Electrochemical sensing of macromolecules based on molecularly imprinted polymers: challenges, successful strategies, and opportunities

Non-enzymatic electrochemical sensors for point-of-care testing: Current status, challenges, and future prospects

Current electrochemical sensors in point-of-care (POC) testing devices rely mainly on enzyme-based sensors owing to superior sensitivity and selectivity. Nevertheless, the poor stability, high reagent cost, complex fabrication methods and requirement of specific operational conditions make their adaptability in real-world applications unfavorable. Non-enzymatic electrochemical sensors are thus developed as they are more robust and cost-effective strategies. The advancement in material science and nanotechnology enables the development of novel non-enzymatic electrodes with favorable analytical performance. However, the developments are yet far from being adopted as viable products. This review therefore aims to gain insight into the field and evaluate the current progress and challenges to eventually propose future research directions. Here, fabrication strategies based on traditional and emerging technology are discussed in the light of analytical performance and cost-effectiveness. Moreover, the discussion is given on the pros and cons of non-enzymatic sensors when they are employed with various kinds of sample matrices, i.e., clinical and non-clinical samples, which must be taken into consideration for sensor development. Furthermore, molecular imprinting technology in tackling the selectivity issue is introduced and current progress is provided. Finally, the promising strategies from literature for solving the remaining challenges are included which could facilitate further development of robust POC testing devices based non-enzymatic sensors. We believe that once researchers and technology developers have reached the point where most problems are solved, the non-enzymatic sensors are going to be the robust choice for POC testing in clinical diagnostic, ensuring food safety, monitoring contaminants in environment, and bioprocess control.

Visible-Light Photo-Iniferter Polymerization of Molecularly Imprinted Polymers for Direct Integration with Nanotransducers

Molecularly Imprinted Polymers (MIPs) have gained prominence as synthetic receptors, combining simplicity of synthesis with robust molecular recognition akin to antibodies and enzymes. One of their main application areas is chemical sensing. However, direct integration of MIPs with nanostructured transducers, crucial for enhancing sensing capabilities and broadening MIPs sensing applications, remains limited. This limitation mainly arises from the need for precise control over the MIP features (such as thickness) during deposition on nanostructured transducers. This work explores the potential of depositing MIPs directly onto nanostructured transducers via controlled radical photopolymerization, focusing on nanoporous silica (PSiO2) with pore sizes of 40 nm and aspect ratio exceeding 100 as an interferometric optical nanotransducer. Leveraging the covalent attachment of a photo-iniferter agent onto the PSiO2 surface, we achieved effective control over the polymerization process, resulting in the deposition of thin and uniform MIP layers on PSiO2. As a case study, we developed an MIP-based PSiO2 optical sensor for propranolol, used as the template molecule, showcasing excellent linearity, a low detection limit, and efficacy in real matrices such as tap water. The results further demonstrate the sensor selectivity for the target molecule, along with its reusability and stability for at least 60 days.

A Molecularly Imprinted Polymer-Based Porous Silicon Optical Sensor for Quercetin Detection in Wines

Quercetin (QU), a bioactive flavonoid with significant nutritional and antioxidant properties, plays a vital role in the quality and stability of wine. This study presents the development of a molecularly imprinted polymer (MIP)-based optical sensor for the selective and sensitive detection of quercetin in red and white wines. The sensor combines the selective molecular recognition capabilities of MIPs with the optical properties of nanostructured porous silica (PSiO2) scaffolds, which serve as the transducer. MIP synthesis was achieved through a novel room-temperature vapor-phase polymerization method using pyrrole as the functional monomer. Computational simulations were used to optimize pyrrole interactions with QU and at the polymer level, to explore the binding interactions of QU with the resulting polypyrrole (PPy) matrix. Comprehensive characterization including UV-vis reflectance spectroscopy and advanced surface analyses confirmed successful MIP formation. The sensor exhibited high sensitivity in a dual linear response range (2.5-80 μM and 80-200 μM), with a detection limit of 0.7 μM. Selectivity tests against structurally similar flavonoids and antioxidants demonstrated a significantly higher response to quercetin, with an imprinting factor of 3.6. The sensor was validated using real wine samples, demonstrating the ability to detect quercetin without prior sample preparation. Results showed strong agreement with high-performance liquid chromatography (HPLC), confirming the sensor reliability. Additionally, the sensor exhibited excellent reusability with minimal signal variation (RSD = 2.6%) and good stability over 60 days (RSD = 3%). This work highlights the potential of MIP-based optical sensors for the real-time monitoring of bioactive compounds in complex food matrices, such as wine, offering a robust and cost-effective alternative for quality control applications.

Silica Nanoparticles Tailored with a Molecularly Imprinted Copolymer Layer as a Highly Selective Biorecognition Element

Molecularly imprinted silica nanoparticles (SP-MIP) are synthesized for the real-time optical detection of low-molecular-weight compounds. Azo-initiator-modified silica beads are functionalized through reversible addition-fragmentation chain transfer (RAFT) polymerization, which leads to efficient control of the grafted layer. The copolymerization of methacrylic acid (MAA) and ethylene glycol dimethacrylate (EDMA) on azo initiator-coated silica particles (≈100 nm) using chain transfer agent (2-phenylprop-2-yl-dithiobenzoate) is carried out in the presence of a target analyte molecule (l-Boc-phenylalanine anilide, l-BFA). The chemical and morphological properties of SP-MIP are characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller surface analysis, and thermogravimetric analysis. Finally, SP-MIP is located on the gold surface to be used as a biorecognition layer on the surface plasmon resonance spectrometer (SPR). The sensitivity, response time, and selectivity of SP-MIP are investigated by three similar analogous molecules (l-Boc-Tryptophan, l-Boc-Tyrosine, and l-Boc-Phenylalanine) and the imprinted particle surface showed excellent relative selectivity toward l-Boc-Phenylalanine (l-BFA) (k = 61), while the sensitivity is recorded as limit of detection = 1.72 × 10-4 m.

Polyaniline-based bovine serum albumin imprinted electrochemical sensor for ultra-trace-level detection in clinical and food safety applications

Monitoring bovine serum albumin (BSA) at ultra-low levels is crucial for clinical and food safety applications, as it plays a significant role in identifying various health conditions and potential risks, necessitating fast, trace-level detection of BSA. This study proposes an approach to address these challenges by employing molecularly imprinted polymer (MIP) to develop an ultra-trace-level and cost-effective BSA sensing platform. The MIP electrochemical sensor was developed using polyaniline (PANI) combined with the protein crosslinker glutaraldehyde (GA) to optimize BSA surface imprinting in the MIP. As a result, the sensor achieves a sensitivity of 1.24 μA/log(pg/mL), with a picomolar detectable limit of 2.3 pg/mL (0.035 pM) and a wide detection range from 20 pg/mL to 200,000 pg/mL (0.303 pM to 3030 pM), making it suitable for clinical and food safety applications. Additionally, the study explores the interaction between an acidic surfactant protein eluent (acetic acid with sodium dodecyl sulfate, AcOH-SDS) and BSA vacant sites, enhancing recognition and re-binding. The PANI-based MIP sensor demonstrates initial feasibility and practicality in commercial milk and real human serum, opening avenues for early disease detection and ensuring food safety in BSA-related immune responses.

Enhancing the substrate selectivity of enzyme mimetics in biosensing and bioassay: Novel approaches

A substantial development in nanoscale materials possessing catalytic activities comparable with natural enzymes has been accomplished. Their advantages were owing to the excellent sturdiness in an extreme environment, possibilities of their large-scale production resulting in higher profitability, and easy manipulation for modification. Despite these advantages, the main challenge for artificial enzyme mimetics is the lack of substrate selectivity where natural enzymes flourish. This review addresses this vital problem by introducing substrate selectivity strategies to three classes of artificial enzymes: molecularly imprinted polymers, nanozymes (NZs), and DNAzymes. These rationally designed strategies enhance the substrate selectivity and are discussed and exemplified throughout the review. Various functional mechanisms associated with applying enzyme mimetics in biosensing and bioassays are also given. Eventually, future directives toward enhancing the substrate selectivity of biomimetics and related challenges are discussed and evaluated based on their efficiency and convenience in biosensing and bioassays.

Molecularly imprinted polymer composite membranes: From synthesis to diverse applications

This review underscores the fundamentals of MIP-CMs and systematically summarizes their synthetic strategies and applications, and potential developments. MIP-CMs are widely acclaimed for their versatility, finding applications in separation, filtration, detection, and trace analysis, as well as serving as scaffolds in a range of analytical, biomedical and industrial contexts. Also characterized by extraordinary selectivity, remarkable sensitivity, and outstanding capability to bind molecules, those membranes are also cost-effective, highly stable, and configurable in terms of recognition and, therefore, inalienable in various application fields. Issues relating to the potential future for the paper are discussed in the last section with the focus on the improvement of resource practical application across different areas. Hence, this review can be seen as a kind of cookbook for the design and fabrication of MIP-CMs with an intention to expand the scope of their application.

Molecular Imprinting Technology for Advanced Delivery of Essential Oils

Essential oils (EOs) hold therapeutic potential, but their conventional delivery systems have some limitations. This review focuses on the critical review and discussion of research related to EO delivery systems. The review also explores how molecular imprinting technologies (MIT) can advance EO delivery. MIT offer several techniques, namely covalent, non-covalent, and semi-covalent imprinting, creating targeted cavities that selectively bind and release EOs. These approaches promise significant advantages including increased selectivity, controlled release, and protection from environmental degradation. However, some challenges related to the stability and biocompatibility of MIPs remain unsolved. Integrating nanotechnology through methods like nanoparticle imprinting and some lithographic techniques seems promising to overcome these limitations. Some recently established models and systems used for EO-related research are paving the way for a more efficient and targeted EO delivery approach to harnessing the therapeutic power of EOs. Therefore, some recent and future research seems promising, and eventually it will increase the effectiveness of MIP-based EO delivery systems.

Boosting Electrochemical Sensing Performances Using Molecularly Imprinted Nanoparticles

Nanoparticles of molecularly imprinted polymers (nanoMIPs) combine the excellent recognition ability of imprinted polymers with specific properties related to the nanosize, such as a high surface-to-volume ratio, resulting in highly performing recognition elements with surface-exposed binding sites that promote the interaction with the target and, in turn, binding kinetics. Different synthetic strategies are currently available to produce nanoMIPs, with the possibility to select specific conditions in relation to the nature of monomers/templates and, importantly, to tune the nanoparticle size. The excellent sensing properties, combined with the size, tunability, and flexibility of synthetic protocols applicable to different targets, have enabled the widespread use of nanoMIPs in several applications, including sensors, imaging, and drug delivery. The present review summarizes nanoMIPs applications in sensors, specifically focusing on electrochemical detection, for which nanoMIPs have been mostly applied. After a general survey of the most widely adopted nanoMIP synthetic approaches, the integration of imprinted nanoparticles with electrochemical transducers will be discussed, representing a key step for enabling a reliable and stable sensor response. The mechanisms for electrochemical signal generation will also be compared, followed by an illustration of nanoMIP-based electrochemical sensor employment in several application fields. The high potentialities of nanoMIP-based electrochemical sensors are presented, and possible reasons that still limit their commercialization and issues to be resolved for coupling electrochemical sensing and nanoMIPs in an increasingly widespread daily-use technology are discussed.

Effect of Various Carbon Electrodes on MIP-Based Sensing Proteins Using Poly(Scopoletin): A Case Study of Ferritin

Sensitivity in the sub-nanomolar concentration region is required to determine important protein biomarkers, e.g., ferritin. As a prerequisite for high sensitivity, in this paper, the affinity of the functional monomer to the macromolecular target ferritin in solution was compared with the value for the respective molecularly imprinted polymer (MIP)-based electrodes, and the influence of various surface modifications of the electrode was investigated. The analytical performance of ferritin sensing was investigated using three different carbon electrodes (screen-printed carbon electrodes, single-walled-carbon-nanotube-modified screen-printed carbon electrodes, and glassy carbon electrodes) covered with a scopoletin-based MIP layer. Regardless of the electrode type, the template molecule ferritin was mixed with the functional monomer scopoletin, and electropolymerization was conducted using multistep amperometry. All stages of MIP preparation were followed by evaluating the diffusional permeability of the redox marker ferricyanide/ferrocyanide through the polymer layer by differential pulse voltammetry. The best results were obtained with glassy carbon electrodes. The MIP sensor responded up to 0.5 µM linearly with a Kd of 0.30 µM. Similar results were also obtained in solution upon the interaction of scopoletin and ferritin using fluorescence spectroscopy, resulting in the quenching of the scopoletin signal, with a calculated Kd of 0.81 µM. Moreover, the binding of 1 µM ferritin led to 49.6% suppression, whereas human serum albumin caused 8.6% suppression.

The Neuromuscular Disorder Mediated by Extracellular Vesicles in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) represents a neurodegenerative disorder characterized by the progressive loss of both upper and lower motor neurons, resulting in muscular atrophy and eventual paralysis. While much research has concentrated on investigating the impact of major mutations associated with ALS on motor neurons and central nervous system (CNS) cells, recent studies have unveiled that ALS pathogenesis extends beyond CNS imbalances, encompassing dysregulation in other tissues such as skeletal muscle. Evidence from animal models and patients supports this broader perspective. Skeletal muscle, once considered solely as an effector organ, is now recognized as possessing significant secretory activity capable of influencing motor neuron survival. However, the precise cellular and molecular mechanisms underlying the detrimental effects observed in muscle and its associated structures in ALS remain poorly understood. Additionally, emerging data suggest that extracellular vesicles (EVs) may play a role in the establishment and function of the neuromuscular junction (NMJ) under both physiological and pathological conditions and in wasting and regeneration of skeletal muscles, particularly in neurodegenerative diseases like ALS. This review aims to explore the key findings about skeletal muscle involvement in ALS, shedding light on the potential underlying mechanisms and contributions of EVs and their possible application for the design of biosensors.

Electrochemical protein biosensors for disease marker detection: progress and opportunities

The development of artificial intelligence-enabled medical health care has created both opportunities and challenges for next-generation biosensor technology. Proteins are extensively used as biological macromolecular markers in disease diagnosis and the analysis of therapeutic effects. Electrochemical protein biosensors have achieved desirable specificity by using the specific antibody-antigen binding principle in immunology. However, the active centers of protein biomarkers are surrounded by a peptide matrix, which hinders charge transfer and results in insufficient sensor sensitivity. Therefore, electrode-modified materials and transducer devices have been designed to increase the sensitivity and improve the practical application prospects of electrochemical protein sensors. In this review, we summarize recent reports of electrochemical biosensors for protein biomarker detection. We highlight the latest research on electrochemical protein biosensors for the detection of cancer, viral infectious diseases, inflammation, and other diseases. The corresponding sensitive materials, transducer structures, and detection principles associated with such biosensors are also addressed generally. Finally, we present an outlook on the use of electrochemical protein biosensors for disease marker detection for the next few years.

Green Synthesis of a Molecularly Imprinted Polymer Based on a Novel Thiophene-Derivative for Electrochemical Sensing

An environmentally friendly and sustainable approach was adopted to produce a molecularly imprinted polymer (MIP) via electropolymerization, with remarkable electrochemical sensing properties, tested in tyrosine (tyr) detection. The 2,2'-bis(2,2'-bithiophene-5-yl)-3,3'-bithianaphtene (BT2-T4) was chosen as functional monomer and MIP electrosynthesis was carried out via cyclic voltammetry on low-volume (20 μL) screen-printed carbon electrodes (C-SPE) in ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ((BMIM) TFSI). An easy and rapid washing treatment allowed us to obtain the resulting MIP film, directly used for tyr electrochemical detection, carried out amperometrically. The sensor showed a linear response in the concentration range of 15-200 μM, with LOD of 1.04 µM, LOQ of 3.17 μM and good performance in selectivity, stability, and reproducibility. Tyrosine amperometric detection was also carried out in human plasma, resulting in a satisfactory recovery estimation. The work represents the first use of BT2-T4 as a functional monomer for the production of a molecularly imprinted polymer, with a green approach afforded by using a few microliters of a room temperature ionic liquid as an alternative to common organic solvents on screen-printed carbon electrodes, resulting in a valuable system that meets the green chemistry guidelines, which is today an essential criterion in both research and application field.

Recent advances in molecularly imprinted polymer-based electrochemical sensors

Molecularly imprinted polymers (MIPs) are the equivalent of natural antibodies and have been widely used as synthetic receptors for the detection of disease biomarkers. Benefiting from their excellent chemical and physical stability, low-cost, relative ease of production, reusability, and high selectivity, MIP-based electrochemical sensors have attracted great interest in disease diagnosis and demonstrated superiority over other biosensing techniques. Here we compare various types of MIP-based electrochemical sensors with different working principles. We then evaluate the state-of-the-art achievements of the MIP-based electrochemical sensors for the detection of different biomarkers, including nucleic acids, proteins, saccharides, lipids, and other small molecules. The limitations, which prevent its successful translation into practical clinical settings, are outlined together with the potential solutions. At the end, we share our vision of the evolution of MIP-based electrochemical sensors with an outlook on the future of this promising biosensing technology.

A new difunctional liquid crystal nanosurface molecularly imprinted polyitaconic acid nanoprobe for SERS/RRS determination of ultratrace melamine

In this paper, a new dimode scattering spectral method for rapid detection of ultratrace melamine (ML) in dairy products was established by coupling nanosurface molecular imprinting technology with nanocatalytic amplification reaction of liquid crystal particles. It was found that liquid crystal cholesteryl butyrate (CBU) nanosurface imprinted polymers (CBU@MIP) not only recognized ML but also catalyzed the nano indicator reaction of HAuCl4-sodium formate to produce gold nanoparticles with surface-enhanced Raman scattering (SERS) and resonance Rayleigh scattering (RRS) effect. When ML was added, it specifically combined with CBU@MIP to form CBU@MIP-ML conjugates with strong catalytic activity, and SERS and RRS signals increased linearly with the detection limits of 0.0072 pmol/L and 0.093 pmol/L respectively. The method was applied to the determination of ML in dairy products and plastic tablewares with relative standard deviation (RSD) of 2.2-4.4 % and 1.6-4.7 %, and recovery of 95.4 %-108.3 % and 95.9-108.6  % respectively.

Recent Advances in Molecularly Imprinted Polymers and Their Disease-Related Applications

Molecularly imprinted polymers (MIPs) and the imprinting technique provide polymeric material with recognition elements similar to natural antibodies. The template of choice (i.e., the antigen) can be almost any type of smaller or larger molecule, protein, or even tissue. There are various formats of MIPs developed for different medical purposes, such as targeting, imaging, assay diagnostics, and biomarker detection. Biologically applied MIPs are widely used and currently developed for medical applications, and targeting the antigen with MIPs can also help in personalized medicine. The synthetic recognition sites of the MIPs can be tailor-made to function as analytics, diagnostics, and drug delivery systems. This review will cover the promising clinical applications of different MIP systems recently developed for disease diagnosis and treatment.

Vapor-Phase Synthesis of Molecularly Imprinted Polymers on Nanostructured Materials at Room-Temperature

Molecularly imprinted polymers (MIPs) have recently emerged as robust and versatile artificial receptors. MIP synthesis is carried out in liquid phase and optimized on planar surfaces. Application of MIPs to nanostructured materials is challenging due to diffusion-limited transport of monomers within the nanomaterial recesses, especially when the aspect ratio is >10. Here, the room temperature vapor-phase synthesis of MIPs in nanostructured materials is reported. The vapor phase synthesis leverages a >1000-fold increase in the diffusion coefficient of monomers in vapor phase, compared to liquid phase, to relax diffusion-limited transport and enable the controlled synthesis of MIPs also in nanostructures with high aspect ratio. As proof-of-concept application, pyrrole is used as the functional monomer thanks to its large exploitation in MIP preparation; nanostructured porous silicon oxide (PSiO2 ) is chosen to assess the vapor-phase deposition of PPy-based MIP in nanostructures with aspect ratio >100; human hemoglobin (HHb) is selected as the target molecule for the preparation of a MIP-based PSiO2 optical sensor. High sensitivity and selectivity, low detection limit, high stability and reusability are achieved in label-free optical detection of HHb, also in human plasma and artificial serum. The proposed vapor-phase synthesis of MIPs is immediately transferable to other nanomaterials, transducers, and proteins.

Imprinted Hydrogel Nanoparticles for Protein Biosensing: A Review

Over the past decade, molecular imprinting (MI) technology has made tremendous progress, and the advancements in nanotechnology have been the major driving force behind the improvement of MI technology. The preparation of nanoscale imprinted materials, i.e., molecularly imprinted polymer nanoparticles (MIP NPs, also commonly called nanoMIPs), opened new horizons in terms of practical applications, including in the field of sensors. Currently, hydrogels are very promising for applications in bioanalytical assays and sensors due to their high biocompatibility and possibility to tune chemical composition, size (microgels, nanogels, etc.), and format (nanostructures, MIP film, fibers, etc.) to prepare optimized analyte-responsive imprinted materials. This review aims to highlight the recent progress on the use of hydrogel MIP NPs for biosensing purposes over the past decade, mainly focusing on their incorporation on sensing devices for detection of a fundamental class of biomolecules, the peptides and proteins. The review begins by directing its focus on the ability of MIPs to replace biological antibodies in (bio)analytical assays and highlight their great potential to face the current demands of chemical sensing in several fields, such as disease diagnosis, food safety, environmental monitoring, among others. After that, we address the general advantages of nanosized MIPs over macro/micro-MIP materials, such as higher affinity toward target analytes and improved binding kinetics. Then, we provide a general overview on hydrogel properties and their great advantages for applications in the field of Sensors, followed by a brief description on current popular routes for synthesis of imprinted hydrogel nanospheres targeting large biomolecules, namely precipitation polymerization and solid-phase synthesis, along with fruitful combination with epitope imprinting as reliable approaches for developing optimized protein-imprinted materials. In the second part of the review, we have provided the state of the art on the application of MIP nanogels for screening macromolecules with sensors having different transduction modes (optical, electrochemical, thermal, etc.) and design formats for single use, reusable, continuous monitoring, and even multiple analyte detection in specialized laboratories or in situ using mobile technology. Finally, we explore aspects about the development of this technology and its applications and discuss areas of future growth.

Molecularly imprinted polymer dual electrochemical sensor for the one-step determination of albuminuria to creatinine ratio (ACR)

The urinary albumin to creatinine ratio (ACR) is a convenient and accurate biomarker of chronic kidney disease (CKD). An electrochemical sensor for the quantification of ACR was developed based on a dual screen-printed carbon electrode (SPdCE). The SPdCE was modified with carboxylated multiwalled carbon nanotubes (f-MWCNTs) and redox probes of polymethylene blue (PMB) for creatinine and ferrocene (Fc) for albumin. The modified working electrodes were then molecularly imprinted with coated with polymerized poly-o-phenylenediamine (PoPD) to form surfaces that could be separately imprinted with creatinine and albumin template molecules. The seeded polymer layers were polymerized with a second coating of PoPD and the templates were removed to form two different molecularly imprinted polymer (MIP) layers. The dual sensor presented recognition sites for creatinine and albumin on different working electrodes, enabling the measurement of each analyte in one potential scan of square wave voltammetry (SWV). The proposed sensor produced linear ranges of 5.0-100 ng mL^-1 and 100-2500 ng mL^-1 for creatinine, and 5.0-100 ng mL^-1 for albumin. LODs were 1.5 ± 0.2 ng mL^-1 and 1.5 ± 0.3 ng mL^-1, respectively. The dual MIP sensor was highly selective and stable for seven weeks at room temperature. The ACRs obtained using the proposed sensor compared well (P > 0.05) with the results from immunoturbidimetric and enzymatic methods.

Critical review of polymer and hydrogel deposition methods for optical and electrochemical bioanalytical sensors correlated to the sensor's applicability in real samples

Sensors, ranging from in vivo through to single-use systems, employ protective membranes or hydrogels to enhance sample collection or serve as filters, to immobilize or entrap probes or receptors, or to stabilize and enhance a sensor's lifetime. Furthermore, many applications demand specific requirements such as biocompatibility and non-fouling properties for in vivo applications, or fast and inexpensive mass production capabilities for single-use sensors. We critically evaluated how membrane materials and their deposition methods impact optical and electrochemical systems with special focus on analytical figures of merit and potential toward large-scale production. With some chosen examples, we highlight the fact that often a sensor's performance relies heavily on the deposition method, even though other methods or materials could in fact improve the sensor. Over the course of the last 5 years, most sensing applications within healthcare diagnostics included glucose, lactate, uric acid, O₂, H⁺ ions, and many specific metabolites and markers. In the case of food safety and environmental monitoring, the choice of analytes was much more comprehensive regarding a variety of natural and synthetic toxicants like bacteria, pesticides, or pollutants and other relevant substances. We conclude that more attention must be paid toward deposition techniques as these may in the end become a major hurdle in a sensor's likelihood of moving from an academic lab into a real-world product.

Molecularly Imprinted Polymer-Based Sensor for Electrochemical Detection of Cortisol

As a steroid hormone, cortisol has a close relationship with the stress response, and therefore, can be used as a biomarker for early detection of stress. An electrochemical immunosensor is one of the most widely used methods to detect cortisol, with antibodies as its bioreceptor. Apart from conventional laboratory-based methods, the trend for cortisol detection has seemed to be exploiting antibodies and aptamers. Both can provide satisfactory performance with high selectivity and sensitivity, but they still face issues with their short shelf life. Molecularly imprinted polymers (MIPs) have been widely used to detect macro- and micro-molecules by forming artificial antibodies as bioreceptors. MIPs are an alternative to natural antibodies, which despite demonstrating high selectivity and a low degree of cross-reactivity, often also show a high sensitivity to the environment, leading to their denaturation. MIPs can be prepared with convenient and relatively affordable fabrication processes. They also have high durability in ambient conditions, a long shelf life, and the ability to detect cortisol molecules at a concentration as low as 2 ag/mL. By collecting data from the past five years, this review summarizes the antibody and aptamer-based amperometric sensors as well as the latest developments exploiting MIPs rather than antibodies. Lastly, factors that can improve MIPs performance and are expected to be developed in the future are also explained.

Recent Advances in Electrochemical Sensing Strategies for Food Allergen Detection

Food allergy has been indicated as the most frequent adverse reaction to food ingredients over the past few years. Since the only way to avoid the occurrence of allergic phenomena is to eliminate allergenic foods, it is essential to have complete and accurate information on the components of foodstuff. In this framework, it is mandatory and crucial to provide fast, cost-effective, affordable, and reliable analysis methods for the screening of specific allergen content in food products. This review reports the research advancements concerning food allergen detection, involving electrochemical biosensors. It focuses on the sensing strategies evidencing different types of recognition elements such as antibodies, nucleic acids, and cells, among others, the nanomaterial role, the several electrochemical techniques involved and last, but not least, the ad hoc electrodic surface modification approaches. Moreover, a selection of the most recent electrochemical sensors for allergen detection are reported and critically analyzed in terms of the sensors’ analytical performances. Finally, advantages, limitations, and potentialities for practical applications of electrochemical biosensors for allergens are discussed.

An insight into polyscopoletin electrosynthesis by a quality-by-design approach

Scopoletin (SP) as a functional monomer for electropolymerization has recently been investigated in the context of molecularly imprinted polymers for biosensing applications. Herein we describe an in-depth analysis of the mechanisms involved in the electropolymerization of SP toward the optimization of the experimental conditions for applications in sensor studies. PolySP films have been in situ synthesized on a standard glassy carbon electrodes by varying three independent experimental parameters, and the output of the analysis has been evaluated in terms of the resulting electroactive area and surface coverage. A quality-by-design approach including design-of-experiments principles and response surface methodology produced unbiased observations on the most relevant parameters to be controlled during the electropolymerization of SP. By combining the output of electroactive area and surface overage, we highlighted a strong dependence on the monomer concentration and scan rate. Thus, an appropriate selection of these two parameters should be sought to have an optimal electropolymerization process, leading to uniform films and homogeneous surface behavior. This study shows that the application of multi-factorial analysis in a comprehensive design of experiments allows the systematic study of polymer electrosynthesis. Therefore, this research is expected to guide further efforts in the electropolymerization of several functional monomers.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10853-022-07349-8.