Dimethylamino-Functionalized\nBODIPY Nanoparticle Enhances\nNear-Infrared Fluorescence Imaging and Photothermal Therapy

Organic dyes have been widely used in bioimaging, molecular\nprobes,\nimaging in vivo, and phototherapy. However, it is still a major challenge\nto improve the imaging and therapeutic properties of organic dyes.\nIn this work, boron dipyrromethene (BODIPY) nanoparticles (NPs) were\nsynthesized with poly(ethylene glycol)<sub>2k</sub>-<i>block</i>-poly(d,l-lactide)<sub>2k</sub> (PEG–PLA)\nNPs for tumor microenvironment response, near-infrared fluorescence\n(NIRF) imaging with a high signal-to-noise ratio (SNR), and photothermal\ntherapy (PTT). The absorption and fluorescence spectra of the obtained\nBDP changed as the pH decreased. The introduction of a dimethylamino\ngroup enhanced the photothermal conversion efficiency and imaging\ncapability of BODIPY-loaded PEG–PLA NPs (BDP NPs). After injection\ninto mice, these NPs showed excellent photothermal efficacy toward\nhepatoma and papillary thyroid cancer. Additionally, BDP NPs could\nbe used for NIRF imaging with a high SNR after BODIPY was modified\nwith a dimethylamino group. This work highlights that molecular engineering\ncan enhance the luminescence and photothermal properties of dyes and\nthat BDP NPs are excellent theranostic agents.