D-A-D structured selenadiazolesbenzothiadiazole-based near-infrared dye for enhanced photoacoustic imaging and photothermal cancer therapy

Near-infrared(NIR)small molecular organic dyes as photothermal agents for cancer photothermal therapy(PTT)have attracted considerable research attention.Herein,two donor-acceptor-donor(D-A-D)structured NIR dyes,BBTT and SeBTT,are rationally designed,where the only difference is one heteroatom within the acceptor unit varying from sulfur to selenium(Se).More importantly,SeBTT NPs exhibit stronger NIR absorbance and higher photothermal conversion efficiency(PTCE≈65.3%).In vivo experiments illustrate that SeBTT NPs can be utilized as a high contrast photoacoustic imaging(PAI)agent,and succeed in tumor suppression without noticeable damage to main organs under NIR photoirradiation.This study presents an effective molecular heteroatom surgery strategy to regulate the photothermal properties of NIR small molecules for enhanced PAI and PTT.

Boron difluoride formazanate dye for high-efficiency NIR-Ⅱ fluorescence imaging-guided cancer photothermal therapy

The small molecular second near-infrared(NIR-Ⅱ, 1000–1700 nm) dye-based nanotheranostics can concurrently combine deep-tissue photodiagnosis with in situ phototherapy, which occupies a vital position in the early detection and precise treatment of tumors. However, the development of small molecular NIR-Ⅱ dyes is still challenging due to the limited electron acceptors and cumbersome synthetic routes.Herein, we report a novel molecular electron acceptor, boron difluoride formazanate(BDF). Based on BDF, a new small molecular NIR-Ⅱ dye BDF1005 is designed and synthesized with strong NIR-I absorption at 768 nm and bright NIR-Ⅱ peak emission at 1034 nm. In vitro and in vivo experiments demonstrate that BDF1005-based nanotheranostics can be applied for NIR-Ⅱ fluorescence imaging-guided photothermal therapy of 4T1 tumor-bearing mice. Under 808 nm laser irradiation, tumor growth can be effectively inhibited. This work opens up a new road for the exploitation of NIR-Ⅱ small molecular dyes for cancer phototheranostics.