The antithrombotic versus calcium antagonistic effects of polyethylene glycol grafted bovine pericardium

Cardiovascular calcification, the formation of calcium phosphate deposits in cardiovascular tissue, is a common end stage phenomenon affecting a wide variety of bioprosthesis. This study proposes a novel approach of reducing pericardial calcification and thrombosis via coupling polyethylene glycols (PEG) to glutaraldehyde treated bovine pericardium via acetal linkages. The calcification of the PEG modified tissue and the control pericardium (extracted and glutaraldehyde treated) was investigated by in vivo rat subcutaneous implantation models and by in vitro meta stable calcium phosphate solutions. Scanning electron microscopy showed that calcification primarily involved the surface of collagen fibrils and the intrafibrillar spaces. However, the grafting of pericardium with PEG-20,000 had dramatically modified the surface and subsequently inhibited the deposits of calcium. Further, the modified tissue had also reduced the platelet surface attachment. Such a reduced calcification of PEG modified tissues can be explained by decrease of free aldehyde groups, a space filling effect and therefore improved biostability and synergistic blood compatible effects of PEG after coupling to the tissues. This simple method can be a useful anticalcification treatment for implantable tissue valves.