A near-infrared and lysosomal targeting thiophene-BODIPY photosensitizer: Synthesis and its imaging guided photodynamic therapy of cancer cells

Abstract

In this study, a novel NIR and lysosomal targeting thiophene-BODIPY photosensitizer SBOP-Lyso was synthesized to explore its potential applications in photodynamic therapy of A549 cells. In the strategy of designing SBOP-Lyso, S atom in thiophene as well as heavy atom I were introduced to promote ISC efficiency to ensure high singlet oxygen yield. A common lysosome targeted group (M1: 1-(2-morpholinoethyl)-1H-indole-3-carbaldehyde) was linked to SBOP to extend its wavelength to the NIR region. Its absorption peak was at 660 nm (εmax = 5.2 × 104 cm−1 M−1) and its corresponding emission peak was located at 705 nm. Singlet oxygen could be quickly generated by SBOP-Lyso in the presence of 660 nm LED irradiation and the singlet oxygen yield was up to 44.1%. In addition, it also had good biocompatibility and could enter cells or zebrafish in a short time. SBOP-Lyso had negligible dark cytotoxicity (cell survival rate > 80%) and excellent phototoxicity (IC50 = 0.2 μM). DCFH-DA (ROS indicator) proved that SBOP-Lyso could generate singlet oxygen with 660 nm LED irradiation. Singlet oxygen produced by SBOP-Lyso could kill cancer cells in PDT process and it had the ability to effectively inhibit A549 cells migration. Besides that, lysosomal colocalization assay showed that it had good lysosomal localization ability (Pearson colocation coefficient, R = 0.93). Considering the above results, SBOP-Lyso as a unique lysosome-targeted photosensitizer with excellent properties would exhibit positive results in PDT process of cancer cells.