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).