“…As previously reported, the cytotoxic effects of rGO nanocomposites were evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and neutral red uptake (NRU) assays. [52,53] Briefly, 2 Í 10 3 HaCaT cells per well were seeded in 96-well cell culture plates and exposed to TM@rGO or rGO for 24 h. After washing with phosphatebuffered saline (PBS, Gibco, USA) and exposure to rGO nanocomposites, an MTT solution (Sigma-Aldrich, USA) was added to each well at a final concentration of 0.5 mg mL −1 and the cells were incubated for 1 h. The formazan crystals formed during the process were dissolved in 50% dimethyl sulfoxide (DMSO) (Sigma-Aldrich, USA) and 50% methanol (Merck, USA). For the NRU assays, NP-exposed cells were washed twice with PBS and incubated for 3 h in OPTI-MEMI (Gibco, USA), which contained 40 ng mL −1 of neutral red reagent (Sigma-Aldrich, USA).…”