Dual-mode smart sensing of sarcosine by integrating nanozyme-mediated electrochemical and smartphone-readable colorimetric assays.

Sarcosine (Sar) detection plays a crucial role in the diagnosis and management of prostate cancer. We developed a dual-mode biosensing platform for the highly sensitive and specific quantification of Sar by integrating electrochemical and colorimetric detection. The sensor was fabricated using a nanocomposite consisting of riboflavin (Rf) and reduced graphene oxide nanoribbons (rGONRs), which served as a support for a bimetallic TCPP(Fe)-Zn metal-organic framework (MOF). The rGONRs significantly increased the active surface area and facilitated electron transfer, thereby enhancing the peroxidase-like activity of the TCPP(Fe)-Zn MOF. This catalytic activity promoted the oxidation of o-phenylenediamine (OPD) in the presence of HO generated via an Sar-specific oxidase-mimetic reaction mediated by Rf. The dual-mode design enabled Sar detection through both electrochemical signals and color changes, with the latter quantitatively analyzed via RGB measurements. Under optimized conditions, the sensor exhibited a broad linear range of 10.0-1000.0 μmol L for colorimetric detection, and 0.0010.001-500.0 μmol L for electrochemical detection, achieving detection limits of 2.0 μmol L and 0.04 nnmol L, respectively. The biosensor exhibited excellent reproducibility, stability, and selectivity, and was successfully applied to the human urine detection. The recovery obtained from healthy men and prostate cancer patients were 97.1 %-110.7 % and 98.7 %-104.4 %, respectively. This work presents a reliable, non-invasive tool for prostate cancer diagnosis with significant potential for point-of-care testing (POCT).