An inhibitory and stimulatory effect of naked (no PC) AuNP on the production of 16β-OH TST (a, b), 16β-OH TST (c, d) and AD (e, f) in pHLM. Data represent mean ± S.D. (n=3). IC50, half maximal inhibitory conc.; EC50, half maximal activation conc.; pHLM, pooled human liver microsomes; ND, not determined by fitting a Hill equation with variable slope to the observed data using GraphPad Prism®; PC, human plasma protein; BPEI, branched polyethylenimine; LA, lipoic acid; PEG, polyethylene glycol; Conc, concentration; 16α-OH TST, 16α-hydroxytestosterone; 16β-OH TST, 16β-hydroxytestosterone; AD, androstenedione.