Photoacoustic-guided photothermal therapy by mapping of tumor microvasculature and nanoparticle

Although photothermal therapy (PTT) has demonstrated its clinical value and adaptability, it still requires imaging guidance to motivate the development of precise and effective treatment. For PTT, high-resolution visualization of tumor microvasculature and accurate location of nanoparticles distribution are crucial for the therapeutic outcome. Here, a wavelength-switchable photoacoustic microscopy (PAM) was developed to noninvasively investigate the tumor microvasculature and the accumulation of nanoparticles for accurately guiding PTT and evaluating the therapeutic effect. In a tumor model, PAM was used to continuously monitor the tumor microenvironment in vivo, and the proportion of microvessels in tumor site was found increased by 10%, and the diameters of the draining veins were doubled on day 7. In addition, quantitative parameters such as tumor volume and vascular density can also be demonstrated by the PAM. Meanwhile, the concentration of Den-RGD/Cy7 at the tumor site reached its maximum at 8 h by PA mapping after intravenous injection, which was used to determine the optimal irradiation timing. After treatment, photoacoustic monitoring showed that PTT can precisely kill the tumors and minimize damage to surrounding normal tissues, which was consistent with the pathological slides. The experimental results proved that PAM can provide an auxiliary means for precision PTT.