Bifunctional Gold Nanobipyramids for Photothermal Therapy and Temperature Monitoring

To realize a real-time thermal feedback, monitoring the temperature of the treated tissue is critical for photothermal therapy (PTT). The poor spatial resolution and low accuracy of current methods for the detection of tissue temperature limits the application of PTT. Herein, by assembling the temperature-responsive DNA stem-loop marked with Texas red (TR) onto the surface of gold nanobipyramids (AuNBPs), a bifunctional reagent (AuNBPs-DNA-TR) was fabricated for PTT and synchronously monitoring the temperature. In this configuration, the AuNBPs not only have a high efficiency for photothermal conversion but also could be quenchers to inhibit the fluorescence of TR. During PTT, the significant photothermal effect of the AuNBPs could elevate the temperature. Meanwhile, the increase of the temperature could open the DNA stem-loop assembled on the AuNBPs and as a result enlarge the distance between the TR and AuNBPs. As a result, the TR fluorescence quenched by the AuNBPs was sensitively recovered. The fluorescence intensity (FI) of the TR could be utilized to monitor the temperature during PTT. It was found that irradiating the cancer cells cultured with the AuNBPs-DNA-TR with an 808 nm laser could distinctly increase the system temperature, while the cells could be inactivated due to the remarkable photothermal effect of the AuNBPs-DNA-TR. Meanwhile, the fluorescence of the AuNBPs-DNA-TR for the measurement of the temperature was significantly enhanced. The results indicated that the variation of the fluorescence from the AuNBPs-DNA-TR could be used as thermal feedback to monitor the effect of PTT.