Interfacial Regulation of ZIF-67 on Bacteria to Generate Bifunctional Sensing Material on Chip for Qualifying Cell-Released Reactive Oxygen Species

Energy difference-driven ROS reduction for electrochemical tracking crop growth sensitized with electron-migration nanostructures

Aiming for sustainable crop productivity under changing climate conditions, it is essential to develop handy models for in-situ monitoring of reactive oxygen species (ROS). Herein, this work reports a simple electrochemical sensing toward hydrogen peroxide (H2O2) for tracking crop growth status sensitized with electron-migration nanostructure. To be specific, Cu-based metal-organic frameworks (MOFs) with high HOMO energy level are designed for H2O2 reduction on account of Cu(I)/Cu(II) redox switchability. Importantly, the sensing performance is improved by electrochemically reduced graphene oxide (GO) with ready to use feature. To overcome the shortcomings of traditional liquid electrolytes, conductive hydrogel as semi-solid electrolyte exhibits the adhesive property to the cut plant petiole surface. Benefitting from the preferred composite models and conductive hydrogel, the electrochemical sensing toward H2O2 with high sensitivity and good anti-interference against the coexistent molecules, well qualified for acquiring plant growth status.

Integrated Sandwich-Paper 3D Cell Sensing Device to In Situ Wirelessly Monitor H2O2 Released from Living Cells

Point-of-care testing (POCT) has attracted great interest because of its prominent advantages of rapidness, precision, portability, and real-time monitoring, thus becoming a powerful biomedical device in early clinical diagnosis and convenient medical treatments. However, its complicated manufacturing process and high expense severely impede mass production and broad applications. Herein, an innovative but inexpensive integrated sandwich-paper three-dimensional (3D) cell sensing device is fabricated to in situ wirelessly detect H2O2 released from living cells. The paper-based electrochemical sensing device was constructed by a sealed sandwiched bottom plastic film/fiber paper/top hole-centered plastic film that was printed with patterned electrodes. A new (Fe, Mn)3(PO4)2/N-doped carbon nanorod was developed and immobilized on the sensing carbon electrode while cell culture solution filled the exposed fiber paper, allowing living cells to grow on the fiber paper surrounding the electrode. Due to the significantly shortening diffusion distance to access the sensing sites by such a unique device and a rationally tuned ratio of Fe2+/Mn2+, the device exhibits a fast response time (0.2 s), a low detection limit (0.4 μM), and a wide detection range (2-3200 μM). This work offers great promise for a low-cost and highly sensitive POCT device for practical clinic diagnosis and broad POCT biomedical applications.

Quantification of Neuronal Cell-Released Hydrogen Peroxide Using 3D Mesoporous Copper-Enriched Prussian Blue Microcubes Nanozymes: A Colorimetric Approach in Real Time and Anticancer Effect

Despite the effectiveness and selectivity of natural enzymes, their instability has paved the way for developing nanozymes with high peroxidase activity using a straightforward technique, thereby expanding their potential for multifunctional applications. Herein, meso-copper-Prussian blue microcubes (Meso-Cu-PBMCs) nanozymes were successfully prepared via a cost-effective hydrothermal route. It was found that the Cu-PBMCs nanozymes, with three-dimensional (3D) mesoporous cubic morphologies, exhibited an excellent peroxidase-like property. Based on the high affinity of Meso-Cu-PBMCs toward H2O2 (Km = 0.226 μM) and TMB (Km = 0.407 mM), a colorimetric sensor for in situ H2O2 detection was constructed. On account of the high catalytic activity, affinity, and cascade strategy, the Meso-Cu-PBMCs nanozyme generated rapid multicolor displays at varying H2O2 concentrations. Under optimized conditions, the proposed sensor exhibits a preferable sensitivity of 18.14 μA μM-1, a linear range of 10 nM-25 mM, and a detection limit of 6.36 nM (S/N = 10). The reliability of the sensor was verified by detecting H2O2 in spiked human blood serum and milk samples, as well as by detecting in situ H2O2 generated from the neuron cell SH-SY5Y. Besides, the Meso-Cu-PBMCs nanozyme facilitated the catalysis of H2O2 in cancer cells, generating •OH radicals that induce the death of cancer cells (HCT-116 colon cancer cells), which holds substantial potential for application in chemodynamic therapy (CDT). This proposed strategy holds promise for simple, rapid, inexpensive, and effective intracellular biosensing and offers a novel approach to improve CDT efficacy.

hROS-Responsive Behavior for Long-Term Stability of Cellulosic Gold Nanoclusters

Understanding the gold core-ligand interaction in gold nanoclusters (GNCs) is essential for the on-demand tailoring of their photoluminescence properties and long-term stability. Here, inspired by the suckers arranged directionally on the tentacles of octopus, a series of GNCs with regulating ligand structures are grown and stabilized on the cellulose nanocrystals (CNCs). The carboxylated CNCs providing an electron-rich environment to promote the luminescence of GNCs and stabilize it within a long-term of 1 year through anchoring and diluting effects, and the highest quantum yields reaches 31.02% in ultrapure water. Interestingly, this bionic preparation strategy is generally applicable to various ligands for tailoring on-demand hROS-responsive and nonresponsive GNCs to construct tunable-emission wavelength dual GNCs ratiometric probes. The results show that designing a specific ligand structure to inhibit the transformation of Au-Au to Au (I)-ligand in GNCs is crucial to regulate the hROS-responsive characteristics. As expected, the interfacial compatible dual GNCs ratiometric probe with a hROS limit of detection of 0.74 µmol L-1 can diagnose certain diseases through intracellular hROS imaging. This work provides important insights for understanding the gold core-ligand interaction in GNCs during the oxidation process triggered by intracellular hROS.

Signal Amplification Strategy Design in Nanozyme-Based Biosensors for Highly Sensitive Detection of Trace Biomarkers

Nanozymes show great promise in enhancing disease biomarker sensing by leveraging their physicochemical properties and enzymatic activities. These qualities facilitate signal amplification and matrix effects reduction, thus boosting biomarker sensing performance. In this review, recent studies from the last five years, concentrating on disease biomarker detection improvement through nanozyme-based biosensing are examined. This enhancement primarily involves the modulations of the size, morphology, doping, modification, electromagnetic mechanisms, electron conduction efficiency, and surface plasmon resonance effects of nanozymes for increased sensitivity. In addition, a comprehensive description of the synthesis and tuning strategies employed for nanozymes has been provided. This includes a detailed elucidation of their catalytic mechanisms in alignment with the fundamental principles of enhanced sensing technology, accompanied by the presentation of quantitatively analyzed results. Moreover, the diverse applications of nanozymes in strip sensing, colorimetric sensing, electrochemical sensing, and surface-enhanced Raman scattering have been outlined. Additionally, the limitations, challenges, and corresponding recommendations concerning the application of nanozymes in biosensing have been summarized. Furthermore, insights have been offered into the future development and outlook of nanozymes for biosensing. This review aims to serve not only as a reference for enhancing the sensitivity of nanozyme-based biosensors but also as a catalyst for exploring nanozyme properties and their broader applications in biosensing.