Bioabsorbable composition and coatings including same

Description of equivalent WO 2004066927 A2

Polyglactin 910-a New Synthetic Absorbable Suture". Jpn J Surg 11 (6):467-75, November 1981. U.S. Pat. No. 4,201,216 discloses a glycolide/lactide copolymer blended with calcium stearate as a suture coating.

Then U.S. Patent No. 5,716,376 provided a surgical suture coating comprising a) a copolymer comprising a predominant amount of epsilon-caprolactone and a minor amount of at least one other copolymerizable monomer and b) a salt of a lactylate ester of a Cio or greater fatty acid selected from the group consisting of calcium stearoyl lactylate, magnesium stearoyl lactylate, aluminum stearoyl lactylate, barium stearoyl lactylate, zinc stearoyl lactylate, calcium palmityl lactylate, magnesium palmityl lactylate, aluminum palmityl lactylate, barium palmityl lactylate, or zinc palmityl lactylate, calcium olelyl lactylate, magnesium olelyl lactylate, aluminum olelyl lactylate, barium olelyl lactylate, and zinc olelyl lactylate.

U.S. Patent No. 5,312,437 discloses an absorbable suture coating composition comprising the product obtained by reacting a mixture of poly(oxypropylene)glycol and a coplymer of lactide/glycolide copolymer.

U.S. Patent No. 5,425,949 discloses a bioabsorbable copolymer obtained by polymerizing a major amount of epsilon-caprolactone and a minor amount of at least one other copolymerizable monomer in the presence of a polyhydric alcohol initiator. The copolymer can be used as a suture coating. U.S. Patent No. 6,177,094 discloses a bioabsorbable blend comprising the reaction product of component A and component B wherein component A comprises a copolymer obtained by polymerizing a major amount of epsilon-caprolactone and a minor amount of at least one other copolymerizable monomer in the presence of polyhydric alcohol as initiator; and component B comprises a composition comprising the product obtained by reacting a mixture of poly(propylene)glycol and lactide glycolide copolymer. The blend can be used as a suture coating.

Although commercially available surgical sutures such as Polysorb have excellent handling characteristics, it would be advantageous to provide another bioabsorbable suture coating that even further enhances the physical characteristics of the surgical sutures that it coats. SUMMARY

A composition useful for coating surgical sutures has been found. The composition comprises 1) a blend of bioabsorbable polymer or copolymer, preferably a glycolide/lactide copolymer, and the reaction product of a bioabsorbable copolymer obtained by polymerizing a major amount of epsilon-caprolactone and a minor amount of at least one other copolymerizable monomer, optionally in the presence of a polyhydric alcohol initiator, and 2) a fatty acid salt, preferably calcium stearate or a salt of a fatty acid ester, preferably calcium stearoyl lactylate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a coated suture attached to a needle described herein.

DESCRIPTION OF THE PREFERED EMBODIMENTS

The bioabsorbable blend may be prepared by conventional methods well known in the art. Preferrably, about 10 to about 90 percent by weight epsilon-caprolactone containing copolymer is mixed with about 90 to about 10 percent by weight of bioabsorbable polymer and/or copolymer at about ambient temperature and stirred for about 4 hours. More preferably, about 40 to 60 percent by weight epsilon-caprolactone containing copolymer is mixed with about 60 to 40 percent by weight a bioabsorbable polymer and/or copolymer at ambient temperature and stirred for about 4 hours. Most preferrably about 50 percent by weight epsilon-caprolactone containing copolymer is mixed with about 50 percent by weight of bioabsorbable copolymer at ambient temperature and stirred for about 4 hours. In an embodiment, the epsilon caprolactone containing copolymer is mixed with the bioabsorbable copolymer and then dissolved in a solvent cocktail to which the fatty acid salt or fatty acid ester salt is added with stirring for at least about an hour.

The ratio of the blend polymer and the fatty acid salt or the fatty acid ester salt in the coating composition may vary depending upon the specific components selected and the particular suture being coated. The ratio of polymer to salt is suitably within the range of 4:1 to 1 :4 parts by weight and preferably is about 1:1 parts by weight.

Preferably the solvent contains methylene chloride, ethanol, and acetone. Most preferably the solvent composition is fabricated such that the density of the polymer solution matches that of the salt, while maintaining the solubility of the polymer blend. Suitable solvent compositions include about 60 to about 65 percent by weight methylene chloride, about 18 to about 0 percent by weight ethanol, and about 22 to about 35 percent by weight acetone.

Suitable caprolactone containing copolymers include copolymers which may be synthesized by well known conventional polymerization techniques; see, for example

Principles of polymerization, George Odian, III Edition; 1991 pp.569-573, the contents of which are incorporated herein by reference.

In one embodiment, the caprolactone containing copolymer is obtained by polymerizing a major amount of epsilon-caprolactone and a minor amount of at least one other copolymerizable monomer or mixture of such monomers. In another embodiment, the polymerization of the above occurs in the presence of a polyhydric alcohol initiator. The polymerization of these monomers contemplates all of the various types of monomer addition, i.e., simultaneous, sequential, simultaneous followed by sequential, sequential followed by simultaneous, etc. The copolymer herein can contain from about 70 to about 98, and preferably from about 80 to about 95, weight percent epsilon-caprolactone derived units, the balance of the copolymer being derived from the other copolymerizable monomer(s).

Suitable monomers which can be copolymerized with epsilon-caprolactone include alkylene carbonates such as trimethylene carbonate, tetramethylenecarbonate, dimethyl trimethylene carbonate; dioxanones; dioxepanones; absorbable cyclic amides; absorbable cyclic ether-esters derived from crown ethers; hydroxyacids capable of esterification, including both alpha hydroxy acids (such as glycolic acid and lactic acid) and beta hydroxyacids (such as beta hydroxybutyric acid and gamma hydroxyvaleric acid); polyalkyl ethers (such as polyethylene glycol and polyloropyline glycol and combinations thereof; with glycolide being a preferred monomer. Suitable polyhydric alcohol initiators include glycerol, trimethylolpropane, 1,2,4- butanetriol, 1,2,6-hexanetriol, triethanolamine, triisopropanolamine, erythritol, threitol, pentaerythritol, ribitol, arabinitol, xylitol, N,N,N',N'-tetrakis(2- hydroxyethyl)ethylenediamine, N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine, dipentaerythritol, allitol, dulcitol, glucitol, altritol, iditol, sorbitol, mannitol, inositol, and the like; with mannitol being preferred.

The polyhydric alcohol initiator is generally employed in small amounts, e.g., from about 0.01 to about 5, and preferably from about 0.1 to about 3, weight percent of the total monomer mixture.

Suitable bioabsorbable polymers include homopolymers of lactide and glycolide, as well as, copolymers of lactide or glycolide and poly (p-dioxanone), poly(alkylene oxalate), copolymers of vinyl acetates with unsaturated carboxylic acids such as crotonic, acrylic, and methacrylic acids; water soluble or dispersible cellulose derivatives such as methyl cellulose, hydroxymethyl cellulose and carboxymethyl cellulose; natural gums; ethylene oxide polymers; polyacrylamide; collagen; gelatin; polyamino acids; polyvinyl alcohol; polyvinyl pyrrolidone; absorbable conjugated unsaturated triglycerides such as dehydrated castor oil, and mixtures thereof. Glycolide/lactide copolymers are preferred. Copolymers containing about 15 to about 85 mole percent lactide are more preferred. Copolymers contain about 65 lactide mole percent and 35 mole percent glycolide are most preferred.

Suitable fatty acid salts include the calcium, magnesium, barium, aluminum, and zinc salts of C6 and higher fatty acids, particularly those having from about 12 to 22 carbon atoms and mixtures thereof. The calcium salts of stearic, palmitic and oleic acids are preferred.

Suitable fatty acid ester salts inlcude a lactylate ester of a Cio or greater fatty acid, such as magnesium stearoyl lactylate, aluminum stearoyl lactylate, barium stearoyl lactylate zinc stearoyl lactylate, calcium palmityl lactylate, magnesium palmityl lactylate, aluminum palmityl lactylate barium palmityl lactylate, or zinc palmityl lactylate, calcium olelyl lactylate, magnesium olelyl lactylate, aluminum olelyl lactylate, barium olelyl lactylate, zinc olelyl lactylate or calcium stearoyl lactylate. One or more medico-surgically useful substances may be incorporated into the composition, e.g., those which accelerate or beneficially modify the healing process when particles are applied to a surgical repair site. So, for example, the composition can carry a therapeutic agent which will be deposited at the repair .site. The therapeutic agent can be chosen for its antimicrobial properties, capability for promoting repair or reconstruction and/or new tissue growth. Antimicrobial agents such as broad spectrum antibiotics (gentamycin, erythromycin or derivatized glycopeptides) which are slowly released into the tissue can be applied in this manner to aid in combating clinical and sub-clinical infections in a tissue repair site. Additional suitable antimicrobial agents include, β- lactams, quinolones, aminoglycosides, antibiotics (such as cephalosporins, penecillins, quinolones, tetracyclines, erythromycins, extended-spectrum macrolides, aminoglycosides, sulfonamides, chloramaphenicol, clindamycin, vancomycin, spectinomycin, carbapenems, monobactams, streptogramin, fosfomycin, tromethamines and teicoplanins) fusidic acid, novobiocin, minocycline, rifampin, and polymyxin. Also suitable are biocides such as heavy metals (Ag, Zn, Cu, Ge) their salts and derivatives; biguanides (such as chlorhexidine, alexidine, and polymeric biguanides), their salts and derivatives; phenols and bisphenols (such as triclosan and hexachlorophene) their salts and derivatives; halogen releasing agents (such as iodine and iodosphers); and quatenary ammonium compounds. The composition may also include antiseptics, anesthetics and anti-inflammatory agents. To promote repair and/or tissue growth, one or several growth promoting factors can be introduced into the sutures, e.g., fibroblast growth factor, bone growth factor, epidermal growth factor, platelet derived growth factor, macrophage derived growth factor, alveolar derived growth factor, monocyte derived growth factor, magainin, and so forth. Some therapeutic indications are: glycerol with tissue or kidney plasminogen activator to cause thrombosis, superoxide dimutase to scavenge tissue damaging free radicals, tumor necrosis factor for cancer therapy or colony stimulating factor and interferon, interleukin-2 or other lymphokine to enhance the immune system. It is contemplated that composition may be dyed to increase visibility if used in the surgical field. Dyes known to be suitable for incorporation in sutures can be used. Such dyes include but are not limited to carbon black, bone black, D&C Green No. 6, and D&C Niolet o. 2 as described in the handbook of U.S. Colorants for Food, Drugs and Cosmetics by Daniel M. Marrion (1979).

While the composition herein can be applied to any type of suture, it is essentially intended for application to a braided suture, a preferred type of which is disclosed in U.S. Pat. No. 5,019,093. The amount of composition applied to a braided suture will vary depending upon the structure of the suture, e.g., the number of filaments, tightness of braid or twist, the size of the suture and its composition. Suitable coating levels range from about 0.3% to about 15% with about 0.5% to about 8% being preferred.

The coated suture, suture 101, may be attached to a surgical needle 100 as shown in FIG. 1 by methods well known in the art. ^"Wounds may be sutured by passing the needled suture through tissue to create wound closure. The needle preferably is then removed from the suture and the suture tied.

The following examples are given as an illustration of the preparation of copolymers, blends and coatings described herein as well as of the preparation and superior characteristics of the sutures described herein. It should be noted that the invention is not limited to the specific details embodied in the examples. EXAMPLES

EXAMPLE 1 Dry glycolide (200 grams), epsilon-caprolactone (1800 grams), stannous octoate as catalyst (0.40 grams) and dry d. mannitol as initiator (3.0 grams) were mixed under nitrogen for one hour. The mixture was heated in a reactor at a temperature of 160°C for 12 hours. The epsilon-caprolactone/glycolide copolymer was then sampled.

EXAMPLE 2

Dry glycolide (61 Og), L-Lactide (1390g), stannous octoate as catalyst (0.40g), and dry dodecanol as initiator (2.60g) were mixed under N2 in a reactor for 1 hour. The mixture was heated in a reactor at a 160° C for 8 hours. The 1-lactide/glycolide copolymer was then sampled. EXAMPLE 3

In a 500 mL container, 176.7grams methylene chloride, 39.9grams ethanol, and 68.4grams acetone were mixed for 15 minutes at ambient conditions. To the above solution, 3.75 g of-the copolymer of Example 2 and 3.75 grams of the copolymer of Example 1 were added while the solution was being stirred. The stirring was continued for 3 hours or until all the copolymers were completely dissolved. 7.5 grams of calcium stearate were added while the solution was stirred. The stirring continued for at about an hour to ensure complete dispersion of the salt.

EXAMPLE 4

A size 2/0 Polysorb surgical suture was drawn through a coating solution applicator which applied the coating solution of Example 3, at a level of about 2.1 percent by weight of the suture, to coat the suture with the coating solution.

EXAMPLE 5

A size 2/0 Polysorb surgical suture was drawn through a coating solution applicator which applied the coating solution of Example 3, at a level of about 2.8 percent by weight of the suture, to coat the suture with the coating solution.

EXAMPLE 6

A size 2/0 Polysorb surgical suture was drawn through a coating solution applicator which applied the coating solution of Example 3, at a level of about 3.5 percent by weight of the suture, to coat the suture with the coating solution.

It will be understood that various modifications may be made to the embodiments disclosed herein. Therefore, the above description should not be construed as limiting, but merely as exemplifications of preferred embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.