Near-infrared light-triggered mild-temperature photothermal effect of nanodiamond with functional groups

There is still an urgent need to develop photothermal agents (PTAs) with stable photothermal stability and good biocompatibility, especially PTAs with functional groups for mild-temperature photothermal therapy (PTT). Herein, carboxylated nanodiamond (ND-COOH) was prepared by annealing of pristine nanodiamond (ND), and aminated nanodiamond (ND-PEI) was further synthesized by grafting ethylenediamine-branched polyethylenimine to ND-COOH. The mild-temperature photothermal effect of these NDs was certified. The photothermal conversion efficiency of the NDs was calculated to be ~20%, and the photothermal properties were stable for the NDs with the functional groups, which supplies possibility to further modify NDs as mild-temperature photothermal nanoplatforms. In vitro antibacterial experiments showed that almost all of the bacteria (>99%) co-cultured with NDs at concentration of 200 μg/mL and 150 μg/mL to S. aureus and to E. coli were killed after 808 nm irradiation for 10 min, respectively. 4T1 cells, mouse breast cancer cells, co-cultured with 200 μg/mL NDs under irradiation 10 min were ablated about 40%. Meanwhile, NDs showed no cytotoxicity and excellent biocompatibility. Therefore, NDs can be used as mild-temperature PTAs by near-infrared light-triggering, and NDs with functional groups will be new promising nanoplatforms which may inspire many new progresses in the field of mild-temperature PTT.