Construction of hollow double shell NiMn PBA nanozymes for sensitive sarcosine detection via a cascade strategy

Abstract

As a significant biomarker for the early development of prostate cancer (PCa), the sensitive detection of sarcosine (SA) in urine can serve as an effective non-invasive early warning method. Herein, we developed novel a hollow double shell NiMn PBA (NiMn-PBA-DSNB) with outstanding peroxidase-like activity through a facile cation exchange reaction according to the distinct solubility product constants (Ksp) of different Prussian blue analogues (PBAs). Moreover, we have innovatively proposed a “enzyme - nanozyme” cascade strategy to realize ultrasensitive SA sensing. This system utilized the enzymatic reaction between SA and sarcosine oxidase (SOX) to generate H2O2 in situ. In the presence of the generated H2O2, the NiMn-PBA-DSNB nanozyme can efficiently catalyze the oxidation of 3, 3’, 5, 5’-tetramethylbenzidine (TMB) to produce the blue oxTMB. Consequently, the concentration of SA directly correlated with the absorbance value of oxTMB, providing a quantitative detection. Based on this dual-enzyme cascade mechanism, a highly sensitive colorimetric assay was developed for the precise analysis of SA. The assay achieved a wide linear range from 8 to 500 μM, with a low detection limit of 1.75 μM, fully fulfilling the requirements for SA sensing in the urine of PCa patients. The method was also successfully applied to the analysis of real human urine samples, achieving recoveries ranging from 102.15% to 104.35% with relative standard deviations ≤ 5.03%, which demonstrates its strong potential for clinical application.