Present Biosensor Research Articles

An Improved Amperometric D-amino Acid Biosensor Based on Immobilization of D-Amino Acid Oxidase on Nanocomposite of Chitosan/Fe3O4NPs/ cMWCNT/GC Electrode

Objective: An improved amperometric D aminoacid (DAA) biosensor was fabricated by immobilizing covalently, D-amino acid oxidase (DAAO) onto nanocomposite of chitosan (CHIT)/ iron oxide nanoparticles (Fe3O4NPs)/ carboxylated multiwalled carbon nanotubes (cMWCNT)/ electrodeposited onto glassy carbon (GC) electrode Methods: The iron oxide nanoparticles (Fe3O4NPs) were prepared and characterized by UV spectroscopy, transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy. Results: The enzyme electrode (DAAO/CHIT/ Fe3O4NPs/cMWCNT/GC) was characterized by scanning electron microscopy (SEM), FTIR and electrochemical impedance spectroscopy (EIS). The biosensor showed maximum response within 2s at pH 8.0, 35°C and potential of 0.09V vs. Ag/AgCl with a linear working range of 0.02-0.80 μM, sensitivity of 919.29 μAcm-2μM-1 and detection limit of 0.02 μM. Conclusion: The within and between batch coefficients of variation (CVs) for determination of DAA by present biosensor were 2.35% and 2.87%, respectively. The level of DAA in real fruit juices as measured by the present biosensor matched with those by the standard spectrophotometric method with a good correlation (r = 0.978). The biosensor lost 30 % of its initial activity over a period of 120 days when stored dry at 4°C.

A Novel BioNEMS Sensor Based on Tunable Plasmonic Modes of a Grating MIM Structure

In this paper, a novel optical BioNEMS (Bio Nano-Electro-Mechanical-Systems) sensor using a nanomechanical plasmonic structure is proposed to develop a high performance label-free biosensor. The present device is composed of a functionalized BioNEMS cantilever coated by a gold layer as a part of the proposed plasmonic grating waveguide. This plasmonic system is based on the light interaction with a metallic nanostructure as a metal-insulator-metal (MIM) Bragg grating where an air gap acts as the insulator. Passing patient samples through the functionalized surface of the nanocantilever, the biological interactions release a stress on the surface because of binding events. The cantilever can be thus deflected by inducing a differential surface stress. Therefore, the air gap distance (the insulator width) between two parts of the plasmonic grating structure is changed to excite surface plasmon polaritons in a different wavelength. Furthermore, the present biosensor is analyzed by numerical and analytical approaches and its functional characteristics are obtained as follows: optical sensitivity of 7872 nm/RIU, figure of merit (FOM) of 394 RIU^-1, mechanical sensitivity of 1.2 µm/Nm^-1. According to the results, the proposed label-free identification method can be used as a sensitive platform for detection of biomarkers in point of care testing (POCT) applications.

Copolymerization of zwitterionic sulfobetaine and hydrophobic acrylamide based antifouling electrochemical biosensors for detection of CA125 in clinical serum samples

It is crucial to construct antifouling electrochemical biosensors with long-term stability and high sensitivity for the detection of biomarkers in complex biological environments to prevent the unspecific adsorption of proteins and other biomolecules. Herein, a glassy carbon electrode electropolymerization with polyaniline (PANI/GCE) was further modified with a copolymerization (PSN) of zwitterionic sulfobetaine methacrylate (SBMA) and hydrophobic N-isopropyl acrylamide (NIPAM) by simple hydrophobic interaction to construct an antifouling biosensor. PSN forms a stable self-assembled monolayer on the PANI/GCE surface and exhibits good antifouling performance in serum due to the advantages of hydrophobic anchoring and the antifouling performance of zwitterionic polymers. Ascribe to the large specific surface area and excellent conductivity, the present biosensor can detect CA125 in undiluted samples in the range of 0.01–1000 U mL−1 with a limit of detection of 2.7 mU mL−1 (3σ/k). Both with good biocompatibility and biological stability, PSN modified sensing surface realizes a long-term antifouling for 15 days in a buffer solution. The present work provides a simple strategy for the direct analysis of CA125 in human serum without a complicated construction of biosensors, indicating the potential application in clinical diagnosis.

An Amperometric Acetylcholine Biosensor Based on Co-Immobilization of Enzyme Nanoparticles onto Nanocomposite.

An electrochemical biosensor was fabricated using nanoparticles of acetylcholinesterase (AChE) and choline oxidase (ChO)/Pt nanoparticles (PtNPs)/porous graphene oxide nanosheet (GONS) composite. A pencil graphite electrode (PGE) was used for the electrodeposition of nanocomposite and the determination of acetylcholine (ACh), a neurotransmitter. Various techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectra and cyclic voltammetry (CV) were used for characterization. This biosensor (AChENPs-ChONPs/GONS/PtNPs/PGE) indicated a very short response time (3 s), a lower limit of detection (0.001 µM), good linearity (0.001-200 µM), longer storage stability (6 months) and better reproducibility. The percent analytical recoveries of added acetylcholine in serum (5.0 and 10 µM) were found to be 97.6 ± 0.7 and 96.5 ± 0.3 for the present biosensor. The coefficients of variation were obtained to be 8% and 3.25%, correspondingly. The biosensor was applied to measure the ACh amount in the serum of healthy individuals and patients with Alzheimer's disease. The number of interferents had no effect on the biosensor at their physiological concentrations.

Smartphone-controlled biosensor for viral respiratory infectious diseases: Screening and response

Outbreaks of emerging viral respiratory infectious diseases (VRIDs) including coronavirus disease 2019 (COVID-19) seriously endanger people's health. However, the traditional nucleic acid detection required professionals and larger instruments and antigen-antibody detection suffered a long window period of target generation. To facilitate the VRIDs detection in time for common populations, a smartphone-controlled biosensor, which integrated sample preparation (electromembrane extraction), biomarker detection (red-green-blue model) and remote response technology (a built-in APP), was developed in this work. With the intelligent biosensor, VRIDs could be recognized in the early stage by using endogenous hydrogen sulfide as the biomarker. Importantly, it only took 15 min to accomplish the whole process of screening and response to VRIDs. Moreover, the experimental data showed that this smartphone-controlled biosensor was suitable for ordinary residents and could successfully differentiate non-communicable respiratory diseases from VRIDs. To the best of our knowledge, this is the first time that a smartphone-controlled biosensor for screening and response to VRIDs was reported. We believe that the present biosensor will help ordinary residents jointly deal with the challenges brought by COVID-19 or other VRIDs in the future.

An Improved Amperometric Lactose Biosensor Based on Enzyme Nanoparticles

A desolvation method was used for the synthesis of β-galactosidase (β-GAL) and glucose oxidase (GOD) nanoparticles (NPs) using ethanol. The enzyme nanoparticles (ENPs) were characterized by transmission electron microscopy (TEM) and Fourier transform Infra-red spectroscopy (FTIR) and were co-immobilized covalently onto surface of polycrystalline Au electrode. An improved amperometric lactose biosensor was constructed using ENPs (β-GALNPs/GODNPs) modified Au electrode as working electrode, Ag/AgCl as reference electrode and Pt wire as auxiliary electrode connected through potentiostat. Cyclic voltammetry (CV) and scanning electron microscope (SEM) were used for the study of working electrode before and after immobilization of ENPs. The biosensor showed maximum current at 0.25V within 5s, at pH 6.5 and 25oC. The limit of detection (LOD) was i.e. 1mg/ml and working range was 1-10 mg/mL. The analytical recovery of added lactose (5 and 10 mg/mL) was 94.73±0.5% and 96.4±0.9%, respectively. Coefficient of variation (CV) within and between batch were <3.0 and <4.0 respectively. The biosensor exhibited a good correlation (R2=0.91) between lactose level in milk as measured by standard (enzymatic colorimetric) method and present biosensor. The biosensor was employed for quantification of lactose in milk from human, cow, buffalo and goat. The working electrode lost 50% of its initial activity within 3 months, after its 120 uses, while being stored dry at 4ºC.
 Int. J. Appl. Sci. Biotechnol. Vol 10(1): 21-30.

Integration of a capacitor to a 3-D DNA walker and a biofuel cell-based self-powered system for ultrasensitive bioassays of microRNAs.

A self-powered microRNA biosensor with triple signal amplification systems was assembled through the integration of three-dimensional DNA walkers, enzymatic biofuel cells and a capacitor. The DNA walker is designed from an enzyme-free target triggered catalytic hairpin assembly of modified gold nanoparticles. When triggered by the target microRNA, the DNA walker will move along the catalytic hairpin track, resulting in a payload release of glucose oxidase. The enzymatic biofuel cell contains the glucose oxidase bioanode and a bilirubin oxidase biocathode that bring a dramatic open circuit voltage to realize the self-powered bioassays of microRNA. A capacitor is further coupled with the enzymatic biofuel cell to further amplify the electrochemical signal, and the sensitivity increases 28.82 times through optimizing the matching capacitor. Based on this design, the present biosensor shows high performance, especially for detection limit and sensitivity. Furthermore, the present biosensor was successfully applied for serum samples, directly demonstrating its good application in clinical biomedicine and disease diagnosis.

An improved amperometric sarcosine biosensor based on graphene nanoribbon/chitosan nanocomposite for detection of prostate cancer

We describe herein an improved amperometric biosensor for detection of sarcosine, a potential biomarker for prostate cancer. The biosensor is based on covalent immobilization of sarcosine oxidase (SOx) onto nanocomposite of chitosan (CHIT) and graphene nanoribbons (GNRs) electrodeposited onto Au electrode. The GNRs were studied by transmission electron microscopy and UV spectroscopy. The working electrode (SOx/CHIT/GNRs/AuE) exhibited maximum current at a potential of 0.1V against Ag/AgCl, generated from electrochemical oxidation of H2O2, from sarcosine by immobilized SOx. The biosensor showed optimum response i.e. current (mA) within 2s at pH 7.3 and 35 ​°C. There was a linearity between current (mA) and sarcosine concentration in a wider range 0.001–100 ​μM with a minimum detection limit of 0.001 ​μM and a high sensitivity of 277.5 ​μA/μM/cm. Analytical recoveries of added sarcosine in sera were 97.35%, within and between-batch coefficients of variation were 1.08% and 1.40% respectively. A good correlation (R2 ​= ​0.99) was obtained between sera sarcosine values, as measured by the standard immuno kit method and present biosensor. The biosensor measured sarcosine levels in sera of prostate cancer patients, which was significantly higher than in apparently healthy persons. The enzyme electrode lost 20% of its initial activity during 180days, when stored dry at 4°C.

Development of the electrochemical biosensor for determination of antibiotic drug isoniazid using ds-DNA/Carbon/La3+/CuO/CPE

In this study, we developed a novel DNA sensor exploiting Carbon/La3+/CuO (C/La3+/CuO) nanocomposites for the determination of isoniazid (INZ). After modification of sensor by C/La3+/CuO, the electrode showed an excellent conductivity, and carbon possesses a large specific surface area, thereby enabling a significant improvement in the sensor sensitivity. Since no DNA probe modification or chemical labeling was required in this approach, this sensor could be employed to detect INZ. The present biosensor was selectively and sensitively able to detect INZ, with a wide linear range (1.0–165.0 μM) and a low limit of detection (0.035 μM). The fabricated biosensor was also used to detect INZ in the real samples successfully. Good recovery values were obtained, showing the excellent analytical potential of the electrochemical biosensor based on ds-DNA/C/La3+/CuO. Moreover, electrochemical, spectroscopic and docking methods showed an effective interaction between INZ and ds-DNA.

Ratiometric 3D DNA Machine Combined with Machine Learning Algorithm for Ultrasensitive and High-Precision Screening of Early Urinary Diseases.

Urinary extracellular vesicles (uEVs) have received considerable attention as a potential biomarker source for the diagnosis of urinary diseases. Present studies mainly focus on the discovery of biomarkers based on high-throughput proteomics, while limited efforts have been paid to applying the uEVs' biomarkers for the diagnosis of early urinary disease. Herein, we demonstrate a diagnosis protocol to realize ultrasensitive detection of uEVs and accurate classification of early urinary diseases, by combing a ratiometric three-dimensional (3D) DNA machine with machine learning (ML). The ratiometric 3D DNA machine platform is constructed by conjugating a padlock probe (PLP) containing cytosine-rich (C-rich) sequences, anchor strands, and nucleic-acid-stabilized silver nanoclusters (DNAAgNCs) onto the magnetic nanoparticles (MNPs). The competitive binding of uEVs with the aptamer releases the walker strand, thus the ratiometric 3D DNA machine was activated to undergo an accurate amplification reaction and produce a ratiometric fluorescence signal. The present biosensor offers a detection limit of 9.9 × 103 particles mL-1 with a linear range of 104-108 particles mL-1 for uEVs. Two ML algorithms, K-nearest neighbor (KNN) and support vector machine (SVM), were subsequently applied for analyzing the correlation between the sensing signals of uEV multibiomarkers and the clinical state. The disease diagnostic accuracy of optimal biomarker combination reaches 95% and 100% by analyzing with KNN and SVM, and the disease type classification exhibits an accuracy of 94.7% and 89.5%, respectively. Moreover, the protocol results in 100% accurate visual identification of clinical uEV samples from individuals with disease or as healthy control by a t-distributed stochastic neighbor embedding (tSNE) algorithm.

SENSITIVE DETERMINATION OF 3,4-DIHYDROXY-L-PHENYLALANINE BY A CLOUD FUNNEL MUSHROOM (Clitocybe nebularis (Batsch), P. Kumm.) HOMOGENATE-BASED AMPEROMETRIC BIOSENSOR

3,4-dihydroxy-L-phenylalanine (L-DOPA) is one of the precursor molecules for the biosynthesis of neurotransmitters in the brain. Monitoring of L-DOPA levels as a drug or biomolecule in biological fluids is crucial for the treatment of patients suffering from Parkinson’s Disease. This study aimed to construct a cloud funnel mushroom (Clitocybe nebularis (Batsch), P. Kumm.) tissue homogenate-based biosensor for precise and sensitive detection of L-DOPA in artificial plasma and urine. For this purpose, in the fabrication of the biosensor, tissue homogenate of C. nebularis was immobilized into a carbon paste electrode by using graphite, mineral oil, gelatine and glutaraldehyde. The amperometric signals corresponding to 600 s were recorded as response current for each L-DOPA concentration. All amperometric measurements were carried out at ⁻700 mV (versus Ag|AgCl). The present biosensor successfully detected L-DOPA with a linear dynamic range at 2.5-100 µM and Limit of Detection (LOD) value as 0.76 µM, as well as standard deviation as ±0.41 µM and coefficient of variation as 0.82% (n=16). Additionally, the determination of L-DOPA spiked in artificial plasma and urine was carried out successfully. The present work would be the first study that utilized C. nebularis tissue as a biosensor component.

Electrochemical Immunosensor for the Simultaneous Determination of Two Main Peanut Allergenic Proteins (Ara h 1 and Ara h 6) in Food Matrices.

Efficiently detecting peanut traces in food products can prevent severe allergic reactions and serious health implications. This work presents the development of an electrochemical dual immunosensor for the simultaneous analysis of two major peanut allergens, Ara h 1 and Ara h 6, in food matrices. A sandwich immunoassay was performed on a dual working screen-printed carbon electrode using monoclonal antibodies. The antibody–antigen interaction was detected by linear sweep voltammetry through the oxidation of enzymatically deposited silver, which was formed by using detection antibodies labeled with alkaline phosphatase and a 3-indoxyl phosphate/silver nitrate mixture as the enzymatic substrate. The assay time was 2 h 20 min, with a hands-on time of 30 min, and precise results and low limits of detection were obtained (Ara h 1: 5.2 ng·mL−1; Ara h 6: 0.017 ng·mL−1). The selectivity of the method was confirmed through the analysis of other food allergens and ingredients (e.g., hazelnut, soybean and lupin). The dual sensor was successfully applied to the analysis of several food products and was able to quantify the presence of peanuts down to 0.05% (w/w). The accuracy of the results was confirmed through recovery studies and by comparison with an enzyme-linked immunosorbent assay. Tracking food allergens is of utmost importance and can be performed using the present biosensor in a suitable and practical way.

An improved amperometric determination of xanthine with xanthine oxidase nanoparticles for testing of fish meat freshness

The nanoparticles of xanthine oxidase (XODNPs) were prepared by desolvation method and characterized by transmission electron microscopy(TEM) and Fourier transform Infra-red spectroscopy(FTIR). These XODNPs were immobilized directly onto surface of Au electrode via covalent bond. An improved amperometric xanthine biosensor was fabricated using XODNPs modified Au electrode, as working electrode (WE), Ag/AgCl as reference electrode and Pt wire as auxiliary electrode connected through potentiostat.The biosensor showed optimum current at 0.25 V within 5 s, at pH 7.0 and 35 °C.The working range of biosensor was 0.01–1.0 μM with a limit of detection of 0.01 μM.The % recovery of added xanthine (1 and 5 μM) was 94.1 ± 0.2 and 94.8 ± 0.31 respectively. Within and between batch coefficient of variation (CV) were <2% & < 2.5% respectively. A good correlation (R2 = 0.996) was obtained between xanthine contents in various fish meat,as measured by the present biosensor and the standard bienzymic colorimetric method. The biosensor was employed for measuring xanthine level in fish meat at different stages of storage to test its freshness. The XODNPs modified Au electrode was stored dry at 4 °C for 2 months.

A Novel Aptasensor Based on the Formation of Intermolecular G Quadruplex DNA and Carbon Dots for Fluorescence Determination Potassium Ions in Human Urine and Blood Serum Samples

The development of a high-performance biosensor for potassium ion (K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> ) analysis is desirable for clinical diagnostics. In the present study, a sensitive and selective biosensor has been presented for the K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> determination using G-rich ssDNA as a recognition tool. A fluorimetric assay based on intermolecular G-quadruplex was introduced using metal sulfide (CoS and CuS) nanosheets as quenchers and carbon dots (CDs) as fluorescence probes conjugated to a G-rich ssDNA (CDs-aptamer). This biosensor was based on the adsorption CDs-aptamer on the surface of nanosheets via van der Waals forces, which resulted in reducing the fluorescence signal. By addition K+ to the system, CDs-aptamer folded into G-quadruplex structure that causes to detach from nanosheets. As a result, the fluorescence signal was increased proportionally to K+ concentration. The present biosensor can detect K+ sensitively and selectively with 12.3 nmol L <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> as a low detection limit. A linear range was achieved from 50.0 nmol L <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> to 1000 nmol L <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> . Furthermore, this biosensor has been successfully applied for the detection of K+ in the real samples and was validated by comparing the data of analyzing real samples to results obtained by the ion-selective electrode (ISE).

Graphene Oxide Nanoparticles Decorated Pencil Lead as Urea Sensing Electrode

In present study, a low-cost and steady electrochemical biosensor has been developed based on graphene oxide nanoparticles (GONPs), electrodeposited on the pencil lead electrode (PLE). The physical and morphological studies revealed the nano-scale range of GONPs that has an average grain size/layer thickness of 2.27 nm and agglomeration size of 90-120 nm. Urease enzyme was immobilized on PLE/GONPs electrode after surface treatment with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC)/N-hydroxysuccinimide (NHS) to impart stable peptide bond. Scanning electron microscopy (SEM) studies demonstrate the difference between unmodified and modified PLE electrodes and depict the spherical, circular and flaky-like morphology. The electrochemical analysis of urea considerably improved on the PLE/GONPs/Ur compared to the untailored PLE electrode. The reported urea biosensor operated in a linear dynamic range between 0.30-50 mM that attained a recognition limit of 0.06 mM and exhibited an advanced exposure sensitivity of 0.814 μA mM-1 cm-2.

A Measurement Platform for Label-Free Detection of Biomolecules Based on a Novel Optical BioMEMS Sensor

In this article, a novel optical Bio-microelectromechanical system (MEMS) sensing platform is proposed based on a tunable laser and its lasing wavelength to detect the biomolecules and measure their quantities. The present biosensor consists of a BioMEMS cantilever and a proposed external cavity tunable laser. While the target samples (i.e., DNA, mRNA, or protein) are exposed to the cantilever surface, target-analyte bindings are happened. This can induce a surface stress on the MEMS cantilever and results in its bending due to the surface stress difference in each side of the cantilever. Thus, the gap size between the laser cavity and the gain medium is changed which can be measured by the wavelength variations of the proposed tunable laser source. Consequently, by analyzing the output response, one can detect the amount of target biomolecules in the sample and assign a level of contamination, infection, or bioparticles, caused by the specific disease. Various parameters of the proposed device are designed by numerical and analytical approaches. Furthermore, functional characteristics of the present BioMEMS sensor are obtained as follows: mechanical sensitivity of $1.8~\mu \text{m}$ /Nm−1, optical sensitivity of 422 nm/RIU, Q-factor of 610, and resonant frequency of 6.43 kHz. The obtained functional characteristics of the proposed device show that the present optical BioMEMS sensor can be appealing for highly sensitive diagnoses of various types of diseases and their progress level.

Avidin-Biotin Technology in Gold Nanoparticle-Decorated Graphene Field Effect Transistors for Detection of Biotinylated Macromolecules with Ultrahigh Sensitivity and Specificity.

The strong and specific noncovalent interaction between avidin and biotin is widely exploited in different types of enzyme-linked immunosorbent assay kits, labeled immunosensors, and polymer-based sensing devices for the detection of different biomarkers specific to different diseases such as cancer and influenza. Here, we employed the avidin–biotin technology in a novel gold nanoparticle-decorated graphene field-effect transistor (AuNP-GFET) and demonstrated the specific detection of the biotinylated macromolecules such as biotinylated proteins and nucleotides in the sub-picomolar (pM) range. The AuNP-GFET was constructed by fabricating six pairs of interdigital electrodes on graphene transferred on a SiO2/Si substrate. The sensing performance of AuNP-GFET was characterized by the real-time two-terminal electrical current measurement upon injection of the analyte solution into a silicone pool preattached onto the electrodes. Avidin, a tetrameric biotin-binding protein with strong affinity and specificity, immobilized on AuNP-decorated single-layer graphene, was used as the sensing platform and transduced the electrical signal upon binding to the analyte macromolecules. The sensing capability of the AuNP-GFET was tested with the biotinylated protein A. Sensitivity of the present biosensor was estimated to be ∼0.4 pM. The specificity and applicability of the biosensor were confirmed using both synthetic and real samples. Because the biotin label can retain its binding capability to avidin with strong affinity and specificity even after conjugating with varieties of proteins and nucleotides, the present AuNP-GFET biosensor is expected to promote the research in developing different biosensors.

Electrochemical sensing of cytochrome c using Graphene Oxide nanoparticles as platform

An improved cytochrome c (Cyt c) biosensor based on immobilization of cytochrome c oxidase (COx) on the surface of graphene oxide nanoparticles (GONPs) electrodeposited onto pencil graphite (PG) electrode. Characterization of graphene oxide nanoparticle was done by Transmission electron microscopy (TEM), Fourier transform infra-red spectroscopy (FTIR) and X-ray diffraction study (XRD). The working electrode (COx/GONPs/PG) was characterized at its different stages of fabrication by scanning electron microscopy (SEM) and FTIR. Fabrication of Cyt c biosensor was done by connecting COx/GONPs/PG as working electrode, Ag/AgCl as reference electrode and Pt as auxiliary electrode to potentiostat. The mechanism of detection of present biosensor was based on oxidation of Cyt c (reduced) to Cyt c (oxidized) by COx resulting in flow of electrons through GONPs to the PG electrode, hence current generated is proportional to the concentration of Cyt c. Present biosensor exhibited optimum potential at 0.49 V with optimum pH 7.5 and optimum temperature 35°C. Biosensor showed linearity within 40–180 ng/ml having 40 ng/ml limit of detection. The precision i.e. within and between-batch coefficients of variation (CVs) were found <0.04% and <0.21% respectively. The enzyme electrode lost 50% of its initial activity when operated for more than 6 months on weekly basis. It was applied for detection of Cyt c level in in apparently healthy and diseased human sera. The present biosensing method was co-related with standard colorimetric method and co-relation coefficient was found 0.99.

Cancer Cell Detection‐Based on Released Hydrogen Peroxide Using a Non‐Modified Closed Bipolar Electrochemical System

AbstractIn this study, a non‐modified closed bipolar electrochemical system for ultrasensitive cancer cell detection by quantitative measurement of released hydrogen peroxide in the presence of ascorbic acid has been developed. This system includes two separate chambers (reporting and sensing), a piece of a gold archival CD (compact disc) as a bipolar electrode, and two platinum driving electrodes. By following the ECL (electrochemiluminescence) intensities of luminol oxidation in the reporting chamber, the hydrogen peroxide released by cancer cells in the presence of ascorbic acid was monitored. Under the optimum conditions, the biosensor delivers a wide linear range from 2.5×10−9 to 1×10−6 M, and a detection limit for hydrogen peroxide as low as 1.8×10−9 M. Also, this system can detect cancer blood cell concentrations (CCRF‐CEM: T‐lymphoblastic leukemia cell line) as low as 12 cells in 300 μL of cell suspension. The present bipolar electrode‐electrochemiluminescence (BPE‐ECL) system demonstrates a simple and low‐cost device with excellent performance without any electrode surface modification for the detection of cancer cells based on different levels of released hydrogen peroxide by normal and cancer cells. The present biosensor can be applied as a promising alternative method for the detection of H2O2 in the field of pathology, cancer diagnosis, and environmental monitoring.

A Sensitive Impedimetric Aptasensor Based on Carbon Nanodots Modified Electrode for Detection of 17ß-Estradiol.

A simple and sensitive aptasensor based on conductive carbon nanodots (CDs) was fabricated for the detection of 17ß-Estradiol (E2). In the present study, the hydrothermal synthesis of carbon nanodots was successfully electrodeposited on a screen-printed electrode (SPE) as a platform for immobilization of 76-mer aptamer probe. The morphology and structure of the nanomaterial were characterized by UV-visible absorption spectra, Fluorescence spectra, Transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). Moreover, cyclic voltammetry and electrochemical impedance spectroscopy were used to investigate the electrochemical performance of the prepared electrodes. Subsequently, impedimetric (EIS) measurements were employed to investigate the relative impedances changes before and after E2 binding, which results in a linear relationship of E2 concentration in the range of 1.0 × 10−7 to 1.0 × 10 −12 M, with a detection limit of 0.5 × 10−12 M. Moreover, the developed biosensor showed high selectivity toward E2 and exhibited excellent discrimination against progesterone (PRG), estriol (E3) and bisphenol A (BPA), respectively. Moreover, the average recovery rate of spiked river water samples with E2 ranged from 98.2% to 103.8%, with relative standard deviations between 1.1% and 3.8%, revealing the potential application of the present biosensor for E2 detection in water samples.