Uniform palladium nanosheets for fluorimetric detection of circulating tumor DNA

Fluorescence quenching property of two-dimensional (2D) nanosheets (NSs) have received extensively attention in the construction of novel biosensing platform. However, the heterogeneity of the wide-size distribution and inefficient fluorescence quenching capacity limit its wide practical applications. Herein, for the first time, we report a novel fluorescent biosensor based on uniform palladium NSs (Pd NSs) with excellent fluorescence quenching efficiency and differential affinity toward ssDNA versus dsDNA and combination with a pair of DNA detection probes with fluorophore for detecting circulating tumor DNA (ctDNA). The DNA detection probes are facilitated to adsorbed to the surface of Pd NSs, leading to efficient fluorescence quench. In the presence of target DNA, it can be linked by T4 DNA ligase to form long DNA duplex structures, which display weak affinity toward Pd NSs, producing the fluorescence recovery. The remarkable fluorescence quenching efficiency and ssDNA/dsDNA differential affinity of Pd NSs make it have a good detection ability without signal amplification. The result indicates that this facile but cost-effective strategy holds great promise in bioanalysis.

Hot-Electron-Activated Peroxidase-Mimicking Activity of Ultrathin Pd Nanozymes

Light-activated nanozymes can provide a wealth of new opportunities for the chemical industry and biotechnology. However, present remote-controlled catalytic systems are still far from satisfactory. Herein, we present an interesting example of applying ultrathin Pd nanosheets (Pd NSs) as a light-controllable peroxidase mimic. Since most of Pd atoms are exposed on their surface, Pd NSs with a thickness of 1.1 nm possess high peroxidase-like activity. More importantly, under light excitation, such intrinsic activity can be further activated by a nearly 2.4- to 3.2-fold. Such a phenomenon can be ascribed to the unique optical property of ultrathin Pd NSs, which can efficiently capture photons to generate hot electrons via surface plasmon resonance effect and thus promote the in situ decomposition of H₂O₂ into reactive oxygen species radicals (O*). This enhanced catalysis can also be used for real-time and highly sensitive colorimetric detection of H2O2. We expect our work can provide valuable insights into the rational design of artificial nanozymes with controllable and efficient activity in biomedical diagnostics, drug delivery, and environmental chemistry.