Electrospinning of l-tyrosine polyurethanes for potential biomedical applications

Biodegradable segmented l-tyrosine polyurethanes (LTUs) have been developed using a tyrosine based chain extender desaminotyrosine-tyrosyl-hexyl ester (DTH). Two such biodegradable LTUs, polycaprolactone diol-hexamethylene diisocyanate-desaminotyrosine-tyrosyl-hexyl-ester (PCL-L-DTH) and polycaprolactone diol-4,4′-methylenebis(cyclohexyl isocyanate)-desaminotyrosine-tyrosyl-hexyl-ester (PCL-C-DTH), have been electrospun, and the effect of solution concentration on the membrane properties has been examined. Scanning electron microscopy (SEM) images show that fiber diameter and structural morphology of the electrospun LTU membranes are a function of the polymer solution concentration. It has been observed all concentrations of PCL-L-DTH lead to the formation of beaded nanofibers; whereas, PCL-C-DTH polyurethane leads to the formation of non-beaded fibers with diameters in the micrometer range. Furthermore, the average fiber diameter enlarges with an increase in the polymer solution concentration. Hydrolytic degradation studies show similar mass loss profiles for both PCL-L-DTH and PCL-C-DTH polyurethane membranes over a period of 28 days. However, the loss of structure and morphology is more readily observed in the case of PCL-L-DTH membranes. Based on the results obtained from this investigation, the electrospun non-woven LTU membranes show excellent potential for biomedical applications such as formulation of drug/gene delivery devices and tissue engineering scaffolds.