Molecularly imprinted electrochemical biosensor for thrombin detection by comparing different monomers

Aim: Investigating molecularly imprinted polymers (MIPs) in electrochemical biosensors for thrombin detection, an essential protein biomarker. Comparing different monomers to showcase distinct sensitivity, specificity and stability advantages. Materials & methods: Dopamine, thionine and ethanolamine serve as monomers for MIP synthesis. Electrochemical methods and atomic force microscopy characterize sensor surfaces. Performance is evaluated, emphasizing monomer-specific electrochemical responses. Results: Monomer-specific electrochemical responses highlight dopamine's superior signal change and stability over 30 days. Notably, a low 5 pg/ml limit of detection, a broad linear range (5-200 pg/ml) and enhanced selectivity against interferents are observed. Conclusion: Dopamine-based MIPs show promise for high-performance electrochemical thrombin biosensors, suggesting significant applications in clinical diagnostics.

Towards miniaturized electrochemical sensors for monitoring of polychlorinated biphenyls

Pollution of our environment as a result of industrialization and other human activities is a growing concern due to the harmful effects of most chemicals that are released into the environment. Of particular interest are the persistent organic pollutants (POPs) that are reported to be toxic and build up in the environment due to their persistence. Among the POPs are polychlorinated biphenyls (PCBs), which were widely used in the past in various applications ranging from additives in pesticides to dielectric fluids in electrical equipment. As a way of protecting the one health trilogy (environment, human and animal health), their determination in the environment is a paramount call that has seen researchers continue to provide advanced technologies towards achieving this goal. These technologies involve the conventional gold standard gas chromatography systems coupled to sensitive detectors that can detect trace level concentrations. They have come in handy in monitoring of PCBs but their application for routing monitoring may not be sustainable because of the cost of operation associated with them and the need for experts to run the equipment. As a result, there is need for affordable systems that are still able to achieve the required sensitivity for routine monitoring and real-time data acquisition. Sensor systems fit very well in this category since they can be miniaturized for affordability and portray many other desirable features. PCBs as environmentally relevant environmental pollutants have received minimal attention with regards to sensor development and this review highlights the efforts that have been made so far. It provides in-depth discussions on electrochemical sensors and the various modifications that have been employed to date to achieve detection of PCBs at low concentrations as well as the future prospects in remote and routine monitoring.

Epitope imprinted polymeric materials: application in electrochemical detection of disease biomarkers

Epitope imprinting is a promising method for creating specialized recognition sites that resemble natural biorecognition elements. Epitope-imprinted materials have gained a lot of attention recently in a variety of fields, including bioanalysis, drug delivery, and clinical therapy. The vast applications of epitope imprinted polymers are due to the flexibility in choosing monomers, the simplicity in obtaining templates, specificity toward targets, and resistance to harsh environments along with being cost effective in nature. The "epitope imprinting technique," which uses only a tiny subunit of the target as the template during imprinting, offers a way around various drawbacks inherent to biomacromolecule systems i.e., traditional molecular imprinting techniques with regards to the large size of proteins, such as the size, complexity, accessibility, and conformational flexibility of the template. Electrochemical based sensors are proven to be promising tool for the quick, real-time monitoring of biomarkers. This review unravels epitope imprinting techniques, approaches, and strategies and highlights the applicability of these techniques for the electrochemical quantification of biomarkers for timely disease monitoring. In addition, some challenges are discussed along with future prospective developments.

Towards Development of Molecularly Imprinted Electrochemical Sensors for Food and Drug Safety: Progress and Trends

Due to their advantages of good flexibility, low cost, simple operations, and small equipment size, electrochemical sensors have been commonly employed in food safety. However, when they are applied to detect various food or drug samples, their stability and specificity can be greatly influenced by the complex matrix. By combining electrochemical sensors with molecular imprinting techniques (MIT), they will be endowed with new functions of specific recognition and separation, which make them powerful tools in analytical fields. MIT-based electrochemical sensors (MIECs) require preparing or modifying molecularly imprinted polymers (MIPs) on the electrode surface. In this review, we explored different MIECs regarding the design, working principle and functions. Additionally, the applications of MIECs in food and drug safety were discussed, as well as the challenges and prospects for developing new electrochemical methods. The strengths and weaknesses of MIECs including low stability and electrode fouling are discussed to indicate the research direction for future electrochemical sensors.

Dual-template rectangular nanotube molecularly imprinted polypyrrole for label-free impedimetric sensing of AFP and CEA as lung cancer biomarkers

A high-performance sensing layer based on dual-template molecularly imprinted polymer (DMIP) was fabricated and successfully applied for one-by-one detection of carcinoembryonic antigen (CEA) and alpha-fetoprotein (AFP) as lung cancer biomarkers. The plastic antibodies of AFP and CEA were created into the electropolymerized polypyrrole (PPy) on a fluorine-doped tin oxide (FTO) electrode. Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) tests were performed to pursue the formation and characterization of the sensing layer. Methyl orange (MO) increased the conductivity of PPy and induced the formation of MO doped PPy (PPy-MO) rectangular-shaped nanotubes. Using impedimetric detection, the rebinding of the template antigens was evaluated, the charge transfer resistance increased as the concentration of AFP and CEA increased. The linear dynamic ranges of 5-10⁴ and 10-10⁴ pg mL^-1 and detection limits of 1.6 and 3.3 pg mL^-1 were obtained for CEA and AFP, respectively. Given satisfactory results in the determination of AFP and CEA in the human serum samples, high sensitivity, and good stability of DMIP sensor made it a promising method for sensing of AFP and CEA in serum samples.

Sensitive and selective detection of glycoprotein based on dual-signal and dual-recognition electrochemical sensing platform

Glycoproteins play extraordinary roles in biology and clinic. The specifically sensitive detection of glycoproteins by electrochemical methods is still a challenging task due to their poor electro-activity and sensitive nature to environment. In this work, ovalbumin (OVA), a model glycoprotein, was sensitively detected by a molecularly imprinted polymer (MIP) based electrochemical sensor, which was prepared by electropolymerizing 3-thiophene boric acid in the presence of OVA. Due to boronate affinity, the rebound OVA interacted with ferrocene boric acid (Fc-BA) to construct a sandwich structural sensing platform. Dual-recognition elements, imprinted effect and the boronate affinity, enabled the sensor to recognize OVA from other proteins. The rebinding of OVA caused the current changes of thionine and Fc-BA, which were combined as a dual-signal for OVA sensitive detection with a low limit of detection of 0.82 pg/mL (S/N = 3). The good performances of sensor indicated its potential applications in clinical diagnosis and other related fields.

Preparation of Dual-Template Epitope Imprinted Polymers for Targeted Fluorescence Imaging and Targeted Drug Delivery to Pancreatic Cancer BxPC-3 Cells

Molecularly imprinted polymers were commonly used for drug delivery. However, single-template molecularly imprinted polymers often fail to achieve both drug delivery and precise targeting. To address this issue, a dual-template molecularly imprinted polymer nanoparticle used for targeted diagnosis and drug delivery for pancreatic cancer BxPC-3 cells (FH-MIPNPs) was prepared. In the FH-MIPNPs, the 71-80 peptide of human fibroblast growth-factor-inducible 14 modified with glucose (Glu-FH) and bleomycin (BLM) were used as templates simultaneously, so that the FH-MIPNPs could load BLM and bind to the BxPC-3 cells, which overexpress human fibroblast growth-factor-inducible 14 (FN14). Targeted imaging experiments in vitro show that the FH-MIPNPs could specifically target BxPC-3 cells and that there is no targeting effect on cells without expression of FN14. In vivo antitumor experiment results demonstrated that the FH-MIPNP-loaded BLM (FH-MIPNPs/BLM) could inhibit the growth of xenografts tumor of BxPC-3 (tumor volume increased to 1.05×), which shows that FH-MIPNPs/BLM had obvious targeted therapeutic effect compared to the other three control groups of BLM, FH-NIPNPs/BLM, and physiological saline (tumor volume increased to 1.5×, 1.6×, and 2.4×, respectively). What is more, FH-MIPNPs have low biotoxicity through toxicity experiments in vitro and in vivo, which is favorable toward making molecularly imprinted polymers an effective platform for tumor-targeted imaging and therapy.

A boronic acid carbon nanodots/poly(thionine) sensing platform for the accurate and reliable detection of NADH

In this work, a novel electrochemical sensing platform was designed and fabricated by the modification of boronic acid functionalized carbon nanodots (B-CNDs) and poly(thionine) (pTHI) on an electrode surface. B-CNDs can not only accelerate electron transfer but also covalently interact with cis-diol groups of dihydronicotinamide adenine dinucleotide (NADH) through functionalized boronic acid groups. Meanwhile, pTHI served as an inner reference element to provide a built-in correction, which enabled the sensor to detect NADH with high accuracy and reliability based on a ratiometric signal (∆I_NADH/∆I_THI). The electrochemical experimental results demonstrated that the ratiometric strategy-based sensor possessed good selectivity and high sensitivity. A linear range of 5.0 × 10^-7 - 2.0 × 10^-4 mol/L for NADH detection was obtained with a limit of detection of 1.5 × 10^-7 mol/L. The sensor has been applied to analyze NADH in human serum samples with satisfactory results. The simple and effective ratiometric strategy reported here can be further used to prepare electrochemical sensors for selective, sensitive, and reliable detection of other cis-diol compounds.

Photoelectrochemical determination of malathion by using CuO modified with a metal-organic framework of type Cu-BTC

A photoelectrochemical (PEC) sensor was constructed for the detection of non-electroactive malathion. It is based on the use of a hierarchical CuO material derived from a Cu-BTC metal-organic framework (where BTC stands for benzene-1,3,5-tricarboxylic acid). The modified CuO was obtained by calcination of Cu-BTC at a high temperature (300 °C) and possesses a high photocurrent conversion efficiency. Under irradiation with visible light and in the presence of malathion, the formation of the CuO-malathion complex on the CuO gave rise to an increase in steric hindrance. This results in a decrease in photocurrent. This novel PEC detection method has a lower detection limit of 8.6 × 10^-11 mol L^-1 and a wide linear range (1.0 × 10^-10 ~ 1.0 × 10^-5 mol L^-1). Graphical abstract Schematic presentation of the Cu-BTC MOF derived photoelectrochemical sensor for non-electroactive malathion detection.

Au-polythionine nanocomposites: a novel mediator for bisphenol A dual-signal assay based on imprinted electrochemical sensor

In this work, a novel electrochemical sensor was developed by the modification of poly(p-aminobenzene sulfonic acid) (pABSA), Au-polythionine (Au-pTH) nanowires, and molecularly imprinted polymer (MIP) on glassy carbon electrode surface for bisphenol A (BPA) detection. The results of characterizations including scanning electron microscope, transmission electron microscopy, Fourier transform infrared spectra, and X-ray diffraction showed the successful synthesis of helical structural Au-pTH nanowires, which acted as an electro-active probe for BPA detection. Cyclic voltammetry results illustrated that the modified pABSA, Au-pTH, and MIP endowed the sensor with good electrocatalytic activity, the second current signal, and recognition ability, respectively. Since the imprinted cavities provided electron transfer channels for thionine (TH) redox, the peak current of TH can be found in a blank electrolyte. The added BPA molecules can be rebound in imprinted cavities, which are oxidized and then display its current. The rebound BPA molecules in turn blocked the electron transfer channels for TH redox, resulting in the decrease of TH current. A double signal defined, as the sum of the changes of TH current (∆i_TH|) and BPA current (|∆i_BPA|) (|∆i_TH|+|∆i_BPA|), was employed as the detected signal for BPA sensitive detection, which was linearly proportional to the logarithm of concentration of BPA ranging from 8.0 × 10^-8 to 1.0 × 10^-4 mol/L with a limit of detection of 3.8 × 10^-8 mol/L (S/N = 3) in a weakly acidic solution. Moreover, the natural recognition ability of MIP enabled the sensor to selectively detect BPA from its analogues. The proposed dual-signal strategy-based sensor provided a feasible tool for rapid, sensitive, and selective determination of BPA. Graphical abstract.

Defect- and phase-engineering of Mn-mediated MoS2 nanosheets for ultrahigh electrochemical sensing of heavy metal ions: chemical interaction-driven in situ catalytic redox reactions

An ultrasensitive electrochemical detection of heavy metal ions is achieved via defect- and phase-engineering of Mn-mediated MoS₂ nanosheets.