Synthesis and comparison of the performance of two different water-soluble phthalocyanine based electrochemical biosensor.

Herein, a comparative study between novel water-soluble phthalocyanine-based biosensors was performed for the application of glucose sensing. For this purpose, two different copper (II) and manganese (III) phthalocyanines and their water-soluble derivatives were synthesized, and then their role as a supporting material for enzyme immobilization was evaluated by comparing their sensor performances. Two different phthalocyanine (AP-OH2-MnQ (MnPc) and AP-OH2-CuQ (CuPc)) were tested using electrochemical biosensor with immobilized glucose oxidase (GOx). To the best of our knowledge, the related water-soluble phthalocyanine-based glucose biosensors were attempted for the first time, and the developed approach resulted in improved biosensor characteristics. The constructed biosensors GE/MnPc/GOx and GE/CuPc/GOx showed good linearity between 0.003-1.0 mM and 0.05-0.4 mM, respectively. The limit of detection was estimated at 0.0026 mM for the GE/MnPc/GOx and 0.019 mM for the GE/CuPc/GOx. KMapp and sensitivity values were also calculated as 0.026 mM and 175.043 µAmM-1 cm-2 for the GE/MnPc/GOx biosensor and 0.178 mM and 117.478 µAmM-1 cm-2 for the GE/CuPc/GOx biosensor. Moreover, the fabricated biosensors were successfully tested to detect glucose levels in beverages with high recovery results. The present study shows that the proposed water-soluble phthalocyanines could be a good alternative for quick and cheap glucose sensing with improved analytical characteristics.

Role of wearable electrochemical biosensors in monitoring renal function biomarkers in sweat: a review.

Real-time detection of renal biomarkers is crucial for immediate and continuous monitoring of kidney function, facilitating early diagnosis and intervention in kidney-related disorders. This proactive approach enables timely adjustments in treatment plans, particularly in critical situations, and enhances overall patient care. Wearable devices emerge as a promising solution, enabling non-invasive and real-time data collection. This comprehensive review investigates numerous types of wearable sensors designed to detect kidney biomarkers in body fluids such as sweat. It critically evaluates the precision, dependability, and user-friendliness of these devices, contemplating their seamless integration into daily life for continuous health tracking. The review highlights the potential influence of wearable technology on individualized renal healthcare and its role in preventative medicine while also addressing challenges and future directions. The review's goal is to provide guidance to academics, healthcare professionals, and technologists working on wearable solutions for renal biomarker detection by compiling the body of current knowledge and advancements.

An ultrasensitive electrochemical biosensor with dual-amplification mode and enzyme-deposited silver for detection of miR-205-5p.

An electrochemical biosensor based on dual-amplified nucleic acid mode and biocatalytic silver deposition was constructed using catalytic hairpin assembly-hybrid chain reaction (CHA-HCR). The electrochemical detection of silver on the electrode by linear sweep voltammetry (LSV) can be utilized to quantitatively measure miR-205-5p since the amount of silver deposited on the electrode is proportional to the target nucleic acid. The current response values exhibit strong linearity with the logarithm of miR-205-5p concentrations ranging from 0.1 pM to 10 µM, and the detection limit is 28 fM. A consistent trend was found in the results of the qRT-PCR and electrochemical biosensor techniques, which were employed to determine the total RNA recovered from cells, respectively. Moreover, the constructed sensor was used to assess miR-205-5p on various cell counts, and the outcomes demonstrated the excellent analytical efficiency of the proposed strategy. The recoveries ranged from 97.85% to 115.3% with RSDs of 2.251% to 4.869% in human serum samples. Our electrochemical biosensor for miR-205-5p detection exhibits good specificity, high sensitivity, repeatability, and stability. It is a potentially useful sensing platform for tumor diagnosis and tumor type identification in clinical settings.

Novel self-powered sandwich type Aptamer sensor for estrogen detection assisted with peroxidase mimic Cu-MOF.

A novel self-powered and flexible enzymatic biofuel cell (EBFC)-based aptasensor was developed for the sensitive and selective detection of 17 ß-estradiol (E2). A flexible polyvinyl alcohol (PVA)-tannic acid­carbon nanotube/reduced graphene oxide (PTCR) substrate was modified with gold nanoparticles (AuNPs) and thiolated aptamer 1 (Apt1) to yield Apt1@AuNPs/PTCR. A copper-based metal-organic framework (Cu-MOF) with peroxidase mimicking activity was employed to anchor glucose oxidase (GOD) and Apt2, forming the Cu-MOF@GOD/Apt2 tag. When E2 was recognized by Apt1, the anchored E2 quantitatively recognized Cu-MOF@GOD/Apt2 to create a Cu-MOF@GOD/Apt2-E2-Apt1 sandwich structure for glucose oxidation to generate electrical power. Increased E2 concentrations enhanced Cu-MOF@GOD/Apt2 capture and amplified the electrical signal. The electrical power increased linearly as the E2 concentration increased from 1.0 pM to 1.0 nM. The sensor was successfully applied to various food samples and blood serum detection. This work promoted the application of novel self-powered biosensors for food safety analysis.

Flexible and wearable sensor for in situ monitoring of gallic acid in plant leaves.

Gallic acid (GA) is one of the main phenolic components naturally occurring in many plants and foods and has been a subject of increasing interest owing to its antioxidant and anti-mutagenic properties. This study introduces a novel flexible sensor designed for in situ detecting GA in plant leaves. The sensor employs a laser-induced graphene (LIG) flexible electrode, enhanced with MXene and molybdenum disulfide (MoS2) nanosheets. The MXene/MoS2/LIG flexible sensor not only demonstrates exceptional mechanical properties, covering a wide detection range of 1-1000 µM for GA, but also exhibits remarkable selectivity and stability. The as-prepared sensor was successfully applied to in situ determination of GA content in strawberry leaves under salt stress. This innovative sensor opens an attractive avenue for in situ measurement of metabolites in plant bodies with flexible electronics.

Electrochemical aptasensor based on a dual signal amplification strategy of 1-AP-CNHs and ROP for highly sensitive detection of ERα.

Estrogen receptor alpha (ERα) serves as a crucial biomarker for early breast cancer diagnosis. In this study, we proposed an electrochemical aptasensor with nanomaterial carbon nanohorns/gold nanoparticle composites (1-AP-CNHs/AuNPs) as the substrate, and the primary amine groups on the antibody initiated the ring-opening polymerization (ROP) of monomer amino acid-ferrocene (NCA-Fc) on the electrode surface for ultrasensitive detection of ERα. The composite of 1-AP-CNHs/AuNPs not only possessed more active sites, but also increased the specific surface area of the electrode and allowed a large amount of ferrocene polymer long chains to be grafted onto the electrode surface to achieve signal amplification. Under optimal conditions, the detection limit of the method was 11.995 fg mL-1 with a detection range of 100 fg mL-1-100 ng mL-1. In addition, the biotin-streptavidin system was used to further improve the sensitivity of the sensor. Importantly, this approach could be applied for the practical detection of ERα in real samples.

Primer exchange reaction assisted CRISPR/Cas9 cleavage for detection of dual microRNAs with electrochemistry method.

An electrochemical sensor assisted by primer exchange reaction (PER) and CRISPR/Cas9 system (PER-CRISPR/Cas9-E) was established for the sensitive detection of dual microRNAs (miRNAs). Two PER hairpin (HP) were designed to produce a lot of extended PER products, which could hybridize with two kinds of hairpin probes modified on the electrode and initiate the cleavage of two CRISPR/Cas9 systems guided by single guide RNAs (sgRNAs) with different recognition sequences. The decrease of the two electrochemical redox signals indicated the presence of dual-target miRNAs. With the robustness and high specificity of PER amplification and CRISPR/Cas9 cleavage system, simultaneous detection of two targets was achieved and the detection limits for miRNA-21 and miRNA-155 were 0.43 fM and 0.12 fM, respectively. The developed biosensor has the advantages of low cost, easy operation, and in-situ detection, providing a promising platform for point-of-care detection of multiple miRNAs.

A sensitive tobramycin electrochemical aptasensor based on multiple signal amplification cascades.

The residue of tobramycin, a broad spectrum antibiotic commonly used in animal husbandry, has evitable impact on human health, which may cause kidney damage, respiratory paralysis, neuromuscular blockade and cross-allergy in humans. Sensitive monitoring of tobramycin in animal-derived food products is therefore of great importance. Herein, a new aptamer electrochemical biosensor for sensing tobramycin with high sensitivity is demonstrated via exonuclease III (Exo III) and metal ion-dependent DNAzyme recycling and hybridization chain reaction (HCR) signal amplification cascades. Tobramycin analyte binds aptamer-containing hairpin probe to switch its conformation to expose the toehold sequence, which triggers Exo III-based catalytic digestion of the secondary hairpin to release many DNAzyme strands. The substrate hairpins immobilized on the Au electrode (AuE) are then cyclically cleaved by the DNAzymes to form ssDNAs, which further initiate HCR formation of lots of long methylene blue (MB)-tagged dsDNA polymers on the AuE. Subsequently electro-oxidation of these MB labels thus exhibit highly enhanced currents for sensing tobramycin within the 5-1000 nM concentration range with an impressive detection limit of 3.51 nM. Furthermore, this strategy has high selectivity for detecting tobramycin in milk and shows promising potential for detect other antibiotics for food safety monitoring.

Signal-On Detection of Caspase-3 with Methylene Blue-Loaded Metal-Organic Frameworks as Signal Reporters.

In this work, we report on an electrochemical method for the signal-on detection of caspase-3 and the evaluation of apoptosis based on the biotinylation reaction and the signal amplification of methylene blue (MB)-loaded metal-organic frameworks (MOFs). Zr-based UiO-66-NH2 MOFs were used as the nanocarriers to load electroactive MB molecules. Recombinant hexahistidine (His6)-tagged streptavidin (rSA) was attached to the MOFs through the coordination interaction between the His6 tag in rSA and the metal ions on the surface of the MOFs. The acetylated peptide substrate Ac-GDEVDGGGPPPPC was immobilized on the gold electrode. In the presence of caspase-3, the peptide was specifically cleaved, leading to the release of the Ac-GDEVD sequence. A N-terminal amine group was generated and then biotinylated in the presence of biotin-NHS. Based on the strong interaction between rSA and biotin, rSA@MOF@MB was captured by the biotinylated peptide-modified electrode, producing a significantly amplified electrochemical signal. Caspase-3 was sensitively determined with a linear range from 0.1 to 25 pg/mL and a limit of detection down to 0.04 pg/mL. Further, the active caspase-3 in apoptosis inducer-treated HeLa cells was further quantified by this method. The proposed signal-on biosensor is compatible with the complex biological samples and shows great potential for apoptosis-related diagnosis and the screening of caspase-targeting drugs.

Controllable self-cleaning FET self-assembled RNA-cleaving DNAzyme based DNA nanotree for culture-free Staphylococcus aureus detection.

Staphylococcus aureus (SA) poses a serious risk to human and animal health, necessitating a low-cost and high-performance analytical platform for point-of-care diagnostics. Cellulose paper-based field-effect transistors (FETs) with RNA-cleaving DNAzymes (RCDs) can fulfill the low-cost requirements, however, its high hydrophilicity and lipophilicity hinder biochemical modification and result in low sensitivity, poor mechanical stability and poor fouling performance. Herein, we proposed a controllable self-cleaning FET to simplify biochemical modification and improve mechanical stability and antifouling performance. Then, we constructed an RCD-based DNA nanotree to significantly enhance the sensitivity for SA detection. For controllable self-cleaning FET, 1 H,1 H,2 H,2 H-perfluorodecyltrimethoxysilane based-polymeric nanoparticles were synthesized to decorate cellulose paper and whole carbon nanofilm wires. O2 plasma was applied to regulate to reduce fluorocarbon chain density, and then control the hydrophobic-oleophobic property in sensitive areas. Because negatively charged DNA affected the sensitivity of semiconducting FETs, three Y-shaped branches with low-cost were designed and applied to synthesize an RCD-based DNA-Nanotree based on similar DNA-origami technology, which further improved the sensitivity. The trunk of DNA-Nanotree was composed of RCD, and the canopy was self-assembled using multiple Y-shaped branches. The controllable self-cleaning FET biosensor was applied for SA detection without cultivation, which had a wide linear range from 1 to 105 CFU/mL and could detect a low value of 1 CFU/mL.

Development of Molecularly Imprinted Magnetic Amino Acid-Based Nanoparticles for Voltammetric Analysis of Lead Ions in Honey.

Lead (Pb) is a hazardous metal that poses a significant threat to both the environment and human health. The presence of Pb in food products such as honey can pose a significant risk to human health and is therefore important to detect and monitor. In this study, we propose a voltammetric detection method using molecularly imprinted polymer (MIP) electrodes to detect Pb (II) ions in honey. Pb (II) ion-imprinted amino acid-based nanoparticles with magnetic properties on a carbon paste electrode (MIP-CPE) were designed to have high sensitivity and selectivity towards Pb (II) ions in the honey sample. Zetasizer measurements, electron spin resonance, and scanning electron microscopy were used to characterize magnetic polymeric nanoparticles. The results showed that the voltammetric detection method using MIP-CPE was able to accurately detect Pb (II) ions in honey samples with a low detection limit. The proposed method offers a simple, rapid, cost-effective solution for detecting Pb (II) ions in honey. It could potentially be applied to other food products to ensure their safety for human consumption. The MIP-CPE sensor was designed to have high sensitivity and selectivity towards Pb (II) ions in the honey sample. The results showed that the technique was able to deliver highly sensitive results since seven different concentrations were prepared and detected to obtain an R2 of 0.9954, in addition to a low detection limit (LOD) of 0.0912 µM and a low quantification limit (LOQ) of 0.276 µM. Importantly, the analysis revealed no trace of Pb (II) ions in the honey samples obtained from Cyprus.

Evaluation of Transducer Elements Based on Different Material Configurations for Aptamer-Based Electrochemical Biosensors.

The selection of an appropriate transducer is a key element in biosensor development. Currently, a wide variety of substrates and working electrode materials utilizing different fabrication techniques are used in the field of biosensors. In the frame of this study, the following three specific material configurations with gold-finish layers were investigated regarding their efficacy to be used as electrochemical (EC) biosensors: (I) a silicone-based sensor substrate with a layer configuration of 50 nm SiO/50 nm SiN/100 nm Au/30-50 nm WTi/140 nm SiO/bulk Si); (II) polyethylene naphthalate (PEN) with a gold inkjet-printed layer; and (III) polyethylene terephthalate (PET) with a screen-printed gold layer. Electrodes were characterized using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) to evaluate their performance as electrochemical transducers in an aptamer-based biosensor for the detection of cardiac troponin I using the redox molecule hexacyanoferrade/hexacyaniferrade (K3[Fe (CN)6]/K4[Fe (CN)6]. Baseline signals were obtained from clean electrodes after a specific cleaning procedure and after functionalization with the thiolate cardiac troponin I aptamers "Tro4" and "Tro6". With the goal of improving the PEN-based and PET-based performance, sintered PEN-based samples and PET-based samples with a carbon or silver layer under the gold were studied. The effect of a high number of immobilized aptamers will be tested in further work using the PEN-based sample. In this study, the charge-transfer resistance (Rct), anodic peak height (Ipa), cathodic peak height (Ipc) and peak separation (∆E) were determined. The PEN-based electrodes demonstrated better biosensor properties such as lower initial Rct values, a greater change in Rct after the immobilization of the Tro4 aptamer on its surface, higher Ipc and Ipa values and lower ∆E, which correlated with a higher number of immobilized aptamers compared with the other two types of samples functionalized using the same procedure.

An overview of signal amplification strategies and construction methods on phage-based biosensors.

Phages are a class of viruses that specifically infect host bacteria. Compared to other recognition elements, phages offer several advantages such as high specificity, easy to obtain and good environmental tolerance, etc. These advantages underscore the potential of phages as recognition elements in the construction of biosensors. Therefore, the phage-based biosensors are currently garnering widespread attention for detecting pathogens in recent years. However, the test performance such as detection limit, sensitivity and stability of exicting phage-based biosensors require enhancement. In the design of sensors, the selection of various materials and construction methods significantly influences the test performance of the sensor, and employing appropriate signal amplification strategies and construction methods to devise biosensors based on different principles is an effective strategy to enhance sensor performance. The manuscript primarily focuses on the signal amplification strategies and construction methods employed in phage-based biosensors recent ten years, and summarizes the advantages and disadvantages of different signal amplification strategies and construction methods. Meanwhile, the manuscript discusses the relationship between sensor performance and various materials and construction methods, and reviews the application progress of phage-based electrochemical biosensors in the detection of foodborne bacteria. Furthermore, the manuscript points out the present limitations and the future research direction for the field of phage-based biosensors, so as to provide the reference for developing high-performance phage-based biosensors.

Graphene oxide/Cu-MOF-based electrochemical immunosensor for the simultaneous detection of Mycoplasma pneumoniae and Legionella pneumophila antigens in water.

The combination of copper-metal organic framework (Cu-MOF) with graphene oxide (GO) has received growing interest in electrocatalysis, energy storage and sensing applications. However, its potential as an electrochemical biosensing platform remains largely unexplored. In this study, we introduce the synthesis of GO/Cu-MOF nanocomposite and its application in the simultaneous detection of two biomarkers associated with lower respiratory infections, marking the first instance of its use in this capacity. The physicochemical properties and structural elucidation of this composite were studied with the support of XRD, FTIR, SEM and electrochemical techniques. The immunosensor was fabricated by drop casting the nanocomposite on dual screen-printed electrodes followed by functionalization with pyrene linker. The covalent immobilization of the monoclonal antibodies of the bacterial antigens of Mycoplasma pneumoniae (M. pneumoniae; M. p.) and Legionella pneumophila (L. pneumophila; L. p.) was achieved using EDC-NHS chemistry. The differential pulse voltammetry (DPV) signals of the developed immunosensor platform demonstrated a robust correlation across a broad concentration range from 1 pg/mL to 100 ng/mL. The immunosensor platform has shown high degree of selectivity against antigens for various respiratory pathogens. Moreover, the dual immunosensor was successfully applied for the detection of M. pneumoniae and L. pneumophila antigens in spiked water samples showing excellent recovery percentages. We attribute the high sensitivity of the immunosensor to the enhanced electrocatalytic characteristics, stability and conductivity of the GO-MOF composite as well as the synergistic interactions between the GO and MOF. This immunosensor offers a swift analytical response, simplicity in fabrication and instrumentation, rendering it an appealing platform for the on-field monitoring of pathogens in environmental samples.

Label-free electrochemical biosensor based on dual amplification of gold nanoparticles and polycaprolactones for CEA detection.

Carcinoembryonic Antigen (CEA), an acidic glycoprotein with human embryonic antigen properties, is found on the surface of cancer cells that have differentiated from endodermal cells. This paper presents a label-free electrochemical immunoassay for the dual amplification detection of CEA using gold nanoparticles loaded with polypyrrole polydopamine (Au/PPy-PDA) and polymerized polycaprolactone (Ng-PCL) prepared by ring-opening polymerization (ROP). First, the composite Au/PPy-PDA was adhered to the electrode surface. Then, gold nanoparticles form a Au-S bond with the sulfhydryl group in Apt1 to secure it on the electrode surface. Subsequently, the non-specific binding sites on the electrodes surface are closed by bovine serum albumin (BSA). Next, CEA is dropped onto the electrode surface, which is immobilized by antigen-antibody specific recognition, and the carboxyl-functionalized Apt2 forms a "sandwich structure" of antibody-antigen-antibody by specific recognition. Polymeric Ng-PCL is adhered to the electrode surface, leading to an increase in the electrochemical impedance signal, resulting in a complete chain of signal analysis. Finally, the response signal is detected by electrochemical impedance spectroscopy (EIS). Under optimal experimental conditions, the method has the advantages of high sensitivity and wide linear range (1 pg mL-1∼100 ng mL-1), and the lower limit of detection (LOD) is 0.234 pg mL-1. And it has the same high sensitivity, selectivity and interference resistance for the real samples detection. Thus, it provides a new way of thinking about biomedical and clinical diagnosis.

An electrochemical biosensor based on mild reduction-activated CRISPR/Cas12a system for sensitive detection of circulating tumor cells.

Circulating tumor cell (CTC) has been a valuable biomarker for the diagnosis of breast cancer, while folate receptor is a kind of cell surface receptor glycoprotein which is overexpressed in breast cancer. In this work, we have designed and fabricated an electrochemical biosensor for sensitive detection of folate receptor-positive CTCs based on mild reduction assisted CRISPR/Cas system. Specifically, folate functionalized magnetic beads are firstly prepared to capture CTCs owing to the strong affinity between folate and the folate receptors on the surface of cells. Then, the cell membranes are treated by mild reduction so as to expose a large number of free sulfhydryl groups, which can be coupled with maleimide-DNA to introduce the signal amplified CRISPR/Cas12a system. After the trans-cleavage activity of CRISPR/Cas12a is activated, the long chain DNA modified with electroactive molecules methylene blue can be randomly cleaved into short DNA fragments, which are then captured on the graphite electrode through the host-guest recognition with cucurbit [7]uril, generating highly amplified electrochemical signal corresponding to the number of CTCs. The electrochemical biosensor not only demonstrates the sensitivity with a low detection limit of 2 cells/mL, but also highlights its excellent selectivity and stability in complex environment. Therefore, our biosensor may provide an alternative tool for the analysis of CTCs.

Development and characterization of a non-enzymatic electrochemical biosensor for rapid determination of sorbent-based extracted trazodone and doxepin in complicated samples.

BACKGROUND: Given the importance of achieving optimal therapeutical concentration in patients treated with antidepressants, this study investigates a novel technique for the simultaneous determination of trazodone (TRZ) and doxepin (DOX) in human plasma and serum samples for the first time. RESULTS: To achieve simultaneous determination of two antidepressants, TRZ and DOX, a novel detection system was designed: a non-enzymatic voltammetric biosensor based on boron-reduced graphene oxide/manganese oxide nanoparticles (GCE/B-rGO/MnO NPs). The detection was accomplished after pre-concentration and extraction trace amounts of the analytes using the thin film-solid phase microextraction (TF-SPME) technique, which employed polyvinyl alcohol/polyvinyl acetate/copper oxide nanoparticles (PVA/PVAc/CuO NPs) electrospun nanofibers. The successful preparation of composite nanofibers and modified electrodes was confirmed using the evaluation of field emission-scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDX). Also, the composite nanofibers were characterized with attenuated total reflectance-Fourier transform-infrared (ATR-FT-IR) and X-ray diffraction (XRD). In the solution of TRZ and DOX, under optimum experimental conditions, the linear dynamic ranges (LDRs) were 0.1-20.0 µmol L-1 and 0.5-27.0 µmol L-1, respectively. Also, the limit of detection (LOD) values of TRZ and DOX were 0.032 and 0.150 µmol L-1. SIGNIFICANCE: PVAc acts as a cross-linking agent for PVA, and their mixture is effective for sample preparation and pre-concentration of analytes in complex matrices. Also, adding CuO NPs to this polymeric mixture enhanced the adsorption efficiency. Taking advantage of the high surface area of MnO NPs and the high electrical conductivity of B-rGO, and considering the superiority of their simultaneous utilization, the constructed electrochemical biosensor is both cost-effective and rapid. It demonstrates excellent stability, repeatability, and sensitivity for the simultaneous determination of TRZ and DOX under optimal conditions. This biosensor, the first of its kind, is specifically designed for the simultaneous determination of TRZ and DOX in human plasma and serum samples, representing a significant advancement in biosensing technology.

An origami microfluidic paper device based on core-shell Cu@Cu2S@N-doped carbon hollow nanocubes.

BACKGROUD: The global prevalence of diabetes mellitus, a serious chronic disease with fatal consequences for millions annually, is of utmost concern. The development of efficient and simple devices for monitoring glucose levels is of utmost significance in managing diabetes. The advancement of nanotechnology has resulted in the indispensable utilization of advanced nanomaterials in high-performance glucose sensors. Modulating the morphology and intricate composition of transition metals represents a viable approach to exploit their structure/function correlation, thereby achieving optimal electrocatalytic performance of the synthesized catalysts. RESULTS: Herein, a sensitive and rapid Cu-encapsulated Cu2S@nitrogen-doped carbon (Cu@Cu2S@N-C) hollow nanocubes-functionalized microfluidic paper-based analytical device (µ-PAD) was fabricated. Through a delicate sacrificial template/interface technique and thermal decomposition, inter-connected hollow networks were formed to boost the active sites, and the carbon shell was coated to protect Cu from being oxidation. For application, the constructed µ-PAD is used for glucose sensing utilizing an origami automated sample pretreatment system enabled by a simple application of strong alkaline solution on wax paper. Under optimal circumstances, the Cu@Cu2S@N-C electrochemical biosensor exhibits broad detection range of 2-7500 µM (R2 = 0.996) with low detection limit of 0.16 µM (S/N = 3) and high sensitivity of 1996 µA mM-1 cm-2. Additionally, the constructed µ-PAD also exhibited excellent selectivity, stability, and reproducibility. SIGNIFICANCE: By rationally designing the double-shell hollow nanostructure and introducing Cu-encapsulated inner layer, the synthesized Cu@Cu2S@N-C hollow nanocubes show large specific surface area, short diffusion channels, and high stability. The proposed origami µ-PAD has been successfully applied to serum samples without any additional sample preparation steps for glucose determination, offering a new perspective for early nonenzymatic glucose diagnosis.

One-pot electrochemical detection of foodborne pathogen based on in situ nucleic acid amplification and wash-free assay.

A signal amplification electrochemical biosensor chip was developed to integrate loop-mediated isothermal amplification (LAMP) based on in situ nucleic acid amplification and methyl blue (MB) serving as the hybridization redox indicator for sensitive and selective foodborne pathogen detection without a washing step. The electrochemical biosensor chip was designed by a screen-printed carbon electrode modified with gold nanoparticles (Au NPs) and covered with polydimethylsiloxane membrane to form a microcell. The primers of the target were immobilized on the Au NPs by covalent attachment for in situ amplification. The electroactive MB was used as the electrochemical signal reporter and embedded into the double-stranded DNA (dsDNA) amplicons generated by LAMP. Differential pulse voltammetry was introduced to survey the dsDNA hybridization with MB, which differentiates the specifically electrode-unbound and -bound labels without a washing step. Pyrene as the back-filling agent can further improve response signaling by reducing non-specific adsorption. This method is operationally simple, specific, and effective. The biosensor showed a detection linear range of 102-107 CFU mL-1 with the limit of detection of 17.7 CFU mL-1 within 40 min. This method showed promise for on-site testing of foodborne pathogens and could be integrated into an all-in-one device.

Role of miRNA-21 in cancer and its application in electrochemical bioanalysis.

GRAPHICAL ABSTRACT[Formula: see text].