Methylcellulose cell culture as a new cytotoxicity test system for biomaterials

The cytotoxicity of biomaterials can be testedin vitro using various culture systems. Liquid culture systems may detect cytotoxicity of a material either by culture of cells with extracts or with the material itself. In the latter instance, renewing the medium will remove possible released cytotoxic products. The agar-overlay test is a short term semi-solid culture system in which the possible cytotoxicity of biomaterials is identified only by the presence of cell free zones. The aim of this study was to develop a more sensitive cytotoxicity test system for biomaterials, using methylcellulose as a culture gel, mixed with human fibroblasts. The main advantage of the test system is the possibility of evaluating cytotoxicity for a period of up to seven days without renewal of the culture gel. Furthermore it is possible to both quantitatively evaluate by counting absolute cell numbers and to qualitatively evaluate by studying cell morphology with light- and/or electron microscopy. Processed dermal sheep collagen was selected as test material, since contradictory results concerning the cytotoxicity of its extracts have been reported by others [2, 15, 18, 19]. Using our test system, both primary and secondary cytotoxic effects were found. Primary cytotoxicity is due to direct leakage of products from the material, detected by testing, extracts of the collagen or the collagen itself. Secondary cytotoxicity is due to release of cytotoxic products resulting from cell-biomaterial interactions. We conclude that our test system is extremely useful to test materials which are suspected of primary and/or secondary cytotoxicity, either with slow release of cytotoxic products or release of products with late cytotoxic effects.