Label-free Electrochemical Biosensor Research Articles

Electrochemical Biosensing Strategy for Ultrasensitive Detection of Aquaporin-4 Antibody as Neuromyelitis Optica Autoimmune Disease Biomarker Using Aquaporin-4 Extracellular Loop

Neuromyelitis optica (NMO) is a severe and disabling neurodegenerative disorder of the central nervous system (CNS). Neuromyelitis optica-Immunoglobulin G (NMO-IgG) is a serum IgG autoantibody almost exclusively present in NMO patients, which helps to differentiate NMO from other CNS disorders. Developing standardized and user-friendly assays remains a significant challenge in making NMO-IgG testing widely available. Label-free methods are simpler and faster, without additional reagents and procedures. Here, we present a peptide-based label-free electrochemical biosensor for detecting aquaporin-4 antibodies (AQP4-Abs) using extracellular AQP4 to diagnose NMO disease via the DPV electrochemical method. We have developed a novel approach in which the E loop of extracellular AQP4 is bemployed to detect NMO. 3 phenylalanines (Phe) were annexed to the C terminal, and because phenylalanine has a benzene ring, it can have π-π interaction with the benzene ring of carbon nanotube (CNT). In the designated platform, instead of using functional groups with complex and multi-step processes for immobilizing on the electrode surface, we used Nickel-Metal−organic framework /CNT as a novel modifier for measuring AQP4 antibodies with a simple, cheap, and accessible synthesis method. The developed sensor can detect antibodies with detection limit and quantification of 6.2 and 10.0 pg ml−1, respectively (S/N = 3). Also, superb sensitivity of the biosensor was attained as 28.8 μA mL ng−1 cm−2, confirming that the sensor has great potential for clinical application as a diagnostic test.

Electrochemical genosensor based on RNA-responsive human telomeric G-quadruplex DNA: A proof-of-concept with SARS-CoV-2 RNA

In this report, a facile and label-free electrochemical RNA biosensor is developed by exploiting methylene blue (MB) as an electroactive positive ligand of G-quadruplex. The electrochemical response mechanism of the nucleic acid assay was based on the change in differential pulse voltammetry (DPV) signal of adsorbed MB on the immobilized human telomeric G-quadruplex DNA with a loop that is complementary to the target RNA. Hybridization between synthetic positive control RNA and G-quadruplex DNA probe on the transducer platform rendered a conformational change of G-quadruplex to double-stranded DNA (dsDNA), and increased the redox current of cationic MB π planar ligand at the sensing interface, thereby the electrochemical signal of the MB-adsorbed duplex is proportional to the concentration of target RNA, with SARS-CoV-2 (COVID-19) RNA as the model. Under optimal conditions, the target RNA can be detected in a linear range from 1 zM to 1 μM with a limit of detection (LOD) obtained at 0.59 zM for synthetic target RNA and as low as 1.4 copy number for positive control plasmid. This genosensor exhibited high selectivity towards SARS-CoV-2 RNA over other RNA nucleotides, such as SARS-CoV and MERS-CoV. The electrochemical RNA biosensor showed DPV signal, which was proportional to the 2019-nCoV_N_positive control plasmid from 2 to 200000 copies (R2 = 0.978). A good correlation between the genosensor and qRT-PCR gold standard was attained for the detection of SARS-CoV-2 RNA in terms of viral copy number in clinical samples from upper respiratory specimens.

Magnetic self-assembled label-free electrochemical biosensor based on Fe3O4/α-Fe2O3 heterogeneous nanosheets for the detection of Tau proteins

A type of electrochemical biosensors based on magnetic Fe3O4/α-Fe2O3 heterogeneous nanosheets was constructed to detect Tau proteins for early diagnosis and intervention therapy of Alzheimer's disease (AD). Firstly, Fe3O4/α-Fe2O3 heterogeneous nanosheets were fabricated as the substrate to realize magnetic self-assembly and magnetic separation to improve current response, and Fe3O4/α-Fe2O3@Au-Apt/ssDNA/MCH biosensors were successfully constructed through the reduction process of chloroauric acid, the immobilizations of aptamer (Apt) and ssDNA, and the intercept process of 6-Mercapto-1-hexanol (MCH); the construction process of the electrochemical biosensor was monitored using Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), and the factors affecting the current response of this sensor (concentration of Fe3O4/α-Fe2O3@Au and Apt/ssDNA, incubation temperature and time of Tau) were explored and optimized using differential pulse voltammetry (DPV). Analyzing the performance of this sensor under optimal conditions, the linear range was finally obtained to be 0.1 pg/mL–10 ng/mL, the limit of detection (LOD) was 0.08 pg/mL, and the limit of quantification (LOQ) was 0.28 pg/mL. The selectivity, reproducibility and stability of the biosensors were further investigated, and in a really sample analysis using human serum, the recoveries were obtained in the range of 93.93 %–107.39 %, with RSD ranging from 1.05 % to 1.94 %.

A trivalent aptasensor by using DNA tetrahedron as scaffold for label-free determination of antibiotics

Owing to advantage in high sensitivity and fast response, aptamer based electrochemical biosensors have attracted much more attention. However, inappropriate interfacial engineering strategy leads to poor recognition performance, which ascribe to the following factors of immobilized oligonucleotide strand including steric hindrance, interchain entanglement, and unfavorable conformation. In this work, we proposed a DNA tetrahedron based diblock aptamer immobilized strategy for the construction of label-free electrochemical biosensor. The diblock aptamer sequence is composite of T-rich anchor domain and recognition domain, where T-rich domain enabling anchored on the edge of DNA tetrahedron via Hoogsteen hydrogen bond at neutral condition. The DNA tetrahedron scaffold offers an appropriate lateral space for target recognition of diblock aptamer. More importantly, this trivalent aptamer recognition interface can be regenerated by simply adjusting the pH environment to alkaline, resulting in the dissociation of diblock aptamer. Under the optimum condition, proposed electrochemical aptasensor manifested a satisfied sensitivity for aminoglycosides antibiotic, kanamycin with a limit of detection of 0.69 nM, which is 45-fold lower than traditional Au–S immobilization strategy. Moreover, the proposed aptasensor had also successfully been extended to ampicillin detection by changing the sequence of recognition domain in diblock aptamer. This work paves a new way for the rational design of aptamer-based electrochemical sensor.

Label-free electrochemical biosensor for direct detection of Oncostatin M (OSM) inflammatory bowel diseases (IBD) biomarker in human serum

Oncostatin M (OSM) is an interleukin-6 (IL-6) member family cytokine implicated in the pathogenesis of chronic diseases including inflammatory bowel disease (IBD). OSM is a novel diagnostic biomarker over-expressed in the serum of IBD patients. This paper reports on the first electrochemical OSM immunosensor, developed using a multistep fabrication process aimed at covalently immobilizing OSM antibodies on a mixed self-assembled monolayer coated gold working electrode. Cyclic voltammetry, atomic force microscopy (AFM), IR spectroscopy and optical characterizations were used to validate the sensor functionalization protocol. Electrochemical impedance spectroscopy (EIS) measurements were performed to assess the reliability of the immunosensor preparation and to verify the antibody-antigen complexes formation. The label-free immunosensor showed high sensitivity identifying OSM at clinically relevant concentrations (37–1000 pg mL−1) with low detection limit of 2.86 pg mL−1. Both sensitivity and selectivity of the proposed immunosensor were also demonstrated in human serum in the presence of interfering biomarkers, making it an innovative potential platform for the OSM biomarker detection in IBD patients’ serum.

Label-free Electrochemical Nanobiosensors Using Au-SPE for COVID-19 Detection: A Comparative Review of Different Biomarkers and Recognition Elements

Abstract: An immediate and precise diagnosis is required due to the COVID-19 outbreak. Labelfree electrochemical biosensors show promise as potentially valuable instruments for detecting COVID-19. These biosensors are distinguished by their lack of complexity, high speed, sensitivity, and relatively low cost. The precise COVID-19 biomarkers may be recognized without labeling or amplification by detecting the electrical signal created by direct contact between the target analyte and the identification element positioned on the electrode surface. This can be done by placing the electrode in contact with the target analyte, which will amplify the signal. It has been shown that using gold screen printed electrodes, also known as Au SPE, is beneficial when used as an electrode material in label-free electrochemical biosensors. This review study examines and contrasts the performance of several label-free electrochemical biosensors that use Au SPE to detect COVID-19. The merits and limitations of each biosensor will also be discussed. These biosensors use recognition components like DNA, RNA, antibody, aptamer, and MIP and depend on various indicators, such as viral RNA, viral protein, and host antibody. In addition, an analysis of the difficulties and possibilities that may present within this burgeoning subject is carried out. This includes the enhancement of sensor selectivity and stability, optimizing sensor manufacture and design, integrating the sensor with portable readout equipment, and validating the sensor's effectiveness via the use of genuine clinical samples. It can be reasoned out that label-free electrochemical biosensors that make use of gold screen-printed electrodes (Au SPE) have a significant amount of potential for the detection of COVID-19. However, further study is required to address various difficulties, improve their dependability, and broaden the range of applications for these technologies.

Construction of a label-free electrochemical biosensing system utilizing Fe3O4/α-Fe2O3@Au with magnetic-induced self-assembly for the detection of EGFR glycoprotein

A label-free electrochemical biosensing system was developed for the sensitive detection of epidermal growth factor receptor (EGFR), which was frequently overexpressed in lung cancer, breast cancer, and glioblastoma. Magnetic Fe3O4/α-Fe2O3@Au nanocomposites were utilized as the signal amplifiers and for the immobilization matrix of specific probes (ssDNA-APT) in the biosensors. The Fe3O4/α-Fe2O3@Au/ssDNA-APT biosensors were formed through Au–S binding on this matrix and were immobilized onto a magnetic glassy carbon electrode (MGCE) using magnetic-induced self-assembly. The performance of the EGFR detection system was verified using differential pulse voltammetry (DPV). The system exhibited a wide linear range from 0.1 ng/mL to 1000 ng/mL (R2 = 0.9947), with a limit of detection (LOD) of 0.18 ng/mL. Furthermore, the repeatability, stability, selectivity, and ability for real sample analysis were investigated. With its simplicity and reliability, this biosensing system has the potential to be developed as a valuable tool in clinical EGFR detection, offering a promising candidate for point-of-care (POC) testing.

A label-free and ultrasensitive electrochemical biosensor using hybrid polypyrrole/gold nanoelectrocatalyst mediated signal amplification for the detection of miRNA-21.

The quantitative detection of microRNAs (miRNAs) is crucial for the diagnosis of cancers, while the traditional methods involve complicated procedures and restricted signal gain. In this study, we have established an ultrasensitive electrochemical biosensor by combining a target-induced hybridization reaction and signal amplification strategy for the detection of miRNA-21. The signal amplification is achieved through employing double-stranded DNA as scaffolds for methylene blue (MB) and using a polypyrrole@gold nanocomposite (ppy@AuNPs) as the electrochemical catalyst for further enhancing the signal. Therefore, this proposed electrochemical platform displayed an analytical performance with a wide linear range from 10 fM to 100 nM and a low detection limit down to 5.4 fM. The excellent selectivity allows the biosensor to discriminate miRNA-21 from other miRNAs, even the one base-mismatched sequence. Moreover, this nanoelectrocatalyst-based platform exhibited good reproducibility and remarkable storage stability, which shows great potential for miRNA-21 detection.

A portable label-free electrochemical DNA biosensor for rapid detection of Salmonella Typhi.

A highly accurate, rapid, portable, and robust platform for detecting Salmonella enterica serovar Typhi (S. Typhi) is crucial for early-stage diagnosis of typhoid to avert and control the outbreaks of this pathogen, which threaten global public health. This study presents a proof-of-concept for our developed label-free electrochemical DNA biosensor system for S. Typhi detection, which employs a printed circuit board gold electrode (PCBGE), integrated with a portable potentiostat reader. Initially, the functionalized DNA biosensor and target detection were characterized using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) methods using a benchtop potentiostat. Interestingly, the newly developed DNA biosensor can identify target single-stranded DNA concentrations ranging from 10 nM to 20 μM, achieving a detection limit of 7.6 nM within a brief 5 minute timeframe. Under optimal detection conditions, the DNA biosensor exhibits remarkable selectivity, capable of distinguishing a single mismatch base pair from the target single-stranded DNA sequence. We then evaluated the feasibility of the developed DNA biosensor system as a diagnostic tool by detecting S. Typhi in 50 clinical samples using a portable potentiostat reader based on the DPV technique. Remarkably, the developed biosensor can distinctly distinguish between positive and negative samples, indicating that the miniaturised DNA biosensor system is practical for detecting S. Typhi in real biological samples. The developed DNA biosensor device in this work proves to be a promising point-of-care (POC) device for Salmonella detection due to its swift detection time, uncomplicated design, and streamlined workflow detection system.

A label-free electrochemical biosensor based on a bimetallic organic framework for the detection of carbohydrate antigen 19-9.

Carbohydrate antigen 19-9 (CA19-9) is an important marker for pancreatic cancer, ovarian cancer and other tumors, and its rapid and stable detection is the basis for early diagnosis and treatment. In this paper, a label-free electrochemical immunosensor for the sensitive detection of CA19-9 has been developed. First, the synthesis of two novel core-shell bimetallic nanomaterials, namely Ce-MOF-on-Fe-MOF and Fe-MOF-on-Ce-MOF, was accomplished using the MOF-on-MOF approach. The poor electrical conductivity of MOF materials was addressed by incorporating polyethylenimide (PEI) functionalized rGO with Ce-MOF-on-Fe-MOF and Fe-MOF-on-Ce-MOF nanomaterials. Simultaneously, toluidine blue (Tb) was employed as a redox probe and physically adsorbed onto the synthesized materials, resulting in the formation of two nanomaterials: rGO@Ce-MOF-on-Fe-MOF@Tb and rGO@Fe-MOF-on-Ce-MOF@Tb. The fundamental characterization reveals that the sensing performance of the rGO@Ce-MOF-on-Fe-MOF@TB-based immune sensor surpasses that of the rGO@Fe-MOF-on-Ce-MOF@TB-based immune sensor, which is attributed to the fact that, unlike the interlayer-constrained structure of Fe-MOF-on-Ce-MOF, in Ce-MOF-on-Fe-MOF, Ce-MOF penetrates into Fe-MOF to form a heterogeneous structure due to the relatively large pore size of Fe-MOF, which better combines the excellent biocompatibility and strong anchoring effect of Fe MOFs on antibodies, as well as the high electrochemical activity and conductivity of Ce-MOF, to enhance sensing performance. The proposed label-free immunosensor based on rGO@Ce-MOF-on-Fe-MOF@Tb has a wide linear range (1-100 000 mU mL-1), a low detection limit (0.34 mU mL-1), good stability, reproducibility, and repeatability, and satisfactory applicability, which provides a potential platform for clinical applications.

Faradaic Impedimetric Immunosensor for Label-Free Point-of-Care Detection of COVID-19 Antibodies Using Gold-Interdigitated Electrode Array.

Label-free electrochemical biosensors have many desirable characteristics in terms of miniaturization, scalability, digitization, and other attributes associated with point-of-care (POC) applications. In the era of COVID-19 and pandemic preparedness, further development of such biosensors will be immensely beneficial for rapid testing and disease management. Label-free electrochemical biosensors often employ [Fe(CN)6]-3/4 redox probes to detect low-concentration target analytes as they dramatically enhance sensitivity. However, such Faradaic-based sensors are reported to experience baseline signal drift, which compromises the performance of these devices. Here, we describe the use of a mecaptohexanoic (MHA) self-assembled monolayer (SAM) modified Au-interdigitated electrode arrays (IDA) to investigate the origin of the baseline signal drift, developed a protocol to resolve the issue, and presented insights into the underlying mechanism on the working of label-free electrochemical biosensors. Using this protocol, we demonstrate the application of MHA SAM-modified Au-IDA for POC analysis of human serum samples. We describe the use of a label-free electrochemical biosensor based on covalently conjugated SARS-CoV-2 spike protein for POC detection of COVID-19 antibodies. The test requires a short incubation time (10 min), and has a sensitivity of 35.4/decade (35.4%/10 ng mL-1) and LOD of 21 ng/mL. Negligible cross reactivity to seasonal human coronavirus or other endogenous antibodies was observed. Our studies also show that Faradaic biosensors are ~17 times more sensitive than non-Faradaic biosensors. We believe the work presented here contributes to the fundamental understanding of the underlying mechanisms of baseline signal drift and will be applicable to future development of electrochemical biosensors for POC applications.

A label-free electrochemical biosensor based on PBA-Au-MXene QD for miR-122 detection in serum samples.

Apoly(n-butyl acrylate)-gold-MXene quantum dots (PBA-Au-MXene QD) nanocomposite-based biosensor is presentedthat is modified by unique antisense single-stranded DNA (ssDNA) and uses the electrochemical detection methods of DPV, CV, and EIS to early detect miR-122 as a breast cancer biomarker in real clinical samples. This fabrication method is based on advanced nanotechnology, at which a poly(n-butyl acrylate) (PBA) as a non-conductive polymer transforms into a conductive composite by incorporating Au-MXene QD. This biosensor had a limit of detection (LOD) of 0.8 zM and a linear range from 0.001 aM to 1000 nM, making it capable of detecting the low concentrations of miR-122 in patient samples. Moreover, it allows approximately 100% sensitivity and 100% specificity for miR-122 without extraction. The synthesis and detection characteristics were evaluated by different complementary tests such as AFM, FTIR, TEM, and FESEM. This new biosensor can have a high potential in clinical applications to detect breast cancer early and hence improve patient outcomes.

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

In this study, we developed a label-free and ultrasensitive electrochemical biosensor for the detection of transferrin (Tf), an important serum biomarker of atransferrinemia. The biosensor was fabricated by using glassy carbon electrode (GCE) and modified with gold nanoparticles (AuNPs) via electroless deposition. The electrochemical characteristics of the GCE-AuNPs biosensors were characterized using cyclic voltammetry and electrochemical impedance spectroscopy analysis. Differential pulse voltammetry was used for quantitative evaluation of the Tf-antigen by recording the increase in the anodic peak current of GCE-AuNPs biosensor. The GCE-AuNPs biosensor demonstrates superior sensing performance for Tf-antigen fortified in buffer, with a wide linear range of 0.1 to 5000 μg/mL and a limit of detection of 0.18 μg/mL. The studied GCE-AuNPs biosensor showed excellent sensitivity, selectivity, long-term storage stability and simple sensing steps without pretreatment of clinical samples. This GCE-AuNPs biosensor indicates great potential for developing a Tf detection platform, which would be helpful in the early diagnosis of atransferrinemia. The developed GCE-AuNPs biosensor holds great potential in biomedical research related to point of care for the early diagnosis and monitoring of diseases associated with aberrant serum transferrin levels. These findings suggest that the GCE-AuNPs biosensor has great potential for detecting other serum biomarkers.

Label-free electrochemical biosensor based on Ng-PCL polymer signal amplification for the detection of carcinoembryonic antigen

Carcinoembryonic antigen (CEA) is the related antigen first extracted from embryonic tissue and is an acidic glycoprotein with human embryonic antigenic properties. It is an important biomarker for the detection of many malignancies. In this paper, we have developed a signal amplified sandwich-type electrochemical impedance biosensor based on naringin initiated poly(ε-caprolactone) (Ng-PCL) polymer for highly sensitive and rapid determination of CEA. The polymer Ng-PCL is a macromolecular polymer that can increase the sensitivity of biosensor. First, SH-functionalized CEA-aptamer 1 (Apt1) was attached to the electrode surface as a recognition probe by Au-S bonds in order to form a self-assembly monolayer (SAM). Then, the one end of CEA antigen could recognize the Apt1 modified on the electrode surface, the other end could recognize the COOH-functionalized CEA-aptamer 2 (Apt2) forming a sandwich structure. Finally, polymer Ng-PCL as a signal amplification unit, which was connected to Apt2 by ester bonds. As a result, the electron transfer in the electrode interface was hindered effectively and a label-free electrochemical impedance sensor was constructed successfully. The high sensitivity and selectivity of biosensor relied on the SAM, polymer Ng-PCL, and specific recognition of CEA. Under the optimum experimental conditions, we proposed electrochemical impedance biosensor had wide detection range between 5 pg/mL and 200 ng/mL, and the sensitivity can reach 0.675 pg/mL. Moreover, the electrochemical impedance biosensor performed high specificity, good stability and satisfactory reproducibility as well. Thus, this strategy will provide new path for the detection of other biomarkers in early clinical diagnosis.

Octahedral Cu2O nanomaterials as electrochemical aptasensor for sensitive detection of tetracycline in milk

In this work, A novel label-free electrochemical biosensor based on octahedral Cu2O @ Au nanocomposites was developed for the detection of tetracycline. The gold nanoparticles (AuNPs) on the surface of Cu2O nanomaterials not only improve the electrochemical performance, but also can be used as a binding site for thiol-modified tetracycline aptamers, which can specifically bind to tetracycline. Cu2O @ Au nanocomposites provide a synergistic effect of electrochemical signal amplification and tetracycline recognition strategy. Under the optimal conditions, the proposed biosensor exhibited different electrochemical reactions for different concentrations of tetracycline, with a linear range of 1 nM-1000 μM and a detection limit of 0.16 nM. This work provides a new idea for rapid and sensitive detection of tetracycline by using a simple and economical tetracycline aptamer combined with Cu2O @ Au biosensor platform.

Aptamer-based label-free electrochemical biosensors for the diagnosis of sickle cell anemia

Sickle cell Anemia (SCA) is a widespread disease that causes hemolysis of blood cells, anemia, painful episodes, organ damage, and in some cases death. Early diagnosis of sickle cell anemia is significantly useful to reduce the mortality rate and manage the disease effectively. Here, we report the selection and characterization of specific aptamers against hemoglobin A (HbA) and hemoglobin S (HbS) and their integration into the electrochemical sensing platforms. The aptamers which have the highest binding affinities toward HbA and HbS are HbA17 and HbS 4 with dissociation constants of 13.5 and 57.5 nM, respectively. Thiol-modified aptamers were immobilized on screen-printed gold electrodes (Au-SPE) and used for the label-free detection of HbA and HbS using square wave voltammetry. The voltammetric aptasensors showed high selectivity and specificity toward HbA and HbS. A cross-reactivity tests were performed showing no response when the aptasensors were incubated with the nonspecific hemoglobin. This method enabled the detection of HbA and HbS in human whole blood showing good agreement with the electrophoresis method. This suggests a great promise of this platform for differentiating between healthy individuals (HbAA), patients with sickle-cell disease (HbSS) and carriers (HbAS).

A label-free electrochemical biosensor for the detection of alpha-thalassemia 1 (SEA deletion) carriers using screen-printed carbon electrodes

A label-free electrochemical DNA biosensor based on electrochemical impedance spectroscopy (EIS) biosensor has been extensively developed for diagnosing human genetic diseases. However, its application has been limited to simulated target DNA. The aim of this study was to develop an EIS biosensor that can identify carriers of alpha (α)-thalassemia 1 with Southeast Asia (SEA) deletion. The biosensor was coupled with screen-printed carbon electrodes (SPCEs) and Hoechst 33,258 dye. To determine the optimal conditions and cutoff criteria, we evaluated forty samples with known DNA genotypes. Our findings suggested that the cutoff value for identifying α-thalassemia 1 (SEA deletion) carriers was more than 26.84 kΩ of negative imaginary impedance (-Z″) and 48.83 kΩ of charge transfer resistance (Rct). The sensitivity of the developed EIS biosensor was comparable to that of conventional gel electrophoresis, with no cross-reactivity observed in α-thalassemia 1 (THAI deletion), α-thalassemia 2 (3.7 deletion), α-thalassemia 2 (4.2 deletion), and beta (β)-thalassemia carriers. The diagnostic potential of the developed EIS biosensor was evaluated using 81 clinical blood samples, demonstrating 100% sensitivity, 88.2% specificity, 83.3% positive predictive value (PPV), 100% negative predictive value (NPV) and 92.6% accuracy for Rct measurement. The developed EIS biosensor presents an attractive screening method for the detecting α-thalassemia 1 (SEA deletion) carriers due to its simplicity, cost-effectiveness, and 45-fold reduction in turnaround time compared to conventional gel electrophoresis. Consequently, the identification of α-thalassemia 1 (SEA deletion) carrier through this approach represents the most effective strategy for the management and prevention of the most severe form of thalassemia.

2D vanadium disulfide nanosheets assisted ultrasensitive, rapid, and label-free electrochemical quantification of cancer biomarker (MMP-2)

Cancer is one of the most tormenting global health burdens reporting high mortality and morbidity worldwide. Matrix metalloproteinase 2 (MMP-2) protein has elevated expression for most types of cancers, including prostate and breast cancer. Therefore, accurate and specific detection of MMP-2 biomarker is crucial for screening, treatment, and prognosis of related cancer. In this work, we have proposed a label-free electrochemical biosensor for the detection of MMP-2 protein. This biosensor was fabricated using hydrothermally synthesized vanadium disulfide (VS2) nanosheets with monoclonal anti-MMP2 antibodies biofunctionalized using a suitable linker. The VS2 nanomaterials were synthesized hydrothermally at different reaction temperatures (140 °C, 160 °C, 180 °C and 200 °C) generating different morphologies from a 3D bulk cubic structure at 140 °C to 2D nanosheets at 200 °C. Owing to the advantages of 2D VS2 nanosheets with high surface-to-volume ratio, excellent electrochemical response and high antibody loading possibility, it was selected for fabricating an MMP-2 specific biosensor. The antibody–antigen binding event is analyzed by recording electrochemical impedance spectroscopy signals for different target MMP-2 protein concentrations. The sensitivity and lower limit of detection were 7.272 (ΔR/R)(ng ml)−1 cm−2 and 0.138 fg ml−1, respectively in 10 mM phosphate buffer saline for this proposed sensor. Further, interference studies were also performed which demonstrates the sensor to be highly selective against non-specific target proteins. This 2D VS2 nanosheet-based electrochemical biosensor is a sensitive, cost-effective, accurate, and selective solution for cancer diagnosis.

Label-free electrochemical biosensor with magnetically induced self-assembly for the detection of cancer antigen 125

Magnetically induced self-assembly technology was used to construct a label-free electrochemical biosensor based on magnetic Mg0.5Cu0.5Fe2O4-Au nanocomposites for the sensitive detection of cancer antigen 125 (CA125). To aim for this, Mg0.5Cu0.5Fe2O4 nanoparticles were first prepared via the rapid combustion process. The average diameter of the nanoparticles calcined at 800 °C with the absolute ethanol volume of 20 mL was about 169.3 nm. Then Au was used for the surface modification by NaBH4 reduction reaction approach. The magnetic glassy carbon electrode (MGCE) was modified by Mg0.5Cu0.5Fe2O4-Au via a magnetic induction self-assembly process. The reduced thiol-modified single-stranded DNA was attached to the Mg0.5Cu0.5Fe2O4-Au nanocomposites by Au-S bonds without any coupling agent. CA125 antigen was grabbed directly by its aptamer DNA due to its specific identification with the aptamer. Finally, the modified electrodes were blocked with BSA and then characterized. Finally, DPV analysis was used for CA125 detection, the novel fabricated biosensor demonstrated good detection properties for CA125 with a linear range of 5–125 U/mL and a detection limit of 4.4 U/mL. The results showed that the aptamer sensor had good specificity, repeatability, and stability. The feasibility of our sensor for the determination of CA125 was also demonstrated by measuring CA125 levels in serum using the Roche gold-standard instrument of the People’s Hospital of Danyang as the reference value. The recoveries of real serum samples were 94.65–101.71%, and RSDs were 1.26–4.65%. Moreover, the surface of the electrode could be cleaned and reused by magnetic separation, greatly reducing the cost and providing the possibility for a point-of-care test (POCT). This work demonstrated a new strategy for integrating both nanostructures and biocompatibility to build advanced cancer biomarker sensors with wide applications.

The Optimization of a Label-Free Electrochemical DNA Biosensor for Detection of Sus scrofa mtDNA as Food Adulterations

Fast, sensitive, and easy-to-use methods for detecting DNA related to food adulteration, health, religious, and commercial purposes are evolving. In this research, a label-free electrochemical DNA biosensor method was developed for the detection of pork in processed meat samples. Gold electrodeposited screen-printed carbon electrodes (SPCEs) were used and characterized using SEM and cyclic voltammetry. A biotinylated probe DNA sequence of the Cyt b S. scrofa gene mtDNA used as a sensing element containing guanine substituted by inosine bases. The detection of probe-target DNA hybridization on the streptavidin-modified gold SPCE surface was carried out by the peak guanine oxidation of the target using differential pulse voltammetry (DPV). The optimum experimental conditions of data processing using the Box–Behnken design were obtained after 90 min of streptavidin incubation time, at the DNA probe concentration of 1.0 µg/mL, and after 5 min of probe-target DNA hybridization. The detection limit was 0.135 µg/mL, with a linearity range of 0.5–1.5 µg/mL. The resulting current response indicated that this detection method was selective against 5% pork DNA in a mixture of meat samples. This electrochemical biosensor method can be developed into a portable point-of-care detection method for the presence of pork or food adulterations.