Label free electrochemical sensor for Pb2+ based on graphene oxide mediated deposition of silver nanoparticles

Development and application of bisphenol S electrochemical immunosensor and iridium oxide nanoparticle-based lateral flow immunoassay

Bisphenol S (BPS) is a common pollutant in the environment and has posed a potential threat to aquatic animals and human health. To accurately assess the pollution level and ecological risk of BPS, there is an urgent need to establish simple and sensitive detection methods for BPS. In this study, BPS complete antigen was successfully prepared by introducing methyl 4-bromobutyrate and coupling bovine serum albumin (BSA). The monoclonal antibody against BPS (anti-BPS mAb) with high affinity (1: 256,000) was developed based on the BPS complete antigen, which showed low cross-reactivity with BPS structural analogues. Then, an electrochemical immunosensor was constructed to detect BPS using multi-walled carbon nanotubes and gold nanoflower composites as signal amplification elements and using anti-BPS mAb as the probe. The electrochemical immunosensor had a linear range from 1 to 250 ng⋅mL-1 and a limit of detection (LOD) down to 0.6 ng⋅mL-1. Additionally, a more stable and sensitive lateral flow immunoassay (LFIA) for BPS was developed based on iridium oxide nanoparticles, with a visual detection limit of 1 ng⋅mL-1, which was 10 times lower than that of classical Au-NPs LFIA. After evaluation of their stability and specificity, the reliability of these two methods were further validated by measuring BPS concentrations in the water and fish tissues. Thus, this study provides sensitive, robust and rapid methods for the detection of BPS in the environment and organisms, which can provide a methodological reference for monitoring environmental contaminants.

A dual-cycle amplification-based electrochemical platform for sensitive detection of tobramycin

BACKGROUND

Tobramycin (TOB), an essential aminoglycoside antibiotic in human life, poses potential threats due to its residues in the environment. The primary concern is the adverse impact of excessive TOB on human kidneys, hearing, and other organs, significantly affecting human health. Constructing a sensitive electrochemical platform for simple and rapid trace detection is crucial. Herein, to enhance the sensitivity of TOB detection in the environment and mitigate the risks associated with residual antibiotics, an ultrasensitive electrochemical aptasensor was developed.

RESULTS

The sensor employs a dual-cycle amplification strategy involving catalytic hairpin assembly (CHA) and exonuclease III (Exo III) for efficient signal amplification. Simultaneously, the electrode performance was optimized by incorporating gold nanowires (AuNWs) onto the surface of reduced graphene oxide (PDA-rGO). Specifically, in the presence of TOB, which binds to the aptamer (Apt), dsDNA dissociates, releasing cDNA to open hairpin 1 (HP1) and initiate the CHA cycle with the participation of hairpin 2 (HP2). Exo III shears HP1 in the HP1/HP2 complex, freeing HP2 to participate in the CHA cycle again. Ultimately, a significant amount of signal label is retained on the electrode by hybridizing with sheared HP1, generating a robust electrical signal.

SIGNIFICANCE

Through the signal amplification strategy, the aptasensor design provides a broad linear range of 0.005-500 nM, with a low detection limit of 0.112 pM for TOB. It is worth mentioning that the aptasensor displayed favorable stability, specificity, and reproducibility, and has been successfully applied to practical samples, demonstrating its utility in practical applications.

Constructing Fe2O3 nanoparticles in nitrogen-doped carbon materials to enhance the electrochemical sensing performance of Pb2+ and Cd2

N-doped carbon materials are known for their high conductivity, rich N content, and high adsorption activity. When combined with Fe2O3 to form nanocomposites, they can improve the conductivity of Fe2O3 and cause significant changes in the electrochemical sensing interface with the influence of their unique electronic structure. In this work, N-doped carbon nanocomposites (Fe2O3@NCNPs-x) modified with Fe2O3 nanoparticles (Fe2O3 NPs) were synthesized by a simple emulsion polymerization method and carbonized under Ar at a high temperature. X-ray photoelectron spectroscopy indicated that compared with undoped Fe2O3 NPs, the π bond of Fe2O3@NCNPs-1.5 was negatively charged due to the lone pair of electrons near the N atom, acting as an electron donor that enhanced the interaction with HMIs and electron transport, therefore generating more active sites on the surface of Fe2O3@NCNPs-1.5. The obtained Fe2+/Fe3+ ratio was about two times higher than that of undoped Fe2O3 NPs (Fe2O3@NCNPs-1.5: Fe2+/Fe3+ = 1.24; Fe2O3 NPs: Fe2+/Fe3+ = 0.61). The surface oxygen vacancy (OV) concentration reached the maximum level (Fe2O3@NCNPs-1.5: OVs/O1s = 41.7%; Fe2O3 NPs: OVs/O1s = 22%). Fe2O3@NCNPs-1.5/GCE also showed enhanced electrochemical performance for detecting Pb2+ and Cd2+, with a limit of detection (LOD, S/N = 3) of 4.92 and 18.79 nM, respectively. Electrochemical adsorption tests suggested that Fe2O3@NCNPs-1.5/GCE had the strongest adsorption capacity for Pb2+ and Cd2+ in comparison with other modified electrodes, suggesting that different N contents led to different absorbability for heavy metal ions (HMIs). Therefore, when the metal oxide nanoparticles are loaded on compatible carriers, the jointly constructed nanocomposites can be used as the active materials for efficiently detecting HMIs, providing a new concept for designing highly active electrochemical sensors.

An overview of Structured Biosensors for Metal Ions Determination

The determination of metal ions is important for nutritional and toxicological assessment. Atomic spectrometric techniques are highly efficient for the determination of these species, but the high costs of acquisition and maintenance hinder the application of these techniques. Inexpensive alternatives for metallic element determination are based on dedicated biosensors. These devices mimic biological systems and convert biochemical processes into physical outputs and can be used for the sensitive and selective determination of chemical species such as cations. In this work, an overview of the proposed biosensors for metal ions determination was carried out considering the last 15 years of publications. Statistical data on the applications, response mechanisms, instrumentation designs, applications of nanomaterials, and multielement analysis are herein discussed.

Detection of pollutants in water bodies: electrochemical detection or photo-electrochemical detection?

The massive discharge of pollutants including endocrine-disrupting chemicals (EDCs), heavy metals, pharmaceuticals and personal care products (PPCPs) into water bodies is endangering the ecological environment and human health, and needs to be accurately detected. Both electrochemical and photo-electrochemical detection methods have been widely used for the detection of these pollutants, however, which one is better for the detection of different environmental pollutants? In this feature article, different electrochemical and photo-electrochemical detection methods are summarized, including the principles, classification, common catalysts, and applications. By summarizing the advantages and disadvantages of different detection methods, this review provides a guide for other researchers to detect pollutants in water bodies by using electrochemical and photo-electrochemical analysis.

Gold nanoparticles mediated designing of versatile aptasensor for colorimetric/electrochemical dual-channel detection of aflatoxin B1

This work is aimed to develop of a new class of versatile aptasensor to specifically detect aflatoxin B1 (AFB1) using dual-channel detection method. To achieve this objective, gold nanoparticles (AuNPs) having peroxidase-like activity and capability of promoting silver deposition were used as the versatile label for both colorimetric and electrochemical techniques. First of all, aptamer (apt) modified Fe₃O₄@Au magnetic beads (MBs-apt) and cDNA modified AuNPs (cDNA-AuNPs) were prepared to use as capture probes and signal probes, respectively. Taking advantage of hybridization reaction between apt and cDNA, these two probes were coupled with each other to generate MBs-apt/cDNA-AuNPs bioconjugations. The high affinity between apt and AFB1 made cDNA-AuNPs detached from MBs-apt, and the released signal probes were separated and collected using an external magnetic field and used for both colorimetric and electrochemical detection channels. The dual-channel signals were directly proportional to logarithm of AFB1 concentration within the ranges of 5-200 ng mL^-1 and 0.05-100 ng mL^-1. The detection limit can reach as low as 35 pg mL^-1 and 0.43 pg mL^-1 for colorimetric and electrochemical channel, respectively. Moreover, the proposed aptasensor has been successfully applied to determine AFB1 in corn samples with satisfactory results. This dual-channel detection method can not only improve the detection precision and diversity significantly, but also can reduce the false-negative and-positive rates in food quality monitoring. We believe we have provided a general strategy with the convincing dual-readout mode which possess great promising in all of the aptamer related fields.

A review on graphene-based nanocomposites for electrochemical and fluorescent biosensors

Biosensors with high sensitivity, selectivity and a low limit of detection, reaching nano/picomolar concentrations of biomolecules, are important to the medical sciences and healthcare industry for evaluating physiological and metabolic parameters.

Selective detection of water pollutants using a differential aptamer-based graphene biosensor

Graphene field-effect transistor (GFET) sensors are an attractive analytical tool for the detection of water pollutants. Unfortunately, this application has been hindered by the sensitivity of such sensors to nonspecific disturbances caused by variations of environmental conditions. Incorporation of differential designs is a logical choice to address this issue, but this has been difficult for GFET sensors due to the impact of fabrication processes and material properties. This paper presents a differential GFET affinity sensor for the selective detection of water pollutants in the presence of nonspecific disturbances. This differential design allows for minimization of the effects of variations of environmental conditions on the measurement accuracy. In addition, to mitigate the impact of the fabrication process and material property variations, we introduce a compensation scheme for the individual sensing units of the sensor, so that such variations are accounted for in the compensation-based differential sensing method. We test the use of this differential sensor for the selective detection of the water pollutant 17β-estradiol in buffer and tap water. Consistent detection results can be obtained with and without interferences of pH variations, and in tap water where unknown interferences are present. These results demonstrate that the differential graphene affinity sensor is capable of effectively mitigating the effects of nonspecific interferences to enable selective water pollutant detection for water quality monitoring.

Progress in utilisation of graphene for electrochemical biosensors

This review discusses recent graphene (GR) electrochemical biosensor for accurate detection of biomolecules, including glucose, hydrogen peroxide, dopamine, ascorbic acid, uric acid, nicotinamide adenine dinucleotide, DNA, metals and immunosensor through effective immobilization of enzymes, including glucose oxidase, horseradish peroxidase, and haemoglobin. GR-based biosensors exhibited remarkable performance with high sensitivities, wide linear detection ranges, low detection limits, and long-term stabilities. Future challenges for the field include miniaturising biosensors and simplifying mass production are discussed.

A sensitive LSPR sensor based on glutathione-functionalized gold nanoparticles on a substrate for the detection of Pb2+ ions

A plasmonic probe based on gold nanoparticles (AuNPs) on a solid substrate for the detection of Pb²⁺ was developed.

An ultrasensitive electrochemical immunosensor based on C60-modified polyamidoamine dendrimers and Au NPs for co-catalytic silver deposition

C₆₀-Modified polyamidoamine dendrimers and Au NPs for the co-catalytic deposition of silver, used for ultrasensitive electrochemical immunosensing.

Fe(III)-based metal-organic framework-derived core-shell nanostructure: Sensitive electrochemical platform for high trace determination of heavy metal ions

A new core-shell nanostructured composite composed of Fe(III)-based metal-organic framework (Fe-MOF) and mesoporous Fe₃O₄@C nanocapsules (denoted as Fe-MOF@mFe₃O₄@mC) was synthesized and developed as a platform for determining trace heavy metal ions in aqueous solution. Herein, the mFe₃O₄@mC nanocapsules were prepared by calcining the hollow Fe₃O₄@C that was obtained using the SiO₂ nanoparticles as the template, followed by composing the Fe-MOF. The Fe-MOF@mFe₃O₄@mC nanocomposite demonstrated excellent electrochemical activity, water stability and high specific surface area, consequently resulting in the strong biobinding with heavy-metal-ion-targeted aptamer strands. Furthermore, by combining the conformational transition interaction, which is caused by the formation of the G-quadruplex between a single-stranded aptamer and high adsorbed amounts of heavy metal ions, the developed aptasensor exhibited a good linear relationship with the logarithm of heavy metal ion (Pb²⁺ and As³⁺) concentration over the broad range from 0.01 to 10.0nM. The detection limits were estimated to be 2.27 and 6.73 pM toward detecting Pb²⁺ and As³⁺, respectively. The proposed aptasensor showed good regenerability, excellent selectivity, and acceptable reproducibility, suggesting promising applications in environment monitoring and biomedical fields.

The application of a bee glue-modified sensor in daclatasvir dual effect detection

A simple and novel carbon paste sensor containing chemically mixed propolis (bee glue) and graphene oxide (GO) was prepared, then electrochemical deposition of silver nanoparticles (AgNPs) was performed to fabricate a selective and sensible electrochemical sensor to detect Daclatasvir (DAC).

Silver nanoparticle-modified electrode for the determination of nitro compound-containing pesticides

This paper reports the electroanalytical determination of pendimethalin and ethyl parathion by square-wave adsorptive stripping voltammetry using a material comprised of chitosan-stabilized silver nanoparticles to modify a glassy carbon electrode. Under optimized experimental conditions, the peak current was found to vary linearly with the concentration of pendimethalin in the range of 70 to 2000 nmol L(-1) and with concentration of ethyl parathion in the range of 40 to 8000 nmol L(-1). Detection limits of 36 and 40 nmol L(-1) were obtained for pendimethalin and ethyl parathion, respectively. The silver - nanoparticle-modified electrode was successfully employed for the analysis of pesticides in tap and mineral water (pendimethalin) and in lettuce and honey (ethyl parathion) samples. Pendimethalin recovery was between 94 and 100 %, and ethyl parathion recovery was between 97 and 101 %, indicating no significant matrix interference effects on the analytical results. The accuracy of the electroanalytical methodology using the proposed modified electrode was also compared to that of the UV-vis spectrophotometric method.