Methods for the measurement of cell and tissue compatibility including tissue regeneration processes

Biocompatibility is one of the main requirements for the safe use of medical devices. Determination of cytotoxicity is part of the initial evaluation stipulated by ISO standards for the biological evaluation of medical devices. The use of cell cultures to test the biocompatibility of drugs, biomaterials or treatment techniques used in various disciplines is gaining in importance. A wide variety of self-initiated and commercially available cell lines has been evaluated and used: cultured fibroblasts from human skin, buccal mucosa, periodontal membrane, embryonic lung, epithelial and HeLa cells; cultures of human keratinocytes and HaCaT cells; different murine cell lines (C3H-L, Balb/c 3T3, L929 and others) as well as murine cells cultured from liver and spleen; T-lymphocytes from lymph nodes and macrophages obtained by lavage. All of the above cells are suitable for use in biocompatibility tests. Nevertheless, the general opinion is that toxicity tests in vitro will be more convincing when performed with cells that are homologous with the human tissue concerned. In accordance, appropriate cell lines for use in cytotoxicity and tolerance tests concerning the skin would be human dermal fibroblasts and human epidermal keratinocytes, as they take an active part in the immune response, inflammatory processes, and wound healing. The evaluation of the in vitro cytotoxicity of a biomaterial is often a qualitative analysis based on the morphological examination of cell damage and growth after direct or indirect contact with the material. Different commercial assays based on the determination of nucleic acids, metabolic activity, protein content or membrane integrity are available to measure cell proliferation and cell viability. A small selection – Pico Green(®) DNA Cell Proliferation Assay, ATPLite™ Luminescence ATP Detection Assay, BC Assay: protein quantitation kit, AlamarBlue™ Proliferation Assay and Live/Dead Staining with SYTO-13 and EthD-2 – are discussed concerning sensitivity, reliability and applicability.