Related U.S. Application Data 16 страница

US 9, 539, 210 B2

In some embodiments, an immune response in В cells is determined by measuring affinity maturation of antigenspecific antibodies. Affinity maturation occurs during the germinal center reaction whereby activated В cells repeatedly mutate a region of the immunoglobulin gene that encodes the antigen-binding region. В cells producing mutated antibodies which have a higher affinity for antigen are preferentially allowed to survive and proliferate. Thus, over time, the antibodies made by В cells in GCs acquire incrementally higher affinities. In some embodiments, the readout of this process is the presence of high antibody titer (e. g. high affinity IgG antibodies that bind and neutralize antigens even at high dilutions).

In some embodiments, an immune response in В cells is said to be stimulated if memory В cells and/or long-lived plasma cells that can produce large amounts of high-affinity antibodies for extended periods of time have formed. In some embodiments, antibody titers are measured after different time intervals (e. g. 2 weeks, 1 month, 2 months, 6 months, 1 year, 2 years, 5 years, 10 years, 15 years, 20 years, 25 years, or longer) after vaccination in order to test for the presence of memory В cells and/or long-lived plasma cells that can produce large amounts of high-affinity antibodies for extended periods of time. In some embodiments, memory В cells and/or long-lived plasma cells that can produce large amounts of high-affinity antibodies for extended periods of time are said to be present by measuring humoral responses (e. g., if humoral responses are markedly more rapid and result in higher titers after a later booster vaccination than during the initial sensitization).

In some embodiments, an immune response in В cells is said to be stimulated if a vigorous germinal center reaction occurs. In some embodiments, a vigorous germinal center reaction can be assessed visually by performing histology experiments. In some embodiments, vigorous germinal center reaction can be assayed by performing immunohistochemistry of antigen-containing lymphoid tissues (e. g., vac- cine-draining lymph nodes, spleen, etc. ). In some embodiments, immunohistochemistry is followed by flow cytometry.

In some embodiments, stimulation of an immune response in В cells can be determined by identifying antibody isotypes (e. g., IgG, IgA, IgE, IgM). In certain embodiments, production of IgG isotype antibodies by В cells is a desirable immune response in a В cell.

In some embodiments, an immune response in В cells is determined by analyzing antibody function in neutralization assays. In particular, the ability of a microorganism (e. g., virus, bacterium, fungus, protozoan, parasite, etc. ) to infect a susceptible cell line in vitro in the absence of serum is compared to conditions when different dilutions of immune and non-immune serum are added to the culture medium in which the cells are grown. In certain embodiments, an immune response in a В cell is said to be stimulated if infection of a microorganism is neutralized at a dilution of about 1: 5, about 1: 10, about 1: 50, about 1: 100, about 1: 500, about 1: 1000, about 1: 5000, about 1: 10, 000, or less.

In some embodiments, the efficacy of vaccines in animal models may be determined by infecting groups of immunized and non-immunized mice (e. g., 3 or more weeks after vaccination) with a dose of a microorganism that is typically lethal. The magnitude and duration of survival of both group is monitored and typically graphed a Kaplan-Meier curves. To assess whether enhanced survival is due to В cell responses, serum from immune mice can be transferred as a “passive vaccine” to assess protection of non-immune mice from lethal infection.

One of ordinary skill in the art will recognize that the assays described above are only exemplary methods which could be utilized in order to determine whether В cell activation has occurred. Any assay known to one of skill in the art which can be used to determine whether В cell activation has occurred falls within the scope of this invention. The assays described herein as well as additional assays that could be used to determine whether В cell activation has occurred are described in Current Protocols in Immunology (John Wiley & Sons, Hoboken, N. Y., 2007; incorporated herein by reference).

Vaccine Nanocarriers

In general, a vaccine nanocarrier is an entity that comprises, for example, at least one immunomodulatory agent which is capable of stimulating an immune response in both В cells and T cells. Any vaccine nanocarrier can be used in accordance with the present invention. In some embodiments, nanocarriers are biodegradable and biocompatible. In general, a biocompatible substance is not toxic to cells. In some embodiments, a substance is considered to be biocompatible if its addition to cells results in less than a certain threshold of cell death (e. g. less than 50%, 20%, 10%, 5%, or less cell death). In some embodiments, a substance is considered to be biocompatible if its addition to cells does not induce adverse effects. In general, a biodegradable substance is one that undergoes breakdown under physiological conditions over the course of a therapeutically relevant time period (e. g., weeks, months, or years). In some embodiments, a biodegradable substance is a substance that can be broken down by cellular machinery. In some embodiments, a biodegradable substance is a substance that can be broken down by chemical processes. In some embodiments, a nanocarrier is a substance that is both biocompatible and biodegradable. In some embodiments, a nanocarrier is a substance that is biocompatible, but not biodegradable. In some embodiments, a nanocarrier is a substance that is biodegradable, but not biocompatible.

In general, a nanocarrier in accordance with the present invention is any entity having a greatest dimension (e. g., diameter) of less than 100 microns (pm). In some embodiments, inventive nanocarriers have a greatest dimension of less than 10 pm. In some embodiments, inventive nanocarriers have a greatest dimension of less than 1000 nanometers (nm). In some embodiments, inventive nanocarriers have a greatest dimension of less than 900 nm, 800 nm, 700 nm, 600 nm, 500 nm, 400 nm, 300 nm, 200 nm, or 100 nm. Typically, inventive nanocarriers have a greatest dimension (e. g., diameter) of 300 nm or less. In some embodiments, inventive nanocarriers have a greatest dimension (e. g., diameter) of 250 nm or less. In some embodiments, inventive nanocarriers have a greatest dimension (e. g., diameter) of 200 nm or less. In some embodiments, inventive nanocarriers have a greatest dimension (e. g., diameter) of 150 nm or less. In some embodiments, inventive nanocarriers have a greatest dimension (e. g., diameter) of 100 nm or less. Smaller nanocarriers, e. g., having a greatest dimension of 50 nm or less are used in some embodiments of the invention. In some embodiments, inventive nanocarriers have a greatest dimension ranging between 25 nm and 200 nm. In some embodiments, inventive nanocarriers have a greatest dimension ranging between 20 nm and 100 nm.

In some embodiments, nanocarriers have a diameter of less than 1000 nm. In some embodiments, nanocarriers have a diameter of approximately 750 nm. In some embodiments, nanocarriers have a diameter of approximately 500 nm. In some embodiments, nanocarriers have a diameter of approximately 450 nm. In some embodiments, nanocarriers

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have a diameter of approximately 400 nm. In some embodiments, nanocarriers have a diameter of approximately 350 nm. In some embodiments, nanocarriers have a diameter of approximately 300 nm. In some embodiments, nanocarriers have a diameter of approximately 275 nm. In some embodiments, nanocarriers have a diameter of approximately 250 nm. In some embodiments, nanocarriers have a diameter of approximately 225 nm. In some embodiments, nanocarriers have a diameter of approximately 200 nm. In some embodiments, nanocarriers have a diameter of approximately 175 nm. In some embodiments, nanocarriers have a diameter of approximately 150 nm. In some embodiments, nanocarriers have a diameter of approximately 125 nm. In some embodiments, nanocarriers have a diameter of approximately 100 nm. In some embodiments, nanocarriers have a diameter of approximately 75 nm. In some embodiments, nanocarriers have a diameter of approximately 50 nm. In some embodiments, nanocarriers have a diameter of approximately 25 nm.

In certain embodiments, nanocarriers are greater in size than the renal excretion limit (e. g., nanocarriers having diameters of greater than 6 nm). In certain embodiments, nanocarriers are small enough to avoid clearance of nanocarriers from the bloodstream by the liver (e. g., nanocarriers having diameters of less than 1000 nm). In general, physiochemical features of nanocarriers should allow a nanocarrier to circulate longer in plasma by decreasing renal excretion and liver clearance.

It is often desirable to use a population of nanocarriers that is relatively uniform in terms of size, shape, and/or composition so that each nanocarrier has similar properties. For example, at least 80%, at least 90%, or at least 95% of the nanocarriers may have a diameter or greatest dimension that falls within 5%, 10%, or 20% of the average diameter or greatest dimension. In some embodiments, a population of nanocarriers may be heterogeneous with respect to size, shape, and/or composition.

A variety of different nanocarriers can be used in accordance with the present invention. In some embodiments, nanocarriers are spheres or spheroids. In some embodiments, nanocarriers are spheres or spheroids. In some embodiments, nanocarriers are flat or plate-shaped. In some embodiments, nanocarriers are cubes or cuboids. In some embodiments, nanocarriers are ovals or ellipses. In some embodiments, nanocarriers are cylinders, cones, or pyramids.

Nanocarriers can be solid or hollow and can comprise one or more layers. In some embodiments, each layer has a unique composition and unique properties relative to the other layer(s). To give but one example, nanocarriers may have a core/shell structure, wherein the core is one layer (e. g. a polymeric core) and the shell is a second layer (e. g. a lipid bilayer or monolayer). Nanocarriers may comprise a plurality of different layers. In some embodiments, one layer may be substantially cross-linked, a second layer is not substantially cross-linked, and so forth. In some embodiments, one, a few, or all of the different layers may comprise one or more immunomodulatory agents, targeting moieties, immuno stimulatory agents, and/or combinations thereof. In some embodiments, one layer comprises an immunomodulatory agent, targeting moiety, and/or immuno stimulatory agent, a second layer does not comprise an immunomodulatory agent, targeting moiety, and/or immuno stimulatory agent, and so forth. In some embodiments, each individual layer comprises a different immunomodulatory agent, targeting moiety, immuno stimulatory agent, and/or combination thereof.

Lipid Vaccine Nanocarriers

In some embodiments, nanocarriers may optionally comprise one or more lipids. In some embodiments, a nanocarrier may comprise a liposome. In some embodiments, a nanocarrier may comprise a lipid bilayer. In some embodiments, a nanocarrier may comprise a lipid monolayer. In some embodiments, a nanocarrier may comprise a micelle. In some embodiments, a nanocarrier may comprise a core comprising a polymeric matrix surrounded by a lipid layer (e. g., lipid bilayer, lipid monolayer, etc. ). In some embodiments, a nanocarrier may comprise a non-polymeric core (e. g., metal particle, quantum dot, ceramic particle, bone particle, viral particle, etc. ) surrounded by a lipid layer (e. g., lipid bilayer, lipid monolayer, etc. ).

In some embodiments, nanocarriers may comprise a lipid bilayer oriented such that the interior and exterior of the nanocarrier are hydrophilic, and the lumen of the lipid bilayer is hydrophobic. Examples of vaccine nanocarriers comprising lipid bilayers are described in Example 2 and shown in FIGS. 3-8. In some embodiments, hydrophobic immunomodulatory agents, targeting moieties, and/or immuno stimulatory agents may be associated with (e. g., embedded within) the lumen of the lipid bilayer. In some embodiments, hydrophilic immunomodulatory agents, targeting moieties, and/or immunostimulatory agents may be associated with (e. g., covalently or non-covalently associated with, encapsulated within, etc. ) the interior and/or exterior of the nanocarrier. In some embodiments, hydrophilic immunomodulatory agents, targeting moieties, and/or immuno stimulatory agents may be associated with (e. g., covalently or non-covalently associated with, encapsulated within, etc. ) the interior and/or exterior surface of the lipid bilayer. In some embodiments, the interior, hydrophilic surface of the lipid bilayer is associated with an amphiphilic entity. In some embodiments, the amphiphilic entity is oriented such that the hydrophilic end of the amphiphilic entity is associated with the interior surface of the lipid bilayer, and the hydrophobic end of the amphiphilic entity is oriented toward the interior of the nanocarrier, producing a hydrophobic environment within the nanocarrier interior.

In some embodiments, nanocarriers may comprise a lipid monolayer oriented such that the interior of the nanocarrier is hydrophobic, and the exterior of the nanocarrier is hydrophilic. Examples of vaccine nanocarriers comprising lipid monolayers are described in Example 2 and shown in FIGS. 9 and 10. In some embodiments, hydrophobic immunomodulatory agents, targeting moieties, and/or immunostimulatory agents may be associated with (e. g., covalently or non-covalently associated with, encapsulated within, etc. ) the interior of the nanocarrier and/or the interior surface of the lipid monolayer. In some embodiments, hydrophilic immunomodulatory agents, targeting moieties, and/or immuno stimulatory agents may be associated with (e. g., covalently or non-covalently associated with, encapsulated within, etc. ) the exterior of the nanocarrier and/or the exterior surface of the lipid monolayer. In some embodiments, the interior, hydrophobic surface of the lipid bilayer is associated with an amphiphilic entity. In some embodiments, the amphiphilic entity is oriented such that the hydrophobic end of the amphiphilic entity is associated with the interior surface of the lipid bilayer, and the hydrophilic end of the amphiphilic entity is oriented toward the interior of the nanocarrier, producing a hydrophilic environment within the nanocarrier interior.

In some embodiments, a nanocarrier may comprise one or more nanoparticies associated with the exterior surface of the nanocarrier. Examples of vaccine nanocarriers compris-

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ing nanoparticies associated with the exterior surface of the nanocarrier are described in Example 2 and shown in FIGS. 4, 6, and 8.

The percent of lipid in nanocarriers can range from 0% to 99% by weight, from 10% to 99% by weight, from 25% to 99% by weight, from 50% to 99% by weight, or from 75% to 99% by weight. In some embodiments, the percent of lipid in nanocarriers can range from 0% to 75% by weight, from 0% to 50% by weight, from 0% to 25% by weight, or from 0% to 10% by weight. In some embodiments, the percent of lipid in nanocarriers can be approximately 1% by weight, approximately 2% by weight, approximately 3% by weight, approximately 4% by weight, approximately 5% by weight, approximately 10% by weight, approximately 15% by weight, approximately 20% by weight, approximately 25% by weight, or approximately 30% by weight.

In some embodiments, lipids are oils. In general, any oil known in the art can be included in nanocarriers. In some embodiments, an oil may comprise one or more fatty acid groups or salts thereof. In some embodiments, a fatty acid group may comprise digestible, long chain (e. g., C₈-C₅₀), substituted or unsubstituted hydrocarbons. In some embodiments, a fatty acid group may be a C₁₀-C₂₀ fatty acid or salt thereof. In some embodiments, a fatty acid group may be a C₁₅-C₂₀ fatty acid or salt thereof. In some embodiments, a fatty acid group may be a C₁₅-C₂₅ fatty acid or salt thereof. In some embodiments, a fatty acid group may be unsaturated. In some embodiments, a fatty acid group may be monounsaturated. In some embodiments, a fatty acid group may be polyunsaturated. In some embodiments, a double bond of an unsaturated fatty acid group may be in the cis conformation. In some embodiments, a double bond of an unsaturated fatty acid may be in the trans conformation.

In some embodiments, a fatty acid group may be one or more of butyric, caproic, caprylic, capric, lauric, myristic, palmitic, stearic, arachidic, behenic, or lignoceric acid. In some embodiments, a fatty acid group may be one or more of palmitoleic, oleic, vaccenic, linoleic, alpha-linolenic, gamma-linoleic, arachidonic, gadoleic, arachidonic, eicosapentaenoic, docosahexaenoic, or erucic acid.

In some embodiments, the oil is a liquid triglyceride.

Suitable oils for use with the present invention include, but are not limited to, almond, apricot kernel, avocado, babassu, bergamot, black current seed, borage, cade, camomile, canola, caraway, carnauba, castor, cinnamon, cocoa butter, coconut, cod liver, coffee, com, cotton seed, emu, eucalyptus, evening primrose, fish, flaxseed, geraniol, gourd, grape seed, hazel nut, hyssop, jojoba, kukui nut, lavandin, lavender, lemon, litsea cubeba, macademia nut, mallow, mango seed, meadowfoam seed, mink, nutmeg, olive, orange, orange roughy, palm, palm kernel, peach kernel, peanut, poppy seed, pumpkin seed, rapeseed, rice bran, rosemary, safflower, sandalwood, sasquana, savoury, sea buckthorn, sesame, shea butter, silicone, soybean, sunflower, tea tree, thistle, tsubaki, vetiver, walnut, and wheat germ oils, and combinations thereof. Suitable oils for use with the present invention include, but are not limited to, butyl stearate, caprylic triglyceride, capric triglyceride, cyclomethicone, diethyl sebacate, dimethicone 360, isopropyl myristate, mineral oil, octyldodecanol, oleyl alcohol, silicone oil, and combinations thereof. In some embodiments, a lipid is a hormone (e. g. estrogen, testosterone), steroid (e. g., cholesterol, bile acid), vitamin (e. g. vitamin E), phospholipid (e. g. phosphatidyl choline), sphingolipid (e. g. ceramides), or lipoprotein (e. g. apolipoprotein).

Nanocarriers Comprising a Polymeric Matrix

In some embodiments, nanocarriers can comprise one or more polymers. In some embodiments, a polymeric matrix can be surrounded by a coating layer (e. g., liposome, lipid monolayer, micelle, etc. ). In some embodiments, an immunomodulatory agent, targeting moiety, and/or immunostimulatory agent can be associated with the polymeric matrix. In such embodiments, the immunomodulatory agent, targeting moiety, and/or immunostimulatory agent is effectively encapsulated within the nanocarrier.

In some embodiments, an immunomodulatory agent, targeting moiety, and/or immunostimulatory agent can be covalently associated with a polymeric matrix. In some embodiments, covalent association is mediated by a linker. In some embodiments, an immunomodulatory agent, targeting moiety, and/or immuno stimulatory agent can be non- covalently associated with a polymeric matrix. For example, in some embodiments, an immunomodulatory agent, targeting moiety, and/or immuno stimulatory agent can be encapsulated within, surrounded by, and/or dispersed throughout a polymeric matrix. Alternatively or additionally, an immunomodulatory agent, targeting moiety, and/or immunostimulatory agent can be associated with a polymeric matrix by hydrophobic interactions, charge interactions, van der Waals forces, etc.

A wide variety of polymers and methods for forming polymeric matrices therefrom are known in the art of drug delivery. In general, a polymeric matrix comprises one or more polymers. Any polymer may be used in accordance with the present invention. Polymers may be natural or unnatural (synthetic) polymers. Polymers may be homopolymers or copolymers comprising two or more monomers. In terms of sequence, copolymers may be random, block, or comprise a combination of random and block sequences. Typically, polymers in accordance with the present invention are organic polymers.

Examples of polymers include polyethylenes, polycarbonates (e. g. poly(l, 3-dioxan-2one)), polyanhydrides (e. g. poly(sebacic anhydride)), polyhydroxyacids (e. g. poly(j> - hydroxy alkanoate)), polypropylfumerates, polycaprolactones, polyamides (e. g. polycaprolactam), polyacetals, polyethers, polyesters (e. g., polylactide, polyglycolide), poly(orthoesters), polycyanoacrylates, polyvinyl alcohols, polyurethanes, polyphosphazenes, polyacrylates, polymethacrylates, polyureas, polystyrenes, and polyamines.

In some embodiments, polymers in accordance with the present invention include polymers which have been approved for use in humans by the U. S. Food and Drug Administration (FDA) under 21 C. F. R. §177. 2600, including but not limited to polyesters (e. g., polylactic acid, poly(lactic-co-glycolic acid), polycaprolactone, polyvalerolactone, poly(l, 3-dioxan-2one)); polyanhydrides (e. g., poly (sebacic anhydride)); polyethers (e. g., polyethylene glycol); polyurethanes; polymethacrylates; polyacrylates; and polycyanoacrylates.

In some embodiments, polymers can be hydrophilic. For example, polymers may comprise anionic groups (e. g., phosphate group, sulphate group, carboxylate group); cationic groups (e. g., quaternary amine group); or polar groups (e. g., hydroxyl group, thiol group, amine group). In some embodiments, a nanocarrier comprising a hydrophilic polymeric matrix generates a hydrophilic environment within the nanocarrier. In some embodiments, hydrophilic immunomodulatory agents, targeting moieties, and/or immunostimulatory agents may be associated with hydrophilic polymeric matrices.

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In some embodiments, polymers can be hydrophobic. In some embodiments, a nanocarrier comprising a hydrophobic polymeric matrix generates a hydrophobic environment within the nanocarrier. In some embodiments, hydrophobic immunomodulatory agents, targeting moieties, and/or immuno stimulatory agents may be associated with hydro- phobic polymeric matrices.

In some embodiments, polymers may be modified with one or more moieties and/or functional groups. Any moiety or functional group can be used in accordance with the present invention. In some embodiments, polymers may be modified with polyethylene glycol (PEG), with a carbohydrate, and/or with acyclic polyacetals derived from polysaccharides (Papisov, 2001, ACS Symposium Series, 786: 301; incorporated herein by reference).

In some embodiments, polymers may be modified with a lipid or fatty acid group, properties of which are described in further detail below. In some embodiments, a fatty acid group may be one or more of butyric, caproic, caprylic, capric, lauric, myristic, palmitic, stearic, arachidic, behenic, or lignoceric acid. In some embodiments, a fatty acid group may be one or more of palmitoleic, oleic, vaccenic, linoleic, alpha-linoleic, gamma-linoleic, arachidonic, gadoleic, arachidonic, eicosapentaenoic, docosahexaenoic, or erucic acid.

In some embodiments, polymers may be polyesters, including copolymers comprising lactic acid and glycolic acid units, such as poly(lactic acid-co-glycolic acid) and poly(lactide-co-glycolide), collectively referred to herein as “PLGA”; and homopolymers comprising glycolic acid units, referred to herein as “PGA, ” and lactic acid units, such as poly-L-lactic acid, poly-D-lactic acid, poly-D, L-lactic acid, poly-L-lactide, poly-D-lactide, and poly-D, L-lactide, collectively referred to herein as “PLA. ” In some embodiments, exemplary polyesters include, for example, polyhydroxyacids; PEG copolymers and copolymers of lactide and glycolide (e. g., PLA-PEG copolymers, PGA-PEG copolymers, PLGA-PEG copolymers, and derivatives thereof. In some embodiments, polyesters include, for example, polyanhydrides, poly(ortho ester), poly(ortho ester)-PEG copolymers, poly(caprolactone), poly(caprolactone)-PEG copolymers, polylysine, polylysine-PEG copolymers, poly(ethylene imine), poly(ethylene imine)-PEG copolymers, poly(b-lac- tide-co-L-lysine), poly(serine ester), poly(4-hydroxy-L-pro- line ester), poly[a-(4-aminobutyl)-L-glycolic acid], and derivatives thereof.

In some embodiments, a polymer may be PLGA. PLGA is a biocompatible and biodegradable co-polymer of lactic acid and glycolic acid, and various forms of PLGA are characterized by the ratio of lactic acid: glycolic acid. Lactic acid can be L-lactic acid, D-lactic acid, or D, L-lactic acid. The degradation rate of PLGA can be adjusted by altering the lactic acid: glycolic acid ratio. In some embodiments, PLGA to be used in accordance with the present invention is characterized by a lactic acid: glycolic acid ratio of approximately 85: 15, approximately 75: 25, approximately 60: 40, approximately 50: 50, approximately 40: 60, approximately 25: 75, or approximately 15: 85.

In some embodiments, polymers may be one or more acrylic polymers. In certain embodiments, acrylic polymers include, for example, acrylic acid and methacrylic acid copolymers, methyl methacrylate copolymers, ethoxyethyl methacrylates, cyanoethyl methacrylate, aminoalkyl methacrylate copolymer, poly(acrylic acid), poly(methacrylic acid), methacrylic acid alkylamide copolymer, poly(methyl methacrylate), poly(methacrylic acid anhydride), methyl methacrylate, polymethacrylate, poly(methyl methacrylate)

copolymer, polyacrylamide, aminoalkyl methacrylate copolymer, glycidyl methacrylate copolymers, polycyanoacrylates, and combinations comprising one or more of the foregoing polymers. The acrylic polymer may comprise fully-polymerized copolymers of acrylic and methacrylic acid esters with a low content of quaternary ammonium groups.

In some embodiments, polymers can be cationic polymers. In general, cationic polymers are able to condense and/or protect negatively charged strands of nucleic acids (e. g. DNA, RNA, or derivatives thereof). Amine-containing polymers such as poly(lysine) (Zauner et al., 1998, Adv. Drug Del. Rev., 30: 97; and Kabanov et al., 1995, Bioconjugate Chem., 6: 7; both of which are incorporated herein by reference), poly(ethylene imine) (PEI; Boussif et al., 1995, Proc. Natl. Acad. Sci., USA, 1995, 92: 7297; incorporated herein by reference), and poly(amidoamine) dendrimers (Kukowska-Latallo et al., 1996, Proc. Natl. Acad. Sci., USA, 93: 4897; Tang et al., 1996, Bioconjugate Chem., 7: 703; and Haensler et al., 1993, Bioconjugate Chem., 4: 372; all of which are incorporated herein by reference) are positively- charged at physiological pH, form ion pairs with nucleic acids, and mediate transfection in a variety of cell lines.

In some embodiments, polymers can be degradable polyesters bearing cationic side chains (Putnam et al., 1999, Macromolecules, 32: 3658; Barrera et al., 1993, J. Am. Chem. Soc., 115: 11010; Kwon et al., 1989, Macromolecules, 22: 3250; Lim et al., 1999, J. Am. Chem. Soc., 121: 5633; and Zhou et al., 1990, Macromolecules, 23: 3399; all of which are incorporated herein by reference). Examples of these polyesters include poly(L-lactide-co-L-lysine) (Barrera et al., 1993, J. Am. Chem. Soc., 115: 11010; incorporated herein by reference), poly(serine ester) (Zhou et al., 1990, Macromolecules, 23: 3399; incorporated herein by reference), poly (4-hydroxy-L-proline ester) (Putnam et al., 1999, Macromolecules, 32: 3658; and Lim et al., 1999, J. Am. Chem. Soc., 121: 5633; both of which are incorporated herein by reference), and poly(4-hydroxy-L-proline ester) (Putnam et al., 1999, Macromolecules, 32: 3658; and Lim et al., 1999, J. Am. Chem. Soc., 121: 5633; both of which are incorporated herein by reference).

In some embodiments, polymers in accordance with the present invention may be carbohydrates, properties of which are described in further detail below. In some embodiments, a carbohydrate may be a polysaccharide comprising simple sugars (or their derivatives) connected by glycosidic bonds, as known in the art. In some embodiments, a carbohydrate may be one or more of pullulan, cellulose, microcrystalline cellulose, hydroxypropyl methylcellulose, hydroxycellulose, methylcellulose, dextran, cyclodextran, glycogen, starch, hydroxy ethyl starch, carageenan, glycon, amylose, chitosan, N, O-carboxylmethylchitosan, algin and alginic acid, starch, chitin, heparin, konjac, glucommannan, pustu- lan, heparin, hyaluronic acid, curdlan, and xanthan.

In some embodiments, a polymer in accordance with the present invention may be a protein or peptide, properties of which are described in further detail below. Exemplary proteins that may be used in accordance with the present invention include, but are not limited to, albumin, collagen, a poly(amino acid) (e. g., polylysine), an antibody, etc.

In some embodiments, a polymer in accordance with the present invention may be a nucleic acid (i. e., polynucleotide), properties of which are described in further detail below. Exemplary polynucleotides that may be used in accordance with the present invention include, but are not limited to, DNA, RNA, etc.

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