Enhanced molecular imprinted electrochemical sensing of histamine based on signal reporting nanohybrid

Non-enzymatic electrochemical sensors for point-of-care testing: Current status, challenges, and future prospects

Current electrochemical sensors in point-of-care (POC) testing devices rely mainly on enzyme-based sensors owing to superior sensitivity and selectivity. Nevertheless, the poor stability, high reagent cost, complex fabrication methods and requirement of specific operational conditions make their adaptability in real-world applications unfavorable. Non-enzymatic electrochemical sensors are thus developed as they are more robust and cost-effective strategies. The advancement in material science and nanotechnology enables the development of novel non-enzymatic electrodes with favorable analytical performance. However, the developments are yet far from being adopted as viable products. This review therefore aims to gain insight into the field and evaluate the current progress and challenges to eventually propose future research directions. Here, fabrication strategies based on traditional and emerging technology are discussed in the light of analytical performance and cost-effectiveness. Moreover, the discussion is given on the pros and cons of non-enzymatic sensors when they are employed with various kinds of sample matrices, i.e., clinical and non-clinical samples, which must be taken into consideration for sensor development. Furthermore, molecular imprinting technology in tackling the selectivity issue is introduced and current progress is provided. Finally, the promising strategies from literature for solving the remaining challenges are included which could facilitate further development of robust POC testing devices based non-enzymatic sensors. We believe that once researchers and technology developers have reached the point where most problems are solved, the non-enzymatic sensors are going to be the robust choice for POC testing in clinical diagnostic, ensuring food safety, monitoring contaminants in environment, and bioprocess control.

Research advances in the diagnosis of infectious disease by aptasensor technology

Infectious diseases remain a major challenge to public health. The accurate and timely detection of pathogens responsible for these diseases is essential for controlling their spread, supporting clinical diagnosis, and enabling the application of appropriate therapies. Traditionally, the antibody-based assay has been the primary method for pathogen detection. However, recent advancements in aptamer-based technologies have initiated a transformative shift in diagnostic approaches. Aptamer-based sensors (aptasensors) are characterized by lower production costs and greater flexibility, making them compatible with various detection techniques. This broad applicability facilitates multifaceted, high-throughput applications, significantly improving the capacity to monitor and detect infectious diseases. In this review, we introduce the pathogenic mechanisms and characteristics of pathogens, provide an overview of recent advancements in the development of aptasensors for pathogen detection and highlight their versatility in identifying various infectious disease pathogens, including viruses, bacteria, parasites and other microorganisms. We systematically categorize aptasensors according to their detection mechanisms, including colorimetry, fluorescence, chemiluminescence, surface-enhanced Raman spectroscopy (SERS), surface plasmon resonance (SPR), electrochemistry and incorporation of field-effect transistors (FETs). We further demonstrate how these platforms leverage pathogen-specific biological features to achieve ultrasensitive and rapid diagnostics. Further optimization and validation of aptasensor platforms are anticipated to accelerate their clinical translation and industrialization. Advancing these innovative technologies will be crucial to meeting the growing demand for rapid, accurate and reliable pathogen detection across diverse clinical and environmental conditions, ultimately strengthening the ability to respond effectively to infectious disease threats.

Molecular imprinting technology for electrochemical sensing of kasugamycin in food products based on Cu2+/Cu+ stripping current

An electrochemical sensing approach was developed for the detection of the agricultural antibiotic drug kasugamycin. The method involves the construction of an electrochemical sensor comprising molecularly imprinted polymers (MIPs) embedded within a carbon paste (CP) matrix. The MIPs are designed to have imprinted sites that match the size and geometry of the Cu(II)-kasugamycin coordinated complex. Upon removal of kasugamycin, cavities suitable for the drug's entrance are formed within the MIPs. The presence of Cu(II) facilitates the detection of the drug by generating a redox signal of Cu(II)-Cu(I), which can be easily detected using differential pulse voltammetry (DPV). The signal response of Cu(II)-Cu(I) increases in the presence of the drug, promoting the accumulation of Cu(II) ions within the imprinted cavities. Under optimized conditions, the anodic peak (Ipa) signal of Cu(II)-Cu(I) exhibits an increase proportional to the concentration of kasugamycin within the range of 0.15-140 μM. The detection limit (LOD, S/N = 3) achieved is 0.046 μM. The proposed sensor demonstrates several characteristic features including good stability, reliable performance, a low detection limit, and excellent selectivity. The Cu(II)-MIP@CP sensor proved effective in detecting kasugamycin within complex samples like meat, milk, and cucumber, yielding recovery% ranging from 96.0 to 103.8%. Additionally, the relative standard deviation % (RSD%) fell within the range of 2.2% to 4.0%, indicating good precision and reliability.

Enhanced fluorometric detection of histamine using red emissive amino acid-functionalized bimetallic nanoclusters

Lysine-capped gold nanoclusters doped with silver (LYS@Ag/Au NCs) have been developed for the sensitive and selective "turn-off" fluorescence detection of histamine. This fluorescent probe demonstrates excellent stability and a high quantum yield of 9.45%. Upon addition of histamine, a positively charged biogenic amine, to the LYS@Ag/Au NCs fluorescent probe, its fluorescence emission is quenched due to electrostatic interaction, aggregation, and hydrogen bond formation. The probe exhibits good sensitivity for the determination of histamine within the range of 0.003-350 μM, with a detection limit of 0.001 μM based on a signal-to-noise ratio of 3. Furthermore, the probe has been applied to detect biogenic amines in complicated matrices, highlighting its potential for practical applications. However, interference from the analogue histidine was observed during analysis, which can be mitigated by using a Supelclean™ LC-SAX solid-phase extraction column for removal.

Optical dِِِِiscrimination of histamine and ethylenediamine in meat samples using a colorimetric affordable test strip (CATS): introducing a novel lab-on paper sensing strategy for low-cost ensuring food safety by rapid and accurate monitoring of biogenic amines

Biogenic amines (BAs) are a group of organic compounds that are produced through the decarboxylation of amino acids by microorganisms. These compounds are commonly found in a variety of foods and are known to cause adverse health effects if consumed in high concentrations. Therefore, the development of sensitive and rapid detection methods for detection and determination of BAs is essential for ensuring food safety. In this study, a novel colorimetric affordable test strip (CATS) was developed for the colorimetric and naked-eye detection of two BAs of ethylenediamine (EDA) and histamine (HIS) in meat samples. Also, triangular silver nanoparticles (AgNPrs) were used as a diagnostic optical probe, and CATS used as a simple, environmentally friendly, inexpensive diagnostic substrate for on-site recognition of meat spoil. The AgNPrs-based optosensor demonstrated high sensitivity and selectivity towards EDA and HIS, allowing for the detection of low concentrations of the BAs in real food samples such as raw chicken and beef. The system presented a UV-vis technique for HIS and EDA analysis in the linear range of 0.1 μM to 0.01 mM, with an LLOQ of 0.1 μM, and 0.05 to 1 μM, with an LLOQ of 0.05 μM, respectively. Additionally, the performance of the designed CATS in the analysis of produced gases was evaluated, highlighting the potential of this simple and cost-effective strategy for the development of BAs diagnostic kits. This approach provides a simple and cost-effective method for detecting BAs in food, which could be beneficial for ensuring food safety and preventing the harmful effects associated with their consumption.

Electronic Tongue Based on ZnO/ITO@glass for Electrochemical Monitoring of Spiciness Levels

Capsaicin, a chemical compound present in chili peppers, is widely acknowledged as the main contributor to the spicy and hot sensations encountered during consumption. Elevated levels of capsaicin can result in meals being excessively spicy, potentially leading to health issues, such as skin burning, irritation, increased heart rate and circulation, and discomfort in the gastrointestinal system and even inducing nausea or diarrhea. The level of spiciness that individuals can tolerate may vary, so what may be considered incredibly hot for one person could be mild for another. To ensure food safety, human healthcare, regulatory compliance, and quality control in spicy food products, capsaicin levels must be measured. For these purposes, a reliable and stable sensor is required to quantify the capsaicin level. To leverage the effect of zinc oxide (ZnO), herein, we demonstrated the one-step fabrication process of an electronic tongue (E-Tongue) based on an electrochemical biosensor for the determination of capsaicin. ZnO was electrodeposited on the indium tin oxide (ITO) surface. The biosensor demonstrated the two notable linear ranges from 0.01 to 50 μM and from 50 to 500 μM with a limit of detection (LOD) of 2.1 nM. The present study also included the analysis of real samples, such as green chilis, red chili powder, and dried red chilis, to evaluate their spiciness levels. Furthermore, the E-Tongue exhibited notable degrees of sensitivity, selectivity, and long-term stability for a duration of more than a month. The development of an E-Tongue for capsaicin real-time monitoring as a point-of-care (POC) device has the potential to impact various industries and improve safety, product quality, and healthcare outcomes.

Methylene blue-assisted molecularly-imprinted film modified nitrogen and sulfur co-doped molybdenum carbide for simultaneous electrochemical determination of two hepatotoxic drugs

A novel electrochemical sensor with a dual-template molecular imprinting technology was fabricated for the simultaneous detection of paracetamol (PAR) and isoniazid (INZ). The sensor was constructed using nitrogen and sulfur co-doped molybdenum carbide (N, S@Mo2C) and a thin layer of electro-polymerized methylene blue was applied onto the surface of the N, S@Mo2C. The electrochemical sensor demonstrated remarkable analytical efficiency for the concurrent PAR and INZ quantification under optimal circumstances. The system achieved an exceptionally low limit of detection (S/N = 3) of  3.7 nM for PAR, with a concentration range  of  0.013 and 140 µM.  A LOD of 7.6 nM was attained for INZ, with a linear range  between 0.025 and 140 µM. Furthermore, the platform's selectivity was evaluated using differential pulse voltammetry  (DPV). The designed platform successfully detected PAR and INZ in authentic samples with recoveries varying between 98.3% and 104.9%. The relative standard deviations (RSD) for these measurements ranged from 2.7 to 4.0%, demonstrating that the proposed sensor is extremely stable, repeatable, and reproducible. These promising results suggest that the sensor holds potential for the detection of various (bio) molecules, paving the way for future applications in sensing fields.

Inspecting Histamine Isolated from Fish through a Highly Selective Molecularly Imprinted Electrochemical Sensor Approach

Numerous analytical approaches have been developed to determine histamine levels in food samples due to its health consequences. Consuming histamine over the Food and Drug Administration (FDA)-regulated 50 mg kg^-1 limit would result in chronic toxicity. Consequently, the present study discusses a novel electrochemical approach to evaluate histamine levels in fish products via a molecularly imprinted polymer (MIP) on an electrode surface. The film was produced with electropolymerized polyurethane (PU), which maintained the histamine compound. Fourier-transform infrared (FTIR) spectroscopy was applied to verify the MIP manufactured in this study. The capability of the polymer was measured by assessing its electron shifts with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Differential pulse voltammetry (DPV) was also employed to validate the sensing method. The MIP/screen-printed electrode (SPE) and non-imprinted polymer (NIP)/SPE recorded a linear response ranging from 1 to 1000 nmol L^-1 at the 1.765 and 709 nmol L^-1 detection limits. The sensing technique was subsequently utilized to determine the histamine levels in selected samples at room temperature (25 °C). Generally, the sensor allowed the accurate and precise detection of histamine in the fish samples. Furthermore, the approach could be categorized as a simple technique that is low-cost and suitable for on-site detections.

Integrated one-dimensional CuO-nanowire arrays/Cu-foam nanoarchitecture for ultrahigh sensitive and non-enzymatic electrochemical determination of histamine levels in different-bacteria fermented mandarin fish

Integrated one-dimensional CuO-nanowire arrays/Cu-foam (CuO-NWAs/Cu-foam) nanostructure, which was fabricated by oxidation and calcination, has been newly utilized as non-enzymatic electrocatalytic electrode for exploring histamine level. Under optimal condition of pH at 13 and potential at 0.55 V (vs Ag/Ag/Cl), the sensitivity of CuO-NWAs/Cu-foam electrode towards non-enzymatic electrochemical histamine determination presented as high as 12.94 mA mM^-1 cm^-2, linear range spanned between 0.5 and 1046 μM, a detection limit (S/N = 3) was about 44 nM. The unprecedented causes of ultrahigh sensitivity were physically contributed to enhancing active surface area and declining charge transfer resistance. More crucially, the outstanding selectivity, stability and reproducibility facilitated its practical capacity on evaluating histamine levels in different-bacteria fermented mandarin fish, which triggered the potential feasibility for commercializing non-enzymatic electrochemical determination of histamine with high sensitivity, reliable precision and low expenditure.

Biomimetic Electrochemical Sensors Based on Core-Shell Imprinted Polymers for Targeted Sunset Yellow Estimation in Environmental Samples

Magnetic molecularly imprinted polymers (MMIPs) contain the predesigned specialized recognition capability that can be chosen to build credible functional materials, that are easy to handle and have a good degree of specificity. Hence, the given piece of work is intended to design a novel electrochemical sensor incorporating magnetite-based molecularly imprinted polymers. The building materials consisted of a cross-linker (EGDMA), reaction-initiator (AIBN), monomer (methylene succinic acid-MSA), and template molecule (Sunset Yellow-SY dye). MMIPs exhibited a diameter of 57 nm with an irregular shape due to the presence of cavities based on SEM analysis. XRD patterns exhibited crystallinity, as well as amorphous peaks that are attributed to polymeric and non-polymeric frameworks of MMIPs. The crystallite size of the MMIPs from XRD analysis was found to be 16.28 nm based on the Debye-Scherrer's equation. Meanwhile, the FTIR bands showed the synthesis of MMIPs using monomer and methylene succinic acid. The sorption data at the optimized operating conditions (pH 2, sorbent dosage 3 mg, time 18 min) showed the highest sorption capacity of 40 mg/g. The obtained data best fitted to the Langmuir sorption isotherm and followed the pseudo-second-order kinetics. The magneto-sensors were applied for ultrasensitive, rapid, and simple sensing of SY dye. The electrochemical experiments were run at the operating condition range of (scan rate 10-50 mV/s, tads 0-120 s, pH 5-9, potential range 1-1.5 V for CV and 1-1.3 V for SWAdASV). The linear range of detection was set to 1.51 × 10^-6 M to 1.51 × 10^-6 M posing LOD and LOQ values of 8.6242 × 10^-5 M and 0.0002874 M, respectively. The regression analysis value for the calibration was found to be 0.950. Additionally, high adsorption efficiency, selectivity, reusability, and strong structural stability of the magneto-sensors showed potential use for SY detection in real samples. These characteristics make MMIPs a viable electrochemical substrate for the detection of chemical contaminants in the environment and in health-related products.

In situ engineering of Au-Ag alloy embedded PEDOT nanohybrids at a solvent/non-solvent interface for the electrochemical enzyme-free detection of histamine

Steadfast efforts have been made to develop novel materials and incorporate them into functional devices for practical applications, pushing the research on electroactive materials to the forefront of nano electronics. Liquid/liquid interface-assisted polymerization offers a scalable methodology to fabricate hybrid materials with multifunctional applications, in contrast to the conventional and ubiquitous routes. Here, we explored this efficient and versatile approach toward the in situ tailoring of Au-Ag alloy nanostructures with a conducting polymer, poly(3,4-ethylene-dioxythiophene) (PEDOT). With the appropriate choice of organic and inorganic phases for the distribution of monomer and oxidant, the miscibility restraints of the reactants in a single phase were alleviated. Effective nanostructure tuning of highly crystalline and electroactive PEDOT/Au-Ag alloy has been achieved by varying the molar ratio of Au³⁺/Ag⁺ in the reaction mixture. The as-synthesized composite is further explored to detect neuromodulator histamine (HA), which displays high sensitivity with a limit of detection (LOD) of 1.5 nM, and selectivity even in the presence of various interfering analogs of 10-fold concentration. Subsequently, density functional theory (DFT) simulations are employed to assess the mode of interaction between HA and the electroactive surfaces. The competency to detect HA in preserved food entails its potential in food spoilage monitoring. Furthermore, the detection of histamine generated by sub-cultured human neuronal cells SH-SY5Y proves its practical viability in health monitoring devices.

An innovative dual recognition aptasensor for specific detection of Staphylococcus aureus based on Au/Fe3O4 binary hybrid

Pathogenic bacteria cause disease outbreaks and threaten human health, prompting the research on advanced detection assays. Herein, we developed a selective molecular imprinted aptasensor for sensitive and prompt quantitation of Staphylococcus aureus (S. aureus) bacteria. The aptasensor was constructed by immobilization of aptamer on gold nanoparticles modified magnetic nanoparticles (apt-AuNPs@ Fe₃O₄). A functional monomer (o-phenylenediamine, o-phen) was electro-polymerized on the surface of the as-synthesized nanocomposite in the presence of a template (S. aureus). After removing S. aureus, the formed imprinted sites were available to extract pathogenic bacteria from complicated matrices. The surface morphology of the as-fabricated nanocomposites was characterized using different spectroscopic and electrochemical methods. Moreover, we thoroughly evaluated factors affecting the synthesis and determination procedures. The molecular imprinted aptasensor exhibited a wide linear range of 10¹–10⁷ CFU mL⁻¹ with a Limit of Detection, LOD (signal to noise = 3) of 1 CFU mL⁻¹. The aptasensor detected S. aureus in milk, conduit water, and apple juice samples with good recoveries % and satisfactory relative standard deviations (RSDs %) values.

Double-signal quantification of amoxicillin based on interaction with 4-aminoantipyrine at copper and nitrogen co-doped carbon quantum dots as an artificial nanozyme

An one-pot hydrothermal method was developed for synthesis of carbon quantum dots co-doped with copper and nitrogen (Cu, N@CQDs). The synthesized Cu, N@CQDs has unique advantages such as high fluorescence quantum yield (39.1%) and high catalytic activity. Oxidative coupling of amoxicillin (AMX) with 4-aminoantipyrine (4-NH₂-APE) in the presence of H₂O₂ as an oxidant to produce pink quinoneimine chromogen was carried out with the aid of Cu, N@CQDs as a peroxidase-like catalyst. This system was used for the colorimetric and fluorometric assays of AMX with reliable results. Colorimetric method is based on the measurement of a pink-colored product at λ_max = 505 nm while the fluorometric assay is based on the quenching of the fluorescence emission of Cu, N@CQDs at 440 nm after excitation at 370 nm. For the colorimetric method, the absorption intensity linearly increased over the concentration range 4.3-110.0 µM with LOD (S/N = 3) of 1.3 µM. For the fluorometric method, the emission intensity of Cu, N@CQDs linearly decreased upon addition of AMX in the concentration range 0.2-120.0 µM with a limit of detection (LOD, S/N = 3) of 0.06 µM. The proposed system was applied to the determination of AMX in different real samples such as pharmaceutical capsules, human serum, milk, and conduit water samples with recoveries in the range 95.8-104.1% and relative standard deviation (RSD %) less than 4.1%.