In vivo degradation and biocompatibility study of in vitro pre-degraded as-polymerized polyactide particles.
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)
Bergsma
J E
JE
Department of Oral and Maxillofacial Surgery, University Hospital, Groningen, The Netherlands.
Rozema
F R
FR
Bos
R R
RR
Boering
G
G
de Bruijn
W C
WC
Pennings
A J
AJ
D000818:Animals; D001672:Biocompatible Materials; D001673:Biodegradation, Environmental; D001860:Bone Plates / Q000009:adverse effects*; D003238:Connective Tissue / Q000473:pathology / Q000648:ultrastructure; D003692:Delayed-Action Preparations; D006801:Humans; D007091:Image Processing, Computer-Assisted; D066298:In Vitro Techniques; D007773:Lactates / Q000737:chemistry / Q000378:metabolism*; D019344:Lactic Acid; D008264:Macrophages / Q000166:cytology / Q000648:ultrastructure; D008297:Male; D008854:Microscopy, Electron; D008970:Molecular Weight; D010316:Particle Size; D011091:Polyesters; D011108:Polymers / Q000737:chemistry / Q000378:metabolism*; D011183:Postoperative Complications; D051381:Rats; D017208:Rats, Wistar
D001672:Biocompatible Materials; D003692:Delayed-Action Preparations; D007773:Lactates; D011091:Polyesters; D011108:Polymers; D019344:Lactic Acid; C033616:poly(lactide)