Visualization of photothermal therapy by semiconducting polymer dots mediated photoacoustic detection in NIR II

Visualization of photothermal therapy mediated by photothermal transduction agents (PTAs) is important to promote individual treatment of patients with low side effects. Photoacoustic detection has emerged as a promising noninvasive method for the visualization of PTAs distribution but still has limitations in temperature measurement, including poor measurement accuracy and low tissue penetration depth. In this study, we developed biocompatible semiconducting polymer dots (SPD) for in situ coupling of photothermal and photoacoustic detection in the near-infrared II window. SPD has dual photostability under pulsed laser and continuous-wave laser irradiation with a photothermal conversion efficiency of 42.77%. Meanwhile, a strong correlation between the photoacoustic signal and the actual temperature of SPD can be observed. The standard deviation of SPD-mediated photoacoustic thermometry can reach 0.13 °C when the penetration depth of gelatin phantom is 9.49 mm. Preliminary experimental results in vivo show that SPD-mediated photoacoustic signal has a high signal-to-noise ratio, as well as good performance in temperature response and tumor enrichment. Such a study not only offers a new nanomaterial for the visualization of photothermal therapy but will also promote the theranostic platform for clinical applications.