Highly Stable Organic Photothermal Agent Based on Near-Infrared-II Fluorophores for Tumor Treatment

Abstract

Background: To develop highly stable near-infrared (NIR) photo-induced tumor therapy agent has obtained considerable role for biological application. With longer wavelength, biological imaging exhibits high signal-to-background ratio, deep tissue penetration and maximum permissible light power, and photoinduced tumor therapy can reduce damage minimization to organism.Results: A class of stable NIR-II fluorophores (NIR998, NIR1028, NIR980, NIR1030 and NIR1028-S) based on aza-BODIPY dyes with donor-acceptor-donor structures have been rationally designed and synthesized via utilizing steric relaxation effect and intramolecular photoinduced electron transfer (IPET). These fluorophores exhibit superior stability against photobleaching, NIR-II emission, large Stokes shift (≥ 100 nm) and excellent photothermal conversion performance. Among them, NIR998 with better near-infrared-II emission and higher temperature increase was utilized to prepare NIR998 nanoparticles (NIR998 NPs) by lipidosome encapsulation. NIR998 NPs show super stability in the presence of light, heat, reactive oxygen nitrogen species than that of ICG NPs, as well as high photothermal conversion ability (η = 50.5%). Finally, under the guidance of photothermal imaging, NIR998 NPs with negligible cytotoxicity have effectively eliminated tumors by their excellent photothermal conversion performance.Conclusions: Utilizing IPET and steric relaxation effect can effectively fulfill NIR-II emission of aza-BODIPY dyes and super stable NIR998 NPs with excellent photothermal conversion performance and negligible dark cytotoxicity can act as potential photothermal agents for biological applications.