Comparative study of a new composite biomaterial fluor-hydroxyapatite on fibroblast cell line NIH-3T3 by direct test

The number of biomaterials used in biomedical applications has rapidly increased in the past two decades. Fluorapatite (FA) is one of the inorganic constituents of bone or teeth used for hard tissue repairs and replacements. Fluor-hydroxyapatite (FHA) is a new synthetically prepared composite that in its structure contains the same molecular concentration of OH⁻ groups and F⁻ ions. The aim of this experimental investigation was to use the embryonal mouse fibroblast cell line NIH-3T3 for comparative study of basal cytotoxicity of fluoridated biomaterials FHA and FA discs. Hydroxyapatite (HA) disc, high-density polyethylene as negative control and polyvinyl chloride (PVC) containing organotin stabilizer as positive control were used as standard biomaterials. The appropriateness of the use of NIH-3T3 cells and their sensitivity for tested biomaterials were evaluated on the basis of five cytotoxic end points: cell proliferation, cell morphology, lactate dehydrogenase (LDH) released, protein and DNA cell content. The basal cytotoxicity of FHA, FA and HA discs was measured by direct contact method. FHA composite, FA and HA demonstrated in cell line NIH-3T3 nearly similar basal cytotoxicity increasing with the time of treatment. After 72 h of biomaterials treatment, about 25% inhibition of cell number, unchanged morphology of dividing cells, 6.31–0.16% increase of released LDH, about 10% inhibition of cell protein content and about 20% inhibition of DNA content was found. On the other hand, from the growth rates it resulted that NIH-3T3 cells, affected by tested biomaterials, divided about 20% slowlier than the control (untreated cells). Using the linear regression analysis we found out that deviations in measurements of cytotoxicity by four methods were as follows: less than 10% for cell number, protein and DNA content methods and 12.4% for released LDH method. Based on a good correlation of the cytotoxicity of biomaterials obtained from all end points we could conclude that fibroblast NIH-3T3 cell line was appropriate for measuring the basal cytoxicity of tested biomaterials.