Objectives Polyesters are the major polymers used in coating or making biodegradable stent, but with issues of inflammation response and insufficient radial strength. We hypothesise blending Poly (D, L-Lactide-Co-Glycolide (PLGA) and Poly-L-lactic acid (PLLA) with Amorphous calcium phosphate (ACP) might solve the problems. The purpose of this study is to investigate the biocompatibility of PLGA/ACP and PLLA/ACP composite in vivo.
Methods Metal stents were coated with either polyethylene-co-vinyl acetate/poly-n-butyl methacrylate (PEVA/PBMA), PLGA and PLGA/ACP composite, respectively, and implanted into rat aortas for one and three months. In addition, PLLA/ACP and PLLA polymers were extruded into stent tubes and implanted into rabbit iliac arteries for one month.
Results At one month, stents coated with PLGA/ACP group had significantly lower percentage of restenosis and arterial inflammatory score as compared with those coated with PLGA group, and had significantly higher endothelial scores than both PEVA/PBMA and PLGA groups (PLGA/ACP vs. PLGA, restenosis%: 21.24 ± 2.59 vs. 32.12 ± 3.93, P < 0.05; inflammatory score: 1.25 ± 0.35 vs. 2.30 ± 0.21, P < 0.05. PLGA/ACP vs. PEVA/PBMA vs. PLGA, endothelial scores: 1.78 ± 0.46 vs. 1.17 ± 0.18 vs. 1.20 ± 0.18, P < 0.05). Inflammatory cell infiltration in the target vessel walls (Rabbit Iliac Arteries) were significantly less in PLLA/ACP group than that in PLLA group (PLLA/ACP vs. PLLA, % NF-κB-positive cells: 12.23 ± 1.36% vs. 24.13 ± 1.45%, P < 0.05). At three months, PLGA/ACP group had no necrotic neointima and higher endothelial scores compared with PEVA/PBMA group (PLGA/ACP vs. PEVA/PBMA, inflammatory score: 1.33 ± 0.33 vs. 2.27 ± 0.55, P < 0.05; endothelial score: 2.33 ± 0.33 vs. 1.20 ± 0.18, P < 0.05). Systemically, no biochemical and pathological evidence of toxicity were found in both rat and rabbit species after one and three month implantation for both PLGA/ACP and PLLA/ACP composites.
Conclusions PLLA/ACP and PLGA/ACP may potentially be promising biodegradable materials in making biodegradable drug eluting stent either as a coating or stent platform.