Sustained release topical formulation and process for preparation thereof

Abstract

The present invention relates to a sustained release formulations of therapeutic molecules for topical application of such therapeutic molecules for various medical applications Specifically, the invention relates to a novel topical spray formulation applied on the skin for their sustained release where the formulation adheres to the skin yet remains invisible. The formulations may be used to treat various disorders and deliver therapeutic molecules.

Description

[0001] SUSTAINED RELEASE TOPICAL FORMULATION AND PROCESS FOR PREPARATION THEREOF

[0002] TECHNICAL FIELD

[0003] The present invention relates generally to the field of drug delivery systems for sustained release of therapeutic molecules, including methods and formulations for topical management by sustained delivery of therapeutic agents.

[0004] BACKGROUND OF THE INVENTION

[0005] When compared to giant killer diseases like cancer, heart diseases, and diabetes; pain is referred as a “silent epidemic” that does not kill the patient but surely hampers day-to-day activities and also lowers the quality of life. In India, the prevalence of pain has increased in the last few years where the majority of the rural population does not have direct access to therapies to alleviate acute or chronic pain. To treat acute and chronic pain, Indian healthcare system is facing many challenges like lack of awareness of pain management strategies, underreporting, financial barriers, and lower patient compliance for the treatment. Current strategies of pain management include use of either opioids or non-steroidal anti-inflammatory drugs. When a patient is prescribed to take opioids, a smaller number of patients follow the treatment with constancy as opioids have imposed fear of addiction / dependency upon usage. A telephonic survey including 5000 patients reported that the majority of people (68%) prefer over-the-counter (OTC) drugs among which 95% of people use non-steroidal anti-inflammatory drugs (NSAIDs).

[0006] The most common type of formulation used by masses is balm, spray, cream, patches, or ointment; among which the most common active pharmaceutical ingredient (API) is Diclofenac. On the other hand, issue with existing oral formulations of diclofenac is delivering a sub-therapeutic dosage to the site of action and producing toxicity to different organs. For a localized delivery of Diclofenac, a transdermal patch is also used to relieve pain. But this also has disadvantages like irritation, redness, discomfort, and lower aesthetic compliance and it is not cost-effective.

[0007] There has been an increasing focus on development of new routes of drug administration to provide tailored treatments for patients, without decreasing efficacy of drugs, in proportion to the progression of the knowledge of pain mechanisms. Topical drug delivery offers a potential advantage of achieving therapeutic concentrations locally with minimal systemic absorption, thereby reducing systemicadverse effects. It is known that reduction of treatment complexity and pill burden are good strategies to increase patient compliance. Topical delivery of drug molecules is useful in treating acute and chronic pain caused by a wide range of conditions, from musculoskeletal (MSK) pain to neuropathic pain syndromes. These agents are available in a variety of formulations, including creams, ointments, gels, lotions, and patches. However, all these formulations can reduce pain for a very short time (3 to 6 hours), requiring several times of application.

[0008] Many delivery systems for the topical application of pharmaceutical compounds are currently available which include lotions, creams, gels, ointments, transdermal patches and sprays. In almost all applications for pain management, for delivery of local anesthetic, and active molecules such as steroids, hormone, antibiotics, etc. to systemic circulation, there is a need for sustained delivery or maintain drug concentration locally or in blood-plasma above the therapeutic concentration for as longer as from 1 hour to 24 hours for better therapeutic effect, and patient compliance or comfort. However, conventional topical spray formulations tend to remain at the application site for only a short period of time. For example, they are easily rubbed off. As a result, the active agent available for absorption through the skin is only transient.

[0009] Many of these systems suffer from occlusion problems and may cause skin irritation. For example, many compounds, including hormonal drugs, are conventionally delivered using a transdermal patch. These patches comprise an occlusive backing membrane which often results in local skin irritation. A further disadvantage of transdermal patches is that percutaneous penetration of the drug is often poor. The problem of skin irritation associated with transdermal patches is not as pronounced when topical spray formulations are used.

[0010] GB 1,372,721 discloses a container of antiseptic for the topical treatment of burns and scalds, containing a topically acceptable antiseptic active agent against Pseudomonas aeruginosa, a pressuring agent and at least one surfactant admixed with water. The container comprises an outlet, and valve means operable to allow discharge of the contents of the container through the outlet in the form of a foam which is effective in the control of Pseudomonas aeruginosa at the site of a burn or scald.

[0011] US 4,534,958 discloses a sprayable aerosol foam treatment composition which is a liquid in the aerosol container and forms a gel upon application to the skin. The composition comprises water, propellant, volatile solvent, a polyoxyethylene copolymer whose function is not described, and optionally a burn treatment agent and one or more adjuvants. The composition is used “for treating living skin”.Further, topical films that incorporate therapeutic agents have been developed for a variety of purposes in the pharmaceutical arts. For example, US 5632727 and US 5792469 disclose preparation of a biodegradable film dressing with or without additional therapeutic agents formed from a liquid composition of at least one biodegradable / bioerodible thermoplastic polymer in a pharmaceutically acceptable solvent. The film is formed by dispensing, preferably by spraying, the liquid composition onto a tissue site and contacting the liquid composition with an aqueous -based fluid to coagulate or solidify the film onto the human or animal tissue. The biodegradable film can be used to protect and to promote healing of injured tissue and / or to deliver biologically active agents.

[0012] US 6,958,154 discloses a spray-on bandage and drug delivery system. Therein, a fluid composition, e.g., an aerosol spray, is applied onto a surface as a fluid, but then dries in situ to form a patch having a tack- free outer surface covering an underlying adhesive that helps to adhere the patch to the substrate. US 6,899,897 discloses use of a natural gum resin as a carrier for topical application of an active agent. The biological dressing is comprised of a gum resin, a topically acceptable volatile solvent, and a pharmacologically active agent. The gum resin is present in a suitable amount that the composition, when the solvent evaporates, will dry to form a solid coating that sticks to the skin or mucosal membrane to which the composition is applied and maintain the pharmacologically active agent over a sustained period of time in contact with sites on the skin or mucosal membranes exhibiting symptoms of a disease to be treated.

[0013] US 2007 / 0219171 describes transdermal pharmaceutical spray formulations which contain a pharmaceutically active agent, a VP / VA copolymer, and a non-aqueous vehicle. The formulations further comprise an anti-nucleating agent to prevent recrystallization of the pharmaceutically active agent and a penetration enhancer to increase the rate of drug delivery through the skin. Upon application to the skin, the formulations dry to provide a film at the site of treatment.

[0014] However, conventional topical spray formulations tend to remain at the application site for only a short time and as a result, the active agent absorbed through the skin is only available transiently. Further, known topical patch may cause skin irritation or occlusion problems.

[0015] Nanotechnology based formulation has high potential to overcome the challenges of sustained release of drugs, drug penetration and finally long-lasting therapeutic effect such as pain relieve etc. Researchers have been working to develop nanoformulations of nonsteroidal anti-inflammatory drugs (NSAIDs), anaesthetics, capsaicin, alpha-adrenoreceptor antagonists, and cannabinoids, among others,using liposomes, lipids, and biodegradable polymers. However, such nano-formulation based topical products are yet to be available for clinical use.

[0016] Thus, there is a need in the art for a novel nano-formulation for topical application which results in sustained delivery of therapeutic molecules and thus exerts a therapeutic effect for up to 24 hours with just one application of a predetermined dose.

[0017] OBJECTIVE OF THE INVENTION

[0018] An objective of the present invention is to provide a novel sustained release formulation for providing an appropriate therapeutic outcome, such as pain relief, to mammals, including humans. Another objective of the present invention is to provide a novel sustained release formulation comprising a therapeutic drug / a nonsteroidal anti-inflammatory drug (NSAID) / an anesthetic / another active agent alone or in combination for treatment of acute or chronic pain, nociceptive and neuropathic pain. Yet another objective of the present invention is to provide a novel sustained release formulation comprising nonsteroidal anti-inflammatory drugs (NSAIDs) / anesthetics / other active molecules for topical application at the site of pain for treatment of acute or chronic pain, nociceptive and neuropathic pain.

[0019] Still another objective of the present invention is to provide a method for providing pain relief in mammals by applying the sustained release formulation for musculoskeletal pain, osteoarthritis pain, pre-and post-operative pain, cancer pain, pain associated with neurotransmitter dysregulation syndromes and orthopaedic disorders, and / or localised severe or intractable pain.

[0020] Yet another objective of the present invention is to provide a novel sustained-release formulation comprising bioactive molecules, such as anaesthetics, antibiotics, and active molecules, for topical application to achieve an appropriate therapeutic outcome.

[0021] Another objective of the present invention is to provide a novel sustained release formulation once applied on skin surface, the formulation provides sustained release up to 24 hours of active molecules. Another objective of the present invention is to provide a novel sustained release formulation using simple process steps and maximum encapsulation of therapeutic molecules and maintains sustained release up to 24 hours of active molecules.

[0022] Another objective of the present invention is to provide a novel sustained release formulation which forms an invisible non-sticky coating once applied on skin surface and maintains sustained release up to 24 hours of active molecules.Another objective of the present invention is to provide a novel sustained-release formulation for an appropriate therapeutic outcome, such as pain relief, to mammals, including humans.

[0023] These and other objects and advantages of the present subject matter will be apparent to a person skilled in the art after consideration of the following detailed description taking into consideration accompanying drawings in which preferred embodiments of the present subject matter are illustrated.

[0024] SUMMARY OF THE INVENTION

[0025] An aspect of the present invention provides a sustained release formulation comprising:

[0026] an acrylic polymer nanocarrier in an amount in the range of 0.01 to 20 w / w %; an ion-pairing agent in an amount in the range of 0.01 to 20 w / w %;

[0027] at least one therapeutic agent in an amount in the range of 0.01 to 20 w / w %;

[0028] at least one solvent in an amount in the range of 0 to 99 % w / w; and

[0029] a pH-adjusting agent in an amount sufficient to adjust the pH of the formulation to a range of 4 to 8

[0030] Another aspect of the present invention provides A process for preparing a sustained release spray formulation comprising:

[0031] a. dissolving an acrylic polymer nanocarrier in a first solvent to obtain a polymer solution;

[0032] b. adjusting the pH by a range of 4 to 8 of the polymer solution by adding a pH-adjusting agent, thereby obtaining a gel;

[0033] c. adding at least one therapeutic agent to the gel and stirring for 15-20 minutes to obtain a first homogenous mixture;

[0034] d. adding an ion-pairing agent to the first homogenous mixture and stirring for 15-20 minutes to obtain a second homogeneous mixture;

[0035] e. adding a second solvent to the second homogeneous mixture and mixing to obtain the sustained release formulation

[0036] Another aspect of the present invention provides a process for preparing a sustained release gel formulation comprising:

[0037] a. dissolving an acrylic polymer nanocarrier along with propylene glycol and glycerin in a first solvent to obtain a polymer solution;b. adding at least one therapeutic agent into a mixture of the first solvent and a second solvent to obtain a therapeutic solution;

[0038] c. dissolving an ion-pairing agent in a mixture of first solvent and second solvent in a separate vessel to obtain an ion-pairing agent solution

[0039] d. Adding at least one drug to ion-pairing agent or vice versa to make drug-ion-pairing complex mixture and stirring for about 15 to 30 min

[0040] e. slowly adding the drug-ion-pairing complex mixture into the polymer solution with stirring for 15 minutes, followed by additional stirring to obtain a uniform solution f. Addition of the remaining first solvent along with excipients to make upto a specific batch size

[0041] g. adjusting the pH by a range of 5 to 7.4 of the polymer solution by adding a pH-adjusting agent, thereby obtaining a final gel formulation

[0042] Still another aspect of the present invention provides a method for providing delivery of therapeutic agents in mammals by administering / applying the sustained release formulation for the treatment of conditions related to acne, alopecia therapy, rosacea, pain management and melasma, wherein a single application of the formulation provides sustained release of the therapeutic agent for a period of up to 24 hours- 48 hours

[0043] The intent of this summary is not to be a comprehensive description of the claimed subject matter, but rather to provide a short overview of some of the subject matter's functionality. Other systems, methods, features and advantages here provided will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages that are included within this description, be within the scope of any claims.

[0044] BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS

[0045] The illustrated embodiments of the subject matter will be best understood by reference to the drawings. The following description is intended only by way of example, and simply illustrates certain selected embodiments of composite and processes that are consistent with the subject matter as claimed herein, wherein:

[0046] Figure 1 illustrates Schematic presentation of an acrylic nanoparticle formulation of a drug with ionpairing molecules, (a) possible interaction between ion-pairing molecules and the drug molecules toform the complex, and the interaction between the drug complex and the acrylic nanocarrier. The preferred functional groups in the drug molecules may include carboxylic acid, phosphate, and sulphate for better interaction with ion-pairing molecules and their association with the acrylic polymer nanoparticles, (b) Schematic presentation of general chemistry to make the acrylic nanoparticles, where the monomer will be polyacrylic acid, with alkyl methacrylate and crosslinker and their emulsion polymerisation method results the acrylic nanoparticles with a hydrophobic matrix to maximize the hydrophobic interaction with ion-pairing molecules.

[0047] Figure 2 illustrates Standard plot of diclofenac generated using HPLC and used to estimate the concentration of diclofenac in the different formulations

[0048] Figure 3 illustrates the release profile of diclofenac from the different formulations using acrylic polymer nanocarrier (a) Aqua SF-2 (Batch Bl); and (b) Novethix L-10 (Batch B2) containing 10% salicylic acid, respectively.

[0049] Figure 4 illustrates the release profile of diclofenac and ibuprofen from different formulations (B79, B82, B84) containing different percentages of methyl salicylate. Figure 3a and 3b represent 10 % methyl salicylate and 0 % methyl salicylate, respectively, in the diclofenac formulation. Figure 3c corresponds to the release profile of ibuprofen from formulation B79. All the formulations show sustained release of the drug for 24 hours or more..

[0050] Figure 5 illustrates the release profile of diclofenac from different formulations with different amino acids, where the amino acid is used as an ion-pairing agent. All formulations show sustained diclofenac release for more than 24 hours.

[0051] Figure 6 illustrates the release profiles of diclofenac from different formulations (B99, B100 and B101) where arginine is used as an ion pairing agent, and their ratios vary with the fixed concentration of diclofenac. The higher ration of amino acid to drug show burst release of drugs. Figure 7 illustrates the release profile of diclofenac from different formulations (B109 to B109) with variable per cent or ratio of cetrimide and drug with a constant amount (ratio) of acrylic nanocarrier using pig ear skin as the membrane. Among the different formulations, the increased ratio of cetrimide: drug results in faster release and a 1: 1 ratio of cetrimide: drug results in sustained release up to 24 hours.

[0052] Figure 8 illustrates the release profiles of diclofenac diethylamine (DDEA) from different formulations of two nanocarriers containing varying percentages of cetrimide and the drug.Figure 9 illustrates the analgesic effect of different sustained-release diclofenac formulations compared to commercial formulations.

[0053] Figure 10 illustrates the release profiles of (a) Ketoprofen, (b) Aceclofenac, and (c) Tolfenamic acid analogues from different formulations showing their sustained release Figure 11 illustrates the release profiles of (a) Fusidic acid, (b) Azelaic acid, (c) Minoxidil sulfate, and (d) Valproic acid from different formulations showing their sustained release

[0054] Figure 12 illustrates In vitro biocompatibility of acrylic (a) nanocarrier, (b) diclofenac (free), (c) diclofenac+ion-pairing agent (cetrimide) and pain killer formulation, using human dermal fibroblast cell line (hDFC). The IC50 value at 24 hours of pain killer formulation follows the IC50 value of cetrimide, which is around 6 µg / ml. The cell morphology and number respective to (d) the nanocarrier (1000 ug / ml), (e) diclofenac (20 ug / ml) and (f) pain killer formulation (3 ug / ml), showing similar cell density and morphology, confirming their biocompatibility.

[0055] Figure 13 illustrates In vitro biocompatibility (viability plot vs. concentration), free ion-pairing molecules (lysine), and their diclofenac painkiller formulation, with their incubation for 24 hours to 72 hours. 24 hours, the cell viability is around 100%, confirming their biocompatibility.

[0056] Figure 14 illustrates SEM images of pig ear skin when spraying the sustained release formulation (Bl) and allowing it to dry, followed by observation under scanning electron microscopy (SEM). It forms an invisible coating on the skin, with particles at the nanometer scale.

[0057] DETAILED DESCRIPTION OF INVENTION

[0058] A detailed description of various exemplary embodiments of the disclosure is described herein. It should be noted that the embodiments are described herein in such detail as to communicate the disclosure. However, the amount of details provided herein is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure.

[0059] The terminology used herein is to describe particular embodiments only and is not intended to be limiting to the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context indicates otherwise. It will be further understood that the terms “comprises” and / or “comprising”, or “includes” and / or “including” or “has” and / or “having”when used in this specification specify the presence of stated features, regions, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and / or groups thereof. The term “gel” is used herein refers to a semi-solid, apparently homogeneous substance that may be elastic and jelly-like (as in gelatin). The gel comprises a three-dimensional polymeric or inorganic matrix within which is dispersed a liquid phase. The matrix of the gel comprises a network of physically or chemical cross-linked polymers that swell but do not dissolve in the presence of a solvent. The gels are generally clear in appearance; however, turbid gels are also contemplated.

[0060] A “topical medication” is a medication that is applied to body surfaces such as the skin or mucous membranes to treat. Topical medications differ from many other types of drugs because mishandling them can lead to certain complications in a patient or administrator of the drug. Suitably the nonaqueous gel compositions described herein are epicutaneous, meaning that they are applied directly to the skin. Topical medications may also be applied to the surface of tissues other than the skin, for example to the surface of a tooth, rectally or vaginally. Suitably the gel composition is topically applied epicutaneously.

[0061] The term “mammal” refers to organisms from the taxonomy class “mammalian,” including but not limited to humans, other primates such as chimpanzees, apes, orangutans and monkeys, rats, mice, cats, dogs, cows, horses, etc. In various embodiments, the mammal is a human patient.

[0062] Treating or treatment of a disease or condition (e.g., pain and / or inflammation) refers to executing a protocol, which may include administering one or more drugs to a patient (human, normal or otherwise, or other mammal), in an effort to alleviate signs or symptoms of the disease. Alleviation can occur prior to signs or symptoms of the disease or condition appearing, as well as after their appearance. Thus, “treating” or “treatment” includes “preventing” or “prevention” of disease or undesirable condition (e.g., pain and / or inflammation). In addition, “treating” or “treatment” does not require complete alleviation of signs or symptoms, does not require a cure, and specifically includes protocols that have only a marginal effect on the patient. “Reducing pain and / or inflammation” includes a decrease in pain and / or inflammation and does not require complete alleviation of pain and / or inflammation signs or symptoms, and does not require a cure. In various embodiments, reducing pain and / or inflammation includes even a marginal decrease in pain and / or inflammation. By way of example, the administration of the effective dosages of the formulation may be used to prevent, treat or relieve the symptoms of pain and / or inflammation for different diseases or conditions.The phrase “pain management medication” includes one or more therapeutic agents that are administered to prevent, alleviate or remove pain entirely. These therapeutic agents include antiinflammatory agents, muscle relaxants, analgesics, anesthetics, narcotics, and so forth, and combinations thereof.

[0063] The terms “effective amount” and “therapeutically effective amount” of an agent as used herein mean a sufficient amount of the agent to provide the desired therapeutic or physiological effect or outcome. This effect is the treatment, alleviation, prevention, diminishment or amelioration of pain or its various symptoms and manifestations. Undesirable effects, e.g. side effects, are sometimes manifested along with the desired therapeutic effect; hence, a practitioner balances the potential benefits against the potential risks in determining what is an appropriate “effective amount”. The exact amount required will vary from subject to subject, depending on the species, age and general condition of the subject, mode of administration and the like. Thus, it may not be possible to specify an exact “effective amount”. However, an appropriate “effective amount” in any individual case may be determined by one of ordinary skill in the art using only routine experimentation.

[0064] A “subject” as used herein refers to an animal, including a mammal such as a human who can benefit from the topical formulations and methods enabled herein. There is no limitation on the type of animal that could benefit from the presently described formulations. A subject regardless of whether a human or non-human animal may be referred to as an individual, patient, animal, host, target or recipient. The formulations and methods described herein have applications in human medicine, veterinary medicine as well as in general, domestic or wild animal husbandry.

[0065] As used herein, the phrase “effective pain management” refers to an objective evaluation of a human patient's response (namely, pain experienced versus side effects) to analgesic treatment by a physician as well as subjective evaluation of therapeutic treatment by the patient undergoing such treatment. As used herein, the phrase “pharmaceutically acceptable salt” refers to those salts in which the anion does not contribute significantly to the toxicity or pharmacological activity of the salt, and, as such, they are the pharmacological equivalent of the base form of the active agent. Examples of pharmaceutically acceptable acids that are useful for the purposes of salt formation include, but are not limited to, hydrochloric, hydrobromic, hydroiodic, sulfuric, citric, tartaric, methanesulfonic, fumaric, malic, maleic and mandelic acids. Pharmaceutically acceptable salts further include mucate, N-oxide, sulfate, acetate, phosphate dibasic, phosphate monobasic, acetate trihydrate, bi(heptafluorobutyrate), bi(methylcarbamate), bi(pentafluoropropionate), bi(pyridine-3-carboxylate), bi(trifluoroacetate),bitartrate, chlorhydrate, and sulfate pentahydrate, benzenesulfonate, benzoate, bicarbonate, bitartrate, bromide, calcium edetate, camsylate, carbonate, chloride, citrate, dihydrochloride, edetate, edisylate, estolate, esylate, fumarate, gluceptate, gluconate, glutamate, glycollylarsanilate, hexylresorcinate, hydrabamine, hydrobromide, hydrochloride, hydroxynaphthoate, iodide, isethionate, lactate, lactobionate, malate, maleate, mandelate, mesylate, methylbromide, methylnitrate, methylsulfate, mucate, napsylate, nitrate, pamoate (embonate), pantothenate, phosphate / diphosphate, polygalacturonate, salicylate, stearate, subacetate, succinate, sulfate, tannate, tartrate, teoclate, triethiodide, benzathine, chloroprocaine, choline, diethanolamine, ethylenediamine, meglumine, and procaine, aluminum, calcium, lithium, magnesium, potassium, sodium propionate, zinc and the like. The phrase “immediate release” is used herein to refer to one or more therapeutic agent(s) that is introduced into the body and that is allowed to dissolve in or become absorbed at the location to which it is administered, with no intention of delaying or prolonging the dissolution or absorption of the drug. Immediate release refers to the release of drug within a short time period following administration, e.g., generally within a few minutes to about 1 hour.

[0066] As used herein, the phrase “sustained release” refers to the release of the drug from the formulation over a period substantially longer than one hour, such as about two hours or longer. Generally, the sustained release of drug from the inventive formulation occurs at such a rate that blood (for example, plasma) concentrations in a patient administered the formulation are sufficient to mitigate pain over a period of time of at least about 12 hours, upto 24 hours or more.

[0067] The phrase “release rate profile” refers to the percentage of active ingredient that is released over fixed units of time, e.g., mcg / hr, mcg / day, mg / hr, mg / day, 10% per day for ten days, etc. As persons of ordinary skill know, a release rate profile may be but need not be linear. By way of a non-limiting example, the formulation may be in a gel patch form that releases at least one analgesic agent over a period of time.

[0068] The present invention is directed towards a sustained release formulation comprising:

[0069] an acrylic polymer nanocarrier in an amount in the range of 0.01 to 20 w / w %; an ion-pairing agent in an amount in the range of 0.01 to 20 w / w %;

[0070] at least one therapeutic agent in an amount in the range of 0.01 to 20 w / w %;

[0071] at least one solvent in an amount in the range of 0 to 99 % w / w; anda pH-adjusting agent in an amount sufficient to adjust the pH of the formulation to a range of 4 to 8.

[0072] In an embodiment of the present invention, there is provided a sustained release formulation comprising:

[0073] an acrylic polymer nanocarrier in an amount in the range of 0.01 to 20 w / w %, preferably 0.1 to 10 % (w / w), preferably 0.5 to 5%, preferably 0.5 to 3 % w / w;

[0074] an ion-pairing agent in an amount in the range of 0.01 to 20 w / w %;

[0075] at least one therapeutic agent in an amount in the range of 0.01 to 20 w / w %;

[0076] at least one solvent in an amount in the range of 0 to 99 % w / w; and

[0077] a pH-adjusting agent in an amount sufficient to adjust the pH of the formulation to a range of 4 to 8.

[0078] In an embodiment of the present invention, there is provided a sustained release formulation wherein the formulation optrionally comprises an excipient.

[0079] In an embodiment of the present invention, there is provided a sustained release formulation, wherein the ratio of acrylic polymer nanocarrier to ion-pairing agent mass is in a range of 0.5:0.05 to 0.5:0.10, preferably 0.5:0.5 to 0.5:5, preferably 0.5:1 to 0.5:3, preferably 0.5:1 to 0.5:3.

[0080] In an embodiment of the present invention, there is provided a sustained release formulation, wherein the ratio of acrylic polymer, ion-pairing agent and drug mass is in a range of 0.5:0.05:0.05 to 0.5: 10:30, preferably 0.5:0.1:0.5 to 0.5:5:10, preferably 0.5:l:l to 0.5:3:3, preferably 0.5:l:l to 0.5:1.5:1.5, preferably 0.5:l:0.1 to 0.5:1.5:1.5, preferably 0.5:l:0.2 to 0.5:1.5:1.5 and preferably 0.5:l:0.5 to 0.5:1.5:1.5.

[0081] In an embodiment of the present invention, there is provided a sustained release formulation, wherein the acrylic polymer nanocarrier is selected from the group consisting of carbomers, acrylates / alkyl acrylate crosspolymers, acrylates copolymers, and polyacrylate crosspolymers, or any commercially available aqueous dispersion thereof,

[0082] In an embodiment of the present invention, there is provided a sustained release formulation, wherein the pH-adjusting agent is any generally used base, such as triethanolamine (TEA) and NaOH etc. In an embodiment of the present invention, there is provided a sustained release formulation, wherein the ion-pairing agent is selected from the group consisting of a quaternary ammonium salt of formulaR-N (CH3)3X, wherein R is a C2-C is alkyl group and X is selected from Cl, Br, or MeSCh, preferably wherein R is C12-C14; tetraalkylammonium salts of formula R4N+X–, wherein R is C4-C18 alkyl; alkylpyridinium salts of formula [R-pyridinium]+X; benzyl-dimethyl-alkyl-ammonium salts of formula [R-N+(CH3)2-CH2Ph] X; quatemized amino-ester compounds having the general formula [R-C(O)O-CH2CH2-N+(CH3)2-CH2CH2-O-C(O)-R] X; cholinium salts of formula [HO-CH2-CH2-N fCHipl X; amino-acid-based quaternary ammonium surfactants of formula R-CO-NH-(CH2)n-N fCHiCR'X or R-CO-NH-(CH2)n-N+(CH3)3X, wherein R is a Cio-Cie fatty chain; quaternary silane compounds; and zwitterionic betaine -type compounds, including but not limited to dodecyltrimethylammonium, tetradecyltrimethylammonium, hexadecyltrimethylammonium, decyltrimethylammonium salts; tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium hydrogen sulfate, tetrabutylammonium phosphate, tetrahexylammonium bromide, tetrahexylammonium chloride; cetylpyridinium chloride, benzalkonium chloride; distearoylethyl dimonium chloride, dipalmitoylethyl hydroxyethylmonium salts, behentrimonium methosulfate; choline chloride and N-alkyl cholinium salts; ethyl lauroyl arginate hydrochloride; lysine-derived surfactants; cocamidopropyl betaine; 3-(trimethoxysilyl)-propyloctadecyl-dimethyl ammonium chloride; glycine betaine, choline, carnitine, butyrobetaine, homarine, and trigonelline. In an embodiment of the present invention, there is provided a sustained release formulation, wherein the ion-pairing agent is selected from the group consisting of cetrimide, arginine, lysine, histidine, and tryptophan.

[0083] In an embodiment of the present invention, there is provided a sustained release formulation, wherein the therapeutic agent comprises a molecule having positive, negative, or zwitterionic character, preferably comprising an anionic functional group selected from -COO, -SO3, or -PO4 or capable of forming a negatively charged species, and wherein the therapeutic agent is selected from the group consisting of a nonsteroidal anti-inflammatory drug, an anesthetic agent, an antibiotic, an analgesic, an antiviral agent, a hormone, an antiaging agent, and other therapeutic agents.

[0084] In an embodiment of the present invention, there is provided a sustained release formulation, wherein the therapeutic agent is selected from the group consisting of ibuprofen, naproxen, ketoprofen, ketorolac, flurbiprofen, indomethacin, salicylic acid, mefenamic acid, zaltoprofen, aceclofenac, diclofenac, fusidic acid, azelaic acid, tranexamic acid, valproic acid, salbutamol sulfate, cromolyn sodium, minoxidil sulfate, methotrexate, clodronic acid, and tolfenamic acid.In an embodiment of the present invention, there is provided a sustained release formulation, wherein the solvent is selected from the group consisting of water, ethanol, isopropyl alcohol, acetone, n-butanol, methylene chloride, and methylene dimethyl ether, or a mixture thereof.

[0085] In an embodiment of the present invention, there is provided a sustained release formulation, wherein the formulation further comprises a preservative, a stabilizer, a surfactant, a buffering agent and an antioxidant.

[0086] In an embodiment of the present invention, there is provided a sustained release formulation, wherein the formulation is in form of cream, gel, ointment, patch, and topical spray.

[0087] Another embodiment of the present invention provides A process for preparing a sustained release spray formulation comprising:

[0088] a. dissolving an acrylic polymer nanocarrier in a first solvent to obtain a polymer solution;

[0089] b. adjusting the pH by a range of 4 to 8 of the polymer solution by adding a pH-adjusting agent, thereby obtaining a gel;

[0090] c. adding at least one therapeutic agent to the gel and stirring for 15-20 minutes to obtain a first homogenous mixture;

[0091] d. adding an ion-pairing agent to the first homogenous mixture and stirring for 15-20 minutes to obtain a second homogeneous mixture;

[0092] e. adding a second solvent to the second homogeneous mixture and mixing to obtain the sustained release formulation.

[0093] Another embodiment of the present invention provides a process for preparing a sustained release gel formulation comprising:

[0094] a. dissolving an acrylic polymer nanocarrier along with propylene glycol and glycerin in a first solvent to obtain a polymer solution;

[0095] b. adding at least one therapeutic agent into a mixture of the first solvent and a second solvent to obtain a therapeutic solution;

[0096] c. dissolving an ion-pairing agent in a mixture of first solvent and second solvent in a separate vessel to obtain an ion-pairing agent solution

[0097] d. Adding at least one drug to ion-pairing agent or vice versa to make drug-ion-pairing complex mixture and stirring for about 15 to 30 mine. slowly adding the drug-ion-pairing complex mixture into the polymer solution with stirring for 15 minutes, followed by additional stirring to obtain a uniform solution f. Addition of the remaining first solvent along with excipients to make upto a specific batch size

[0098] g. adjusting the pH by a range of 5 to 7.4 of the polymer solution by adding a pH-adjusting agent, thereby obtaining a final gel formulation

[0099] In an embodiment of the present invention, there is provided a process for preparing a sustained release formulation, wherein the first solvent and second solvent are each independently selected from the group consisting of water, ethanol, isopropyl alcohol, acetone, n-butanol, methylene chloride, and methylene dimethyl ether, or a mixture thereof, wherein the pH-adjusting agent is triethanolamine. In an embodiment of the present invention, there is provided a process for preparing a sustained release formulation, wherein the process optionally comprises adding a preservative, a stabilizer, a surfactant, a buffering agent and an antioxidant after step (d) and before step (e).

[0100] In an embodiment of the present invention, there is provided a process for preparing a sustained release formulation, wherein the therapeutic agent comprises a molecule having positive, negative, or zwitterionic character, preferably comprising an anionic functional group selected from -COO, –SO3–, or –PO4–or capable of forming a negatively charged species, and wherein the therapeutic agent is selected from the group consisting of a nonsteroidal anti-inflammatory drug, an anesthetic agent, an antibiotic, an analgesic, an antiviral agent, a hormone, an antiaging agent, ibuprofen, naproxen, ketoprofen, ketorolac, flurbiprofen, indomethacin, salicylic acid, mefenamic acid, zaltoprofen, aceclofenac, diclofenac, fusidic acid, azelaic acid, tranexamic acid, valproic acid, salbutamol sulfate, cromolyn sodium, minoxidil sulfate, methotrexate, clodronic acid, and tolfenamic acid.

[0101] Another embodiment of the present invention provides a method for providing delivery of bioactive molecules in mammals by administering / applying the sustained release formulation for the treatment of conditions related to acne, alopecia therapy, rosacea and melasma.

[0102] In yet another embodiment of the present invention there is provided a sustained release formulation, wherein the solvent is water.

[0103] In still another embodiment of the present invention there is provided a sustained release formulation, wherein the solvent is ethanol.In an embodiment of the present invention there is provided a sustained release formulation, wherein the solvent is a mixture of water and ethanol in the ratio of 30:70 by volume.

[0104] In still another embodiment of the present invention there is provided a sustained release formulation, wherein the formulation is in form of cream, gel, ointment, patch, and topical spray.

[0105] In still another embodiment of the present invention there is provided a sustained release formulation, wherein the formulation forms an invisible non-sticky coating once applied on skin surface and maintains sustained release up to 24- 48 hours of the therapeutic agent.

[0106] In an embodiment there is provided a method for providing delivery of therapeutic agents in mammals by administering / applying the sustained release formulation for the treatment of conditions related to acne, alopecia therapy, rosacea, pain management and melasma, wherein a single application of the formulation provides sustained release of the therapeutic agent for a period of up to 24 hours- 48 hours

[0107] The present invention is directed towards a sustained release formulation comprising an acrylic polymer nanocarrier, an ion-pairing agent, a therapeutic drug / a nonsteroidal anti-inflammatory drug (NSAID) / an anesthetic / another active agent alone or in combination, and at least one solvent or two or more solvents. This sustained release formulation can be applied directly on skin surface as a cream or an ointment of via utilization of a spray device (mechanical pump).

[0108] In an embodiment of the present invention there is provided a sustained release formulation, wherein the acrylic polymer nanocarrier are polymers with carboxylic functional groups, preferably crosslinked or un-crosslinked acrylic polymers, more preferably pre-crosslinked suspension form of carbomer or acrylic-polymer-particles. Polymers with carboxylic functional group such as pre-crosslinked suspension form of carbomer or acrylic-polymer-particles or crosslinked polyacrylic polymers are present in an amount in the range of 0.01 to 40 % by weight.

[0109] In an embodiment of the present invention there is provided a sustained release formulation, wherein the protonated amine compound, preferably from quaternary ammonium compound (QAC) act as ionpairing agents to interact with both acrylic polymer nanocarrier and active molecule / drug through ionic interaction or / and hydrophobic interaction with drug or acrylic polymer nanocarrier, to make carrierdrug gel complex and help in loading the drug with the carrier molecule, which are released in a sustained manner after topical application. The QAC also acts as an active molecule penetrator enhancer. These ion-pairing agents are present in an amount in the range of 0.01 to 20 % by weight.In an embodiment of the present invention there is provided a sustained release formulation, wherein the acrylic polymer nanocarrier are hydrophobically modified acrylic copolymers with Generic compositions, (Meth) acrylic acid + alkyl methacrylate + crosslinker, with typical structure: CH2=CH-COOH + CH2=C(CH3)-COOR+ Crosslinker, or combination of similar monomers more than two (where R= alkyl group 1 to 20) such copolymers are widely used in aqueous sprayable systems best interaction with ion-pair: as carboxyl groups ionic interaction, Alkyl chains ion-pair partitioning. In an embodiment, there is provided a process for preparing a sustained release formulation wherein the first solvent and second solvent are each independently selected from the group consisting of water, ethanol, isopropyl alcohol, acetone, n-butanol, methylene chloride, and methylene dimethyl ether, or a mixture thereof,

[0110] wherein the pH-adjusting agent base, such as triethanolamine, NaOH etc,

[0111] wherein the process optionally comprises adding a preservative, a stabilizer, a surfactant, a buffering agent and an antioxidant after step (d) and before step (e),

[0112] wherein the excipient is selected from a group consisting ofas propylene glycol, glycerol, polyethylene glycol.

[0113] In certain embodiments, the sustained release formulation of the present invention is useful for the topical treatment and management of a broad range of conditions including, but not limited to, acute and chronic pain, musculoskeletal pain, osteoarthritis pain, neuropathic pain, nociceptive pain, preoperative and post-operative pain, cancer pain, pain associated with neurotransmitter dysregulation syndromes, and orthopedic disorders. The formulation may further be used for localized severe or intractable pain. Additionally, the sustained release formulation finds utility in dermatological conditions including acne, alopecia, rosacea, and melasma. The formulation may also be used for the delivery of bioactive molecules including vitamins, antibiotics, antiviral agents, hormones, and antiaging agents for the treatment of conditions associated therewith. The method of treatment comprises administering or applying a therapeutically effective amount of the sustained release formulation to the skin of a mammal, including a human, in need thereof.

[0114] The present invention relates to a sustained release formulation for transdermal delivery of a drug comprising an acrylic polymer nanocarrier, an ion-pairing agent, a therapeutic agent, and at least one or more solvents. The formulation may contain additional excipients. The important aspects of the invention are:Acrylic polymer nanocarrier: These polymer nanocarriers carry multiple negative charges, preferentially from the carboxylic functional group, such as polyacrylic polymer in the form of long carbon chain molecules or in nanoparticle forms. Nanocarriers interact with ion-paring molecules or drug molecule through ionic or hydrophobic interaction or both interactions, preferentially with hydrophobic interaction with ion-pairing molecules. In certain embodiments, pre-crosslinked polyacrylic polymer nanocarriers are synthesized or are in pre-crosslinked suspension form of a carbomer, selected from the group though not limited to Carbopol Aqua SF-1, Carbopol Aqua SF-2, Carbopol Aqua SF-1 OS, Novethix L-10, Noverite, Carbopol Aqua 30, Novemer EC-1, and Novemer EC-2, AQUAPOL® SF Series such as AQUAPOL® SF-1, AQUAPOL® SF-2, AQUAPOL® SF-22, AQUAPOL® Carbomer Series such as AQUAPOL® 934, AQUAPOL® 940, EUDRAGIT® NE 30 D, EUDRAGIT® NM 30 D, EUDRAGIT® RS 30 D, Volarest™ FL, HYGEL LV30 / LV40 or any commercially available crosslinked acrylic polymer suspension.

[0115] In certain preferred embodiments, the hydrophobic polymer comprises acrylic polymers or copolymers, methacrylic polymers and copolymers, including ethoxyethyl methacrylates, cynaoethyl methacrylate, poly(acrylic acid), poly(methacrylic acid), methacrylic acid alkylamide copolymer, poly(methyl methacrylate), polymethacrylate, poly(methyl methacrylate) copolymer, polyacrylamide, aminoalkyl methacrylate copolymer, poly(methacrylic acid anhydride), and glycidyl methacrylate copolymers. In certain embodiments, the acrylic polymer comprises one or more ammonia methacrylate copolymers. Ammonia methacrylate copolymers are well known as fully polymerized copolymers of acrylic and methacrylic acid esters with a low content of quaternary ammonium groups. Preferred film-formers include copolymer of methyl methacrylate and butyl methacrylate (Plastoid B®), a copolymer of dimethylamine ethyl methacrylate and a neutral methacrylic acid ester (Eudragit El 00®), ammonio methacrylate copolymer type B (Eudragit RS®), ammonio methacrylate copolymer type A (Eudragit RL®), methacrylic acid copolymer type A (Eudragit L100®), methacrylic acid copolymer type B (Eudragit SI 00®), and the like. Suitable hydrophobic acrylic polymers include acrylate copolymers, methacrylic polymers and copolymers, acrylate / oc-tylacrylamide copolymer, methacrylic polymer, AMP-acrylates copolymer, Poly(butyl methacrylate, (2-dimethylaminoethyl)methacrylate, methyl methacrylate) 1:2:1, Poly(ethyl acrylate, methyl methacrylate) 2:1, Poly(ethyl acrylate, (2-trimethylaminoethyl)methacrylate, methyl methacrylate) l:0.2:2 chloride, Poly(methacrylic acid, methyl methacrylate).

[0116] Ion-pairing agent: Ion-pairing agents have positive charges at the respective formulation pH (4 to 8), having primary amine group, secondary amine group, and tertiary amine groups. Preferentially, the ion-pairing agents are a quaternary ammonium salt with following general formula: Generic motif: R-N+(CH3)3X- (R = C2-C18 alkyl; X = C17Br7MeSO4), preferentially C12 to C14, Dodecyltrimethylammonium, Tetradecyltrimethylammonium, Hexadecyltrimethylammonium, Decyltrimethylammonium; Tetraalkylammonium salts: Generic motif: R4N+X (R = C4-C18 alkyl) such as Tetrabutylammonium bromide / chloride, Tetrabutylammonium hydrogen sulfate,, Tetrabutylammonium phosphate, Tetrahexylammonium bromide / chloride; Alkylpyridinium: [R-Py+] X such as Benzyl-dimethyl-alkyl-ammonium: [R-N+(CH3)2-CH2Ph] X (mixtures common), Cetylpyridinium chloride (CPC) - |C 16-pyridinium|CI. Benzalkonium chloride (BAC) - mixture of C12 / C14 / C16 benzyl dimethyl ammonium chlorides; Quaternized amino-ester with 1-2 fatty chains with general formula [R-C(O)O-CH2CH2-N+(CH3)2-CH2CH2-O-C(O)-R] X (dialkyl esterquat motifs; structures vary) such as Distearoylethyl dimonium chloride (DEEDM AC -type), Dipalmitoylethyl hydroxyethylmonium salts (esterquat class), Behentrimonium methosulfate (C22 with MeSCh ): Cholinium with general formula [HO-CH2-CH2-N+(CH3)3] such as Choline chloride (cholinium chloride), N-alkyl-cholinium salts, Alkylpyridinium with Generic cation: [R-(pyridinium)+] X such as Cetylpyridinium chloride (CPC), Benzyl dimethyl alkyl ammonium, Generic cation: [R-N+(CH3)2-CELPh] X. Amino- acid-based quaternary ammonium surfactants, General structure: R-CO-NH-(CH_2 )_n-NA+ (CH_3 )_2 RA’ XA- or R-CO-NH-(CH_2 )_n-NA+ (CH_3 )_3 XA- Where: R = fatty chain (C10-C16) and amino acid backbone = Lys, Arg, His, etc.; Ethyl Lauroyl Arginate HC1 (LAE) ( Vedeqsa®, Mirenat-G®, Aminat-G®); Lysine-derived surfactant (Gemini type) such as AMISAFE® LL-DS-22; Cocamidopropyl betaine (CAPB) such as Dehyton® PK45 (BASF) Amphosol® CG (Stepan); Quaternary Silane Compound such as 3-(trimethoxysilyl)-propyloctadecyl-dimethyl ammonium chloride etc. Other examples of ion-pairing agents include glycine betaine, choline, carnitine, butyrobetaine, homarine, and trigonelline etc.

[0117] Drug / Therapeutic agents: The therapeutic agents or drug molecules are positive, negative, or zwitter ionic, preferably with anionic groups (-COO. -SO3", -PO4") or form negatively charged species including but not limited to local anesthetic agents, anti-inflammatory agents (Ibuprofen, Naproxen, Ketoprofen, Ketorolac, Flurbiprofen, Indomethacin, Salicylic acid, Mefenamic acid, Zaltoprofen, Aceclofenac), analgesic (Diclofenac, Naproxen, Flurbiprofen, Indomethacin, Salicylic acid, Mefenamic acid, Zaltoprofen, Aceclofenac), antibiotic molecules,, antiviral agent, hormone, antiaging agent, and other therapeutic molecules such as fusidic acid Azelaic acid Tranexamic acid Valproic acid, Salbutamol sulfate, Cromolyn sodium, Minoxidil sulfate, Methotrexate, Clodronic acid, Tolfenamic acid etc.Solvent: The solvent for the topical spray formulation includes volatile solvents or mixture of water and a different volatile solvent such as ethanol, isopropyl alcohol, acetone, n-butanol, methylene chloride, methylene dimethyl ether, or a hydroalcoholic system or in combination of two or more solvents. The volatile solvent concentration in the topical spray formulation is between 1 % to 99% of the formulation. Preferably, the solvent is a hydroalcoholic solvent with the volatile solvent percentage 30 to 95%.

[0118] Optional agents: In addition to the drug / therapeutic agents, the polymeric film forming topical spray formulation may additionally include physiologically acceptable components such as sodium chloride and like materials conventionally used to achieve isotonicity with typical body fluids, pH buffers to establish a physiologically compatible pH range and to enhance the solubility of the anesthetic present, vasoconstrictors such as epinephrine, preservatives, stabilizers and antioxidants and the like.

[0119] In certain other embodiments, an additional surfactant (co-surfactant) and / or buffering agent can preferably be combined with the formulation so that the surfactant and / or buffering agent maintains the product at an optimal pH for stability. The surfactant and / or buffering agent may also prevent the initial stinging or burning discomfort associated with administration of the drug on the skin (e.g, local anesthetic).

[0120] In certain other embodiments, an additional anti-oxidant and / or stabilizing agent can preferably be combined with one or more of the pharmaceutically acceptable vehicles previously described herein so that the anti-oxidant and / or stabilizing agent maintains the drug product at an optimal impurity level for stability. The anti-oxidant and / or stabilizing agent also prevents the initial degradation of active agent during the manufacturing process. The anti-oxidant may be selected, e.g., from ascorbic acid, EDTA, trolamine, tocopherol, propyl galate, sodium sulfite and mixtures of any of the foregoing. The formulation of the present invention may contain preservatives to prevent microbial growth. Suitable preservatives for use in the present invention include, but not limited to benzoic acid, boric acid, p-hydroxybenzoates, phenols, chlorinated phenolic compounds, alcohols, quarternary compounds, mercurials, mixtures of the foregoing and the like.

[0121] The composition may further comprise one or more additional components selected from the group consisting of solubilizers, plasticizers, and water-soluble additives. Preferred plasticizers include triethyl citrate, dimethyl isosorbide, acetyltributyl citrate, castor oil, propylene glycol, and polyethylene glycol, or any two or more of the above in combination.In the formulation of the present invention, ions-pair interaction is used to load the therapeutic molecules, positive, negative and z witter ionic preferably negative; acrylic polymer nanocarrier with preferentially negatively charged with or without amine (primary, secondary and tertiary) and ionpairing agent in a volatile solvent. The acrylic polymer nanocarrier acts as a depot of the therapeutic molecule and sticks to the surface of the skin. With change in pH of the skin, the therapeutic molecules are slowly released and penetrate the skin in the applied area where ion pairing molecules may enhance the skin permeability of drug molecules.

[0122] The formulation of the present invention can be applied through topical spray, ointment, gel or cream. However, the preferred method of application is meter dose spray. The acrylic polymer nanocarrier makes a non-sticky (compared to messy conventional ointment or cream) invisible, breathable coating on the skin which is not even felt after fast drying of formulation. The coated formulation on the skin release the drug up to 24 hours or up to 48 hours.

[0123] EXAMPLES

[0124] Following examples are given by way of illustration, therefore, should not be construed to limit the scope of the invention.

[0125] Example 1:

[0126] Measurement of particle size and Zeta potential formulation:

[0127] The acrylic nanoparticles were obtained from the respective company. To measure particle size and zeta potential, 20 pl of the nanocarrier was added to 1-2 ml of PBS and analysed in a DLS (dynamic light scattering) Malvern Zetasizer Nano ZS instrument. Table 1 shows the physicochemical properties of different commercially available acrylic polymer nanocarriers, including particle size, zeta potential, and pH before drug loading.

[0128] Table 1

[0129] Name Size (nm) Zeta (mv) PH Carbopol Aqua SF-2 70.8 -37.7 2.98 Novethix L-10 84.2 -44.4 2.85 Novemer EC- 1 97.1 -73.0 6.4

[0130]

[0131] AQUAPOL® SF-1, 100 -40 3AQUAPOL® 940, 98 -59 2.9 HYGEL LV30 101 -50 3.2 EUDRAGIT® NE 30 D 102 -49 5 Novemer EC-2 -62.4 6.7

[0132]

[0133] 110.8

[0134] The physicochemical properties of different commercially available acrylic polymer suspensions, as obtained, vary between 70 nm and 120 nm, and zeta potential varies between -30 mV and -80 mV, depending on the solution pH. These particles were observed to be stable with low' value (<0.1) polydispersity index.

[0135] EXAMPLE 2

[0136] Preparation of diclofenac loaded formulation using different acrylic polymer nanocarrier All different formulations in 100 ml batch were prepared by taking 0.5 to 1 % (0.5 g to 1 g) of different acrylic polymer nanocarrier [as mentioned in table 1] in 10 to 20 ml water. Then, pH was adjusted to 6-7 by adding 20% TEA (Triethanolamine). 0.5 to 3 % (0.5 g to 1 g) of drug (diclofenac sodium) was added and stirred for 15 minutes to obtain a homogenous mixture of drug. Once the homogenous mixture was formed, 0.25% to 3 % (0.25 gm to 3 g) of cetrimide (ion pairing agent) was added into the drug- acrylic polymer nanocarrier mixture and stirred for 15 minutes. Once mixture was homogeneously mixed, 0 to 10% of methyl salicylate was added into the mixture and stirred for another 15 minutes. The volume was made up with ethanol to obtain ratios of 40:60 to 30:70 (water:ethanol). The prepared formulation was stored for further studies. Table 1 provides the details of the various formulations prepared.

[0137] Table 2Batch Acrylic Nanocarrier Cetrimide Diclofenac Methyl Ethanol Particle polymer (g) (g) (g) Salicylate ml size nanocarrier (g) (nm) Bl Aqua SF-2 0.5 0.5 0.5 0 70 172.2 B2 Novethix L- 0.5 0.5 0.5 0 70 169.2

[0138] 10

[0139] B3 Novemer EC- 0.5 0.5 1 0 70 166.2

[0140] 1

[0141] B4 Novemer EC- 0.5 0.5 1.5 0 70 180.3

[0142] 2

[0143] B5 AQUAPOL® 0.5 1 0.5 10 60 193.3

[0144] 934,

[0145] B6 AQUAPOL® 0.5 1 0.5 10 60 192.3

[0146] 940,

[0147] B7 EUDRAGIT® 0.5 1 0.5 0 60 170.2 NE 30 D,

[0148] B8 EUDRAGIT® 0.5 2 1.5 0 60 171.12 NM 30 D,

[0149] B9 EUDRAGIT® 0.5 2 1.5 10 60 180.12

[0150] RS 30 D

[0151] BIO Volar est™ FL 0.5 2 1.5 10 70 193.12 Bll HYGEL 0.5 2 1.5 0 70 180.1

[0152] LV30

[0153] B12 HYGEL 0.5 2 2.5 0 70 200.12

[0154] LV40

[0155] B13 AQUAPOL® 0.5 2 2.5 5 60 204.12

[0156] SF-1,

[0157] B14 AQUAPOL® 0.5 2 2.5 5 70 202.11

[0158] SF-2,

[0159] B15 AQUAPOL® 1 3 3 5 60 198.23

[0160] SF-22

[0161] B16 Carbopol 1 3 3 10 60 210.12

[0162] Aqua 30,

[0163] B17 Aqua SF-1 0.5 2 3 10 70 211.23 B18 Aqua SF-2 0.5 0.50 1 0 70 183.1 B19 Aqua SF-2 0.5 1 2 10 70 183.1 B20 Aqua SF-2 1 2 2 0 70 191.2

[0164]

[0165] B21 Aqua SF-2 1 3 3.5 0 70 210.12Above formulation with different commercially available acrylic polymer nanoparticles (see the trade name in table 2) with their particle size around 70 to 100 nm and charges — 30 to -40 mV depending on the pH of the solution were used for the diclofenac formulation development. The amount of ion pairing agent 0.5 % to 3 % (w / w) and diclofenac 0.5 % to 3 % (w / w) were varied from with variable carrier concentration 0.5 % to 1 % (w / w) of drug result stable formulations with their average particles size ranging from 166 to 210 nm depending on the amount of the ion paring molecules and drug as well as their relative amount with nanocarrier. Moreover it is important to note that the overall charges of the resultant ion pairing molecule-i- drug complex loaded into the particles do not change much of the charge of drug loaded nanocarrier. This is due to interaction between particles and the drug complex are through the hydrophobic interaction of alkyl chain of ionpar molecules and not through the ionic interaction between ion paring agent and the negatively charged acrylic nanoparticles.

[0166] EXAMPLE: 3

[0167] Preparation of formulation using various ion pairing agents and their physicochemical properties

[0168] All different formulations in 100 ml batch were prepared by taking 0.5 (0.5 g) of Novethix L-10 acrylic polymer nanocarrier [as mentioned in table 1] in 10 to 20 ml water. Then, pH was adjusted to 6-7 by adding 20% TEA (Triethanolamine). 1% (1 g) of drug (diclofenac sodium) was added and stirred for 15 minutes to obtain a homogenous mixture of drug. Once the homogenous mixture was formed, 1 % ( 1 g) of cetrimide (ion pairing agent) was added into the drug- acrylic polymer nanocarrier mixture and stirred for 15 minutes. Once the mixture was homogeneously mixed, 0 to 10 % of methyl salicylate was added to the mixture and stirred for another 15 minutes. The volume was made up with ethanol to obtain a ratio of 30:70 (water: ethanol). The prepared formulation was stored for further studies. Table 3 provides the details of the various formulations prepared.

[0169] Table 3

[0170] Batch Acrylic lonpairing lonpairing Diclofen Ethanol Particle Zeta polymer molecules molecules ac (ml) Size Potential nanocarrier (g) (g) (nm) (mV) B22 Novethix L- Tetrabutylammoni 0.5 1 70 169 -30.22

[0171]

[0172] 10 um chloride,B23 Novethix L- Tetrabutylammoni 0.5 1 70 170 -29.44 10 um hydrogen

[0173] sulfate

[0174] B24 Novethix L- Cetylpyridinium 0.5 1 70 195 -33.14

[0175] 10 chloride

[0176] B25 Novethix L- Distearoylethyl 0.5 1 70 180 -34.12

[0177] 10 dimonium chloride

[0178] B26 Novethix L- Benzyl dimethyl 0.5 1 70 200 -33.14

[0179] 10 alkyl ammonium

[0180] B27 Novethix L- B ehentrimonium 0.5 1 70 187 -29.13

[0181] 10 methosulfate

[0182] B28 Novethix L- Octyl-cholinium 0.5 1 70 165 -29.44

[0183] 10

[0184] B29 Novethix L- Hexyl-cholinium 0.5 1 70 170 -30.15

[0185] 10

[0186] B30 Novethix L- Vedeqsa® 0.5 1 70 181 -33.14

[0187] 10

[0188] B31 Novethix L- Mirenat-G® 0.5 1 70 169 -34.23

[0189] 10

[0190] B32 Novethix L- Cocamidopropyl 0.5 1 70 176 -33.26

[0191] 10 betaine:

[0192] (Dehyton®)

[0193] B33 Novethix L- Tetrabutylammoni 0.5 1 70 180 -31.53

[0194] 10 um chloride,

[0195] B34 Aqua SF-2 Tetrabutylammoni 0.5 1 70 169 -33.14 um hydrogen

[0196] sulfate

[0197] B35 Aqua SF-2 Cetylpyridinium 0.5 1 70 187 -29.43 chloride

[0198] B36 Aqua SF-2 Tetrabutylammoni 0.5 1 70 179 -31.24 um chloride,

[0199] B37 Aqua SF-2 Tetrabutylammoni 0.5 1 70 184 -33.45 um hydrogen

[0200] sulfate

[0201] B38 Aqua SF-2 Cetylpyridinium 0.5 1 70 183 -29.24 chloride

[0202] B39 Aqua SF-2 Distearoylethyl 0.5 1 70 167 -33.23 dimonium chloride

[0203] B40 Aqua SF-2 Benzyl dimethyl 0.5 1 70 180 -33.24 alkyl ammonium

[0204]

[0205] B41 Aqua SF-2 B ehentrimonium 0.5 1 70 185 -31.21 methosulfate

[0206] B42 Aqua SF-2 Octyl-cholinium 0.5 1 70 190 -29.23 B43 AQUAPOL® Hexyl-cholinium 0.5 1 70 175 -28.33

[0207] SF-1,

[0208] B44 AQUAPOL® Vedeqsa® 0.5 1 70 178 -28.53

[0209] SF-1,

[0210] B45 AQUAPOL® Mirenat-G® 0.5 1 70 180 -31.44

[0211] SF-1,

[0212] B46 AQUAPOL® Cocamidopropyl 0.5 1 70 185 -34.10

[0213] SF-1, betaine

[0214] (Dehyton®)

[0215] B47 AQUAPOL® Tetrabutylammoni 0.5 1 70 179 -35.20

[0216] SF-1, um chloride,

[0217] B48 AQUAPOL® Tetrabutylammoni 0.5 1 70 181 -32.34

[0218] SF-1, um hydrogen

[0219] sulfate

[0220] B49 AQUAPOL® Cetylpyridinium 0.5 1 70 184 -31.20

[0221] SF-1, chloride

[0222] B50 AQUAPOL® Tetrabutylammoni 0.5 1 70 186 -29.25

[0223] SF-1, um chloride,

[0224]

[0225] The above formulation with different commercially available different acrylic polymer nanoparticles (see the trade name in Table 3) with their fixed 0.5 % (w / w) concentration and 0.5 % (w / w) the different ion pairing agents (different types of positively charged molecules) and 1 % (w / w) of drug molecules (diclofenac) result stable formulation in the 30 to 95 % of ethanol solution. Particle sizes ranged from 160 nm to 205 nm, with negative zeta potentials (-29 mV to 40 mV) depending on the ion-pairing agents. Moreover, it is important to note that the overall charges of the resultant ion pairing molecule+drug complex loaded into the particles do not change much of the charge of the drug loaded nanocarrier. As mentioned above this is due to the interaction between particles and the drug complex through the hydrophobic interaction of the alkyl chain of ionpar molecules and not through the ionic interaction between the ion pairing agent and the negatively charged acrylic nanoparticles.

[0226] EXAMPLE 4:

[0227] Preparation of acrylic nanoparticles and their formulation:Preparation of Acrylic Nanoparticles by Emulsion Polymerization:

[0228] Materials: Butyl acrylate: 6.00 g, Methyl methacrylate: 3.00 g, Acrylic acid: 1.00 g, Sodium dodecyl sulfate (SDS): 0.30 g, Polyvinyl alcohol (optional stabilizer): 0.20 g, Ammonium persulfate (APS): 0.10 g, Sodium bicarbonate: 0.05 g, Deionized water: 39.35 g

[0229] Procedure: A 100 mL three-neck round-bottom flask equipped with a mechanical stirrer, condenser, and nitrogen inlet was charged with 35.00 g deionized water, 0.30 g SDS, 0.20 g polyvinyl alcohol, and 0.05 g sodium bicarbonate. The mixture was stirred at 500 rpm until complete dissolution and purged with nitrogen for 20 minutes. A monomer mixture comprising 6.00 g butyl acrylate, 3.00 g methyl methacrylate, and 1.00 g acrylic acid was prepared separately and added slowly to the aqueous phase over 15 minutes under stirring to form a uniform emulsion. The reaction temperature was raised to 70 ± 2°C. Polymerization was initiated by addition of 0.10 g ammonium persulfate dissolved in 4.35 g deionized water. The reaction was maintained at 70°C for 4 hours under nitrogen and continuous stirring. After completion of polymerization, the batch was cooled to room temperature and filtered through a 0.45 pm filter to remove any coagulum. A stable acrylic nanoparticle dispersion was obtained. The resulting articles typically contains about 20 wt% polymer solids and acrylic nanoparticles in the approximately 80-250 nm size range, depending on stirring speed and surfactant level. The acrylic nanoparticles name as “ANEP”.

[0230] Example 5:

[0231] Preparation of Poly(acrylic acid) Nanoparticles by Inverse Emulsion Polymerization Materials: Acrylic acid: 3.00 g, N, N'-methylenebisacrylamide (crosslinker): 0.06 g, Deionized water: 2.50 g, Sodium hydroxide (10% solution): q.s. to partial neutralization (-20%), Cyclohexane: 20.00 g, Sorbitan monooleate (Span 80): 1.20 g, Polysorbate 80 (Tween 80): 0.30 g Initiator: Ammonium persulfate: 0.05 g, Deionized water: 0.50 g

[0232] Procedure: The organic phase was prepared by dissolving 1.20 g Span 80 and 0.30 g Tween 80 in 20.00 g cyclohexane under stirring. Separately, the aqueous monomer phase was prepared by mixing 3.00 g acrylic acid, 0.06 g N, N'-methylenebisacrylamide, and 2.50 g water. The acrylic acid solution was partially neutralized to approximately 20% neutralization using sodium hydroxide solution. The aqueous phase was added slowly to the organic phase under high-speed stirring(1000-1500 rpm) to form a stable water-in-oil emulsion. The temperature was adjusted to 65 °C, and polymerization was initiated with 0.05 g APS dissolved in 0.50 g water. The reaction was continued for 4 hours. After completion, the nanoparticles were isolated by addition of excess ethanol, centrifuged, and washed three times with ethanol / water to remove residual surfactants and organic solvent. The product was dried under vacuum at 40°C. Crosslinked poly(acrylic acid) nanoparticles or microparticles having high carboxyl group density were obtained. The prepared acrylic nanoparticles name as “ANREP”.

[0233] Table-4

[0234] Batch Acrylic lonpairing lonpairing Diclofen Ethanol Particle polymer molecules molecules ac (ml) Size nanocarrier (g) (g) (nm) B126 ANEP Cetrimde 0.5 1 70 169

[0235] (0.5 %)

[0236] B127 ANEP Cetrimide 5 10 70 433

[0237] (2.5 %)

[0238] B128 ANREP Cetrimide 0.5 1 70 195

[0239] (0.5 %)

[0240] B129 ANREP Cetrimide 5 10 70 450

[0241]

[0242] (2.5 %)

[0243] EXAMPLE 6

[0244] Preparation of formulation using other drugs and their physicochemical properties All formulations in a 100 ml batch were prepared by adding 0.5 % (0.5 g) of the acrylic polymer Aqua SF-2 nanocarriers [as mentioned in Table 5] to 10 ml of water. Then, pH was adjusted to 6-7 by adding 20% TEA (Triethanolamine). 0.5 to 3 % (0.5 g to 3 g) of drug from their 15 to 20 % (w / w) stock solution in 60% ethanol solution (different drugs see Table 5) was added and stirred for 15 minutes to obtain a homogenous mixture of drug. Once the homogeneous mixture was formed, 1% (1 g) of cetrimide (ion-pairing agent) was added to the drug-acrylic polymer nanocarrier mixture and stirred for 15 minutes. Once the mixture was homogenised, the volumewas made up with ethanol and water to obtain a 30:70 (water: ethanol) ratio. The prepared formulation was stored for further studies. Table 5 provides the details of the various formulations prepared.

[0245] All different formulations in 100 ml batch using different drugs were prepared by similar technique as described in example 1. The prepared formulations (Table 5) were stored for further studies.

[0246] Table 5

[0247] Batch Acrylic Cetrimi Drug Ethanol Particle Zeta PDI polymer de (g) (g) (g) Size potential nanocarrier (g) (nm)

[0248] B60 0.5 1 1 70 165 -34.4 0.012 Ibuprofen

[0249] B61 0.5 1 1.5 70 179 -36.5 0.04 Naproxen

[0250] B62 0.5 1 2 70 190 -38.5 0.089 Ketoprofen

[0251] B63 0.5 1 2 70 196 -39.8 0.10 Ketorolac

[0252] B64 0.5 1 3 70 200 -36.7 0.13 Naproxen

[0253] B67 0.5 1 2 70 186 41.3 0.120 Fusidic acid

[0254] B68 0.5 1 1.5 70 178 -40.5 0.08 Azelaic acid

[0255] B69 0.5 1 1.5 70 182 -42.1 0.09 Minoxidil

[0256] sulfate

[0257] B70 0.5 1 1 70 165 -36.2 0.05 Valproic acid

[0258] B71 0.5 1 1 70 164 -36.1 0.088 Tolfenamic

[0259] acid analogs

[0260]

[0261] B72 0.5 1 1.5 70 185 -38.2 0.078 Ibuprofen

[0262] B73 0.5 1 1.5 70 188 -37.2 0.093 Ketoprofen

[0263] B74 0.5 1 2 70 199 -37.1 0.078 Naproxen

[0264] B75 0.5 1 1.5 70 177 -43.2 0.080 Flurbiprofen

[0265] B76 0.5 1 2 70 198 -40.1 0.108 Aceclofenac

[0266] B77 0.5 1 1 70 175 -38.2 0.089 Aceclofenac

[0267] B78 0.5 1 0.5 70 159 -36.5 0.067 Aceclofenac

[0268]

[0269] The above formulation with Aqua SF-2 commercially available acrylic polymer nanoparticles (see the trade name in Table 5) with their fixed 0.5 % (w / w) concentration and 1 % (w / w) of the cetrimide ion pairing agents and 0.5 to 3 % (w / w) of different drug molecules results stable formulation in the 70 % ethanol solution. Particle sizes ranged from 160 nm to 200 nm, with negative zeta potentials (-29 mV to -40 mV) depending on the nature of drug molecules and the amount of drug molecules in the formulation with fixed ion-pairing agents. Moreover, it is important to note that the overall charges of the resultant ion pairing molecule+drug complex loaded into the particles do not change much of the charge of the drug loaded nanocarrier. As mentioned above this is due to the interaction between particles and the drug complex through the hydrophobic interaction of the alkyl chain of ionpar molecules and not through the ionic interaction between the ion pairing agent and the negatively charged acrylic nanoparticles. It is concluded that our ionpairing of drug molecules is a versatile platform and can be easily adapted with a broad range of drug molecules having preferably a negative charge with functional group -COOH, -SOs", -PO4.

[0270] EXAMPLE 7

[0271] Effect of amount of salicylic acid on the formulation

[0272] All different formulations in 100 ml batch were prepared by taking 0.5 (0.5 g) of Aqua SF-2 and Novethix L-10 acrylic polymer nanocarrier [as mentioned in table 6] in 10 ml water. Then, pH was adjusted to 6-7 by adding 20% TEA (Triethanolamine). 1% (1 g) of drug (diclofenac sodium from20 % w / w solution) was added and stirred for 15 minutes to obtain a homogenous mixture of drug. Once the homogenous mixture was formed, 1 % ( 1 g) of cetrimide (ion pairing agent) was added into the drug-acrylic polymer nanocarrier mixture and stirred for 15 minutes. Once the mixture was homogeneously mixed, 0 to 10 % w / w of methyl salicylate / salisylic acid and 0.5 5 w / s menthol was added to the mixture and stirred for another 15 minutes. The volume was made up with ethanol to obtain a ratio of 30:70 (water: ethanol). The prepared formulation was stored for further studies. Table 3 provides the details of the various formulations prepared.

[0273] The different formulations, as mentioned in Table 3 was prepared following the method provided in example 1.

[0274] Table 6

[0275] Batch (Drug Acrylic Cetrimid Drug Ethanol Particle Zeta Methyl Mentho molecules + polymer e (g) (g) (g) Size potential Salicylate 1 (g) Acrylic nanocarrier (nm) (g) particles) (g)

[0276] B79 0.5 1 1 70 165.3 -34.4 0 5 Ibuprofen

[0277] +AQUAPO

[0278] L® SF-1,

[0279] B80 0.5 1 1 70 189.2 -34.5 5 5 Ibuprofen

[0280] +AQUAPO

[0281] L® SF-1,

[0282] B81 0.5 1 1 70 290 -28.5 10 5 Ibuprofen

[0283] +AQUAPO

[0284] L® SF-1,

[0285] B82 0.5 1 1 70 169.2 -29.3 0 5 Diclofenac

[0286] + Aqua SF- 2

[0287] B83 0.5 1 1 70 185.3 -34.3 5 5 Diclofenac

[0288] +Aqua SF-2

[0289]

[0290] B84 0.5 1 1 70 292.6 -28.3 10 5 Diclofenac

[0291] +Aqua SF-2

[0292] B85 0.5 1 1 70 300.6 -35.2 0 5 Diclofenac+

[0293] Novethix L- 10

[0294] B86 0.5 1 1 70 298.2 -33.3 10 5 Diclofenac

[0295] +Novethix

[0296] L-10

[0297] B87 0.5 1 1 70 292.6 -28.3 10 0 Diclofenac

[0298] +Aqua SF-2

[0299]

[0300] The physicochemical characterization of the formulation was performed and analyzed in a DLS (dynamic light scattering) instrument. The results are as presented in table 6. All the formulation show low PDI (<0.1) confirming stable formulation in presence of methyl salicylate and menthol. However, the physicochemical properties of different diclofenac and ibuprufan formulation with salicylic acid, showed increase in the particles size with increase of the salicylate concentration attributing association of salisylate with the particles. However, there are no systematic changes in their zeta potential confirming that the salicylate molecules is not directly interacting with acrylic polymer nanoparticles rather involve in the interaction with the ion pairing molecules where the whole complex might be interacting with the acrylic nanoparticle through hydrophobic interaction. The release behavior of different formulation and effect of methyl salicylate is discussed below section.

[0301] EXAMPLE 8

[0302] Ex-vivo Release of Drug from the formulation using Pig ear skin

[0303] In this study, formulations obtained in example 1 were tested for release studies using Pig ear skin, which represents the human skin.

[0304] Preparation of Pig skin for release studies:

[0305] For the release study, pig ear skin [procured from a slaughter house in Secunderabad, Hyderabad, Telangana, India] was carefully peeled off from the bone and cut off into small pieces (1.5 cmdiameter). The pieces were soaked into 0.1N NaOH and stirred for 6 hours with frequent change of 0.1 NaOH for the removal of non-collagenous proteins. Then, the skin was cleaned with PBS and stirred in 1: 1 acetone / isopropanol for 24 hours for the removal of fat content. For removal of inorganic compounds, this precleaned skin was stirred with IN HC1 for 24 hours with change of solvent for every 6 hours. Once cleaned, the skin pieces were stored in PBS at 4°C.

[0306] Release studies

[0307] The pretreated clean skin was cleaned with 0.1M PBS. 300 pl of the formulation was sprayed evenly on the PBS treated skin and dried for 1 hour at RT. The formulation sprayed pig skin was loaded into the Franz-diffusion cell with bath volume of 20 ml of PBS. Then, 1ml of PBS was added on top of skin to allow the diffusion. Then, 500 ul of supernatant was taken at predetermined time interval (0 hr, 5 hrs, 10 hrs, 15 hrs, 20 hrs, 25 hrs) and stored at 4°C for further studies.

[0308] EXAMPLE 9

[0309] Ex vivo Release of Drug from the formulation using the synthetic membrane Strat-M.

[0310] In this study, specific formulations obtained in example Table 1 to 6 were tested for release using synthetic human skin, Strat-M using following process and the result are discussed below.

[0311] The in vitro release study of the different formulations [Table 1 to 6] was performed using a Franz diffusion cell system. The volume of each receptor chamber was 25 mL. The system temperature was maintained at 37 °C, and the receptor medium was continuously stirred at 600 rpm. A Strat-M® membrane, skin mimic for transdermal diffusion testing, was used as the barrier membrane. The membrane was mounted between the donor and receptor compartments of the Franz diffusion cell, with the dense shiny side facing the donor compartment and the porous side facing the receptor compartment. Subsequently, 200 pL of 1.2 (commercially available diclofenac formulation) and 100 pL of our specific formulation (Table 1 to 6) were applied onto the shiny surface of the membrane and allowed to dry for at least 1 hour. Before initiating the experiment, the system was preheated to stabilize the temperature at 37 °C. After temperature stabilisation, each receptor chamber was completely filled with 1 x PBS, ensuring the medium was in direct contact with the underside of the membrane. The release study was then initiated, and samples were collected at predetermined time intervals. At each sampling point, 500 pL of the receptor medium was withdrawn, transferred to Eppendorf tubes, and stored at 4 °C for further analysis. To maintainconstant volume and sink conditions in the receptor chamber, an equal volume (500 pL) of fresh 1 x PBS was added immediately after each sampling.

[0312] Quantification of drug using HPLC method

[0313] Chromatographic conditions: Diclofenac concentration in the receptor samples was determined using a reverse-phase HPLC system equipped with a UV detector. Diclofenac released into the receptor medium was quantified by RP-HPLC using a C18 column (250 mm x 4.6 mm, 5 pm). The mobile phase consisted of acetonitrile:methanol:0.05 M phosphate buffer pH 3.0 (50: 10:40, v / v / v). The flow rate was 1.0 mL / min, column temperature was maintained at 30°C, injection volume was 20 pL, and detection was carried out at 276 nm. Diclofenac was quantified using an external calibration curve prepared in the range of 1-50 pg / mL. Separation was achieved on a C18 analytical column maintained at ambient temperature. The mobile phase comprised an aqueous acidic buffer and an organic solvent, such as acetonitrile or methanol, in a suitable ratio to obtain symmetrical diclofenac peak shape and acceptable retention. The mobile phase was filtered and degassed before use. The flow rate was maintained at about 1.0 mL / min, and the injection volume was typically 10-20 pL. Detection was performed at a wavelength suitable for diclofenac, preferably around 276 nm.

[0314] Standard preparation and calibration: A diclofenac and other drugs listed in the table 1 to 6 reference standard stock solution of 500 pg / mL was prepared, and a series of dilutions was used to obtain calibration standards over an appropriate concentration range. A calibration curve was generated by plotting peak area versus concentration, and the diclofenac content in the samples was calculated from the corresponding regression equation depicted in Figure 2. Note that Figure 1 is the representative standard plot of diclofenac. A similar standard plot was generated for the other drugs.

[0315] Example 10:

[0316] Sustained release of diclofenac from the formulation made from different acrylic nanocarriers using Pig ear skin as membrane:

[0317] Two different formulations using different acrylic polymer nanocarrier (a) Aqua SF-2 (Bl), and (b) Novethix L-10 (B2) were prepared as mentioned in Example 2. The release study of the drug was performed using Pig ear skin as mentioned above example 8. Figure 2 shows the release profileof the two formulations. The release profiles of the two samples are shown in Figure 3, with sustained drug release up to 24 hours. 100 % release of the drug was observed at 24-25 hours, confirming sustained and long-lasting up to 24 hours for the painkiller drug through the skin.

[0318] Example 11:

[0319] Effect of Methyl Salicylate on the release profile of the formulation measured by START-M It is important to check the possible release profile of the sustained released formulation in presence of the most common associated pain release molecules such as methyl salicylate and menthol. Here we have prepared different formulations following the method in Example 7. Four different formulations (B79, B82, B84) of ibuprofen and diclofenac with variable concentration of methyl salicylate and menthol were subjected to their release study using synthetic human skin, START -M. The release study of the drug was performed using START-M example 9. Figure 4 shows the release profile of the four formulations. Figure 4 shows the release profile of diclofenac from Aqua SF-2 formulations containing (a) 10% salicylic acid, (b) 5% salicylic acid, and (c) 0% salicylic acid. The results showed that there is no significant effect of the sustained-release behaviour of diclofenac in the presence of methyl salicylate. However, higher concentration of methyl salicylate increases the drug release rate and achieve 100 per cent release within 24 hours. Similar sustained-release behaviour is observed for ibuprofen from the formulation B79. It further confirms the sustained-release profile of all formulations containing different drug molecules, in the presence or absence of other associated pain-relief molecules such as methyl salicylate and menthol.

[0320] Example 12:

[0321] Loading Efficiency of diclofenac in different formulations

[0322] It is important to maximise the loading of drug molecules into the nanocarrier. Loading efficiency was determined by adding 100 pL of the respective formulations (see Table 1 to 6) to 900 pL of IN HC1. This formulation mixture was incubated overnight (12 hours). The mixture was then centrifuged at 5000 RPM for 10 minutes. The supernatant was then analysed by HPLC using a drug-specific protocol. The area of the respective HPLC graph is used to estimate the amount using the respective standard plot. The loading efficiencies of diclofenac, ibuprofen, ketoprofen, minoxidil sulfate, tolfenamic acid analogues, and aceclofenac were measured and reported in Table7. Important to note that these formulations also contain different nanocarrier and different ion pairing agents.

[0323] Table 7

[0324] Formulation Percentage of loading (%)

[0325] B82 94.4

[0326] B83 92.3

[0327] B84 90.9

[0328] B86 96.2

[0329] B87 96.4

[0330] B8 98.2

[0331] B13 96.2

[0332] B21 97.2

[0333] B38 96.2

[0334] B46 97.2

[0335] B49 95.2

[0336] B60 98.2

[0337] B62 95.2

[0338] B69 94.2

[0339] B71 98.2

[0340] B77

[0341]

[0342] 98.1

[0343] The loading efficiency of the different formulations of different drugs, with various nanocarriers and ion -pairing agents with varying concentrations of salicylic acid resulted in more than 90%, and a minor increase in the loading efficiency was observed in the presence of salicylic acid. However, the particle size of the formulation was observed to increase with an increased concentration of salicylic acid. The zeta potential of the formulation also increased in negative values, which may be due to the association of salicylic acid with the formulation.

[0344] EXAMPLE 13Diclofenac formulations using an amino acid as an ion pairing agent

[0345] All formulations in a 100 ml batch were prepared by adding 0.5% (0.5 g) of Aqua SF-2 acrylic polymer nanocarrier, as mentioned in Table 6, to 10 ml of water. Then, pH was adjusted to 6-7 by adding 20% TEA. 1 % ( 1 g) of diclofenac sodium (from a 20% solution) was added to the mixture and stirred for 15 minutes to obtain a homogeneous mixture of the drug. Once the homogeneous mixture had been formed, 1% (1 g) of different amino acids (ion -pairing agents) was added to the drug-acrylic polymer nanocarrier mixture and stirred for 15 minutes. Once the mixture was opaque, 5% or 10% methyl salicylate was added to the mixture and stirred for 15 minutes. The volume was made up of ethanol to obtain a 30:70 (water: ethanol) ratio. The prepared formulations were stored for further studies.

[0346] Table 8

[0347] Batch Amino acid Acrylic Amino Diclofenac Salicylic acid Ethanol polymer acid (g) (g) (g) % nanocarrier ml (g)

[0348] B89 Arginine 0.5 1 1 5 70 B90 Lysine 0.5 1 1 5 70 B91 Histidine 0.5 1 1 5 70 B92 Tryptophan 0.5 1 1 5 70

[0349]

[0350] B93 Lysine 0.5 2 2 5 70

[0351] The physicochemical characterization of the formulation was performed and analyzed in a DLS (dynamic light scattering) instrument. The results are as presented in table 7.

[0352] Table 9

[0353] Name Size (nm) Zeta (mv) PH

[0354] B89 342.9 -16.5 6.8

[0355] B90 401.6 -14.3 6.8

[0356] B91 263.5 -31.5 6.8

[0357] B92 349.5 -21.3 6.8

[0358]

[0359] B93 340.5 -25.3 6.8The physicochemical properties of different diclofenac formulation with different amino acids showed no change in their zeta and particle sizes of polymer nanocarriers. All the formulations using amino acid as ion-pairing agent show sustained releases of the drug as discussed before. Moreover, the form the stable suspension with average particles size between 263 nm to 401 nam and negative zeta potential, confirming their interaction to the nanocarrier mainly through their hydrophobic interaction with partially through their ionic interaction as well.

[0360] Ex-vivo Release of Drug from the formulation using Pig ear skin

[0361] The release study was performed for each formulation using pig ear skin as per the protocol provided in Example 9, and the results obtained are as provided in Figure 5. Figure 5 shows the release profile of diclofenac from different formulations with different amino acids. The release profiles of the different amino acid formulations show sustained drug release up to 24 hours (Figure 5).

[0362] EXAMPLE 14

[0363] Diclofenac formulation using amino acid as ion paring agent and variation of drug to amino acid ratio where acrylic polymer nanocarrier kept constant

[0364] All different formulations in 100 ml batch were prepared by taking 0.5% (0.5 g) of Aqua SF-2 acrylic polymer nanocarrier, as mentioned in Table 8, in 10 ml water. Then pH was adjusted to 6-7 by adding 20 % TEA. 1% (1 g) of diclofenac sodium drug (from the 20 % of diclofenac stock solution) was added to the mixture and stirred for 15 minutes to obtain a homogenous mixture of the drug. Once the homogenous mixture was formed, 1 % ( 1 g) of different amino acids (ion pairing agent) were added into the drug-acrylic polymer nanocarrier mixture and stirred for 15 minutes. The volume was made up of ethanol to achieve a 30:70 (water: ethanol) ratio. The prepared formulation was stored for further studies.

[0365] Table 10

[0366] Batch Ion pairing Acrylic Amino Diclofenac Salicylic acid Ethanol % agent polymer acid (g) (g) (g) ml

[0367] nanocarrier

[0368]

[0369] (g)B94 Arginine 0.5 1 1 0 70 B95 Arginine 0.5 2 1 0 70 B96 Arginine 0.5 3 1 0 70 B97 Arginine 0.5 1 2 0 70

[0370]

[0371] B98 Cetrimide 0.5 1 1 0 70

[0372] The physicochemical characterisation of the formulation was performed and analysed in a DLS (dynamic light scattering) instrument. The results are presented in Table 11.

[0373] Table 11

[0374] SI. Description Size Zeta potential PDI

[0375] No (Ratio) (nm) (mV)

[0376] B99 Diclofenac: Arginine 337.8 -18.7 0.748 (1:1)

[0377] 385.3 -24.1 0.823 629.9 -20.7 0.722 B100 Diclofenac: Arginine 744.2 -14.8 0.543 (1:2)

[0378] 973 -18.7 0.523 788.7 -16.0 0.590 B101 Diclofenac: Arginine 1607 -38.7 0.804 (1:3)

[0379] 1062 -37.0 0.648 1196 -66.6 0.666 B102 Diclofenac: Arginine 668.3 -29.0 0.676 (2:1)

[0380] 742 -38.3 0.766 759.2 -46.3 0.529

[0381]

[0382] B103 Diclofenac with 164.0 -27.3 0.146 Cetrimide (1%)

[0383] 168.2 -29.7 0.165 169.9 -28.5 0.150

[0384]

[0385] The physicochemical properties of different diclofenac formulation with different ion pairing agent showed no change in their zeta and particle sizes of polymer nanocarriers.

[0386] Ex-vivo Release of Drug from the formulation using pig ear skin

[0387] The release study was performed for each formulation (B99, B100, B101) using pig ear skin as per the protocol provided in example 11 and results obtained are as provided in Figure 6. Figure 6 shows the release profile of diclofenac from different formulations with variable percentages of drug and amino acids. The release profile of different arginine formulations showed sustained release of drug. However, the increase of amino acid (arginine) with respect to drug (1:3) lead to faster release of drug through the skin.

[0388] EXAMPLE 15

[0389] Effect of ion-pairing molecules concentration on the drug release

[0390] AAll different formulations in a 100 ml batch were prepared by taking 0.5% (0.5 g) of AQUAPOL® SF-1, acrylic polymer nanocarrier, as mentioned in Table 12, in 10ml of water. Then pH was adjusted to 6-7 by adding 20% TEA. 1% to 4% (1g to 4g) of diclofenac sodium (from a 20% w / w diclofenac stock) was added to the gel and stirred for 15 minutes to obtain a homogeneous mixture. Once the homogenous mixture was formed, 0.3 % to 3 % (0.3 g to 3 g) of cetrimide (ion pairing agent) was added into the drug- acrylic polymer nanocarrier mixture and stirred for 15 minutes. The volume was made up of ethanol to obtain a 20:80 (water: ethanol) ratio. The prepared formulations were stored for further studies.

[0391] Table 12

[0392] Batch Acrylic Cetrimide Diclofenac Salicylic acid Ethanol polymer (g) (g) (g) ml nanocarrier

[0393] (g)

[0394] B104 (A) 1

[0395]

[0396] 0.5 0.3 0 80B105 (B) 0.5 0.5 1 0 80 B106 (C) 0.5 1 1 0 80

[0397] B 107(D) 0.5 1 2 0 80

[0398] B108(E) 0.5 1 3 0 80

[0399]

[0400] B 109 (F) 0.5 1 4 0 80

[0401] Ex-vivo Release of Drug from the formulation using pig ear skin

[0402] The release study was performed for each formulation using pig ear skin, as per the protocol in Example 2, and the results are shown in Figure 7. Figure 7 shows the release profile of diclofenac from different formulations with varying per cent cetrimide and diclofenac, showing that a 1: 1 ratio of cetrimide: diclofenac results in sustained release up to 24 hours. The increase in the drug contraction with constant cetrimide (ion-pairing agent) results in an initial burst release followed by a sustained release of the drugs.

[0403] EXAMPLE 16

[0404] Formulation using diclofenac ethanol amine (DDEA) and release profile

[0405] All formulations in a 100 ml batch were prepared by adding 0.5% (0.5 g) of EUDRAGIT® NM 30 D (B110, B112, B113), and Aqua SF-2, (B114, B115, B116) and the polymer nanocarrier as mentioned in Table 13 to 10 ml of water. Then the pH was adjusted to 6.8-7 by adding 20 % TEA.

[0406] 1 % ( 1 g) of diclofenac diethylamine (DDEA) / diclofenec epolaamin (DEA) was added and stirred for 15 minutes to obtain a homogeneous mixture of the drug. Once the homogenous mixture was formed, 0.1 % to 1 % (0.1 g to 1 g) of cetrimide (ion pairing agent) was added into the drug-acrylic polymer nanocarrier mixture and stirred for 15 minutes. The volume was made up of ethanol to obtain a ratio of 20:80 (water: ethanol). The prepared formulations (Table 13) were stored for further studies.

[0407] Table 13

[0408] Batch Acrylic Cetrimide DDEA Salicylic acid Ethanol polymer (g) (g) (g) ml nanocarrier

[0409] (g)

[0410] B110 0.5 1 1 0 80

[0411] B112 0.5 1 1.5 0 80

[0412]

[0413] B113 0.5 1 2 0 80B114 0.5 1 1 0 80 B115 0.5 1 1.5 0 80

[0414] B116 0.5 1 2 0 80

[0415] Diclofenec Epolaamin (DEA)

[0416]

[0417] B117 0.5 0.1 2 0 80

[0418] Ex-vivo Release of Drug from the formulation using pig ear skin

[0419] The release study was performed for each formulation using pig ear skin, as per the protocol in Example 7, and the results are shown in Figure 8. Figure 8 shows the release profiles of diclofenac from different formulations with varying percentages of cetrimide and diclofenac diethylamine (DDEA). The release profile of diclofenac diethylamine (DDEA) with a variable ratio of drug: cetrimide showed sustained release of the drug and 100 % release of the drug was not observed even after 24 hours of release. Moreover, it is important to note that even the release profile does not change much in the case of different acrylic nanocarrier systems. This result shows that the DDEA formulation provides sustained drug release beyond 24 hours.

[0420] EXAMPLE 17

[0421] Formulation using linear acrylic polymer nanocarrier and diclofenac

[0422] All different formulations in 100 ml batch were prepared by taking 0.5 to 5% (0.5 g to 5 g) of acrylic polymer (carbomer C-940, Lubrizol), as mentioned in Table 14, in 50 ml of different ratios of ethanol 90%. Then pH was adjusted to 6-7 by adding 20% TEA or NaOH. The required amount of plasticiser and propylene glycol was added, followed by stirring for 15 min to homogenise. 1 to 5% (1 g to 5 g) of diclofenac or DDEA was added to the gel and stirred for 15 minutes to obtain a homogenous mixture of drug in the gel. Once the homogeneous mixture had been formed, 1% to 5% (1 g to 5 g) of cetrimide (ion -pairing agent) was added to the drug-acrylic polymer nanocarrier mixture and stirred for 15 minutes. The volume was made up to 100 ml with ethanol and water, resulting in a final ethanol concentration of 95% (v / v). The prepared formulations (Table 12) were stored for further studies.

[0423] The preferred plasticizers include triethyl citrate, dimethyl isosorbide, acetyltributyl citrate, castor oil, propylene glycol, and polyethylene glycol, or two or more of the above in combination.Table 14

[0424] Batch Acrylic Cetrimide Diclofenac Propylene Ethanol Water (ml) polymer (g) (g) glycol (g) (ml)

[0425] nanocarrier

[0426] (g)

[0427] B118 0.5 1 1 1 85 15 B119 2 2 2 3 90 10 B120 5 5 5 6 95 05

[0428] DDEA

[0429] B121 0.5 1 1 1 85 15 B122 2 2 2 3 90 10

[0430]

[0431] B123 5 5 5 6 95 05

[0432] EXAMPLE 18

[0433] Diclofenac-cetrimide ion-pair sustained-release gel

[0434] Materials: Diclofenac sodium: 1.00 to 3 g, Cetrimide: 1.05 to 3 g, Carbopol® Aqua SF-1 polymer: 1.40 g to 2 gm, Propylene glycol: 8.00 g, Glycerin: 3.00 g, Ethanol: 10.00 g, Purified water: q.s. to 100 g, Optional disodium EDTA: 0.05 g

[0435] Method of preparation: 55 g purified water was added to a mixing vessel and stirred. Disodium EDTA, propylene glycol, and glycerin were added stir until clear. Carbopol® Aqua SF-1 to 2 g of polymer was slowly added with continuous stirring and mixed for 30–45 minutes until a uniform gel base is obtained. In a separate vessel, 1 to 3 g of diclofenac sodium in 8 g of water and 6 g of ethanol were added. Similarly, in another vessel, 1 g to 3 g cetrimide was added to 4 g of water and 4 g of ethanol. Cetrimide solution was slowly added to the diclofenac solution over 10-15 minutes with stirring to form an ion-pair concentrate. Then it was stirred for 30 minutes, then allowed to stand for 15-30 minutes. Following the addition of the ion-pair concentrate, slowly add it to the Aqua SF-1 gel base over 10-15 minutes under low-to-moderate stirring. Mixing was continuing for 30–45 minutes until homogeneous. pH was adjusted to 5-7.4. The required amount of water is added to make the total bath of 100 g, and mixed gently to make the final gel formulation, andstored for further use. The viscosity of the gel formulation was approximately 8,000-15,000 cP. A release study using the START-M membrane shows sustained release of diclofenac.

[0436] Batch Acrylic Cetrimide Diclofenac Propylene Ethanol Glycerin EDTA polymer (g) (g) glycol (g) (ml) (ml) and other nanocarrie ingradien r (g) t B130 1.40 1 1 8 10 3 0.05 to 0.5 B131 1.90 2 2 8 10 3 0.05 to 0.5 B132 2.0 3 3 8 10 3 0.05 to

[0437]

[0438] 0.5

[0439] EXAMPLE 19

[0440] In vivo evaluation of different formulation and their duration of action after one application All different formulations in a 100 ml batch were prepared by a similar technique as described in Example 2. All different formulations in a 100 ml batch were prepared by taking 0.5 to 2 (0.5 g to 2 g) % of Aqua SF-2 acrylic polymer nanocarrier [as mentioned in Table 13] in 10 to 20 ml of water. Then, pH was adjusted to 6-7 by adding 20% TEA (Triethanolamine). 2 to 3% (2 g-3g) of the drug (diclofenac sodium) was added, and the mixture was stirred for 15 minutes to obtain a homogeneous mixture. Once the homogeneous mixture was formed, 1.5% to 2% (1.5 g to 2 g) of cetrimide (ion-pairing agent) was added to the drug-acrylic polymer nanocarrier mixture and stirred for 15 minutes. Once the mixture was homogenised, 0-10% methyl salicylate was added and stirred for another 15 minutes, followed by the addition of menthol. The volume was made up with ethanol to obtain a ratio of 30:70 (water: ethanol). The prepared formulation was stored for further studies. Table 15 provides the details of the various formulations prepared.

[0441] Table 15

[0442] Batch Acrylic Cetrimide Diclofenac Methyl Menthol Ethanol polymer (g) Salicylate (ml)

[0443] (g) (g)

[0444]

[0445] (g)nanocarrier

[0446] (g)

[0447] B124 0.5 1.5 3 10 5 70 B125 2 2 2 0 0 70 Commercial Diclofenac Diethylamine- 4.64%w / v, Diclofenac Sodium 4% w / v

[0448]

[0449] Formulation: I

[0450] Analgesic effect study in the rat model by the Hot Plate Analgesiometer

[0451] A hot plate was used in this method and set at a temperature of 55-56°C. The rats [(SD rats aged 8-10 weeks, procured from ICMR-NARFBR (National Animal Resource Facility for Biomedical Research)] were placed on the hot plate and their behavioural response (jumping, paw licking, and rearing) was recorded for 15 seconds.

[0452] For testing the analgesic activity, the formulations were applied on the rats topically and allowed to dry. Then, the animals were placed on a hot plate and the behavioral response was recorded. Each formulation was applied once, then the readings were recorded till 48 hours with planned intervals. Table 16 provides the response time of different formulations in the rat pow application. Figure 8 shows the analgesic effect of different formulations compared to commercial Dynapar.

[0453] Table 16

[0454] II iiiiii

[0455] Commercial

[0456] formulation

[0457] B37

[0458]

[0459] It was inferred from the table 16 and figure 8 that formulations B37 and B38 of the present invention provided analgesic effects till 24 hours, whereas the commercial ones provided analgesic effects till 9 hours. The formulations of the present invention with variable concentration ofnanocarrier, drug and ion-pairing agent (B37 and 38) provide sustained release of drug as discussed before, resulting in analgesic effect till 24 hrs to the rat.

[0460] Example 20:

[0461] Release profile of the other active molecules from the sustained release formulation using START-M membrane.

[0462] Ex vivo Release of Other Pain Drug molecules from the formulation using the synthetic membrane Strat-M.

[0463] In this study, specific formulations obtained in examples Table 1 to 6 (B71, B73, B77) were tested for release using synthetic human skin, Strat-M, using the following process, and the results are discussed below.

[0464] The in vitro release study of the different formulations [B71, B73, B77] was performed using a Franz diffusion cell system. The volume of each receptor chamber was 25 mL. The system temperature was maintained at 37 °C, and the receptor medium was continuously stirred at 600 rpm. A Strat-M® membrane, skin mimic for transdermal diffusion testing, was used as the barrier membrane. The membrane was mounted between the donor and receptor compartments of the Franz diffusion cell, with the dense shiny side facing the donor compartment and the porous side facing the receptor compartment. Subsequently, 200 pL of 1.2 (commercially available diclofenac formulation) and 100 pL of our specific formulation (Table 1 to 6) were applied onto the shiny surface of the membrane and allowed to dry for at least 1 hour. Before initiating the experiment, the system was preheated to stabilize the temperature at 37 °C. After temperature stabilisation, each receptor chamber was completely filled with 1× PBS, ensuring the medium was in direct contact with the underside of the membrane. The release study was then initiated, and samples were collected at predetermined time intervals. At each sampling point, 500 µL of the receptor medium was withdrawn, transferred to Eppendorf tubes, and stored at 4 °C for further analysis. To maintain constant volume and sink conditions in the receptor chamber, an equal volume (500 µL) of fresh 1× PBS was added immediately after each sampling. Figure 10 shows the release profile of the Ketoprofen,, Aceclofenac, and Tolfenamic acid analogues from their respective formulation. All the drug molecules show sustained release upto 24 hrs and beyond.

[0465] Example 21:Release profile of the other active molecules from the sustained release formulation using START-M membrane.

[0466] In this study, specific formulations obtained in examples Table 1 to 6 (B67, B68, B69, B70) were tested for release using synthetic human skin, Strat-M, using the following process, and the results are discussed below.

[0467] The in vitro release study of the different formulations [B67, B68, B69, B70] was performed using a Franz diffusion cell system. The volume of each receptor chamber was 25 mL. The system temperature was maintained at 37 °C, and the receptor medium was continuously stirred at 600 rpm. A Strat-M® membrane, skin mimic for transdermal diffusion testing, was used as the barrier membrane. The membrane was mounted between the donor and receptor compartments of the Franz diffusion cell, with the dense shiny side facing the donor compartment and the porous side facing the receptor compartment. Subsequently, 200 µL of 1.2 (commercially available diclofenac formulation) and 100 µL of our specific formulation (Table 1 to 6) were applied onto the shiny surface of the membrane and allowed to dry for at least 1 hour. Before initiating the experiment, the system was preheated to stabilize the temperature at 37 °C. After temperature stabilisation, each receptor chamber was completely filled with 1× PBS, ensuring the medium was in direct contact with the underside of the membrane. The release study was then initiated, and samples were collected at predetermined time intervals. At each sampling point, 500 µL of the receptor medium was withdrawn, transferred to Eppendorf tubes, and stored at 4 °C for further analysis. To maintain constant volume and sink conditions in the receptor chamber, an equal volume (500 µL) of fresh 1× PBS was added immediately after each sampling. Figure 11 shows the release profile of the Fusidic acid, Azelaic acid, Minoxidil sulfate, and Valproic acid from their respective formulation. All the drug molecules show sustained release up to 24 hrs and beyond.

[0468] Example 22:

[0469] In vitro biocompatibility study of the pain killer formulations

[0470] Human dermal fibroblasts (HDF) were procured from HiMedia, India. HDF were routinely cultured in fibroblast basal medium (HiMedia, India) supplemented with 10% (v / v) FBS (Gibco, USA) and 1% penicillin and streptomycin (Gibco, USA) in T75 flask (NuncTM, Thermofisher Scientific) in a CO2 incubator (Thermo Fisher, USA) at 37°C with 5% CO2 and 95% humidity, and the culture medium was changed every 2-3 d until 70%-80% confluency was achieved. Followingthis, the confluent cells were trypsinized (trypsin / EDTA; Invitrogen Corporation), and cell suspensions were prepared.

[0471] In vitro biocompatibility evaluation of acrylic nanoparticles, diclofenac and pain killer formulation: In vitro biocompatibility of different pain killer formulations and free nanocarrier, as well as free ion-pairing agent and drug, were evaluated on HDF cells along with a control group of tissue culture polystyrene (TCPS) samples. 3000 cells / well were seeded in 96-well plates to determine proliferation at 24, 48, and 72 hours with free nanocarrier, drug, ion-pairing agent, diclofenac ion-pairing agent, and pain-killer formulation. The MTT assay (Sigma, MO, USA) was used to quantitatively measure the in vitro cytotoxicity and cell proliferation. After incubation, the medium was removed and the wells were washed. 100 µL of MTT (0.5 mg / mL) was added to each well and incubated in the dark for 4 h at 37 °C under 5% CO₂. After the incubation time, the solution was removed and 100 µL of DMSO was added to each well and shaken to completely dissolve the formazan crystals. The absorbance was measured at 595 nm using a plate reader (iD5 Molecular Devices, USA). Fluorescence microscopy imaging of HDF was conducted to qualitatively evaluate cell density or number of cells on the respective well plate in the presence of a particular concentration. The viability or biocompatibility of free drugs / ion-pairing agent and pain killer is shown in Figures 12 to 14. Figure 12 shows the viability of acrylic nanocarrier (Aqua-SF) and diclofenac (free), confirming 100 % cell viability corresponding to the concentration of nanocarrier 1000 ug / ml and 25 ug / ml for free diclofenac at 24 hours of incubation. Similarly, Figure 13 shows the cell viability of formulation (Bl), free cetrimide, diclofenac (free), and cetrimide+diclofenac (free). The viability related to the diclofenac formulation follows the cetrimide concentration, with an IC50 of 6 ug / ml at 48 hours and 12 ug / ml at 24 hours. Figure 14 shows similar cell viability for the formulation (B90) and the free ion-pairing agent (lysine) at different incubation times (24 to 72 hours). The cell viability of all free lysine, nanocarrier, and painkiller formulations is excellent (-100% viability) at concentrations above 1000 pg / ml, similar to that of the nanocarrier (Aqua SF).

[0472] Example 23.

[0473] Confirming the nanoscale coating on the skin after application of the formulation

[0474] Around 100 µL of the formulation (B20) was placed on the pig ear skin (1 cm specimen) and allowed to air dry for 5 min. The size and surface morphology of the nanoparticles coating wereanalysed using cryo-scanning electron microscopy (Cryo-SEM) employing a JEOL field-emission scanning electron microscope equipped with a cryogenic preparation system. A small cut of the coated skin was rapidly frozen in liquid nitrogen (−196°C) to preserve the native, hydrated structure of the nanoparticles and prevent aggregation or drying artefacts. The frozen sample was transferred under vacuum into a cryo-preparation chamber, where it was fractured and sublimated at approximately −90°C for 5–10 minutes to remove superficial ice and expose the nanoparticle surface. The sample was subsequently sputter-coated with a thin, conductive platinum or gold layer (~5 nm thick) to minimise charging effects during imaging. The specimen was then transferred to the cryo-SEM stage maintained at approximately −140°C and imaged using the JEOL fieldemission scanning electron microscope operating at 3–5 kV and a working distance of 6–10 mm. Images were acquired at various magnifications to evaluate the particle morphology, surface structure, and size distribution. The average nanoparticle size was determined by measuring at least 100 particles from multiple micrographs using image analysis software. Cryo-SEM imaging enabled visualisation of nanoparticles in a near-native hydrated state, allowing accurate assessment of particle size and morphology. SEM images of the formulation coating on the skin are depicted in Figure 15 at different magnifications. The images confirm the nano formulation uniformly coats the skin surface as individual nanoparticles, not as a film. The particle size is between 100 and 150 nm, further confirming the invisible coating on the skin.

[0475] It should be noted that the description and figures merely illustrate the principles of the present subject matter. It should be appreciated by those skilled in the art that conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present subject matter. It should also be appreciated by those skilled in the art that by devising various systems that, although not explicitly described or shown herein, embody the principles of the present subject matter and are included within its spirit and scope. Furthermore, all examples recited herein are principally intended expressly to be for pedagogical purposes to aid the reader in understanding the principles of the present subject matter and the concepts contributed by the inventor(s) to further the art and are to be construed as being without limitation to such specifically recited examples and conditions. The novel features, which are believed to be characteristic of the present subject matter, both as to its organisation and method of operation, together with further objects and advantages, will be better understood from the following description when considered in connection with the accompanying figures.

Claims

WE CLAIM:

1. A sustained release formulation comprising:an acrylic polymer nanocarrier in an amount in the range of 0.01 to 20 w / w %; an ion-pairing agent in an amount in the range of 0.01 to 20 w / w %;at least one therapeutic agent in an amount in the range of 0.01 to 20 w / w %;at least one solvent in an amount in the range of 0 to 99 % w / w; anda pH-adjusting agent in an amount sufficient to adjust the pH of the formulation to a range of 4 to 8.

2. The sustained release formulation as claimed in claim 1, wherein the ratio of acrylic polymer nanocarrier to ion-pairing agent mass is in a range of 0.5:0.05 to 0.5:0.10, preferably 0.5:0.5 to 0.5:5, preferably 0.5:1 to 0.5:3, preferably 0.5:1 to 0.5:3,wherein the ratio of acrylic polymer, ion-pairing agent and drug mass is in a range of 0.5:0.05:0.05 to 0.5:10:30, preferably 0.5:0.1:0.5 to 0.5:5:10, preferably 0.5:l:l to 0.5:3:3, preferably 0.5:1:1 to 0.5:1.5:1.5, preferably 0.5:l:0.1 to 0.5:1.5:1.5, preferably 0.5:l:0.2 to 0.5:1.5:1.5 and preferably 0.5:l:0.5 to 0.5: 1.5: 1.5.

3. The sustained release formulation as claimed in claim 1, wherein the acrylic polymer nanocarrier is selected from the group consisting of carbomers, acrylates / alkyl acrylate crosspolymers, acrylates copolymers, and polyacrylate crosspolymers, or any commercially available aqueous dispersion thereof,wherein the pH-adjusting agent is any base not limited to such as triethanolamine (TEA) and NaOH.

4. The sustained release formulation as claimed in claim 1, wherein the ion-pairing agent is selected from the group consisting of a quaternary ammonium salt of formula R–N+(CH3)3X–, wherein R is a C2-C18 alkyl group and X is selected from Cl–, Br–, or MeSO4–. preferably wherein R is C12-C14; tetraalkylammonium salts of formula R4N+X–, wherein R is C4-C18 alkyl; alkylpyridinium salts of formula [R–pyridinium]+X–; benzyl-dimethyl-alkyl-ammonium salts of formula [R–N+(CH3)2–CH2Ph] X–; quatemized amino-ester compounds having the generalformula [R-C(O)O-CH2CH2-N+(CH3)2-CH2CH2-O-C(O)-R] X; cholinium salts of formula [HO-CH2-CH2-N+(CH3)3] X; amino- acid-based quaternary ammonium surfactants of formula R-CO-NH-(CH2)n-N+(CH3)2R'X or R-CO-NH-(CH2)n-N+(CH3)3X, wherein R is a C10–C16fatty chain; quaternary silane compounds; and zwitterionic betaine-type compounds, including but not limited to dodecyltrimethylammonium, tetradecyltrimethylammonium, hexadecyltrimethylammonium, decyltrimethylammonium salts; tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium hydrogen sulfate, tetrabutylammonium phosphate, tetrahexylammonium bromide, tetrahexylammonium chloride; cetylpyridinium chloride, benzalkonium chloride; distearoylethyl dimonium chloride, dipalmitoylethyl hydroxyethylmonium salts, behentrimonium methosulfate; choline chloride and N-alkyl cholinium salts; ethyl lauroyl arginate hydrochloride; lysine-derived surfactants; cocamidopropyl betaine; 3-(trimethoxysilyl)-propyloctadecyl-dimethyl ammonium chloride; glycine betaine, choline, carnitine, butyrobetaine, homarine, and trigonelline,wherein the ion-pairing agent is selected from the group consisting of cetrimide, arginine, lysine, histidine, and tryptophan.

5. The sustained release formulation as claimed in claim 1, wherein the therapeutic agent comprises a molecule having negative, or zwitterionic character, preferably comprising an anionic functional group selected from -COO, -SO3, or –PO4–or capable of forming a negatively charged species, and wherein the therapeutic agent is selected from the group consisting of a nonsteroidal anti-inflammatory drug, an anesthetic agent, an antibiotic, an analgesic, an antiviral agent, a hormone, an antiaging agent, and other therapeutic agents such as ibuprofen, naproxen, ketoprofen, ketorolac, flurbiprofen, indomethacin, salicylic acid, mefenamic acid, zaltoprofen, aceclofenac, diclofenac, fusidic acid, azelaic acid, tranexamic acid, valproic acid, salbutamol sulfate, cromolyn sodium, minoxidil sulfate, methotrexate, clodronic acid, and tolfenamic acid.

6. The sustained release formulation as claimed in claim 1, wherein the solvent is selected from the group consisting of water, ethanol, isopropyl alcohol, acetone, n-butanol, methylene chloride, and methylene dimethyl ether, or a mixture thereof.

7. The sustained release formulation as claimed in claim 1, wherein the formulation further comprises a preservative, a stabilizer, a surfactant, a buffering agent and an antioxidant.8 The sustained release formulation as claimed in claim 1, wherein the formulation is in form of patch, and topical spray.

9. A process for preparing a sustained release formulation as claimed in claim 1 comprising:a. dissolving an acrylic polymer nanocarrier in a first solvent to obtain a polymer solution;b. adjusting the pH by a range of 4 to 8 of the polymer solution by adding a pH-adjusting agent, thereby obtaining a gel;c. adding at least one therapeutic agent to the gel and stirring for 15-20 minutes to obtain a first homogenous mixture;d. adding an ion-pairing agent to the first homogenous mixture and stirring for 15-20 minutes to obtain a second homogeneous mixture;e. adding a second solvent to the second homogeneous mixture and mixing to obtain the sustained release formulation.

10. The process as claimed in claim 9, wherein the first solvent and second solvent are each independently selected from the group consisting of water, ethanol, isopropyl alcohol, acetone, n-butanol, methylene chloride, and methylene dimethyl ether, or a mixture thereof, wherein the pH-adjusting agent base, such as triethanolamine, NaOH etc,wherein the process optionally comprises adding a preservative, a stabilizer, a surfactant, a buffering agent and an antioxidant after step (d) and before step (e).

11. The process as claimed in claim 9, wherein the therapeutic agent comprises a molecule having negative, or zwitterionic character, preferably comprising an anionic functional group selected from -COO, –SO3–, or –PO4–or capable of forming a negatively charged species, and wherein the therapeutic agent is selected from the group consisting of a nonsteroidal anti-inflammatory drug, an anesthetic agent, an antibiotic, an analgesic, an antiviral agent, a hormone, an antiaging agent, ibuprofen, naproxen, ketoprofen, ketorolac, flurbiprofen, indomethacin, salicylic acid, mefenamic acid, zaltoprofen, aceclofenac, diclofenac, fusidic acid, azelaic acid, tranexamicacid, valproic acid, salbutamol sulfate, cromolyn sodium, minoxidil sulfate, methotrexate, clodronic acid, and tolfenamic acid.

12. A process for preparing a sustained release gel formulation comprising:a. dissolving an acrylic polymer nanocarrier along with propylene glycol and glycerin in a first solvent to obtain a polymer solution;b. adding at least one therapeutic agent into a mixture of the first solvent and a second solvent to obtain a therapeutic solution;c. dissolving an ion-pairing agent in a mixture of first solvent and second solvent in a separate vessel to obtain an ion-pairing agent solutiond. Adding at least one drug to ion-pairing agent or vice versa to make drug-ion-pairing complex mixture and stirring for about 15 to 30 mine. slowly adding the drug-ion-pairing complex mixture into the polymer solution with stirring for 15 minutes, followed by additional stirring to obtain a uniform solution f. Addition of the remaining first solvent along with excipients to make upto a specific batch sizeg. adjusting the pH by a range of 5 to 7.4 of the polymer solution by adding a pH-adjusting agent, thereby obtaining a final gel formulation.

13. The process as claimed in claim 9, wherein the first solvent and second solvent are each independently selected from the group consisting of water, ethanol, isopropyl alcohol, acetone, n-butanol, methylene chloride, and methylene dimethyl ether, or a mixture thereof, wherein the pH-adjusting agent base, such as triethanolamine, NaOH etc,wherein the process optionally comprises adding a preservative, a stabilizer, a surfactant, a buffering agent and an antioxidant after step (d) and before step (e),wherein the excipient is selected from a group consisting ofas propylene glycol, glycerol, polyethylene glycol.

14. The process as claimed in claim 12, wherein the therapeutic agent comprises a molecule having negative, or zwitterionic character, preferably comprising an anionic functional group selected from -COO, –SO3–, or –PO4–or capable of forming a negatively charged species, and whereinthe therapeutic agent is selected from the group consisting of a nonsteroidal anti-inflammatory drug, an anesthetic agent, an antibiotic, an analgesic, an antiviral agent, a hormone, an antiaging agent, ibuprofen, naproxen, ketoprofen, ketorolac, flurbiprofen, indomethacin, salicylic acid, mefenamic acid, zaltoprofen, aceclofenac, diclofenac, fusidic acid, azelaic acid, tranexamic acid, valproic acid, salbutamol sulfate, cromolyn sodium, minoxidil sulfate, methotrexate, clodronic acid, and tolfenamic acid.

15. A method for providing delivery of therapeutic agents in mammals by administering / applying the sustained release formulation for the treatment of conditions related to acne, alopecia therapy, rosacea, pain management and melasma, wherein a single application of the formulation provides sustained release of the therapeutic agent for a period of up to 24 hours- 48 hours.

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