Process of surface activation of biocompatible and bioabsorbable

Details Process of surface activation of biocompatible and bioabsorbable Process of surface activation of biocompatible and bioabsorbable

1998-01-27

2000-08-22

Acquah, Samuel A.

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Treating polymer containing material or treating a solid...

528483, 528488, 528489, 528492, 528495, 528503, C08F 600

Patent

active

061074535

DESCRIPTION:

BRIEF SUMMARY
The invention relates to surface-activated copolymers of lactic acid and .epsilon.-caprolactone and to a procedure for preparation thereof.
In recent times homo- and copolymers of lactic acid have been the subject of growing attention regarding their potential applications, in part already put into practice, in the biomedical sector.
Such applications, which take advantage of the biocompatibility and biodegradability of these materials, comprise among other things the manufacture of prosthetic implants, suture threads, microspheres for vehicling of principal active ingredients.
A relative advantage of these materials is that of eliminating the need for a second surgical intervention, sometimes necessary for removing the implant, thanks to the gradual biodegradability which favors regeneration of the pre-existing tissues.
This advantage has been exploited, for example, in the preparation of bioabsorbable suture threads using homo- and copolymers of glycolic acid, commercially known as DEXON (mark of the company Davis and Jeck) and VICRYL (mark of the company Ethicon). In more recent times commercialisation has begun of the first products for the orthopaedic sector, known as BIOFIX (mark of Bioscience Oy) and ORTHOSORB (mark of the company Johnson and Johnson).
A field of use of bioabsorbable materials which has great use potential is the preparation of vascular grafts. Implants at present available, often made in DACRON (a material provided by the company Du Pont of Nemurs), as they are not bioabsorbable, lack in some important requisites, such as for example a complete absence of thrombogenicity of the internal wall, or elastic properties which remain unaltered over time [New Polymeric Mater, 1 (2), 111-126 (1988)]. These limitations become important especially when prostheses are below 6 mm diameter, which often leads during surgery to implant of autologous veins to repair small-caliber arteries, with all the problems deriving there-from.
The development of a biodegradable vascular prosthesis, which would thus promote the regeneration of pre-existing tissue, is of great interest and is at present the object of many studies for example, see Colloid Polym. Sci 264, 854-858 (1986) , but is also hindered by the problem of thrombogenicity for small calibers.
Thrombotic formation on the internal wall of the prosthesis happens especially during the initial implant phase, that is before the wall has been covered with endothelial cells, for which reason a biocompatible and bioabsorbable material for the manufacturing of a vascular graft would have a relevant advantage if it could have surface alterations aimed at accelerating the endothelialisation process.
The copolymers of lactic acid (L-lactic) and .epsilon.-caprolactone, developed in 1975 by Gulf Oil see U.S. Pat. No. 4,057,537 (Sinclair) are very interesting materials for various biomedical uses, among which the realisation of nerve guides Biomaterial 15 (3), 189-193 (1994), J. Mater Sci. Mater in Medicine 4, 521-525 (1993), suture threads and bioabsorbable vascular prostheses.
The interest in these materials is linked, other than for their biocompatibility and bioabsorbability, to their excellent elastic properties (Polymer Bulletin 25, 335-341 (1991)) which are stable over time, especially for copolymers with about equal components of two comonomers (Makromol Chem 194, 2463-2469 (1993)).
These materials, on the other hand, have the drawback as far as biomedical use is concerned of having a low hydrophilicity, which reduces their wettability and the adherence of the organism cells, namely the endothelial cells. For the poly (L-Lactide-co-.epsilon.-caprolactone) at 50/50 weight, for example, the wetting angle measured with distilled water in air at 23.degree. C. is 82.degree., thus very high.
GB-A-2,141,435 discloses a method based on irradiation or hydrolytic treatments to control the physical properties of structural surgical elements made from bioabsorbable polymer materials so that the rate of strength loss and degradation in vivo is alterated to achieve

REFERENCES:
patent: 5236563 (1993-08-01), Loh

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