Preparation of IgG imprinted polymers by metal-free visible-light-induced ATRP and its application in biosensor

Ultrasensitive self-powered biosensor with facile chemical signal amplification strategy using hydrogen peroxide-triggered silver oxidation reaction

The amplification strategies used for self-powered biosensor based on biofuel cell (BFC-SPB) need to be further developed. Because the currently developed strategies utilized the complicated hybridization of DNA or poorly readable current signal of capacitors for amplification, which limits the practical application in public health emergencies. Here, we present a facile chemical amplification strategy for BFC-SPB. The 5-min amplification was triggered by simply adding H2O2 solution dropwise to the sensing cathode after the formation of the immune sandwich. The Ag NP of immunoprobe were oxidized to Ag(I), which can be served as the electron acceptor of the cathode. The amount of immunoprobe was positively correlated with that of the antigen, resulting in corresponding and high concentration of Ag(I) after the amplification, which enhanced the ability of the cathode as the electron acceptor. Meanwhile the glucose oxidation reaction (GOR) was performed on the bioanode modified with glucose oxidase (GOx). After assembling the bioanode and sensing cathode, the open circuit voltage of the BFC-SPB, measured by digital multimeter, distinctly rised with the elevated concentration of the antigen. To demonstrate the proof of concept, immunoglobulin G (IgG), selecting as a model analyte, was sensitively detected using this method. Result indicated that the limit of detection was 4.4 fg mL-1 (0.03 amol mL-1) in the linear range of 1 pg mL-1-10 μg mL-1. This work initiates a brand-new way of chemical amplification strategy for BFC-SPB, and offers a promising platform for practical applications.

Molecularly imprinted polymers: A closer look at the template removal and analyte binding

Molecularly imprinted polymers (MIPs), which first appeared over half a century ago, are now attracting considerable attention as artificial receptors, particularly for sensing. MIPs, especially applied to biomedical analysis in biofluids, contribute significantly to patient diagnosis at the point of care, thereby allowing health monitoring. Despite the importance given to MIPs, removal of templates and binding of analytes have received little attention and are currently the least focused steps in MIP development. This critical review is dedicated to a comprehensive analysis and discussion of cutting-edge concepts and methodologies in the removal and binding steps pertaining to various types of analytes, including ions, molecules, epitopes, proteins, viruses, and bacteria. The central objective of this review is to comprehensively examine and discuss a range of removal methods, including soxhlet extraction, immersion, microwave-assisted technique, ultrasonication, electrochemical approach, and proteolytic digestion, among others. Additionally, we will explore various binding methods, such as soaking, drop-casting, and batch sorption, to provide a comprehensive overview of the subject. Furthermore, the current challenges and perspectives in removal and binding are highlighted. Our review, at the interface of chemistry and sensors, will offer a wide range of opportunities for researchers whose interests include MIPs, (bio)sensors, analytical chemistry, and diagnostics.

A rapid abiotic/biotic hybrid sandwich detection for trace pork adulteration in halal meat extract

In this study, we prepared molecularly imprinted polymer nanogels with good affinity for the Fc domain of immunoglobulin G (IgG) using 4-(2-methacrylamidoethylaminomethyl) phenylboronic acid as a modifiable functional monomer for post-imprinting in-cavity modification of a fluorescent dye (F-Fc-MIP-NGs). A novel nanogel-based biotic/abiotic hybrid sandwich detection system for porcine serum albumin (PSA) was developed using F-Fc-MIP-NGs as an alternative to a secondary antibody for fluorescence detection and another molecularly imprinted polymer nanogel capable of recognizing PSA (PSA-MIP-NGs) as a capturing artificial antibody, along with a natural antibody toward PSA (Anti-PSA) that was used as a primary antibody. After incubation of PSA and Anti-PSA with F-Fc-MIP-NGs, the PSA/Anti-PSA/F-Fc-MIP-NGs complex was captured by immobilized PSA-MIP-NGs for fluorescence measurements. The analysis time was less than 30 min for detecting pork adulteration of 0.01 wt% in halal beef and lamb meats. The detection limit was comparable to that of frequently used immunoassays. Therefore, we believe that this method is a promising, sensitive, and rapid detection method for impurities in real samples and could be a simple, inexpensive, and rapid alternative to conventional methods that have cumbersome procedures of 4 hours or more.

Peptide-crosslinked molecularly imprinted polymers for efficient separation of immunoglobulin G from human serum

Low-cost and highly effective methods are highly desirable to replace the costly ethanol fractionation and affinity chromatography in IgG isolation from human plasma. Molecularly imprinted polymers (MIPs) of IgG are potential candidates, however, they still suffer from severe problems such as difficult template removal and low imprinting efficiency. Here, a recently developed strategy was adopted to overcome these problems. The MIPs were synthesized using poly(L-glutamic acid) (PLGA) peptide crosslinkers instead of commonly used crosslinkers, such as N,N-methylenebisacrylamide (BIS). Because of the pH-induced helix-coil transition and the precise folding of the peptide segments in the polymers, the imprint cavities can be enlarged by adjusting the pH from 5.0 to 7.0, but their original size and shape are restored when the pH is adjusted back. Therefore, the IgG template can be eluted completely under mild conditions, and significantly improved imprinting efficiency can be achieved. Compared with BIS-crosslinked MIP, 8.6 times more binding sites can be created by molecular imprinting PLGA-crosslinked MIP. The factors influencing the performance of the MIP were studied systematically. An optimized MIP with a high adsorption capacity (612.5 mg g^-1), high IF (4.92), and high selectivity was obtained. The adsorption capacity and selectivity of the MIP are much higher than the previously reported IgG MIPs. Because of its high adsorption capacity and selectivity, it can separate IgG from human serum effectively, affording high purity products.

Rabbit IgG-imprinted nanoMIPs by solid phase synthesis: the effect of cross-linkers on their affinity and selectivity

Solid phase synthesis (SPS) of molecularly imprinted nanopolymers (nanoMIPs) represents an innovative method to prepare nanomaterials with tailor-made molecular recognition properties towards peptides and proteins. The synthesis of nanoMIPs by SPS usually involves a pre-polymerization formulation, where the cross-linker is invariably N,N'-methylen-bis-acrylamide (BIS). To date, the effect of cross-linkers on the binding properties of nanoMIPs prepared using cross-linkers other than BIS has never been reported. In this work, in order to investigate the effect of different cross-linkers in protein-imprinted nanoMIPs prepared by SPS, alongside BIS we considered other similar cross-linkers: N,N'-ethylene dimethacrylamide (EDAM), N,O-bis-methacryloylethanolamine (NOBE), ethylene glycol dimethacrilate (EDMA) and glycerol dimethacrylate (GDMA), replacing BIS with them in pre-polymerization mixtures. The synthetized nanoMIPs were homogeneous, with a polydispersity index of 0.24-0.30 and a mean diameter of 129-169 nm in water. The binding properties of the nanoMIPs were measured via equilibrium partition experiments with the template, rabbit IgG (RIgG), and the selectivity was evaluated with respect to bovine IgG (BIgG), bovine serum albumin (BSA) and hen egg lysozyme (LZM). The experimental results show that all the cross-linkers, with the exception of EDMA, endowed nanoMIPs with high binding affinities for the template (BIS: 16.0 × 10⁶ mol^-1 L, EDAM: 8.8 × 10⁶ mol^-1 L, NOBE: 15.8 × 10⁶ mol^-1 L, and GDMA: 12.8 × 10⁶ mol^-1 L), medium to high imprinting factors (BIS: 12.3, EDAM: 5.5, NOBE: 7.2, and GDMA: 11.6) and good selectivity towards other proteins but markedly dependent on the structure of the cross-linker, confirming the importance of the latter in the SPS of imprinted nanopolymers.

An electrochemical biosensor based on ARGET ATRP with DSN-assisted target recycling for sensitive detection of tobacco mosaic virus RNA

Herein, an electrochemical biosensor for detecting tobacco mosaic virus (TMV) RNA is constructed by activator regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) combined with duplex-specific nuclease (DSN)-assisted target recycling. First, the captured DNA (cDNA) is self-assembled on the electrode surface and hybridizes with the TMV RNA (tRNA) to form cDNA/tRNA hybrids. And then the initiator of ARGET ATRP (α-bromoisobutyric acid, BMP) is attached to the cDNA via an amide bond and later triggers ARGET ATRP. Many electroactive monomers (ferrocenylmethyl methacrylate, FMMA) are polymerized and a remarkable electrical signal response of ferrocene (Fc) is obtained. However, with the present of DSN, DSN cleaves the cDNA/tRNA hybrid and releases tRNA to hybridize with another cDNA, thereby causing significant shortening of the length of the cDNA. The number of polymer chains on the electrode surface is drastically reduced, which is followed by a noticeable reduction in the signal of Fc. The method shows high sensitivity, superior selectivity, excellent stability and good reproducibility under optimal conditions with the limit of detection (LOD) of 2.9 fM. Furthermore, the biosensor showed satisfactory applicability in detecting tRNA in real samples, thereby demonstrating the potential of the method for practical TMV RNA detection.

Ion-Imprinted Polymer-on-a-Sensor for Copper Detection

The accumulation of metal ions in the body is caused by human activities and industrial uses. Among these metal ions, copper is the third most abundant ion found in the human body and is indispensable for health because it works as a catalyst in the iron absorption processes. However, high doses of copper ions have been reported to generate various diseases. Different types of sensors are used to detect metal ions for several applications. To design selective and specific recognition sites on the sensor surfaces, molecular imprinting is one of the most used alteration methods to detect targets by mimicking natural recognition molecules. In this study, an ion-imprinted polymer-integrated plasmonic sensor was prepared to selectively detect copper (Cu(II)) ions in real-time. Following different characterization experiments, the Cu(II)-imprinted plasmonic sensor was employed for kinetic, selectivity, and reusability studies. According to the results, it was observed that this sensor can measure with 96% accuracy in the Cu(II) concentration range of 0.04-5 μM in buffer solution. The limit of detection and limit of quantification values were computed as 0.027 µM and 0.089 µM. The results also showed that this plasmonic sensor works successfully not only in a buffer solution but also in complex media such as plasma and urine.

Recent advances in the biosensors application for the detection of bacteria and viruses in wastewater

The presence of disease-causing pathogens in wastewater can provide an excellent diagnostic tool for infectious diseases. Biosensors are far superior to conventional methods used for regular infection screening and surveillance testing. They are rapid, sensitive, inexpensive portable and carry no risk of exposure in their detection schemes. In this context, this review summarizes the most recently developed biosensors for the detection of bacteria and viruses in wastewater. The review also provides information on the new detection methods aimed at screening for SARS-CoV-2, which has now caused more than 4 million deaths. In addition, the review highlights the potential behind on-line and real-time detection of pathogens in wastewater pipelines. Most of the biosensors reported were not targeted to wastewater samples due to the complexity of the matrix. However, this review highlights on the performance factors of recently developed biosensors and discusses the importance of nanotechnology in amplifying the output signals, which in turn increases the accuracy and reliability of biosensors. Current research on the applicability of biosensors in wastewater promises a dramatic change to the conventional approach in the field of medical screening.

Photoinduced Organocatalyzed Atom Transfer Radical Polymerization (O-ATRP): Precision Polymer Synthesis Using Organic Photoredox Catalysis

The development of photoinduced organocatalyzed atom transfer radical polymerization (O-ATRP) has received considerable attention since its introduction in 2014. Expanding on many of the advantages of traditional ATRP, O-ATRP allows well-defined polymers to be produced under mild reaction conditions using organic photoredox catalysts. As a result, O-ATRP has opened access to a range of sensitive applications where the use of a metal catalyst could be of concern, such as electronics, certain biological applications, and the polymerization of coordinating monomers. However, key limitations of this method remain and necessitate further investigation to continue the development of this field. As such, this review details the achievements made to-date as well as future research directions that will continue to expand the capabilities and application landscape of O-ATRP.

Highly sensitive and specific assessment of ochratoxin A in herbal medicines via activator regeneration by electron transfer ATRP

A signal-off fluorescence biosensor for highly sensitive detection of OTA was constructed via the ARGET ATRP signal amplification strategy.

Customizable molecular recognition: advancements in design, synthesis, and application of molecularly imprinted polymers

Molecularly imprinted polymers (MIPs) are unlocking the door to synthetic materials that are capable of molecular recognition.

Metal-Free Organocatalyzed Atom Transfer Radical Polymerization: Synthesis, Applications, and Future Perspectives

Reversible deactivation radical polymerization (RDRP) is a class of powerful techniques capable of synthesizing polymers with a well-defined structure, properties, and functionalities. Among the available RDRPs, ATRP is the most investigated. However, the necessity of a metal catalyst represents a drawback and limits its use for some applications. O-ATRP emerged as an alternative to traditional ATRP that uses organic compounds that catalyze polymerization under light irradiation instead of metal. The friendly nature and the robustness of O-ATRP allow its use in the synthesis of tailorable advanced materials with unique properties. In this review, the fundamental aspects of the reductive and oxidative quenching mechanism of O-ATRP are provided, as well as insights into each component and its role in the reaction. Besides, the breakthrough recent studies that applied O-ATRP for the synthesis of functional materials are presented, which illustrate the significant potential and impact of this technique across diverse fields.