Novel Application of NIR-I-Absorbing Quinoidal Conjugated Polymer as a Photothermal Therapeutic Agent

Abstract

Conjugated polymer nanoparticles (CP NPs) that could absorb the first near-infrared (NIR-I) window have emerged as highly desirable therapeutic nanomaterials. Here, a quinoidal-conjugated polymer (QCP), termed PQ, was developed as a novel class of therapeutic agents for photothermal therapy (PTT). Owing to its intrinsic quinoid structure, PQ exhibits molecular planarity and π-electron overlap along the conjugated backbone, endowing it with a narrow band gap, NIR-I absorption, and diradical features. The obtained PQ was coated with a poly(ethylene glycol) (PEG) moiety, affording nanosized and water-dispersed PQ nanoparticles (PQ NPs), which consequently show a high photothermal conversion efficiency (PCE) of 63.2%, good photostability, and apparent therapeutic efficacy for both <i>in vitro</i> and <i>in vivo</i> PTTs under an 808 nm laser irradiation. This study demonstrates that QCPs are promising active agents for noninvasive anticancer therapy using NIR-I light.