Application of melatonin-loaded poly(N-isopropylacrylamide) hydrogel particles to reduce the toxicity of airborne pollutes to RAW264.7 cells.

The adverse effect of airborne PM2.5 pollutes on human beings and the environment, most likely due to heavy metal leaching, has received extensive attention recently. It is urgently required to develop a simple and effective method to suppress the toxicity of PM2.5 pollutes. In this study, the heavy metal content of PM2.5 pollutes around Zhejiang university were firstly identified. Their cytotoxicity was confirmed, by inducing significantly enhanced intracellular reactive oxygen species level. Poly(N-isopropylacrylamide) (PNIPAM) submicron hydrogel particles with tunable crosslinking densities and thermo-responsive swelling/shrinking properties were then prepared by adjusting the crosslinking density. Anti-oxidant drug melatonin (MLT) was encapsulated into the obtained PNIPAM nanogel particles with the drug loading efficiency larger than 50%, achieving thermo-responsive drug release profile. The PNIPAM/MLT particles had a strong ability to reduce the cytotoxicity to Raw264.7 cells induced by the extractant of PM2.5 pollutes, as well as to suppress the intracellular reactive oxygen species (ROS) level and secretion of tumor necrosis factor alpha (TNF-α), especially when the cells were treated under 25°C for 3h after ingestion of the PNIPAM/MLT particles. This concept-proving study demonstrates the potential to use the thermo-responsive PNIPAM/MLT particles to suppress the toxicity of airborne PM2.5 pollutes, which is a paramount requirement for human health.