3.2. Photothermal effect of OHH NPs
Due to the strong NIR absorption of OHH NPs, the photothermal effect of OHH NPs under an 808 nm NIR light irradiation was systematically assessed.34-35 As seen in Fig. 2A, the increased temperature (∆T) of HMPB NPs and OHH NPs solution was up to ∼25 °C after irradiation with an 808 nm NIR laser at a power density of 1 W/cm2 for 10 min, whereas it was only ∼4.7 °C and ∼4.9 °C for pure water and ofloxacin, respectively. The negligible difference of temperature increment between HMPB NPs and OHH NPs suggested that ofloxacin loading and HA modification didn’t influence the photothermal property of HMPB NPs. Simultaneously, the real-time photothermal images of Fig. 2B intuitively exhibited the discrepancy of photothermal ability of different nanoparticals. Fig. 2C and Fig. 2D confirmed that the temperature increase of OHH NPs could be precisely tuned by the concentration of OHH NPs and laser intensity. Besides, the previously reported equation37 was used to measure the photothermal conversion efficiency (Fig. 2E). It could be calculated that OHH NPs possessed a relatively high photothermal conversion efficiency of 27.13%. According to five heating-cooling cycles without obvious temperature decrease, it could be concluded that OHH NPs possessed the high photostability stability (Fig. 2F). All the aforementioned results implied that OHH NPs could be utilized to be an excellent photothermal agent for photothermal therapy(PTT).