Relative viability of primary rat hepatocytes at 24 hours on tissue culture polystyrene and chemically modified porous silicon with (+) and without (−) collagen adsorbed, quantified by ethidium homodimer-1 stain. Abbreviations for the control and the modified porous Si samples are indicated on the x-axis: polystyrene (PS), undecanoic acid (Ac), ozone-oxidized (Oz), oligo(ethylene) glycol (OEG), and dodecyl (Dod) modified. Cell viability studies were performed in cell media containing 10% FBS. Results are means ± standard error of the mean of three separate cell preparations.