Comparative examination of subcutaneous tissue reaction to high molecular materials in medical use

Because high molecular polymer is used as a material in vivo, it should be evaluated for safety according to ISO standard 10993-6 [1,2]. Polypropylene (PP), Polyethylene (PE) and polytetrafluoroethylene (FE) are high molecular materials in medical use, although the tissue reaction in a single material is not examined. They are also used as the negative control materials for ISO 10993-6 international standard biological evaluation of medical devices. In the present investigation, we examine the local effects after implantation of the above-mentioned materials. The data led us to believe that many researchers can know the tissue reactions to these biomaterials itself. This means next step of developing new biomaterials.The materials to be examined include 1) Polypropylene (PP: Prime Polypro; Prime Polymer Co., Ltd., Tokyo), 2) Polyethylene (PE: HI-ZEX, Prime Polymer Co., Ltd., Tokyo) and 3) Polytetrafluoroethylene (FE: TeflonRTFE; Du Pont-Mitsui Fluorochemicals Co., Ltd., Tokyo), in discoids 6 mm in diameter. Materials were prepared in the following thickness: PP, 0.54 mm; PE, 0.79 mm; and FE, 0.94 mm. The materials were then disinfected by autoclave treatment.A total of 18 male 9-week-old ddY mice weighing about 35 g (30-40 g) each were purchased from Japan SLC Inc. (Hamamatsu, Japan). The animals were kept in plastic cages with a floor mat (Paper Clean: Peparlet Co., Ltd., Shizuoka, Japan) under controlled air-conditioned room with water and solid diet (Picolab Rodent Diet 20: Japan SLC Inc., Hamamatsu, Japan) during the experimental periods.The Matsumoto Dental University Committee for Animal Experimentation approved the study.Prior to the examination, inhalation anesthesia was used with isoflurane (Isoflu: Dainippon Sumitomo Pharma Co., Osaka, Japan) and gas-air mixture (4.0% concentration). Immediately after the dorsal areas of the mice were disinfected with 70% ethanol, the incisions were made, and the materials were injected subcutaneously into the connective t