Tissue response to poly( l-lactic acid)-based blend with phospholipid polymer for biodegradable cardiovascular stents

Abstract

A temporary cardiovascular stent device by bioabsorbable materials might reduce late stent thrombosis. A water-soluble amphiphilic phospholipid polymer bearing phosphorylcholine groups (PMB30W) was blended with a high-molecular-weight poly( l-lactic acid) (PLLA) to reduce unfavorable tissue responses at the surface. The PLLA implants and the polymer blend (PLLA/PMB30W) implants were inserted into subcutaneous tissues of rats, the infrarenal aorta of rats, and the internal carotid arteries of rabbits. After 6 months subcutaneous implantation, the PLLA/PMB30W maintained high density of phosphorylcholine groups on the surface without a significant bioabsorption. After intravascular implantation, the cross-sectional areas of polymer tubing with diameters less than 1.6 mm were histomorphometrically measured. Compared to the PLLA tubing, the PLLA/PMB30W tubing significantly reduced the thrombus formation during 30 d of implantation. Human peripheral blood mononuclear cells were cultured on the PLLA and the PLLA/PMB30W to compare inflammatory reactions. Enzyme-linked immunosorbent assay quantified substantially decreased proinflammatory cytokines in the case of the PLLA/PMB30W. They were almost the same level as the negative controls. Thus, we conclude that the phosphorylcholine groups could reduce tissue responses significantly both in vivo and in vitro, and the PLLA/PMB30W is a promising material for preparing temporary cardiovascular stent devices.