Tissues of mice that had had microchip transponders with surfaces made of bioglass, bioglass with a polypropylene cap, parylene C, titanium or aluminium oxide inserted were examined histologically, and the growth of two lines of feline fibroblastoid cells around these transponders was examined in vitro. The results for bioglass and aluminium oxide were similar. In vitro, there were almost no cells around or on the transponders; in vivo, there was often granulomatous inflammation in the surrounding tissue. In the case of the bioglass, this reaction seemed to be induced by petrolatum, which was added by the manufacturer for technical reasons, rather than by the bioglass itself. In some of the mice, polypropylene caused a proliferation of granulation tissue. In vitro, the cellularity around the transponders was high, but only a moderate number of cells were found on the material. In vivo, around the parylene C transponders, there were occasionally small fragments of foreign material, surrounded by a foreign body reaction; in vitro, the results for parylene C resembled those for polypropylene. In vivo, particles of titanium were sometimes visible in the connective tissue adjacent to the titanium transponders, and sometimes accompanied by a foreign body reaction; in vitro, a confluent layer of cells developed on the transponders, with a high cellularity around them.
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