Absorbable E-caprolactone polymers and medical devices

Details Absorbable E-caprolactone polymers and medical devices Absorbable E-caprolactone polymers and medical devices

1998-06-29

2001-03-06

Clardy, S. Mark (Department: 1616)

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Biocides; animal or insect repellents or attractants

C606S230000, C606S231000

Reexamination Certificate

active

06197320

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to crystalline, low melting, &egr;-caprolactone polymers bearing basic amine functionalities which are linked to the ester chain ionically or covalently to induce catalyzed hydrolysis. The ester components can be derived from &egr;-caprolactone with or without small amounts of glycolide, and/or similar lactones. Such polymers with accelerated absorption profiles are especially adapted for use as transient coatings for absorbable multifilament surgical sutures (and other medical implants).
Multifilament surgical sutures such as Dexon® polyglycolide multifilament suture typically require a surface coating to improve their handling and knotting characteristics. Capitalizing on the desirable low melting temperature, crystallinity, and rheological properties of polycaprolactone and its copolymers as coating materials, several compositions based on this polymer were investigated as coatings for surgical sutures. Recognizing the fact that the &egr;-caprolactone homopolymer is essentially non-absorbable led to the development of copolymers of &egr;-caprolactone with variable amounts of more absorbable monomers to improve the coating absorbability. U.S. Pat. No. 4,624,256 discloses a suture coating copolymer of at least 90 percent &egr;-caprolactone and a biodegradable monomer and optionally a lubricating agent. Examples of monomers for the biodegradable polymers disclosed include glycolic acid and glycolide, as well as well-known monomers typically used to prepare absorbable polymer fibers or coatings for multifilament sutures. U.S. Pat. No. 4,788,979 and U.S. Pat. No. 4,791,929 disclose a bioabsorbable coating of a copolymer of at least 50 percent &egr;-caprolactone and glycolide. Sutures coated with such polymers are reported to be less stiff than sutures coated with other materials and the physical properties of the coated suture are also reported to be acceptable. U.S. Pat. No. 4,994,074 discloses copolymers of a predominant amount of &egr;-caprolactone, the balance being glycolide and glycolic acid. The use of glycolic acid as a comonomer into the copolymers of this invention was reported to increase the rate of absorption of the copolymer when used as a coating for multifilament surgical sutures.
Unfortunately, the problem of adequate bioabsorbability of &egr;-caprolactone-based polymers without detrimental effects on their desirable properties as coatings still remains. Specifically, the use of sufficient amounts of glycolide to achieve sufficient absorbability of the copolymeric coating can compromise its crystallinity and melting characteristics, for it may become amorphous or liquid near room temperature. On the other hand, the strategy of using glycolic acid to achieve the reported results in coating absorbability does limit the ability to produce sufficiently long chain molecules to achieve optimum frictional properties, due to glycolic acid's known properties as both a ring-opening initiator chain terminator. Thus, a totally new approach to modifying the absorbability of polycaprolactone and its copolymers without affecting their desirable properties as suture coatings (or coatings for surgical device) would be a more desirable goal.
SUMMARY OF THE INVENTION
One aspect of the invention are low melting, crystalline, basic nitrogenous polyesters, or polyesteramides, where the amine functionality represents between 1 and 20 percent of the total weight, while the repeat units of the polyester chain originate predominantly from &egr;-caprolactone. The balance ester sequences can be derived from glycolide, lactide p-dioxanone and/or one or more of the corresponding hydroxy acids. The amine functionality can be linked to the polyester chain ionically or covalently.
In another aspect, the invention is a coating for a surgical suture which displays autocatalyzed hydrolysis and improved absorbability over polyester coatings of the prior art which are devoid of any basic amine functionality. This coating comprises a low viscosity melt or a solution in an organic solvent, of the amine-bearing polyesters described above. Surprisingly, the incorporation of 1 to 10 percent of the amine functionality increased the polyester absorbability substantially, without compromising its desirable physical properties such as those associated with crystallinity and melting profile.
Polyesters bearing the amine-functionalities subject of this invention and coating derived therefrom can be used for coating bioabsorbable multifilament surgical sutures, as well as other surgical closure devices and indwelling devices. In addition, they may be used alone or as carriers or matrices for viable cells and vaccines, or as a coating containing bioactive agents such as growth factors, antimicrobials and antibiotics.


REFERENCES:
patent: 5522842 (1996-06-01), Shalaby
patent: 5773563 (1998-06-01), Shalaby

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