Development of a hybrid cardiovascular graft using a tissue engineering approach 1

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Abstract
Tissue engineering of endothelial cells (EC) and chemical engineering with anticoagulant moieties has been undertaken in order to improve prosthetic graft patency and thrombogenicity. This was done by covalently bonding a compliant poly(carbonate-urea)urethane graft (MyoLink™) with with arginine-glycine-aspartate (RGD) or/and heparin (Hep) to ascertain whether EC retention could be improved. The retention of these moieties and EC was assessed after exposure to pulsatile flow. We covalently bonded RGD, Hep, and RGD/Hep onto the luminal surface of MyoLink using spacer arm technology. Narrow-beam X-ray photoelectron spectroscopy was carried out to check the efficiency of the bonding. EC were radiolabeled and seeded onto native MyoLink and with 1) RGD-, 2) Hep-, and 3) RGD/Hep-bonded grafts and exposed to shear stress in a physiological flow circuit for 6 h, which reproduces femoral artery flow waveforms and pulsatility. Results were recorded on a gamma camera imaging system. Viability of cells was tested with a modified Alamar Blue assay (ABA) and scanning electron microscopy for morphological appearance of seeded cells. Experiments were repeated (n=6). RGD, Hep, and RGD/Hep were bonded together in a uniform distribution on the luminal surface of each graft type, and bioactivity of each moiety covalently bonded was very high. In the flow circuit, there was exponential cell retention for the first 60 min of flow for all the grafts, but after 6 h of exposure to pulsatile flow the RGD/Hep-bonded graft had a significantly better cell retention rate than native MyoLink (75.7%±2.3 vs. 60.5±10.1, PPFASEB J. 16, 791–796 (2002)