Recent Progress in the Development of Conducting Polymer-Based Nanocomposites for Electrochemical Biosensors Applications: A Mini-Review

Harnessing Photo-Energy Conversion in Nanomaterials for Precision Theranostics

The rapidly advancing field of theranostics aims to integrate therapeutic and diagnostic functionalities into a single platform for precision medicine, enabling the simultaneous treatment and monitoring of diseases. Photo-energy conversion-based nanomaterials have emerged as a versatile platform that utilizes the unique properties of light to activate theranostics with high spatial and temporal precision. This review provides a comprehensive overview of recent developments in photo-energy conversion using nanomaterials, highlighting their applications in disease theranostics. The discussion begins by exploring the fundamental principles of photo-energy conversion in nanomaterials, including the types of materials used and various light-triggered mechanisms, such as photoluminescence, photothermal, photoelectric, photoacoustic, photo-triggered SERS, and photodynamic processes. Following this, the review delves into the broad spectrum of applications of photo-energy conversion in nanomaterials, emphasizing their role in the diagnosis and treatment of major diseases, including cancer, neurodegenerative disorders, retinal degeneration, and osteoarthritis. Finally, the challenges and opportunities of photo-energy conversion-based technologies for precision theranostics are discussed, aiming to advance personalized medicine.

Nanostructured conductive polymers: synthesis and application in biomedicine

Conductive polymers (CPs), distinguished by their sp2-hybridized carbon backbone, offer remarkable electrical conductivity while maintaining the advantageous mechanical flexibility and processing characteristics typical of organic polymers. Compared to their bulk counterparts, nanostructured CPs exhibit unique physicochemical properties, such as large surface areas and shortened charge/mass transport pathways, making them promising candidates for various applications. This mini review explores various synthesis methodologies for nanostructured CPs, including electrospinning, hard templating, and soft templating techniques, while elucidating their advantages and disadvantages. Additionally, the burgeoning biomedical applications of nanostructured CPs are highlighted, including drug delivery, neural electrodes and interfaces, nerve regeneration, and biosensing, demonstrating their potential to significantly advance contemporary biomedical science.

Combining WO3@AuNPs with Poly(amidoamine) Allows Sensitive Electrochemical Detection of DR1 Based on Dual Signal Amplification

Down-regulator of transcription 1 (DR1) is considered as a biomarker of hashimoto's thyroiditis (HT), which is a risk factor for thyroid cancer. Here, a label-free electrochemical biosensor for DR1 detection was constructed based on polyamidoamine (PAMAM) polymer and the nanocomposite (WO3@AuNPs) composed of tungsten trioxide (WO3) and gold nanoparticles (AuNPs). WO3@AuNPs was obtained by combining monolayer WO3 nanosheets, which has high conductivity, and AuNPs. The modification of WO3@AuNPs can not only increase the conductivity of the electrode but also provide more active sites for signaling units, thus greatly improve the sensitivity of the sensor. The polymer PAMAM is biocompatible and non-immunogenic, and its end functional group can bind to the target molecules, providing them with more binding sites and thus improving the sensitivity of the sensor. Under optimal conditions, the label-free biosensor showed a good linear relationship between the logarithm of DR1 concentration and the impedance in the range of 10 fg ⋅ mL-1 to 100 ng ⋅ mL-1, with a detection limit as low as 0.3 fg ⋅ mL-1. Besides, this label-free electrochemical platform exhibited satisfactory selectivity and anti-interference capability in human serum samples. Therefore, this method has considerable potential in clinical detection of DR1.

Biosensors for metastatic cancer cell detection

Early detection and effective cancer treatment are critical to improving metastatic cancer cell diagnosis and management today. In particular, accurate qualitative diagnosis of metastatic cancer cell represents an important step in the diagnosis of cancer. Today, biosensors have been widely developed due to the daily need to measure different chemical and biological species. Biosensors are utilized to quantify chemical and biological phenomena by generating signals that are directly proportional to the quantity of the analyte present in the reaction. Biosensors are widely used in disease control, drug delivery, infection detection, detection of pathogenic microorganisms, and markers that indicate a specific disease in the body. These devices have been especially popular in the field of metastatic cancer cell diagnosis and treatment due to their portability, high sensitivity, high specificity, ease of use and short response time. This article examines biosensors for metastatic cancer cells. It also studies metastatic cancer cells and the mechanism of metastasis. Finally, the function of biosensors and biomarkers in metastatic cancer cells is investigated.

Ultrasensitive, Label-Free Voltammetric Detection of Dibutyl Phthalate Based on Poly-l-lysine/poly(3,4-ethylenedioxythiophene)-porous Graphene Nanocomposite and Molecularly Imprinted Polymers

Development of an efficient technique for accurate and sensitive dibutyl phthalate (DBP) determination is crucial for food safety and environment protection. An ultrasensitive molecularly imprinted polymers (MIP) voltammetric sensor was herein engineered for the specific determination of DBP using poly-l-lysine/poly(3,4-ethylenedioxythiophene)/porous graphene nanocomposite (PLL/PEDOT-PG) and poly(o-phenylenediamine)-imprinted film as a label-free and sensing platform. Fabrication of PEDOT-PG nanocomposites was achieved through a simple liquid-liquid interfacial polymerization. Subsequently, poly-l-lysine (PLL) functionalization was employed to enhance the dispersibility and stability of the prepared PEDOT-PG, as well as promote its adhesion on the sensor surface. In the presence of DBP, the imprinted poly(o-phenylenediamine) film was formed on the surface of PLL/PEDOT-PG. Investigation of the physical properties and electrochemical behavior of the MIP/PLL/PEDOT-PG indicates that the incorporation of PG into PEDOT, with PLL uniformly wrapping its surface, significantly enhanced conductivity, carrier mobility, stability, and provided a larger surface area for specific recognition sites. Under optimal experimental conditions, the electrochemical response exhibited a linear relationship with a logarithm of DBP concentration within the range of 1 fM to 5 µM, with the detection limit as low as 0.88 fM. The method demonstrated exceptional stability and repeatability and has been successfully applied to quantify DBP in plastic packaging materials.

Progress in Treatment and Diagnostics of Infectious Disease with Polymers

In this era of advanced technology and innovation, infectious diseases still cause significant morbidity and mortality, which need to be addressed. Despite overwhelming success in the development of vaccines, transmittable diseases such as tuberculosis and AIDS remain unprotected, and the treatment is challenging due to frequent mutations of the pathogens. Formulations of new or existing drugs with polymeric materials have been explored as a promising new approach. Variations in shape, size, surface charge, internal morphology, and functionalization position polymer particles as a revolutionary material in healthcare. Here, an overview is provided of major diseases along with statistics on infection and death rates, focusing on polymer-based treatments and modes of action. Key issues are discussed in this review pertaining to current challenges and future perspectives.

Detection of SARS-CoV-2 Spike Protein Using Micropatterned 3D Poly(3,4-Ethylenedioxythiophene) Nanorods Decorated with Gold Nanoparticles

The sensitivity and fabrication process of the detection platform are important for developing viral disease diagnosis. Recently, the outbreak of SARS-CoV-2 compelled us to develop a new detection platform to control such diseases in the future. We present an electrochemical-based assay that employs the unique properties of gold nanoparticles (AuNPs) deposited on 3D carboxyl-functionalized poly(3,4-ethylenedioxythiophene) (PEDOTAc) nanorods for specific and sensitive detection of SARS-CoV-2 spike protein (S1). The 3D-shaped PEDOTAc nanorods offer an ample surface area for receptor immobilization grown on indium-tin oxide surfaces through transfer-printing technology. Characterization via electrochemical, fluorescence, X-ray photoelectron spectroscopy, and scanning electron microscopy techniques confirmed the structural and morphological properties of the AuNPs-decorated PEDOTAc. In contrast to antibody-based assays, our platform employs ACE2 receptors for spike protein binding. Differential pulse voltammetry records current responses, showing linear sensitivity from 100 ng to 10 pg/mL of S1. In addition, the SARS-CoV-2 assay (CoVPNs) also exhibited excellent selectivity against nonspecific target proteins (H9N2, IL-6, and Escherichia coli). Furthermore, the developed surface maintained good stability for up to 7 consecutive days without losing performance. The results provide new insight into effective 3D conductive nanostructure formation, which is promising in the development of versatile sensory devices.

Development and Analytical Evaluation of a Point-of-Care Electrochemical Biosensor for Rapid and Accurate SARS-CoV-2 Detection

The COVID-19 pandemic has underscored the critical need for rapid and accurate screening and diagnostic methods for potential respiratory viruses. Existing COVID-19 diagnostic approaches face limitations either in terms of turnaround time or accuracy. In this study, we present an electrochemical biosensor that offers nearly instantaneous and precise SARS-CoV-2 detection, suitable for point-of-care and environmental monitoring applications. The biosensor employs a stapled hACE-2 N-terminal alpha helix peptide to functionalize an in situ grown polypyrrole conductive polymer on a nitrocellulose membrane backbone through a chemical process. We assessed the biosensor's analytical performance using heat-inactivated omicron and delta variants of the SARS-CoV-2 virus in artificial saliva (AS) and nasal swab (NS) samples diluted in a strong ionic solution, as well as clinical specimens with known Ct values. Virus identification was achieved through electrochemical impedance spectroscopy (EIS) and frequency analyses. The assay demonstrated a limit of detection (LoD) of 40 TCID50/mL, with 95% sensitivity and 100% specificity. Notably, the biosensor exhibited no cross-reactivity when tested against the influenza virus. The entire testing process using the biosensor takes less than a minute. In summary, our biosensor exhibits promising potential in the battle against pandemic respiratory viruses, offering a platform for the development of rapid, compact, portable, and point-of-care devices capable of multiplexing various viruses. The biosensor has the capacity to significantly bolster our readiness and response to future viral outbreaks.

Molecularly Imprinted Polymer-Based Electrochemical Sensors for the Diagnosis of Infectious Diseases

The appearance of biological molecules, so-called biomarkers in body fluids at abnormal concentrations, is considered a good tool for detecting disease. Biomarkers are usually looked for in the most common body fluids, such as blood, nasopharyngeal fluids, urine, tears, sweat, etc. Even with significant advances in diagnostic technology, many patients with suspected infections receive empiric antimicrobial therapy rather than appropriate treatment, which is driven by rapid identification of the infectious agent, leading to increased antimicrobial resistance. To positively impact healthcare, new tests are needed that are pathogen-specific, easy to use, and produce results quickly. Molecularly imprinted polymer (MIP)-based biosensors can achieve these general goals and have enormous potential for disease detection. This article aimed to overview recent articles dedicated to electrochemical sensors modified with MIP to detect protein-based biomarkers of certain infectious diseases in human beings, particularly the biomarkers of infectious diseases, such as HIV-1, COVID-19, Dengue virus, and others. Some biomarkers, such as C-reactive protein (CRP) found in blood tests, are not specific for a particular disease but are used to identify any inflammation process in the body and are also under consideration in this review. Other biomarkers are specific to a particular disease, e.g., SARS-CoV-2-S spike glycoprotein. This article analyzes the development of electrochemical sensors using molecular imprinting technology and the used materials' influence. The research methods, the application of different electrodes, the influence of the polymers, and the established detection limits are reviewed and compared.

Biomedical applications of biodegradable polycaprolactone-functionalized magnetic iron oxides nanoparticles and their polymer nanocomposites

Magnetic nanoparticles (MNPs) have gained significant attention among several nanoscale materials during the last decade due to their unique properties. These properties make them successful nanofillers for drug delivery and a number of new biomedical applications. MNPs are more useful when combined with biodegradable polymers. In this review, we discussed the synthesis of polycaprolactones (PCL) and the various methods of synthesizing magnetic iron oxide nanoparticles. Then, the synthesis of composites that is made of PCL and magnetic materials (with special focus on iron oxide nanoparticles) were highlighted. In addition, we comprehensively reviewed their application in drug delivery, cancer treatment, wound healing, hyperthermia, and bone tissue engineering. Other biomedical applications of the magnetic PCL such as mitochondria targeting are highlighted. Moreover, biomedical applications of magnetic nanoparticles incorporated into other synthetic polymers apart from PCL are also discussed. Thus, great progress and better outcome with functionalized MNPs enhanced with polycaprolactone has been recorded with the biomedical applications of drug delivery and recovery of bone tissues.

Nanoporous Conducting Polymer Nanowire Network-Encapsulated MnO2-Based Flexible Supercapacitor with Enhanced Rate Capability and Cycling Stability

Transition-metal-oxide-based electrochemical electrodes usually suffer from poor electron and ion transport, leading to deteriorated rate performance and cycling stability. Herein, we address these issues by developing a facile "conducting encapsulation" strategy toward a nanoporous PEDOT nanowire/MnO₂ nanoparticle/PEDOT nanowire composite electrode. Through encapsulation of the PEDOT nanowire network, the overall electrochemical performance of the resultant composite electrode is substantially enhanced. Specifically, the rate capability and capacitance retention are improved by ∼48.2 and ∼33%, respectively, which are 89.8% at 0.8-40 mA/cm² and 93% after 3000 charge/discharge cycles at 2.0 mA/cm², respectively. Moreover, the specific capacitance is increased by ∼6 times of that of the MnO₂@PEDOT NW electrode at ∼200 mA/cm². We find that a nanoporous conducting nanowire network that encapsulates a MnO₂ nanoparticle layer can provide efficient electron and ion transport paths and stabilize the structure of MnO₂ from collapse during charge/discharge cycling and mechanical deformation. This strategy can be applied to other pseudocapacitive material-based electrochemical electrodes, such as transition-metal oxides and conducting polymers.

Micro/Nano-Fabrication of Flexible Poly(3,4-Ethylenedioxythiophene)-Based Conductive Films for High-Performance Microdevices

With the increasing demands for novel flexible organic electronic devices, conductive polymers are now becoming the rising star for reaching such targets, which has witnessed significant breakthroughs in the fields of thermoelectric devices, solar cells, sensors, and hydrogels during the past decade due to their outstanding conductivity, solution-processing ability, as well as tailorability. However, the commercialization of those devices still lags markedly behind the corresponding research advances, arising from the not high enough performance and limited manufacturing techniques. The conductivity and micro/nano-structure of conductive polymer films are two critical factors for achieving high-performance microdevices. In this review, the state-of-the-art technologies for developing organic devices by using conductive polymers are comprehensively summarized, which will begin with a description of the commonly used synthesis methods and mechanisms for conductive polymers. Next, the current techniques for the fabrication of conductive polymer films will be proffered and discussed. Subsequently, approaches for tailoring the nanostructures and microstructures of conductive polymer films are summarized and discussed. Then, the applications of micro/nano-fabricated conductive films-based devices in various fields are given and the role of the micro/nano-structures on the device performances is highlighted. Finally, the perspectives on future directions in this exciting field are presented.

Molecularly imprinted polymers for the recognition of biomarkers of certain neurodegenerative diseases

The appearance of the biomarkers in body fluids like blood, urine, saliva, tears, etc. can be used for the identification of many diseases. This article aimed to summarize the studies about electrochemical biosensors with molecularly imprinted polymers as sensitive and selective layers on the electrode to detect protein-based biomarkers of such neurodegenerative diseases as Alzheimer's disease, Parkinson's disease, and stress. The main attention in this article is focused on the detection methods of amyloid-β oligomers and p-Tau which are representative biomarkers for Alzheimer's disease, α-synuclein as the biomarker of Parkinson's disease, and α-amylase and lysozyme as the biomarkers of stress using molecular imprinting technology. The research methods, the application of different electrodes, the influence of the polymers, and the established detection limits are reviewed and compared.

Molecularly Imprinted Polymers for the Determination of Cancer Biomarkers

Biomarkers can provide critical information about cancer and many other diseases; therefore, developing analytical systems for recognising biomarkers is an essential direction in bioanalytical chemistry. Recently molecularly imprinted polymers (MIPs) have been applied in analytical systems to determine biomarkers. This article aims to an overview of MIPs used for the detection of cancer biomarkers, namely: prostate cancer (PSA), breast cancer (CA15-3, HER-2), epithelial ovarian cancer (CA-125), hepatocellular carcinoma (AFP), and small molecule cancer biomarkers (5-HIAA and neopterin). These cancer biomarkers may be found in tumours, blood, urine, faeces, or other body fluids or tissues. The determination of low concentrations of biomarkers in these complex matrices is technically challenging. The overviewed studies used MIP-based biosensors to assess natural or artificial samples such as blood, serum, plasma, or urine. Molecular imprinting technology and MIP-based sensor creation principles are outlined. Analytical signal determination methods and the nature and chemical structure of the imprinted polymers are discussed. Based on the reviewed biosensors, the results are compared, and the most suitable materials for each biomarker are discussed.

2D carbon materials based photoelectrochemical biosensors for detection of cancer antigens

Cancer is a leading cause of death globally and early diagnosis is of paramount importance for identifying appropriate treatment pathways to improve cancer patient survival. However, conventional methods for cancer detection such as biopsy, CT scan, magnetic resonance imaging, endoscopy, X-ray and ultrasound are limited and not efficient for early cancer detection. Advancements in molecular technology have enabled the identification of various cancer biomarkers for diagnosis and prognosis of the deadly disease. The detection of these biomarkers can be done by biosensors. Biosensors are less time consuming compared to conventional methods and has the potential to detect cancer at an earlier stage. Compared to conventional biosensors, photoelectrochemical (PEC) biosensors have improved selectivity and sensitivity and is a suitable tool for detecting cancer agents. Recently, 2D carbon materials have gained interest as a PEC sensing platform due to their high surface area and ease of surface modifications for improved electrical transfer and attachment of biorecognition elements. This review will focus on the development of 2D carbon nanomaterials as electrode platform in PEC biosensors for the detection of cancer biomarkers. The working principles, biorecognition strategies and key parameters that influence the performance of the biosensors will be critically discussed. In addition, the potential application of PEC biosensor in clinical settings will also be explored, providing insights into the future perspective and challenges of exploiting PEC biosensors for cancer diagnosis.

Nanomaterial-based electrochemical enzymatic biosensors for recognizing phenolic compounds in aqueous effluents

With the rapid development of industrial society, phenolic pollutants already identified in water are severe threats to human health. Traditional detection techniques like chromatography are poor in the ability of cost-effectiveness and on-site detection. In recent years, electrochemical enzymatic biosensors have attracted increasing attention for use in the recognition of phenolic compounds, which is considered an effective strategy for the product transfer of portable analytical devices. Although electrochemical enzymatic biosensors provide a fast, accurate on-site detection technique, the difficulties of enzyme deactivation, poor stability and low sensitivity remain to be solved. Thus, effective immobilization methods of enzymes and nanomaterials with excellent properties have been extensively researched to obtain a high-sensitivity and high-stability biosensing platform. Simultaneous detection of multiple phenols may become the focus of further research. In this review, we provide an overview of recent progress toward electrochemical enzymatic biosensors for the detection of phenolic compounds, including enzyme immobilization approaches and advanced nanomaterials, especially nanocomposites with attractive properties such as good conductivity, high specific surface area, and porous structure. We will comprehensively discuss the features and mechanisms of the main enzymes adopted in the construction of different phenolic biosensors, as well as traditional methods (e.g., adsorption, covalent bonding, entrapment, encapsulation, cross-linking) of enzyme immobilization. The most effective method is based on the properties of enzymes, supports and application objective because there is no one-size-fits-all method of enzymatic immobilization. The emphasis will be given to various advanced nanomaterials, including their special nanostructures, preparation methods and performance. Finally, the main challenges in future research on electrochemical phenolic biosensors will be discussed to provide further perspectives for practical applications in dynamic and on-site monitoring. We believe this review will deliver an important inspiration for the construction of novel and high-performance electrochemical biosensors from enzyme selection to nanomaterial design for the detection of various hazardous materials. We believe this review will deliver an important inspiration on the construction of novel and high-performance electrochemical biosensors from the enzyme selection to the nanomaterial design for detections of various hazardous materials.

Conjugated Polymers-Based Biosensors for Virus Detection: Lessons from COVID-19

Human beings continue to endure the coronavirus disease (COVID-19) pandemic, which has spread throughout the world and significantly affected all countries and territories, causing a socioeconomic crunch. Human pathogenic viruses are considered a global burden for public health, both in the present and the future. Therefore, the early and accurate diagnosis of viruses has been and still is critical and should be accorded a degree of priority that is equivalent to vaccinations and drugs. We have opened a Special Issue titled "Conjugated polymers-based biosensors for virus detection". This editorial seeks to emphasize the importance and potential of conjugated polymers in the design and development of biosensors. Furthermore, we briefly provide an overview, scientific evidence, and opinions on promising strategies for the development of CP-based electrochemical biosensors for virus detection.

Heavy Metal Ions Detection Using Nanomaterials-Based Aptasensors

Heavy metals ions as metallic pollutants are a growing global issue due to their adverse effects on the aquatic ecosystem, and human health. Unfortunately, conventional detection methods such as atomic absorption spectrometry exhibit a relatively low limit of detection and hold numerous disadvantages, and therefore, the development of an efficient method for in-situ and real-time detection of heavy metal residues is of great importance. The aptamer-based sensors offer distinct advantages over antibodies and emerged as a robust sensing platform against various heavy metals due to their high sensitivity, ease of production, simple operations, excellent specificity, better stability, low immunogenicity, and cost-effectiveness. The nucleic acid aptamers in conjugation with nanomaterials can bind to the metal ions with good specificity/selectivity and can be used for on-site monitoring of metal ion residues. This review aimed to provide background information about nanomaterials-based aptasensor, recent advancements in aptamer conjunction on nanomaterials surface, the role of nanomaterials in improving signal transduction, recent progress of nanomaterials-based aptasening procedures (from 2010 to 2022), and future perspectives toward the practical applications of nanomaterials-based aptasensors against hazardous metal ions for food safety and environmental monitoring.

Development of molecularly imprinted polymer based phase boundaries for sensors design (review)

Achievements in polymer chemistry enables to design artificial phase boundaries modified by imprints of selected molecules and some larger structures. These structures seem very useful for the design of new materials suitable for affinity chromatography and sensors. In this review, we are overviewing the synthesis of molecularly imprinted polymers (MIPs) and the applicability of these MIPs in the design of affinity sensors. Such MIP-based layers or particles can be used as analyte-recognizing parts for sensors and in some cases they can replace very expensive compounds (e.g.: antibodies, receptors etc.), which are recognizing analyte. Many different polymers can be used for the formation of MIPs, but conducing polymers shows the most attractive capabilities for molecular-imprinting by various chemical compounds. Therefore, the application of conducting polymers (e.g.: polypyrrole, polyaniline, polythiophene, poly(3,4-ethylenedioxythiophene), and ortho-phenylenediamine) seems very promising. Polypyrrole is one of the most suitable for the development of MIP-based structures with molecular imprints by analytes of various molecular weights. Overoxiation of polypyrrole enables to increase the selectivity of polypyrrole-based MIPs. Methods used for the synthesis of conducting polymer based MIPs are overviewed. Some methods, which are applied for the transduction of analytical signal, are discussed, and challenges and new trends in MIP-technology are foreseen.

Modeling of the Electrotransport Process in PP-Based and PLA-Based Composite Fibers Filled with Carbon Nanofibers

Polypropylene and polylactide-based composite fibers have been produced by a melt technology. Long vapor-grown carbon fibers (CNFs) have been used as electrical conductivity fillers. It is clearly shown by experimental methods that the CNFs are evenly distributed in the polymer matrix, orienting themselves along the direction of fiber extrusion and retaining their initial dimensions. It is shown that for composites fibers based on crystallizing (polypropylene) and amorphous (polylactide acid) polymer matrix, the dependence of electrical resistance on the filler concentration is percolation character and can be described as a double Boltzmann function. Four sections are identified on the dependences of the electrical resistance on the filler concentration for composite fibers, and the reasons for this character of this dependence on the formation of electrically conductive circuits are analyzed. Investigated in this work are the PP-based and PLA-based composites filled with carbon nanofibers that can be used as antistatic, shielding materials, or as sensors.

Development of polypyrrole (nano)structures decorated with gold nanoparticles toward immunosensing for COVID-19 serological diagnosis

The rapid and reliable detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) seroconversion in humans is crucial for suitable infection control. In this sense, many studies have focused on increasing the sensibility, lowering the detection limits and minimizing false negative/positive results. Thus, biosensors based on nanoarchitectures of conducting polymers are promising alternatives to more traditional materials since they can hold improved surface area, higher electrical conductivity and electrochemical activity. In this work, we reported the analytical comparison of two different conducting polymers morphologies for the development of an impedimetric biosensor to monitor SARS-CoV-2 seroconversion in humans. Biosensors based on polypyrrole (PPy), synthesized in both globular and nanotubular (NT) morphology, and gold nanoparticles are reported, using a self-assembly monolayer of 3-mercaptopropionic acid and covalently linked SARS-CoV-2 Nucleocapsid protein. First, the novel hybrid materials were characterized by electron microscopy and electrochemical measurements, and the biosensor step-by-step construction was characterized by electrochemical and spectroscopic techniques. As a proof of concept, the biosensor was used for the impedimetric detection of anti-SARS-CoV-2 Nucleocapsid protein monoclonal antibodies. The results showed a linear response for different antibody concentrations, good sensibility and possibility to quantify 7.442 and 0.4 ng/mL of monoclonal antibody for PPy in the globular and NT morphology, respectively. The PPy-NTs biosensor was able to discriminate serum obtained from COVID-19 positive versus negative clinical samples and is a promising tool for COVID-19 immunodiagnostic, which can contribute to further studies concerning rapid, efficient, and reliable detections.

Electrochemical Methods for the Analysis of Milk

The milk and dairy industries are some of the most profitable sectors in many countries. This business requires close control of product quality and continuous testing to ensure the safety of the consumers. The potential risk of contaminants or degradation products and undesirable chemicals necessitates the use of fast, reliable detection tools to make immediate production decisions. This review covers studies on the application of electrochemical methods to milk (i.e., voltammetric and amperometric) to quantify different analytes, as reported over the last 10 to 15 years. The review covers a wide range of analytes, including allergens, antioxidants, organic compounds, nitrogen- and aldehyde containing compounds, biochemicals, heavy metals, hydrogen peroxide, nitrite, and endocrine disruptors. The review also examines pretreatment procedures applied to milk samples and the use of novel sensor materials. Final perspectives are provided on the future of cost-effective and easy-to-use electrochemical sensors and their advantages over conventional methods.

Electrochemically Deposited Molecularly Imprinted Polymer-Based Sensors

This review is dedicated to the development of molecularly imprinted polymers (MIPs) and the application of MIPs in sensor design. MIP-based biological recognition parts can replace receptors or antibodies, which are rather expensive. Conducting polymers show unique properties that are applicable in sensor design. Therefore, MIP-based conducting polymers, including polypyrrole, polythiophene, poly(3,4-ethylenedioxythiophene), polyaniline and ortho-phenylenediamine are frequently applied in sensor design. Some other materials that can be molecularly imprinted are also overviewed in this review. Among many imprintable materials conducting polymer, polypyrrole is one of the most suitable for molecular imprinting of various targets ranging from small organics up to rather large proteins. Some attention in this review is dedicated to overview methods applied to design MIP-based sensing structures. Some attention is dedicated to the physicochemical methods applied for the transduction of analytical signals. Expected new trends and horizons in the application of MIP-based structures are also discussed.

The influence of physicochemical properties on the processibility of conducting polymers: A bioelectronics perspective

Conducting polymers (CPs) possess unique electrical and electrochemical properties and hold great potential for different applications in the field of bioelectronics. However, the widespread implementation of CPs in this field has been critically hindered by their poor processibility. There are four key elements that determine the processibility of CPs, which are thermal tunability, chemical stability, solvent compatibility and mechanical robustness. Recent research efforts have focused on enhancing the processibility of these materials through pre- or post-synthesis chemical modifications, the fabrication of CP-based complexes and composites, and the adoption of additive manufacturing techniques. In this review, the physicochemical and structural properties that underlie the performance and processibility of CPs are examined. In addition, current research efforts to overcome technical limitations and broaden the potential applications of CPs in bioelectronics are discussed. STATEMENT OF SIGNIFICANCE: This review details the inherent properties of CPs that have hindered their use in additive manufacturing for the creation of 3D bioelectronics. A fundamental approach is presented with consideration of the chemical structure and how this contributes to their electrical, thermal and mechanical properties. The review then considers how manipulation of these properties has been addressed in the literature including areas where improvements can be made. Finally, the review details the use of CPs in additive manufacturing and the future scope for the use of CPs and their composites in the development of 3D bioelectronics.

PEDOT-AuNPs-based impedimetric immunosensor for the detection of SARS-CoV-2 antibodies

Electrochemical sensors and biosensors are useful techniques for fast, inexpensive, sensitive, and easy detection of innumerous specimen. In face of COVID-19 pandemic, it became evident the necessity of a rapid and accurate diagnostic test, so the impedimetric immunosensor approach can be a good alternative to replace the conventional tests due to the specific antibody-antigen binding interaction and the fast response in comparison to traditional methods. In this work, a modified electrode with electrosynthesized PEDOT and gold nanoparticles followed by the immobilization of truncated nucleoprotein (N aa160-406aa) was used for a fast and reliable detection of antibodies against COVID-19 in human serum sample. The method consists in analyzing the charge-transfer resistance (R_CT) variation before and after the modified electrode comes into contact with the positive and negative serum sample for COVID-19, using [Fe(CN)₆]^3-/4- as a probe. The results show a linear and selective response for serum samples diluted in a range of 2.5 × 10³ to 20 × 10³. Also, the electrode material was fully characterized by Raman spectroscopy, transmission electron microscopy and scanning electron microscopy coupled with EDS, indicating that the gold nanoparticles were well distributed around the polymer matrix and the presence of the biological sample was confirmed by EDS analysis. EIS measurements allowed to differentiate the negative and positive samples by the difference in the R_CT magnitude, proving that the material developed here has potential properties to be applied in impedimetric immunosensors for the detection of SARS-CoV-2 antibodies in about 30 min.

In Vivo Monitoring of pH in Subacute PD Mouse Brains with a Ratiometric Electrochemical Microsensor Based on Poly(melamine) Films

In vivo monitoring of cerebral pH is of great significance because its disturbance is related to some pathological processes such as neurodegenerative diseases, for example, Parkinson's disease (PD). In this study, we developed an electrochemical microsensor based on poly(melamine) (P_Mel) films for ratiometric monitoring of pH in subacute PD mouse brains. In this microsensor, P_Mel films were prepared from a simple electropolymerization approach in a melamine-containing solution, serving as the selective pH recognition membrane undergoing a 2H⁺/2e^- process. Meanwhile, electrochemically oxidized graphene oxide (EOGO) produced a built-in correction signal which helped avoid the environmental interference of the complicated brain systems. The potential difference between the peaks generated from EOGO and P_Mel gradually decreased with the aqueous pH increasing from 4.0 to 9.0, constituting the detection foundation of the ratiometric electrochemical microsensor (REM). The in vitro studies demonstrated that this proposed method exhibited a high sensitivity (a Nernstian response of -61.35 mV/pH) and remarkable selectivity against amino acids, anions, cations, and biochemical and reactive oxygen species coexisting in the brain. Coupled with its excellent stability and reproducibility and good antibiofouling based on short-term detection, the developed REM could serve as a disposable sensor for the determination of cerebral pH in vivo. Its following successful application in the real-time measurement of pH in the striatum, hippocampus, and cortex of rat brains in the events of global cerebral ischemia/reperfusion verified the reliability of this method. Finally, we adopted this robust REM to systematically analyze and compare the average pH in different regions of normal and subacute PD mouse brains.

Fabrication of Polyaniline Ni-Complex Catalytic Electrode by Plasma Deposition for Electrochemical Detection of Phosphate through Glucose Redox Reaction as Mediator

We report here the preparation and characterization of polyaniline Ni-complex catalytic electrode by one-pot plasma deposition for the electrochemical detection of phosphate via the redox reaction of glucose. We first prepared a precursory solution by combining NiCl2 and 3-aminobenzoic acid in a mixed solution of methanol (MeOH) and water, and adding aniline as a conductive polymeric precursor for increasing the electron transfer potential. We then synthesized the catalytic electrode in a one-step cold plasma process by preparing the precursors on ITO glass. We characterized the obtained Ni-coordinate catalytic electrode via X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (SEM), and electrochemical methods. Electrochemical characterization produced stable redox properties of Ni3+/Ni2+ couples in a 0.1 M NaOH solution. Cyclic voltametric experiments have drastically increased electrocatalytic oxidation and reduction of glucose by increasing the concentration of phosphate (PO43−) ions using the prepared Ni-modified catalytic electrodes. From these results, the prepared catalytic electrode could be used as the electrochemical sensor for phosphate in actual water.

Sexual pheromone detection using PANI·Ag nanohybrid and PANI/PSS nanocomposite nanosensors

In this study, polyaniline/poly(styrene sulfonate) (PANI/PSS) nanocomposite and polyaniline·silver (PANI·Ag) nanohybrid thin films were obtained in cantilever nanosensors surface. The developed films were characterized in relation to topography, roughness, thickness, height, and structural properties. The topography study revealed that both films have a globular morphology, thickness and height in nanoscale. The gas sensing performance was investigated for sexual pheromone from the neotropical brown stink bug, Euschistus heros (F.). The sensitivities of both nanosensors based on PANI/PSS nanocomposite and PANI·Ag nanohybrid films were similar. The PANI·Ag nanohybrid nanosensor had a limit of detection of less than 3.1 ppq and limit of quantification of 10.05 ppq. The nanosensor layers were analyzed by UV-vis and FTIR showing the incorporation of Ag nanoparticles in the nanohybrid. We found that pheromone compound was adsorbed in sensing layer resulting in a reduction in the resonance frequency. The detection mechanism help us understand the good results of LOD, LOQ, sensitivity, selectivity and repeatability. The presented device has great potential for detection of the sexual pheromone from E. heros.

Ionic Liquid Electrolytes for Electrochemical Energy Storage Devices

For decades, improvements in electrolytes and electrodes have driven the development of electrochemical energy storage devices. Generally, electrodes and electrolytes should not be developed separately due to the importance of the interaction at their interface. The energy storage ability and safety of energy storage devices are in fact determined by the arrangement of ions and electrons between the electrode and the electrolyte. In this paper, the physicochemical and electrochemical properties of lithium-ion batteries and supercapacitors using ionic liquids (ILs) as an electrolyte are reviewed. Additionally, the energy storage device ILs developed over the last decade are introduced.

Development strategies of conducting polymer-based electrochemical biosensors for virus biomarkers: Potential for rapid COVID-19 detection

Rapid, accurate, portable, and large-scale diagnostic technologies for the detection of severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) are crucial for controlling the coronavirus disease (COVID-19). The current standard technologies, i.e., reverse-transcription polymerase chain reaction, serological assays, and computed tomography (CT) exhibit practical limitations and challenges in case of massive and rapid testing. Biosensors, particularly electrochemical conducting polymer (CP)-based biosensors, are considered as potential alternatives owing to their large advantages such as high selectivity and sensitivity, rapid detection, low cost, simplicity, flexibility, long self-life, and ease of use. Therefore, CP-based biosensors can serve as multisensors, mobile biosensors, and wearable biosensors, facilitating the development of point-of-care (POC) systems and home-use biosensors for COVID-19 detection. However, the application of these biosensors for COVID-19 entails several challenges related to their degradation, low crystallinity, charge transport properties, and weak interaction with biomarkers. To overcome these problems, this study provides scientific evidence for the potential applications of CP-based electrochemical biosensors in COVID-19 detection based on their applications for the detection of various biomarkers such as DNA/RNA, proteins, whole viruses, and antigens. We then propose promising strategies for the development of CP-based electrochemical biosensors for COVID-19 detection.

Interference-free electrocatalysis of p-chloro meta xylenol (PCMX) on uniquely designed optimized polymeric nanohybrid of P(EDOT-co-OPD) and fMWCNT modified glassy carbon electrode

p-Chloro-meta-Xylenol (PCMX) is an environmentally hazardous phenolic compound having biocidal and antiseptic activity. Very few research publications addressed monitoring this contaminant. This paper presents a rapid sensing system to quantify it in waste water samples. The electrochemical activity of PCMX was exploited through a unique polymeric nanocomposite modified transducer for its quantification. Poly[(3,4-Ethylenedioxythiophene)-co-(o-phenylenediamine)] [P(EDOT-co-OPD)] was deposited through one-step electropolymerization technique on the glassy carbon electrode (GCE) modified by functionalized multi-wall carbon nanotubes (fMWCNTs). An optimized combination of these constituents was evaluated using response surface methodology (RSM) based Box-Behnken experimental design. This maximized the response for PCMX using differential pulse voltammetry (DPV). The sensing matrix was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The structural and morphological study of the modified film was conducted by Fourier transform-infrared spectroscopy (FT-IR), Raman spectroscopy, scanning electron microscopy (SEM), and field emission scanning electron microscope (FESEM). The anodic peak current could be read from a wide range of 0.5-225 μM calibration curve with a detection limit of 0.2545 μmol L^-1. Interestingly this work did not use any biomaterial in the modification but achieved interference-free response with excellent selectivity, sensitivity (0.4668 μA μM^-1 cm^-2), reproducibility (RSD = 2.2%), and repeatability. The sensing platform showed good stability (85.7%) of 3 months even after 150 times repetitive use. Its applicability for real samples was established by good correlation with standard methods.

Laccase and Tyrosinase Biosensors Used in the Determination of Hydroxycinnamic Acids

In recent years, researchers have focused on developing simple and efficient methods based on electrochemical biosensors to determine hydroxycinnamic acids from various real samples (wine, beer, propolis, tea, and coffee). Enzymatic biosensors represent a promising, low-cost technology for the direct monitoring of these biologically important compounds, which implies a fast response and simple sample processing procedures. The present review aims at highlighting the structural features of this class of compounds and the importance of hydroxycinnamic acids for the human body, as well as presenting a series of enzymatic biosensors commonly used to quantify these phenolic compounds. Enzyme immobilization techniques on support electrodes are very important for their stability and for obtaining adequate results. The following sections of this review will briefly describe some of the laccase (Lac) and tyrosinase (Tyr) biosensors used for determining the main hydroxycinnamic acids of interest in the food or cosmetics industry. Considering relevant studies in the field, the fact has been noticed that there is a greater number of studies on laccase-based biosensors as compared to those based on tyrosinase for the detection of hydroxycinnamic acids. Significant progress has been made in relation to using the synergy of nanomaterials and nanocomposites for more stable and efficient enzyme immobilization. These nanomaterials are mainly carbon- and/or polymer-based nanostructures and metallic nanoparticles which provide a suitable environment for maintaining the biocatalytic activity of the enzyme and for increasing the rate of electron transport.

Advances in Molecularly Imprinted Polymers Based Affinity Sensors (Review)

Recent challenges in biomedical diagnostics show that the development of rapid affinity sensors is very important issue. Therefore, in this review we are aiming to outline the most important directions of affinity sensors where polymer-based semiconducting materials are applied. Progress in formation and development of such materials is overviewed and discussed. Some applicability aspects of conducting polymers in the design of affinity sensors are presented. The main attention is focused on bioanalytical application of conducting polymers such as polypyrrole, polyaniline, polythiophene and poly(3,4-ethylenedioxythiophene) ortho-phenylenediamine. In addition, some other polymers and inorganic materials that are suitable for molecular imprinting technology are also overviewed. Polymerization techniques, which are the most suitable for the development of composite structures suitable for affinity sensors are presented. Analytical signal transduction methods applied in affinity sensors based on polymer-based semiconducting materials are discussed. In this review the most attention is focused on the development and application of molecularly imprinted polymer-based structures, which can replace antibodies, receptors, and many others expensive affinity reagents. The applicability of electrochromic polymers in affinity sensor design is envisaged. Sufficient biocompatibility of some conducting polymers enables to apply them as "stealth coatings" in the future implantable affinity-sensors. Some new perspectives and trends in analytical application of polymer-based semiconducting materials are highlighted.

An electrochemical sensor for high sensitive determination of lysozyme based on the aptamer competition approach

Protein is a kind of basic substance that constitutes a life body. The determination of protein is very important for the research of biology, medicine, and other fields. Lysozyme is relatively small and simple in structure among all kinds of proteins, so it is often used as a standard target detector in the study of aptamer sensor for protein detection. In this paper, a lysozyme electrochemical sensor based on aptamer competition mechanism is proposed. We have successfully prepared a signal weakening electrochemical sensor based on the lysozyme aptamer competition mechanism. The carboxylated multi-walled carbon nanotubes (MWCNTs) were modified on the glassy carbon electrode, and the complementary aptamer DNA with amino group was connected to MWCNTs. Because of the complementary DNA of daunomycin into the electrode, the electrochemical signal is generated. When there is a target, the aptamer binds to lysozyme with higher binding power, and the original complementary chain breaks down, resulting in the loss of daunomycin inserted into the double chain and the weakening of electrochemical signal. Differential pulse voltammetry was used to determine lysozyme, the response range was 1–500 nM, the correlation coefficient was 0.9995, and the detection limit was 0.5 nM. In addition, the proposed sensor has good selectivity and anti-interference.

Electrochemical Sensors Based on Conducting Polymers for the Aqueous Detection of Biologically Relevant Molecules

Electrochemical sensors appear as low-cost, rapid, easy to use, and in situ devices for determination of diverse analytes in a liquid solution. In that context, conducting polymers are much-explored sensor building materials because of their semiconductivity, structural versatility, multiple synthetic pathways, and stability in environmental conditions. In this state-of-the-art review, synthetic processes, morphological characterization, and nanostructure formation are analyzed for relevant literature about electrochemical sensors based on conducting polymers for the determination of molecules that (i) have a fundamental role in the human body function regulation, and (ii) are considered as water emergent pollutants. Special focus is put on the different types of micro- and nanostructures generated for the polymer itself or the combination with different materials in a composite, and how the rough morphology of the conducting polymers based electrochemical sensors affect their limit of detection. Polypyrroles, polyanilines, and polythiophenes appear as the most recurrent conducting polymers for the construction of electrochemical sensors. These conducting polymers are usually built starting from bifunctional precursor monomers resulting in linear and branched polymer structures; however, opportunities for sensitivity enhancement in electrochemical sensors have been recently reported by using conjugated microporous polymers synthesized from multifunctional monomers.

Selective determination of non-organophosphorus insecticide using DNA aptamer-based single-use biosensors

In the present study, we developed a disposable aptamer-based biosensor for rapid, sensitive, and reliable detection of acetamiprid (ACE). To improve the sensitivity of the aptasensor, poly-5-amino-2-mercapto-1,3,4-thiadiazole [P(AMT)] and gold nanoparticles (AuNPs) were progressively electrodeposited on the screen-printed electrode (SPE) surface by using cyclic voltammetry (CV) technique. For the determination of ACE, thiol-modified primary aptamer (Apt1) was selected by using the SELEX method and immobilized on the surface of the P(AMT) and AuNPs-modified SPE (SPE/P(AMT)/AuNPs) via AuS bonding. Then, the surface-bound aptamer was incubated with ACE for 45 Min. After that, the biotin-labeled aptamer 2 (Apt2) was interacted with the ACE, then the enzyme-labeled step was performed. In this step, alkaline phosphatase (ALP) was bound to the surface through the interaction between Apt2 labeled with biotin and streptavidin (strep)-ALP conjugate. The determination of ACE was achieved by measuring the oxidation signal of α-naphthol, which is formed on the electrode surface through the interaction of ALP with α-naphthyl phosphate. The working range of the developed aptasensor was determined as 5 × 10^-12 -5 × 10^-10  mol L^-1 with a low limit of detection (1.5 pmol L^-1 ). It was also found that the proposed aptasensor possessed great advantages such as low cost, good selectivity, and good reproducibility.

Dispersible Conjugated Polymer Nanoparticles as Biointerface Materials for Label-Free Bacteria Detection

Fast and efficient identification of bacterial pathogens in water and biological fluids is an important issue in medical, food safety, and public health concerns that requires low-cost and efficient sensing strategies. Impedimetric sensors are promising tools for monitoring bacteria detection because of their reliability and ease-of-use. We herein report a study on new biointerface-based amphiphilic poly(3-hexylthiophene)-b-poly(3-triethylene-glycol-thiophene), P3HT-b-P3TEGT, for label-free impedimetric detection of Escherichia coli (E. coli). This biointerface is fabricated by the self-assembly of P3HT-b-P3TEGT into core-shell nanoparticles, which was further decorated with mannose, leading to an easy-to-use solution-processable nanoparticle material for biosensing. The hydrophilic block P3TEGT promotes antifouling and prevents nonspecific interactions, while improving the ionic and electronic transport properties, thus enhancing the electrochemical-sensing capability in aqueous solution. Self-assembly and micelle formation of P3HT-b-P3TEGT were analyzed by 2D-NMR, Fourier transform infrared, dynamic light scattering, contact angle, and microscopy characterizations. Detection of E. coli was characterized and evaluated using electrochemical impedance spectroscopy and optical and scanning electron microscopy techniques. The sensing layer based on the mannose-functionalized P3HT-b-P3TEGT nanoparticles demonstrates targeting ability toward E. coli pili protein with a detection range from 10³ to 10⁷ cfu/mL, and its selectivity was studied with Gram(+) bacteria. Application to real samples was performed by detection of bacteria in tap and the Nile water. The approach developed here shows that water/alcohol-processable-functionalized conjugated polymer nanoparticles are suitable for use as electrode materials, which have potential application in fabrication of a low-cost, label-free impedimetric biosensor for the detection of bacteria in water.

A novel lactose biosensor based on electrochemically synthesized 3,4-ethylenedioxythiophene/thiophene (EDOT/Th) copolymer

In this study, a new lactose biosensor has been developed in which the 3,4-ethylenedioxythiophene/thiophene (EDOT/Th) copolymer is used as a transducer. The EDOT/Th copolymer was deposited on the glassy carbon electrode to be used as the working electrode. In addition to the working electrode, the three-electrode system was used in both the electrochemical synthesis and in the biosensor measurements. Lactase (β-galactosidase) that catalyzes the breakdown of lactose into monosaccharides (glucose and galactose) and galactose oxidase that catalyzes the oxidation of the resulting galactose were attached to the copolymer by a cross-linker on the modified working electrode. The response of the enzyme electrode to lactose was determined by cyclic voltammetry (CV) at +0.12 V. Enzyme electrode optimization parameters (pH, temperature, enzyme concentration, etc.) were performed. Fourier transform infrared spectroscopy, scanning electron microscopy and CV methods were used to support copolymer formation. In addition, the characteristics of the enzyme electrode prepared in this study (Km, 0.02 mM; activation energy Ea, 38 kJ/mol; linear working range, up to 1.72 mM; limit of detection, 1.9 × 10−5 M and effects of interferents [uric acid and ascorbic acid]) were determined.

Combining Electrospinning and Vapor-Phase Polymerization for the Production of Polyacrylonitrile/ Polypyrrole Core-Shell Nanofibers and Glucose Biosensor Application

In this work, polyacrylonitrile (PAN) nanofiber mats coated with conductive polypyrrole layers were produced at the surface of gold electrodes by a two-step approach combining electrospinning and vapor phase polymerization. In the first step, smooth and uniform PAN fibers exhibiting an average diameter of 650 ± 10 nm were generated through electrospinning of 12 wt% PAN solutions. The electrospun PAN fibers were impregnated with iron(III)tosylate (FeTos), annealed at 70°C and used as a robust and stable template for the growth of a thin layer of conductive polymer by co-polymerizing pyrrole (Py) and pyrrole-3-carboyxylic acid (Py3COOH) vapors under nitrogen atmosphere. The carboxyl groups introduced in polypyrrole coatings enabled further covalent binding of a model enzyme, glucose oxidase. The effect of different parameters (concentration of FeTos into the immersion solution, time of polymerization, Py/Py3COOH molar ratio) on the PAN/PPy/PPy3COOH/GOx impedimetric biosensor response was investigated. In the best conditions tested (immersion of the PAN fibers into 20 wt% FeTos solution, polymerization time: 30 min, 1:2 Py/Py3COOH ratio), the biosensor response was linear in a wide range of glucose concentration (20 nM−2μM) and selective toward ascorbic and uric acids. A very low limit of detection (2 nM) compared to those already reported in the literature was achieved. This value enables the determination of glucose in human serum after a large dilution of the sample (normal concentrations: 3.6 mM−6.1 mM range).