Voltammetric aptasensor for sulfadimethoxine using a nanohybrid composed of multifunctional fullerene, reduced graphene oxide and Pt@Au nanoparticles, and based on direct electron transfer to the active site of glucose oxidase

Ruthenium complex based nanocomposite film with enhanced and selective electrochemical sensing of bifenthrin pesticide

Bifenthrin (BF), a widely used pyrethroid pesticide in farming, lacks highly sensitive and selective sensors despite its extensive application. Ruthenium complexes are very effective for selective sensing applications but suffer from structural instability at elevated conditions, electrochemical activity, and the use of costly electrolytes. This work improves their electrochemical activity and mechanical strength by incorporating silver nanowires and replacing the costly electrolyte with abundant KCl + PBS, resulting in enhanced signal performance. Herein, a ruthenium complex containing composite film was immobilized on a platinum (Pt) electrode using Langmuir Blodgett technique. The fabricated sensor has been characterized by differential pulse voltammetry (DPV) based electrochemical technique. The BF pesticide sensing parameters, including the limit of detection (LOD), linear range (LR), and sensitivity, were evaluated using SWV, DPV, and CV techniques. Among these, the DPV technique demonstrated the best performance, achieving a sensitivity of 0.648 μA cm-2 μM-1, a LR of 1-10 μM, and a LOD of 1 μM. The relative standard deviation (RSD) values using DPV are found to be 6.3% (repeatability study), 3% (reproducibility study), 8% (metal ion interference), 5% (organic species interference), and 2% (real sample study), which are much lesser than the World Health Organization (WHO) recommendation of RSD value on the pesticide (i.e. 20%). The BF sensor demonstrated a selectivity of 2× difference of peak height response compared to similar pesticides. The reported pesticide sensor will open new options for sensor research using metal complex-based LB film nanocomposite.

Identification of hypermucoviscous Klebsiella pneumoniae strains via untargeted surface-enhanced Raman spectroscopy

Klebsiella pneumoniae is one of the most common causes of hospital-acquired infections, especially due to the emergence of the hypervirulent K. pneumoniae (hvKp) strains. Multiple methods have been developed to discriminate hvKp strains from classical K. pneumoniae (cKp) strains, such as the presence of candidate genes (e.g., peg-344, iroB, and iucA), high level of siderophore production, hypermucoviscosity phenotype, etc. Although the string test is commonly used to confirm the hypermucoviscosity of K. pneumoniae strains, it is a method lacking rigidity and accuracy. Surface-enhanced Raman spectroscopy (SERS) coupled with machine learning algorithms has been widely used in discriminating bacterial pathogens with different phenotypes. However, the technique has not be applied to identify hypermucoviscous K. pneumoniae (hmvKp) strains. In this study, we isolated a set of K. pneumoniae strains from clinical samples, among which hmvKp strains (N = 10) and cKP strains (N = 10) were randomly selected to collect SESR spectra. Eight machine learning algorithms were recruited for model construction and spectral prediction in this study, among which support vector machine (SVM) outperforms all other algorithms with the highest prediction accuracy of hmvKp strains (5-fold cross validation = 99.07%). Taken together, this pilot study confirms that SERS, combined with machine learning algorithms, can accurately identify hmvKp strains, which can facilitate the fast recognition of hvKP strains when combined with relevant methods and biomarkers in clinical settings in the near future.

Graphitic carbon nitride-based electrochemical sensors: A comprehensive review of their synthesis, characterization, and applications

Graphitic carbon nitride (g-C3N4) has garnered much attention as a promising 2D material in the realm of electrochemical sensors. It contains a polymeric matrix that can serve as an economical and non-toxic electrode material for the detection of a diverse range of analytes. However, its performance is impeded by a relatively limited active surface area and inherent instability. Although electrochemistry involving metal-doped g-C3N4 nanomaterials is rapidly progressing, it remains relatively unexplored. The metal doping of g-C3N4 augments the electrochemically active surface area of the resulting electrode, which has the potential to significantly enhance electrode kinetics and bolster catalytic activity. Consequentially, the main objective of this review is to provide insight into the intricacies of synthesizing and characterizing metal-doped g-C3N4. Furthermore, we comprehensively delve into the fundamental attributes of electrochemical sensors based on metal-doped g-C3N4, with a specific focus on healthcare and environmental applications. These applications encompass a meticulous exploration of detecting biomolecules, drug molecules, and organic pollutants.

Comprehensive review on fluorescent carbon dots and their applications in nucleic acid detection, nucleolus targeted imaging and gene delivery

Carbon dots (CDs), including carbon quantum dots, graphene quantum dots, carbon nanodots, and polymer dots, have gained significant attention due to their unique structural and fluorescence characteristics. This review provides a comprehensive overview of the classification, structural characteristics, and fluorescence properties of CDs, followed by an exploration of various fluorescence sensing mechanisms and their applications in gene detection, nucleolus imaging, and gene delivery. Furthermore, the functionalization of CDs with diverse surface ligand molecules, including dye molecules, nucleic acid probes, and metal derivatives, for sensitive nucleic acid detection is systematically examined. Fluorescence imaging of the cell nucleolus plays a vital role in examining intracellular processes and the dynamics of subcellular structures. By analyzing the mechanism of fluorescence and structure-function relationships inherent in CDs, the nucleolus targeting abilities of CDs in various cell lines have been discussed. Additionally, challenges such as the insufficient organelle specificity of CDs and the inconsistent mechanisms underlying nucleolus targeting have also been highlighted. The unique physical and chemical properties of CDs, particularly their strong affinity toward deoxyribonucleic acid (DNA), have spurred interest in gene delivery applications. The use of nuclear-targeting peptides, polymers, and ligands in conjunction with CDs for improved gene delivery applications have been systematically reviewed. Through a comprehensive analysis, the review aims to contribute to a deeper understanding of the potential and challenges associated with CDs in biomedical applications.

Recent progress on DNAzyme-based biosensors for pathogen detection

Pathogens endanger food safety, agricultural productivity, and human health. Those pathogens are spread through direct/indirect contact, airborne transmission and food/waterborne transmission, and some cause severe health consequences. As the population grows and global connections intensify, the transmission of infectious diseases expands. Traditional detection methods for pathogens still have some shortcomings, such as time-consuming procedures and high operational costs. To fulfil the demands for simple and effective detection, numerous biosensors have been developed. DNAzyme, a unique DNA structure with catalytic activity, is gradually being applied in the field of pathogen detection owing to its ease of preparation and use. In this review, we concentrated on the two main types of DNAzyme, hemin/G-quadruplex DNAzyme (HGD) and RNA-cleaving DNAzyme (RCD), explaining their research progress in pathogen detection. Furthermore, we introduced two additional novel DNAzymes, CLICK 17 DNAzyme and Supernova DNAzyme, which showed promising potential in pathogen detection. Finally, we summarize the strengths and weaknesses of these four DNAzymes and offer feasible recommendations for the development of biosensors.

Label-free liquid crystal-based optical detection of norfloxacin using an aptamer recognition probe in soil and lake water

Norfloxacin (NOX), a broad spectrum fluoroquinolone (FQ) antibiotic, is commonly detected in environmental residues, potentially contributing to biological drug resistance. In this paper, an aptamer recognition probe has been used to develop a label-free liquid crystal-based biosensor for simple and robust optical detection of NOX in aqueous solutions. Stimuli-receptive liquid crystals (LCs) have been employed to report aptamer-target binding events at the LC-aqueous interface. The homeotropic alignment of LCs at the aqueous-LC interface is due to the self-assembly of the cationic surfactant cetyltrimethylammonium bromide (CTAB). In the presence of the negatively charged NOX aptamer, the ordering changes to planar/tilted. On addition of NOX, the aptamer-NOX binding causes redistribution of CTAB at the LC-aqueous interface and the homeotropic orientation is restored. This results in a bright-to-dark optical transition under a polarized optical microscope (POM). This optical transition serves as a visual indicator to mark the presence of NOX. The devised aptasensor demonstrates high specificity with a minimum detection limit of 5 nM (1.596 ppb). Moreover, the application of the developed aptasensor for the detection of NOX in freshwater and soil samples underscores its practical utility in environmental monitoring. This proposed LC-based method offers several advantages over conventional detection techniques for a rapid, feasible and convenient way to detect norfloxacin.

A General Strategy for Food Traceability and Authentication Based on Assembly-Tunable Fluorescence Sensor Arrays

Food traceability and authentication systems play an important role in ensuring food quality and safety. Current techniques mainly rely on direct measurement by instrumental analysis, which is usually designed for one or a group of specific foods, not available for various food categories. To develop a general strategy for food identification and discrimination, a novel method based on fluorescence sensor arrays is proposed, composed of supramolecular assemblies regulated by non-covalent interactions as an information conversion system. The stimuli-responsiveness and tunability of supramolecular assemblies provided an excellent platform for interacting with various molecules in different foods. In this work, five sensor arrays constructed by supramolecular assemblies composed of pyrene derivatives and perylene derivatives are designed and prepared. Assembly behavior and sensing mechanisms are investigated systematically by spectroscopy techniques. The traceability and authentication effects on several kinds of food from different origins or grades are evaluated and verified by linear discriminant analysis (LDA). It is confirmed that the cross-reactive signals from different sensor units encompassing all molecular interactions can generate a unique fingerprint pattern for each food and can be used for traceability and authentication toward universal food categories with 100% accuracy.

Bifunctional magnetic nanoparticles with ion imprinting for improving the flow through determination of ultratraces of Cd(II) using magnetic preconcentration

A novel bifunctional magnetic sorbent with mercapto and amino groups and ion imprinting (MBII) was synthesized using a one-step aqueous sol-gel process for preconcentration and determination of Cd(II) ions. MBII was employed as a microcolumn (MC) filler in a flow-through system coupled to GFAAS. The magnetic properties of the solid allowed microcolumn magnetic solid-phase extraction (MCMSPE) to be performed by simply including a single circular magnet around the MC. This assembly enabled complete attachment of the solid to the MC wall leaving a central void to facilitate higher sample flow rates without blockage or material loss. For comparison, a bifunctional magnetic solid without imprinting (MBNI) was also synthesized and evaluated. Both MBII and MBNI were characterized by FTIR, SEM, EDX, BET and magnetization measurements. The results showed the preservation of the magnetic core, its superparamagnetism and the functional groups in the solid. Batch studies revealed a maximum adsorption capacity for both materials at pH around 6 with equilibrium reached within 5 minutes. The advantages were reflected in the maximum adsorption capacity of MBII, which was found to be 2.5 times greater than that of MBNI. Both adsorbents were compared as MC fillers for dynamic preconcentration in MCMSPE systems. Under optimized conditions, MBNI showed a PCF of 125 and MBII of 250. The higher selectivity of MBII was corroborated by interfering ion studies. The analytical performance parameters for the proposed method using MBII as an adsorbent showed a detection limit of 0.05 ng L-1, a linear range of 2.0-80 ng L-1, an RSD% of 2.2 (n = 7; 20 ng L-1) and a lifetime of more than 300 preconcentration-elution cycles without loss of sensitivity or need for refilling. The method was successfully applied to the determination of trace Cd(II) in osmosis, lake and tap water with recoveries ranging from 98 to 105%. Comparison of these results with those of similar reported methods showed a considerable improvement primarily attributed to the combined effect of MBII's higher retention capacity and its magnetic properties that allowed higher sample flow rates and, thus, enhanced figures of merit.

Methyl methacrylate-modified polystyrene microspheres: an effective strategy to enhance the fluorescence of Eu-complexes

The in vitro detection applications of europium complex-doped microspheres mainly rely on strong fluorescence intensity and a well-defined morphology. In this work, using methyl methacrylate-modified polystyrene microspheres has been proven an effective strategy to enhance the fluorescence and morphology of Eu-complexes. The experimental results showed that the modification resulted in the formation of a porous structure within the polystyrene microspheres, enhancing the doping uniformity and facilitating a more significant accumulation of fluorescent molecules. Furthermore, because of their encapsulation ability, microspheres efficiently confine the fluorescent molecules within them. In addition, the nano-scale porous structure endowed the microspheres with enhanced properties without compromising solvent swelling capability, thereby significantly boosting the fluorescence performance of porous PSMMA. In lateral flow immunoassays (LFIAs), PSMMA-Eu microspheres were effectively utilized to detect fentanyl with exceptional sensitivity by capitalizing on these benefits, capable of detecting concentrations as low as 0.10 ng mL-1. This technology has significant potential for rapid point-of-care screening and clinical applications.

Hydrothermal synthesis of modified lignin-based carbon dots derived from biomass waste for fluorescence determination of valsartan

Recently, carbon dots (CDs) have been extensively investigated as potential tools for numerous applications. Modified lignin-based CDs have been synthesized and used in the field of drug detection. They were found to be highly selective and sensitive to valsartan (VAL). Using a simple hydrothermal method, phosphorus and chlorine co-doped CDs were synthesized using lignin extracted from date seeds. The fluorescence properties of the synthesized CDs are influenced by several factors, which were investigated in detail. The optimal synthesis conditions were 1.50 g of lignin, 18 mL of 2 M NaOH, 1 mM H3PO4, 3 mM HCl and the mixture was heated at 220 °C for 16 hours. The synthesized lignin-based CDs have excellent FL properties and are well soluble in water with reasonable stability. Characterization of the prepared CDs revealed that they have various functional groups with a graphene oxide-like structure. The developed CDs show a good quantum yield of 37.7%. The FL of the CDs is quenched by VAL at λ em 313 nm after λ ex at 275 nm by a combination of static and dynamic quenching mechanisms. The response of VAL was linear in the range of 4.0-100.0 μg mL-1. The detection and quantification limits of VAL were 1.23 and 3.71 μg mL-1, respectively. The nanoprobe was successfully used to analyze VAL in drug samples and provided satisfactory results.

Bonding states of gold/silver plasmonic nanostructures and sulfur-containing active biological ingredients in biomedical applications: a review

As one of the most instrumental components in the architecture of advanced nanomedicines, plasmonic nanostructures (mainly gold and silver nanomaterials) have been paid a lot of attention. This type of nanomaterial can absorb light photons with a specific wavelength and generate heat or excited electrons through surface resonance, which is a unique physical property. In innovative biomaterials, a significant number of theranostic (therapeutic and diagnostic) materials are produced through the conjugation of thiol-containing ingredients with gold and silver nanoparticles (Au and Ag NPs). Hence, it is essential to investigate Au/Ag-S interfaces precisely and determine the exact bonding states in the active nanobiomaterials. This study intends to provide useful insights into the interactions between Au/Ag NPs and thiol groups that exist in the structure of biomaterials. In this regard, the modeling of Au/Ag-S bonding in active biological ingredients is precisely reviewed. Then, the physiological stability of Au/Ag-based plasmonic nanobioconjugates in real physiological environments (pharmacokinetics) is discussed. Recent experimental validation and achievements of plasmonic theranostics and radiolabelled nanomaterials based on Au/Ag-S conjugation are also profoundly reviewed. This study will also help researchers working on biosensors in which plasmonic devices deal with the thiol-containing biomaterials (e.g., antibodies) inside blood serum and living cells.

Design of cobalt-doped graphene quantum dot-decorated vanadium pentoxide nanosheet-based Off-On fluorescent sensor system for tiopronin sensing

Despite the high medicinal value of tiopronin, there are substantial adverse effects such as yellow skin, yellow eyes, muscle aches, etc. Therefore, there is a huge necessity to identify tiopronin using advanced sensors in provided samples. Recently, the preference for graphene quantum dots (GQDs) and inorganic nanomaterial-based fluorescent sensors for the detection of pharmaceuticals has been extensively documented due to their plentiful advantages. Therefore, in this work, the cobalt-doped GQDs decorated vanadium pentoxide nanosheet-based fluorescence switch 'Off-On' sensor (Co-GQDs@V2O5-NS) was designed for highly sensitive and selective detection of tiopronin. Briefly, the green synthesis of highly fluorescent Co-GQDs was carried out using a hydrothermal method. Meanwhile, the synthesis of V2O5-NS was synthesized using the liquid exfoliation method. The synthesis of Co-GQDs@V2O5-NS was accomplished wherein Co-GQDs adsorbed on the surface of V2O5-NS that offered the quenching of fluorescence of Co-GQDs. Afterward, the addition of tiopronin into the quenched probe disclosed the proportional recovery of fluorescence of Co-GQDs. Here, the addition of tiopronin provides the decomposition of V2O5-NS and conversion into the V4+ that aids in releasing the quenched fluorescence of Co-GQDs. The limit of detection and linearity range for tiopronin was found to be 1.43 ng/mL and 10-700 ng/mL, respectively. Moreover, it demonstrated high selectivity, good stability at experimental conditions, and practicality in analyzing tiopronin in spiked sample analysis. Hence, the designed Co-GQDs@V2O5-NS nanosized sensor enables high sensitivity, selectivity, simplicity, label-free, and eco-friendly tiopronin recognition. In the future, the utility of Co-GQDs@V2O5-NS can open a new door for sensing tiopronin in provided samples.

A novel N-CNDs/PAni modified molecular imprinted polymer for ultraselective and sensitive detection of ciprofloxacin in lentic ecosystems: a dual responsive optical sensor

The research study describes the development of a hybrid nanocomposite called nitro-doped carbon nanodots/polyaniline/molecularly imprinted polymer (N-CNDs/PAni/MIP). This composite is specifically engineered to function as a durable and flexible dual-response sensor to detect and analyze pharmaceutical organic contaminants (POCs). Powder X-Ray diffraction (PXRD), Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) were employed to perform an exhaustive structural and morphological analysis of N-CNDs/PAni/MIP. N-CNDs/PAni/MIP emitted blue luminescence under ultraviolet irradiation and exhibited typical excitation-dependent emission properties. It can act as fluorescent probe for the detection of CIPRO with high selectivity and sensitivity with an IF value of 4.2. Furthermore, N-CNDs/PAni/MIP exhibited high peroxidase-like catalytic behavior. After adding CIPRO to the N-CNDs/PAni/MIP/TMB/H2O2 system, the blue color of the solution faded due to the reduction of blue ox-TMB to colorless TMB. Based on these two phenomena, with CIPRO as the target analyte, the N-CNDs/PAni/MIP dual sensor showed a minimal detection limit of 70 pM for the fluorescent signaling platform and 3.5 nM for the colorimetric probe with a linear range of 0.038-200 nM. The fluorometric and colorimetric assays based on N-CNDs/PAni/MIP for CIPRO detection were then successfully applied to lentic water as well as to tap water samples, demonstrating the sensitivity and dependability of the instrument. Furthermore, the synthesized PVA (N-CNDs/PAni/MIP) films enable the recognition of CIPRO, and these films have the potential to be integrated into portable sensing devices, providing a practical solution for rapid and on-site detection of CIPRO in various samples.

Recent Progress in Folic Acid Detection Based on Fluorescent Carbon Dots as Sensors: A Review

Folic acid (FA) is a water-soluble vitamin found in diverse natural sources and is crucial for preserving human health. The risk of health issues due to FA deficiency underscores the need for a straightforward and sensitive FA detection methodology. Carbon dots (CDs) have gained significant attention owing to their exceptional fluorescence performance, biocompatibility, and easy accessibility. Consequently, numerous research studies have concentrated on developing advanced CD fluorescent probes to enable swift and precise FA detection. Despite these efforts, there is still a requirement for a thorough overview of the efficient synthesis of CDs and their practical applications in FA detection to further promote the widespread use of CDs. This review paper focuses on the practical applications of CD sensors for FA detection. It begins with an in-depth introduction to FA and CDs. Following that, based on various synthetic approaches, the prepared CDs are classified into diverse detection methods, such as single sensing, visual detection, and electrochemical methods. Furthermore, persistent challenges and potential avenues are highlighted for future research to provide valuable insights into crafting effective CDs and detecting FA.

A genetic engineering strategy to enhance outer membrane vesicle-mediated extracellular electron transfer of Geobacter sulfurreducens

Bioelectrochemical systems (BESs) are unique devices that harness the metabolic activity of electroactive microorganisms (EAMs) to convert chemical energy stored in organic substrates into electrical energy. Enhancing electron transfer efficiency between EAMs and electrodes is the key to practical implementation of BESs. Considering the role of outer membrane vesicles (OMVs) in mediating electron transfer of EAMs, a genetic engineering strategy to achieve OMVs overproduction was explored to enhance electron transfer efficiency and the underlying mechanisms were investigated. This study constructed a mutant strain of Geobacter sulfurreducens that lacked the ompA gene encoding an outer membrane protein. Experimental results showed that the mutant strain produced more OMVs and possessed higher electron transfer efficiency in Fe(III) reduction, dye degradation and current generation in BESs than the wild-type strain. More cargoes such as c-type cytochromes, functional proteins, eDNA, polysaccharides and signaling molecules that might be favorable for electron transfer and biofilm formation were found in OMVs produced by ompA-deficient anodic biofilm, which possibly contributed to the improved electron transfer efficiency of ompA-deficient biofilm. The results indicate that overproduction of OMVs in EAMs might be a potential strategy to enhance BESs performance.

Fluorescent multichannel sensor array based on three carbon dots derived from Tibetan medicine waste for the quantification and discrimination of multiple heavy metal ions in water

A fluorescent multichannel sensor array has been established based on three carbon dots derived from Tibetan medicine waste for rapid quantification and discrimination of six heavy metal ions. Due to the chelation between metal ions and carbon dots (CDs), this fluorescence "turn off" mode sensing array can quantify six metal ions as low as "μM" level. Moreover, the six heavy metal ions display varying quenching effects on these three CDs owing to diverse chelating abilities between each other, producing differential fluorescent signals for three sensing channels, which can be plotted as specific fingerprints and converted into intuitive identification profiles via principal component analysis (PCA) and hierarchical cluster analysis (HCA) technologies to accurately distinguish Cu2+, Fe3+, Mn2+, Ag+, Ce4+, and Ni2+ with the minimum differentiated concentration of 5 μM. Valuably, this sensing array unveils good sensitivity, exceptional selectivity, ideal stability, and excellent anti-interference ability for both mixed standards and actual samples. Our contribution provides a novel approach for simultaneous determination of multiple heavy metal ions in environmental samples, and it will inspire the development of other advanced optical sensing array for simultaneous quantification and discrimination of multiple targets.

Silver-coated hollow fiber surface plasmon resonance sensor for glucose detection with enhanced limit of detection

A fiber-optic surface plasmon resonance (SPR) biosensor based on a silver-coated hollow fiber (HF) structure for glucose detection is presented. The sensor surface was immobilized with 4-mercaptophenylboronic acid (PMBA) acting as a glucose recognition monolayer. Then, gold nanoparticles (AuNPs) modified with 2-aminoethanethiol (2-AET) and PMBA were introduced onto the sensor surface after glucose was captured to enhance the wavelength shift of the SPR phenomenon excited by the light transmitted in the wall of the HF sensor. Instead of the conventional one-step sensitization pretreatment commonly used in the deposition process of silver films for fiber-optic SPR sensors, a sensitization-activation two-step activation method was adopted in the fabrication of the proposed sensor. Experiments for glucose detection were performed on the fabricated sensors in the concentration range of 1 nM-1 mM. Results showed that the sensor fabricated by the two-step activation method has a much larger shift of resonance wavelength than the sensor fabricated using the one-step sensitization method. The resonance wavelength shift was found to be linear to the logarithm of the concentration in the range of 1 nM-1 mM. The sensor achieved a limit of detection (LOD) of as low as 1 nM, which is at least an order of magnitude lower than that of other fiber-optic sensors for glucose detection reported previously. The presented HF glucose sensor has the potential for biosensing applications and provides a large reference value in the study of optical fiber SPR sensors for biosensing.

Futuristic Alzheimer's therapy: acoustic-stimulated piezoelectric nanospheres for amyloid reduction

The degeneration of neurons due to the accumulation of misfolded amyloid aggregates in the central nervous system (CNS) is a fundamental neuropathology of Alzheimer's disease (AD). It is believed that dislodging/clearing these amyloid aggregates from the neuronal tissues could lead to a potential cure for AD. In the present work, we explored biocompatible polydopamine-coated piezoelectric polyvinylidene fluoride (DPVDF) nanospheres as acoustic stimulus-triggered anti-fibrillating and anti-amyloid agents. The nanospheres were tested against two model amyloidogenic peptides, including the reductionist model-based amyloidogenic dipeptide, diphenylalanine, and the amyloid polypeptide, amyloid beta (Aβ42). Our results revealed that DPVDF nanospheres could effectively disassemble the model peptide-derived amyloid fibrils under suitable acoustic stimulation. In vitro studies also showed that the stimulus activated DPVDF nanospheres could efficiently alleviate the neurotoxicity of FF fibrils as exemplified in neuroblastoma, SHSY5Y, cells. Studies carried out in animal models further validated that the nanospheres could dislodge amyloid aggregates in vivo and also help the animals regain their cognitive behavior. Thus, these acoustic stimuli-activated nanospheres could serve as a novel class of disease-modifying nanomaterials for non-invasive electro-chemotherapy of Alzheimer's disease.

One-pot Synthesis of High-performance Green-emitting Carbon Dots for Cd2+ Sensing and Anti-counterfeiting Applications

This study presents a facile one-pot solvothermal synthesis of high-performance green fluorescent carbon dots (G-CDs) using o-phenylenediamine and ethylenediamine as precursors. The G-CDs show excellent optical, temporal, and chemical stability. Notably, they exhibit the highest quantum yield of 24.2% in ethanol and a strong green emission peaking at 546 nm under 440-490 nm excitation. In addition, G-CDs have outstanding salt resistance and multi-solvent compatibility. Due to its bright photoluminescence, G-CDs can be used as a secure ink for anti-counterfeiting. More remarkably, Cd2+ ions can efficiently quench the fluorescence of G-CDs with a detection limit of 0.152 µmol/L, enabling accurate quantification of Cd2+ in water systems. The simple synthesis of high-performance G-CDs expands their applicability in sensing and bioimaging.

A novel and sensitive electrochemical aptasensor for sulfadimethoxine detection based on the triple helix/exonuclease I-assisted double-amplification strategy

In this paper, a novel and sensitive electrochemical aptasensor for sulfadimethoxine (SDM) detection has been designed based on the triple helix structure/exonuclease I (Exo I)-assisted double signal amplification strategy. The aptamer probe (Apt) hybridizes with the signal transduction probe (STP) on the electrode to form a rigid double-stranded DNA (dsDNA) structure, so that the STP remains upright and methylene blue (MB) on the STP is far away from the electrode surface, resulting in a delicate current signal. In the presence of SDM, the SDM and Apt combine into a complex, leading to the transfer of the Apt and the exposure of the STP. Meanwhile, the added Exo I can digest the Apt to realize the cyclic amplification of SDM. After the addition of the signal probe (SP), a triple helix structure between the SP and STP is formed under acidic conditions, and MB on the STP and SP collide with the electrode surface to generate a strong electrochemical signal. The proposed aptasensor combines the features of the triple helix structure and Exo I to achieve double signal amplification for the sensitive detection of SDM with a wide linear range of 0.05-1000 ng mL-1 and a low detection limit of 0.02 ng mL-1. Furthermore, it has been successfully used to detect SDM in milk and lake water samples.

A selective colorimetric and efficient removal strategy for mercury(II) in aquatic systems using mesoporous Fe3O4-loaded silver probes

Mesoporous Fe3O4-loaded silver nanocomposites (Fe3O4@Ag) were simply fabricated as bi-functional nanozymes for the catalysis-based detection and removal of Hg2+ ions. It was found that the as-prepared magnetic Fe3O4@Ag could display peroxidase-like catalysis activity that could be rationally enhanced in the presence of Hg2+ ions. To our surprise, the shell of the Ag element may decrease the catalysis of the Fe3O4 to some degree. However, the Ag particles could serve as the probes for specifically recognizing Hg2+ ions and trigger increased catalysis through the formation of Ag-Hg alloys, with a decreased signal background. A high-throughput colorimetric analytical method was thereby developed based on the Fe3O4@Ag catalysis for probing Hg2+ ions in the muscles of fish by using 96-well plates, at linear Hg2+ concentrations ranging from 0.010 to 2.5 mg kg-1. Moreover, the developed colorimetric analytical method was applied to evaluate Hg2+ levels in muscle samples of different kinds of fish. Unexpectedly, an obvious difference of Hg2+ levels in muscles of four kinds of fish was discovered, with the order of snakehead (Ophicephalus argus) > largemouth bass (Micropterus salmoides) > crucian carp (Carassius auratus) > silver carp (Hypophthalmichthys molitrix), where the carnivorous fish showed higher Hg2+ levels than the omnivorous or plant-based ones. Moreover, the as-fabricated Fe3O4@Ag adsorbents with their large specific surface area and high environmental robustness could exhibit efficient Hg2+ adsorption with capacities of up to 397.60 mg g-1. A removal efficiency of 99.40% can also be expected for Hg2+ ions from wastewater, with the magnet-aided recycling of Fe3O4@Ag adsorbents. Such an Fe3O4@Ag-based colorimetric analysis and removal strategy for Hg2+ ions should find wide applications in the fields of aquatic food safety, environmental monitoring, and clinical diagnostics of Hg-poisoning diseases.

Surface-enhanced Raman spectroscopy for the characterization of bacterial pellets of Staphylococcus aureus infected by bacteriophage

Drug-resistant pathogenic bacteria are a major cause of infectious diseases in the world and they have become a major threat through the reduced efficacy of developed antibiotics. This issue can be addressed by using bacteriophages, which can kill lethal bacteria and prevent them from causing infections. Surface-enhanced Raman spectroscopy (SERS) is a promising technique for studying the degradation of infectious bacteria by the interaction of bacteriophages to break the vicious cycle of drug-resistant bacteria and help to develop chemotherapy-independent remedial strategies. The phage (viruses)-sensitive Staphylococcus aureus (S. aureus) bacteria are exposed to bacteriophages (Siphoviridae family) in the time frame from 0 min (control) to 50 minutes with intervals of 5 minutes and characterized by SERS using silver nanoparticles as SERS substrate. This allows us to explore the effects of the bacteriophages against lethal bacteria (S. aureus) at different time intervals. The differentiating SERS bands are observed at 575 (C-C skeletal mode), 620 (phenylalanine), 649 (tyrosine, guanine (ring breathing)), 657 (guanine (COO deformation)), 728-735 (adenine, glycosidic ring mode), 796 (tyrosine (C-N stretching)), 957 (C-N stretching (amide lipopolysaccharides)), 1096 (PO2 (nucleic acid)), 1113 (phenylalanine), 1249 (CH2 of amide III, N-H bending and C-O stretching (amide III)), 1273 (CH2, N-H, C-N, amide III), 1331 (C-N stretching mode of adenine), 1373 (in nucleic acids (ring breathing modes of the DNA/RNA bases)) and 1454 cm-1 (CH2 deformation of saturated lipids), indicating the degradation of bacteria and replication of bacteriophages. Multivariate data analysis was performed by employing principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) to study the biochemical differences in the S. aureus bacteria infected by the bacteriophage. The SERS spectral data sets were successfully differentiated by PLS-DA with 94.47% sensitivity, 98.61% specificity, 94.44% precision, 98.88% accuracy and 81.06% area under the curve (AUC), which shows that at 50 min interval S. aureus bacteria is degraded by the replicating bacteriophages.

Self-calibrating surface-enhanced Raman scattering-lateral flow immunoassay for determination of amyloid-β biomarker of Alzheimer's disease

Rapid early diagnosis of Alzheimer's disease (AD) is critical for its effective and prompt treatment since the clinically available treatments can only relieve the symptoms or slow the disease progression. However, it is still a grand challenge to accurately diagnose AD at its early stage because of the indiscernible early symptoms and the lack of sensitive detection tools. Here, we develop a self-calibrating surface-enhanced Raman scattering (SERS)-lateral flow immunoassay (LFIA) biosensor for quantitative analysis of amyloid-β1-42 (Aβ1-42) biomarker in biofluids, enabling accurate AD diagnosis. The designed SERS-LFIA biosensor makes full use of the unique aspects of the LFIA format and the SERS technique to quantify the Aβ1-42 level in complex biofluids with high sensitivity, excellent anti-interference capability, low-cost, and operation simplicity. The key aspect of the design of this biosensor is that internal standard (IS)-SERS nanoparticles are embedded in the test line of the test strip as a self-calibration unit for correction of fluctuations of SERS signals caused by various external factors such as test parameters and sample heterogeneity. We demonstrate significant improvement of the detection performance of the SERS-LFIA biosensor for ratiometric quantification of Aβ1-42 owing to the built-in IS in the test line. We expect that the present IS-based biosensing strategy provides a promising tool for accurate AD diagnosis and longitudinal monitoring of therapeutic response with great promises for clinical translation.

Fluorescent sensing platform based on polyethyleneimine-protected copper nanoclusters for detection of chromium(VI) in real samples

A new type of polyethyleneimine-protected copper nanoclusters (PEI-CuNCs) is favorably developed by a one-pot method under mild conditions. The obtained PEI-CuNCs is characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, Fourier-transform infrared (FTIR) spectroscopy and other techniques. It is worth noting that the proposed PEI-CuNCs demonstrate a selective response to chromium(VI) over other competitive species. Fluorescence quenching of PEI-CuNCs is determined to be chromium(VI) concentrations dependence with a low limit of detection of 8.9 nM. What is more, the as-developed PEI-CuNCs is further employed in building a detection platform for portable recognition of chromium(VI) in real samples with good accuracy. These findings may offer a distinctive strategy for the development of methods for analyzing and monitoring chromium(VI) and expand their application in real sample monitoring.

Co-based Nanozymatic Profiling: Advances Spanning Chemistry, Biomedical, and Environmental Sciences

Nanozymes, next-generation enzyme-mimicking nanomaterials, have entered an era of rational design; among them, Co-based nanozymes have emerged as captivating players over times. Co-based nanozymes have been developed and have garnered significant attention over the past five years. Their extraordinary properties, including regulatable enzymatic activity, stability, and multifunctionality stemming from magnetic properties, photothermal conversion effects, cavitation effects, and relaxation efficiency, have made Co-based nanozymes a rising star. This review presents the first comprehensive profiling of the Co-based nanozymes in the chemistry, biology, and environmental sciences. The review begins by scrutinizing the various synthetic methods employed for Co-based nanozyme fabrication, such as template and sol-gel methods, highlighting their distinctive merits from a chemical standpoint. Furthermore, a detailed exploration of their wide-ranging applications in biosensing and biomedical therapeutics, as well as their contributions to environmental monitoring and remediation is provided. Notably, drawing inspiration from state-of-the-art techniques such as omics, a comprehensive analysis of Co-based nanozymes is undertaken, employing analogous statistical methodologies to provide valuable guidance. To conclude, a comprehensive outlook on the challenges and prospects for Co-based nanozymes is presented, spanning from microscopic physicochemical mechanisms to macroscopic clinical translational applications.

Lung cancer cells detection by a photoelectrochemical MoS2 biosensing chip

This research aims to explore the potential application of this approach in the production of biosensor chips. The biosensor chip is utilized for the identification and examination of early-stage lung cancer cells. The findings of the optical microscope were corroborated by the field emission scanning electron microscopy, which provided further evidence that the growth of MoS2 is uniform and that there is minimal disruption in the electrode, hence minimizing the likelihood of an open circuit creation. Furthermore, the bilayer structure of the produced MoS2 has been validated through the utilization of Raman spectroscopy. A research investigation was undertaken to measure the photoelectric current generated by three various types of clinical samples containing lung cancer cells, specifically the CL1, NCI-H460, and NCI-H520 cell lines. The findings from the empirical analysis indicate that the coefficient of determination (R-Square) for the linear regression model was approximately 98%. Furthermore, the integration of a double-layer MoS2 film resulted in a significant improvement of 38% in the photocurrent, as observed in the device's performance.

Carbon dots@noble metal nanoparticle composites: research progress report

Carbon dots@noble metal nanoparticle composites are formed by combining carbon dots and metal nanoparticles using various strategies. Carbon dots exhibit a reducing ability and function as stabilisers; consequently, metal-ion solutions can be directly reduced by them to synthesise gold, silver, and gold-silver alloy particles. Carbon dots@gold/silver/gold-silver particle composites have demonstrated the potential for several practical applications owing to their superior properties and simple preparation process. Until now, several review articles have been published to summarise fluorescent carbon dots or noble metal nanomaterials. Compared with metal-free carbon dots, carbon dots@noble metal nanoparticles have a unique morphology and structure, resulting in new physicochemical properties, which allow for sensing, bioimaging, and bacteriostasis applications. Therefore, to promote the effective development of carbon dots@noble metal nanoparticle composites, this paper primarily reviews carbon dots@gold/silver/gold-silver alloy nanoparticle composites for the first time in terms of the following aspects. (1) The synthesis strategies of carbon dots@noble metal nanoparticle composites are outlined. The principle and function of carbon dots in the synthesis strategies are examined. The advantages and disadvantages of these methods and composites are analysed. (2) The characteristics and properties of such composites are described. (3) The applications of these composite materials are summarised. Finally, the potentials and limitations of carbon dots@noble metal nanoparticle composites are discussed, thus laying the foundation for their further development.

Simple potentiometry and cyclic voltammetry techniques for sensing Hg2+ ions in water using a promising flower-shaped WS2-WO3/poly-2-aminobenzene-1-thiol nanocomposite thin film electrode

A highly promising flower-shaped WS2-WO3/poly-2-aminobenzene-1-thiol (P2ABT) nanocomposite was successfully synthesized via a reaction involving 2-aminobenzene-1-thiol, Na2WO4, and K2S2O8 as oxidants. The WS2-WO3/P2ABT nanocomposite demonstrated remarkable potential as a sensor for detecting harmful Hg2+ ions in aqueous solutions. The sensing behavior was evaluated over a wide concentration range, from 10-6 to 10-1 M, using a simple potentiometric study on a two-electrode cell. The calibration curve yielded an excellent Nernstian slope of 33.0 mV decade-1. To further validate the sensing capabilities, cyclic voltammetry was employed, and the results showed an increasing trend in the cyclic voltammetry curve as the Hg2+ concentration increased from 10-6 to 10-1 M with an evaluated sensitivity of 2.4 μA M-1. The WS2-WO3/P2ABT nanocomposite sensor exhibited exceptional selectivity for detecting Hg2+ ions, as no significant effects were observed from other interfering ions such as Zn2+, Ni2+, Ca2+, Mg2+, Al3+, and K+ ions in the cyclic voltammetry tests. Furthermore, the sensor was tested on a natural sample that was free of Hg2+ ions, and the cyclic voltammetry curves did not produce any characteristic peaks, confirming the sensor's specificity for Hg2+ detection. The sensor's cost-effectiveness and ease of fabrication present the potential for developing a simple and practical sensor for detecting highly poisonous ions in aqueous solutions.

Electrochemical aptasensor based on DNA-templated copper nanoparticles and RecJf exonuclease-assisted target recycling for lipopolysaccharide detection

An electrochemical aptasensor for detecting lipopolysaccharides (LPS) was fabricated based on DNA-templated copper nanoparticles (DNA-CuNPs) and RecJf exonuclease-assisted target recycling. The DNA-CuNPs were synthesized on a double-stranded DNA template generated through the hybridization of the LPS aptamer and its complementary chain (cDNA). In the absence of LPS, the CuNPs were synthesized on DNA double-strands, and a strong readout corresponding to the CuNPs was achieved at 0.10 V (vs. SCE). In the presence of LPS, the fabricated aptamer could detach from the DNA double-strand to form a complex with LPS, disrupting the template for the synthesis of CuNPs on the electrode. Meanwhile, RecJf exonuclease could hydrolyze the cDNA together with this single-stranded aptamer, releasing the LPS for the next round of aptamer binding, thereby enabling target recycling amplification. As a result, the electrochemical signal decreased and could be used to indicate the LPS content. The fabricated electrochemical aptasensor exhibited an extensive dynamic working range of 0.01 pg mL-1 to 100 ng mL-1, and its detection limit was 6.8 fg mL-1. The aptasensor also exhibited high selectivity and excellent reproducibility. Moreover, the proposed aptasensor could be used in practical applications for the detection of LPS in human serum samples.

A recyclable Eu3+-functionalized dual-emissive metal-organic framework for portable, rapid detection and efficient removal of malachite green

A europium-functionalized, dual-emissive, metal-organic framework-based fluorescence sensor (EuUCNDA) was constructed via post-synthetic modification of an UiO-66-type precursor through coordination interactions. EuUCNDA exhibited extremely high selectivity and sensitivity for malachite green (MG) with a low detection limit of 13.01 nM, a wide linear concentration range (0.05-50 μM), excellent anti-interference properties, a rapid response (<1 min), and the possibility of recycling. The good sensing performance of EuUCNDA enables the practical detection of MG in fish pond water and grass carp with good recoveries. Moreover, EuUCNDA can be reused for sensing MG and over 90% of fluorescence intensity can be restored after 7 cycles. Furthermore, EuUCNDA-embedded paper-based sensors combined with smartphone imaging afford portable and visual monitoring of MG in real samples. Notably, besides good sensing performance, EuUCNDA could efficiently remove MG from water. Hence, this work provides a recyclable and sensitive fluorescence sensor for portable, visual, rapid detection and efficient removal of MG.

Cheap and portable paper chip with terrific oxidase-like activity and SERS enhancement performance for SERS-colorimetric bimodal detection of intracellular glutathione

Glutathione (GSH) acts a crucial role in the normal operation of manifold life activities and is closely bound up with many human diseases. Here, a SERS-colorimetric bimodal paper-based biosensor based on Mn-doped CDs/silver nanoparticles (Mn-CDs/AgNPs) has been fabricated for high-efficiency quantification of intracellular GSH. The Mn-CDs/AgNPs with fine oxidase-like characteristic and SERS enhancement ability has been assembled onto the Whatman filter paper (WFP) to cleverly fabricate paper chip (Mn-CDs/AgNPs@WFP) which can trigger the oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) into blue TMBox and simultaneously enhance the SERS signal of TMBox. However, the introduction of GSH inhibits the oxidation of TMB, leading to color fading of paper chip and diminishment of SERS signal. Considering this, the bimodal paper-based sensing platform can be exploited for SERS-colorimetric detection of GSH, manifesting excellent selectivity, reliable stability, and satisfactory precision. The detection limits of SERS and colorimetric detection modes are as low as 0.41 μM and 0.53 μM, respectively. Furthermore, this proposed bimodal biosensor has been successfully utilized for the determination of intracellular GSH and validated by commercial GSH assay kit, which provides a mighty and convenient tool for intracellular GSH detection and can boost future effort about exploitation of other multimode paper-based biosensors as well as promote their appliances in disease diagnosis.

Green Emissive Molybdenum Nanoclusters for Selective and Sensitive Detection of Hydroxyl Radical in Water Samples

In this work, Cassia tora (C. tora) have been used as a template to synthesize green fluorescent C. tora molybdenum nanoclusters (C. tora-MoNCs) through a green chemistry approach. These C. tora-MoNCs showed a quantum yield (QY) of 7.72% and exhibited a significant emission peak at 498 nm when excited at 380 nm. The as-prepared C. tora-MoNCs had an average size of 3.48 ± 0.80 nm and showed different surface functionality. The as-synthesized C. tora-MoNCs were successfully identified the hydroxyl radical (•OH) via a fluorescence quenching mechanism. Also, fluorescence lifetime and Stern-Volmer proved that after the addition of •OH radicals it was quenched the fluorescence intensity via a static quenching mechanism. The limit of detection is 9.13 nM, and this approach was successfully utilized for sensing •OH radicals in water samples with a good recovery rate.

Selective purification and rapid quantitative detection of spores using a "stepped" magnetic flow device

A study on the inactivation and germination mechanism of spores is very important in the application of spores, as such high-purity spores are the basis of related research. However, spores and vegetative cells of bacteria often coexist, and it is difficult to separate them. In this study, a magnetic flow device for the purification of spores in the culture medium system was developed based on a "stepped" structure with a magnetic force that could absorb vegetative cells with magnetic nanoparticles. The operation process was as follows: first, vancomycin functionalized nanoparticles were used to prepare Van-Fe3O4 NPs, which were then combined with vegetative cells to form a magnetic conjugate. Subsequently, the magnetic conjugate (vegetative cells) flowed through the "stepped" magnetic flow device and was adsorbed. Meanwhile, the spores moved through the channel and were collected. The achieved purity of the collected spores was more than 95%. Further, the number of the obtained spores was quickly quantified using Raman spectroscopy. The entire purification and quantitative process can be completed within 30 min and the limit of detection was 5 CFU mL-1. This study showed outstanding spore purification ability and provided a new method for purification and rapid quantitative detection of spores.

Selective FRET nano probe based on carbon dots and naphthalimide-isatin for the ratiometric detection of peroxynitrite in drug-induced liver injury

Drug-induced liver injury (DILI) is the most common cause for acute liver failure in the USA and Europe. However, most of DILI cases can recover or be prevented if treatment by the offending drug is discontinued. Recent research indicates that peroxynitrite (ONOO-) can be a potential indicator to diagnose DILI at an early stage. Therefore, the establishment of an assay to detect and track ONOO- in DILI cases is urgently needed. Here, a FRET-based ratiometric nano fluorescent probe CD-N-I was developed to detect ONOO- with high selectivity and excellent sensitivity. This probe consists of carbon dots and a naphthalimide-isatin peroxynitrite sensing system assembled based on electrostatic interactions. Using CD-N-I we were able to detect exogenous ONOO- in live cells and endogenous ONOO- in APAP-induced liver injury of HepG2 cells.

A wearable AuNP enhanced metal-organic gel (Au@MOG) sensor for sweat glucose detection with ultrahigh sensitivity

The demand for sensitive and non-invasive sensors for monitoring glucose levels in sweat has grown considerably in recent years. This study presents the development of a wearable sensor for sweat glucose detection with ultrahigh sensitivity. The sensor was fabricated by embedding Au nanoparticles (AuNPs) and metal-organic gels (MOGs) on nickel foam (NF). A non-enzymatic electrocatalytic glucose sensor has been developed to combine the three-dimensional network of MOGs with more active sites favourable for glucose diffusion and the transfer of electrons from glucose to the electrode. These results show that the sensor has an ultrahigh sensitivity of 13.94 mA mM-1 cm-2, a linear detection range between 2 and 600 μM, and a lower detection limit as low as 1 μM (signal/noise = 3) with comparable accuracy and reliability under non-alkaline conditions to those of high-pressure ion chromatography (HPIC). Furthermore, a wearable sweat glucose sensor has been constructed by sputtering an Au conductive layer on a flexible polydimethylsiloxane (PDMS) substrate and coating it with Au@MOGs. Our work demonstrates that the combination of Au NPs and MOGs can enhance the sensitivity and activity of these materials, making them useful for electrocatalytic glucose monitoring with ultrahigh sensitivity.

Biocompatibility assessment of chemically modified GONRs with hemoglobin and histopathological studies for its toxicity evaluation

Transition metal-Schiff base complexes are found to be important for biomedical applications but have demerits of being homogeneous complexes, thus their synthesis on the surface of graphene oxide nanoribbons (GONRs), materials of specific interest, can be beneficial for preparing advanced graphene-based materials for biomedical applications. Of foremost importance is their safety and biocompatibility with biological systems. In this study, a transition metal-Schiff base complex has been synthesized on the surface of a GONR (Ni-S-GNR) using 3-aminopropyltriethoxysilane and pyridine-2-carbaldehyde and complexing nickel. This Ni-S-GNR was characterized well by various physicochemical techniques. The evaluation of biocompatibility of Ni-S-GNR with hemoglobin confirmed binding interactions and influence on the native structure of hemoglobin. It was found that there was alteration in the secondary and tertiary structures of hemoglobin. In addition, histopathological studies on the liver and kidney cells of rats revealed non-toxicity of Ni-S-GNR towards these cells. Overall, Ni-S-GNR was found to be compatible with protein as the native structure was not destroyed and was non-toxic to cells.

Utilising the Nanozymatic Activity of Copper-Functionalised Mesoporous C3 N5 for Sensing Biomolecules

Designing unique nanomaterials for the selective sensing of biomolecules is of significant interest in the field of nanobiotechnology. In this work, we demonstrated the synthesis of ordered Cu nanoparticle-functionalised mesoporous C3 N5 that has unique peroxidase-like nanozymatic activity for the ultrasensitive and selective detection of glucose and glutathione. A nano hard-templating technique together with the in-situ polymerisation and self-assembly of Cu and high N-containing CN precursor was adopted to introduce mesoporosity as well as high N and Cu content in mesoporous C3 N5 . Due to the ordered structure and highly dispersed Cu in the mesoporous C3 N5 , a large enhancement of the peroxidase mimetic activity in the oxidation of a redox dye in the presence of hydrogen peroxide could be obtained. Additionally, the optimised Cu-functionalised mesoporous C3 N5 exhibited excellent sensitivity to glutathione with a low detection limit of 2.0 ppm. The strong peroxidase activity of the Cu-functionalised mesoporous C3 N5 was also effectively used for the sensing of glucose with a detection limit of 0.4 mM through glucose oxidation with glucose oxidase. This unique Cu-functionalised mesoporous C3 N5 has the potential for detecting various molecules in the environment as well as for next-generation glucose and glutathione diagnostic devices.

Ultrahighly Sensitive and Selective Glutathione Sensor Based on Carbon Dot-Functionalized Solution-Gate Graphene Transistor

A new type of carbon dot (CD)-functionalized solution-gated graphene transistor (SGGT) sensor was designed and fabricated for the highly sensitive and highly selective detection of glutathione (GSH). The CDs were synthesized via a one-step hydrothermal method using DL-thioctic acid and triethylenetetramine (TETA) as sources of S, N, and C. The CDs have abundant amino and carboxyl groups and were used to modify the surface of the gate electrode of SGGT as probes for detecting GSH. Remarkably, the CDs-SGGT sensor exhibited excellent selectivity and ultrahigh sensitivity to GSH, with an ultralow limit of detection (LOD) of up to 10-19 M. To the best of our knowledge, the sensor outperforms previously reported systems. Moreover, the CDs-SGGT sensor shows rapid detection and good stability. More importantly, the detection of GSH in artificial serum samples was successfully demonstrated.

Recent advances and prospects in nanomaterials for bacterial sepsis management

Bacterial sepsis is a life-threatening condition caused by bacteria entering the bloodstream and triggering an immune response, underscoring the importance of early recognition and prompt treatment. Nanomedicine holds promise for addressing sepsis through improved diagnostics, nanoparticle biosensors for detection and imaging, enhanced antibiotic delivery, combating resistance, and immune modulation. However, challenges remain in ensuring safety, regulatory compliance, scalability, and cost-effectiveness before clinical implementation. Further research is needed to optimize design, efficacy, safety, and regulatory strategies for effective utilization of nanomedicines in bacterial sepsis diagnosis and treatment. This review highlights the significant potential of nanomedicines, including improved drug delivery, enhanced diagnostics, and immunomodulation for bacterial sepsis. It also emphasizes the need for further research to optimize design, efficacy, safety profiles, and address regulatory challenges to facilitate clinical translation.

Nanoclusters with specific DNA overhangs: modifying configurability, engineering contrary logic pairs and the parity generator/checker for error detection

The most promising alternative for next-generation molecular computers is biocomputing, which uses DNAs as its primary building blocks to perform a Boolean operation. DNA nanoclusters (NCs) have emerged as promising candidates for biosensing applications due to their unique self-assembly properties and programmability. It has been demonstrated that adding DNA overhangs to DNA NCs improves their adaptability in identifying specific biomolecular interactions. A recent proposal in DNA computing is the concept of "contrary logic pairs (CLPs)" executed by employing a DNA hybrid architecture as a universal platform. We have designed thymine overhang-modified DNA-templated NCs (T-Au/Ag NCs). These NCs serve as a chemosensing ensemble platform, where the presence of HgII ions mediates the formation of M-Au/Ag NCs. The resulting NCs exhibit the capability to drive elementary CLPs (YES, NOT, OR, NOR, INH and IMP) as well as complex logic operations (XOR and XNOR). Additionally, they can be utilized for advanced non-arithmetic DNA logic devices like a parity generator (pG) and a parity checker (pC) for "error detection". Bit errors are an unavoidable and common occurrence during any computing. A cascade of XOR operations was used to evaluate these errors by introducing the pG and pC at the transmitting (TX) and receiving (RX) ends in binary transmission, respectively, which has devastating implications for reliable logic circuits, especially in advanced logic computation. Moreover, an even/odd natural number from 0 to 9 distinguishable pC was designed based on a dual-source responsive computing platform. This work offers inspiring avenues for a cost-effective strategy to construct highly-intelligent DNA computing devices by enhancing the multi-input responsive single DNA platform concept.

Magnetic solid-phase extraction of polycyclic aromatic hydrocarbons from water samples using magnetic carbon nanofiber/MIL-101(Cr) nanocomposites

In this study, magnetic carbon nanofibers (Fe3O4@CNF) were modified with MIL-101(Cr) (Fe3O4@CNF@MIL-101) and used as sorbents for magnetic solid-phase extraction (MSPE) to extract polycyclic aromatic hydrocarbons (PAHs) from real water samples. Gas chromatography coupled with a flame ionization detector (GC-FID) was used for the determination of the PAHs. The effect of experimental variables on the extraction efficiency of PAHs was investigated and optimized. These variables include the quantity of sorbent, the kind and volume of the elution solvent, the duration of extraction and desorption, and the salt concentration. The linear range was found to be 0.01 to 200 ng mL-1 with correlation coefficients ranging from 0.9906 to 0.9931 after the effective extraction parameters were optimized. Its detection limits (LOD) were also calculated to be between 0.003 and 0.005 ng mL-1 (S/N = 3). The method's repeatability was tested at three different concentration levels (0.1, 1, and 10 ng mL-1), and relative standard deviations (RSDs%) were obtained in the range of 2.3 to 5.0%. Finally, using the MSPE-GC-FID method, PAHs were extracted from tap water, wastewater, seawater, and spring water samples. The relative recoveries were in the range of 95.7 to 99.8%.

Enhancing electrochemical sensing through the use of functionalized graphene composites as nanozymes

Graphene-based nanozymes possess inherent nanomaterial properties that offer not only a simple substitute for enzymes but also a versatile platform capable of bonding with complex biochemical environments. The current review discusses the replacement of enzymes in developing biosensors with nanozymes. Functionalization of graphene-based materials with various nanoparticles can enhance their nanozymatic properties. Graphene oxide functionalization has been shown to yield graphene-based nanozymes that closely mimic several natural enzymes. This review provides an overview of the classification, current state-of-the-art development, synthesis routes, and types of functionalized graphene-based nanozymes for the design of electrochemical sensors. Furthermore, it includes a summary of the application of functionalized graphene-based nanozymes for constructing electrochemical sensors for pollutants, drugs, and various water and food samples. Challenges related to nanozymes as electrocatalytic materials are discussed, along with potential solutions and approaches for addressing these shortcomings.

Recent advancements in nanomaterial based optical detection of food additives: a review

Food additives have become a critical component in the food industry. They are employed as preservatives to decelerate the negative effects of environmental and microbial factors on food quality. Currently, food additives are used for a variety of purposes, including colorants, flavor enhancers, nutritional supplements, etc., owing to improvements in the food industry. Since the usage of food additives has increased dramatically, the efficient monitoring of their acceptable levels in food products is quite necessary to mitigate the problems associated with their inappropriate use. The traditional methods used for detecting food additives are generally based on standard spectroscopic and chromatographic techniques. However, these analytical techniques are limited by their high instrumentation cost and time-consuming procedures. The emerging field of nanotechnology has enabled the development of highly sensitive and specific sensors to analyze food additives in a rapid manner. The current article emphasizes the need to detect various food additives owing to their potential negative effects on humans, animals, and the environment. In this article, the role of nanomaterials in the optical sensing of food additives has been discussed owing to their high accuracy, ease-of-use, and excellent sensitivity. The applications of nanosensors for the detection of various food additives have been elaborated with examples. The current article will assist policymakers in developing new rules and regulations to mitigate the adverse effects of toxic food additives on humans and the environment. In addition, the prospects of nanosensors for the optical detection of food additives at a commercial scale have been discussed to combat their irrational use in the food industry.

A cooperation tale of biomolecules and nanomaterials in nanoscale chiral sensing and separation

The cooperative relationship between biomolecules and nanomaterials makes up a beautiful tale about nanoscale chiral sensing and separation. Biomolecules are considered a fabulous chirality 'donor' to develop chiral sensors and separation systems. Nature has endowed biomolecules with mysterious chirality. Various nanomaterials with specific physicochemical attributes can realize the transmission and amplification of this chirality. We focus on highlighting the advantages of combining biomolecules and nanomaterials in nanoscale chirality. To enhance the sensors' detection sensitivity, novel cooperation approaches between nanomaterials and biomolecules have attracted tremendous attention. Moreover, innovative biomolecule-based nanocomposites possess great importance in developing chiral separation systems with improved assay performance. This review describes the formation of a network based on nanomaterials and biomolecules mainly including DNA, proteins, peptides, amino acids, and polysaccharides. We hope this tale will record the perpetual relation between biomolecules and nanomaterials in nanoscale chirality.

New two-dimensional nanocomposites combined with target-induced strategy in an electrochemical aptasensor for sensitive determination of sulfadimethoxine

Ni-Zn bimetallic organic framework nanosheets (NiZn-MOF NSs) were modified onto PEI-functionalized MXene for the first time. The combination of the two kinds of nanosheets forms a sensing platform with superior conductivity and biocompatibility. On this basis, a highly sensitive biosensor was developed for the determination of sulfadimethoxine (SDM). Furthermore, Au and Mn nanoparticles decorated reduced graphene oxide (Au-Mn/rGO) was introduced as a signal hindering molecule under the target-induced amplification strategy. When the Au-Mn/rGO-labelled SDM-binding aptamer (Au-Mn/rGO-SBA) specifically bound to target SDM, it detached from the electrode, thereby further amplifying the electrochemical signal of [Fe(CN)6]3-/4-. The developed aptasensor for SDM showed excellent response signals in the range 1 pg mL-1 to 100 ng mL-1, with a limit of detection (LOD) as low as 0.22 pg mL-1. Significantly, the proposed sensor also showed satisfactory results in milk samples with recoveries ranging from 87.0 to 96.4% and RSD from 1.5 to 5.1%, which is believed to be useful in food safety assays.

Dual-mode transfer response based on electrochemical and fluorescence signals for the detection of amyloid-beta oligomers (AβO)

An aptamer sensor has been developed utilizing a dual-mode and stimuli-responsive strategy for quantitative detection of AβO (amyloid-beta oligomers) through simultaneous electrochemical and fluorescence detection. To achieve this, we employed UIO-66-NH2 as a carrier container to load MB (Methylene Blue), and Fe3O4 MNPs (iron oxide magnetic nanoparticles) with aptamer (ssDNA-Fe3O4 MNPs) fixed on their surface for biological gating. The ssDNA-Fe3O4 MNPs were immobilized onto the surface of UIO-66-NH2 through hydrogen bonding between the aptamer and the -NH2 group on the surface of UIO-66-NH2, thereby encapsulating MB and forming ssDNA-Fe3O4@MB@UIO-66-NH2. During the detection of AβO, the aptamer selectively reacted with AβO to form the AβO-ssDNA-Fe3O4 complex, leading to its detachment from the surface of UIO-66-NH2. This detachment facilitated the release of MB, enabling its electrochemical detection. Simultaneously, the AβO-ssDNA-Fe3O4 complex was efficiently collected and separated using a magnet after leaving the container's surface. Furthermore, the addition of NaOH facilitated the disconnection of biotin modifications at the 3' end of the aptamer from the avidin modifications on the Fe3O4 MNPs. Consequently, the aptamer detached from the surface of Fe3O4 MNPs, resulting in the restoration of fluorescence intensity of FAM (fluorescein-5'-carboxamidite) modified at its 5' end for fluorescence detection. The dual-mode sensor exhibited significantly enhanced differential pulse voltammetry signals and fluorescence intensity compared to those in the absence of AβO. The sensor demonstrated a wide detection range of 10 fM to 10 μM, with a detection limit of 3.4 fM. It displayed excellent performance in detecting actual samples and holds promising prospects for early diagnosis of Alzheimer's disease.

Silver nanoparticles in electrochemical immunosensing and the emergence of silver-gold galvanic exchange detection

Nanoparticle-based electrochemical immunosensors demonstrate high sensitivity toward biomarker detection due to the large surface area of the nanoparticles and their ability to amplify the signal of the target molecule. Additionally, they have a fast response time, relatively lower cost, and can be easily miniaturized for point-of-care applications. Among noble metals, silver nanoparticles (AgNPs) have been extensively used in electrochemical sensors due to their unique properties, such as catalytic activity and excellent electrical conductivity. This Feature Article describes six approaches for incorporating AgNPs in electrochemical platforms, featuring the most recent developments in the silver-gold galvanic exchange-based detection strategy. With a few exceptions, many of these detection methods use AgNP oxidation into Ag+ ions, followed by electrodeposition of Ag+ ions onto the working electrode as zero-valent Ag metal and a final stripping step using a voltammetric technique. Combining these steps provides desirable low detection limits and good sensitivity for various biomarkers. A few other methods involved the reduction of Ag+ ions and depositing them as Ag metal onto the electrode using a reagent mixture so that the striping analysis could be performed. Typically, this reagent mixture includes Ag+ ions, a reducing agent, or an enzyme substrate. Besides, AgNPs have also been directly used to modify the surface of electrodes to facilitate kinetically favored redox-mediated electrochemical reactions. In addition to Ag detection methods, this report will also provide recent examples to illustrate how the size and shape of AgNPs impact the detection limits and sensitivity of an electrochemical assay. Finally, we discuss recent developments in lab-on-a-chip type immunosensors designed explicitly for Ag-based metalloimmunoassay detection, and we envision that this article will provide a comprehensive summary of the operational principles and new insights into such immunoassay systems.

A bacterial cellulose-based LiSrVO4:Eu3+ nanosensor platform for smartphone sensing of levodopa and dopamine: point-of-care diagnosis of Parkinson's disease

Among the catecholamines, dopamine (DA) is essential in regulating multiple aspects of the central nervous system. The level of dopamine in the brain correlates with neurological diseases such as Parkinson's disease (PD). However, dopamine is unable to cross the blood-brain barrier (BBB). Therefore, levodopa (LD) is used to restore normal dopamine levels in the brain by crossing the BBB. Thus, the control of LD and DA levels is critical for PD diagnosis. For this purpose, LiSr0.0985VO4:0.015Eu3+ (LSV:0.015Eu3+) nanoplates were synthesized by the microwave-assisted co-precipitation method, and have been employed as an optical sensor for the sensitive and selective detection of catecholamines. The synthesized LSV:0.015Eu3+ nanoplates emitted red fluorescence with a high quantum yield (QY) of 48%. By increasing the LD and DA concentrations, the fluorescence intensity of LSV:0.015Eu3+ nanoplates gradually decreased. Under optimal conditions, the linear dynamic ranges were 1-40 μM (R2 = 0.9972) and 2-50 μM (R2 = 0.9976), and the detection limits (LOD) were 279 nM, and 390 nM for LD and DA, respectively. Herein, an instrument-free, rapid quantification visual assay was developed using a paper-based analytical device (PAD) with LSV:0.015Eu3+ fixed on the bacterial cellulose nanopaper (LEBN) to determine LD and DA concentrations with ease of operation and low cost. A smartphone was coupled with the PAD device to quantitatively analyze the fluorescence intensity changes of LSV:0.015Eu3+ using the color recognizer application (APP). In addition, the LSV:0.015Eu3+ nanosensor showed acceptable repeatability and was used to analyze real human urine, blood serum, and tap water samples with a recovery of 96-107%.

A bimetallic Fe-Mg MOF with a dual role as an electrode in asymmetric supercapacitors and an efficient electrocatalyst for hydrogen evolution reaction (HER)

In this work, a novel bimetallic Fe-Mg/MOF was synthesized through a cost-effective and rapid hydrothermal process. The structure, morphology, and composition were examined using X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy. Further, the Brunauer-Emmett-Teller (BET) measurement showed a 324 m2 g-1 surface area for Fe-Mg/MOF. The Fe-Mg/MOF achieved 1825 C g-1 capacity at 1.2 A g-1 current density, which is higher than simple Fe-MOF (1144 C g-1) and Mg-MOF (1401 C g-1). To assess the long-term stability of the asymmetric device, the bimetallic MOF supercapattery underwent 1000 charge/discharge cycles and retained 85% of its initial capacity. The energy and power densities were calculated to be 57 W h kg-1 and 2393 W kg-1, respectively. Additionally, Fe-Mg/MOF showed superior electrocatalytic performance in hydrogen evolution reaction (HER) by demonstrating a smaller Tafel slope of 51.43 mV dec-1. Our research lays the foundation for enhancing the efficiency of energy storage technologies, paving the way for more sustainable and robust energy solutions.

A dual-function fluorescent probe for the detection of pH values and formaldehyde

A dual-function fluorescent probe (Probe 1) was developed in this work for the separate detection of pH value and formaldehyde (HCHO). Probe 1 could recognize HCHO and the pH value from the amino group. The colour of the probe solution was changed from grey blue to light blue with the increase in the pH value, and luminous intensity became larger with the increase in formaldehyde concentration. The curve function relationship between fluorescence intensity and the pH value was also determined. A smartphone containing a colour detector for imaging was used to record the values of the three primary colours (R value, G value, and B value) for the probe solution in formaldehyde. Importantly, there was a linear functional relationship between the B*R/G value with HCHO concentration. Therefore, the probe could be used as a rapid tool for the detection of formaldehyde. More importantly, Probe 1 was successfully used to detect formaldehyde in an actual distilled liquor sample.