Protein capped Cu nanoclusters-SWCNT nanocomposite as a novel candidate of high performance platform for organophosphates enzymeless biosensor

Enzyme-mimic catalytic activities and biomedical applications of noble metal nanoclusters

Noble metal (e.g., Au and Ag) nanoclusters (NCs), which exhibit structural complexity and hierarchy comparable to those of natural proteins, have been increasingly pursued in artificial enzyme research. The protein-like structure of metal NCs not only ensures enzyme-mimic catalytic activity, including peroxidase-, catalase-, and superoxide dismutase-mimic activities, but also affords an unprecedented opportunity to correlate the catalytic performance with the cluster structure at the molecular or atomic levels. In this review, we aim to summarize the recent progress in programming and demystify the enzyme-mimic catalytic activity of metal NCs, presenting the state-of-the-art understandings of the structure-property relationship of metal NC-based artificial enzymes. By leveraging on a concise anatomy of the hierarchical structure of noble metal NCs, we manage to unravel the structural origin of the catalytic performance of metal NCs. Noteworthily, it has been proven that the surface ligands and metal-ligand interface of metal NCs are instrumental in influencing enzyme-mimic catalytic activities. In addition to the structure-property correlation, we also discuss the synthetic methodologies feasible to tailoring the cluster structure at the atomic level. Prior to the closure of this review with our perspectives in noble metal NC-based artificial enzymes, we also exemplify the biomedical applications based on the enzyme-mimic catalysis of metal NCs with the theranostics of kidney injury, brain inflammation, and tumors. The fundamental and methodological advancements delineated in this review would be conducive to further development of metal NCs as an alternative family of artificial enzymes.

Recent advances in the biomolecules mediated synthesis of nanoclusters for food safety analysis

The development of nanoclusters based on incorporating biomolecules like proteins, lipids, enzymes, DNA, surfactants, and chemical stabilizers creates a stable and high fluorescence bio-sensors promising future due to their high sensitivity, high level of detection and better selectivity. This review addresses a comprehensive and systematic overview of the recent development in synthesizing metal nanocluster by various strategized synthesis techniques. Significantly, the application of nanometal clusters for the detection of various food contaminants such as microorganisms, antibodies, drugs, pesticides, metal contaminants, amino acids, and other food flavors have been discussed briefly concerning the detection techniques, sensitivity, selectivity, and lower limit of detection. The review further gives a brief account on the future prospects in the synthesis of novel metal nanocluster-based biosensors, and their advantages, shortcomings, and potential perspectives toward their application in the field of food safety analysis.

AuNPs and graphdiyne nanocomposite as robust electrocatalyst for methyl parathion detection in real samples

The present work describes a simple and rapid synthesis method of gold nanoparticles and graphdiyne (AuNPs@GDY) nanocomposites including porous structure. Moreover, the synthesized AuNPs@GDY material was decorated on the glassy carbon electrode (GCE) with a drop coating method to construct a non-enzymatic electrochemical pesticides sensor. The micro-morphology and elemental composition of the materials were characterized by transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). The electrocatalysis and conductivity of the material were studied with cyclic voltammetry (CV) and impedance method, respectively. The properties of the sensor were investigated by CV and differential pulse voltammetry (DPV). The results showed that AuNPs@GDY exhibited excellent electrocatalytic ability for methyl parathion in a wide linear range (from 0.25 ng/mL to 24.43 μg/mL) and low limit of detection value (6.2 pg/mL). Furthermore, the DPV method used in this paper was accurate and sensitive, and could be used for routine quality control of methyl parathion in kiwi fruit and tomato samples.

New analytical strategies Amplified with 2D carbon nanomaterials for electrochemical sensing of food pollutants in water and soils sources

Pharmaceutical and food pollutants have threatened global health. Pharmacotherapy has left a positive impression in the field of health and life of people and animals. However, the many unresolved problems brought along with residues of pharmaceuticals in the environmental and food. Consumption of the world's freshwater resources, toxic chemicals, air pollution, plastic waste directly affects water and soil resources. Pesticides have a wide role in pollutants. Therefore, the determination of pesticides is significant to eliminate their negative effects on living things. Nowadays, there are many analytical methods available. However, new analysis methods are still being researched due to certain limitations of traditional methods. Electrochemical sensors have drawn attention because of their superior properties, such as short analysis time, affordability, high sensitivity, and selectivity. The development of new analytical strategies for assessing risks from pharmaceutical to food pollutants in water and soil sources is important for the measurement of different pollutants. Moreover, the 2D-carbon nanomaterials used in the development of electrochemical sensors are widely utilized to enlarge the surface area, increase porosity, and make easy immobilization. Graphene (graphene derivations) and carbon nanotubes integrated nanosensors are widely used for the determination of pesticides. 2D-carbon nanomaterials can be tailored according to the purpose of the study. The characterization and synthesis methods of 2D-carbon nanomaterials are widely explained. Furthermore, enzyme nanobiosensors, especially Acetylcholinesterase (AChE), are widely used to determine pesticides. The three main topics are focused on in this review: 2D-carbon nanomaterials, pesticides that threaten life, and the application of 2D-carbon nanomaterials-based electrochemical sensors. The various developed 2D-carbon nanomaterials-based electrochemical sensors were applied in pharmaceutical forms, fruits, tap/lake water, beverages, and soils sources. This work aims to indicate the recently published paper related to pesticide analysis and highlight the importance of 2D-nanomaterials on sensors.

A novel paraoxon imprinted electrochemical sensor based on MoS2NPs@MWCNTs and its application to tap water samples

Organophosphorus pesticides are widely utilized in agricultural fertility. However, their long-term accumulations result in serious damage to human health and ecological balance. Paraoxon (PAR) can block acetylcholinesterase in the human body, resulting in death. Thus, in this study, a molecularly imprinted electrochemical PAR sensor based on multiwalled carbon nanotubes (MWCNTs)/molybdenum disulfide nanoparticles (MoS₂NPs) nanocomposite (MoS₂NPs@MWCNTs) was proposed for selective tap water determination. A hydrothermal fabrication approach was firstly implemented to prepare MoS₂NPs@MWCNTs nanocomposite. Afterwards, the formation of PAR imprinted electrochemical electrode was performed on nanocomposite modified glassy carbon electrode (GCE) in presence of PAR as template and pyrrole (Py) as a monomer by cyclic voltammetry (CV) technique. Just after determining the physicochemical features of as-fabricated nanostructures by scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), Raman spectroscopy, and atomic force microscopy (AFM), the electrochemical behavior of the fabricated sensors was determined through CV, differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). The suggested imprinted electrode provided the acceptable limit of quantification (LOQ) and limit of detection (LOD) values of 1.0 × 10^-11 M, and 2.0 × 10^-12 M, respectively. As a consequence, the proposed PAR imprinted electrochemical sensor can be offered for the determining safe tap water and its utility.

High-performance electrochemical sensing of hazardous pesticide Paraoxon using BiVO4 nano dendrites equipped catalytic strips

Paraoxon is one of the pesticide that can induce toxicity to nervous system of living organisms. In this work, we focused on synthesizing the catalyst Bismuth Vanadate with the properties that can sense the presence of organophosphorus compounds and characterized them with various characterization methods. The structural studies done by XRD, UV spectroscopy and FTIR spectroscopy. Morphological studies were carried by SEM and TEM. Elemental analysis using XPS spectra. The proposed electrocatalyst was successfully applied as the active electrode material modifying the screen printed carbon electrode for electrochemical sensor applications. The results of the studies indicate that bismuth vanadate modified electrode exhibited four electron transfer process for reduction of nitro group and this lead to the superior electrochemical sensing performance for ethyl Paraoxon with a detection limit of 0.03 μM and good sensitivity 0.345 μA μM^-1 cm^-2 with excellent reproducibility, repeatability, stability and selectivity over common interferents. Furthermore, the practical application was successfully carried using the proposed modified strips to determine Paraoxon presence in the river water sample with satisfactory results. This proposed catalyst can act as a desirable candidate for the rapid electrochemical sensor.

Construction of cationic polyfluorinated azobenzene/reduced graphene oxide for simultaneous determination of dopamine, uric acid and ascorbic acid

A highly sensitive cationic polyfluorinated azobenzene/reduced graphene oxide (C₃F₇-azo⁺/RGO) nanocomposite electrochemical sensor for simultaneous detection of dopamine (DA), ascorbic acid (AA) and uric acid (UA) was successfully synthesized using a facile exfoliation/restacking method. The nanocomposite is self-assembled from oppositely charged graphene oxide nanosheets (GO) and polyfluorinated azobenzene cations (C₃F₇-azo⁺), and then obtained by electrochemical reduction. The structure and electrochemical properties were characterized by X-ray diffraction (XRD), energy dispersive spectrometer analysis (EDS), transmission electron microscope (TEM) and scanning electron microscope (SEM). The electrochemical property of C₃F₇-azo⁺/RGO was characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). It can be clearly seen from experimental results that C₃F₇-azo⁺/RGO-modified electrode (C₃F₇-azo⁺/RGO/GCE) can detect DA, AA and UA simultaneously, and has good stability and anti-interference performance. The detection limits are 65 nM, 8 nM and 11 nM for DA, AA and UA in the ranges 57.28-134.28 μM, 0.04-6.01 μM, 9.23-23.45 μM, respectively.

Stable Luminescent Poly(Allylaminehydrochloride)-Templated Copper Nanoclusters for Selectively Turn-Off Sensing of Deferasirox in β-Thalassemia Plasma

Highly stable and facile one-pot copper nanoclusters (Cu NCs) coated with poly(allylamine hydrochloride) (PAH) have been synthesized for selectively sensing deferasirox (DFX) in β-thalassemia plasma. DFX is an important drug used for treating iron overloading in β-thalassemia, but needs to be monitored due to certain toxicity. In this study, the PAH-Cu NCs showed highly stable fluorescence with emission wavelengths at 450 nm. The DFX specifically interacted with the copper nanocluster to turn off the fluorescence of the PAH-Cu NCs, and could be selectively quantified through the fluorescence quenching effect. The linear range of DFX in plasma analyzed by PAH-Cu NCs was 1.0-100.0 µg/mL (r = 0.985). The relative standard deviation (RSD) and relative error (RE) were lower than 6.51% and 7.57%, respectively, showing excellent reproducibility of PAH-Cu NCs for sensing DFX in plasma. This method was also successfully applied for an analysis of three clinical plasma samples from β-thalassemia patients taking DFX. The data presented high similarity with that obtained through a capillary electrophoresis method. According to the results, the PAH-Cu NCs could be used as a tool for clinically sensing DFX in human plasma for clinical surveys.

Electrochemical biosensor based on CuPt alloy NTs-AOE for the ultrasensitive detection of organophosphate pesticides

The electrode material is vital for the performance of the electrochemical biosensor. Lately, many nanomaterials have been developed to improve the sensitivity and detection efficiency of the biosensors. In this work, a kind of one-dimensional nanomaterials, the CuPt alloy nanotubes with an open end (CuPt alloy NTs-AOE), was explored. The nanotubes with an open end can provide a larger electrochemical active surface area and more active sites for the immobilization of enzyme. The CuPt alloy displays excellent conductivity and catalytic activity. In addition, the Cu shows the great affinity to thio-compounds, which can greatly enhance the detection efficiency and sensitivity. As a result, the prepared biosensor demonstrates the wider linear range of 9.98 × 10^-10-9.98 × 10^-5g l^-1for fenitrothion and 9.94 × 10^-11-9.94 × 10^-4g l^-1for dichlorvos (as model OPs ) and with the lower detection limit of 1.84 × 10^-10g l^-1and 6.31 × 10^-12g l^-1(S/N = 3), respectively. Besides, the biosensor has been used to detect the real samples and obtains satisfactory recoveries (95.58%-100.56%).

Ligand-protected nanoclusters and their role in agriculture, sensing and allied applications

Nano biotechnology, when coupled with green chemistry, can revolutionize human life because of the vast opportunities and benefits it can offer to the quality of human life. Luminescent metal nanoclusters (NCs) have recently developed as a potential research area with applications in different areas like medical, imaging, sensing etc. Recently these new candidates have proved to be beneficial in the food supply chain enabling controlled release of nutrients, pesticides and as nanosensors for the detection of contaminants and play roles in healthy food storage and maintaining food quality. An assortment of nanomaterials has been employed for these applications and reviews have been published on the use of nanotechnology in agriculture. Ligand-protected metal nanoclusters are a distinctive class of small organic-inorganic nanostructures that garnered immense research interest in recent years owing to their stability at specific "magic size" compositions along with tunable properties that make them promising candidates for a wide range of nanotechnology-based applications. This review tries to consolidate the recent developments in the area of ligand-protected nanoclusters in connection with the detection of pesticides, food contaminants, heavy metal ions and plant growth monitoring for healthy agricultural practices. Its antimicrobial activity to manage the microbial contamination is highlighted. The review also throws light on the various perspectives by which food production and allied areas will be transformed in future.

Synthesis of Copper Nanocluster and Its Application in Pollutant Analysis

Copper nanoclusters (Cu NCs) with their inherent optical and chemical advantages have gained increasing attention as a kind of novel material that possesses great potential, primarily in the use of contaminants sensing and bio-imaging. With a focus on environmental safety, this article comprehensively reviews the recent advances of Cu NCs in the application of various contaminants, including pesticide residues, heavy metal ions, sulfide ions and nitroaromatics. The common preparation methods and sensing mechanisms are summarized. The typical high-quality sensing probes based on Cu NCs towards various target contaminants are presented; additionally, the challenges and future perspectives in the development and application of Cu NCs in monitoring and analyzing environmental pollutants are discussed.

Applications of Filled Single-Walled Carbon Nanotubes: Progress, Challenges, and Perspectives

Single-walled carbon nanotubes (SWCNTs), which possess electrical and thermal conductivity, mechanical strength, and flexibility, and are ultra-light weight, are an outstanding material for applications in nanoelectronics, photovoltaics, thermoelectric power generation, light emission, electrochemical energy storage, catalysis, sensors, spintronics, magnetic recording, and biomedicine. Applications of SWCNTs require nanotube samples with precisely controlled and customized electronic properties. The filling of SWCNTs is a promising approach in the fine-tuning of their electronic properties because a large variety of substances with appropriate physical and chemical properties can be introduced inside SWCNTs. The encapsulation of electron donor or acceptor substances inside SWCNTs opens the way for the Fermi-level engineering of SWCNTs for specific applications. This paper reviews the recent progress in applications of filled SWCNTs and highlights challenges that exist in the field.

Recent advancements in the detection of organophosphate pesticides: a review

Organophosphorus pesticides (OPPs) are generally utilized for the protection of crops from pests. Because the use of OPPs in various agricultural operations has expanded dramatically, precise monitoring of their concentration levels has become the critical issue, which will help in the protection of ecological systems and food supply. However, the World Health Organization (WHO) has classified them as extremely dangerous chemical compounds. Taking their immense use and toxicity into consideration, the development of easy, rapid and highly sensitive techniques is necessary. Despite the fact that there are numerous conventional ways for detecting OPPs, the development of portable sensors is required to make routine analysis considerably more convenient. Some of these advanced techniques include colorimetric sensors, fluorescence sensors, molecular imprinted polymer-based sensors, and surface plasmon resonance-based sensors. This review article specifically focuses on the colorimetric, fluorescence and electrochemical sensors. In this article, the sensing strategies of these developed sensors, analytical conditions and their respective limit of detection are compiled.

Bio-inspired gelatin/single-walled carbon nanotube nanocomposite for transient electrochemical energy storage: An approach towards eco-friendly and sustainable energy system

Wide-scale production of non-biodegradable e-waste from electrical appliances are causing great harm to the environment. The use of bio-polymer based nanomaterials may offer a promising approach for the fabrication of eco-friendly sustainable devices. In this work, gelatin/single walled carbon nanotube (Gel/SWCNT) nanocomposites were prepared by a simple and economic aqueous casting method. The effect of SWCNT on the structural, surface-morphological, electrical, and electrochemical properties of the nanocomposite was studied. Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscope (FESEM) showed an improved degree of interaction between the SWCNTs and Gel matrix. The surface wettability of the nanocomposites was found to be changed from hydrophilic to hydrophobic in nature due to the incorporation of SWCNTs into the Gel matrix. The incorporation of SWCNTs was also found to reduce the DC resistivity of the nanocomposite by 4 orders of magnitude. SWCNTs also increase the specific capacitance of the nanocomposite from 124 mF/g to 467 mF/g at a current density of 0.3 mA/g. The electrochemical impedance spectroscopy analysis revealed an increase of the pseudo-capacitance increased from 9.4 μF to 31 μF due to the incorporation of SWCNT. The Gel/SWCNT nanocomposite showed cyclic stability with capacitive retention of about 98% of its initial capacitance after completing 2000 charging/discharging cycles at a current density of 100 mA/g. The nanocomposite completely dissolves in water within 12 h, demonstrates it as a promising candidate for transient energy storage applications. The Gel/SWCNT nanocomposite may offer a new route for the synthesis of eco-friendly, biodegradable, and transient devices.

Copper nanoclusters: designed synthesis, structural diversity, and multiplatform applications

Atomically precise metal nanoclusters (MNCs) have gained tremendous research interest in recent years due to their extraordinary properties. The molecular-like properties that originate from the quantized electronic states provide novel opportunities for the construction of unique nanomaterials possessing rich molecular-like absorption, luminescence, and magnetic properties. The field of monolayer-protected metal nanoclusters, especially copper, with well-defined molecular structures and compositions, is relatively new, about two to three decades old. Nevertheless, the massive progress in the field illustrates the importance of such nanoobjects as promising materials for various applications. In this respect, nanocluster-based catalysts have become very popular, showing high efficiencies and activities for the catalytic conversion of chemical compounds. Biomedical applications of clusters are an active research field aimed at finding better fluorescent contrast agents, therapeutic pharmaceuticals for the treatment and prevention of diseases, the early diagnosis of cancers and other potent diseases, especially at early stages. A huge library of structures and the compositions of copper nanoclusters (CuNCs) with atomic precisions have already been discovered during last few decades; however, there are many concerns to be addressed and questions to be answered. Hopefully, in future, with the combined efforts of material scientists, inorganic chemists, and computational scientists, a thorough understanding of the unique molecular-like properties of metal nanoclusters will be achieved. This, on the other hand, will allow the interdisciplinary researchers to design novel catalysts, biosensors, or therapeutic agents using highly structured, atomically precise, and stable CuNCs. Thus, we hope this review will guide the reader through the field of CuNCs, while discussing the main achievements and improvements, along with challenges and drawbacks that one needs to face and overcome.

Recent Advances in Bio-Templated Metallic Nanomaterial Synthesis and Electrocatalytic Applications

Developing metallic nanocatalysts with high reaction activity, selectivity and practical durability is a promising and active subfield in electrocatalysis. In the classical "bottom-up" approach to synthesize stable nanomaterials by chemical reduction, stabilizing additives such as polymers or organic surfactants must be present to cap the nanoparticle to prevent material bulk aggregation. In recent years, biological systems have emerged as green alternatives to support the uncoated inorganic components. One key advantage of biological templates is their inherent ability to produce nanostructures with controllable composition, facet, size and morphology under ecologically friendly synthetic conditions, which are difficult to achieve with traditional inorganic synthesis. In addition, through genetic engineering or bioconjugation, bio-templates can provide numerous possibilities for surface functionalization to incorporate specific binding sites for the target metals. Therefore, in bio-templated systems, the electrocatalytic performance of the formed nanocatalyst can be tuned by precisely controlling the material surface chemistry. With controlled improvements in size, morphology, facet exposure, surface area and electron conductivity, bio-inspired nanomaterials often exhibit enhanced catalytic activity towards electrode reactions. In this Review, recent research developments are presented in bio-approaches for metallic nanomaterial synthesis and their applications in electrocatalysis for sustainable energy storage and conversion systems.

Label-Free Detection of Staphylococcus aureus Based on Bacteria-Imprinted Polymer and Turn-on Fluorescence Probes

The effective identification and quantitative determination of Staphylococcus aureus is a major public health concern. Here, an innovative strategy that combines a bacteria-imprinted polydimethylsiloxane film for bacterial recognition and fluorescence resonance energy transfer platform for turn-on fluorescence sensing is demonstrated. The bacteria-imprinted polydimethylsiloxane film was facilely fabricated to generate corresponding specific sites on the polydimethylsiloxane surface via stamp imprinting using Staphylococcus aureus as template followed by modification with 1H,1H,2H,2H-perfluorooctyltriethoxysilane. The fluorescence resonance energy transfer platform was developed through electrostatic interaction between citrate-functional copper clusters and dopamine-stabilized gold nanoparticles. When the Staphylococcus aureus are present, the 1H,1H,2H,2H-perfluorooctyltriethoxysilane-modified bacteria-imprinted polydimethylsiloxane film can precisely capture the target; subsequently, the negatively charged bacteria compete with citrate-functional copper clusters and bind to dopamine-stabilized gold nanoparticles, leading to the fluorescence recovery of citrate-functional copper clusters. The entire detection process was achieved within 135 min, showing a wide linear calibration response from 10 to 1 × 10⁷ cfu mL^-1 with a low detection limit of 11.12 cfu mL^-1. Furthermore, the recoveries from spiked samples were from 97.7 to 101.90% with relative standard derivations lower than 10%. The established label-free assay of measuring Staphylococcus aureus is rapid, sensitive, specific, and efficient.

Magnetic restricted-access carbon nanotubes for the extraction/pre-concentration of organophosphates from food samples followed by spectrophotometric determination

In this work, magnetic restricted-access carbon nanotubes (M-RACNTs) were synthesized, characterized and used in the dispersive solid-phase extraction (d-SPE) of organophosphate pesticides (OPPs) from food samples (broccoli, eggplant, cauliflower, and soy milk), followed by spectrophotometric determination in a flow injection analysis system. Fe₃O₄ nanoparticles were incorporated in the multi-walled carbon nanotubes employing dimethylformamide. The dimethylformamide was used as a solvent in the incorporation process, forming the suspension of both particles. The resulting M-CNTs were covered with an external bovine serum albumin (BSA) layer, chemically crosslinked. M-RACNTs were able to efficiently capture OPPs, excluding about 95% of the proteins from food matrices. The analyses were carried out in a flow injection analysis system (FIA), with the spectrophotometric detection (at 560 nm) of the complex formed by the reaction between OPPs, N-bromosuccinimide and rhodamine B. A fractional factorial design method was used to optimize the experimental parameters. The addition/recovery test showed results from 95.5% to 108.9%. Accuracies were checked by comparing the results obtained with the proposed and standard HPLC methods, which were in agreement. The proposed method was linear from 5 to 90 μg L^-1 of OPPs, with limits of detection and quantification of 0.74 and 5 μg L^-1 and precision of 3.67%, expressed as relative standard deviation. The pre-concentration factor was about 164 times.

A La3+-doped TiO2 nanoparticle decorated functionalized-MWCNT catalyst: novel electrochemical non-enzymatic sensing of paraoxon-ethyl

The development of novel chemical sensors for pesticide detection has found particular application in the area of environmental monitoring. However, designing primary sensors as weapons to destroy contaminants (e.g., paraoxon-ethyl) in water and soil remains a challenge. Herein, we show different strategies, such as modification of TiO₂ NPs through La³⁺ doping and decoration of f-MWCNTs, which can provide possibilities for notable developments in electrocatalytic performance. Using this approach, we introduce an active La³⁺ doped TiO₂ NP decorated f-MWCNT electrocatalyst for pollutant monitoring applications. Thereby, our findings move towards an outstanding LOD (0.0019 μM) performance, high selectivity, and exceptional sensitivity (7.6690 μA μM^-1 cm^-2) on an as-presented catalytic platform for a PE sensor. Interestingly, the practical applicability of the suggested catalyst shows a rich sensing platform for PE-contaminated environmental samples.

Effective Photodynamic Therapy for Colon Cancer Cells Using Chlorin e6 Coated Hyaluronic Acid-Based Carbon Nanotubes

Colon cancer is the third major cancer contributor to mortality worldwide. Nanosized particles have attracted attention due to their possible contribution towards cancer treatment and diagnosis. Photodynamic therapy (PDT) is a cancer therapeutic modality that involves a light source, a photosensitizer and reactive oxygen species. Carbon nanotubes are fascinating nanocarriers for drug delivery, cancer diagnosis and numerous potential applications due to their unique physicochemical properties. In this study, single walled carbon nanotubes (SWCNTs) were coupled with hyaluronic acid (HA) and chlorin e6 (Ce6) coated on the walls of SWCNTs. The newly synthesized nanobiocomposite was characterized using ultraviolet-visible spectroscopy, Fourier transform electron microscopy (FTIR), X-ray diffraction analysis (XRD), particle size analysis and zeta potential. The loading efficiency of the SWCNTs-HA for Ce6 was calculated. The toxicity of the nanobiocomposite was tested on colon cancer cells using PDT at a fluence of 5 J/cm² and 10 J/cm². After 24 h, cellular changes were observed via microscopy, LDH cytotoxicity assay and cell death induction using annexin propidium iodide. The results showed that the newly synthesized nanobiocomposite enhanced the ability of PDT to be a photosensitizer carrier and induced cell death in colon cancer cells.

Specific detection and discrimination of dithiocarbamates using CTAB-encapsulated fluorescent copper nanoclusters

The continuous increase of annual dithiocarbamates consumption and a severe underestimation of ditihocarbamates threats urge the establishment of monitoring network for dithiocarbamates residue based on neoteric facile, rapid, inexpensive and applicable detection method. Current rapid detection methods based on enzyme or Au/Ag nanoparticles suffer either from low sensitivity or from poor selectivity, greatly limiting their practical applications. In this work, a paper-based versatile chemosensor based on CTAB-encapsulated fluorescent cooper nanocluster was developed for the specific detection and discrimination of dithiocarbamates. The as-synthesized cooper nanoclusters were investigated highly sensitive and selective to dithiocarbamates both in colorimetric and fluorometric detecting channel. In addition, the as-fabricated sensor can be used to evaluate total amounts of dithiocarbamates, even for real samples. By integrating colorimetry and fluorometry, a binary concentration-based optical electronic tongue was established for the discrimination of different dithiocarbamates.

Sepsis progression monitoring via human serum fibronectin detection based on sandwich-type electrochemical immunosensor

Sepsis has always been a severe clinical problem in critical care medicine due to its rather high mortality and poor prognosis. The current study reported for the first time a practical immunosensor for fibronectin (FN) detection in human serum by electrochemistry. A simple but robust sandwich-type strategy was employed without any complex design or material modifications, which exhibited a linear calibration plot over the 15.625-500 ng/mL concentration range and a detection limit of 15 ng/mL. The results showed that the proposed strategy displayed an excellent selectivity against other non-target substances in human serum, a higher accuracy and a better stability when compared with the traditional enzyme-linked immunosorbent assay (ELISA) in detecting the same or mixed serum from 21 healthy subjects. Furthermore, the proposed electrochemical immunosensor successfully monitored the level of serum FN at various time points in five septic patients during the treatment. These findings demonstrate that the proposed strategy is highly sensitive and accurate in monitoring sepsis progress and has significant clinical improvements over the ELISA methodology, signifying a great potential of a commercial kit.

Dual-modality impedimetric immunosensor for early detection of prostate-specific antigen and myoglobin markers based on antibody-molecularly imprinted polymer

A new dual-modality immunosensor based on molecularly imprinted polymer (MIP) and a nanostructured biosensing layer has fabricated for the simultaneous detection of two important markers including prostate-specific antigen (PSA) and myoglobin (Myo) in human serum and urine samples. In the first step, 3,3'-dithiodipropionic acid di(N-hydroxysuccinimide ester) (DSP) was self-assembled on a gold screen printed electrode (SPE). Then, the target proteins were attached covalently to the DSP-SPE. The imprinted cocktail polymer ((MIP(PSA, Myo)-SPE)) was synthesized at the SPE surface using acrylamide as monomer, N,N'-methylenebisacrylamide as a crosslinker, and PSA and Myo as the templates, respectively. The MIP-SPE was specific for the impedimetric sensing of PSA and Myo. After that, a nanocomposite (NCP) was synthesized based on the decorated magnetite nanoparticles with multi-walled carbon nanotube, graphene oxide and specific antibody for PSA (Ab). Then, NCP incubated with (MIP(PSA, Myo)-SPE. The modified electrodes and synthesized nanoparticles were characterized using electrochemical impedance spectroscopy, dynamic light scattering, surface plasmon resonance and scanning electron microscopy. The limits of detections were found to be 5.4 pg mL^-1 and 0.83 ng mL^-1 with the linear dynamic ranges of 0.01-100 and 1-20000 ng mL^-1 for PSA and Myo, respectively. The ability of proposed biosensor to detect PSA and Myo simultaneously with high sensitivity and specificity offers a powerful opportunity for the new generation of biosensors. This dual-analyte specific receptors-based device is highly desired for the integration with lab-on-chip kits to measure a wide panel of biomarkers present at ultralow levels during early stages of diseases progress.

A signal-on nanobiosensor for VEGF165 detection based on supraparticle copper nanoclusters formed on bivalent aptamer

In this study, a signal-on nanobiosensor based on bivalent aptamer-Cu nanocluster was designed and optimized for specific and sensitive detection of VEGF₁₆₅. The VEGF₁₆₅ is known as a promising biomarker in different diseases such as cancer in the angiogenic stage. Detection and quantification of VEGF₁₆₅ is a crucial step in diagnosis and monitoring the treatment plan. The represented nanostructure consists of multimerized VEGF₁₆₅ aptamer joint with ssDNA based linker in the middle and poly thymine sequences on both 3' and 5' ends as a template for Cu-nanocluster supraparticle formation. This self-assembled structure leads to accurate controlling of aggregation in the presence of VEGF₁₆₅. This study is the first report for Cu nanocluster nucleation on ploy thymine tails of ssDNA which performed in two reduction steps to form stable CuNC supraparticle. The sensing strategy was designed based on the target-induced structure switching mode of the aptamer. In the presence of VEGF₁₆₅, due to self-assembly induced emission and aggregation-induced emission phenomena this nanostructure depicted the visible wavelength shift and enhancement in the fluorescence emission intensity. Also, the results of the analytical performance of this nanobiosensor indicated the LOD of 12 pM which revealed high rate sensitivity. This aptasensor exhibited stability and decent response linearity range (10-800 pM, R² = 0.9943). The selectivity and specificity assessment showed high discriminant capability in the real serum sample. In conclusion, this signal-on nanobiosensor provides a facile, sensitive and reliable assay for clinical monitoring of the VEGF₁₆₅ concentration in serum without further sample preparation.

Self-stacking of exfoliated charged nanosheets of LDHs and graphene as biosensor with real-time tracking of dopamine from live cells

This study introduces a new strategy for periodic stacking of positively charged NiAl layered double hydroxides (LDHs) nanosheets with negatively charged monolayers of graphene (G) by systematically optimizing several parameters in a controlled co-feeding fashion and resultant heterostacked NiAl LDH/G LBL nanocomposites have been practically applied in sensitive detection of dopamine released from live cells as early Parkinson's disease (PD) diagnostic tool. PD is the second most chronic neurodegenerative disorder with gradual progressive loss of movement and muscle control causing substantial disability and threatening the life seriously. Unfortunately majority of dopaminergic neurons present in substantia nigra of PD patients are destroyed before it is being clinically diagnosed, so early stages PD diagnosis is essential. Because of direct neighboring of extremely conductive graphene to semiconductive LDHs layers, enhanced intercalation capability of LDHs, and huge surface area with numerous active sites, good synergy effect is harvested in heteroassembled NiAl LDH/G LBL material, which in turn shows admirable electrocatalytic ability in DA detection. The interference induced by UA and AA is effectively eliminated especially after the modifying the electrode with Nafion. The outstanding electrochemical sensing performance of NiAl LDH/G LBL modified electrode has been achieved in terms of broad linear range and lowest real detection limit of 2 nM (S/N = 3) towards DA oxidation. Benefitting from superior efficiency, biosensor has been successfully used for real-time in-vitro tracking of DA efflux from live human nerve cell after being stimulated. We believe that our biosensing platform of structurally integrated well-ordered LBL heteroassembly by inserting graphene directly to the interlayer galleries of LDHs material will open up new avenue in diseases determination window.

Metallic Transition Metal Dichalcogenide Nanosheets as an Effective and Biocompatible Transducer for Electrochemical Detection of Pesticide

Owing to their large specific surface, favorable electrical conductivity, and excellent electrocatalytic capabilities, two-dimensional transition metal dichalcogenides have received considerable attention in the field of biosensors. On the basis of these properties, we developed a portable and disposable enzyme-based biosensor for paraoxon detection using a metallic MoS₂ nanosheets modified screen-printed electrode (SPE). The exfoliated ultrathin metallic MoS₂ nanosheets can accelerate the electron transfer on electrode surface and contribute to the immobilization of acetylcholinesterase (AChE) via the cross-linking of glutaraldehyde. Electrodeposited gold nanoparticles (AuNPs) on SPE were used to immobilize MoS₂ nanosheets through the interaction between Au atoms on AuNPs and S atoms on MoS₂. Using acetylcholine as the substrate, AChE can catalyze the formation of electroactive thiocholine and further generate the redox current. In the presence of paraoxon, the activity of AChE can be inhibited, making the related electrochemical signals weaken. Under the optimized conditions, this electrochemical biosensor exhibited a favorable linear relationship with the concentration of paraoxon from 1.0 to 1000 μg L^-1, with the detection limit of 0.013 μg L^-1. Furthermore, this developed biosensor was successfully applied to detect paraoxon in pretreated apple and pakchoi samples, which can provide a reliable method for the rapid analysis of organophosphorus pesticides in agricultural products.