Salt-template preparation of Mo5N6 nanosheets with peroxidase- and catalase-like activities and application for colorimetric determination of 4-aminophenol

A sensitive sandwich-type electrochemical aptasensing platform based on Ti3C2Tx/MoS2/MWCNT@rGONR composites for simultaneous detection of kanamycin and chloramphenicol in food samples

A Ti3C2Tx/MoS2/MWCNT@rGONR nanocomposite was prepared for the first time for building a sensitive electrochemical aptasening platform to simultaneously detect kanamycin (Kana) and chloramphenicol (Cap). Owing to their accordion-like structure, rich surface groups, and high charge mobility, Ti3C2Tx/MoS2/MWCNT@rGONR composites provided a spacious covalent immobilization surface and a better electrochemical aptasensing platform. The aptamers of Kana and Cap used in sensors enhance the selectivity. Furthermore, TiP, an ion exchanger, was used for loading more different metal ions functioning as labels to form a sandwich-type sensor together with Ti3C2Tx/MoS2/MWCNT@rGONR, improving the electrochemical sensitivity and obtaining a highly distinguishable signal readout. Under the optimized conditions, the sensor has good detection limits of 0.135 nmol L-1 and 0.173 nmol L-1 for Kana and Cap, respectively, at the same linearity concentration of 0.5-2500 nmol L-1. Finally, it was successfully applied for detection in milk and fish meat, and the results were compared with the standard method HPLC, indicating its great potential for food safety monitoring.

Mo5N6 nanosheets for fluorescent quenching and target recognition: Highly selectively sensing of sodium hexametaphosphate

Typical fluorescent biosensors use fluorescently labeled ssDNA for target recognition and nanomaterials for signal transduction. Herein, we propose a reverse sensing strategy that Mo5N6 nanosheets are used for target recognition while fluorescein (FAM)-labeled ssDNA only serves for signal generation. We discover that Mo5N6 nanosheets show high fluorescence quenching ability (>95%) and selective recognition for sodium hexametaphosphate (SHMP). After FAM-labeled ssDNA is adsorbed on Mo5N6 nanosheets, the fluorescence is quenched due to the photoinduced electron transfer (PET) effect between FAM and Mo5N6 nanosheets. SHMP can specifically displace the adsorbed FAM-labeled ssDNA from Mo5N6 nanosheets, resulting in more than 80% fluorescence recovery on addition of 5 μmol L-1 SHMP. This biosensor can sensitively detect SHMP down to 150 nmol L-1 and selectively recognize SHMP over glucose, lactose, common amino acids, Zn2+, Mg2+, Ca2+ and other phosphates (such as Na2HPO4, sodium pyrophosphate, sodium tripolyphosphate). This biosensor also shows great potential for the detection of SHMP in bacon sample. This work not only provides a facile sensitive and selective biosensor for SHMP but also exploits the application of transition metal nitrides in the field of sensing and biosensing.

Nonenzymatic dual glucose sensing on boronic acid modified zeolitic imidazolate framework-67 nanoparticles for diabetes management

For early diabetes identification and management, the progression of an uncomplicated and exceedingly responsive glucose testing technology is crucial. In this study, we present a new sensor incorporating a composite of metal organic framework (MOF) based on cobalt, coated with boronic acid to facilitate selective glucose binding. Additionally, we successfully employed a highly sensitive electro-optical immunosensor for the detection of subtle changes in concentration of the diabetes biomarker glycated haemoglobin (HbA1c), using zeolitic imidazolate framework-67 (ZIF-67) coated with polydopamine which further modified with boronic acid. Utilizing the polymerization characteristics of dopamine and the NH2 groups, a bonding structure is formed between ZIF-67 and 4-carboxyphenylboronic acid. ZIF-67 composite served as an effective substrate for immobilising 4-carboxyphenylboronic acid binding agent, ensuring precise and highly selective glucose identification. The sensing response was evaluated through both electrochemical and optical methods, confirming its efficacy. Under optimized experimental condition, the ZIF-67 based sensor demonstrated a broad detection range of 50-500 mg dL-1, a low limit of detection (LOD) of 9.87 mg dL-1 and a high correlation coefficient of 0.98. Furthermore, the 4-carboxyphenylboronic acid-conjugated ZIF-67-based sensor platform exhibited remarkable sensitivity and selectivity in optical-based detection for glycated haemoglobin within the clinical range of 4.7-11.3%, achieving a LOD of 3.7%. These findings highlight the potential of the 4-carboxyphenylboronic acid-conjugated ZIF-67-based electro-optical sensor as a highly sensitive platform for diabetes detection.

On the Dendrite-Suppressing Effect of Laser-Processed Polylactic Acid-Derived Carbon Coated Zinc Anode in Aqueous Zinc Ion Batteries

A major bottleneck limiting the commercialization of aqueous zinc ion batteries (AZIBs) is dendrite formation on the zinc (Zn) anode during the plating/stripping process, which leads to rapid deterioration in performance and, consequently to the device failure. In this regard, researchers are trying to design more stable anodes toward suppressing dendrite formation. One possible solution to tackle this problem and to extend the cycling life of AZIBs is to modify the zinc anode surface by coating carbonaceous materials, enabling more controlled charge flux and uniform ion distribution. This work reports sustainable and bio-derived polylactic acid (PLA) as a coating layer on the zinc anode. Carbonizing this polymer under ambient conditions using a high-power nanosecond laser forms a carbon-coated zinc foil, which was directly utilized as the anode in aqueous zinc ion batteries. The fabricated laser-processed PLA-derived carbon-coated zinc anode demonstrated an extended cycling life of almost 1600 hours, significantly outperforming the bare zinc anode. A full aqueous zinc ion battery assembled from as-modified anode and as-prepared V2O5 nanofibers as cathode was able to deliver a specific capacity of 238 mAh g-1 at 1.0 A g-1 with a capacity retention of 70 % after 1000 cycles.

Dual-functional porphyrinic zirconium-based metal-organic framework for the fluorescent sensing of histidine enantiomers and Hg2

A novel fluorescence sensor based on a porphyrinic zirconium-based metal-organic framework, L-cysteine-modified PCN-222 (L-Cys/PCN-222), was developed to selectively recognize histidine enantiomers and sensitively detect Hg2+. The dual-functional sensor was successfully prepared via the solvent-assisted ligand incorporation method and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), 1H nuclear magnetic resonance (1H NMR) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, circular dichroism (CD), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption-desorption analyses. L-Cys/PCN-222 not only showed a higher quenching response for L-histidine than that for D-histidine with a fast fluorescent response rate of <40 s but also exhibited low detection limits for L- and D-histidine (2.48 μmol L-1 and 3.85 μmol L-1, respectively). Moreover, L-Cys/PCN-222 was employed as a fluorescent and visual sensor for the highly sensitive detection of Hg2+ in the linear range of 10-500 μmol L-1, and the detection limit was calculated to be 2.79 μmol L-1 in surface water. The specific and selective recognition of chiral compounds and metal ions by our probe make it suitable for real field applications.

SPOOC (Sensor for Periodic Observation of Choline): An Integrated Lab-on-a-Spoon Platform for At-Home Quantification of Choline in Infant Formula

Choline is an essential micronutrient for infants' brain development and health. To ensure that infants receive the needed daily dose of choline, the U.S. Food and Drug Administration (FDA) has set requirements for choline levels in commercialized infant formulas. Unfortunately, not all families can access well-regulated formulas, leading to potential inadequacies in choline intake. Economic constraints or difficulties in obtaining formulas, exacerbated by situations like COVID-19, prompt families to stretch formulas. Accurate measurement of choline in infant formulas becomes imperative to guarantee that infants receive the necessary nutritional support. Yet, accessible tools for this purpose are lacking. An innovative integrated sensor for the periodic observation of choline (SPOOC) designed for at-home quantification of choline in infants' formulas and milk powders is reported. This system is composed of a choline potentiometric sensor and ionic-liquid reference electrode developed on laser-induced graphene (LIG) and integrated into a spoon-like device. SPOOC includes a micro-potentiometer that conducts the measurements and transmits results wirelessly to parents' mobile devices. SPOOC demonstrated rapid and accurate assessment of choline levels directly in pre-consuming infant formulas without any sample treatment. This work empowers parents with a user-friendly tool for choline monitoring promoting informed nutritional decision-making in the care of infants.

Spindle-shaped Cu-Ru mesoporous nanospheres with enhanced enzyme-like activity for visual differentiation of toxic o-/m-aminophenol and recognition mechanisms

To effectively differentiate toxic aminophenol isomers, a kind of spindle-shaped Cu-Ru bimetal mesoporous nanozyme (Cu-Ru MPNZ) with high specific surface was developed by one-pot homogeneous reduction method, directed by hexadecyl trimethyl ammonium bromide (CTAB) in this work. By virtue of the distinctive microstructure, Cu-Ru MPNZ expressed superior bi-functional oxidase- and peroxidase-mimic activity to catalyze the oxidation of 3,3',5,5,'-tetramethylbenzidine (TMB) and 2,2'-azinobis (3-ethylbenzothiazoline-6- sulfonic acid) ammonium salt (ABTS) with low Michaelis-Menten constants and quick reaction rates. Especially, toxic aminophenol isomers could exclusively react with the oxydates of TMB or ABTS to express differentiable signals in color. Under the optimal conditions, Cu-Ru MPNZ was successfully applied for visual differentiation of toxic aminophenol isomers in real aqueous, juices and medicinal samples with low detection limits (1.60 × 10-8 mol/L for o-aminophenol and 3.25 × 10-8 mol/L for m-aminophenol) and satisfactory recoveries (96.6-103.5%). The different recognition mechanisms of Cu-Ru MPNZ to toxic o- and m-aminophenol isomers were proposed for the first time as far as we known. This work will provide a potential way to monitor different organic isomer pollution in future.

Metal-Organic Frameworks Nanocarriers for Functional Nucleic Acid Delivery in Biomedical Applications

Metal-organic frameworks (MOFs), a distinctive funtionalmaterials which is constructed by various metal ions and organic molecules, have gradually attracted researchers' attention from they were founded. In the last decade, MOFs emerge as a biomedical material with potential applications due to their unique properties. However, the MOFs performed as nanocarriers for functional nucleic acid delivery in biomedical applications rarely summarized. In this review, we introduce recent developments of MOFs for nucleic acid delivery in various biologically relevant applications, with special emphasis on cancer therapy (including siRNA, ASO, DNAzyme, miRNA and CpG oligodeoxynucleotides), bioimaging, biosensors and separation of biomolecules. We expect the accomplishment of this review could benefit certain researchers in biomedical field to develop novel sophisticated nanocarriers for functional nucleic acid delivery based on the promising material of MOFs.

β-Cyclodextrin-functionalized Ti3C2Tx MXene nanohybrids as innovative signal amplifiers for the electrochemical sandwich-like immunosensing of squamous cell carcinoma antigen

Herein, a simple and highly sensitive electrochemical sandwich-like immunosensor for the squamous cell carcinoma antigen (SCCA) was constructed using gold nanoparticle/graphene nanosheet (Au/GN) nanohybrids as a sensing platform and β-cyclodextrin/Ti₃C₂T_x MXenes (β-CD/Ti₃C₂T_x) as a signal amplifier. The good biocompatibility and large surface area as well as the high conductivity of Au/GN allow the platform to load primary antibodies (Ab₁) and facilitate electron transport. In the case of the β-CD/Ti₃C₂T_x nanohybrids, the β-CD molecule is dedicated to binding secondary antibodies (Ab₂) through host-guest interactions, thus inducing the formation of the sandwich-like structure Ab₂-β-CD/Ti₃C₂T_x/SCCA/Ab₁/Au/GN in the presence of SCCA. Interestingly, Cu²⁺ can be adsorbed and self-reduced on the surface of the sandwich-like structure to form Cu⁰ since Ti₃C₂T_x MXenes can exhibit superior adsorption and reduction capabilities towards Cu²⁺, and a prominent current signal of Cu⁰ can be observed via differential pulse voltammetry. Based on this principle, an innovative signal amplification strategy has been proposed for SCCA detection, which avoids the process of labeling the probe and the specific immobilization step of catalytic components on the surface of amplification markers. After the optimization of various conditions, a wide linear range from 0.05 pg mL^-1 to 20.0 ng mL^-1, coupled with a low detection limit of 0.01 pg mL^-1, was obtained for SCCA analysis. The proposed method for SCCA detection was also applied in real human serum samples and the observed results are satisfactory. This work opens up new pathways for constructing electrochemical sandwich-like immunosensors for SCCA and other targets.

Programmable synthesis of well-defined, glycosylated iron(ii) supramolecular assemblies with multivalent protein-binding capabilities

Multivalency plays a key role in achieving strong, yet reversible interactions in nature, and provides critical chemical organization in biological recognition processes. Chemists have taken an interest in designing multivalent synthetic assemblies to both better understand the underlying principles governing these interactions, and to build chemical tools that either enhance or prevent such recognition events from occurring in biology. Rationally tailoring synthetic strategies to achieve the high level of chemical control and tunability required to mimic these interactions, however, is challenging. Here, we introduce a systematic and modular synthetic approach to the design of well-defined molecular multivalent protein-binding constructs that allows for control over size, morphology, and valency. A series of supramolecular mono-, bi-, and tetrametallic Fe(ii) complexes featuring a precise display of peripheral saccharides was prepared through coordination-driven self-assembly from simple building blocks. The molecular assemblies are fully characterized, and we present the structural determination of one complex in the series. The mannose and maltose-appended assemblies display strong multivalent binding to model lectin, Concanavalin A (K _d values in μM), where the strength of the binding is a direct consequence of the number of saccharide units decorating the molecular periphery. This versatile synthetic strategy provides chemical control while offering an easily accessible approach to examine important design principles governing structure-function relationships germane to biological recognition and binding properties.

Influence of dopant concentration on the ammonia sensing performance of citric acid-doped polyvinyl acetate nanofibers

The chemical modification of polymer nanofiber-based ammonia sensors by introducing dopants into the active layers has been proven as one of the low-cost routes to enhance their sensing performance. Herein, we investigate the influence of different citric acid (CA) concentrations on electrospun polyvinyl acetate (PVAc) nanofibers coated on quartz crystal microbalance (QCM) transducers as gravimetric ammonia sensors. The developed CA-doped PVAc nanofiber sensors are tested against various concentrations of ammonia vapors, in which their key sensing performance parameters (i.e., sensitivity, limit of detection (LOD), limit of quantification (LOQ), and repeatability) are studied in detail. The sensitivity and LOD values of 1.34 Hz ppm^-1 and 1 ppm, respectively, can be obtained during ammonia exposure assessment. Adding CA dopants with a higher concentration not only increases the sensor sensitivity linearly, but also prolongs both response and recovery times. This finding allows us to better understand the dopant concentration effect, which subsequently can result in an appropriate strategy for manufacturing high-performance portable nanofiber-based sensing devices.

Nanobots-based advancement in targeted drug delivery and imaging: An update

Manipulation and targeted navigation of nanobots in complex biological conditions can be achieved by chemical reactions, by applying external forces, and via motile cells. Several studies have applied fuel-based and fuel-free propulsion mechanisms for nanobots movements in environmental sciences and robotics. However, their applications in biomedical sciences are still in the budding phase. Therefore, the current review introduces the fundamentals of different propulsion strategies based on the advantageous features of applied nanomaterials or cellular components. Furthermore, the recent developments reported in various literatures on next-generation nanobots, such as Xenobots with applications of in-vitro and in-vivo drug delivery and imaging were also explored in detail. The challenges and the future prospects are also highlighted with corresponding advantages and limitations of nanobots in biomedical applications. This review concludes that with ever booming research enthusiasm in this field and increasing multidisciplinary cooperation, micro-/nanorobots with intelligence and multifunctions will emerge in the near future, which would have a profound impact on the treatment of diseases.

Label-free fluorescence detection of hydrogen peroxide and glucose based on the Ni-MOF nanozyme-induced self-ligand emission

A bifunctional Ni-MOF nanosheet was synthesized and developed for label-free fluorescent detection of H₂O₂ and glucose. The Ni-MOF exhibited intrinsic peroxidase-like activity and its catalytic activity was demonstrated to be originated from the hydroxyl radicals (•OH) produced in catalytic process. Since the generated •OH enabled terephthalic acid, the non-fluorescent organic ligand of Ni-MOF, to form a strongly fluorescent 2-hydroxy terephthalic acid, the Ni-MOF nanozyme was endowed with dual-function properties of mimicking peroxidase and emitting fluorescence. Based on this bifunctional Ni-MOF nanozyme, the proposed label-free fluorescence sensing strategy was applied to detecting H₂O₂ and glucose with wide linear ranges of 0.1-20 mM and 8-30 μM, and low detection limits of 4.0 × 10^-5 M and 4.0 × 10^-6 M, respectively. Furthermore, the bifunctional Ni-MOF-based label-free sensing platform was successfully used for the glucose detection in human serum samples, showing good reproducibility and high accuracy. This strategy provides a green and sensitive method for the determination of small biomolecules in practical applications by the combination of enzyme cascade reaction.

Research progress in synthesis and biological application of quantum dots

Quantum dots are an excellent choice for biomedical applications due to their special optical properties and quantum confinement effects. This paper reviews the research and application progress of several quantum...