METHODS FOR THE EVALUATION OF BIOCOMPATIBILITY OF SOLUBLE SYNTHETIC-POLYMERS WHICH HAVE POTENTIAL FOR BIO-MEDICAL USE .1. USE OF THE TETRAZOLIUM-BASED COLORIMETRIC ASSAY (MTT) AS A PRELIMINARY SCREEN FOR EVALUATION OF INVITRO CYTOTOXICITY

A tetrazolium-based colorimetric assay (MTT) was first introduced by Mossman in 1983 to assess the potential of novel antitumour agents, and it has been used here to evaluate the cytotoxicity of several soluble synthetic polymers proposed as drug carriers. Polymers including poly-L-lysine (molecular weight 57 000) were incubated (up to 1 mg ml-1) with two human cell lines, hepatocellular carcinoma (HepG2) and lymphoblastoid leukaemia (CCRF), adherent and suspension cells, respectively. Tests were carried out in the presence and absence of serum proteins. The assay was first modified to optimize the colorimetric profiles produced by the cell lines following incubation with MTT, to increase both the test sensitivity and the reproducibility of the method. Polymer toxicity observed using the MTT test was compared with data obtained using other methods; [H-3]thymidine or [H-3]leucine incorporation and counting cell numbers. Poly-L-lysine was very toxic to both cell lines with approximate IC50-values of 60 and 30-mu-g ml-1 for HepG2 and CCRF, respectively, the values obtained being similar for each of the three different viability methods used. In the absence of serum proteins the toxicity of poly-L-lysine increased, the IC50-values falling to 25.5-mu-g ml-1 for the adherent and 0.8-mu-g ml-1 for the suspension cell line. Other polymers such as poly-L-proline, polyethylene glycol, dextran, polyvinylpyrrolidone and poly-L-glutamic acid were not cytotoxic (MTT assay), either in the presence or in the absence of serum proteins. The MTT assay is a useful technique for the primary and rapid evaluation of the cytotoxicity of soluble polymers.