Photocleavable luminescent conjugates of 2-(2-aryl-5-(piperidin-1-yl)-2H-1,2,3-triazol-4-yl)thiazoles and aminoacids, diagnostics and drugs

Abstract

Photocleavable protective groups (PPGs) offer a straightforward method of temporarily masking the aggressive functions of organic compounds and inactivating biologically active or toxic substrates. The active species can then be released from their photoactivatable precursors in a controlled manner upon exposure to light. In this study, we present a series of photocages based on the novel fluorescent scaffold 2-aryl-2H-1,2,3-triazol-4-yl-thiazoles (ATTs), incorporating proteinogenic amino acids, the biologically active compound biotin, the anticancer agent melphalan, and model compounds such as aromatic acids. Studies of photodegradation under various conditions using mass spectrometry, spectral and kinetic analyses, and quantum mechanical calculations have shown that acid release from the photoconjugates (ATT-PCs) depends on fluorophore fragment structure, acid nature, and the presence of air, water or a phosphate buffer solution (pH of 7.4), as well as the light source power and λ_ir. The release of acid during photodissociation was confirmed through high-resolution mass spectrometry and biological experiments, including the MTT assay and the imaging of Vero cells incubated with ATT-PCs, utilising a confocal scanning microscope. The photorelease mechanism was explored using both experimental studies and quantum mechanical calculations, which revealed that the properties and reactivity of this photosystem are predominantly influenced by the transition to the triplet state. Additionally, the findings indicated that ATT-PCs effectively absorb light in the visible spectrum and exhibit intense fluorescence, even in a DMSO–PBS mixture at a 1 : 9 ratio. Furthermore, ATT-PCs can function as photosensitisers, capable of generating reactive oxygen species (ROS). Cell studies demonstrate the rapid intracellular uptake of ATT-PCs by Vero cells, with accumulation in the endoplasmic reticulum (ER) or lipid droplets within a 0.5-hour incubation period.