Molecularly imprinted polymer-based bioelectrical interfaces with intrinsic molecular charges

The Versatility of Biological Field-Effect Transistor-Based Biosensors (BioFETs) in Point-of-Care Diagnostics: Applications and Future Directions for Peritoneal Dialysis Monitoring

Peritoneal dialysis (PD) is a vital treatment for end-stage renal disease patients, but its efficacy is often compromised by complications such as infections and peritoneal fibrosis. Biological field-effect transistors (BioFETs) present a promising solution for rapid, sensitive, and non-invasive detection of indicators and biomarkers associated with these complications, potentially enabling early intervention. However, BioFETs are yet to be adopted for PD monitoring. This review presents a forward-looking analysis of the capacity and potential integration of BioFETs into PD management systems, highlighting their capacity to monitor both routine indicators of dialysis efficiency and metabolic status, as well as specific biomarkers for complications such as inflammation and fibrosis. We examine the challenges in adapting BioFETs for PD applications, focusing on key areas for improvement, including sensitivity, specificity, stability, reusability, and clinical integration. Furthermore, we discuss various approaches to address these challenges, which are crucial for developing point-of-care (PoC) and multiplexed wearable devices. These advancements could facilitate continuous, precise, and user-friendly monitoring, potentially revolutionizing PD complication management and enhancing patient care.

Low-cost graphite and double-gate FET-based label-free biosensor for dopamine sensing to detect neural diseases

The manuscript proposes biosensors for detecting different concentrations of neurotransmitters named dopamine, which have a critical role in the human body's neurological, hormonal, and renal systems. In this work, the primary focus is to detect dopamine, whose disorder levels cause many neurological disabilities such as Alzheimer's and Parkinson's disease. In the present work, the simulation of two different structures has been studies: a) a graphite-based structure and b) a double gate TFET structure for detecting dopamine using TCAD Silvaco software. The proposed device utilizes a graphite-based structure with respective work functions of the used materials and studies the change in ON current (ION sensing factor is calculated for simulation study for VGS = 0.8 V). The cavity is increased to 800 µm for graphite-based biosensors for improved sensitivity. The graphite-based biosensors can detect up to 13.3 nM concentration of dopamine. Experimental electrochemical analysis results verify the proposed graphite-based biosensors' sensitivity for different dopamine concentrations. Another double gate field effect transistor (FET) biosensor has also been investigated for the detection of dopamine. The effective dielectric constant has been calculated using Bruggeman's model to check the sensitivity of double gate FET-based sensors for varying dopamine and uric acid concentrations. The sensitivity is increased with the increase of dopamine concentration percentage.

Electrical monitoring of human-serum-albumin-templated molecularly imprinted polymer nanoparticles with high affinity based on molecular charges and their visualization

Human-serum-albumin (HSA)-templated molecularly imprinted polymer nanoparticles (nano-MIPs) were integrated with a solution-gated field-effect transistor-based biosensor. The real-time electrical analysis of nano-MIP-HSA binding showed a high affinity and specificity of nano-MIPs for HSA. Moreover, the binding behaviour was continuously visualised using a solution-gated complementary metal-oxide semiconductor array image biosensor.

Molecular imprinting technology for biomedical applications

Molecularly imprinted polymers (MIPs), a type of biomimetic material, have attracted considerable interest owing to their cost-effectiveness, good physiochemical stability, favourable specificity and selectivity for target analytes, and widely used for various biological applications. It was demonstrated that MIPs with significant selectivity towards protein-based targets could be applied in medicine, diagnostics, proteomics, environmental analysis, sensors, various in vivo and/or in vitro applications, drug delivery systems, etc. This review provides an overview of MIPs dedicated to biomedical applications and insights into perspectives on the application of MIPs in newly emerging areas of biotechnology. Many different protocols applied for the synthesis of MIPs are overviewed in this review. The templates used for molecular imprinting vary from the minor glycosylated glycan-based structures, amino acids, and proteins to whole bacteria, which are also overviewed in this review. Economic, environmental, rapid preparation, stability, and reproducibility have been highlighted as significant advantages of MIPs. Particularly, some specialized MIPs, in addition to molecular recognition properties, can have high catalytic activity, which in some cases could be compared with other bio-catalytic systems. Therefore, such MIPs belong to the class of so-called 'artificial enzymes'. The discussion provided in this manuscript furnishes a comparative analysis of different approaches developed, underlining their relative advantages and disadvantages highlighting trends and possible future directions of MIP technology.

Signal transduction interfaces for field-effect transistor-based biosensors

Biosensors based on field-effect transistors (FETs) are suitable for use in miniaturized and cost-effective healthcare devices. Various semiconductive materials can be applied as FET channels for biosensing, including one- and two-dimensional materials. The signal transduction interface between the biosample and the channel of FETs plays a key role in translating electrochemical reactions into output signals, thereby capturing target ions or biomolecules. In this Review, distinctive signal transduction interfaces for FET biosensors are introduced, categorized as chemically synthesized, physically structured, and biologically induced interfaces. The Review highlights that these signal transduction interfaces are key in controlling biosensing parameters, such as specificity, selectivity, binding constant, limit of detection, signal-to-noise ratio, and biocompatibility.

Terminally Phosphorylated Triblock Polyethers Acting Both as Templates and Pore-Forming Agents for Surface Molecular Imprinting of Monoliths Targeting Phosphopeptides

The novel process reported here described the manufacture of monolithic molecularly imprinted polymers (MIPs) using a terminally functionalized block copolymer as the imprinting template and pore-forming agent. The MIPs were prepared through a step-growth polymerization process using a melamine-formaldehyde precondensate in a biphasic solvent system. Despite having a relatively low imprinting factor, the use of MIP monolith in liquid chromatography demonstrated the ability to selectively target desired analytes. An MIP capillary column was able to separate monophosphorylated peptides from a tryptic digest of bovine serum albumin. Multivariate data analysis and modeling of the phosphorylated and nonphosphorylated peptide retention times revealed that the number of phosphorylations was the strongest retention contributor for peptide retention on the monolithic MIP capillary column.

Molecular Level Sucrose Quantification: A Critical Review

Sucrose is a primary metabolite in plants, a source of energy, a source of carbon atoms for growth and development, and a regulator of biochemical processes. Most of the traditional analytical chemistry methods for sucrose quantification in plants require sample treatment (with consequent tissue destruction) and complex facilities, that do not allow real-time sucrose quantification at ultra-low concentrations (nM to pM range) under in vivo conditions, limiting our understanding of sucrose roles in plant physiology across different plant tissues and cellular compartments. Some of the above-mentioned problems may be circumvented with the use of bio-compatible ligands for molecular recognition of sucrose. Nevertheless, problems such as the signal-noise ratio, stability, and selectivity are some of the main challenges limiting the use of molecular recognition methods for the in vivo quantification of sucrose. In this review, we provide a critical analysis of the existing analytical chemistry tools, biosensors, and synthetic ligands, for sucrose quantification and discuss the most promising paths to improve upon its limits of detection. Our goal is to highlight the criteria design need for real-time, in vivo, highly sensitive and selective sucrose sensing capabilities to enable further our understanding of living organisms, the development of new plant breeding strategies for increased crop productivity and sustainability, and ultimately to contribute to the overarching need for food security.

Development of a Redox-Label-Doped Molecularly Imprinted Polymer on β-Cyclodextrin/Reduced Graphene Oxide for Electrochemical Detection of a Stress Biomarker

Cortisol is a major stress biomarker involved in the regulation of metabolic and immune responses. Readily accessible assays with sufficient quantitative and temporal resolution can assist in prevention, early diagnosis, and management of chronic diseases. Whereas conventional assays are costly in terms of time, labor, and capital, an electrochemical approach offers the possibility of miniaturization and detection at the point-of-care. Here, we investigate the biosensor application of molecularly imprinted polypyrrole (PPy) doped with hexacyanoferrate (HCF) and coupled to reduced graphene oxide functionalized with β-cyclodextrin (β-CD). β-CD provides an inclusion site for lipophilic cortisol and was electrochemically grafted simultaneous with reduction of GO. Next, PPy was electrochemically deposited in presence of cortisol template with HCF dopant ions serving as intrinsic redox probe. Thus, the sensor response was evaluated via changes of redox peak current in cyclic voltammetry and demonstrated a broad logarithmic detection range (5 pg/mL to 5000 ng/mL, R ² = 0.995), with a sensitivity of 8.809 μA log^-1 (ng/mL) cm^-2 and LOD of 19.3 pM. The sensor was shown to be specific toward cortisol in reference to salivary cortisol concentration in saliva over structural analogues. The sensor was exhibited to determine cortisol in artificial saliva at normal and elevated levels. The good performance and facile electrochemical fabrication of this antibody- and external label-free interface are promising for the development of affordable point-of-care biosensors.

Surface Characteristics and Formation of Polyserotonin Thin Films for Bioelectrical and Biocompatible Interfaces

In this study, we examined the fundamental surface characteristics of a polyserotonin (pST) film, which is attractive as a bioelectrical and biocompatible interface of biosensors. The pST film can easily be modified on electrode materials such as Au by self-polymerization and electropolymerization. By a simple cytotoxicity test using nonadhesive living cells, we found that the pST film is biocompatible for culturing cells on it. This finding is also supported by the fact that the surface tension of the pST film is moderate for protein adsorptions. The pST film is thinner and smoother than a poly-dopamine film, the chemical structure of which is similar to that of the pST film, depending on the polymerization time, cycle, and temperature; thus, ST as the main monomer can facilitate the precise control of the thickness and roughness of functional polymer membranes on the nanometer order. In addition, the pST film is useful as a relatively insulative interface for preventing interfering species from approaching electrode surfaces without their nonspecific adsorption, depending on the surface charges of the pST film in solutions of different pHs. The formation of the pST film self-polymerized on electrode materials is derived from the adsorption of pST nanoparticles formed by oxidative polymerization under basic conditions; therefore, the process of pST film formation should be considered in the functionalization of the pST film as a bioelectrical interface that allows biomolecular recognition (e.g., molecularly imprinted polymer membrane) for its application to wearable and biocompatible biosensors.

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.

Technical Perspectives on Applications of Biologically Coupled Gate Field-Effect Transistors

Biosensing technologies are required for point-of-care testing (POCT). We determine some physical parameters such as molecular charge and mass, redox potential, and reflective index for measuring biological phenomena. Among such technologies, biologically coupled gate field-effect transistor (Bio-FET) sensors are a promising candidate as a type of potentiometric biosensor for the POCT because they enable the direct detection of ionic and biomolecular charges in a miniaturized device. However, we need to reconsider some technical issues of Bio-FET sensors to expand their possible use for biosensing in the future. In this perspective, the technical issues of Bio-FET sensors are pointed out, focusing on the shielding effect, pH signals, and unique parameters of FETs for biosensing. Moreover, other attractive features of Bio-FET sensors are described in this perspective, such as the integration and the semiconductive materials used for the Bio-FET sensors.

Self-oscillating chemoelectrical interface of solution-gated ion-sensitive field-effect transistor based on Belousov-Zhabotinsky reaction

The Belousov-Zhabotinsky (BZ) self-oscillation reaction is an important chemical model to elucidate nonequilibrium chemistry in an open system. However, there are only a few studies on the electrical behavior of pH oscillation induced by the BZ reaction, although numerous studies have been carried out to investigate the mechanisms by which the BZ reaction interacts with redox reactions, which results in potential changes. Needless to say, the electrical characteristic of a self-oscillating polymer gel driven by the BZ reaction has not been clarified. On the other hand, a solution-gated ion-sensitive field-effect transistor (ISFET) has a superior ability to detect ionic charges and includes capacitive membranes on the gate electrode. In this study, we carried out the electrical monitoring of self-oscillation behaviors at the chemoelectrical interface based on the BZ reaction using ISFET sensors, focusing on the pH oscillation and the electrical dynamics of the self-oscillating polymer brush. The pH oscillation induced by the BZ reaction is not only electrically observed using the ISFET sensor, the electrical signals of which results from the interfacial potential between the solution and the gate insulator, but also visualized using a large-scale and high-density ISFET sensor. Moreover, the N-isopropylacrylamide (NIPAAm)-based self-oscillating polymer brush with Ru(bpy)3 as a catalyst clearly shows a periodic electrical response based on the swelling-deswelling behavior caused by the BZ reaction on the gate insulator of the ISFET sensor. Thus, the elucidation of the electrical self-oscillation behaviors induced by the BZ reaction using the ISFET sensor provides a solution to the problems of nonequilibrium chemistry.

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.

Hydrogel-Coated Gate Field-Effect Transistor for Real-Time and Label-Free Monitoring of β-Amyloid Aggregation and Its Inhibition

In this paper, we propose a hydrogel-coated gate field-effect transistor (FET) for the real-time and label-free monitoring of β-amyloid (Aβ) aggregation and its inhibition. The hydrogel used in this study is composed of poly tetramethoxysilane (TMOS), in which Aβ monomers are entrapped and then aggregate, and coated on the gate insulator; that is, Aβ aggregation is induced in the vicinity of the sensing surface. With the Aβ hydrogel-coated gate FET, the steplike decrease in the surface potential of the Aβ hydrogel-coated gate electrode is electrically monitored in real time, according to the stepwise aggregation of Aβ monomers to form into fibrils through oligomers and so forth in stages. This is because the capacitance of the Aβ-hydrogel membrane decreases depending on the stage of aggregation; that is, the hydrophobicity of the Aβ-hydrogel membrane increases stepwise depending on the amount of Aβ aggregates. The formation of Aβ fibrils is also confirmed in the measurement solution using a fluorescent dye, thioflavin T, which selectively binds to the Aβ fibrils. Moreover, the addition of daunomycin, an inhibitor of Aβ aggregation, to the measurement solution suppresses the stepwise electrical response of the Aβ hydrogel-coated gate FET. Thus, a platform based on the Aβ hydrogel-coated gate FET is suitable for a simple screening system for inhibitors of Aβ aggregation, which may lead the identification of potential therapeutic agents for Alzheimer's disease.

Electrochemical Cleavage of the Carbon-Boron Bond in p-Acetamidophenylboronic Acid at Neutral pH Conditions

Herein, it is reported that p-acetamidophenylboronic acid can be electrolytic cleavage of the carbon-boron bond to p-acetamidophenol at an electric potential of 1.2 V vs. Ag/AgCl in 100 mM phosphate buffer of pH 7.4 (containing 10% acetonirile). The electrochemical reaction was investigated by HPLC, LC with tandem mass spectrometry, and cyclic voltammetry. This electrochemical reaction could be useful in the development of electrical controlled drug delivery systems under neutral pH conditions.

Potential Use of Papaya Waste as a Fuel for Bioelectricity Generation

Papaya (Carica papaya) waste cause significant commercial and environmental damage, mainly due to the economic losses and foul odours they emit when decomposing. Therefore, this work provides an innovative way to generate electricity for the benefit of society and companies dedicated to the import and export of this fruit. Microbial fuel cells are a technology that allows electricity generation. These cells were produced with low-cost materials using zinc and copper electrodes; while a 150 mL polymethylmethacrylate tube was used as a substrate collection chamber (papaya waste). Maximum values of 0.736 ± 0.204 V and 5.57 ± 0.45 mA were generated, while pH values increased from 3.848 to 8.227 ± 0.35 and Brix decreased slowly from the first day. The maximum power density value was 878.38 mW/cm2 at a current density of 7.245 A/cm2 at a maximum voltage of 1072.77 mV. The bacteria were identified with an identity percentage of 99.32% for Achromobacter xylosoxidans species, 99.93% for Acinetobacter bereziniae, and 100.00% for Stenotrophomonas maltophilia. This research gives a new way for the use of papaya waste for bioelectricity generation.

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.