A new histological method of estimating the in vivo performance of biomedical polymer materials was developed by means of microspheres. Some kinds of microsphere suspensions in saline were injected noninvasively into the target organs e. g. muscle, liver, kidney, pancreas and spleen of rats. The bioreactions of the injected regions were histologically examined. In addition, the microspheres coated with a variety of polyelectrolyte complexes under development were injected and the bioreactivity of the coated materials was evaluated. The microsphere method was found to be very advantageous as compared with the conventional method e. g. the filmimplantation method.
