Chitosan composition used as tissue separating agent or filling agent

Abstract

Compositions and methods of making and using the same are described. The composition may comprise chitosan cross-linked with tripolyphosphate and calcium, optionally, the composition is made by combining particles comprising chitosan and tripolyphosphate with calcium ions, such as calcium ions provided by calcium salts.

Description

Cross-references to related applications

[0001] This application claims priority to U.S. Provisional Application No. 63 / 582,335, filed September 13, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure generally relates to compositions that can be used for tissue separation and / or as filler materials, and related methods of preparation and use. For example, this disclosure includes cross-linked chitosan compositions that can be used as interstitial spacers or fillers. Background Technology

[0003] Filler or lifting materials can be used for a variety of conditions and medical procedures. For example, patients undergoing urological procedures may benefit from the separation of tissue layers, such as separating the prostate from the rectum during radiotherapy for prostate cancer to protect the rectum from radiation. Patients diagnosed with endoscopy-related conditions and / or undergoing endoscopic procedures may also require materials for filling fistulas and / or separating tissue. Fistulas are abnormal channels that form between organs, blood vessels, or other tissues and can be repaired by filling them. Biocompatible materials can also be used as lifting agents, for example, when separating tissue during the removal of polyps, adenomas, gastrointestinal lesions, or early-stage cancerous tissue. Summary of the Invention

[0004] This disclosure includes compositions and methods of preparation and use thereof. For example, this disclosure includes a composition comprising chitosan crosslinked with tripolyphosphate and calcium. Optionally, the composition is prepared by mixing particles comprising chitosan and tripolyphosphate with calcium ions, such as calcium ions from a calcium salt. The calcium salt may comprise, for example, calcium chloride. The composition can be prepared by combining (mixing) a suspension of the particles comprising chitosan and tripolyphosphate with a calcium salt, wherein the suspension is aqueous. According to some aspects of this disclosure, the suspension also comprises polyethylene glycol, a surfactant, or both. In some instances, the composition is prepared by combining the particles comprising chitosan and tripolyphosphate with an aqueous solution of calcium chloride, optionally wherein the aqueous solution of calcium chloride is a supersaturated solution. The composition may be in gel form, such as a crosslinking matrix for gel particles. The crosslinking between calcium and the particles is reversible; the addition of a saline solution disrupts the crosslinking structure of the composition. In some aspects, the average particle size of the chitosan and tripolyphosphate-containing particles is from about 100 micrometers to about 700 micrometers, for example, from about 100 micrometers to about 300 micrometers. In some instances, the composition contains from about 10% to about 99% of the chitosan crosslinked with tripolyphosphate and calcium, based on the total weight of the composition. This disclosure also includes the use of the compositions described above and in other parts thereof, for example, as lifting agents, spacer materials, or filler materials, such as embolic fillers or fistula fillers. For example, the composition can be applied to a target site by combining the chitosan and tripolyphosphate-containing particles with calcium ions to form the composition at the target site of a subject. The target site may contain soft tissue, and the composition achieves separation of tissue layers at the site. In some instances, the target site contains a fistula, and the composition partially or completely fills the fistula. The composition can be applied to the target site via a catheter. Optionally, the chitosan and tripolyphosphate-containing particles are applied to the target site simultaneously with calcium ions.

[0005] This disclosure also includes a method of treating a subject, the method comprising applying a composition to a target site of the subject, wherein the step of applying the composition includes combining particles comprising chitosan and tripolyphosphate with calcium ions to form a cross-linked material. The calcium ions may be provided by a calcium salt solution, such as calcium ions in a calcium chloride solution. According to some aspects, the average particle size of the particles comprising chitosan and tripolyphosphate is from about 100 micrometers to about 700 micrometers. The composition may be applied via a catheter. According to some aspects of this disclosure, the step of applying the composition includes simultaneously combining the particles with calcium ions at the target site. The method may further include adding an aqueous saline solution to the composition and removing at least a portion of the composition from the target site. In at least one exemplary method, the target site is a fistula, and the composition partially or completely fills the fistula. In at least one exemplary method, the target site is soft tissue, and the composition achieves separation of tissue layers. For example, the target site may be the region between the pancreas and the abdominal cavity or gallbladder of the subject.

[0006] This disclosure also includes a method for preparing a composition comprising combining particles comprising chitosan and tripolyphosphate with a calcium salt solution to form a composition, wherein the composition comprises chitosan crosslinked with tripolyphosphate and calcium. The composition can be prepared by combining an aqueous suspension of the particles with a calcium salt solution. Optionally, the aqueous suspension further comprises polyethylene glycol, a surfactant, or both. In some examples, the calcium salt solution comprises calcium chloride, and / or the calcium salt solution is a supersaturated solution. In some examples, the average particle size of the particles comprising chitosan and tripolyphosphate is from about 100 micrometers to about 700 micrometers.

[0007] This disclosure also includes a method of treating a subject, the method comprising combining an aqueous suspension containing chitosan and tripolyphosphate particles with a calcium salt solution at a target site of the subject to form a cross-linked material, thereby applying the composition to the target site. In some instances, the aqueous suspension also contains polyethylene glycol, a surfactant, or both. According to some aspects, the target site is a fistula or soft tissue in the urinary tract or gastrointestinal tract. For example, the composition can be administered via a catheter. Attached Figure Description

[0008] The accompanying drawings, which are incorporated herein by reference and form part of this application, illustrate various exemplary embodiments and, together with the specification, serve to explain the principles of the disclosed embodiments.

[0009] Figure 1 illustrates an exemplary reaction diagram of some aspects of this disclosure.

[0010] Figure 2 shows chitosan particles (left) and an exemplary composition made from the chitosan particles (right), see Example 1 for details.

[0011] Figures 3A-3B show photomicrographs of the exemplary compositions prepared in Example 1. Detailed Implementation

[0012] The various aspects of this disclosure will be described in more detail below. In the event of any conflict between the terms and definitions provided herein and those incorporated by reference, the terms and definitions provided herein shall prevail.

[0013] The terms “comprising,” “including,” or any other variations thereof, as used herein, are intended to cover non-exclusive inclusion, such that a method, process, composition, article, or apparatus that comprises a list of elements may include not only those elements but also other elements not expressly listed or inherent to the method, process, composition, article, or apparatus. The term “exemplary” herein means “example” rather than “ideal.”

[0014] The singular forms “a,” “an,” and “the / that” used herein include plural references unless the context clearly specifies otherwise. The terms “about” and “approximately” refer to something substantially the same as the value or quantity cited. In this document, the terms “about” and “approximately” should be understood to cover ±5% of the specified value or quantity.

[0015] Embodiments of this disclosure include compositions comprising biocompatible materials, and related methods for preparing and applying said compositions to target sites. The compositions described herein can be used for a variety of conditions and medical procedures, such as as lifting agents, spacers, or fillers. For example, patients undergoing urological or endoscopic procedures may benefit from increased spacing between organs, such as separating the prostate from the rectum during radiotherapy for prostate cancer to protect the rectum from radiation. Furthermore, fistula repair can be achieved, for example, by partially or completely filling a fistula. The compositions described herein can also be used as lifting agents, for example, to achieve separation of tissue layers, thereby facilitating the removal of polyps, adenomas, gastrointestinal lesions, and / or early-stage cancerous tissue. The compositions described herein can also be used as embolic fillers, for example, for vessels in various highly vascularized tumors, including uterine fibroids and arteriovenous malformations. The compositions described herein can be formulated into cross-linked materials (e.g., gels) with desired density and / or viscosity to maintain the structural integrity of the material at the target site. As further detailed below, the cross-linking is reversible, and the structure of the cross-linked matrix or gel can be broken down, for example, dissolved or otherwise destroyed. This property is useful when the composition is applied in an improper position and the misaligned composition needs to be removed.

[0016] The compositions described herein may contain cross-linked chitosan. For example, the compositions may contain components formed by cross-linking chitosan with tripolyphosphate (TPP) and calcium (e.g., calcium ions Ca²+).

[0017] Chitosan is a linear polysaccharide composed of glucosamine units derived from chitin, a structural component of the exoskeleton of crustaceans. . Chitosan is typically prepared by deacetylation of chitin with alkaline reagents such as sodium hydroxide, resulting in a water-soluble material. Chitosan can be cross-linked with tripolyphosphate to form particles. An exemplary method for preparing such particles is described in U.S. Patent Application Publication 2021 / 0322629A1.

[0018] In preparing the compositions described herein, chitosan particles (e.g., particles containing chitosan cross-linked with tripolyphosphate) are mixed with divalent calcium ions capable of binding to available phosphate groups (e.g., phosphate groups of tripolyphosphate) on the particles to form a cross-linked matrix. This is illustrated in the final step of the exemplary reaction diagram shown in Figure 1. The calcium ion source can be a biocompatible salt, such as calcium chloride.

[0019] According to some aspects of this disclosure, the particles can be mixed with calcium ions at or near a target site of a subject to prepare the composition, for example, by crosslinking at the target site to form a gel matrix or other crosslinked material, or subsequently applied to the target site. When the particles are mixed with calcium ions, they can be in the form of a suspension or a slurry, such as an aqueous suspension or an aqueous slurry.

[0020] The chitosan particles in the compositions described herein may have a particle size suitable for application to in vivo sites, such as via catheters or other medical devices suitable for endoscopic and / or urological delivery. Particle size can be characterized by morphological analysis (e.g., static automated imaging). For example, various particle parameters, including equivalent circle diameter, length, width, circumference, area, maximum distance, equivalent sphere volume, and aspect ratio, can be analyzed using a Malvern Morphologi 4 morphological analyzer. For the purposes of this disclosure only, the term "average particle size" as used herein refers to the equivalent circle diameter, which is defined as the diameter of a circle with the same area as the particle. According to some examples in this article, the average particle size of chitosan particles is about 100 nanometers to about 700 micrometers, such as about 250 nanometers to about 700 micrometers, about 400 nanometers to about 700 micrometers, about 650 nanometers to about 700 micrometers, about 100 nanometers to about 600 micrometers, about 100 nanometers to about 500 micrometers, about 100 nanometers to about 400 micrometers, about 100 nanometers to about 300 micrometers, about 100 nanometers to about 200 micrometers, or about 100 nanometers to about 100 micrometers. In some examples in this article, the average particle size may be less than about 700 micrometers, less than about 650 micrometers, less than about 600 micrometers, less than about 550 micrometers, less than about 500 micrometers, less than about 450 micrometers, less than about 400 micrometers, less than about 350 micrometers, less than about 300 micrometers, less than about 250 micrometers, less than about 200 micrometers, or less than about 150 micrometers.

[0021] The suspension or slurry of particles may contain water (e.g., deionized water) and optionally one or more reagents or fillers to increase viscosity and / or keep the particles in suspension for easy delivery. For example, the slurry or suspension may also contain polyethylene glycol, chitosan solution, surfactants, or combinations thereof.

[0022] According to some aspects of this disclosure, the concentration of chitosan particles (particles containing chitosan and tripolyphosphate) in the slurry or suspension is from about 1 mg / mL to about 50 mg / mL, for example, from about 1 mg / mL to about 45 mg / mL, from about 1 mg / mL to about 40 mg / mL, from about 1 mg / mL to about 35 mg / mL, from about 1 mg / mL to about 30 mg / mL, from about 1 mg / mL to about 25 mg / mL, from about 1 mg / mL to about 20 mg / mL, from about 5 mg / mL to about 25 mg / mL, from about 5 mg / mL to about 15 mg / mL, from about 10 mg / mL to about 30 mg / mL, from about 15 mg / mL to about 45 mg / mL, from about 20 mg / mL to about 40 mg / mL, from about 25 mg / mL to about 30 mg / mL, from about 30 mg / mL to about 50 mg / mL, or from about 35 mg / mL to about 45 mg / mL.

[0023] A suspension or slurry of particles can be mixed with an aqueous calcium salt solution, which serves as a calcium ion source. For example, the calcium salt may comprise calcium chloride. In some instances, the concentration of the salt solution is from about 0.1 M to about 2 M, for example from about 0.5 M to about 1.5 M, with an exemplary concentration of about 1 M. According to some aspects of this disclosure, the salt solution may be a supersaturated solution.

[0024] The relative amounts of chitosan suspension / slurry and salt solution can be determined based on the properties of the target site (e.g., target site size) and the desired characteristics of the crosslinking material. In at least one example, 10-20 mL of 1 M calcium chloride solution is mixed with 10-30 mL of an aqueous suspension / slurry containing 25 mg / mL chitosan particles (particles containing chitosan and tripolyphosphate).

[0025] As described above, the structure of the gel / crosslinked material can be decomposed if needed. Gel formation is reversible; the addition of a saline solution (physiological saline) can disrupt the crosslinked structure of the material. For example, a saline solution can disrupt the crosslinked structure formed by calcium ions and phosphate groups, thereby restoring it to a chitosan suspension or slurry as needed. This property is beneficial for the removal of the composition, for example, when it is molded and / or applied to the wrong location, or when excessive composition remains after a medical procedure. Example

[0026] The following examples are intended to illustrate this disclosure and are not intended to limit the scope of protection of this disclosure. It is understood that this disclosure covers other aspects and implementations consistent with the foregoing description and the following examples.

[0027] Example 1

[0028] A cross-linked composition was prepared by mixing particles containing chitosan and tripolyphosphate with a salt solution. The particles, obtained by decanting an aqueous solution, are shown in the left image of Figure 2. 0.2 g of the particles were immersed in a 1 M calcium chloride solution to form a cross-linked matrix, as shown in the right image of Figure 2. The microstructure of the material was analyzed by scanning electron microscopy / energy dispersive spectroscopy (SEM / EDS), and the results are shown in Figures 3A and 3B. The boxed areas in Figures 3A and 3B represent regions of relatively high calcium chloride concentration detected by energy dispersive spectroscopy, indicating that calcium ions formed cross-linking bridges between the particles. The scale bar in Figure 3A is 100 μm, and the scale bar in Figure 3B is 500 μm. The obtained cross-linked particles formed a sponge-like, well-adhered matrix that could be shaped within the voids in the matrix.

[0029] Other aspects of this disclosure will become clear to those skilled in the art through reading the specification and practicing the embodiments disclosed herein. This specification and embodiments should be considered exemplary only, and the true scope and spirit of this disclosure are defined by the appended claims.

Claims

1. A composition comprising chitosan crosslinked with tripolyphosphate and calcium, optionally, said composition being prepared by combining particles comprising chitosan and tripolyphosphate with calcium ions, such as calcium ions from calcium salts.

2. The composition according to claim 1, wherein, The composition is prepared by mixing a suspension of particles containing chitosan and tripolyphosphate with a calcium salt, wherein the suspension is aqueous.

3. The composition according to claim 2, wherein, The suspension also contains polyethylene glycol, surfactants, or both.

4. The composition according to any one of the preceding claims, wherein, The calcium salt contains calcium chloride.

5. The composition according to any one of the preceding claims, wherein, The composition is prepared by combining the particles containing chitosan and tripolyphosphate with an aqueous solution of calcium chloride, optionally wherein the aqueous solution of calcium chloride is a supersaturated solution.

6. The composition according to any one of the preceding claims, wherein, The composition is in gel form.

7. The composition according to any one of the preceding claims, wherein, The cross-linking between calcium and particles is reversible; the addition of a salt solution disrupts the cross-linking structure of the composition.

8. The composition according to any one of the preceding claims, wherein, The average particle size of the particles containing chitosan and tripolyphosphate is from about 100 micrometers to about 700 micrometers, for example from about 100 micrometers to about 300 micrometers.

9. The composition according to any one of the preceding claims, wherein, The composition comprises, by total weight of the composition, about 10% to about 99% of the chitosan crosslinked with tripolyphosphate and calcium.

10. Use of the composition according to any one of claims 1-9 as a lifting agent, spacer material, or filler material, such as an embolic filler or a fistula filler.

11. The use according to claim 10, wherein, The composition is applied to the target site of the subject by combining the particles containing chitosan and tripolyphosphate with calcium ions to form the composition.

12. The use according to claim 11, wherein, The target site comprises soft tissue, and the composition separates tissue layers.

13. The use according to claim 11, wherein, The target site includes a fistula, and the composition partially or completely fills the fistula.

14. The use according to any one of claims 11-13, wherein, The composition is applied to the target site via a catheter.

15. The use according to any one of claims 11-14, wherein, The particles containing chitosan and tripolyphosphate are applied simultaneously with calcium ions to the target site.

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