Rational Design of a Hydrophilic Perovskite Ultraviolet Photocatalyst for Mediating a Sensitive and Controllable Nucleic Acid Assay

CsPbX3 perovskites are emerging photocatalysts with promising biosensing applications, yet designing highly active ultraviolet photocatalysts and clarifying their photocatalytic mechanism in the aqueous phase remain challenging. This study reveals the oxidase-like activity of hydrophilic CsPbX3 nanoparticles (NPs) under ultraviolet light (UV-OXD-like activity), wherein soluble oxygen is catalyzed into singlet oxygen (1O2), leading to rapid oxidation of the chromogenic substrate within seconds. Halogen atoms and doped metal ions can significantly influence the band structure of the CsPbX3 NPs. Among these, Cl atoms endow a wide bandgap (∼3.0 eV) favorable for UV absorption of CsPbX3 NPs, while the deep trap states introduced by Bi3+ promote nonradiative recombination, thus enabling Bi3+:CsPbCl3 NPs to have excellent UV-OXD-like activity. Notably, ascorbic acid (AA) formed by alkaline phosphatase (ALP)-catalyzed hydrolysis of the substrate can passivate deep trap states through hydrogen bonding. The presence of the target nucleic acid activates the trans-cleavage activity of LbCas12a, releasing ALP from magnetic beads. Accordingly, an enzyme cascade reaction coupled with a UV-controlled readout is proposed for the BRAF V600E assay with a low limit of detection (0.10 pM, preamplification-free) and applied to human thyroid cancer tissue samples. This work provides a perspective for the design and bioapplication of hydrophilic perovskite-based UV photocatalysts.