MXene-TiO2-based photocatalytic fuel cell with bioresponsive controlled glucose release system: An innovative mode for Ochratoxin A detection.

Self-powered photocatalytic fuel cell (PFC)-based sensors incorporating bioelement recognition with fuel concentration-dependent output power have been developed for electrochemical analysis, but most involve poor energy conversion efficiency and are unsuitable for routine use. Herein, a self-powered and self-checking PFC bioanalysis platform under visible light for ultrasensitive screening of Ochratoxin A (OTA) was designed. Specifically, the self-powered photocatalytic fuel cell-based sensor was comprised of a photoanode fabricated with MXenes (Ti3C2)-TiO2 and a cathode modified with Prussian blue (PB). To realize the high-performance of OTA detection, mesoporous silica nanoparticles (MSNs) were used as nanocontainers to load glucose, and aptamers were assembled on the surface of MSNs as dual-gated molecules to form signal probes. The reaction of analyte OTA with OTA aptamer was greater than the force between OTA aptamer and MSN, resulting in the release of glucose from MSNs. The released glucose was photo-oxidized by Ti3C2-TiO2 under visible light illumination and used as an electron acceptor to reduce PB, resulting in a high cell output response with a maximum output power (Pmax) of 23.516 µW cm-2. Meanwhile, the electrochromic PB enabled colorimetric detection of OTA with self-checking. The self-powered Ti3C2-TiO2-based PFC with target-recognition cargo release system exhibited superior analytical performance toward OTA in the range of 0.2 ppb-20 ppb and limit of detection (LOD) down to 0.0587 ppb. Additionally, excellent stability, rapid response, and exquisite selectivity for real samples (beer) was acceptable, providing an efficient approach in food safety monitoring.

Ti3C2 MXene-anchored photoelectrochemical detection of exosomes by in situ fabrication of CdS nanoparticles with enzyme-assisted hybridization chain reaction.

Exosomes that carry large amounts of tumor-specific molecular information have been identified as a potential non-invasive biomarker for early warning of cancer. In this work, we reported an enzyme-assisted photoelectrochemical (PEC) biosensor for quantification of exosomes based on the in situ synthesis of Ti3C2 MXene/CdS composites with magnetic separation technology and hybridization chain reaction (HCR). First, exosomes were specifically bound between aptamer-labeled magnetic beads (CD63-MBs) and a cholesterol-labeled DNA anchor. The properly designed anchor ends acted as a trigger to enrich the alkaline phosphatase (ALP) through HCR. It catalyzed more sodium thiophosphate to generate the sulfideion (S2-), which combined with Cd2+ for in situ fabrication of CdS on Ti3C2 MXene resulting in elevated photocurrent. The Ti3C2 MXene-anchored PEC method was realized for the quantitative detection of exosomes, which exhibited the dynamic working range from 7.3 × 105 particles per mL to 3.285 × 108 particles per mL with a limit of detection of 7.875 × 104 particles per mL. The strategy showed acceptable stability, high sensitivity, rapid response and excellent selectivity. Furthermore, we believe that the PEC biosensor has huge potential as a routine bioassay method for the precise quantification of exosomes from breast cancer in the future.