One-pot synthesized citric acid-modified bimetallic PtNi hollow nanospheres as peroxidase mimics for colorimetric detection of human serum albumin

The combination of Pt with low-cost transition metal is an effective way to diminish the bulk utilization of costly Pt and to design new nanostructured materials with improved enzyme-like activity. In the present work, citric acid-functionalized platinum–nickel hollow nanospheres ([email protected] hNS) were synthesized through a simple one-pot wet chemical method, which involves the galvanic replacement reaction between the Ni nanoparticles and the Pt precursor that leads to the formation of hollow nanostructures. Transmission electron spectroscopic images revealed the uniformity of the [email protected] hNS, with an average diameter of 10.3 ± 2 nm. Moreover, zeta potential, FTIR, and XPS measurements confirmed the existence of citric acid in the [email protected] hNS. During synthesis, the use of citric acid not only facilitates monodispersity but also provides a negative surface charge (−11 mV) to the [email protected] hNS that electrostatically attracts the 3,3′,5,5′-Tetramethylbenzidine (TMB) substrate. As-prepared [email protected] hNS possessed excellent peroxidase-like activity due to rich Pt surfaces, large surface area, and heterogeneous interaction between Pt and Ni atoms. Furthermore, a nanozyme-linked immunosorbent assay (NLISA) for human serum albumin (HSA) detection was developed by replacing the enzyme in a standard enzyme-linked immunosorbent assay with [email protected] hNS. The [email protected] hNS based-NLISA showed sensitive detection of HSA concentrations ranging from 0 to 400 ng mL−1 with a LOD of 0.19 ng mL−1 and an average of 112% recovery of HSA from the spiked human plasma samples. The outcomes of the present study confirm the applicability of [email protected] hNS as substitutes for natural enzymes.