POLYMER PARTICLES

Description

[0001] The present invention relates to polymer particles for the occlusion of vascular sites and cavities within the body, such as the embolization of vascularized tumors or arteriovenous malformations are described.

[0002] WO2012 / 120138 of Occlugel et al relates to a polymer obtained from the polymerization of: (i) at least one monomer of formula (I) (CH 2 =CR 1 )CO-K (I) wherein: - K represents O-Z or N H-Z, Z representing (CR 2 R 3 )m-CH 3 , (CH 2 -CH 2 -O)m-H, (CH 2 -CH 2 -O)m-CH 3 , (CH 2 )m-NR 4 R 5 with m representing an integer from 1 to 30; - R 1 , R 2 , R 3 , R 4 and R 5 independently represent H or a C1 -C6 alkyl; (ii) at least between 0.1 and 50% mol, advantageously between 1 and 30% mol, more advantageously between 1 and 20 mol % of a cyclic monomer having a exomethylene group of formula (II) wherein: - R 6 , R 7 , R 8 and R 9 represent independently H or a C 5 -C 7 aryl group or R 6 and R 9 are absent and R 7 and R 8 form together with the carbon atom on which they are bonded a C5-C7 aryl group; - i and j represent independently an integer chosen between 0 and 2; - X represents either O or X is not present and in this latter case, CR 6 R 7 and CR 8 R 9 are linked via a single bond C-C and (iii) at least one bio-resorbable block copolymer cross-linker.

[0003] WO2009 / 131982 of Nalco Company describes a composition comprising expandable polymeric microparticles comprising an interpenetrating polymer network (IPN). The IPN constrains the microparticle to an unexpanded volume average particle size diameter of from about 0.05 to about 5,000 microns. Labile cross-links in the polymers of the IPN are subject to degradation, which results in release of the expandable microparticle so that the microparticle expands. The invention is further directed to the use of the composition for modifying the permeability of subterranean formations and increasing the mobilization and / or recovery rate of hydrocarbon fluids present in the formations.

[0004] WO2009 / 073193 of The John Hopkins University describes compositions comprising a hydrogel and an agent, for example a therapeutic agent or an imaging agent, for loco-regional delivery. In certain preferred embodiments of the invention, the hydrogel compositions are detectable by Magnetic Responance and CT Scan and are used for loco-regional delivery of therapeutic agents, for example chemotherapeutic agents. The invention also features polymer matrix compositions comprising nanoparticles that can be loaded after polymerization with bioactive agents, for example a diagnostic agent or therapeutic agent.

[0005] The invention is defined in the appended claims. Accordingly, an aspect of the present invention provides a polymer particle comprising the reaction product of a prepolymer solution including: poly(ethylene glycol) diacrylamide at a concentration of between about 15% w / w and about 50% w / w; and at least one monomer selected from glycerol monomethacrylate, amino ethyl methacrylate, 3-sulfopropyl acrylate, amino propyl methacrylamide, or a combination thereof, wherein the polymer particle is spherical, and has a diameter less than about 1,200 µm, and does not comprise n-isopropyl acrylamide.

[0006] These polymers can be used for / in embolization. The polymer particles are compressible for ease of delivery. The particles can be loaded or coated with a drug(s) or active agent(s).

[0007] An aspect of the present invention provides a method of making a spherical polymer particle comprising: reacting an aqueous based prepolymer solution including poly(ethylene glycol) diacrylamide , at least one monomer, wherein the monomer is glycerol monomethacrylate, amino ethyl methacrylate, 3-sulfopropyl acrylate, amino propyl methacrylamide, or a combination thereof, and an initiator in an oil to form the spherical polymer particle; wherein said spherical polymer particle has a diameter less than about 1,200 µm.

[0008] Further disclosure is provided for information purposes only.Brief Description of the Drawings

[0009] Figure 1 illustrates a plot of average drug loading of particles charged with doxorubicin or irinotecan. Figure 2 illustrates a plot of average drug elution from particles at 22 hours after in situ. Figure 3 illustrates a plot of particle compressibility at 30% deformation. Figure 4 illustrates another plot of particle compressibility at 30% deformation. Figure 5 illustrates a plot of particle time in suspension. Figure 6 illustrates a plot of drug loaded particle time in suspension. Detailed Description

[0010] The invention is defined in the appended claims. The particles can be referred to herein as being microparticles, microspheres, microbeads, spheres, microembolis, embolics, and the like. The particles have diameters less than about 1,200 µm. The particles can also be compressible, biostable, and / or durable for ease of delivery.

[0011] The particles can be formed from a prepolymer solution or mixture comprising: (i) one or more polyether macromers that contain at least two functional groups amenable to polymerization, (ii) optionally one or more monomers, and (iii) optionally one or more multifunctional crosslinkers. A polymerization initiator may be utilized.

[0012] The macromer may include a plurality of functional groups suitable or amenable to polymerization. The macromer can be linear. The macromer can have one or more branches. The macromer can be an ethylenically unsaturated macromer. Macromers can include polyethers. Polyether macromers can include linear or branched poly(ethylene glycol), poly(propylene glycol), poly(tetramethylene oxide), derivatives thereof, or combinations thereof.

[0013] Macromers described herein can have molecular weights of about 200 grams / mole, 400 grams / mole, 600 grams / mole, 800 grams / mole, 1,000 grams / mole, 2,000 grams / mole, 3,000 grams / mole, 4,000 grams / mole, 5,000 grams / mole, 10,000 grams / mole, 15,000 grams / mole, 20,000 grams / mole, 25,000 grams / mole, 30,000 grams / mole, 35,000 grams / mole, between about 200 grams / mole and about 35,000 grams / mole, between about 200 grams / mole and about 30,000 grams / mole, between about 1,000 grams / mole and about 15,000 grams / mole, at least about 200 grams / mole, at most about 30,000 g / mole, or at most about 35,000 grams / mole. Macromers may have a molecular weight of about 10,000 g / mole.

[0014] Derivatives of these polyethers can be prepared to render them amenable to polymerization. While any type of chemistry can be utilized, for example nucleophile / N-hydroxysuccinimde esters, nucleophile / halide, vinyl sulfone / acrylate or maleimide / acrylate; a preferred chemistry is free radical polymerization. As such, polyethers with a plurality of ethylenically unsaturated groups, such as acrylate, acrylamide, methacrylate, methacrylamide, and vinyl, can be used. A polyether macromer can be poly(ethylene glycol) diacrylamide with a molecular weight of about 10,000 g / mole.

[0015] The macromer may be poly(ethylene glycol) diacrylamide, poly(ethylene glycol) diacrylate, poly(ethylene glycol) dimethacrylate, poly(ethylene glycol) dimethacrylamide, derivatives thereof, or combinations thereof. The macromer of the invention is poly(ethylene glycol) diacrylamide.

[0016] Macromers can be included at a concentration in the solution of about 0% w / w, about 1% w / w, about 2% w / w, about 3% w / w, about 4% w / w, about 5% w / w, about 6% w / w, about 7% w / w, about 8% w / w, about 9% w / w, about 10% w / w, about 11% w / w, about 12% w / w, about 13% w / w, about 14% w / w, about 15% w / w, about 16% w / w, about 17% w / w, about 18% w / w, about 19% w / w, about 20% w / w, about 35% w / w, about 30% w / w, about 35% w / w, about 40% w / w, about 45% w / w, about 50% w / w, about 60% w / w, about 70% w / w, between about 5% w / w and about 10% w / w, between about 5% w / w and about 20% w / w, between about 5% w / w and about 25% w / w, between about 5% w / w and about 15% w / w, between about 6% w / w and about 8% w / w, or between about 14% w / w and about 16% w / w. A macromer may need not be used.

[0017] The macromer of the invention is included at a concentration of between about 15% w / w and about 50% w / win the solution.

[0018] If one of the monomer(s) and / or macromers(s) is a solid, a solvent can be used to form a solution from which the particles for use as embolics can be prepared. If liquid monomers and macromers are utilized, a solvent may not be required. Even when using liquid monomers and / or macromers, a solvent may still be used. Solvents may include any liquid that can dissolve or substantially dissolve a polyether macromer, monomers, multifunctional crosslinkers, and / or initiators. Any aqueous or organic solvent may be used that dissolves the desired monomer(s), macromer(s), multifunctional crosslinker(s) and / or polymerization initiators. The solvent can be water. Additionally, solutes, e.g. sodium chloride, may be added to the solvent to increase the rate of polymerization. Solvent concentration can be varied to alter the compressibility of the embolic particle, allowing for delivery through a catheter of smaller inner diameter than the diameter of the particle.

[0019] Solvent concentrations can be about 25% w / w, about 35% w / w, about 45% w / w, about 55% w / w, about 65% w / w, about 75% w / w, about 85% w / w, about 95% w / w, between about 40% w / w and about 80% w / w, between about 30% w / w and about 90% w / w, or between about 50% w / w and about 70% w / w of the solution. The solvent concentration can be about 50% w / w, about 51% w / w, about 52% w / w, about 53% w / w, about 54% w / w, about 55% w / w, about 56% w / w, about 57% w / w, about 58% w / w, about 59% w / w, or about 60% w / w. The solvent concentration can be about 65% w / w, about 66% w / w, about 67% w / w, about 68% w / w, about 69% w / w, about 70% w / w, about 71% w / w, about 72% w / w, about 73% w / w, about 74% w / w, or about 75% w / w.

[0020] The solvent concentration can be about 57% w / w.

[0021] The solvent concentration can be about 70% w / w.

[0022] The solvent concentration can be about 75% w / w.

[0023] In general, monomers can contain moieties such as acrylate, acrylamide, methacrylate, methacrylamide or other moieties amenable to polymerization. The polymer particles may be comprised of one or more macromers combined with one or more monomers. Monomers of the invention are selected from glycerol monomethacrylate, amino ethyl methacrylate, 3-sulfopropyl acrylate, amino propyl methacrylamide, or a combination thereof.

[0024] Optionally, one or more monomers can be added to the polyether macromer to impart desired chemical and / or mechanical properties to the polymer particle. If the binding of positively charged drugs or other materials is desired, monomers with negatively charged moieties, e.g. carboxylic acids, can be polymerized into the particles. Acidic unsaturated monomers can include, but are not limited to, acrylic acid, methacrylic acid, 3-sulfopropyl acrylate, 3-sulfopropyl methacrylate, derivatives thereof, combinations thereof, and salts thereof. If the binding of negatively charged drugs is desired, monomers with positively charged moieties, e.g. amines, can be polymerized into the particles. Basic monomers can include amino ethyl methacrylate, 2-amino ethyl methacrylate, amino propyl methacrylamide, derivatives thereof, combinations thereof, and salts thereof.

[0025] Monomers including positive or negative moieties can be present in solution at concentrations of about 0.5% w / w, about 1% w / w, about 2% w / w, about 3% w / w, about 4% w / w, about 5% w / w, about 6% w / w, about 7% w / w, about 8% w / w, about 9% w / w, about 10% w / w, about 15% w / w, about 20% w / w, about 21% w / w, about 22% w / w, about 23% w / w, about 24% w / w, about 25% w / w, about 26% w / w, about 27% w / w, about 28% w / w, about 29% w / w, about 30% w / w, about 40% w / w, about 50% w / w, about 55% w / w, about 60% w / w, about 65% w / w, about 70% w / w, about 80% w / w, between about 1% w / w and about 10% w / w, between about 1% w / w and about 5% w / w, between about 15% w / w and about 35% w / w, or between about 20% w / w and about 30% w / w.

[0026] A monomer(s) including charged moieties can be included at a concentration of about 14% w / w in the solution.

[0027] A monomer(s) including charged moieties can be included at a concentration of about 24% w / w in the solution.

[0028] 2-amino ethyl methacrylate can be included at a concentration of about 0.7% w / w in the solution.

[0029] Amino propyl methacrylamide can be included at a concentration of about 0.5% w / w in the solution.

[0030] If desired, uncharged, reactive moieties can be introduced into the particles. For example, hydroxyl groups can be introduced into the particles with the addition of 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, glycerol monomethacrylate, glycerol monoacrylate, sorbitol monomethacrylate, sorbitol monoacrylate, a carbohydrate similar to sorbitol and amenable to polymerization, derivatives thereof, or combinations thereof. Alternatively, uncharged, relatively un-reactive moieties can be introduced into the particles. For example, acrylamide, methacrylamide, methyl methacrylate, derivatives thereof, or combinations thereof can be added to the polyether macromer. The monomer(s) can be selected to vary the number of hydroxyl groups in the polymeric particles to enable the particles to remain suspended in radiopaque contrast solution used in the preparation of the particle for clinical use.

[0031] Such uncharged moieties if included can be present in the final particle (not including solvents, initiators, and salts) at about 0% w / w, about 10% w / w, about 20% w / w, about 30% w / w, about 40% w / w, about 50% w / w, about 60% w / w, about 61% w / w, about 62% w / w, about 63% w / w, about 64% w / w, about 65% w / w, about 66% w / w, about 67% w / w, about 68% w / w, about 69% w / w, about 70% w / w, about 71% w / w, about 72% w / w, about 73% w / w, about 74% w / w, about 75% w / w, about 80% w / w, about 90% w / w, between about 50% w / w and about 90% w / w, between about 60% w / w and about 70% w / w, between about 65% w / w and about 70% w / w, or between about 67% w / w and about 69% w / w.

[0032] An uncharged moiety can be present at about 68% w / w of the final particle.

[0033] The uncharged moiety can be glycerol monomethacrylate.

[0034] Adding multifunctional crosslinkers containing more than one moiety amenable to polymerization can create a more cohesive hydrogel polymer by adding crosslinking to the molecular structure. The polymer particles are comprised of a macromer combined with one or more multifunctional crosslinkers such as, but not limited to, glycerol dimethacrylate, glycerol diacrylate, sorbitol dimethacrylate, sorbitol acrylate, a derivatized carbohydrate similar to sorbitol, derivatives thereof, or combinations thereof. A disclosed multifunctional crosslinker is N,N'-methylenebisacrylamide.

[0035] If used, a crosslinker can be present in the solution used to form the particles at a concentration of about 0.1% w / w, about 0.25% w / w, about 0.5% w / w, about 0.75% w / w, about 1.0% w / w, about 1.25% w / w, about 1.5% w / w, about 1.75% w / w, about 2% w / w, about 3% w / w, about 4% w / w, about 5% w / w, about 6% w / w, about 7% w / w, about 10% w / w, about 20% w / w, about 25% w / w, about 30% w / w, between about 0% w / w and about 10% w / w, between about 0% w / w and about 2% w / w, between about 0.5% w / w and about 1.5% w / w, between about 0.25% w / w and about 1.75% w / w, or between about 0.1% w / w and about 2% w / w.

[0036] A crosslinker may be not used.

[0037] A crosslinker can be present at about 1% w / w.

[0038] The crosslinker can be N,N'-methylenebisacrylamide.

[0039] Any amounts of macromer(s), monomer(s), and multifunctional crosslinker(s) can be used in the solution used to form the particles that allows for a desired particle. Total concentration of reactive compounds or solids in the solution can be about 5% w / w, about 10% w / w, about 11% w / w, about 12% w / w, about 13% w / w, about 14% w / w, about 15% w / w, about 16% w / w, about 17% w / w, about 18% w / w, about 19% w / w, about 20% w / w, about 21% w / w, about 22% w / w, about 23% w / w, about 24% w / w, about 25% w / w, about 30% w / w, about 31% w / w, about 32% w / w, about 33% w / w, about 34% w / w, about 35% w / w, about 36% w / w, about 37% w / w, about 38% w / w, about 39% w / w, 40% w / w, about 50% w / w, about 60% w / w, about 70% w / w, between about 10% and 60%, between about 15% w / w and about 50% w / w, or between about 20% w / w and about 40% w / w.

[0040] The total concentration of reactive compounds in the solution can be about 20% w / w.

[0041] The total concentration of reactive compounds in the solution can be about 41% w / w.

[0042] Polymer particles can be prepared from monomers having a single functional group and / or macromers having two or more functional groups suitable for polymerization. Functional groups can include those suitable to free radical polymerization, such as acrylate, acrylamide, methacrylate, and methacrylamide. Other polymerization schemes can include, but are not limited to nucleophile / N-hydroxysuccinimide esters, nucleophile / halide, vinyl sulfone / acrylate or maleimide / acrylate. Selection of the monomers is governed by the desired chemical and mechanical properties of the resulting particle.

[0043] Concentrations of macromers in the final desiccated particle products can be at a concentration of about 10% w / w, about 20% w / w, about 21% w / w, about 22% w / w, about 23% w / w, about 24% w / w, about 25% w / w, about 26% w / w, about 27% w / w, about 28% w / w, about 29% w / w, about 30% w / w, about 35% w / w, about 36% w / w, about 37% w / w, about 38% w / w, about 39% w / w, about 40% w / w, about 41% w / w, about 42% w / w, about 43% w / w, about 44% w / w, about 45% w / w, about 50% w / w, about 60% w / w, about 70% w / w, about 80% w / w, between about 15% w / w and about 60% w / w, between about 20% w / w and about 50% w / w, between about 25% w / w and about 45% w / w, between about 25% w / w and about 40% w / w, between about 35% w / w and about 45% w / w, between about 37% w / w and about 43% w / w, between about 39% w / w and about 41% w / w, between about 25% w / w and about 35% w / w, between about 26% w / w and about 30% w / w, or between about 27% w / w and about 29% w / w.

[0044] The concentration of macromer(s) in the final desiccated particle products can be about 40% w / w.

[0045] The concentration of macromer(s) in the final desiccated particle products can be about 27% w / w.

[0046] Poly(ethylene glycol) diacrylamide is present in the final desiccated particle products at about 40% w / w.

[0047] Poly(ethylene glycol) diacrylamide is present in the final desiccated particle products at about 27% w / w.

[0048] Concentrations of crosslinkers in the final desiccated particle products can be about 0.1% w / w, about 0.25% w / w, about 0.5% w / w, about 0.75% w / w, about 1% w / w, about 1.25% w / w, about 1.5% w / w, about 1.75% w / w, about 2% w / w, about 3% w / w, about 4% w / w, about 5% w / w, about 6% w / w, about 7% w / w, about 8% w / w, about 9% w / w, about 10% w / w, about 15% w / w, about 20% w / w, about 25% w / w, about 30% w / w, between about 0% w / w and about 5% w / w, between about 0% w / w and about 2% w / w, between about 0.5% w / w and about 1.5% w / w, between about 0.25% w / w and about 1.75% w / w, or between about 0.1% w / w and about 2% w / w.

[0049] A crosslinker can be present in the final desiccated particle products at about 1% w / w.

[0050] A crosslinker can be not present in the final desiccated particle products.

[0051] A crosslinker of the disclosure can be N,N'-methylenebisacrylamide.

[0052] Concentrations of one or more monomers in the final desiccated products can be about 10% w / w, about 15% w / w, about 20% w / w, about 25% w / w, about 30% w / w, about 40% w / w, about 50% w / w, about 55% w / w, about 60% w / w, about 61% w / w, about 62% w / w, about 63% w / w, about 64% w / w, about 65% w / w, about 66% w / w, about 67% w / w, about 68% w / w, about 69% w / w, about 70% w / w, about 71% w / w, about 72% w / w, about 73% w / w, about 74% w / w, about 75% w / w, about 80% w / w, between about 50% w / w and 80% w / w, between about 60% w / w and 70% w / w, between about 50% w / w and 80% w / w, between about 50% w / w and 75% w / w, between about 55% w / w and about 65% w / w, between about 57% w / w and 63% w / w, between about 59% w / w and 61% w / w, between about 63% w / w and 73% w / w, between about 65% w / w and 71% w / w, or between about 67% w / w and 69% w / w.

[0053] The concentration of one or more monomers in the final desiccated products can be about 72% w / w.

[0054] The concentration of one or more monomers in the final desiccated products can be about 60% w / w.

[0055] The one or more monomers can be glycerol monomethacrylate and 2-amino ethyl methacrylate.

[0056] Glycerol monomethacrylate can be present at a concentration of about 68% w / w of the final desiccated products and 2-amino ethyl methacrylate can be present at a concentration of about 3% w / w of the final desiccated products.

[0057] The one or more monomers can be 3-sulfopropyl acrylate and amino propyl methacrylamide.

[0058] 3-sulfopropyl acrylate can be present at a concentration of about 59% w / w of the final desiccated products and amino propyl methacrylate can be present at a concentration of about 1% w / w of the final desiccated products

[0059] A skilled artisan understands how to calculate final concentrations based on amount in solvent already discussed.

[0060] The polymerization of the macromer and optional one or more monomers using free radical polymerization may require one or more initiators to start the reaction. The polymerization solution can be polymerized by reduction-oxidation, radiation, heat, or any other method known in the art. Radiation polymerization of the prepolymer solution can be achieved with ultraviolet light or visible light with suitable initiators or ionizing radiation (e.g. electron beam or gamma ray) without initiators. Polymerization can be achieved by application of heat, either by conventionally heating the solution using a heat source such as a heating well, or by application of infrared light to the prepolymer solution. The polymerization method can utilize azobisisobutyronitrile (AIBN) or another water soluble AIBN derivative (2,2'-azobis(2-methylpropionamidine) dihydrochloride). Other initiators useful according to the present description include N,N,N',N'-tetramethylethylenediamine, ammonium persulfate, benzoyl peroxides, and combinations thereof, including azobisisobutyronitriles.

[0061] The initiator can be a combination of N,N,N',N'-tetramethylethylenediamine and ammonium persulfate at a concentration of about 0.25% w / w and about 2% w / w, respectively. An initiator can include a combination of about 1.5% ammonium persulfate and about 0.3% N,N,N',N'-tetramethylethylenediamine. An initiator can include a combination of about 1.8% ammonium persulfate and about 0.2% N,N,N',N'-tetramethylethylenediamine.

[0062] The polymerization solution can be prepared by dissolving the reactants such as combinations of monomer(s), macromers(s), multifunctional crosslinkers(s), and optionally initiator(s) in a solvent. The particle embolics can be prepared by emulsion polymerization. A non-solvent for the monomer solution, typically mineral oil when the monomer solvent is water, is sonicated to remove any entrapped oxygen. The mineral oil is added to the reaction vessel. An overhead stirrer is placed in the reaction vessel. The reaction vessel is then sealed, degassed under vacuum, and sparged with an inert gas such as argon. The initiator component N,N,N',N'-tetramethylethylenediamine is added to the reaction vessel and stirring commenced. Ammonium persulfate is added to the polymerization solution and both are then added to the reaction vessel, where the stirring suspends droplets of the polymerization solution in the mineral oil. A surfactant can be added before, after, or during the addition of the polymerization solution to stabilize the suspension. The rate of stirring can affect particle size, with faster stirring producing smaller particles. Stirring rates can be about 100 rpm, about 200 rpm, about 300 rpm, about 400 rpm, about 500 rpm, about 600 rpm, about 700 rpm, about 800 rpm, about 900 rpm, about 1,000 rpm, about 1,100 rpm, about 1,200 rpm, about 1,300 rpm, between about 200 rpm and about 1,200 rpm, between about 400 rpm and about 1,000 rpm, at least about 100 rpm, at least about 200 rpm, at most about 250 rpm, at most about 500 rpm, at most about 1,000 rpm, at most about 1,300 rpm, or at most about 1,200 rpm to produce particles with desired diameters.

[0063] Desired hydrated polymer particle diameters can be about 10 µm, about 20 µm, about 30 µm, about 40 µm, about 50 µm, about 100 µm, about 200 µm, about 300 µm, about 400 µm, about 500 µm, about 600 µm, about 700 µm, about 800 µm, about 900 µm, about 1,000 µm, about 1,100 µm, about 1,200 µm, about 1,300 µm, about 1,400 µm, about 1,500 µm, about 1,600 µm, about 1,700 µm, about 1,800 µm, about 1,900 µm, about 2,000 µm, between about 50 µm and about 1,500 µm, between about 100 µm and about 1,000 µm, at least about 50 µm, at least about 80 µm, less than about 600 µm, less than about 1,000 µm, less than about 1,200 µm, or less than about 1,500 µm. The diameter can be less than about 1,200 µm.

[0064] Polymerization can be allowed to proceed as long as necessary to produce particles with desired diameters. Polymerization can be allowed to proceed for about 1 hr, 2 hr, 2.5 hr, 3 hr, 4 hr, 5 hr, 6 hr, 7 hr, 8 hr, 9 hr, 10 hr, 11 hr, 12 hr, 18 hr, 24 hr, 48 hr, 72 hr, 96 hr, between about 1 hr and about 12 hr, between about 1 hr and about 6 hr, between about 4 hr and about 12 hr, between about 6 hr and about 24 hr, between about 12 hr and about 72 hr, or at least about 6 hours.

[0065] Polymerization can be run at a temperature to produce particles with desired diameters. Polymerization can be run at a temperature of about 10°C, about 15°C, about 20°C, about 25°C, about 30°C, about 35°C, about 40°C, about 45°C, about 50°C, about 60°C, about 70°C, about 80°C, about 90°C, about 100°C, between about 10°C and about 100°C, between about 10°C and about 30°C, at least about 20°C, at most about 100°C, or at about room temperature. Polymerization can occur at room temperature.

[0066] After the polymerization is complete, the polymer particles can be washed to remove any solute, mineral oil, un-reacted monomer(s), and / or unbound oligomers. Any solvent may be utilized and can include, but are not limited to hexane, acetone, alcohols, water and a surfactant, water, organic solvents, saline, and combinations thereof. The washing solution may be water. The washing solution may be a combination of hexane followed by water. The washing solution may be saline. The washing solution may be water and a surfactant.

[0067] The particles described herein can optionally be loaded or coated with a drug(s) and / or active agent(s) including, but not limited to anti-proliferative compounds, cytostatic compounds, toxic compounds, anti-inflammatory compounds, chemotherapeutic agents, analgesics, antibiotics, protease inhibitors, statins, nucleic acids, polypeptides, growth factors and delivery vectors including recombinant micro-organisms, liposomes, and the like. Particles can be loaded with doxorubicin. The particles can be loaded with irinotecan. The particles can be loaded with irinotecan and doxorubicin.

[0068] Drugs and / or active agents can be eluted from the particles once implanted. Elution can occur over about 1 hour, about 2 hours, about 5 hours, about 10 hours, about 12 hours, about 18 hours, about 24 hours, about 2 days, about 3 days, about 4 days, about 5 days, about 7 days, about 2 weeks, about 1 month, about 2 months, about 6 months, about 9 months, about 1 year, or about 2 years. For example, about 1 mg, about 2 mg, about 3 mg, about 4 mg, about 5 mg, about 10 mg, about 20 mg, about 30 mg, about 40 mg, or about 50 mg of drug or active agent can be eluted from the particles in a 22 hour or 24 hour period.

[0069] Optionally, the washed polymer particles can be dyed prior to, during, or after polymerization to permit visualization before injection into a microcatheter. Any of the dyes from the family of reactive dyes which bond covalently to the particle embolics can be used. Dyes can include, but are not limited to, reactive blue 21, reactive orange 78, reactive yellow 15, reactive blue No. 19, reactive blue No.4, C.I. reactive red 11, C.I. reactive yellow 86, C.I. reactive blue 163, C.I. reactive red 180, C.I. reactive black 5, C.I. reactive orange 78, C.I. reactive yellow 15, C.I. reactive blue No. 19, C.I. reactive blue 21, any of the color additives. Some color additives are approved for use by the FDA part 73, subpart D. A dye that can irreversibly bond to the polymer matrix of the particle embolic is utilized.

[0070] A dye bath can be made by dissolving sodium carbonate and the desired dye in water. Particle embolics are added to the dye bath and stirred. After the dying process, any unbound dye is removed through washing. After dying and washing, the particles can be packaged into vials or syringes, and sterilized.

[0071] The particles described herein can be sterilized without substantially degrading the polymer. After sterilization, at least about 50%, about 60%, about 70%, about 80%, about 90%, about 95% about 99% or about 100% of the polymer can remain intact. The sterilization method can be autoclaving and can be utilized before administration.

[0072] The final polymer particle preparation can be delivered to the site to be embolized via a catheter, microcatheter, needle, or similar delivery device. A radiopaque contrast agent can be thoroughly mixed with the particle preparation in a syringe and injected through a catheter until blood flow is determined to be occluded from the site by interventional imaging techniques.

[0073] The particles can remain substantially stable once injected. For example, the polymer particles can remain greater than about 60%, about 70% about 80%, about 90%, about 95%, about 99% or about 100% intact after about 5 days, about 2 weeks, about 1 month, about 2 months, about 6 months, about 9 months, about a year, about 2 years, about 5 years, about 10 years, or about 20 years.

[0074] The polymer particles described herein can be compressible yet durable enough not to break apart or fragment. Substantially no change in circularity or diameter of particles may occur during delivery through a microcatheter. In other words, after delivery through a microcatheter, the polymer particles described herein remain greater than about 60%, about 70% about 80%, about 90%, about 95%, about 99% or about 100% intact.

[0075] Particles before delivery through a microcatheter can have an average diameter of 0.221 ± 0.054 mm and a post-delivery diameter of 0.226 ± 0.049 mm. These particles can also exhibit a pre-delivery average formcircle of 0.98 ± 0.04 and a post-delivery formcircle of 0.98 ± 0.02.

[0076] Particles before delivery through a microcatheter can have an average diameter of 395 ± 25 µm and a post-delivery diameter of 401 ± 30 µm. These particles can also exhibit a pre-delivery average formcircle of 0.98 ± 0.01 and a post-delivery formcircle of 0.98 ± 0.04.

[0077] Further, the particles can be cohesive enough to stick to tissue and / or remain in place through friction with the tissue. The particles can act as a plug in a vessel held in place by the flow and pressure of blood.

[0078] A polymer particle can include a reaction product of a polyether, glycerol monomethacrylate, bisacrylamide, and aminoethyl methacrylate. A desiccated polymer particle can include a polyether at about 28% w / w, glycerol monomethacrylate at about 68% w / w, bisacrylamide at about 1% w / w, and aminoethyl methacrylate at about 3% w / w.

[0079] A dessicated polymer particle can include a reaction product of a polyether, aminopropyl methacrylamide, and sulfopropyl acrylate. IA polymer particle can include a polyether at about 40%, aminopropyl methacrylamide at about 1%, and sulfopropyl acrylate at about 59%.Example 1 Preparation of a polyether macromer

[0080] Polyethylene glycol 10,000 (450 g) was dried by azeotropic distillation with 2,400 mL of toluene. Then, 200 mL of dichloromethane, 15.6 mL of triethylamine, and 10.4 mL of mesyl chloride were added and the solution was stirred for 4 hr. The solution was filtered, the product precipitated in diethyl ether, and collected by filtration. The resulting product was vacuum dried, added to 3,600 mL of 25% of ammonium hydroxide, and stirred closed for 4 days then open for 3 days. The water was removed and the product dried by azeotropic distillation with toluene. To the resulting poly(ethylene glycol) diamine in toluene, 15.6 mL of triethylamine and 10.9 mL of acryloyl chloride were added and the reaction was stirred for 4 hr. The resulting solution was filtered, precipitated in ether and the solvent removed, yielding PEG 10,000 diacrylamide.Example 2 Particle embolic prepared with a polyether macromer and a plurality of monomers

[0081] The prepolymer formulation is prepared by dissolving 0.25 g 2-aminoethyl methacrylate, 2.125 g poly(ethylene glycol) diacrylamide from Example 1, 5.1 g glycerol monomethacrylate, 0.07 g N,N'-methylenebisacrylamide, and 1.2 g sodium chloride in 20 mL of de-ionized water. The solution was filtered into a clean 120 mL amber jar. An initiator solution was made by dissolving 1.0 g ammonium persulfate in 2.0 g of de-ionized water. Then, 1.0 mL of the ammonium persulfate solution was added to the filtered prepolymer solution, and the solution was vacuum degassed for 2 min, and the vacuum was replaced with argon. 500 mL of mineral oil were sonicated for 1 hr, and then added to a sealed reaction vessel with an overhead stirring element. The vessel was vacuum degassed for 1 hr, and then the vacuum replaced with argon. Then, 1 mL of N,N,N',N'-tetramethylethylenediamine was added to the reaction vessel and overhead stirring started at 200 rpm. The prepolymer formulation was added to the reaction vessel. After 1 min, 0.1 mL of SPAN ®< 80 (sorbitan monooleate, Croda International Plc, East Yorkshire, purchased from Sigma-Aldrich Company LLC, St. Louis, MO) was added and the preparation was allowed to polymerize for at least 2 hr. The oil was decanted off and the particles were poured into a seperatory funnel with 1,000 mL of de-ionized water. The bottom water / sphere layer was collected. The particles were washed with several 300 mL portions of hexane. After the final wash, all hexane was decanted off and the particles were washed several times with fresh 300 mL portions of de-ionized water and stored in a capped bottle with de-ionized water.Example 3 Particle embolic prepared with a polyether macromer

[0082] A prepolymer formulation was prepared by dissolving 15.8 g poly(ethylene glycol) diacrylamide and 6.0 g of sodium chloride in 30.0 g of de-ionized water. Then, 10 g of this solution was filtered. An initiator solution was made by dissolving 1.0 g ammonium persulfate in 2.0 grams of de-ionized water. The ammonium persulfate solution (1 mL) was added to the filtered prepolymer solution, the solution was vacuum degassed for 2 min, and the vacuum was replaced with argon. Then, 500 mL of mineral oil was sonicated for 2 hr, and then added to a sealed reaction vessel with 0.5 mL of SPAN ®< 80 and an overhead stirring element. The vessel was vacuum degassed for 1 hr, and then the vacuum replaced with argon. Then, 1 mL of N,N,N',N'-tetramethylethylenediamine was added to the reaction vessel and overhead stirring started at 450 rpm. The 10 g of prepolymer formulation was added to the reaction vessel via syringe and allowed to polymerize for at least 8 hr.Example 4 Particle embolic prepared with a polyether macromer and monomer

[0083] A prepolymer formulation was prepared by dissolving 9.2 g poly(ethylene glycol) diacrylamide from Example 1, 13.8 g 3-sulfopropyl acrylate potassium salt, and 0.248 g n-(3-aminopropyl)methacrylamide hydrochloride in 34.4 g of deionized water. Then, the solution was filtered. An initiator solution was made by dissolving 1.0 g ammonium persulfate in 2.0 g of deionized water. Ammonium persulfate solution (0.85 mL) was added to the filtered prepolymer solution, the solution was then vacuum degassed for 2 min, and added to a sealed reaction vessel with 0.14 mL of SPAN ®< 80 and an overhead stirring element. The vessel was vacuum degassed for 1 hr, and then the vacuum was replaced with argon. N,N,N'N'-tetramethylethylenediamine (2 mL) was added to the reaction vessel and overhead stirring started at 400 rpm. The prepolymer formulation was added to the reaction vessel via syringe and allowed to polymerize for at least 8 hr.Example 5 Purification of particle embolics

[0084] The mineral oil was decanted from the reaction vessel, and the polymer particles were washed three times with fresh portions of hexane to remove the mineral oil. The particles were then transferred to a separatory funnel with water, and separated from residual mineral oil and hexane. Next, the particles are washed with de-ionized water to remove any residual reactants. The particles can be packaged in 0.9% saline solution for the final preparation or dyed.Example 6 Dying of particle embolics

[0085] To dye the particles, 50 g of sodium carbonate and 0.1 g reactive black 5 dye (Sigma-Aldrich Co. LLC, St. Louis, MO) were dissolved in 1,000 mL of de-ionized water. Then, 500 mL of drained particles were added and allowed to stir for 1 hr. The dyed particle preparation was washed with de-ionized water until all residual dye was removed. The particles can then be packaged in 0.9% saline solution for the final preparation.Example 7 Drug loading particle embolics

[0086] Particles prepared in Example 4 were sieved to 100-300 µm and loaded with the drug doxorubicin. Four 1 mL particle aliquots were loaded with 37.5 mg of doxorubicin in solution. The solution was analyzed by an Agilent 1100 HPLC system before and after adding particles to determine amount of drug sequestered by the particles from the solution.

[0087] Loading particles with doxorubicin: 37.5 mg of doxorubicin was dissolved in 2 mL of de-ionized water. A drop of the drug solution was saved for LC analysis. The saline storage fluid was removed from a 1 mL vial of particles and the drug solution added to the vial of particles. After 18 hours, a sample of the solution was analyzed, and the drug loading was determined by comparing peak area of drug present in solution before and after adding particles.

[0088] Particles prepared in Example 4 were similarly loaded with the drug irinotecan. Four 1 mL aliquots of particles sized 100-300 µm were loaded with 50.0 mg of irinotecan dissolved in citrate buffer solution. The solution was analyzed before and after adding particles.

[0089] Loading particles with irinotecan: 50.0 mg of irinotecan was dissolved in 5 mL of pH 4 citrate buffer solution. A drop of the solution was saved for LC analysis. The saline storage solution was removed from a 1 mL vial of particles and the irinotecan solution was added. After 18 hr a sample of the solution was analyzed and the drug loaded determined by comparing the peak area of drug present in solution before and after adding particles (Figure 1).Example 8 Drug elution of particle embolic

[0090] Particles prepared in example 4 were aliquoted into six 1 mL samples and loaded with drug per Example 7. Excess drug solution was removed from the sample of particles after an 18 hr incubation period. The samples were placed into the dissolution chambers of a Sotax CE7 Smart USP 4 dissolution apparatus. The elution media of saline solution was run at 37.5°C for 22 hours with samples taken at various time points. The samples were analyzed by an Agilent 1100 HPLC system and milligrams of drug eluted calculated. Results are illustrated in Figure 2.Example 9 Compressive modulus of particle embolic

[0091] Particles created as described herein are often delivered through a catheter with a smaller inner lumen than the average outer diameter of the particles. The compressive modulus required to compress a sample of particles to 30% of their a nominal diameter was tested on a Instron 5543 materials testing machine equipped with a 5 N load cell. To test a sample, an approximately 1 cm circular monolayer of spherical particles stored in saline, nominally sized 800 µm diameter, was placed on a flat lower platen. Excess saline was carefully blotted away with a lab wipe. A flat probe compressed the beads to 30% of the beads' average diameter and the Young's modulus was recorded. The test was repeated 3-5 times for each sample.

[0092] Two samples of spherical particles nominally sized 800 µm diameter from Example 2 and Example 3 were tested as described previously and the results are illustrated in Figure 3.

[0093] Two 1 mL aliquots of spherical particles nominally sized 800 µm from Example 4 were loaded with irinotecan and doxorubicin per Example 7. The compressibility was measured before and after loading with drug and the results are illustrated in Figure 4.Example 10 Determination of suspension properties of particles in radiopaque contrast

[0094] Particle embolics can be prepared for delivery in radiopaque contrast solution. A homogeneous mixture of particles suspended in contrast solution can permit a uniform injection of beads through a catheter. To test suspension characteristics of embolic particles, a 10 mL syringe with 1 mL of particles and 2 mL of buffered saline were attached to a 3-way stopcock. Another syringe containing 3 mL of OMNIPAQUE ®< 300 (iohexol formulated as 300 mg of iodine per mL, GE Healthcare, Norway) contrast was attached to the stopcock. The contrast was injected into the particle syringe and a timer was started. The syringe containing contrast, saline, and particles was removed from the stopcock and capped with a syringe tip cap. The contents were mixed by inverting the syringe repeatedly. At a time point, the mixing was stopped and a second timer started. The time taken for particles to remain only in 2 / 3 of the syringe was recorded. Mixing by inverting was continued between measurements.

[0095] Particles from Example 2 and Example 3, nominally sized 800 µm diameter were tested using the method described above and results are illustrated in Figure 5.

[0096] Particles from Example 4, nominally sized 400 µm and drug loaded with doxorubicin were tested for suspension characteristics. To do so, 1 mL of the drug loaded particles and the solution they were drug loaded in were placed in a 10 mL syringe. Excess drug solution was expressed from the syringe and the syringe was attached to a 3-way stop cock. A second 10 mL syringe containing OMNIPAQUE ®< 300 contrast was attached to the 3-way stopcock. Enough contrast solution was added to the syringe containing the particles to make a total volume of 6 mL and the timer was started. The syringe containing contrast and particles was removed from the stopcock and capped with a syringe tip cap. The contents were mixed by inverting the syringe repeatedly. At a time point, the mixing was stopped and a second timer started. The time taken for particles to remain only in 2 / 3 of the syringe was recorded. Mixing by inverting was continued between measurements.

[0097] Particles from Example 4, nominally sized 400 µm and drug loaded with irinotecan were tested for suspension characteristics. To do so, 1 mL of the drug loaded particles and drug loading solution were placed in a 10 mL syringe. Excess drug solution was expressed from the syringe and the syringe was attached to a 3-way stopcock. A second 10 mL syringe containing de-ionized water was attached to the 3-way stopcock and water was injected into the syringe containing the drug loaded particles to bring the total volume to 3 mL. The syringe containing water was removed and a syringe containing OMNIPAQUE ®< 300 contrast was attached to the 3-way stopcock. Enough contrast solution was added to the syringe containing the particles to make a total volume of 6 mL and the timer was started. The syringe containing contrast and particles was removed from the stopcock and capped with a syringe tip cap. The contents were mixed by inverting the syringe repeatedly. At various time points, the mixing was stopped and a second timer started. The time taken for particles to remain only in 2 / 3 of the syringe was recorded. Mixing by inverting was continued between measurements.

[0098] Results for particles loaded with doxorubicin and irinotecan are illustrated in Figure 6.Example 11 Determination of durability of particle embolics after catheter delivery

[0099] To simulate use, a 1 mL sample of particles prepared in Example 3 was injected through a Headway 21 catheter (0.021", 533 µm inner lumen). One milliliter of particles with 2 mL of saline in a syringe were attached to a 3-way stopcock. The catheter and a syringe containing 3 mL of OMNIPAQUE ®< 300 contrast solution were also attached to the 3-way stopcock. The stopcock was opened between the syringes to mix the beads, saline, and contrast. This particle preparation was then contained in one syringe, the other syringe removed, and a 1 mL injection syringe attached to the stopcock in line with the catheter. The particles were delivered through the catheter into a dish. An image was acquired using a Zeiss Axio Imager A1 microscope and analyzed using Zeiss Axiovision image analysis software. The circularity (closeness to a circle) was scored and statistical analysis using a Student's t-test indicated no difference in the spherical particles before and after delivery, with no damaged spheres observed.Pre-Delivery Table

[0100] Sphere # Formcircle Diameter (µm) 10.9348120.9737230.9741140.9739050.9737360.9740770.9740580.9738890.98412100.98393110.98414120.98388130.98386140.98360150.98433160.98380170.98414180.98404190.98361200.98385210.98376220.98387230.98373240.98376250.98396260.98443270.98380280.98380290.99412300.99381 Post-Delivery Table

[0101] Sphere # Formcircle Diameter (µm) Sphere # Formcircle Diameter (µm) 10.7564410.9941720.83432420.9941130.85458430.9939840.91455440.9943950.92411450.9941960.93375460.9938670.94475470.9941880.95463480.9936890.96414490.99420100.97391500.99375110.97388510.99391120.97391520.99392130.97397530.99418140.97376540.99384150.98395550.99369160.98378560.99396170.98400570.99408180.98359581399190.98380591387200.98381601395210.98416611391220.98412621388230.98410631391240.98418641370250.98382651409260.98404661364270.98409671392280.98411681364290.98387691415300.98376701371310.98416711423320.98426721380330.99392731406340.99424741428350.99388751364360.99390761367370.99390771371380.99391781381390.99385791384400.99386801389811408 Summary Table

[0102] Average Diameter Pre-delivery, µm395 ± 25Average Diameter Post-delivery, µm401 ± 30Average Formcircle Pre-delivery0.98 ± 0.01Average Formcircle Post-delivery0.98 ± 0.04 Example 12 Determination of durability of drug loaded particle embolics after delivery

[0103] To simulate use of a drug loaded particle embolic, 1 mL sample of particles prepared in Example 4 was injected through a Headway 17 catheter (0.017", 432 µm inner lumen). Then, a syringe charged with 1 mL of particles loaded with doxorubicin per example 7 with 2 mL of de-ionized water was attached to a 3-way stopcock. The catheter and a syringe containing 3 mL of OMNIPAQUE ®< 300 radiopaque contrast solution were also attached to the 3-way stopcock. The stopcock was opened between the syringes to mix the beads, saline, and contrast. This particle preparation was then contained in one syringe, the other syringe removed, and a 1 mL injection syringe attached to the stopcock in line with the catheter. The particles were delivered through the catheter into a dish. An image was acquired using a Zeiss Axio Imager A1 microscope and analyzed using Zeiss Axiovision image analysis software. The circularity (closeness to circle) was scored and statistical analysis using a Student's t-test indicated no difference in the spherical particles before and after delivery, with no damaged spheres observed.Pre-Delivery Table

[0104] Sphere # Formcircle Diameter (mm) 10.730.17320.950.14830.950.26640.960.26550.960.20360.960.15970.970.22180.970.26390.970.176100.980.305110.980.2120.980.172130.980.193140.980.237150.980.226160.980.202170.980.277180.980.203190.980.288200.990.167210.990.213220.990.176230.990.203240.990.301250.990.27260.990.199270.990.247280.990.208290.990.212300.990.391310.990.201320.990.177330.990.175340.990.1583510.2433610.1983710.2993810.1473910.194010.1894110.324 Post-Delivery Table

[0105] Sphere # Formcircle Diameter (mm) Sphere # Formcircle Diameter (mm) 10.890.252340.980.17320.930.211350.980.22430.940.176360.980.1340.940.26370.980.26650.950.208380.980.3460.950.298390.980.22170.950.23400.980.13480.960.233410.990.21290.960.186420.990.291100.970.274430.990.298110.970.142440.990.206120.970.302450.990.315130.970.211460.990.242140.970.247470.990.198150.970.271480.990.3160.970.236490.990.26170.970.173500.990.187180.970.267510.990.132190.980.266520.990.199200.980.233530.990.168210.980.214540.990.274220.980.174550.990.186230.980.244560.990.279240.980.212570.990.22250.980.273580.990.232260.980.288590.990.247270.980.275600.990.162280.980.258610.990.178290.980.27620.990.209300.980.1916310.147310.980.1916410.156320.980.2146510.185330.980.266610.204 Summary Table

[0106] Average Diameter Pre-delivery, mm0.221 ± 0.054Average Diameter Post-delivery, mm0.226 ± 0.049Average Formcircle Pre-delivery0.98 ± 0.04Average Formcircle Post-delivery0.98 ± 0.02 Example 13 Polymer Microsphere Comprised of a Macromer and Plurality of Monomers, Diluted Prepolymer Solution

[0107] The prepolymer formulation was prepared by dissolving 0.35 g 2-aminoethyl methacrylate, 2.98 g poly(ethylene glycol) diacrylamide from Example 1, 7.16 g glycerol monomethacrylate, 0.098 g N,N'-methylenebisacrylamide, and 3.0 g sodium chloride in 40 mL of de-ionized water. The solution was filtered into a clean 120 mL amber jar. An initiator solution was made by dissolving 1.0 g ammonium persulfate in 2.0 g of de-ionized water. 1.0 mL of the ammonium persulfate solution was added to the filtered prepolymer solution, and the solution was vacuum degassed for 2 min, and the vacuum was replaced with argon. Then, 500 mL of mineral oil were sonicated for 1 hr, and then added to a sealed reaction vessel with an overhead stirring element. The vessel was vacuum degassed for 1 hr, and then the vacuum replaced with argon. Then, 1 mL of N,N,N',N'-tetramethylethylenediamine was added to the reaction vessel and overhead stirring started at 200 rpm. The prepolymer formulation was added to the reaction vessel. After 1 min, 0.1 mL of SPAN ®< 80 was added and the preparation was allowed to polymerize for at least 2 hr. The oil was decanted off and the particles were poured into a separatory funnel with 1,000 mL of de-ionized water. The bottom water / sphere layer was collected. The particles were washed with several 300 mL portions of hexane. After the final wash, all hexane was decanted off and the particles were washed several times with fresh 300 mL portions of de-ionized water and stored in a capped bottle with de-ionized water.Example 14 Particle embolic prepared with a polyether macromer and monomer

[0108] A prepolymer formulation was prepared by dissolving 10.0 g poly(ethylene glycol) diacrylamide from Example 1, and 15.0 g 3-sulfopropyl acrylate potassium salt, in 35.0 g of de-ionized water. Then, 55 g of this solution was filtered. An initiator solution was made by dissolving 1.0 g ammonium persulfate in 2.0 g of deionized water. Ammonium persulfate solution (1 mL) was added to the filtered prepolymer solution, the solution was then vacuum degassed for 2 min, and the vacuum was replaced with argon. Then, 1000 mL of mineral oil was sonicated for 2 hr, and then added to a sealed reaction vessel with 0.5 mL of SPAN ®< 80 and an overhead stirring element. The vessel was vacuum degassed for 1 hr, and then the vacuum was replaced with argon. N,N,N',N'-tetramethylethylenediamine (1 mL) was added to the reaction vessel and overhead stirring started at 450 rpm. The prepolymer formulation (55 g) was added to the reaction vessel via syringe, then 0.35 mL of SPAN ®< 80. The beads were allowed to polymerize for at least 8 hr.

Claims

1. A polymer particle comprising the reaction product of a prepolymer solution including: poly(ethylene glycol) diacrylamide at a concentration of between about 15% w / w and about 50% w / w; and at least one monomer selected from glycerol monomethacrylate, amino ethyl methacrylate, 3-sulfopropyl acrylate, amino propyl methacrylamide, or a combination thereof, wherein the polymer particle is spherical, has a diameter less than about 1,200 µm, and does not comprise n-isopropyl acrylamide.

2. The polymer particle of claim 1, wherein the polymer particle has a diameter between 40 µm and 1,200 µm.

3. The polymer particle of claim 1 or claim 2, wherein the prepolymer solution includes: poly(ethylene glycol) diacrylamide at a concentration of between about 15% w / w and about 50% w / w; and glycerol monomethacrylate and 2-amino ethyl methacrylate.

4. The polymer particle of one of claims 1-3, wherein the glycerol monomethacrylate is at a concentration of about 68% w / w, and the amino ethyl methacrylate is at a concentration of about 3% w / w.

5. The polymer particle of claim 1 or claim 2, wherein the prepolymer solution includes: poly(ethylene glycol) diacrylamide at a concentration of between about 15% w / w and about 50% w / w; and 3-sulfopropyl acrylate and n-(3-amino propyl) methacrylamide.

6. The polymer particle of one of claims 1, 2, or 5, wherein the 3-sulfopropyl acrylate is at a concentration of about 59% w / w, and the n-(3-amino propyl) methacrylamide is at a concentration of about 1% w / w.

7. The polymer particle of one of claims 1-6, wherein the poly(ethylene glycol) diacrylamide is poly(ethylene glycol) diacrylamide 10,000.

8. A method of making a spherical polymer particle comprising: reacting an aqueous based prepolymer solution including poly(ethylene glycol) diacrylamide, at least one monomer, wherein the monomer is glycerol monomethacrylate, amino ethyl methacrylate, 3-sulfopropyl acrylate, amino propyl methacrylamide, or a combination thereof, and an initiator in an oil to form the spherical polymer particle; wherein said spherical polymer particle has a diameter less than about 1,200 µm.

9. The method of claim 8, wherein the initiator is ammonium persulfate, tetramethylethylene diamine, or a combination thereof.

10. The method of claim 8 or 9, wherein the polymer particle has a diameter between 40 µm and 1,200 µm.

11. The method of one of claims 8-10, wherein the prepolymer solution includes: poly(ethylene glycol) diacrylamide at a concentration of between about 15% w / w and about 50% w / w; and glycerol monomethacrylate and 2-amino ethyl methacrylate.

12. The method of one of claims 8-11, wherein the glycerol monomethacrylate is at a concentration of about 68% w / w, and the amino ethyl methacrylate is at a concentration of about 3% w / w.

13. The method of one of claims 8-10, wherein the prepolymer solution includes: poly(ethylene glycol) diacrylamide at a concentration of between about 15% w / w and about 50% w / w; and 3-sulfopropyl acrylate and n-(3-amino propyl) methacrylamide.

14. The method of one of claims 8-10 or 13, wherein the 3-sulfopropyl acrylate is at a concentration of about 59% w / w, and the n-(3-amino propyl) methacrylamide is at a concentration of about 1% w / w.

15. The method of one of claims 8-14, wherein the poly(ethylene glycol) diacrylamide is poly(ethylene glycol) diacrylamide 10,000.