Cell Membrane Related Cytotoxicity and Dependency on Methacrylate Monomer Structure

The importance of acrylates in dental materials requires analysis of potential untoward effects on cell membranes. Objective: To evaluate the cytotoxicity of meth/acrylate monomers at the level of cell membrane. Method: mouse fibroblast cells (ATCC CCL1 clone L929) were seeded in 96-well plates. A confluent population of ~200,000 cells/well was exposed to several concentrations of a monomer for 24hr at 37^oC/5%CO₂ and cell viability was measured using the neutral red dye (NR) (50-ug/well).  Monomers were tested in DMSO or Ethanol (0.1-0.4% in medium). The concentration that reduced 50% cellular uptake of NR (IC₅₀) was extrapolated from concentration vs %OD₅₅₀ curves. Results: TC₅₀ values obtained are tabulated below (lowest most cytotoxic) along with permeability coefficients (Kp, cm/hr) calculated with the Potts and Guy Equation. TC₅₀ values were compared by ANOVA followed by Bonferroni Post Hoc tests (α =0.05) with significantly different values between the acrylates and methacrylates.   

Conclusions: Methylation of the acrylate moiety (4-6) significantly reduces cytotoxicity compared to non-methylated (1-3), which effect is dependent on membrane permeability.  Hydroxylation has a small effect on the already cytotoxic acrylates.  Increase in hydrophilicity via hydroxylation, however, attenuated the reduction in cytotoxicity of the methylated acrylate moiety substantially (4-5 vs.6).  Since this effect is related to membrane permeability further studies are justified to explore the chemically dependent differences on membranes at the molecular level.  Study supported by NIH/NIDCR grant DE14379-01A2.jcuqh3@umkc.edu