Two-dimensional ß-MnOOH nanosheets with high oxidase-mimetic activity for smartphone-based colorimetric sensing.

Manganese (Mn) is a versatile transition element with diverse oxidation states and significant biological importance. Mn-based nanozymes have emerged as promising catalysts in various applications. However, the direct use of manganese oxides as oxidase mimics remains limited and requires further improvement. In this study, we focus on hydroxylated manganese (MnOOH), specifically the layered form ß-MnOOH which exhibits unique electronic and structural characteristics. The two-dimensional ß-MnOOH nanosheets were synthesized through a hydrothermal approach and showed remarkable oxidase-like activity. These nanosheets effectively converted the oxidase substrate, 3,3',5,5'-tetramethylbenzidine (TMB), into its oxidized form by initiating the conversion of dissolved oxygen into ·O2-, 1O2 and ·OH. However, in the presence of L-cysteine (L-Cys), the catalytic activity of ß-MnOOH was significantly inhibited, enabling highly sensitive detection of L-Cys. This sensing strategy was successfully applied for smartphone-based L-Cys assay, offering potential utility in the diagnosis of Cys-related diseases. The exploration of layered ß-MnOOH nanosheets as highly active oxidase mimics opens up new possibilities for catalytic and biomedical applications.

Subcellular Nanobionic Liposome with High Zeta Potential Enhances Intravesical Adhesion and Drug Delivery.

The administration of drugs resident to counteract fluid washout has received considerable attention. However, the fabrication of a biocompatible system with adequate adhesion and tissue penetration capability remains challenging. This study presents a cell membrane-inspired carrier at the subcellular scale that facilitates interfacial adhesion and tissue penetration to improve drug delivery efficiency. Both chitosan oligosaccharide (COS) and oleic acid (OA) modified membranes exhibit a high affinity for interacting with the negatively charged glycosaminoglycan layer, demonstrating that the zeta potential of the carrier is the key to determining spontaneous penetration and accumulation within the bladder tissue. In vivo modeling has shown that a high surface charge significantly improves the retention of the drug carrier in the presence of urine washout. Possibly due to charge distribution, electric field gradients, and lipid membrane softening, the high positive surface charge enabled the carriers to penetrate the urinary bladder barrier and/or enter the cell interior. Overall, this study represents a practical and effective delivery strategy for tissue binders.

Protein-directed synthesis of fluorescent sulfur quantum dots for highly robust detection of pyrophosphate.

Inorganic pyrophosphate anions (PPi) play a key role in various biological processes and act as an essential indicator for physiological function evaluation and disease diagnosis. However, there is still a lack of available approaches for straightforward, robust, and convenient PPi detection. Herein, we design an on-off-on fluorescent switching nanoprobe employing Fe3+-mediated fluorescent sulfur quantum dots (SQDs) for highly robust detection of PPi. The bovine serum protein (BSA)-capped SQDs with fine water dispersibility and good optical stability are synthesized by an H2O2-assisted chemical etching reaction. Specifically, Fe3+ can strongly induce the aggregation of the SQDs into relatively larger sizes, resulting in aggregation-induced fluorescence quenching behavior. PPi can selectively bind with Fe3+ via emulative coordination and in preventing the aggregation of SQDs this is accompanied by recovery of fluorescence. The physicochemical properties of aggregated and disaggregated SQDs have been systematically investigated. Aggregation and disaggregation of the SQDs and the corresponding quenching and recovery of fluorescence occurs and guarantees the high-contrast sensing performance of the SQD system in complex and challenging aquatic environments. Our designed on-off-on nanoswitch holds great potential for the design of elemental quantum dot-based biosensors for the highly robust detection of analytes in the near future.

Designing CoS1.035 Nanoparticles Anchored on N-Doped Carbon Dodecahedron as Dual-Enzyme Mimics for the Colorimetric Detection of H2O2 and Glutathione.

In recent years, the exploration of the nanozyme, an artificial enzyme with the structure and function of natural enzymes, has become a hot topic in this field. Although significant progress has been made, it is still a huge challenge to design nanozymes with multiple enzyme-like catalytic activities. In this work, we have successfully fabricated a colorimetric sensing platform to mimic peroxidase-like and oxidase-like activities by the CoS1.035 nanoparticles decorated N-doped carbon framework porous dodecahedrons (abbreviated to CoS1.035/N-C PDHs). And the catalytic mechanism of CoS1.035/N-C PDHs toward the peroxidase-like and oxidase-like activities is systematically explored. The results display that CoS1.035/N-C PDHs can catalyze the oxidation of the colorless substrate 3,3,'5,5'-tetramethylbenzidine (TMB) into blue oxidized TMB (ox-TMB) by disintegrating H2O2 or the physically/chemically absorbed O2 into different ROS species (·OH or O2 ·-) in the presence or absence of H2O2. Therefore, on the basis of the dual-enzyme mimic activities of CoS1.035/N-C PDHs, the bifunctional colorimetric sensing platform is established for H2O2 detection with a wide linear range of 0.5-120 µM and glutathione detection with a linear range of 1-60 µM, respectively. This work provides an efficient platform for dual-enzyme mimics, expanding the application prospect of Co-based chalcogenides as enzyme mimics in biosensing, medical diagnosis, and environment monitoring.

Functionalized Mn3 O4 Nanosheets with Photothermal, Photodynamic, and Oxidase-Like Activities Triggered by Low-Powered Near-Infrared Light for Synergetic Combating Multidrug-Resistant Bacterial Infections.

Multidrug-resistant (MDR) pathogenic bacterial infections have become a major danger to public health. Synergetic therapy through multiple approaches is more powerful than the respective one alone, but has been rarely achieved in defeating MDR bacterial infections so far. Herein, indocyanine green-functionalized Mn3 O4 nanosheets are engineered as an efficient and safe antibacterial agent with photothermal, photodynamic, and oxidase-like activities, which display powerful ability in treating MDR bacterial infections. Therein, photothermal and photodynamic activities can be triggered by a single low-powered near-infrared laser (808 nm, 0.33 W cm-2 ), resulting in the generation of localized hyperthermia (photothermal conversion efficiency, 67.5%) and singlet oxygen. Meanwhile, oxidase-like activity of this material further leads to the generation of hydroxyl radical as well as superoxide radical. Sheet-like structure with rough surfaces make them tends to adhere on bacterial surface and thus damage membrane system as well as influence bacterial metabolism. As a result, Gram-positive and Gram-negative bacteria can both be eradicated. Animal experiments further indicate that the functionalized Mn3 O4 nanosheets can effectively treat methicillin-resistant Staphylococcus aureus-infected wounds through the triple synergetic therapy. Moreover, toxicity evaluation in vitro and in vivo has proved the superior biosafety of this material, which is promising to apply in clinical anti-infective therapy.

Fe(III)-mediated reversible catalytic activity of MoS2 nanozymes for bisphosphonate drug sensing.

Peroxidase-like activity of MoS2 quantum dots (QDs) can be reversibly regulated by means of Fe3+/alendronate sodium (ALDS)-induced aggregation/disaggregation of the QDs in solution. Specifically, Fe3+ can selectively aggregate the MoS2 QDs and thus greatly enhance their peroxidase-like activity, while such enhancement can be inhibited in the presence of ALDS owing to the competitive coordination of ALDS with Fe3+. By regulating the enzyme-like activity of MoS2 QDs, different colorimetric signal of a typical substrate of horseradish peroxidase, 3,3΄,5,5΄-tetramethylbenzidine, can be measured in the presence of H2O2. Based on this mechanism, we develop a colorimetric approach for the determination of ALDS and further applied in quality control of pharmaceutical products, utilizing either smartphone or UV-vis spectrometer as a readout. This detection method is rapid and selective, where derivatization of ALDS before detection is not needed. Such a smartphone-based colorimetric detection platform is promising to be applied in point-of-care testing at home, small clinics, or underdeveloped regions.

Etching-controlled suppression of fluorescence resonance energy transfer between nitrogen-doped carbon dots and Ag nanoprisms for glucose assay and diabetes diagnosis.

Numerous methods have been developed for glucose detection, only few cases can be really applied in clinical diagnosis. Herein, we report a new approach to achieve the detection of glucose in clinical samples and distinguishing the diabetic patients with healthy ones. Specifically, a fluorescence resonance energy transfer (FRET) system is established first, where nitrogen-doped carbon dots (N-CDs) and Ag nanoprisms (AgNPRs) with good spectral overlap act as energy donor and acceptor, respectively. Then, the FRET can be inhibited through oxidative etching of the energy acceptor in the presence of glucose and glucose oxidase, where hydrogen peroxide is generated to transform AgNPRs into Ag+ ions. Based on the turn-on fluorescent signal versus glucose concentration, a new method for quantitative detection of glucose is developed. This etching-induced analytical method is simple, reliable, robust and cost-effective, which is promising to assist the doctors to clinically diagnose diabetes and other diseases related to metabolic disorders.

Manipulating Bimetallic Nanostructures With Tunable Localized Surface Plasmon Resonance and Their Applications for Sensing.

Metal nanocrystals with well-controlled shape and unique localized surface plasmon resonance (LSPR) properties have attracted tremendous attention in both fundamental studies and applications. Compared with monometallic counterparts, bimetallic nanocrystals endow scientists with more opportunities to precisely tailor their LSPR and thus achieve excellent performances for various purposes. The aim of this mini review is to present the recent process in manipulating bimetallic nanostructures with tunable LSPR and their applications for sensing. We first highlight several significant strategies in controlling the elemental ratio and spatial arrangement of bimetallic nanocrystals, followed by discussing on the relationship between their composition/morphology and LSPR properties. We then focus on the plasmonic sensors based on the LSPR peak shift, which can be well-controlled by seed-mediated growth and selective etching. This review provides insights of understanding the "rules" involving in the formation of bimetallic nanocrystals with different structures and desired LSPR properties, and also forecasts the development directions of plasmonic sensors in the future.