In vivo degradation and biocompatibility study of in vitro pre-degraded as-polymerized polylactide particles

Abstract

The degradation of high molecular weight as-polymerized poly(L-lactide) (PLLA) is very slow; it takes more than 5.6 yr for total resorption. Moreover, the degradation products of as-polymerized PLLA bone plates, consisting of numerous stable particles of high crystallinity, are related with a subcutaneous swelling in patients 3 yr postoperatively. In order to avoid these complications, polymers were developed that are anticipated to have comparable mechanical properties but a higher degradation rate and do not degrade into highly stable particles that can induce a subcutaneous swelling. On chemical grounds it can be expected that copolymerization of PLLA with 4% D-lactide (PLA96) or by modifying PLLA through cross-linking (CL-PLLA) will lead to less stable particles and a higher degradation rate. To evaluate the long-term suitability of these as-polymerized polymers, the biocompatibility of the degradation products should be studied. Considering the very slow degradation rate of as-polymerized PLLA, in vitro pre-degradation at elevated temperatures was used to shorten the in vivo follow-up periods. In this study, the biocompatibility and degradation of as-polymerized PLLA, PLA96 and CL-PLLA were investigated by implanting pre-degraded particulate materials subcutaneously in rats. Animals were killed after a postoperative period varying from 3 to 80 wk. Light and electron microscopical analysis and quantitative measurements were performed. The histological response of all three pre-degraded materials showed a good similarity with in vivo implanted material. Pre-degraded PLLA induced a mild foreign body reaction and showed a slow degradation rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Lamellar orientation and interlamellar cracks in co-crystallized poly(ethylene oxide)/poly(L-lactic acid) blend

“…10 Partial miscibility with phase domains in blends of PEO with PLLA of high molecular weight has been claimed. 6,7 Reportedly, blending PEO with PLLA can further enhance the biocompatibility of PLLA; 11,12 however, separate domains in both the amorphous and crystalline domains in PEO/PLLA might make it complicated to addressing the biocompatibility.…”

Non-Thermal Plasma Surface Modification of Biodegradable Polymers

“…Compared to PGA, PLLA slowly degrades: when PLLA is hydrolyzed, it loses its strength in circa 6 months. However, no mass loss is observed for a very long time and total degradation amount up to several years (Middleton & Tipton, 2000, Nair & Laurencin, 2007, Bergsma et al, 1995. Next to this slow degradation, PLLA offers good tensile strength, a high tensile modulus and low extension and can therefore be applied in load bearing applications like in orthopaedic fixation devices (Nair & Laurencin, 2007).…”

Keratin-based Nanofibres

“…Our attempts to obtain filaments of pure regenerated keratin from water were indeed unsuccessful; moreover, literature reports on the fabrication of regenerated keratin films ) using cross linking agents, and the fabrication of composite nanofibres of regenerated silk fibroin blended with synthetic polymers such as poly(ethylene oxide) (PEO) (Jin et al, 2002). PEO is an amphiphilic water soluble and nondegradable polymer, with good biocompatibility (Desai & Hubbel, 1991) and low toxicity (Bergsma et al, 1995). This polymer is often used as an ideal model for the electrospinning process (Theron et al, 2004;Son et al, 2004) because it can be electrospun without defects from aqueous solutions in a rather narrow range of conditions.…”