Development and characterization of an alginate-impregnated polyester vascular graft

Alignate gels are known to be biocompatible, degradable, and nontoxic. In this study, sodium alginate was impregnated into a porous, knitted polyester graft (Microvel double velour graft) 6 mm in diameter. The alginate-impregnated graft was investigated in vitro and in vivo to evaluate its potential for use as a new vascular graft impervious to blood, while retaining high porosity for tissue ingrowth and biological healing. For in vitro investigation, the coating weight, water permeability, morphology, and mechanical properties of the alginate-impregnated grafts were compared to those of control or commercially available collagen-impregnated (Hemashield) grafts. The water permeability of the controls (1846 mL/min.cm2 at 120 mm Hg) was reduced > 99% by the alginate impregnation, rendering the graft impervious to blood. The coating weight of the alginate was 45 mg/g of graft, producing a much lower value than that of the collagen-impregnated model (310 mg/g). For in vivo investigation, the alginate-impregnated grafts were implanted in the aorta of mongrel dogs without preclotting for scheduled periods ranging from 4 h to 6 months. The control grafts after preclotting and the collagen-impregnated grafts without preclotting were also implanted for 3 and 6 months for comparison. Gross observation of the explanted grafts and histologic examination of the representative sections were conducted for three types of grafts using a light microscope after hematoxylin-eosin staining. No significant differences were observed between the histologic appearance of the alginate-impregnated grafts and that of the preclotted and collagen-impregnated grafts in terms of the degree of inflammation, foreign-body giant cell reaction, and intimal fibrosis. Endothelial-like cells were present on the midsections of all the grafts after 3 months of implantation. The resorption rate of alginate impregnated into the graft was also examined after staining the sections with periodic acid-Schiff reagent, Toluidine blue, and Alcian blue, which are specific for alginates. The staining alginate was partially visible between the graft fabrics up to 1 month after implantation, but was completely resorbed after 3 months. This preliminary study demonstrated that the use of an alginate as a biological sealant instead of proteins such as collagen, gelatin, and albumin may be a feasible approach to developing imprevious textile arterial prostheses, since the proteins have been reported to be generally unstable, hard to obtain in pure forms, not easy to crosslink and control resorption rate, and difficult to render compatible with standard storage and sterilization procedures.