Label-free and ultrasensitive electrochemical transferrin detection biosensor based on a glassy carbon electrode and gold nanoparticles

A new Aptasensor to detect Salmonella Typhi Hemolysin E protein utilising a graphene oxide-chitosan modified printed circuit board gold electrode

This study presents the first report of HlyE protein (HlyE) detection utilising an electrochemical aptasensor platform. HlyE is a virulent protein produced by Salmonella enterica serotype Typhi (S. Typhi), responsible for typhoid fever. The aptasensor was developed using the in-house-designed printed circuit board gold electrode, modified with graphene oxide-chitosan nanocomposite via the drop cast technique. This platform was immobilised with a specific HlyE aptamer sequence utilising the carbodiimide crosslinking chemistry. The electrochemical characteristics of the developed aptasensor were analysed using cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy techniques using a benchtop potentiostat. The aptasensor successfully detects the HlyE protein ranging from 1.25 to 20 ng/μL, with a detection limit of 0.137 ng/μL within 30 min under optimal detection conditions. The aptasensor demonstrates excellent specificity, reproducibility and stability up to 14 days at room temperature. A preliminary clinical study indicates that the aptasensor was able to discriminate direct serum samples containing HlyE protein from S. Typhi-infected patients among healthy individuals and patients with other diseases using a portable potentiostat reader. Their detection was comparable with the commercially available Typhidot assay, demonstrating its practicality for early diagnosis of S. Typhi infection. Thus, the aptasensor device developed in this study works efficiently as a portable and rapid diagnostic tool for S. Typhi point-of-care detection.

Electrochemical biosensor based on composite of gold nanoparticle/reduced-graphene oxide/graphitic carbon nitride and a caprolactone polymer for highly sensitive detection of CEA

Carcinoembryonic antigen (CEA) is a broad-spectrum biomarker, and its accurate detection and analysis is important for early clinical diagnosis and treatment. This study aimed to develop a highly sensitive and selective sandwich-type immunosensor based on electrochemical impedance spectroscopy (EIS) for the accurate detection of CEA. A novel composite material, gold nanoparticle/reduced-graphene oxide/graphitic carbon nitride (AuNPs/rGO/g-C3N4), was synthesized with excellent electrical conductivity and a large specific surface area to immobilize biological probes. And ab1-CEA-ab2 formed a sandwich structure of 'antibody-antigen-antibody', which ensured the high selectivity of the biosensor. Furthermore, the introduction of caprolactone polymer (DMPA-PCL) significantly amplifies the impedance signal and improves the sensitivity of the analytical method. Scanning electron microscopy, x-ray diffraction, transmission electron microscopy Fourier transform infrared spectroscopy, and ultraviolet-visible spectrophotometry were used to characterise the prepared AuNPs/rGO/g-C3N4 and DMPA-PCL. Under the optimal conditions, the sensor showed good analytical performance for the detection of CEA with a linear range of 100 fg mL-1-100 ng mL-1 and a detection limit of 83.2 fg mL-1. And the sandwich-type immunosensor showed good selectivity and stability for the recognition of CEA in real samples.

An electrochemical microsensor for osteopontin based on a molecularly imprinted layer and a built-in probe-functionalized acupuncture needle

Osteopontin (OPN) is an important biomarker for reflecting osteoarthritic inflammation and endochondral ossification. In the field of electroanalysis, OPN is a non-electroactive protein, which is usually detected by means of an outer probe or biolabel. Here, a novel microsensor that can directly electroanalyze OPN was constructed by coordinating a surface molecularly imprinted polymer (SMIP) with a built-in electroactive probe of poly(methylene blue) (pMB) on an acupuncture needle microelectrode (ANME). The OPN template can be reversibly anchored using 4-mercaptophenylboronic acid (4-MBPA) via a borate bond between phenylboronic acid and the external cis-diol of the glycoprotein. Methylene blue (MB) and dopamine (DA) were sequentially electropolymerized and grown around templates, which played pivotal roles in the detection signal from the built-in pMB through the imprinted nanocavities. After the recombination of OPN molecules with imprinted nanocavities, the current strength of built-in pMB could be impeded, producing a highly sensitive response. This microsensor shows a linear relationship with the concentration of OPN from 0.01 to 1000 ng mL-1 with a detection limit of 3 pg mL-1. The microsensor also exhibits high selectivity and stability, which is attributed to the recognizing ability of the imprinted nanocavities and the hindrance and anti-interference function of coated polydopamine (pDA). This strategy of preparing a sensor shows practical and scientific significance for functionalizing microelectrodes and constructing microsensors for non-electroactive glycoproteins. In the future, it will be fascinating to integrate this microsensor with the acupuncture technique.

Neurotensin Conjugated Polymeric Porous Microparticles Suppress Inflammation and Improve Angiogenesis Aiding in Diabetic Wound Healing

Neurotensin (NT), a bioactive tridecapeptide aids in diabetic wound healing by modulating inflammation and angiogenesis. However, its rapid degradation in peptidase-rich wound environment (plasma half-life <2 min) limits its efficacy. To address this, neurotensin-conjugated polymeric porous microparticles (NT-PMP) were developed and loaded in gelatin (hydrogel 15% w/v) for topical application, enabling sustained NT release to enhance therapeutic outcomes. NT-PMP exhibited a size range of 60 - 240 µm (mean: 120.63 ± 40.71 µm) and pore size of 5 - 16 µm (average: 10.68 ± 3.47 µm). In vitro studies demonstrated cytocompatibility of NT-PMP in fibroblasts and reduced TNF-α levels in inflammation-induced macrophages (1256 ± 167.02 pg/ml). Further NT-PMP scaffold depicted excellent cell adhesion and migration properties upon seeding of dermal fibroblasts on surface of PMPs. In vivo studies in diabetic wound rat model demonstrated effective wound management, characterized by notable regenerative and healing attributes in the presence of NT-PMP. This included complete re-epithelialization, reducing pro-inflammatory cytokine (TNF-α), and enhancing VEGF expression, ultimately leading to the development of a well-organized collagen matrix in diabetic wounds upon application of NT-PMP gel.Altogether, NT conjugated PMP loaded in hydrogel demonstrated significant regenerative and healing properties, suggesting its potential as an alternative treatment for diabetic wounds.

Ultrasensitive and label-free electrochemical immunosensor using gold nanoparticles deposited on a carbon electrode for the quantification of osteopontin: A serum-based oncomarker

Early detection of cancer biomarkers is crucial for effective diagnosis and treatment, prompting the development of an ultrasensitive label-free electrochemical immunosensor. In this study, we fabricated an ultrasensitive label-free electrochemical immunosensor using a glassy carbon electrode/gold nanoparticles (GCE/AuNPs) modification for quantification of osteopontin (OPN), an oncomarker. The surface features of the modified electrodes were confirmed using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) methods. The electrochemical behavior of the bare and modified electrode was characterized using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The quantification of the OPN antigen was achieved through the differential pulse voltammetry (DPV) method. The fabricated immunosensor demonstrated excellent detection capabilities in both commercial serum samples and phosphate-buffered saline (PBS). It showed sensitive quantification of OPN in the range of 0.001 to 1000 ng/mL with a limit of detection (LOD) of 0.005 ng/mL in PBS. Furthermore, the immunosensor retained approximately 89.3 % of its initial signal after storage for up to 8 weeks. The results were validated by detecting OPN-spiked commercial serum samples with a satisfactory recovery rate. The potential of this immunosensor makes it suitable for assaying OPN in real cancer patient's serum samples with minimal interference from complex sample matrices.

Development of a magnetic α-Fe2O3/Fe3O4 heterogeneous nanorod-based electrochemical biosensing platform for HPV16 E7 oncoprotein detection

The prevention, diagnosis and treatment of cancer have always been the focus of medical research. In this study, a label-free, rapid, simple, sensitive, and specific method for the detection of HPV16 E7 oncoprotein was developed. The electrochemical biosensor platform was constructed by magnetic self-assembly of α-Fe2O3/Fe3O4@Au nanocomposites onto the surface of magnetic glass carbon electrode (MGCE), and the nanocomposite was connected to aptamer through AuS bond to construct a probe to capture HPV16 E7. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were applied to verify the performance of the constructed biosensor. The condition optimization and performance analysis were carried out by differential pulse voltammetry (DPV). Under optimal conditions, the biosensor exhibited a strong linearity between current value and the logarithm of HPV16 E7 oncoprotein concentration in the range of 10 pg/mL - 0.1 μg/mL, with a limit of detection (LOD) of 159 fg/mL and a limit of quantification (LOQ) of 530 fg/mL, and it also revealed excellent reproducibility, long-term stability, and anti-interference ability. In a word, the biosensor would contribute to the early diagnosis of oncoprotein HPV16 E7 and had promising application prospects.

A type of self-assembled and label-free DNA-modified electrochemical biosensors based on magnetic α-Fe2O3/Fe3O4 heterogeneous nanorods for ultra-sensitive detection of CYP2C19*3

CYP2C19*3 enzyme plays a pivotal role in drug metabolism and is tightly regulated by the CYP2C19*3 gene. Therefore, quantification of CYP2C19*3 gene holds paramount importance for achieving personalized medication guidance in precision medicine. In this project, the magnetic electrochemical biosensors were constructed for the ultra-sensitive detection of CYP2C19*3 gene. Employing magnetic α-Fe2O3/Fe3O4@Au as the matrixes for signal amplification, CYP2C19*3 complementary chains (c-ssDNA) were bound to their surfaces through gold-sulfur bonds with subsequent specific sites blockade by bovine serum albumin (BSA) to form the α-Fe2O3/Fe3O4@Au/c-ssDNA/BSA biosensors. This design enabled efficient biosensors separation, target gene capture, and self-assembly on the electrode surface, enhancing the response signal. The biosensors exhibited excellent capture capabilities with a wide linear range (1 pM-1 μM), a low detection limit of 0.2710 pM, a quantitation limit of 0.9033 pM, reproducibility with an RSD value of 1.26 %, and stable storage for at least one week. The RSD value of CYP2C19*3 in serum samples consistently remained below 4.5 %, with a recovery rate ranging 95.52 % from 102.71 %. Moreover, the target gene could be accurately identified and captured in a mixed system of multiple nucleotide mutants of the CYP2C19*3 gene, suggesting a promising applicability and popularization.

Electrochemical biosensing of Acinetobacter baumannii gene using chitosan-gold composite modified electrode

In this study, a novel electrochemical biosensor was developed for the sensitive and selective detection of the Acinetobacter baumannii gene sequence. The biosensor was created by immobilizing a capture probe specific to the A. baumannii gene on the surface of chitosan-gold modified pencil graphite electrodes. Following solid-state hybridization on the Chit-Au/PGE surface, the target DNA sequence of the A. baumannii was detected by measuring the guanine signal using square wave voltammetry (SWV). All experimental parameters impacting sensor response are examined in order to improve hybridization efficacy, and the electrochemical biosensor's performance. The limit of detection (LOD) for the A. baumannii gene sequence was calculated and found to be 1.93 nM. Three different non-complementary DNA sequences were used to evaluate the assay selectivity, but no interference effect was obtained. Additionally, the potential applicability of the biosensor to real samples was tested in artificial serum media. The suggested electrochemical test procedure is simple, approachable, and quick, making it a convenient approach for the screening of DNA sequence.

Optical biosensing of monkeypox virus using novel recombinant silica-binding proteins for site-directed antibody immobilization

The efficient immobilization of capture antibodies is crucial for timely pathogen detection during global pandemic outbreaks. Therefore, we proposed a silica-binding protein featuring core functional domains (cSP). It comprises a peptide with a silica-binding tag designed to adhere to silica surfaces and tandem protein G fragments (2C2) for effective antibody capture. This innovation facilitates precise site-directed immobilization of antibodies onto silica surfaces. We applied cSP to silica-coated optical fibers, creating a fiber-optic biolayer interferometer (FO-BLI) biosensor capable of monitoring the monkeypox virus (MPXV) protein A29L in spiked clinical samples to rapidly detect the MPXV. The cSP-based FO-BLI biosensor for MPXV demonstrated a limit of detection (LOD) of 0.62 ng/mL in buffer, comparable to the 0.52 ng/mL LOD achieved using a conventional streptavidin (SA)-based FO-BLI biosensor. Furthermore, it achieved LODs of 0.77 ng/mL in spiked serum and 0.80 ng/mL in spiked saliva, exhibiting no cross-reactivity with other viral antigens. The MPXV detection process was completed within 14 min. We further proposed a cSP-based multi-virus biosensor strategy capable of detecting various pandemic strains, such as MPXV, the latest coronavirus disease (COVID) variants, and influenza A protein, to extend its versatility. The proposed cSP-modified FO-BLI biosensor has a high potential for rapidly and accurately detecting MPXV antigens, making valuable contributions to epidemiological studies.

Copper(II)-Tannic Acid@Cu with In Situ Grown Gold Nanoparticles as a Bifunctional Matrix for Facile Construction of Label-Free and Ultrasensitive Electrochemical cTnI Immunosensor

Sensitive detection of cardiac troponin I (cTnI) is of great significance in the diagnosis of a fatal acute myocardial infarction. A redox-active nanocomposite of copper(II)-tannic acid@Cu (CuTA@Cu) was herein prepared on the surface of a glassy carbon electrode by electrochemical deposition of metallic copper combined with a metal stripping strategy. Then, HAuCl4 was in situ reduced to gold nanoparticles (AuNPs) by strong reductive catechol groups in the TA ligand. The AuNPs/CuTA@Cu composite was further utilized as a bifunctional matrix for the immobilization of the cTnI antibody (anti-cTnI), producing an electrochemical immunosensor. Electrochemical tests show that the immunoreaction between anti-cTnI and target cTnI can cause a significant reduction of the electrochemical signal of CuTA@Cu. It can be attributed to the insulating characteristic of the immunocomplex and its barrier effect to the electrolyte ion diffusion. From the signal changes of CuTA@Cu, cTnI can be analyzed in a wide range from 10 fg mL-1 to 10 ng mL-1, with an ultralow detection limit of 0.65 fg mL-1. The spiked recovery assays show that the immunosensor is reliable for cTnI determination in human serum samples, demonstrating its promising application in the early clinical diagnosis of myocardial infarction.

Phage tailspike protein coated gold nanoparticles combined with smartphone for rapid bacterial detection and photothermal sterilization

The integration of recognition and therapeutic functions in multifunctional biosensors is of great importance in guaranteeing food security and reducing the occurrence of foodborne illness caused by foodborne pathogens. In this study, a biosensor utilizing a "sense-and-treat" approach was developed by integrating phage tailspike protein (TSP) with gold nanoparticles (AuNPs@TSP). The synthesized AuNPs@TSP showed strong binding affinity towards Salmonella typhimurium causing color changes and exhibited effective bactericidal activity when exposed to near-infrared (NIR) irradiation. This biosensor facilitated rapid colorimetric detection of S. typhimurium in 50 min, with a LOD (limit of detection) of 2.53 × 103 CFU/mL output on a smartphone APP after analyzing the red-green-blue (RGB) values from color rendering results. Furthermore, the biosensor displayed high selectivity, rapid response time, and broad applicability when tested with real samples. Moreover, the biosensor exhibited a remarkably efficient antibacterial efficacy of 100 % against S. typhimurium under 808 nm light irradiation for 6 min. This study provides a comprehensive investigation into the potential utilization of biosensors for rapid detection and eradication of foodborne pathogens in food industry.

Innovations in Biosensor Technologies for Healthcare Diagnostics and Therapeutic Drug Monitoring: Applications, Recent Progress, and Future Research Challenges

This comprehensive review delves into the forefront of biosensor technologies and their critical roles in disease biomarker detection and therapeutic drug monitoring. It provides an in-depth analysis of various biosensor types and applications, including enzymatic sensors, immunosensors, and DNA sensors, elucidating their mechanisms and specific healthcare applications. The review highlights recent innovations such as integrating nanotechnology, developing wearable devices, and trends in miniaturisation, showcasing their transformative potential in healthcare. In addition, it addresses significant sensitivity, specificity, reproducibility, and data security challenges, proposing strategic solutions to overcome these obstacles. It is envisaged that it will inform strategic decision-making, drive technological innovation, and enhance global healthcare outcomes by synthesising multidisciplinary insights.

An affordable label-free ultrasensitive immunosensor based on gold nanoparticles deposited on glassy carbon electrode for the transferrin receptor detection

In recent decades, there has been a concerning and consistent rise in the incidence of cancer, posing a significant threat to human health and overall quality of life. The transferrin receptor (TfR) is one of the most crucial protein biomarkers observed to be overexpressed in various cancers. This study reports on the development of a novel voltammetric immunosensor for TfR detection. The electrochemical platform was made up of a glassy carbon electrode (GCE) functionalized with gold nanoparticles (AuNPs), on which anti-TfR was immobilized. The surface characteristics and electrochemical behaviors of the modified electrodes were comprehensively investigated through scanning electron microscopy, XPS, Raman spectroscopy FT-IR, electrochemical cyclic voltammetry and impedance spectroscopy. The developed immunosensor exhibited robust analytical performance with TfR fortified buffer solution, showing a linear range (LR) response from 0.01 to 3000 μg/mL, with a limit of detection (LOD) of 0.01 μg/mL and reproducibility (RSD <4 %). The fabricated sensor demonstrated high reproducibility and selectivity when subjected to testing with various types of interfering proteins. The immunosensor designed for TfR detection demonstrated several advantageous features, such as being cost-effective and requiring a small volume of test sample making it highly suitable for point-of-care applications.

Molecularly imprinted polymer-based SERS sensing of transferrin in human serum

Specific detection of glycoproteins such as transferrin (TRF) related to neurological diseases, hepatoma and other diseases always plays an important role in the field of disease diagnosis. We designed an antibody-free immunoassay sensing method based on molecularly imprinted polymers (MIPs) formed by the polymerization of multiple functional monomers for the sensitive and selective detection of TRF in human serum. In the sandwich surface-enhanced Raman spectroscopy (SERS) sensor, the TRF-oriented magnetic MIP nanoparticles (Fe3O4@SiO2-MIPs) served as capture units to specifically recognize TRF and 4-mercaptophenylboronic acid-functionalized gold nanorods (MPBA-Au NRs) served as SERS probes to label the targets. In order to achieve stronger interaction between the recognition cavities of the prepared MIPs and the different amino acid fragments that make up TRF, Fe3O4@SiO2-MIPs were obtained through polycondensation reactions between more silylating reagents, enhancing the specific recognition of the entire TRF protein and achieving high IF. This sensing method exhibited a good linear response to TRF within the TRF concentration range of 0.01 ng mL-1 to 1 mg mL-1 (R2 = 0.9974), and the LOD was 0.00407 ng mL-1 (S/N = 3). The good stability, reproducibility and specificity of the resulting MIP based SERS sensor were demonstrated. The determination of TRF in human serum confirmed the feasibility of the method in practical applications.

Fabrication of an affordable and sensitive corticosteroid-binding globulin immunosensor based on electrodeposited gold nanoparticles modified glassy carbon electrode

Herein, we fabricated an ultrasensitive electrochemical immunosensor for the quantitative detection of corticosteroid-binding globulin (CBG). CBG is a protein that regulates glucocorticoid levels and is an important biomarker for inflammation. A decrease in CBG levels is a key biomarker for inflammatory diseases, such as septic shock. To enhance the electrochemical performance and provide a large surface area for anti-CBG immobilization, we functionalized the glassy carbon electrode surface with AuNPs. Electrochemical characterization methods including cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to examine the construction of the fabricated immunosensor. The electrochemical signal demonstrated a remarkable sensitivity to the CBG antigen, with a detection range from 0.01 to 100 μg/mL and a limit of detection of 0.012 μg/mL, making it suitable for both clinical and research applications. This label-free immunosensor offers significant advantages, including high sensitivity, low detection limits and excellent selectivity, making it a promising tool for detecting CBG in complex biological samples. Its potential applications include early disease diagnosis, treatment monitoring and studying CBG-related physiological processes.

A novel nanoliposome model platform mimicking SARS-CoV-2 as a bioreceptor to dissect the amperometric response in biosensor applications

In this study, we proposed to investigate the response of an electrochemical-based immunosensor via nanoliposomes carrying the SARS-CoV-2 Spike-S1 protein. In this regard, we prepared RNA encapsulated nanoliposome functionalized with a specific SARS-CoV-2 Spike-S1 protein as a SARS-CoV-2 model. Then, this new nanoliposome mimicking SARS-CoV-2 was used as the bio-recognizing agent of an immunosensor developed to detect the SARS-CoV-2 within the scope of the study. The working electrode of the immunosensor was coated with chitosan polymer, decorated with SARS-CoV-2 Spike antibody, to achieve antibody-antigen matching on the electrode surface. SARS-CoV-2 mimicking nanoliposomes at various concentrations was used to achieve an amperometric response and the analytical parameters of the sensor were calculated from the relationship between the immunosensor's current values depending on the number of these matches with regard to varying antigen concentrations. Linear measurement range, LOD and measurement sensitivity were calculated as 53 pM-8 nM, 3.79 pM and 55.47 μA nM-1 cm-2, respectively. The standard deviation of the same measurements in the developed immunosensor was 0.33 %.

Synthesis of carbon nanotubes-chitosan nanocomposite and immunosensor fabrication for myoglobin detection: An acute myocardial infarction biomarker

The use of single-walled carbon nanotubes (SWCNTs) in biomedical applications is limited due to their inability to disperse in aqueous solutions. In this study, dispersed -COOH functionalized CNTs with N-succinylated chitosan (CS), greatly increasing the water solubility of CNTs and forming a uniformly dispersed nanocomposite solution of CNTs@CS. Coupling reagent EDC/NHS was used as a linker with the -COOH groups present on the N-succinylated chitosan which significantly improved the affinity of the CNTs for biomolecules. Myoglobin (Mb) is a promising biomarker for the precise assessment of cardiovascular risk, type 2 diabetes, metabolic syndrome, hypertension and several types of cancer. A high level of Mb can be used to diagnose the mentioned pathogenic diseases. The CNTs@CS-FET demonstrates superior sensing performance for Mb antigen fortified in buffer, with a wide linear range of 1 to 4000 ng/mL. The detection limit of the developed Mb immunosensor was estimated to be 4.2 ng/mL. The novel CNTs@CS-FET immunosensor demonstrates remarkable capability in detecting Mb without being affected by interferences from nonspecific antigens. Mb spiked serum showed a recovery rate of 100.262 to 118.55 % indicating great promise for Mb detection in clinical samples. The experimental results confirmed that the CNTs@CS-FET immunosensor had excellent selectivity, reproducibility and storage stability.