In vivo biocompatibility of aliphatic segmented polyurethane in rabbit.

ABSTRACT

An aliphatic segmented polyurethane with soft to hard segment ratio 3 was synthesised using hexamethylene diisocyanate, polypropylene glycol 400 and 1,4-butane diol.A stainless steel cage implant system has been used to study the in vivo biocompatibility of this polyurethane. United States Pharmacopoeia negative control polyethylene was used for the comparison. Three cages, one with polyurethane another with United States Pharmacopoeia polyethylene and the third control empty cage were implanted subcutaneously in the dorsal aspect of rabbits. The inflammatory exudate surrounding the material was aspirated from the cages on 4, 7, 14 and 21 days after implantation. The total protein content in the exudate aspirated from all the 3 cages was significantly higher at 7 days than in the reported normal rabbit serum of New Zealand white rabbit but equal to that of our rabbit colony. The albumin concentration was lower in the initial period but increased at 21 days post implantation period in all the cages. Concentration of α1, α2 and γ-globulin also decreased in all cages at 21 days. Neutrophils were predominant in all the exudates aspirated from polyurethane, polyethylene and empty control cages during whole implantation period. This is attributed to the profound effect of the cages on the surrounding vasculature. Macrophage was found to be seen during acute phase of inflammation due to the migration of macrophage along with neutrophil towards the inflammatory lesion. The percentage of neutrophils showed a faster decline in the cage containing polyethylene at 21 days. The extra cellular alkaline phosphatase activity, though higher in exudate from cages containing polyurethane at 14 days post implantation, was same in all 3 cages at 21 days. Leucine amino peptidase activity was found to be decreased at 21 days of post implantation time though the empty control cage exhibited an increase at 14 days post implantation. The inflammatory response at 21 days was similar in polyurethane and the control polyethylene.