Uv vis spectrometer

The pH-responsive characteristics of the MnAs-ICG nanospike were evaluated using TEM and in vitro release in PBS buffer at different pH conditions. First, MnAs-ICG was added to PBS at pH 6.2 and 5.0. At the selected time, the solution was collected for observation of morphological changes using TEM. Then, the release of ICG and As from MnAs-ICG at different pH values and photothermal treatments was measured by dialysis bag. Briefly, MnAs-ICG (ICG: 100 μg) was suspended in a dialysis bag (MWCO = 3500 Da), immersed in 10 mL of PBS (pH 7.4, 6.2, or 5.0), and incubated at 37 °C with constant stirring. Then, 1 mL of PBS was collected at specific time intervals, and the released As and ICG was measured according to the standard curve of As and ICG using ICP-MS (Thermo Electron Corporation) and UV–Vis spectrometer (Molecular Devices), respectively.

To measure cellular tyrosinase activity, the same amounts of cell lysates (10 μg) were incubated with 10mM L-dihydroxyphenylalanine (L-DOPA; pH 6.8; Sigma) at 37°C for 1 h. The amount of melanin calculated from L-DOPA via the tyrosinase activity in the cell extracts was measured using a UV–Vis spectrometer (Molecular Devices, Sunnyvale, CA, USA) at 490 nm. To determine the cellular melanin levels, the cell pellets were dissolved in 50 μL of 1N sodium hydroxide, and the melanin levels were determined by measuring the absorbance at 490 nm. The melanin levels were normalized to the protein input of samples.