Citric Acid-Functionalized Rhodium–Platinum Nanoparticles as Peroxidase Mimics for Determination of Cholesterol

Abstract

Nanostructured artificial enzymes, also called nanozymes, are considered effective substitutes for natural enzymes. In this study, citric acid-functionalized rhodium–platinum nanoparticles (CA-RhPt NPs) were synthesized by a simple one-pot synthetic method. Transmission electron microscopy images showed the uniform structure of the CA-RhPt NPs, with an average diameter of 3.5 ± 0.5 nm, and X-ray photoelectron spectroscopy and zeta potential measurements demonstrated the presence of citric acid in the CA-RhPt NPs. The CA-RhPt NPs exhibited enhanced peroxidase-like activity that catalyzed the reaction between 3,3′,5,5′-tetramethylbenzidine (TMB) and hydrogen peroxide (H2O2) due to the synergistic effects of Rh and Pt. The catalytic mechanism of CA-RhPt NPs was found to decompose H2O2 to a hydroxyl radical (•OH), and then, the •OH oxidizes the TMB, generating a blue product. The excellent peroxidase-like CA-RhPt NPs were then applied to the colorimetric determination of cholesterol. The CA-RhPt NP-based colorimetry showed sensitive cholesterol detection in the range from 0.08 to 5.0 mM, with a detection limit of 25.7 μM. The recoveries of cholesterol concentrations from the spiked human serum samples were 96.8% and 106%, which were comparable to those from the commercialized cholesterol detection kit. These results demonstrate the possibility of CA-RhPt NPs as alternatives for natural enzymes and applicability for sensitive cholesterol detection.

N, S-co-doped carbon/Co1-xS nanocomposite with dual-enzyme activities for a smartphone-based colorimetric assay of total cholesterol in human serum

“…It can be seen from Fig. 10b that the 652-nm ODs decreased slightly (<7.0%) after 5 cycles, which could be explained by the slight dissolution of metal ions in the reaction system [63]. These data and phenomena provide compelling evidence that the NSC/Co 1-x S nanocomposite can be reutilized at least five times with a minor loss in its catalytic activity.…”

Nanocomposite with Imprint of Cholesterol for Its Nonenzymatic, Visual, and Smartphone-Based Detection

“…8−10 Second, our approach is capable of detecting cholesterol concentrations in the range of 0.5−5 μM with a LOD of 0.37 μM, which is quite low compared to most of the reported methods. 12,13,15 Third, the inclusion of a molecular imprinting technique brings much-needed selectivity in the detection of cholesterol which is absent in the reported nonenzymatic works. 7,13 Fourth, we have developed a capillary sensor equipped with a smartphone app for detection of cholesterol in human serum.…”

“…Various methods have been developed for determination of cholesterol that include an HPLC-based method, a fluorescence displacement assay, an electrochemical technique, and colorimetric detection. − In addition, different nanoparticles such as graphene oxide, gold nanoparticles, polypyrroles, and polydopamine nanoparticles are utilized for cholesterol detection. ,,, Overall, these detection methods suffer three major drawbacks which limit clinical applications. First, a majority of the developed methods lack selectivity toward cholesterol. , Second, most of the methods require costly enzyme cholesterol oxidase for the detection selectivity. − Third, very often, expensive equipment and complex analysis are used. , …”

Generated Mercury(I) as a Peroxidase-like Activity Modulator via Stimulating the Expression of Active Sites of Silver Nanoparticles for Environmental Hg2+ Detection

“…Nanozymes, as an ideal substitute for natural enzymes, can significantly reduce the Gibbs free energy of the chemical reaction to catalyze the oxidation reaction . Due to their low price, convenient processing, and high stability, a series of nanomaterials with enzyme-like activities have been widely reported, − including metal organic framework-based, − carbon-based, , metal-based, − metal oxide-based nanomaterials, − and so on. However, the catalytic activities of nanozymes are still not comparable to natural enzymes, especially metal-based nanozymes.…”