Hollow Ruthenium Nanoparticles with Enhanced Catalytic Activity for Colorimetric Detection of C-Reactive Protein

Hollow structures can improve the physical and chemical characteristics of nanoparticles. In the present work, we synthesized hollow ruthenium nanoparticles (HRNs) using a galvanic replacement reaction. Compared to normal nanoparticles, the hollow structures had greater surface area, leading to enhanced transport of reactants. Transmission electron microscopy images revealed the formation of distinct hollow structures with an average size of 30 nm. As a peroxidase mimic, the HRNs showed excellent catalytic activity for the oxidation of 3,3′,5,5′-tetramethylbenzidine due to the increased surface area of the hollow structure. Moreover, the catalytic efficiency of the HRNs was greater than that of horseradish peroxidase, due to the presence of hollow structures. The HRNs were applied to the colorimetric detection of C-reactive protein (CRP) by enzyme-linked immunosorbent assay (ELISA). The results displayed great sensitivity for CRP levels of 0.12–7.8 ng/mL and a limit of detection of 33.2 pg/mL. In the recovery test, the assay showed accurate detection of CRP in spiked human serum with recovery values of 97.0–98.0%. The results of the present study reveal the validity and possibility of HRNs as alternatives to natural enzymes for application to conventional ELISA.