Functionalized nitrogen doped graphene quantum dots and bimetallic Au/Ag core-shell decorated imprinted polymer for electrochemical sensing of anticancerous hydroxyurea

Development of a molecularly imprinted polymer-based electrochemical sensor with metal-organic frameworks for monitoring the antineoplastic drug vismodegib

A novel and robust electrochemical sensing tool for the determination of vismodegib (VIS), an anticancer drug, has been developed by integrating the selective recognition capabilities of molecularly imprinted polymer (MIP) and the sensitivity enhancement capability of metal-organic framework (MOF). Prior to this step, the electrochemical behavior of VIS was investigated using a bare glassy carbon electrode (GCE). It was observed that in 0.5 M H2SO4 solution as electrolyte, VIS has an oxidation peak around 1.3 V and the oxidation mechanism is diffusion controlled. The determination of VIS in a standard solution using a bare GCE showed a linear response in the concentration range from 2.5 μM to 100 μM, with a limit of detection (LOD) of 0.75 μM. Since sufficient sensitivity and selectivity could not be achieved with bare GCE, a MIP sensor was developed in the next step of the study. For this purpose, the GCE surface was first modified by drop casting with as-synthesized Co-MOF. Subsequently, a MIP network was synthesized via a thermal polymerization approach using 2-acrylamido-2-methylpropanesulfonic acid (AMPS) as monomer and VIS as template. MOFs are ideal electrode materials due to their controllable and diverse morphologies and modifiable surface properties. These characteristics enable the development of MIPs with more homogeneous binding sites and high affinity for target molecules. Integrating MOFs could help the performance of sensors with the desired stability and reproducibility. Electrochemical analysis revealed an observable enhancement of the output signal by the incorporation of MOF molecules, which is consistent with the sensitivity-enhancing role of MOF by providing more anchoring sites for the attachment of the polymer texture to the electrode surface. This MOF-MIP sensor exhibited impressive linear dynamic ranges ranging from 0.1 to 1.0 pM for VIS, with detection limits in the low picomolar range. In addition, the MOF-MIP sensor offers high accuracy, selectivity and precision for the determination of VIS, with no interference observed from complex media of serum samples. Additionally, in this study, Analytical GREEnness metric (AGREE), Analytical GREEnness preparation (AGREEprep) and Blue Applicability Grade Index (BAGI) were used to calculate the green profile score.

Electrochemistry as a Powerful Tool for Investigations of Antineoplastic Agents: A Comprehensive Review

Cancer is most frequently treated with antineoplastic agents (ANAs) that are hazardous to patients undergoing chemotherapy and the healthcare workers who handle ANAs in the course of their duties. All aspects related to hazardous oncological drugs illustrate that the monitoring of ANAs is essential to minimize the risks associated with these drugs. Among all analytical techniques used to test ANAs, electrochemistry holds an important position. This review, for the first time, comprehensively describes the progress done in electrochemistry of ANAs by means of a variety of bare or modified (bio)sensors over the last four decades (in the period of 1982-2021). Attention is paid not only to the development of electrochemical sensing protocols of ANAs in various biological, environmental, and pharmaceutical matrices but also to achievements of electrochemical techniques in the examination of the interactions of ANAs with deoxyribonucleic acid (DNA), carcinogenic cells, biomimetic membranes, peptides, and enzymes. Other aspects, including the enantiopurity studies, differentiation between single-stranded and double-stranded DNA without using any label or tag, studies on ANAs degradation, and their pharmacokinetics, by means of electrochemical techniques are also commented. Finally, concluding remarks that underline the existence of a significant niche for the basic electrochemical research that should be filled in the future are presented.

Gd-GQDs as nanotheranostic platform for the treatment of HPV-positive oropharyngeal cancer

In this study, we developed new gadolinium-graphene quantum dot nanoparticles (Gd-GQDs) as a theranostic platform for magnetic resonance imaging and improved the efficiency of radiotherapy in HPV-positive oropharyngeal cancer. Based on cell toxicity results, Gd-GQD NPs were nontoxic for both cancer and normal cell lines up to 25 µg/ml. These NPs enhance the cytotoxic effect of radiation only on cancer cells but not on normal cells. The flow cytometry analysis indicated that cell death mainly occurred in the late phase of apoptosis. The immunocytochemical analysis was used to evaluate apoptosis pathway proteins. The Bcl-2 and p53 protein levels did not differ statistically significantly between radiation alone group and those that received irradiation in combination with NPs. In contrast, the combination group exhibited a significant increase in Bax protein expression, suggesting that cells could undergo apoptosis independent of the p53 pathway. Magnetic resonance (MR) imaging showed that Gd-GQD NPs, when used at low concentrations, enhanced T1-weighted signal intensity resulting from T1 shortening effects. At higher concentrations, the T2 shortening effect became predominant and was able to decrease the signal intensity. Gd-GQD appears to offer a novel approach for enhancing the effectiveness of radiation treatment and facilitating MR imaging for monitoring HPV-positive tumors.

Three-Dimensional DNA Hydrogel Mediated Dual-Mode Sensing Method for Quantification of Epithelial Cell Adhesion Molecule in Biological Fluid Samples

Monitoring changes in the expression of marker proteins in biological fluids is essential for biomarker-based disease diagnosis. Epithelial cell adhesion molecule (EpCAM) has been identified as a broad-spectrum biomarker for various chronic diseases and as a therapeutic target. However, the development of simple and reliable methods for quantifying EpCAM changes in biological fluids faces challenges due to the variability of its expression across different diseases, the presence of soluble forms, and matrix effects. In this paper, a surface-enhanced Raman scattering (SERS)-fluorescence (FL) dual-mode sensing method was established for quantification of trace EpCAM in biological fluids based on bimetallic Au@Ag nanoparticles and nitrogen-doped quantum dots encapsulated DNA hydrogel hybrid with graphene oxide (Au@Ag-NQDs/GO). The DNA hydrogel was constructed based on three-dimensional (3D) structure DNA-mediated strategy using an aptamer DNA (AptDNA) linker. The interaction of the AptDNA with EpCAM triggered the disassembly of the DNA hydrogel. Consequently, the release of Au@Ag nanoparticles induced an "on-off" switch in the SERS signal while the weakened FL quenching effect in Au@Ag-NQDs/GO system achieved "off-on" switch of FL signal, enabling the simultaneous SERS-FL quantification of EpCAM. The established dual-mode method exhibited outstanding sensitivity and stability in quantifying EpCAM in the range of 0.5-60.0 pg/mL, with the limits of detection (LODs) of SERS and FL as 0.17 and 0.35 pg/mL, respectively. When applied for real sample analysis, the method showed satisfactory specificity and recoveries in cancer cells lysate, serum, and urine samples with RSDs of 2.8-6.3%, 4.0-6.3%, and 2.8-5.7%, respectively. The developed SERS-FL sensing method offered a sensitive, reliable, and practical quantification strategy for trace EpCAM in diverse biological fluid samples, which would benefit the early diagnosis of disease and further health management.

Fentogram electrochemical detection of HIV RNA based on graphene quantum dots and gold nanoparticles

This work reports the construction of an HIV-specific genosensor through the modification of carbon screen-printed electrodes (CSPE) with graphene quantum dots decorated with L-cysteine and gold nanoparticles (cys-GQDs/AuNps). Cys-GQDs were characterized by FT-IR and UV-vis spectra and electronic properties of the modified electrodes were evaluated by cyclic voltammetry and electrochemical impedance spectroscopy. The modification of the electrode surface with cys-GQDs and AuNps increased the electrochemical performance of the electrode, improving the electron transfer of the anionic redox probe [Fe(CN)6]3-/4- on the electrochemical platform. When compared to the bare surface, the modified electrode showed a 1.7 times increase in effective electrode area and a 29 times decrease in charge transfer resistance. The genosensor response was performed by differential pulse voltammetry, monitoring the current response of the anionic redox probe, confirmed with real genomic RNA samples, making it possible to detect 1 fg/mL. In addition, the genosensor maintained its response for 60 days at room temperature. This new genosensor platform for early detection of HIV, based on the modification of the electrode surface with cys-GQDs and AuNps, discriminates between HIV-negative and positive samples, showing a low detection limit, as well as good specificity and stability, which are relevant properties for commercial application of biosensors.

Exploring the potential of molecularly imprinted polymers and metal/metal oxide nanoparticles in sensors: recent advancements and prospects

Metal/metal oxide nanoparticles have gained increasing attention in recent years due to their outstanding features, including optical and catalytic properties, as well as their excellent conductivity. The implementation of metal/metal oxide nanoparticles, combined with molecularly imprinted polymers (MIPs) has paved the way for a new generation of building blocks to engineer and enhance the fascinating features of advanced sensors. This review critically evaluates the impact of combining metal/metal oxide nanoparticles with MIPs in sensors. It covers synthesis strategies, advantages of coupling these materials with MIPs, and addresses questions about the selectivity of these hybrid materials. In the end, the current challenges and future perspectives of this field are discussed, with a particular focus on the potential applications of these hybrid composites in the sensor field. This review highlights the exciting opportunities of using metal/metal oxide nanoparticles along with MIPs for the development of next-generation sensors.

Molecularly imprinted electrochemical sensor based on synergistic interaction of honeycomb-like Ni-MOF decorated with AgNPs and N-GQDs for ultra-sensitive detection of olaquindox in animal-origin food

Olaquindox (OLA) in food from its illegal use possesses great harmful effects on humans, making it important to develop sensitive, inexpensive, and convenient methods for OLA detection. This study innovatively presented a molecularly imprinted electrochemical sensor based on the synergistic effects of nitrogen-doped graphene quantum dots (N-GQDs) and a nickel-based metal-organic framework functionalized with silver nanoparticles (Ag/Ni-MOF) for OLA detection. N-GQDs and Ag/Ni-MOF with unique honeycomb structures were sequentially modified on the glassy carbon electrode (GCE) surface to accelerate the electron transfer rate and increase the available region of the electrode. Molecularly imprinted polymers were further grown on the Ag/Ni-MOF/N-GQDs/GCE by electropolymerization to significantly enhance the selective recognition of OLA. The constructed sensor showed excellent performance for selective OLA determination, with a wide linear range (5-600 nmol·L^-1) and exceedingly low detection limit (2.2 nmol·L^-1). The sensor was successfully applied to detect OLA in animal-origin food with satisfactory recoveries (96.22-101.02%).

Construction of a novel nano-enzyme for ultrasensitive glucose detection with surface-enhanced Raman scattering

Fabricating more sensitive, stable and low-cost nanomaterials for the detection of glucose is important for the disease diagnosis and monitoring. Herein, we established a nanocomposite (polypyrrole bridging GO@Au@MnO₂) as a novel surface-enhanced Raman scattering (SERS) nanoprobe for the quantitative detection of glucose in trace serum. Each component in the nanocomposites played an irreplaceable role in SERS detection of glucose. Polypyrrole (PPy) could act as Raman signal and extra SERS signal molecules didn't need to be introduced; Graphene oxide (GO) and gold nanoparticles (Au NPs) could enhance Raman signal of PPy; Au NPs also acted as glucose oxidase, which can oxidize glucose to produce gluconic acid and hydrogen peroxide(H₂O₂); Manganese oxide (MnO₂) further enhanced Raman signal of PPy and responded to hydrogen peroxide, which will induce the decrease of Raman intensity of PPy. Thus, glucose can be quantified according to Raman signal output of PPy, which displayed a liner range from 1 to 10 μM, with detectable limit of 0.114 μM. Because of the merits in sensitivity, convenience and versatility, the novel method shows large potential space for disease-related substance detection in the future.

Carbon-based biosensors from graphene family to carbon dots: A viewpoint in cancer detection

According to the latest report by International Agency for Research on Cancer, 19.3 million new cancer cases and 10 million cancer deaths were globally reported in 2020. Early diagnosis can reduce these numbers significantly, and biosensors have appeared to be a solution to this problem as, unlike the traditional methods, they have low cost, rapid process, and do not need experts present on site for use. These devices have been incorporated to detect many cancer biomarkers and measure cancer drug delivery. To design these biosensors, a researcher must know about their different types, properties of nanomaterials, and cancer biomarkers. Among all types of biosensors, electrochemical and optical biosensors are the most sensitive and promising sensors for detecting complicated diseases like cancer. The carbon-based nanomaterial family has attracted lots of attention due to their low cost, easy preparation, biocompatibility, and significant electrochemical and optical properties. In this review, we have discussed the application of graphene and its derivatives, carbon nanotubes (CNTs), carbon dots (CDs), and fullerene (C60), for designing different electrochemical and optical cancer-detecting biosensors. Furthermore, the application of these carbon-based biosensors for detecting seven widely studied cancer biomarkers (HER2, CEA, CA125, VEGF, PSA, Alpha-fetoprotein, and miRNA21) is reviewed. Finally, various fabricated carbon-based biosensors for detecting cancer biomarkers and anticancer drugs are comprehensively summarized as well.

Eco-Friendly and Sustainable Pathways to Photoluminescent Carbon Quantum Dots (CQDs)

Carbon quantum dots (CQDs), a new family of photoluminescent 0D NPs, have recently received a lot of attention. They have enormous future potential due to their unique properties, which include low toxicity, high conductivity, and biocompatibility and accordingly can be used as a feasible replacement for conventional materials deployed in various optoelectronic, biomedical, and energy applications. The most recent trends and advancements in the synthesizing and setup of photoluminescent CQDs using environmentally friendly methods are thoroughly discussed in this review. The eco-friendly synthetic processes are emphasized, with a focus on biomass-derived precursors. Modification possibilities for creating newer physicochemical properties among different CQDs are also presented, along with a brief conceptual overview. The extensive amount of writings on them found in the literature explains their exceptional competence in a variety of fields, making these nanomaterials promising alternatives for real-world applications. Furthermore, the benefits, drawbacks, and opportunities for CQDs are discussed, with an emphasis on their future prospects in this emerging research field.

Effects of morphology and size of nanoscale drug carriers on cellular uptake and internalization process: a review

In the field of targeted drug delivery, the effects of size and morphology of drug nanocarriers are of great importance and need to be discussed in depth. To be concise, among all the various shapes of nanocarriers, rods and tubes with a narrow cross-section are the most preferred shapes for the penetration of a cell membrane. In this regard, several studies have focused on methods to produce nanorods and nanotubes with controlled optimized size and aspect ratio (AR). Additionally, a non-spherical orientation could affect the cellular uptake process while a tangent angle of less than 45° is better at penetrating the membrane, and Ω = 90° is beneficial. Moreover, these nanocarriers show different behaviors when confronting diverse cells whose fields should be investigated in future studies. In this survey, a comprehensive classification based on carrier shape is first submitted. Then, the most commonly used methods for control over the size and shape of the carriers are reviewed. Finally, influential factors on the cellular uptake and internalization processes and related analytical methods for evaluating this process are discussed.

A robust electrochemical sensing platform for the detection of erlotinib based on nitrogen-doped graphene quantum dots/copper nanoparticles-polyaniline-graphene oxide nanohybrid

Erlotinib is a potent and highly specific tyrosine kinase inhibitor with the hindering effects on the growth of cancer cells. An electrochemical sensor with the great sensitivity and selectivity was fabricated for determining erlotinib by using a graphite rod electrode modified by the nitrogen-doped graphene quantum dots (N-GQDs) and a ternary nanohybrid comprising copper nanoparticles, polyaniline, along with graphene oxide (N-GQDs/CuNPs-PANI@GO) for the first time. The establishment of PANI and CuNPs was done simultaneously on the GO surface by thein situoxidative polymerization method. The morphological characteristics and elemental structure of the synthesized nanoparticles were examined by some microscopy techniques and x-ray energy/diffraction methods. The fabricated sensor represented the electrocatalytic activity towards erlotinib with a linear detection range from 1.0 nM to 35.0μM, a detection limit of 0.712 nM, and a sensitivity of 1.3604μAμM^-1. Moreover, the N-GQDs/CuNPs-PANI@GO sensor showed acceptable stability up to 30 d (94.82%), reproducibility (RSD values of 3.19% intraday and 3.52% interday), and repeatability (RSD value of 3.65%) as a novel and powerful electrochemical sensor. It was successfully applied to monitor erlotinib in the drug-injected aqueous solution, serum, and urine samples that proved the capability of the sensor for the erlotinib monitoring in the biological samples.

Dual signal light detection of beta-lactoglobulin based on a porous silicon bragg mirror

In this work, a new dual signal light detection method based on porous silicon Bragg mirror (PSBM) and biological labelling with quantum dots (QDs) is proposed for the detection of beta-lactoglobulin (β-lg). The first signal light is a probe light emitted by a laser with wavelength of 633 nm, which enters the PSBM and is reflected from the surface. The wavelength of the probe light is located at the edge of the PSBM band gap, where it has the lowest reflectivity. β-lg antibodies is labelled with CdSe/ZnS QDs and reacts with β-lg molecules have been fixed to the inner wall of the porous silicon pores. Due to the specific binding of biomolecules in PSBM, the refractive index of the device increases, resulting in the enhancement of detection reflected light. The QDs play the role of refractive index amplification. The second signal light is the fluorescence of QDs in immune reactants. QDs produce fluorescence at 630 nm when excited by a short-wavelength laser. The fluorescence signal is further enhanced by PSBM. The superimposed images of two kinds of light on the surface of PSBM are obtained by digital microscope at the same time. By calculating the average grey value change of the image before and after biological reaction, β-lg can be detected with high sensitivity. The detection limit of β-lg was 0.12 ng/mL. The experimental results showed that the PSBM-based dual signal light method could be used to detect the content of cow milk adulterated in β-lg free camel milk.

Novel dual-template molecular imprinted electrochemical sensor for simultaneous detection of CA and TPH based on peanut twin-like NiFe2O4/CoFe2O4/NCDs nanospheres: Fabrication, application and DFT theoretical study

Hollow peanut-shaped NiFe₂O₄/CoFe₂O₄ twinned nano-spherical shell composite materials have interconnected electron channels and excellent electrochemical performance, which prompted the use of this unique spatial structure to fabricate efficient electrochemical sensors. In this work, N-doped carbon dots (NCDs) incorporated into magnetic NiFe₂O₄/CoFe₂O₄ nanoparticle shell (NiFe₂O₄/CoFe₂O₄/NCDs) modified glassy carbon electrode (GCE) was applied to construct a dual-template molecularly imprinted polymer (MIP) based electrochemistry sensor (NiFe₂O₄/CoFe₂O₄/NCDs/MIP/GCE) for the simultaneous detection of catechin (CA) and theophylline (TPH). MIP was fabricated by an in-situ electrochemical polymerization strategy based on the theoretical exploration and density functional theory (DFT) computer directional simulation to screen out the optimal functional monomer (L-arginine) and the optimal ratio between the dual template molecules (CA and TPH) and functional monomer. The materials were characterized by SEM, TEM, XRD, XPS, and TGA. Besides, electron binding energy, binding constant, and imprinting factor were investigated. With the optimal conditions, the proposed electrochemical dual detection system showed outstanding analytical performance for the simultaneous sensing of CA and TPH, with an ultralow detection limit (LOD, S/N = 3) of 1.3 nM for CA in 0.01-1 μM (R² = 0.9956) and 1-50 μM (R² = 0.9928), as well as a LOD of 20.0 nM for TPH in the linear range of 0.1-100 μM (R² = 0.9939), respectively. Also, the selectivity and anti-interference performances of the fabricated sensor were performed by differential pulse voltammetry and chronoamperometry, and successfully detected the analyte from tea drinks and human urine samples with the recovery rates ranging from 98.22% to 104.76% and relative standard deviations (RSD) were 1.19%-3.81%, demonstrated the sensor has excellent stability, repeatability, and reproducibility, which paves the way for other platforms to use this nanomaterial for the detection of antioxidant in the filed food safety.

Determination of chloropropanol with an imprinted electrochemical sensor based on multi-walled carbon nanotubes/metal-organic framework composites

In this paper, a composite composed of carboxylated multi-wall carbon nanotubes (cMWCNT) incorporated in a metal–organic framework (MOF-199) has been synthesized using 1,3,5-benzoic acid as a ligand through a simple solvothermal method. The synthesized cMWCNT/MOF-199 composite was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffractometry (XRD). The cMWCNT/MOF-199 hybrids were modified on the surface of glassy carbon electrodes (GCE) to prepare a molecularly imprinted electrochemical sensor (MIECS) for specific recognition of 3-chloro-1,2-propanediol (3-MCPD). The electrodes were characterized by differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Under optimal conditions, the electrochemical sensor exhibited an excellent sensitivity and high selectivity with a good linear response range from 1.0 × 10⁻⁹ to 1.0 × 10⁻⁵ mol L⁻¹ and an estimated detection limit of 4.3 × 10⁻¹⁰ mol L⁻¹. Furthermore, this method has been successfully applied to the detection of 3-MCPD in soy sauce, and the recovery ranged from 96% to 108%, with RSD lower than 5.5% (n = 3), showing great potential for the selective analysis of 3-MCPD in foodstuffs.

In this study, cMWCNT/MOF-199 composites were used as the modified electrodes, and a MIECS having specific recognition of 3-MCPD was prepared by electrochemical polymerization for selective analysis of 3-MCPD in foodstuffs.

Doped-carbon dots: Recent advances in their biosensing, bioimaging and therapy applications

As a fascinating class of fluorescent carbon dots (CDs), doped-CDs are now sparked intense research interest, particularly in the diverse fields of biomedical applications due to their unique advantages, including low toxicity, physicochemical, photostability, excellent biocompatibility, and so on. In this review, we have summarized the most recent developments in the literature regarding the employment of doped-CDs for pharmaceutical and medical applications, which are published over approximately the past five years. Accordingly, we discuss the toxicity and optical properties of these nanomaterials. Beyond the presentation of successful examples of the application of these multifunctional nanoparticles in photothermal therapy, photodynamic therapy, and antibacterial activity, we further highlight their application in the cellular labeling, dual imaging, and in vitro and in vivo bioimaging by use of fluorescent-, photoacoustic-, magnetic-, and computed tomography (CT)-imaging. The potency of doped-CDs was also described in the biosensing of ions, small molecules, and drugs in biological samples or inside the cells. Finally, the advantages, disadvantages, and common limitations of doped-CD technologies are reviewed, along with the future prospects in biomedical research. Therefore, this review provides a concise insight into the current developments and challenges in the field of doped-CDs, especially for biological and biomedical researchers.

Single-Atom Gadolinium Anchored on Graphene Quantum Dots as a Magnetic Resonance Signal Amplifier

A single-atom metal doped on carbonaceous nanomaterials has attracted increasing attention due to its potential applications as high-performance catalysts. However, few studies focus on the applications of such nanomaterials as nanotheranostics for simultaneous bioimaging and cancer therapy. Herein, it is pioneeringly demonstrated that the single-atom Gd anchored onto graphene quantum dots (SAGd-GQDs), with dendrite-like morphology, was successfully prepared. More importantly, the as-fabricated SAGd-GQDs exhibits a robustly enhanced longitudinal relaxivity (r₁ = 86.08 mM^-1 s^-1) at a low Gd³⁺ concentration of 2 μmol kg^-1, which is 25 times higher than the commercial Gd-DTPA (r₁ = 3.44 mM^-1 s^-1). In vitro and in vivo studies suggest that the obtained SAGd-GQDs is a highly potent and contrast agent to obtain high-definition MRI, thereby opening up more opportunities for future precise clinical theranostics.

Electrochemical Determination of Hydroxyurea in a Complex Biological Matrix Using MoS2-Modified Electrodes and Chemometrics

Hydroxyurea, an oral medication with important clinical benefits in the treatment of sickle cell anemia, can be accurately determined in plasma with a transition metal dichalcogenide-based electrochemical sensor. We used a two-dimensional molybdenum sulfide material (MoS₂) selectively electrodeposited on a polycrystalline gold electrode via tailored waveform polarization in the gold electrical double layer formation region. The electro-activity of the modified electrode depends on the electrical waveform parameters used to electro-deposit MoS₂. The concomitant oxidation of the MoS₂ material during its electrodeposition allows for the tuning of the sensor’s specificity. Chemometrics, utilizing mathematical procedures such as principal component analysis and multivariable partial least square regression, were used to process the electrochemical data generated at the bare and the modified electrodes, thus allowing the hydroxyurea concentrations to be predicted in human plasma. A limit-of-detection of 22 nM and a sensitivity of 37 nA cm⁻² µM⁻¹ were found to be suitable for pharmaceutical and clinical applications.

Smart materials for point-of-care testing: From sample extraction to analyte sensing and readout signal generator

The last decade has seen a surge of technical developments in the field on point-of-care testing (POCT). While these developments are extremely diverse, the common aim is to implement improved methods for quick, reliable and inexpensive diagnosis of patients within the clinical setting. While examples of successful introduction and use of POCT techniques are growing, further developments are still necessary to create POCT devices with better portability, usability and performance. Advances in smart materials emerge as potentially valuable know-hows to provide a competitive edge to the development of next generation POCT devices. This review describes the key advantages of adopting smart material-based technologies at different analytical stages of a POCT platform. Under these analytical stages which involves sample pre-treatment, analyte sensing and readout signal generator, several concepts and approaches from contemporary research work in using smart material-based technologies will be the major focus in this review. Lastly, challenges and potential outlook in implementing materials technologies from the application point of view for POCT will be discussed.

Carbonaceous Nanomaterials Employed in the Development of Electrochemical Sensors Based on Screen-Printing Technique—A Review

This paper aims to revise research on carbonaceous nanomaterials used in developing sensors. In general, nanomaterials are known to be useful in developing high-performance sensors due to their unique physical and chemical properties. Thus, descriptions were made for various structural features, properties, and manner of functionalization of carbon-based nanomaterials used in electrochemical sensors. Of the commonly used technologies in manufacturing electrochemical sensors, the screen-printing technique was described, highlighting the advantages of this type of device. In addition, an analysis was performed in point of the various applications of carbon-based nanomaterial sensors to detect analytes of interest in different sample types.

Fluorescent Carbon Quantum Dots-Synthesis,Functionalization and Sensing Application in FoodAnalysis

Carbon quantum dots (CQDs) with stable physicochemical properties are one of theemerging carbon nanomaterials that have been studied in recent years. In addition to the excellentoptical properties such as photoluminescence, photobleaching resistance and light stability, thismaterial also has favorable advantages of good biocompatibility and easy functionalization, whichmake it an ideal raw material for constructing sensing equipment. In addition, CQDs can combinedwith other kinds of materials to form the nanostructured composites with unique properties, whichprovides new insights and ideas for the research of many fields. In the field of food analysis,emerging CQDs have been deeply studied in food composition analysis, detection and monitoringtrace harmful substances and made remarkable research progress. This article introduces andcompares the various methods for CQDs preparation and reviews its related sensing applicationsas a new material in food components analysis and food safety inspection in recent years. It isexpected to provide a significant guidance for the further study of CQDs in the field of foodanalysis and detection. CQDs; synthesis; fluorescent sensing; food analysis.

Noble Metals Based Bimetallic and Trimetallic Nanoparticles: Controlled Synthesis, Antimicrobial and Anticancer Applications

Noble bimetallic and trimetallic nanoparticles (NBT-NPs) have superior biomedical applications as compared to their monometallic counterparts. The performance of these nanomaterials depends on their composition, shape and size. Hence, the controlled-synthesis of these nanomaterials is a hot area of research. Till date, no review article in the literature accounts regarding the controlled-synthesis and biomedical applications related to morphology, optimum composition, biocompatibility and versatile chemistry of NBT-NPs. Taking this into contemplation, an effort was made to provide a clear insight into the morphology-controlled synthesis and size/shape-dependent anticancer and bactericidal applications of NBT-NPs. Chemical reduction method for the controlled-synthesis of NBT-NPs is reviewed critically. Furthermore, the potential role of various reaction parameters such as time, reducing agents, stabilizing/capping agents, nature/concentration of precursors, temperature and pH in the shape/size-controlled synthesis of these nanomaterials are discussed. In the second part of this article, anticancer and bactericidal applications of the NBT-NPs are reviewed and the influences of optimum composition, size, surface structure, versatile chemistry and synergism are studied. Finally, the current challenges in the controlled-synthesis and biomedical applications of these nanomaterials, and prospects to resolve related issues are discussed. HighlightsChemical reduction method for the synthesis of NBT-NPs is reviewed.The influences of parameters on the control synthesis of NBT-NPs are discussed.Antibacterial and anticancer applications and cytotoxicity of NBT-NPs are reviewed.Possible solutions for the key challenges are discussed.Outlooks about the synthesis and biomedical applications of NBT-NPs are discussed.

Electrochemistry in Carbon-based Quantum Dots

Electrochemistry belongs to an important branch of chemistry that deals with the chemical changes produced by electricity and the production of electricity by chemical changes. Therefore, it can not only act a powerful tool for materials synthesis, but also offer an effective platform for sensing and catalysis. As extraordinary zero-dimensional materials, carbon-based quantum dots (CQDs) have been attracting tremendous attention due to their excellent properties such as good chemical stability, environmental friendliness, nontoxicity and abundant resources. Compared with the traditional methods for the preparation of CQDs, electrochemical (EC) methods offer advantages of simple instrumentation, mild reaction conditions, low cost and mass production. In return, CQDs could provide cost-effective, environmentally friendly, biocompatible, stable and easily-functionalizable probes, modifiers and catalysts for EC sensing. However, no specific review has been presented to systematically summarize both aspects until now. In this review, the EC preparation methods of CQDs are critically discussed focusing on CQDs. We further emphasize the applications of CQDs in EC sensors, electrocatalysis, biofuel cells and EC flexible devices. This review will further the experimental and theoretical understanding of the challenges and future prospective in this field, open new directions on exploring new advanced CQDs in EC to meet the high demands in diverse applications.

Purification and separation of ultra-small metal nanoclusters

Metal nanoclusters (NCs) are ultra-small nanoparticles intermediate in size between small molecule complexes and nanoparticles. NCs with tunable surface functionality feature unique physical and chemical properties, however these properties are frequently compromised by the presence of undesired components such as excess ligands or mixtures of NCs. In a typical synthesis process, different NCs can be formed with varying numbers of metal atoms and/or ligands, and even NCs with the same number of metal atoms and ligands can have different spatial structures. The separation of pure NCs is important because different species have distinct optical and catalytic behavior. However, NCs can be difficult to purify or separate for a range of reasons. In this review, we discuss established and emerging approaches for NC purification/separation, with a focus on choosing the appropriate method depending on NC and application.

Dual enzyme-like properties of silver nanoparticles decorated Ag2WO4 nanorods and its application for H2O2 and glucose sensing

The facile one-pot hydrothermal synthesis of silver nanoparticles decorated silver tungstate nanorods (Ag@Ag₂WO₄ NRs) and their catalytic activities similar to those of natural enzymes catalase and peroxidase were reported. The Ag@Ag₂WO₄ NRs could catalyze the decomposition reaction of H₂O₂ into water and oxygen besides catalyzing the reduction of H₂O₂ into water in the presence of peroxidase substrates. Spectrophotometric and electrochemical methods were used to investigate the pH-dependent dual enzyme mimics exhibited by Ag@Ag₂WO₄ NRs. The Ag@Ag₂WO₄ NRs showed a lower Km value when compared to the natural horseradish peroxidase enzyme showing the stronger affinity for hydrogen peroxide and TMB. The peroxidase-like property of the synthesized Ag@Ag₂WO₄ NRs was exploited to develop a H₂O₂ sensor with a broad linear range and low detection limit. Thus, a wide linear range of 45.4 μM- 2.38 mM and a low detection limit of 5.4 μM was obtained by spectrophotometry while a wide linear range of 62.34 μM- 2.4 mM and a low detection limit of 6.25 μM was obtained by amperometry for H₂O₂. Further, the detection method was extended for the detection of glucose with a wide linear range of 27.7 μM- 0.33 mM and a low detection limit of 2.6 μM.

Amperometric sensing of catechol by using a nanocomposite prepared from Ag/Ag2O nanoparticles and N,S-doped carbon quantum dots

This work describes the synthesis of a nanocomposite consisting of Ag₂O, silver nanoparticles and N,S-doped carbon quantum dots (Ag₂O/Ag@NS-CQD). The NS-CQD were prepared by hydrothermal treatment of p-aminobenzenesulfonic acid. They act as both the reducing and stabilizing agent for synthesis of Ag₂O/Ag@NS-CQD. The composite was characterized by UV-vis spectroscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The glassy carbon electrode (GCE) was modified by coating it with Ag₂O/Ag@NS-CQD. It exhibits excellent amperometric response to catechol, typically at a low working potential of around 0.25 V. Under the best experimental conditions, the sensor has a wide linear response (0.2 to 180 μM) and a low detection limit (13 nM; at S/N = 3). The method was applied to analysis of spiked water samples and gave satisfactory results. Graphical abstract Schematic representation of the preparation of the Ag/Ag2O@N,S-doped carbon quantum dots composite using p-aminobenzenesulfonic acid and silver nitrate as the starting materials. The corresponding modified glassy carbon electrode exhibits the excellent amperometric sensing performance toward catechol at pH 7.0 with low detection limit and good selectivity.