Au@Pt Nanoparticles as Catalysts for the Detection of Holotranscobalamin as a Biomarker for Vitamin B12 Deficiency

Early detection of vitamin B12 deficiency is critical in the prevention of irreversible neurological damage caused by anemia. Therefore, a dual-mode colorimetric/electrochemical strategy was proposed for the quantification of holotranscobalamin. Urchin-like Au@Pt nanocatalysts (peroxidase-mimicking nanozymes) were synthesized and found to be catalytically superior to the traditional peroxidase enzyme. Further, the nanocatalyst-antibody conjugate was prepared and used as a signal transduction probe for delivering dual signal outputs, both electrochemical and colorimetric. In colorimetric detection, the nanozyme catalyzes the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB)-hydrogen peroxide (H2O2) system in the presence of holoTC, while in electrochemical detection, the impedance signal of the anti-holoTC/Au@Pt/FTO was enhanced and exhibited LODs of 0.036 pg mL–1 and 0.61 pg mL–1, respectively. The improved sensing performance of the sensor is attributed to the nanoscale architecture of the material, as confirmed through TEM and DLS. For real-world application, the method successfully detected holoTC in human serum samples. Hence, this study presents a strategy for clinical diagnosis of vitamin B12 deficiency, as it is the first dual-mode assay for the detection of holoTC.