Carboxyethylsilanetriol-Coated Magnetic Nanoparticles as an Ultrasensitive Immunoplatform for Electrochemical Magnetosensing of Cotinine.

In the present study, an innovative and simple electrochemical magneto biosensor based on carboxyethylsilanetriol-modified iron oxide (Fe3O4) magnetic nanoparticles was designed for ultrasensitive and specific analysis of cotinine, an important marker of smoking. Anticotinine antibodies were covalently immobilized on carboxylic acid-modified magnetic nanoparticles, and the cotinine-specific magnetic nanoparticles created a specific surface on the working electrode surface. The use of magnetic nanoparticles as an immobilization platform for antibodies provided a large surface area for antibody attachment and increased sensitivity. In addition, the advantages of the new immobilization platform were reusing the working electrode numerous times, recording repeatable and reproducible signals, and reducing the necessary volume of biomolecules. The specific interaction between cotinine and cotinine-specific antibody-attached magnetic nanoparticles restricted the electron transfer of the redox probe and changed the impedimetric response of the electrode correlated to the concentration of cotinine. The magneto biosensor had a wide detection range (2-300 pg/mL), a low LOD (606 fg/mL), and an acceptable recovery (97.24-105.31%) in real samples. In addition, the current biosensor's measurement results were in good agreement with those found by the standard liquid chromatography (HPLC) and enzyme-linked immunosorbent assay (ELISA) methods. These results showed that a simple impedimetric immunosensing platform was generated for the cotinine analysis.

Label-Free Electrochemical Immunosensor Based on Conjugated Polymer Film Coated Disposable Electrode for Ultrasensitive Determination of Resistin Potential Obesity Biomarker.

A new label-free immunosensor was designed for sensitive detection of resistin obesity biomarker in human biological fluids. To construct a sensing interface, the monomer of double epoxy groups-substituted thiophene (TdiEpx) was synthesized for the fabrication of the biosensing system. A disposable indium tin oxide sheet was first modified by electrochemical polymerization of the TdiEpx monomer, and this robust and novel surface was characterized using different spectroscopic and electrochemical analyses. The double epoxy ends were linked to the amino ends of anti-resistin, and they served as binding points for the covalent binding of biomolecules. The double epoxy ends present in each TdiEpx monomer ensured an extensive surface area, which improved the quantity of attached anti-resistin. The determination of resistin antigen was based on the specific coupling of resistin with anti-resistin, and this interaction hindered the electron transfer reaction. The immunosensor introduced a wide linear range of 0.0125-15 pg/mL, a low detection limit of 4.17 fg/mL, and an excellent sensitivity of 1.38 kohm pg mL-1 cm2. In this study, a sandwich enzyme-linked immunosorbent assay spectrophotometric method was utilized as a reference technique for the quantitative analysis of resistin in human serum and saliva samples. Both measurements in clinical samples displayed correlations and high-correlation coefficients. In addition, this immunosensor had good storage stability, acceptable repeatability and reproducibility, high specificity, and good accuracy. The proposed immunosensor provided a simple and versatile impedimetric immunosensing platform and a promisingly sensitive way for clinical applications.

Ultrasensitive detection of NSE employing a novel electrochemical immunosensor based on a conjugated copolymer.

In the current study a simple and highly specific label-free impedimetric neuron specific enolase (NSE) immunosensor based on a copolymer matrix-coated disposable electrode was designed and tested. The copolymer matrix was prepared using a very conductive EDOT monomer and semi-conductive thiophene-bearing epoxy groups (ThEp), and the combination of the two monomers enhanced the conductivity and protein loading capacity of the electrode surface. The P(ThEp-co-EDOT) copolymer matrix was prepared via a drop-casting process and anti-NSE recognition biomolecules were immobilized directly on the epoxy groups of the copolymer. After the coupling of NSE molecules on the P(ThEp-co-EDOT) copolymer matrix-coated electrode surface, the charge transfer resistance (Rct) of the biosensor changed dramatically. These changes in Rct were proportional to the NSE molecule amounts captured by anti-NSE molecules. Under optimized experimental conditions, the increment in the Rct value was proportional to the NSE concentration over a range of 0.01 to 25 pg mL-1 with a detection limit (LOD) of 2.98 × 10-3 pg mL-1. This copolymer-coated electrode provided a lower LOD than the other biosensors. In addition, the suggested electrochemical immuno-platform showed good selectivity, superior reproducibility, long-term stability, and high recovery of NSE in real serum (95.64-102.20%) and saliva (95.28-105.35%) samples. These results showed that the present system had great potential for electrochemical biosensing applications.

An innovative method for the detection of alpha synuclein, a potential biomarker of Parkinson's disease: quartz tuning fork-based mass sensitive immunosensor design.

An innovative biosensing fabrication strategy has been demonstrated for the first time using a quartz tuning fork (QTF) to develop a practical immunosensor for sensitive, selective and practical analysis of alpha synuclein protein (SYN alpha), a potential biomarker of Parkinson's disease. Functionalization of gold-coated QTFs was carried out in 2 steps by forming a self-assembled monolayer with 4-aminothiophenol (4-ATP) and conjugation of gold nanoparticles (AuNPs). The selective determination range for SYN alpha of the developed biosensor system is 1-500 ng mL-1 in accordance with the resonance frequency shifts associated with a limit of detection of 0.098 ng mL-1. The changes in surface morphology and elemental composition were evaluated using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and energy-dispersive X-ray spectroscopy (EDX). The remarkable point of the study is that this QTF based mass sensitive biosensor system can capture the SYN alpha target protein in cerebrospinal fluid (CSF) samples with recoveries ranging from 92% to 104%.

A new immunosensing platform based on conjugated Poly(ThidEp-co-EDOT) copolymer for resistin detection, a new obesity biomarker.

The design of a novel electrochemical impedimetric biosensor for label-free analysis of resistin, a biomarker for obesity, is reported. For the fabrication of the immunosensor, a novel approach composed of electrochemical copolymerization of double epoxy groups-substituted thiophene (ThidEp) and 3,4-Ethylenedioxythiophene (EDOT) monomers was utilized. Anti-resistin antibodies were covalently attached to the copolymer-coated electrode. The capture of resistin antigens by anti-resistin antibodies caused significant variations in charge transfer resistance (Rct) because of the immunoreactions between these proteins. Under optimum experimental variables, the changes in impedance signals were employed for the determination of resistin antigen concentration, and the prepared immunosensor based on conjugated copolymer illustrated a wide linear range between 0.0125 and 22.5 pg/mL, a low detection limit (LOD) of 3.71 fg/mL, and a good sensitivity of 1.22 kΩ pg-1mL cm2. The excellent analytical performance of the resistin immunosensor in terms of selectivity, sensitivity, repeatability, reproducibility, storage stability, and low detection limit might be attributed to the conductive copolymer film layer generation on the disposable indium tin oxide (ITO) platform. The capability of this system for the determination of resistin in human serum and saliva samples was also tested. The immunosensor results were in accordance with the enzyme-linked immunosorbent assay (ELISA) results. The matrix effects of human serum and saliva were also investigated, and the proposed immunosensor displayed good recovery ranging from 95.91 to 106.25%. The engineered immunosensor could open new avenues for obesity monitoring.

Point-of-care testing: a disposable label-free electrochemical CA125 and HE4 immunosensors for early detection of ovarian cancer.

Cancer antigen 125 (CA125) and human epididymal secretory protein 4 (HE4) are critical biomarkers for ovarian cancer diagnosis and progression monitoring; therefore, sensitive determination of their levels in body fluids is crucial. In recent study, label-free CA125 and HE4 immunosensors were prepared using disposable screen-printed carbon electrodes modified with reduced graphene oxide, polythionine, and gold nanoparticles for the sensitive, fast, and practical determination of CA125 and HE4. Differential pulse voltammetry, square wave voltammetry, and electrochemical impedance spectroscopy methods were used for the electrochemical determination of antigens in four different linear ranges (1-100 pg mL- 1, 0.01-10 ng mL- 1, 10-50 ng mL- 1, and 50-500 ng mL- 1). High sensitivity, low limit of detection, and limit of quantification were obtained for each linear range with a correlation coefficient above 0.99. The application stability of CA125 and HE4 immunosensors was determined as 60 days, and the storage stability was determined as 16 weeks. Immunosensors showed high selectivity in nine different antigen mixtures. The reusability of the immunosensors has been tested up to 9 cycles. The Risk of Ovarian Malignancy Algorithm score% values were calculated using the concentration of CA125 and HE4 in the blood serum and evaluated in terms of ovarian cancer risk. For the point-of-care testing, CA125 and HE4 levels at pg mL- 1 concentration were measured in blood serum samples using the developed immunosensors and a hand-held electrochemical reader in approximately 20-30 s, and high recoveries were obtained. These disposable label-free immunosensors are user-friendly and can be used in point-of-care tests for rapid and practical detection of CA125 and HE4 with high selectivity, sensitivity, and repeatability.

A novel electrochemical impedance immunosensor for the quantification of CYFRA 21-1 in human serum.

A sensitive, simple, and reliable immunosensor was constructed to detect the lowest alteration of a fragment of cytokeratin subunit 19 (CYFRA 21-1), a protein lung carcinoma biomarker. The proposed immunosensor was manufactured with a carbon black C45/polythiophene polymer-containing amino terminal groups (C45-PTNH2) conductive nanocomposite, resulting in an excellent, biocompatible, low-cost, and electrically conductive electrode surface. Anti-CYFRA 21-1 biorecognition molecules were attached to the electrode thanks to the amino terminal groups of the used PTNH2 polymer with a relatively simple procedure. All electrode surfaces after modifications were characterized by electrochemical, chemical, and microscopic techniques. Electrochemical impedance spectroscopy (EIS) was also utilized for the evaluation of the analytical feature of the immunosensor. The charge transfer resistance of the immunosensor signal was correlated with the CYFRA 21-1 concentration in the concentration range 0.03 to 90 pg/mL. The limit of detection (LOD) and the limit of quantification (LOQ) of the suggested system were 4.7 fg/mL and 14.1 fg/mL, respectively. The proposed biosensor had favorable repeatability and reproducibility, long storage stability, excellent selectivity, and low cost. Furthermore, it was applied to determine CYFRA 21-1 in commercial serum samples, and satisfactory recovery results (98.63-106.18%) were obtained. Thus, this immunosensor can be offered for clinical purposes as a rapid, stable, low-cost, selective, reproducible, and reusable tool.

Biosensors for saliva biomarkers.

The analysis of salivary biomarkers has gained interest and is advantageous for simple, safe, and non-invasive testing in diagnosis as well as treatment. This chapter explores the importance of saliva biomarkers and summarizes recent advances in biosensor fabrication. The identification of diagnostic, prognostic and therapeutic markers in this matrix enables more rapid and frequent testing when combined with the use of biosensor technology. Challenges and future goals are highlighted and examined.

A label-free dual immunosensor for the simultaneous electrochemical determination of CA125 and HE4 biomarkers for the early diagnosis of ovarian cancer.

The blood levels of cancer antigen 125 (CA125) and human epididymal secretory protein 4 (HE4) are measured in the diagnosis and progression monitoring of ovarian cancer (OC), and the Risk of Ovarian Malignancy Algorithm (ROMA) score% values are calculated for cancer risk assessment. For the first time, disposable dual screen-printed carbon electrodes modified with reduced graphene oxide, polythionine, and gold nanoparticles were used to fabricate label-free electrochemical dual CA125-HE4 immunosensors for the sensitive, fast, and practical simultaneous determination of CA125 and HE4. DPV and SWV methods were used to simultaneously determine antigens in two different linear ranges (1-100 pg mL-1 and 1-50 ng mL-1). High sensitivity, low LOD, and LOQ were obtained for two linear ranges with a correlation coefficient above 0.99. The application stability of the dual CA125-HE4 immunosensors was determined as 60 days, and the storage stability was determined as 16 weeks. The dual immunosensors exhibited high selectivity in eight different antigen mixtures. The reusability of the dual immunosensors has been tested up to 9 cycles. ROMA score% values for pre-menopausal and post-menopausal status were calculated using the concentration of CA125 and HE4 in the blood serum and assessing OC risk. The disposable dual immunosensors can be used in point-of-care tests for rapid and practical simultaneous determination of CA125 and HE4 with high selectivity, sensitivity, and repeatability.

Lab-on-a-chip systems for cancer biomarker diagnosis.

Lab-on-a-chip (LOC) or micro total analysis system is one of the microfluidic technologies defined as the adaptation, miniaturization, integration, and automation of analytical laboratory procedures into a single instrument or "chip". In this article, we review developments over the past five years in the application of LOC biosensors for the detection of different types of cancer. Microfluidics encompasses chemistry and biotechnology skills and has revolutionized healthcare diagnosis. Superior to traditional cell culture or animal models, microfluidic technology has made it possible to reconstruct functional units of organs on chips to study human diseases such as cancer. LOCs have found numerous biomedical applications over the past five years, including integrated bioassays, cell analysis, metabolomics, drug discovery and delivery systems, tissue and organ physiology and disease modeling, and personalized medicine. This review provides an overview of the latest developments in microfluidic-based cancer research, with pros, cons, and prospects.

An ultrasensitive and disposable electrochemical aptasensor for prostate-specific antigen (PSA) detection in real serum samples.

In this study, we constructed a disposable indium tin oxide polyethylene terephthalate film (ITO-PET)-based electrochemical aptasensor for analyzing prostate-specific antigen (PSA), one of the most important biomarkers of prostate cancer. Because of their clinical importance, building PSA biosensing systems with high sensitivity and stability is essential. However, it still presents significant difficulties, such as low detection limits. We designed a platform to covalently bind the amino-terminated aptamer by modifying the ITO-PET surface with carboxyethylsilanetriol (CTES) to obtain a self-assembled monolayer (SAM). We also evaluated the potential for use in real human serum samples by investigating the optimal operating conditions and analytical performance characteristics of the developed biosensor. The design we present here exhibits excellent precision, with a limit of detection (LOD) as low as 8.74 fg/mL PSA. The broad linear detection range of the biosensor under optimal conditions was determined as 1.0-1500 fg/mL. The dissociation constant (Kd) for the aptamer was also calculated as 46.28 ± 5.63 nM by evaluating the impedimetric response as a function of PSA concentration. The aptasensor displayed considerable repeatability (1.3% RSD) and reproducibility (7.51% RSD) and good storage stability (98.34% of the initial activity for 8 weeks). Additionally, we demonstrated that the technique we developed was quite efficient in estimating the kinetics of aptamer-analyte interactions by determining the Kd and single-frequency impedance (SFI) data. In conclusion, we proposed a selective and sensitive biosensor with the potential for clinical application and superior performance in real serum samples.

A Simple and Low-Cost Electrochemical Immunosensor for Ultrasensitive Determination of Calreticulin Biomarker in Human Serum.

An early on time detection of breast cancer significantly affects the treatment process and outcome. Herein, a new label-free impedimetric biosensor is developed to determine the lowest change in the level of calreticulin (CALR), which is a new biomarker of breast carcinoma. The proposed immunosensor is fabricated by using reduced graphene oxide/amino substituted polypyrrole polymer (rGO-PPyNH2 ) nanocomposite modified disposable electrode. The anti-CALR antibodies are first attached on the rGO-PPyNH2 nanocomposite coated electrode through glutaraldehyde crosslinking; the CALR antigens are then immobilized with the addition of CALR antigens to form an immunocomplex on the sensing surface. This immunocomplex induces considerably larger interfacial electron transport resistance (Rct ). The variation in the Rct has a linear relationship with CALR level in the detection range of 0.025 to 75 pg mL-1 , with a detection limit of 10.4 fg mL-1 . The suggested biosensor shows high selectivity to CALR, good storage stability (at least 5 weeks) and suitable reproducibility results as shown in quality control chart. The designed immunosensor is utilized to analyze CALR levels in human sera with satisfying results. This immunosensor provides a novel way for the clinical determination of CALR and other cancer biological markers.

Fluid-based wearable sensors: a turning point in personalized healthcare.

Nowadays, it has become very popular to develop wearable devices that can monitor biomarkers to analyze the health status of the human body more comprehensively and accurately. Wearable sensors, specially designed for home care services, show great promise with their ease of use, especially during pandemic periods. Scientists have conducted many innovative studies on new wearable sensors that can noninvasively and simultaneously monitor biochemical indicators in body fluids for disease prediction, diagnosis, and management. Using noninvasive electrochemical sensors, biomarkers can be detected in tears, saliva, perspiration, and skin interstitial fluid (ISF). In this review, biofluids used for noninvasive wearable sensor detection under four main headings, saliva, sweat, tears, and ISF-based wearable sensors, were examined in detail. This report analyzes nearly 50 recent articles from 2017 to 2023. Based on current research, this review also discusses the evolution of wearable sensors, potential implementation challenges, and future prospects.

Ultrasensitive and Cost-Effective Detection of Neuropeptide-Y by a Disposable Immunosensor: A New Functionalization Route for Indium-Tin Oxide Surface.

Neuropeptide Y (NPY) is one of the most abundant neuropeptides in the human brain, and its levels in the blood change in neurodegenerative and neuroimmune disorders. This indicates that NPY may serve as a diagnostic and monitoring marker for associated disorders. In this paper, an electrochemical immunosensor was created to detect NPY biomarkers using a novel immobilization technique. The proposed biosensor system enables accurate, specific, cost-effective, and practical biomarker analysis. Indium tin oxide-coated polyethylene terephthalate (ITO-PET) sheets were treated with hexamethylene diisocyanate (HMDC) to covalently immobilize antibodies. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques were used to analyze each step of the biosensors. The proposed NPY biosensor has a broad linear detection range (0.01-100 pg mL-1), a low limit of detection (LOD) (0.02968 pg mL-1), and a low limit of quantification (LOQ) (0.0989 pg mL-1). Atomic force microscopy (AFM) was used to support in the optimization process, study the surface morphology, and visualize it. Studies of repeatability, reproducibility, storage, and Kramers-Kronig transformation were conducted during electrochemical characterization. After analytical experiments, the biosensor's responses to human serum samples were evaluated. According to the obtained data, the error margin is small, and the created biosensor offers a great deal of promise for the clinical measurement of NPY.

Impedimetric Detection of Calreticulin by a Disposable Immunosensor Modified with a Single-Walled Carbon Nanotube-Conducting Polymer Nanocomposite.

A label-free impedimetric immunosensing system was constructed for ultrasensitive determination of the calreticulin (CALR) biological marker in human serum samples utilizing an electrochemical impedance spectroscopy analysis technique for the first time. The new biosensor fabrication procedure consisted of electrodeposition of single-walled carbon nanotubes (SWCNTs) incorporating polymerization of an oxiran-2-yl methyl 3-(1H-pyrrol-1-yl) propanoate monomer (Pepx) onto a low-cost and disposable indium tin oxide (ITO) electrode. The SWCNTs-PPepx nanocomposite layer was prepared onto the ITO after the one-step fabrication procedure. The fabrication procedure of the immunosensor and the characteristic biomolecular interactions between the anti-CALR and CALR were characterized by electrochemical analysis and morphological monitoring techniques. Under optimum conditions, the proposed biosensor was responsive to CALR concentrations over the detection ranges of 0.015-60 pg/mL linearly, and it had a very low detection limit (4.6 fg/mL) and a favorable sensitivity (0.43 kΩ pg-1 mL cm-2). The reliability of the biosensor system in clinical analysis was investigated by successful quantification of CALR levels in human serum. Moreover, the repeatability and reproducibility results of the biosensor were evaluated by using Dixon, Grubbs, T-test, and F-tests. Consequently, the proposed biosensor was a promising method for scientific, rapid, and successful analysis of CALR in human serum samples.

Lateral flow assays for viruses diagnosis: Up-to-date technology and future prospects.

Bacteria, viruses, and parasites are harmful microorganisms that cause infectious diseases. Early detection of diseases is critical to prevent disease transmission and provide epidemic preparedness, as these can cause widespread deaths and public health crises, particularly in resource-limited countries. Lateral flow assay (LFA) systems are simple-to-use, disposable, inexpensive diagnostic devices to test biomarkers in blood and urine samples. Thus, LFA has recently received significant attention, especially during the pandemic. Here, first of all, the design principles and working mechanisms of existing LFA methods are examined. Then, current LFA implementation strategies are presented for communicable disease diagnoses, including COVID-19, zika and dengue, HIV, hepatitis, influenza, malaria, and other pathogens. Furthermore, this review focuses on an overview of current problems and accessible solutions in detecting infectious agents and diseases by LFA, focusing on increasing sensitivity with various detection methods. In addition, future trends in LFA-based diagnostics are envisioned.

A direct and simple immobilization route for immunosensors by CNBr activation for covalent attachment of anti-leptin: obesity diagnosis point of view.

Leptin is a peptide hormone produced in adipose tissue that works as an antiobesity hormone by balancing energy intake and expenditure. We aimed to develop an ultrasensitive electrochemical immunosensor based on a novel immobilization technique for the early detection of leptin-related diseases in this work. Although several methods for immobilizing antibodies to the biosensor recognition element are known, it is necessary to utilize novel, cost-effective, and less complicated immobilization procedures. When compared with currently utilized immobilization techniques for leptin measurement, this novel method is more efficient, easy to prepare, and sensitive, with a broad detection range. Indium tin oxide-coated polyethylene terephthalate (ITO-PET) sheets were used as the working electrode. ITO-PET sheets were modified using cyanogen bromide (CNBr) to immobilize the anti-leptin antibody through covalent interactions. Each stage of the proposed biosensors was characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) methods, and extensive characterization studies were carried out. The designed biosensor has a wide linear detection range (0.05-100 pg/mL), low limits of detection (LOD) (0.0086 pg/mL) and quantification (LOQ) (0.0287 pg/mL). It was concluded that although it is disposable, the ITO-PET working electrode retains its activity even in repeated studies. In addition, the new immobilization procedure provided by CNBr for the designed biosensor fabrication can be effectively used in other biosensing applications. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13205-021-03096-w.

Biosensing strategies for diagnosis of prostate specific antigen.

Almost from the time of its discovery, the prostate specific antigen (PSA) has been one of the most accurate and most extensively studied indicators of prostate cancer (PC). Because of advancements in biosensing systems and technology, PSA analysis methods have been substantially updated and enhanced as compared to their first instances. With the development of techniques in biosensor technology, the number of PSA biosensors that can be used in the biomedical sector is increasing year by year. Many different recognition elements and transducers have been used in the development of biosensor systems that exhibit high sensitivity, selectivity, and specificity. Here in this review, we provide a current overview of the different approaches to PSA detection.

Biosensor approaches on the diagnosis of neurodegenerative diseases: Sensing the past to the future.

Early diagnosis of neurodegeneration-oriented diseases that develop with the aging world is essential for improving the patient's living conditions as well as the treatment of the disease. Alzheimer's and Parkinson's diseases are prominent examples of neurodegeneration characterized by dementia leading to the death of nerve cells. The clinical diagnosis of these diseases only after the symptoms appear, delays the treatment process. Detection of biomarkers, which are distinctive molecules in biological fluids, involved in neurodegeneration processes, has the potential to allow early diagnosis of neurodegenerative diseases. Studies on biosensors, whose main responsibility is to detect the target analyte with high specificity, has gained momentum in recent years with the aim of high detection of potential biomarkers of neurodegeneration process. This study aims to provide an overview of neuro-biosensors developed on the basis of biomarkers identified in biological fluids for the diagnosis of neurodegenerative diseases such as Alzheimer's disease (AD), and Parkinson's disease (PD), and to provide an overview of the urgent needs in this field, emphasizing the importance of early diagnosis in the general lines of the neurodegeneration pathway. In this review, biosensor systems developed for the detection of biomarkers of neurodegenerative diseases, especially in the last 5 years, are discussed.