Photothermal agents with high photothermal transfer efficiencies in the near-infrared (NIR) region are important for enhanced
photothermal therapy (PTT) of
tumors. Herein, we developed a strategy for the
acid-triggered in situ aggregation of a system based on
peptide-conjugated
gold nanoparticles (GNPs). In an acidic environment, the GNPs formed large aggregates in
solution, in cell lysates, and in
tumor tissues, as observed by transmission electron microscopy (TEM). As a consequence of the aggregation, their UV-vis absorbance in the NIR region was greatly increased, and
laser irradiation of the GNPs resulted in a dramatic increase in the temperatures of solutions and
tumors that contained the GNP system. When exposed to NIR irradiation, the aggregates formed by the GNP system under acidic conditions were capable of producing a sufficient level of
hyperthermia to destroy
cancer cells both in vitro and in vivo. Interestingly, the GNP aggregates showed enhanced properties in multiple imaging modalities, including computed tomography (CT), photoacoustic (PA), and photothermal (PT) imaging. Thus, we have developed a novel probe for enhanced multimodal
tumor imaging. These findings prove that a strategy involving the
acid-triggered in situ aggregation of a GNP system can increase the photothermal transfer efficiency for low to high energy conversion, thus boosting the therapeutic specificity and antitumor efficacy of PTT and facilitating multimodal imaging.