Ochratoxin A (OTA), a toxic mycotoxin, poses severe risks to environment and human health. Herein, we develop a ratiometric surface-enhanced Raman scattering (SERS) aptasensor based on internal standard (IS) methods for the sensitive and reproducible quantitative detection of OTA. Au−Ag Janus nanoparticles (NPs) are successfully synthesized under the guidance of 2-mercaptobenzoimidazole-5-carboxylic acid (MBIA), which possesses intrinsic Raman signals, thus no additional modification with a Raman reporter on NPs is required. In addition, Au−Ag Janus NPs exhibit amplified and stable SERS activity. MXenes nanosheets generate a unique and stable Raman signal, making them an ideal IS for quantitative Raman analysis. In principle, Au−Ag Janus NPs are assembled with MXenes nanosheets depending on hydrogen bond and the chelation interaction between MXenes nanosheets and OTA aptamers. In the presence of OTA, Au−Ag Janus NPs are dissociated from MXenes nanosheets due to the formation of aptamer/OTA complex, leading to the attenuation of Raman signal of Au−Ag Janus NPs, and meanwhile, the signal of MXenes nanosheets remain constant. Quantitatively, upon correction by the IS Raman signals, sensitive and quantitative detection can be achieved with the limit of detection (LOD) of 1.28 pM for OTA. Our results suggest that this ratiometric SERS aptasensor is a powerful tool which shows great promise for applications in complex systems.

PETase displays great potential in PET depolymerization. Directed evolution has been limited to engineer PETase due to the lack of high-throughput screening assay. In this study, a novel fluorescence-based high-throughput screening assay employing a newly designed substrate, bis (2-hydroxyethyl) 2-hydroxyterephthalate (termed BHET-OH), was developed for PET hydrolases. The best variant DepoPETase produced 1407-fold more products towards amorphous PET film at 50 °C and showed a 23.3 °C higher T m value than the PETase WT. DepoPETase enabled complete depolymerization of seven untreated PET wastes and 19.1 g PET waste (0.4 % W enzyme /W PET ) in liter-scale reactor, suggesting that it is a potential candidate for industrial PET depolymerization processes. The molecular dynamic simulations revealed that the distal substitutions stabilized the loops around the active sites and transmitted the stabilization effect to the active sites through enhancing inter-loop interactions network.

Establishing a simple and accurate assay for detecting Microcystin-LR (MC-LR) is of significant important for the environment and human health. Herein, we develop a ratiometric surface-enhanced Raman scattering (SERS) aptasensor based on internal standard (IS) methods for the sensitive and reproducible quantitative detection of MC-LR. Gap-tethered SERS-active Au@AgAu nanoparticles (NPs) are successfully prepared and the gap sizes are adjustable by simply adjusting the acidity. Gap-tethered Au@AgAu NPs exhibit gaptunable amplified SERS activity and are served as SERS tags. The graphene oxide (GO)/Fe 3 O 4 NPs demonstrate a unique and stable Raman band from the graphitic component, making them an ideal IS for quantitative Raman analysis. In principle, Au@gap@AgAu NPs are assembled with GO/Fe 3 O 4 NPs depending on the π−π stacking interaction between GO and MC-LR aptamers. In the presence of MC-LR, Au@gap@AgAu NPs are dissociated from GO/Fe 3 O 4 NPs due to the affinity of aptamer, leading to the changes of Raman intensity of SERS tags. Quantitatively, upon correction by the IS Raman signals, the limit of detection (LOD) is as low as 9.82 pM for MC-LR. The developed protocol provides a simple and rapid approach for the sensitive and quantitative detection of MC-LR and shows great promise for applications in complex systems.

Persistent luminescence materials (PLMs) have been capturing more and more attention in biosensing, which is ascribed to the autoluminescence-free background, no requirement of illumination in situ, and high signal-to-noise ratio. PLMs with tunable persistent luminescence and desired decay patterns are still required to meet the demands of multiple bioassays and time-resolved fluoroimmunoassays. Herein, persistent luminescence nanorods with distinct decay patterns are prepared by doping Mn2+, Mo6+, Cr3+, and Sr2+ in the Zn2GeO4 (ZGO) host material, and persistent luminescence nanoparticles are synthesized by doping Cr3+ in the ZnGa2O4 (ZGC) host material. Green-emitted ZGO:Mn NRs and NIR-emitted ZnGa2O4:Cr (ZGC) NPs show slow luminescence decay rates and noninterfered colors and are alternative probes for the dual detection of prostate specific antigens and carcinoembryonic antigens (CEAs). The limits of detection are as low as 8.9 fg mL–1 PSA and 72 fg mL–1 CEA. The nanoprobes are capable of monitoring the CEA level in the human serum matrix. This work provides a new window for the fabrication of multiplex colored PLMs with desired decay patterns, which were used in high throughput cancer early screening, cancer diagnostics, and time-resolved fluoroimmunoassay.