A highly sensitive immunosensor based on ITO thin films covered by a new semi-conductive conjugated polymer for the determination of TNFα in human saliva and serum samples

Biomedical Application of Electroactive Polymers in Electrochemical Sensors: A Review

Conducting polymers are of interest due to their unique behavior on exposure to electric fields, which has led to their use in flexible electronics, sensors, and biomaterials. The unique electroactive properties of conducting polymers allow them to be used to prepare biosensors that enable real time, point of care (POC) testing. Potential advantages of these devices include their low cost and low detection limit, ultimately resulting in increased access to treatment. This article presents a review of the characteristics of conducting polymer-based biosensors and the recent advances in their application in the recognition of disease biomarkers.

A flow-through microfluidic system for the detection of circulating melanoma cells

We report the fabrication of polyaniline nanofiber (PANI)-modified screen-printed electrode (PANI/SPE) incorporated in a poly-dimethylsiloxane (PDMS) microfluidic channel for the detection of circulating tumor cells. We employed this device to detect melanoma skin cancer cells through specific immunogenic binding of cell surface biomarker melanocortin 1 receptor (MC1R) to anti-MC1R antibody. The antibody-functionalized PANI/SPE was used in batch-continuous flow-through fashion. An aqueous cell suspension of ferri/ferrocyanide at a flow rate of 1.5 mL/min was passed over the immunosensor, which allowed for continuous electrochemical measurements. The sensor performed exceptionally well affording an ultralow limit of quantification of 1 melanoma cell/mL, both in buffer and when mixed with peripheral blood mononuclear cells, and the response was log-linear over the range of 10-9000 melanoma cells/10 mL.

Biosensors in Drug Discovery and Drug Analysis

Background:

The determination of drugs in pharmaceutical formulations and human biologic fluids is important for pharmaceutical and medical sciences. Successful analysis requires low sensitivity, high selectivity and minimum interference effects. Current analytical methods can detect drugs at very low levels but these methods require long sample preparation steps, extraction prior to analysis, highly trained technical staff and high-cost instruments. Biosensors offer several advantages such as short analysis time, high sensitivity, real-time analysis, low-cost instruments, and short pretreatment steps over traditional techniques. Biosensors allow quantification not only of the active component in pharmaceutical formulations, but also the degradation products and metabolites in biological fluids. The present review gives comprehensive information on the application of biosensors for drug discovery and analysis. Moreover, this review focuses on the fabrication of these biosensors.

Methods:

Biosensors can be classified as the utilized bioreceptor and the signal transduction mechanism. The classification based on signal transductions includes electrochemical optical, thermal or acoustic. Electrochemical and optic transducers are mostly utilized transducers used for drug analysis. There are many biological recognition elements, such as enzymes, antibodies, cells that have been used in fabricating of biosensors. Aptamers and antibodies are the most widely used recognition elements for the screening of the drugs. Electrochemical sensors and biosensors have several advantages such as low detection limits, a wide linear response range, good stability and reproducibility. Optical biosensors have several advantages such as direct, real-time and label-free detection of many biological and chemical substances, high specificity, sensitivity, small size and low cost. Modified electrodes enhance sensitivity of the electrodes to develop a new biosensor with desired features. Chemically modified electrodes have gained attention in drug analysis owing to low background current, wide potential window range, simple surface renewal, low detection limit and low cost. Modified electrodes produced by modifying of a solid surface electrode via different materials (carbonaceous materials, metal nanoparticles, polymer, biomolecules) immobilization. Recent advances in nanotechnology offer opportunities to design and construct biosensors. Unique features of nanomaterials provide many advantages in the fabrication of biosensors. Nanomaterials have controllable chemical structures, large surface to volume ratios, functional groups on their surface. To develop proteininorganic hybrid nanomaterials, four preparation methods have been used. These methods are immobilization, conjugation, crosslinking and self-assembly. In the present manuscript, applications of different biosensors, fabricated by using several materials, for drug analysis are reviewed. The biosensing strategies are investigated and discussed in detail.

Results:

Several analytical techniques such as chromatography, spectroscopy, radiometry, immunoassays and electrochemistry have been used for drug analysis and quantification. Methods based on chromatography require timeconsuming procedure, long sample-preparation steps, expensive instruments and trained staff. Compared to chromatographic methods, immunoassays have simple protocols and lower cost. Electrochemical measurements have many advantages over traditional chemical analyses and give information about drug quantity, metabolic fate of drugs, and pharmacological activity. Moreover, the electroanalytical methods are useful to determine drugs sensitively and selectivity. Additionally, these methods decrease analysis cost and require low-cost instruments and simple sample pretreatment steps.

Conclusion:

In recent years, drug analyses are performed using traditional techniques. These techniques have a good detection limit, but they have some limitations such as long analysis time, expensive device and experienced personnel requirement. Increased demand for practical and low-cost analytical techniques biosensor has gained interest for drug determinations in medical sciences. Biosensors are unique and successful devices when compared to traditional techniques. For drug determination, different electrode modification materials and different biorecognition elements are used for biosensor construction. Several biosensor construction strategies have been developed to enhance the biosensor performance. With the considerable progress in electrode surface modification, promotes the selectivity of the biosensor, decreases the production cost and provides miniaturization. In the next years, advances in technology will provide low cost, sensitive, selective biosensors for drug analysis in drug formulations and biological samples.

Advances in electrochemical immunosensors

Immunosensors are compact tools on which antibody and antigen interactions are formed. The specific interaction between antibody and antigen is detected by using a transducer and an electrical signal is measured. This specific interaction between these molecules makes immunosensor very attractive for several applications in different fields. Electrochemical immunosensors are successful devices in selective and sensitive detection of several analytes. Electrochemical transducing methods such as voltammetric, potentiometric, conductometric or impedimetric have been utilized in different applications due to their excellent properties such as being low-cost, sensitivity and simplicity. In this chapter, the fundamentals of electrochemical immunosensors are summarized and different applications in food, environmental and clinical analyses are investigated and discussed.

Electrochemical Biosensors as Potential Diagnostic Devices for Autoimmune Diseases

An important class of biosensors is immunosensors, affinity biosensors that are based on the specific interaction between antibodies and antigens. They are classified in four classes based on the type of employed transducer: electrochemical, optical, microgravimetric, and thermometric and depending on the type of recognition elements, antibodies, aptamers, microRNAs and recently peptides are integrating parts. Those analytical devices are able to detect peptides, antibodies and proteins in various sample matrices, without many steps of sample pretreatment. Their high sensitivity, low cost and the easy integration in point of care devices assuring portability are attracting features that justify the increasing interest in their development. The use of nanomaterials, simultaneous multianalyte detection and integration on platforms to form point-of-care devices are promising tools that can be used in clinical analysis for early diagnosis and therapy monitoring in several pathologies. Taking into account the growing incidence of autoimmune disease and the importance of early diagnosis, electrochemical biosensors could represent a viable alternative to currently used diagnosis methods. Some relevant examples of electrochemical assays for autoimmune disease diagnosis developed in the last several years based on antigens, antibodies and peptides as receptors were gathered and will be discussed further.

Ultrasensitive Immunosensor Array for TNF-α Detection in Artificial Saliva using Polymer-Coated Magnetic Microparticles onto Screen-Printed Gold Electrode

Tumor necrosis factor-α (TNF-α) is a biomarker of inflammation that occurs in patients suffering from heart failure (HF). Saliva can be sampled in a non-invasive way, and it is currently gaining importance as matrix alternative to blood in diagnostic and therapy monitoring. This work presents the development of an immunosensor array based on eight screen-printed gold electrodes to detect TNF-α in saliva samples. Two different functionalization strategies of electrodes were compared. In the first, anti-TNF-α antibodies were chemically bonded onto the electrode by functionalization with 4-carboxymethylaniline. The other functionalization procedure involved the binding of antibodies onto polymer-coated magnetic microparticles, which were then deposited onto the electrode by pulsed chronoamperometry. Finally, the chronoamperometry technique was applied to characterize the modified SPEAu. The use of a secondary antibody anti-TNF-α (Ab-TNF-α-HRP) labelled with horseradish peroxidase (HRP, 2 µg·mL⁻¹) was investigated using tetramethylbenzidine (TMB, pH = 3.75) as electrochemical substrate containing 0.2 mM of H₂O₂. A sandwich-type detection strategy with a secondary antibody anti-TNF-α provided chronoamperometric analyses in 10 s for each sample. Linearity, precision, limit of detection, and selectivity of devices were investigated. Interferences were evaluated by analyzing solutions containing other cytokine produced during the acute stage of inflammation. The immunosensor showed good performance within the clinically relevant concentration range, with a precision of 8%, and a limit of detection of 0.3 pg/mL. Therefore, it may represent a promising tool for monitoring HF in a non-invasive way.

Bioassay of saliva proteins: The best alternative for conventional methods in non-invasive diagnosis of cancer

Non-invasive diagnosis of cancer is often the key to effective treatment and patient survival. Saliva as a multi-constituent oral fluid comprises various disease signaling biomarkers, holds great potential for early-stage cancer diagnostics with cost-effective and easy collection, storage, transport and processing. Therefore, detection of biomarkers and proteins in the saliva samples is highly demand. The current review was performed using reliable internet database (mainly PubMed) to provide an overview of the most recent developments on non-invasive diagnosis of cancers in saliva and highlights main challenges and future prospects in sensing of the salivary biomarkers. The conventional detection methods of cancer biomarkers in saliva is discussed in the paper, however, the main focus is on non-invasive diagnosis of cancers in saliva using immunosensing (electrochemical, optical, piezoelectric), DNA based sensors, aptasensors and peptide based bio-assays The reviewed literature revealed that non-invasive cancer detection methods using the mentioned biosensors and without any processing of saliva sample offers a quick, sensitive, specific and cost effective analytical tool. Besides, salivary based detection methods can be used for simultaneous detection of panels of disease specific biomarkers in a real time manner or as home testing kits in near future.

Recent advances in designing nanomaterial based biointerfaces for electrochemical biosensing cardiovascular biomarkers

Early diagnosis of cardiovascular disease (CVD) is critically important for successful treatment and recovery of patients. At present, detection of CVD at early stages of its progression becomes a major issue for world health. The nanoscale electrochemical biosensors exhibit diverse outstanding properties, rendering them extremely suitable for the determination of CVD biomarkers at very low concentrations in biological fluids. The unique advantages offered by electrochemical biosensors in terms of sensitivity and stability imparted by nanostructuring the electrode surface together with high affinity and selectivity of bioreceptors have led to the development of new electrochemical biosensing strategies that have introduced as interesting alternatives to conventional methodologies for clinical diagnostics of CVD. This review provides an updated overview of selected examples during the period 2005-2018 involving electrochemical biosensing approaches and signal amplification strategies based on nanomaterials, which have been applied for determination of CVD biomarkers. The studied CVD biomarkers include AXL receptor tyrosine kinase, apolipoproteins, cholesterol, C-reactive protein (CRP), D-dimer, fibrinogen (Fib), glucose, insulin, interleukins, lipoproteins, myoglobin, N-terminal pro-B-type natriuretic peptide (BNP), tumor necrosis factor alpha (TNF-α) and troponins (Tns) on electrochemical transduction format. Identification of new specific CVD biomarkers, multiplex bioassay for the simultaneous determination of biomarkers, emergence of microfluidic biosensors, real-time analysis of biomarkers and point of care validation with high sensitivity and selectivity are the major challenges for future research.

Recent progress on the sensitive detection of cardiovascular disease markers by electrochemical-based biosensors

Cardiovascular disease is the most reason for deaths in all over the world. Hence, biomarkers of cardiovascular diseases are very crucial for diagnosis and management process. Biomarker detection demand is opened the important way in biosensor development field. Rapid, cheap, portable, precise, selective and sensitive biomarker sensing devices are needed at this point to detect and predict disease. A cardiac biomarker can be orderable as C-reactive protein, troponin I or T, myoglobin, tumor necrosis factor alpha, interleukin-6, interleukin-1, lipoprotein-associated phospholipase, low-density lipoprotein and myeloperoxidase. They are used for prediction of cardiovascular diseases. There are many methods for early diagnosis of cardiovascular diseases, but these have long time process and expensive devices. In recent studies, different biosensors have been developed to remove the problems in this field. Electrochemical devices and developed biosensors have many superiorities than others such as low cost, mobile, reliable, repeatable, need a little amount of solution. In this review, recent studies were presented as details for cardiovascular disease biomarkers detection using electrochemical methods.

Rapid and sensitive SERS detection of the cytokine tumor necrosis factor alpha (tnf-α) in a magnetic bead pull-down assay with purified and highly Raman-active gold nanoparticle clusters

Tumor necrosis factor alpha (TNF-α) is a cytokine with significance in early diagnosis of cardiovascular diseases, obesity and insulin resistance. We demonstrate the proof of concept for a rapid and sensitive detection of TNF-α using a magnetic bead pull-down assay in combination with surface-enhanced Raman scattering (SERS). The use of purified and highly SERS-active small clusters of gold nanoparticles (AuNP) provides the high sensitivity of the assay with a limit of detection of ca. 1 pg/mL. Continuous density gradient centrifugation was employed for separating the very bright silica-encapsulated AuNP dimers and trimers from the significantly weaker AuNP monomers. Negative control experiments with other cytokines (IL-6, IL-8) and bovine serum albumin (BSA) confirm the high specificity of the assay, but indicate also space for future improvements by further reducing non-specific binding between proteins and the SERS nanotags. The multiplexing potential of this SERS-based detection scheme is exemplarily demonstrated by using a set of three spectrally distinct and highly SERS-active AuNP clusters with unique spectral barcodes. Graphical abstract ᅟ.

An impedimetric immunosensor for highly sensitive detection of IL-8 in human serum and saliva samples: A new surface modification method by 6-phosphonohexanoic acid for biosensing applications

In this study, we fabricated a sensitive and label-free impedimetric immunosensor based on 6-phosphonohexanoic acid (PHA) modified ITO electrode for detection of interleukin-8 (IL-8) in human serum and saliva. PHA was first employed to cancer biomarker sensing platform. Anti-IL-8 antibody was used as a biorecognition element and the detection principle of this immunosensor was based on monitoring specific interaction between anti-IL-8 antibody and IL-8 antigen. The morphological characterization of each electrode modification step was analyzed by scanning electron microscopy (SEM), SEM-energy dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM) while electrochemical characterization was performed by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and single frequency impedance (SFI) techniques. Moreover, the antibody immobilization on the electrode surface was proved Fourier-transform infrared spectroscopy (FTIR) and Raman Spectroscopy. This proposed impedimetric immunosensor exhibited good performances with a wide linear in the range from 0.02 pg/mL to 3 pg/mL as well as a relative low detection limit of 6 fg/mL. The impedimetric immunosensor had a good specificity, stability and reproducibility. This study proved that PHA was a suitable interface material to fabricate an electrochemical biosensor.

Emerging Biosensing Technologies for Neuroinflammatory and Neurodegenerative Disease Diagnostics

Neuroinflammation plays a critical role in the onset and progression of many neurological disorders, including Multiple Sclerosis, Alzheimer's and Parkinson's diseases. In these clinical conditions the underlying neuroinflammatory processes are significantly heterogeneous. Nevertheless, a common link is the chronic activation of innate immune responses and imbalanced secretion of pro and anti-inflammatory mediators. In light of this, the discovery of robust biomarkers is crucial for screening, early diagnosis, and monitoring of neurological diseases. However, the difficulty to investigate biochemical processes directly in the central nervous system (CNS) is challenging. In recent years, biomarkers of CNS inflammatory responses have been identified in different body fluids, such as blood, cerebrospinal fluid, and tears. In addition, progress in micro and nanotechnology has enabled the development of biosensing platforms capable of detecting in real-time, multiple biomarkers in clinically relevant samples. Biosensing technologies are approaching maturity where they will become deployed in community settings, at which point screening programs and personalized medicine will become a reality. In this multidisciplinary review, our goal is to highlight both clinical and recent technological advances toward the development of multiplex-based solutions for effective neuroinflammatory and neurodegenerative disease diagnostics and monitoring.

Intracellular calcium ions and morphological changes of cardiac myoblasts response to an intelligent biodegradable conducting copolymer

A novel biodegradable conducting polymer, PLA-b-AP-b-PLA (PAP) triblock copolymer of poly (l-lactide) (PLA) and aniline pentamer (AP) with electroactivity and biodegradability, was synthesized and its potential application in cardiac tissue engineering was studied. The PAP copolymer presented better biocompatibility compared to PANi and PLA because of promoted cell adhesion and spreading of rat cardiac myoblasts (H9c2 cell line) on PAP/PLA thin film. After pulse electrical stimulation (5 V, 1 Hz, 500 ms) for 6 days, the proliferation ratio, and intracellular calcium concentration of H9c2 cells on PAP/PLA were improved significantly. Meanwhile, cell morphology changed by varying the pulse electrical signals. Especially, the oriented pseudopodia-like structure was observed from H9c2 cells on PAP/PLA after electrical stimulation. It is regarded that the novel conducting copolymer could enhance electronic signals transferring between cells because of its special electrochemical properties, which may result in the differentiation of cardiac myoblasts.

A label-free electrochemical biosensor for direct detection of RACK 1 by using disposable, low-cost and reproducible ITO based electrode

In this study we designed an ultrasensitive electrochemical immunosensor for RACK 1 detection using 11-cyanoundecyltrimethoxysilane (11-CUTMS) as a immobilization matrix to immobilize biorecognition element. The used silane agent (11-CUTMS) provides a favorable platform for efficient loading of anti-RACK 1 antibody. The effective loading of the biorecognition element on the 11-CUTMS matrix was monitored by scanning electron microscopy (SEM), atomic force microscopy (AFM) images and fourier transform infrared spectroscopy (FTIR) spectra. The electrochemical characterization of the immunosensor was performed by using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. Moreover, biorecognition interaction between anti-RACK1 antibodies and RACK1 antigens was monitored by using single frequency technique (SFI). The operating conditions, calibration curves obtained during optimization of experiments and reproducibility of the proposed impedimetric RACK1 biosensor are also investigated and discussed. The electrochemical immunosensor illustrated a sensitive response to RACK 1 antigen with detection limit of 10.8 fg/mL and in the linear range of 0.036-2.278 pg/mL (R² = 0.999). Owing to high specificity, good reproducibility, long stability and reusability, the fabricated immunosensor will provide a sensitive, selective approach to RACK 1 detection. Furthermore, the practical applicability in human serum samples were investigated with a satisfactory result.