Dipeptide Surface Modification and Ultrasound Boosted Phosphatase-Like Activity of the Ceria Nanozyme: Dual Signal Enhancement for Colorimetric Sensors

The development of innovative nanozymes with superior enzyme-mimicking activities for colorimetric sensor applications has attracted substantial attention in recent years; however, their application has remained challenging in sensitive colorimetric detection owing to their low catalytic activities. The construction of a more efficient nanozyme-based catalytic system would therefore be expected to improve the detection sensitivities of colorimetric sensors. Herein, we report the development of a highly reactive phosphatase-like nanozyme (carnosine-modified nanoceria, CMNC) engineered by introducing distal imidazole-containing amino acid residues onto the nanoceria surfaces to mimic the reaction microenvironment of the native phosphatase. The obtained results showed that CMNC presented a significantly enhanced catalytic activity compared to the bare nanoceria, furthermore discovering that ultrasonic stimulation significantly enhanced the phosphatase-like catalytic performance of CMNC. Based on these findings, as a proof-of-concept demonstration, two ultrasensitive nanozyme-based colorimetric immunoassays were developed for quantifying the C-reactive protein and prostate-specific antigen. Benefiting from the surface modification and ultrasound-enhanced phosphatase-like activity of CMNC, this dual signal-enhancing strategy improved the performances of the corresponding colorimetric sensors, and an approximately 50-fold higher sensitivity was achieved compared to that of the bare nanoceria without ultrasonic irradiation. These results pave the way for the use of nanozymes in highly sensitive biosensors.