Polydopamine Nanocarriers Loading and Release of Curcumin

The UV absorption spectrum of polydopamine has a broad spectrum, with absorption in the range of 400–800 nm, but no clear absorption peak, while curcumin has a maximum UV absorption peak at 425 nm. Therefore, the experiment was designed to calculate the loading effect of polydopamine nanocarriers on curcumin by measuring the change of UV absorption value at 425 nm wavelength of the loading system. Three beakers were taken, and 30 mL of curcumin working liquid (8 μg mL⁻¹) was measured in two beakers, and 30 mL of distilled water was measured in the other beaker as the control group. The beakers were placed in a magnetic stirrer and stirred at a constant speed. Add 10 mg of the above-mentioned prepared polydopamine nanoparticles into three beakers and stir them fully and continuously in the curcumin working liquid system. Collect 4 mL of each experimental group every 1 h. After centrifugation, the supernatant is tested for 425 nm absorption value. The loading and loading percentage of polydopamine nanocarriers on ginger were calculated until there was no significant change in light absorption value measured for 3 consecutive times (loading plateau period). After that, the prepared PDA-Cur NPs were purified, the unstable load of curcumin was fully washed away for analysis, and then characterized and used for backup. For curcumin releasing measurement, PDA-Cur NPs was dialyzed in PBS buffer at pH 6.0 in dark and kept in a 37 °C water bath. At different time points (1, 2, 4, 8 and 16 h), curcumin released from PDA-Cur NPs was collected. The size distribution and polydispersity index of PDA-Cur NPs were determined by dynamic light scattering (DLS) measurements (Nano ZS90, Malvern Instruments, UK).