Highly sensitive fluorogenic sensing of L-Cysteine in live cells using gelatin-stabilized gold nanoparticles decorated graphene nanosheets

Developing an Electrochemically Reversible Switch for Modulating the Optical Signal of Gold Nanoparticles

Gold nanoparticles (AuNPs) possess remarkable optical properties and electrical conductivity, making them highly relevant in various fields such as medical diagnoses, biological imaging, and electronic sensors. However, the existing methods for modulating the optical properties of AuNPs are often under limitations such as a high cost, the complexity of detection, a narrow range of application settings, and irreversibility. In this study, we propose a novel approach to address these challenges by constructing a reversible electrochemical switch. The switch (ITO-OMAD) involves covalently linking nitroxide radicals and AuNPs (AuNPs-NO•), followed by tethering this nanocomposite to a siloxane-derived indium tin oxide (ITO) electrode. By simply electrochemically oxidizing/reducing the nitroxide units, one is able to reversibly modulate the optical properties of AuNPs at will. The surface morphology and structure of the as-prepared ITO-OMAD electrode were characterized through scanning electron microscopy (SEM) and cyclic voltammetry (CV). SEM imaging confirmed the successful anchoring of AuNPs on the ITO electrode. Electrochemical tests performed in the three-electrode system demonstrated that the local surface plasmon resonance (LSPR) of AuNPs can be reversibly regulated by alternatively imposing ± 0.5V (vs. Ag/AgCl) to the modified electrode. The development of this electrochemical switch presents a novel approach to effectively control the optical properties of AuNPs. The further exploration and utilization of this reversible electrochemical switch could significantly enhance the versatility and practicality of AuNPs in numerous applications.

Emerging carbonate anion intercalated- ZnCr-layered double hydroxide/vanadium carbide nanocomposite: Sustainable design strategies based on disposal electrochemical sensor for diethofencarb fungicide monitoring

Diethofencarb (DFC) is widely used in agriculture to fight against plant fungal attacks and enhance food crop production. On the other hand, the National food safety standard has set the overall maximum residual limit (MRL) of DFC to be 1 mg/kg. Hence it becomes essential to limit their usage, and it is vital to quantify the amount of DFC present in real-life samples to safeguard the health and environmental well-being. Here, we introduce a simple hydrothermal procedure for preparing vanadium carbide (VC) anchored by ZnCr-LDH. The sustainably designed electrochemical sensor for the detection of DFC portrayed high electro-active surface area, conductivity, rapid-electron transport ratio, and high ion diffusion parameters. The obtained structural and morphological information confirms the enriched electrochemical activity of the ZnCr-LDH/VC/SPCE towards DFC. The ZnCr-LDH/VC/SPCE electrode has displayed exceptional characteristics with DPV resulting in a vast linear response (0.01-228 μM), and lower LOD (2 nM) with high sensitivity. Real-sample analysis was carried out to demonstrate the specificity of the electrode with an acceptable recovery in both water (±98.75-99.70%) and tomato (±98.00-99.75%) samples.

L-cysteine aided polyaniline capped SrO2 nanoceramics: Assessment of MC3T3-E1-arbitrated osteogenesis and anti-bactericidal efficacy on the polyurethane 2D nanofibrous substrate

Fabricating bioartificial bone graft ceramics retaining structural, mechanical, and bone induction properties akin to those of native stem-cell niches is a major challenge in the field of bone tissue engineering and regenerative medicine. Moreover, the developed materials are susceptible to microbial invasion leading to biomaterial-centered infections which might limit their clinical translation. Here, we successfully developed biomimetic porous scaffolds of polyurethane-reinforcedL-cysteine-anchored polyaniline capped strontium oxide nanoparticles to improve the scaffold's biocompatibility, osteo-regeneration, mechanical, and antibacterial properties. The engineered nanocomposite substrate PU/L-Cyst-SrO₂ @PANI (0.4 wt%) significantly promotes bone repair and regeneration by modulating osteolysis and osteogenesis. ALP activity, collagen-I, ARS staining, as well as biomineralization of MC3T3-E1 cells, were used to assess the biocompatibility and cytocompatibility of the developed scaffolds in vitro, confirming that the scaffold provided a favorable microenvironment with a prominent effect on cell growth, proliferation, and differentiation. Furthermore, osteogenic protein markers were studied using qRT-PCR with expression levels of runt-related transcription factor 2 (RUNX2), secreted phosphoprotein 1 (Spp-I), and collagen type I (Col-I). The overall results suggest that PU/L-Cyst-SrO₂ @PANI (0.4 wt%) scaffolds showed superior interfacial biocompatibility, antibacterial properties, load-bearing ability, and osteoinductivity as compared to pristine PU. Thus, prepared bioactive nanocomposite scaffolds perform as a promising biomaterial substrate for bone tissue regeneration.

Recent biomedical advancements in graphene oxide- and reduced graphene oxide-based nanocomposite nanocarriers

Recently, nanocarriers, including micelles, polymers, carbon-based materials, liposomes, and other substances, have been developed for efficient delivery of drugs, nucleotides, and biomolecules. This review focuses on graphene oxide (GO) and reduced graphene oxide (rGO) as active components in nanocarriers, because their chemical structures and easy functionalization can be valuable assets for in vitro and in vivo delivery. Herein, we describe the preparation, structure, and functionalization of GO and rGO. Additionally, their important properties to function as nanocarriers are presented, including their molecular interactions with various compounds, near-infrared light adsorption, and biocompatibility. Subsequently, their mechanisms and the most appealing examples of their delivery applications are summarized. Overall, GO- and rGO-based nanocomposites show great promise as multipurpose nanocarriers owing to their various potential applications in drug and gene delivery, phototherapy, bioimaging, biosensing, tissue engineering, and as antibacterial agents.

Recent Developments in G-Quadruplex Binding Ligands and Specific Beacons on Smart Fluorescent Sensor for Targeting Metal Ions and Biological Analytes

The G-quadruplex structure is crucial in several biological processes, including DNA replication, transcription, and genomic maintenance. G-quadruplex-based fluorescent probes have recently gained popularity because of their ease of use, low cost, excellent selectivity, and sensitivity. This review summarizes the latest applications of G-quadruplex structures as detectors of genome-wide, enantioselective catalysts, disease therapeutics, promising drug targets, and smart fluorescence probes. In every section, sensing of G-quadruplex and employing G4 for the detection of other analytes were introduced, respectively. Since the discovery of the G-quadruplex structure, several studies have been conducted to investigate its conformations, biological potential, stability, reactivity, selectivity for chemical modification, and optical properties. The formation mechanism and advancements for detecting different metal ions (Na⁺, K⁺, Ag⁺, Tl⁺, Cu⁺/Cu²⁺, Hg²⁺, and Pb²⁺) and biomolecules (AMP, ATP, DNA/RNA, microRNA, thrombin, T4 PNK, RNase H, ALP, CEA, lipocalin 1, and UDG) using fluorescent sensors based on G-quadruplex modification, such as dye labels, artificial nucleobase moieties, dye complexes, intercalating dyes, and bioconjugated nanomaterials (AgNCs, GO, QDs, CDs, and MOF) is described herein. To investigate these extremely efficient responsive agents for diagnostic and therapeutic applications in medicine, fluorescence sensors based on G-quadruplexes have also been employed as a quantitative visualization technique.

Fabricating BiOCl/BiVO4 nanosheets wrapped in a graphene oxide heterojunction composite for detection of an antihistamine in biological samples

Antibiotics are essential medications for human and animal health, as they are used to battle urinary infections and bacterial diseases. Therefore, the rapid determination of antibiotic drugs in biological samples is necessary to address the current clinical challenge. Here, we developed a heterojunction ternary composite of BiOCl/BiVO₄ nanosheets enriched with graphene oxide (BiOCl/BiVO₄@GO) for accurate and minimal-level detection of an antihistamine (promethazine hydrochloride, PMZ) in urine samples. The BiOCl/BiVO₄ nanosheets were prepared by a wet chemical approach using a deep eutectic green solvent. The spectroscopic and analytical methods verified the formation and interaction of the BiOCl/BiVO₄@GO composite. Our results showed that the thoroughly exfoliated BiOCl/BiVO₄@GO composite retained good electrical conductivity and fast charge transfer toward the electrode-electrolyte interface in neutral aqueous media. In addition, the experimental conditions were accurately optimized, and the BiOCl/BiVO₄@GO composite showed excellent electrocatalytic activity toward the oxidation of PMZ. Indeed, the BiOCl/BiVO₄@GO composite demonstrated a good linear response range (0.01-124.7 μM) and a detection level of 3.3 nM with a sensitivity of 1.586 μA μM^-1 cm^-2. In addition, the BiOCl/BiVO₄@GO composite had excellent storage stability, good reproducibility, and reliable selectivity. Finally, the BiOCl/BiVO₄@GO displayed a desirable recovery level of PMZ in urine samples for real-time monitoring.

Fluorescent-based nanosensors for selective detection of a wide range of biological macromolecules: A comprehensive review

Thanks to their unique attributes, such as good sensitivity, selectivity, high surface-to-volume ratio, and versatile optical and electronic properties, fluorescent-based bioprobes have been used to create highly sensitive nanobiosensors to detect various biological and chemical agents. These sensors are superior to other analytical instrumentation techniques like gas chromatography, high-performance liquid chromatography, and capillary electrophoresis for being biodegradable, eco-friendly, and more economical, operational, and cost-effective. Moreover, several reports have also highlighted their application in the early detection of biomarkers associated with drug-induced organ damage such as liver, kidney, or lungs. In the present work, we comprehensively overviewed the electrochemical sensors that employ nanomaterials (nanoparticles/colloids or quantum dots, carbon dots, or nanoscaled metal-organic frameworks, etc.) to detect a variety of biological macromolecules based on fluorescent emission spectra. In addition, the most important mechanisms and methods to sense amino acids, protein, peptides, enzymes, carbohydrates, neurotransmitters, nucleic acids, vitamins, ions, metals, and electrolytes, blood gases, drugs (i.e., anti-inflammatory agents and antibiotics), toxins, alkaloids, antioxidants, cancer biomarkers, urinary metabolites (i.e., urea, uric acid, and creatinine), and pathogenic microorganisms were outlined and compared in terms of their selectivity and sensitivity. Altogether, the small dimensions and capability of these nanosensors for sensitive, label-free, real-time sensing of chemical, biological, and pharmaceutical agents could be used in array-based screening and in-vitro or in-vivo diagnostics. Although fluorescent nanoprobes are widely applied in determining biological macromolecules, unfortunately, they present many challenges and limitations. Efforts must be made to minimize such limitations in utilizing such nanobiosensors with an emphasis on their commercial developments. We believe that the current review can foster the wider incorporation of nanomedicine and will be of particular interest to researchers working on fluorescence technology, material chemistry, coordination polymers, and related research areas.

Prostate cancer biomarker citrate detection using triaminoguanidinium carbon dots, its applications in live cells and human urine samples

Citrate is a tricarboxylate, plays vital role in prostate cancer (PC) and the level of citrate is an indicator for PC identification. Herein, triaminoguanidine carbon dots (TAG-CDs) prepared by one step hydrothermal method and used as a citrate receptor. Notably the TAG-CDs without alkaline treatment were highly fluorescent at pH 7 with high quantum yield (11.3%). TAG-CDs were characterized through TEM, XRD, FT-IR, UV-vis and spectrofluorimetry. It is noted that the average size was of 2.8 nm, the presence of highly disordered carbon, retain the functionality of TAG. The absorbance maxima obtained at 294 nm and good emitting response observed at 396 nm. The Y-aromaticity of receptor guanidinium moiety acts as Lewis acid and have peculiar interaction with Lewis base citrate via electrostatic interaction and also protons in the TAG participate hydrogen bonds with citrate, which causes quenching of TAG-CDs. From the obtained linear quenching equation the LOD was found to be 4 nM. The probe expressed high selectivity, high interference tolerance (500 - fold), fast response in 15 mins and good biocompatible. Finally, TAG-CDs utilized for the intracellular imaging of citrate in live MCF-7 cells, it showed good cytotoxicity and delivered contrast images in presence, absence of citrate. TAG-CDs detected the citrate level in human urine samples, the obtained results are validated with HPLC method.

SPR based gold nano-probe as optical sensor for cysteine detection via plasmonic enhancement in the presence of Cr3

A selective and sensitive detection of L-cysteine (Cys) is an important tool for various biological studies. Here, Au nanoparticles (NPs) were prepared by chemical reduction technique. The probe was developed to detect and quantify Cys in the presence of Cr³⁺ ions which acts as a cross linker. The citrate capped Au NPs probe was analyzed by UV-visible spectrophotometry, TEM, EDAX, FTIR, DLS, XPS and zetasize. The zeta potential and effective size of Au NPs were -41.22 mV and 12 nm, respectively. The Cys interaction with Au NPs showed drastic colour variation from red to purple and colourless with rapid response time of 1 min. The limit of detection (LOD) of Au NPs probe was as low as 0.012 nM. The TEM image of Au NPs after Cys interaction verified the aggregation that resulted in colour change. The XPS core level scans of Au 4f showed 0.3 eV red shift when Cyswas interacted. The Au NPs sensor is highly selective for Cys with excellent reproducibility. Acidic pH slightly favored Cys detection. Further, the probe was applied to estimate Cys quantity from milk, urine, blood and environmental augmented samples in the presence of other amino acids . The study suggests that the proposed Au NPs could detect Cys with high accuracy from various biological samples.

Enhancing K2S2O8 electrochemiluminescence based on silver nanoparticles and zinc metal–organic framework composite (AgNPs@ZnMOF) for the determination of l-cysteine

A silver nanoparticle-doped Zn(ii) metal–organic framework composite (AgNPs@ZnMOF) was investigated as an electrochemiluminescence (ECL) signal enhancer for potassium persulfate. First, ZnMOF was prepared by a one-step hydrothermal method, and then AgNPs@ZnMOF composite was obtained by depositing AgNPs on the surface and interior of ZnMOF. After the AgNPs@ZnMOF composite was modified on the glass carbon electrode (GCE), the cathode luminescence of potassium persulfate on bare GCE was enhanced by 8 times. A dual amplification mechanism provided by Zn(ii) and Ag nanoparticles in the AgNPs@ZnMOF composite has been validated by ECL spectra, fluorescence spectra, and electrochemical methods. The interaction between the sulfhydryl groups in l-cysteine (l-Cys) and AgNPs significantly affects the catalytic luminescence of the AgNPs@ZnMOF composite. Thus, a sensitive ECL method for the determination of l-Cys was developed based on the inhibition effect of l-Cys on the ECL signal within the linear range from 5.0 nM to 1.0 μM and the limit of detection was found to be 2 nM (S/N = 3). The established method has been successfully applied to the determination of l-Cys in human urine.

A silver nanoparticle-doped Zn(ii) metal–organic framework composite (AgNPs@ZnMOF) was investigated as an electrochemiluminescence (ECL) signal enhancer for potassium persulfate.

Toward the Development of Disposable Electrodes Based on Holmium Orthovanadate/f-Boron Nitride: Impacts and Electrochemical Performances of Emerging Inorganic Contaminants

Rare-earth metal orthovanadates have great technological relevance in the family of rare-earth compounds owing to their excellent physical and chemical properties. A significant number of studies have been carried out on this class of compounds to exploit their electrochemical properties in virtue of variable oxidation states. But holmium vanadate (HoV) and its morphology selective synthesis have not been considered, which can have potential applications similar to the rest of the family. In this work, we propose the synthesis of superior architectures of HoV with a functionalized boron nitride (f-BN) nanocomposite. The synergistic effect between HoV and f-BN can have a positive effect on the physical characteristics of the nanocomposite, which can be explored for its electrochemical capacity. Here, HoV incorporated with f-BN is explored for the electrochemical detection of Hg²⁺ ions, which is known for its toxicity-induced environmental health hazards. The structural and compositional revelation reveals higher conductivity and faster electron transfer in the composite, which facilitates a wide working range (0.02-53.8 and 64.73-295.4 μM), low limit of detection (5 nM), higher sensitivity (66.6 μA μM^-1 cm^-2), good selectivity over 10-fold higher concentration of other interfering compounds compared to Hg²⁺ ion concentration, and good cycles stability (30 segments) toward Hg²⁺ ion detection. This also envisages the morphology selective synthesis and utilization of other rare-earth metals, whose electrochemical capacities are unexplored.

Influence of selenium precursors on the formation of iron selenide nanostructures (FeSe2): Efficient Electro-Fenton catalysts for detoxification of harmful organic dyestuffs

In this investigation, a sequences of iron diselenide (FeSe₂) nanomaterials as the competent and highly stable catalysts for the detoxification of aqueous organic dye pollutants such as Congo red (CR) and methylene blue (MB) through Electro-Fenton (EF) process using hydrogen peroxide as an initiator have been studied. The utilized selenium precursors include selenium metal, selenious acid (H₂SeO₃) and selenium dioxide (SeO₂) which were employed for the synthesis of FeSe₂ catalysts through a wet chemical strategy. It has been observed that based on the employed precursors, different morphologies ranges of the FeSe₂ catalysts were obtained: microgranualr particles to nano-stick to nanoflakes. The crystalline nature and phase purity of the obtained FeSe₂ catalysts were determined through XRD, Raman and HR-TEM analyses which confirmed their orthorhombic ferroselite structure. Among the prepared FeSe₂ catalysts, FS-2 (using H₂SeO₃) displayed better porous properties as compared to other catalysts and achieved the highest surface area of 74.68 m²g^-1. The narrow bandgap (0.88 eV) and fast conversion of Fe²⁺/Fe³⁺ cycle of FeSe₂ led CR and MB degradation of 93.3% and 90.4%, respectively. The outcome of this study demonstrates improved catalytic properties of FeSe₂ nanostructures for the efficient detoxification of hazardous and toxic effluents.

A novel tool for the adsorption of dsDNA: Electrochemical reduction of Pd nanoparticles onto reduced-keratin particles extracted from wool wastes

This work outlines the fabrication of a novel electrochemical platform for the dsDNA adsorption, using one of the most sustainable materials, wool fabric waste, and Pd²⁺ ions. To develop a functional material with a significant adsorption capability, the waste wool was subjected to the chemical reduction process, and the keratin-SH (KerSH) particles were extracted in powder form. These particles were used in the adsorption of Pd²⁺ ions by monitoring with the UV-vis spectra. The dispersion of the KerSH-Pd²⁺ particles was subsequently drop-casted onto a glassy carbon electrode (GCE) and electrochemically reduced to the GCE/KerSH-PdNPs composite by chronoamperometry at -0.4 V for 500 s. It was found that the KerSH particles were self-assembled by revealing chemically attractive NH₂ groups after the electrochemical PdNPs deposition. A GCE/KerSH-PdNPs composite was then employed in the electrochemical dsDNA detection by Differential Pulse Voltammetry (DPV), using the oxidation signals of guanine and adenine bases at 0.8 V and 1.2 V, respectively. Accordingly, relatively stable, repeatable, and reproducible dsDNA adsorption was ensured through the positively charged-NH₂ groups of KerSH-PdNPs. This finding reveals the potential of textile waste for various electrochemical applications, such as DNA biosensors for environmental, pharmaceutical, and medicinal fields.

l-cysteine-modified chiral gold nanoparticles promote periodontal tissue regeneration

Gold nanoparticles (AuNPs) with surface-anchored molecules present tremendous potential in tissue regeneration. However, little is known about chiral-modified AuNPs. In this study, we successfully prepared L/D-cysteine-anchored AuNPs (L/D-Cys-AuNPs) and studied the effects of chiral-modified AuNPs on osteogenic differentiation and autophagy of human periodontal ligament cells (hPDLCs) and periodontal tissue regeneration. In vitro, more L-Cys-AuNPs than D-Cys-AuNPs tend to internalize in hPDLCs. L-Cys-AuNPs also significantly increased the expression of alkaline phosphatase, collagen type 1, osteocalcin, runt-related transcription factor 2, and microtubule-associated protein light chain 3 II and decreased the expression of sequestosome 1 in hPDLCs compared to the expression levels in the hPDLCs treated by D-Cys-AuNPs. In vivo tests in a rat periodontal-defect model showed that L-Cys-AuNPs had the greatest effect on periodontal-tissue regeneration. The activation of autophagy in L-Cys-AuNP-treated hPDLCs may be responsible for the cell differentiation and tissue regeneration. Therefore, compared to D-Cys-AuNPs, L-Cys-AuNPs show a better performance in cellular internalization, regulation of autophagy, cell osteogenic differentiation, and periodontal tissue regeneration. This demonstrates the immense potential of L-Cys-AuNPs for periodontal regeneration and provides a new insight into chirally modified bioactive nanomaterials.

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L/D-Cys-AuNPs exert a chirality-dependent effect on hPDLCs.

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L-Cys-AuNPs efficiently induced osteogenic differentiation in hPDLCs.

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L-Cys-AuNPs significantly improved periodontal tissue regeneration.

Engineering of gemcitabine coated nano-graphene oxide sheets for efficient near-infrared radiation mediated in vivo lung cancer photothermal therapy

Gemcitabine (GEM) and its derivatives of deoxycytosine is a promising anticancer candidate which is effective for the treatment of various cancers including lung cancer via cascade targetting Erk/Mek/Raf/Ras pathway and blocking the proliferation of the tumor cells. In this present work, we have described reduced graphene oxide (rGO) in the presence of anticancer utilizing ascorbic acid as reducing agents for lung cancer treatment. GEM reduced graphene oxide (termed as GEM-rGO) has resulted in a smooth and transparent morphological surface, which was confirmed by various spectroscopical investigations. The anticancer drug-loaded rGO has displayed remarkable cytotoxic activities against a panel of lung cancer cell lines when compared to the untreated lung cancer cells. Further, we examined the morphological observation of the cancer cell death was monitored through the fluorescence microscopic examinations. In addition, the cell deaths of the lung cancer cells were observed by the flow cytometry analyses. In addition, the non-toxic nature of potent GEM-rGO and GEM-rGO + NIR was confirmed by in vivo systemic toxicity analysis. Besides, the higher safety feature of the GEM-rGO and GEM-rGO + NIR was evidenced by histological analyses of the mice organs. The subcutaneous injection of GEM-rGO and GEM-rGO + NIR into mice bearing A549 xenografts more effectively inhibited the tumor than the free GEM. Based on the outcomes, we can summarise that the GEM reduced graphene oxide (GEM-rGO) can be used as a promising drug candidate for the treatment of lung cancer in the future.

Applications of advanced materials in bio-sensing in live cells: Methods and applications

A wide variety of species, such as different ions, reactive oxygen species, and biomolecules play critical roles in many cell functions. These species are responsible for a range of cellular functions such as signaling, and disturbed levels could be involved in many diseases, such as diabetes, cancer, neurodegeneration etc. Thus, sensitive and specific detection methods for these biomarkers could be helpful for early disease detection and mechanistic investigations. New ultrasensitive sensors for detection of markers within living cells are a growing field of research. The present review provides updates in live cell-based biosensing, which have been published within the last decade. These sensors are mainly based on carbon, gold and other metals, and their physicochemical advantages and limitations are discussed. Advanced materials can be incorporated into probes for the detection of various analytes in living cells. The sensitivity is strongly influenced by the intrinsic properties of the nanomaterials as well their shape and size. The mechanisms of action and future challenges in the developments of new methods for live cell based biosensing are discussed.

Computational studies and biosensory applications of graphene-based nanomaterials: a state-of-the-art review

Graphene, graphene oxide (GO) and graphene quantum dots (GQDs) are expected to play a vital role in the diagnosis of severe ailments. Computer-based simulation approaches are helpful for understanding theoretical tools prior to experimental investigation. These theoretical tools still have a high computational requirement. Thus, more efficient algorithms are required to perform studies on even larger systems. The present review highlights the recent advancement in structural confinement using computer simulation approaches along with biosensory applications of graphene-based materials. The computer simulation approaches help to identify the interaction between interacting molecules and sensing elements like graphene sheets. The simulation approach reduces the wet-lab experiment time and helps to predict the interaction and interacting environment. The experimental investigation can be tuned at a molecular level easily to predict small changes in structural configuration. Here, the molecular simulation study could be useful as an alternative to actual wet experimental approaches. The sensing ability of graphene-based materials is a result of interactions like hydrogen bonding, base-base interaction, and base-to-pi interaction to name a few. These interactions help in designing and engineering a substrate for sensing of various biomolecules.

Highly sensitive determination of cancer toxic mercury ions in biological and human sustenance samples based on green and robust synthesized stannic oxide nanoparticles decorated reduced graphene oxide sheets

This work proposes the conventional sonochemical synthesis of nanoparticles of tin (IV) oxide on reduced graphene oxide (rGOS@SnO₂) influencing the formation of a composite with enhanced properties. The combination of SnO₂ nanoparticles with rGOS weakens the accumulation in layered structures of the latter system, which leads to better exposure of SnO₂ active sites and thus increases the conductivity of rGOS@SnO₂ composite. This validates the improved electro-catalytic activity of the composite based on previous reports for its successful utilization in the electrochemical determination of toxic contaminants. The quantitative determination of mercury ions, through the use of the electrochemical sensor based on rGOS@SnO₂ manifests several advantages such as simple operator, promptness, cost effectiveness and time independency when compared to other traditional techniques. The fabricated sensor displays two wide linear responses in the range of 0.25-705.3 μM for mercury ions, with a rapid response time about 1 s, and with a high sensitivity of 10.18 μA μM^-1 cm^-2 under optimized conditions. The accumulation of traces of mercury in the bodies of fish in the marine eco system marks the significance of its detection in real samples. The satisfactory results of the proposed sensor establish the supreme efficacy of layered nanomaterials in conjunction with nanoparticles for the simple, rapid and efficient detection of pollutants in food and biological samples.

Application of Zero-Dimensional Nanomaterials in Biosensing

Zero-dimensional (0D) nanomaterials, including graphene quantum dots (GQDs), carbon quantum dots (CQDs), fullerenes, inorganic quantum dots (QDs), magnetic nanoparticles (MNPs), noble metal nanoparticles, upconversion nanoparticles (UCNPs) and polymer dots (Pdots), have attracted extensive research interest in the field of biosensing in recent years. Benefiting from the ultra-small size, quantum confinement effect, excellent physical and chemical properties and good biocompatibility, 0D nanomaterials have shown great potential in ion detection, biomolecular recognition, disease diagnosis and pathogen detection. Here we first introduce the structures and properties of different 0D nanomaterials. On this basis, recent progress and application examples of 0D nanomaterials in the field of biosensing are discussed. In the last part, we summarize the research status of 0D nanomaterials in the field of biosensing and anticipate the development prospects and future challenges in this field.

Nanomolar detection of biothiols via turn-ON fluorescent indicator displacement

A simple, visual colour and turn-ON fluorescent method for the detection of biothiols under physiological conditions is reported. The chemosensing is achieved on the basis of the displacement of BODIPY dyes from the surface of gold nanoparticles.

Nanomaterials for Healthcare Biosensing Applications

In recent years, an increasing number of nanomaterials have been explored for their applications in biomedical diagnostics, making their applications in healthcare biosensing a rapidly evolving field. Nanomaterials introduce versatility to the sensing platforms and may even allow mobility between different detection mechanisms. The prospect of a combination of different nanomaterials allows an exploitation of their synergistic additive and novel properties for sensor development. This paper covers more than 290 research works since 2015, elaborating the diverse roles played by various nanomaterials in the biosensing field. Hence, we provide a comprehensive review of the healthcare sensing applications of nanomaterials, covering carbon allotrope-based, inorganic, and organic nanomaterials. These sensing systems are able to detect a wide variety of clinically relevant molecules, like nucleic acids, viruses, bacteria, cancer antigens, pharmaceuticals and narcotic drugs, toxins, contaminants, as well as entire cells in various sensing media, ranging from buffers to more complex environments such as urine, blood or sputum. Thus, the latest advancements reviewed in this paper hold tremendous potential for the application of nanomaterials in the early screening of diseases and point-of-care testing.

Designing an "Off-On" Fluorescence Sensor Based on Cluster-Based CaII-Metal-Organic Frameworks for Detection of l-Cysteine in Biological Fluids

Recently, luminescent metal-organic framework (MOF) materials have attracted considerable attention in fluorescence sensing. In this essay, we prepared a new cluster-based Ca^II-MOFs {[Ca_1.5(μ₈-HL₁)(DMF)₂]·DMF}_n (1) with good water dispersibility, excellent photoluminescence properties (FL quantum yield of 20.37%) and great fluorescence stability. Further, it was employed to design as an "off-on" fluorescence sensor for sensitive detection of l-cysteine. This proposed strategy was that fluorescence of Ca^II-MOFs 1 was quenched for providing a low fluorescence background by the introduction of Pb²⁺ forming the Ca^II-MOFs 1/Pb²⁺ hybrid system. The quenching effect could be ascribed to the static quenching mechanism because of the formation of ground-state complexes and coordination interactions between the free carboxyl of H₄L₁ ligands of Ca^II-MOFs 1 and Pb²⁺. Then, with the addition of l-cysteine into the Ca^II-MOFs 1/Pb²⁺ hybrid system, the fluorescence signal was immediately restored. This result was because the Pb²⁺ was gradually released from the hybrid system by chelation interactions between the -SH groups of l-cysteine and Pb²⁺. This method received a relative wide linear range varying from 0.05 to 40 μM and a low detection limit of 15 nM for detection of l-cysteine. This proposed strategy was also successfully applied to detect l-cysteine in human serum samples with satisfactory recoveries from 95.9 to 101.5%.

Fluorometric determination and intracellular imaging of cysteine by using glutathione capped gold nanoclusters and cerium(III) induced aggregation

A turn-on fluorometric method is described for selective and sensitive detection of cysteine (Cys). Gold nanoclusters (Au NCs) capped with glutathione (GSH) are used as a fluorescent probe. If Ce³⁺ ion are present, they will bind to the carboxy groups of the GSH-capped Au NC. This results in aggregation-induced emission enhancement (AIEE), best measured at excitation/emission wavelengths of 360/575 nm. On addition of Cys, which has less steric hindrance compared with GSH and higher affinity for Ce³⁺, it will bind to Ce³⁺ through the carboxyl group and link with Au NCs via Au-S bond. Hence, the AIEE is increased and Cys can be quantified via this effect with a linear response in the 0.4-120 μmol L^-1 Cys concentration range and a detection limit of 0.15 μmol L^-1. Graphical abstract Schematic presentation of cysteine detection via the Ce³⁺-triggered aggregation of glutathione capped gold nanoclusters which leads to increased yellow fluorescence.

Applications of Nanosheets in Frontier Cellular Research

Several types of nanosheets, such as graphene oxide (GO) nanosheet, molybdenum disulfide (MoS₂) and poly(l-lactic acid) (PLLA) nanosheets, have been developed and applied in vitro in cellular research over the past decade. Scientists have used nanosheet properties, such as ease of modification and flexibility, to develop new cell/protein sensing/imaging techniques and achieve regulation of specific cell functions. This review is divided into three main parts based on the application being examined: nanosheets as a substrate, nanosheets as a sensitive surface, and nanosheets in regenerative medicine. Furthermore, the applications of nanosheets are discussed, with two subsections in each section, based on their effects on cells and molecules. Finally, the application prospects of nanosheets in cellular research are summarized.

A novel dual-emission fluorescent nanohybrid containing silica nanoparticles and gold nanoclusters for ratiometric determination of cysteine based on turn-on fluorescence strategy

A novel fluorescence sensor SiO₂NPs/AuNCs nanohybrid has been used developed for ratiometric visual detection of Cys.