Diagnosis of Mycobacterium tuberculosis using palladium-platinum bimetallic nanoparticles combined with paper-based analytical devices.

In this study, we demonstrate that palladium-platinum bimetallic nanoparticles (Pd@Pt NPs) as the nanozyme, combined with a multi-layer paper-based analytical device and DNA hybridization, can successfully detect Mycobacterium tuberculosis. This nanozyme has peroxidase-like properties, which can increase the oxidation rate of the substrate. Compared with horseradish peroxidase, which is widely used in traditional detection, the Michaelis constants of Pd@Pt NPs are fourteen and seventeen times lower than those for 3,3',5,5'-tetramethylbenzidine and H2O2, respectively. To verify the catalytic efficiency of Pd@Pt NPs, this study will execute molecular diagnosis of Mycobacterium tuberculosis. We chose the IS6110 fragment as the target DNA and divided the complementary sequences into the capture DNA and reporter DNA. They were modified on paper and Pd@Pt NPs, respectively, to detect Mycobacterium tuberculosis on a paper-based analytical device. With the above-mentioned method, we can detect target DNA within 15 minutes with a linear range between 0.75 and 10 nM, and a detection limit of 0.216 nM. These results demonstrate that the proposed platform (a DNA-nanozyme integrated paper-based analytical device, dnPAD) can provide sensitive and on-site infection prognosis in areas with insufficient medical resources.

Palladium-platinum bimetallic nanomaterials and their application in Staphylococcus aureus detection on paper-based devices.

In this study, we demonstrate how palladium@platinum nanoparticles (Pd@Pt NPs) can be used as a nanozyme for the detection of Staphylococcus aureus (S. aureus) on a paper-based analytical device. Pt was doped with Pd to form bimetallic NPs that serve as a peroxidase mimetic, which can enhance the reaction area with a substrate (3, 3', 5, 5'-tetramethylbenzidine, TMB). After material characterization, we show the peroxidase-like activity of the Pd@Pt NPs featured a 13-times higher binding affinity value (Km) for TMB compared to horseradish peroxidase, which is currently widely used in immunoassays. By incorporating the Pd@Pt NPs in a paper-based immunoassay, we can detect protein A, the biomarker of S. aureus, within 30 min with a detection limit of 9.56 ng/mL. We have also successfully validated this nanozyme-immobilized paper-based analytical device (nPAD) for the detection of human immunoglobulin G to demonstrate the capability of the Pd@Pt NPs for different target analytes. This highly sensitive, rapid, and portable nPAD design has the potential for personalized medicine and point-of-care testing, which could expand on-site prognoses in resource-limited settings.