730 nm Light-Induced Cleavage of BODIPY Photocages via Entropy-Driven Triplet Sensitization

Abstract

<p>Light-activated drug delivery systems allow precise spatiotemporal control of a drug release process. However, safe and efficient drug release activation needs a low-power nonpulsed red/near-infrared light with high tissue penetration depth. Nevertheless, such systems remain a challenge. Herein, a self-assembled nanovehicle made of 2,6-diiodo-B-dimethyl-boron dipyrromethene (BODIPY)-based photocleavable trigonal molecules bearing Pt(II) meso-tetraphenyltetranaphthoporhyrin photosensitizer and a fluorescent release marker Nile Red in hydrophobic core is introduced. The system employs endothermic triplet–triplet energy transfer between the photosensitizer and the trigonal molecule, leading to the cleavage of the trigonal molecule followed by cargo release. This allows to engage 730 nm light to cleave BODIPY photoremovable protecting groups (PPGs) instead of 530 nm light that would be needed for direct photocage excitation. Therefore, the approach unleashes the desired activation of drug release via photocleavage with longer wavelengths (within the phototherapeutic window) without any chemical modification of the PPGs. Cell studies demonstrate fast intracellular uptake of the nanovehices by PC3 human prostate cancer cells with accumulation in lysosomes in 2 h. Light irradiation at 730 nm on nanovehicles dispersed in cell media leads to payload release. Remarkably, the system exhibits higher release efficiency at low oxygen concentration than at ambient thus allowing to tackle aggressive hypoxic solid tumors.</p>