ANDREI MARIAN FEIER, DOINA RAMONA MANU, GABRIELA STRNAD, MINODORA DOBREANU, OCTAV MARIUS RUSSU, DIANA PORTAN, TIBERIU BATAGA A STEP FORWARD STANDARDIZATION OF BIOCOMPATIBILITY TESTING ON TISSUE CULTURE POLYSTYRENE Standard procedures regarding osteoblast cells deposition on different subtrates to test the biocompatibility of materials are not available. Aspects related to cells morphology depending on their number on the surface area of the substrate were studied for the first time. Osteoblasts were successfully isolated from residual bone resulted from two different patients after total hip arthroplasty. Different numbers of osteoblasts in populations (3x104 cells/cm2, 6x104 cells/cm2, 1x105 cells/cm2) were deposited on tissue culture polystyrene for 7 and 10 days of incubation. Results suggested that the protocol of osteoblasts deposition should be adjusted to assure a fair distribution of cells on the entire available area of the substrate, possible if a very good dispersion in the medium is achieved prior to deposition. Some other key factors in cells appropriate development, such as substrate nature, topography and incubation time,were detected. The present investigation helps declaring specific standards with respect to the biocompatibility testing of materials using osteoblast populations. Further investigations may lead to the creation of databases and the establishment of standards regarding bicompatibility researches that involve osteoblasts populations.