Molecularly imprinted polymer nanogel-based fluorescence sensing of pork contamination in halal meat extracts

Unravelling the Potential of Zwitterionic Polymers in Molecular Imprinting

Molecularly imprinted polymers (MIPs) are a class of molecular receptors that are the closest imitation of biological receptors. They are often called "artificial enzymes". The capability of the MIPs to bind bioactive molecules under specific conditions creates molecular imprinting technology as having considerable potential for customized applications. Polymerization in the presence of a "template" molecule with the assistance of monomers, cross-linkers, and initiators leads to MIPs on extraction of the template molecule from the polymeric matrices. Conventionally neutral monomers were utilized for molecular imprinting. Recently, zwitterionic polymers, having innumerable advantages over nonionic polymers, were realized to be an advantageous choice as a polymeric matrix for imprinting. This review article presents an overview of sulfobetaine, carbobetaine, and phosphobetaine polymers as imprinting matrices for a range of template(s). Zwitterionic polymers are accomplished with biocompatibility, low cytotoxicity, negligible immunogenicity, systematic stability, and long circulation time, and can alleviate quick recognition by the immune system and delayed blood clearance from the body. They can be a fitting candidate for imprinting, especially of biomolecules. The molecular imprinting work on zwitterionic polymers is presented here, which will encourage researchers working in this area.

Facile biotic/abiotic sandwich detection system for the highly sensitive detection of human serum albumin and glycated albumin

Quantifying glycated albumin (GA) levels in the blood is crucial for diagnosing diabetes because they strongly correlate with blood glucose concentration. In this study, a biotic/abiotic sandwich assay was developed for the facile, rapid, and susceptible detection of human serum albumin (HSA) and GA. The proposed sandwich detection system was assembled using a combination of two synthetic polymer receptors and natural antibodies. Molecularly imprinted polymer nanogels (MIP-NGs) for HSA (HSA-MIP-NGs) were used to mimic capture antibodies, whereas antibodies for HSA or GA were used as primary antibodies and fluorescent signaling MIP-NGs for the Fc domain of IgG (F-Fc-MIP-NGs) were used as a secondary antibody mimic to indicate the binding events. The HSA/anti-HSA/F-Fc-MIP-NGs complex, formed by incubating HSA and anti-HSA antibodies with F-Fc-MIP-NGs, was captured by HSA-MIP-NGs immobilized on the chips for fluorescence measurements. The analysis time was less than 30 min, and the limit of detection was 15 pM. After changing the anti-HSA to anti-GA (monoclonal antibody), the fluorescence response toward GA exceeded that of HSA, indicating successful GA detection using the proposed sandwich detection system. Therefore, the proposed system could change the detection property by changing a primary antibody, indicating that this system can be applied to various target proteins and, especially, be a powerful approach for facile and rapid analysis methods for proteins with structural similarity.

Advanced Halal Authentication Methods and Technology for Addressing Non-Compliance Concerns in Halal Meat and Meat Products Supply Chain: A Review

Religious beliefs have a significant impact on consumer preferences, particularly in relation to food choices. Islam, like other religions, imposes specific dietary guidelines, notably regarding meat and meat products. However, ensuring compliance with halal standards across the entire meat and meat products supply chain presents considerable challenges. Instances of non-compliance, including improper slaughtering techniques, mislabeling, adulteration, and contamination, have caused concerns about the authenticity of halal status. To address these concerns, this review explores recent advancements in halal authentication methods and technology, focusing on practical objectives aimed at addressing non-compliance issues. It categorizes methods into four main areas of non-compliance concerns, providing a unique perspective compared to earlier reviews that primarily examined the progression of analytical methods. This classification offers a comprehensive analysis of the field's current status, facilitating the identification of research gaps and strategic recommendations for enhancing future halal authentication methods. Through the implementation of this novel approach, the review seeks to promote the development of a more robust framework for evaluating halal meat and meat products, safeguarding consumer trust and ensuring adherence to religious dietary guidelines in the future.

One-Pot Preparation of Ratiometric Fluorescent Molecularly Imprinted Polymer Nanosensor for Sensitive and Selective Detection of 2,4-Dichlorophenoxyacetic Acid

The development of fluorescent molecular imprinting sensors for direct, rapid, and sensitive detection of small organic molecules in aqueous systems has always presented a significant challenge in the field of detection. In this study, we successfully prepared a hydrophilic colloidal molecular imprinted polymer (MIP) with 2,4-dichlorophenoxyacetic acid (2,4-D) using a one-pot approach that incorporated polyglycerol methacrylate (PGMMA-TTC), a hydrophilic macromolecular chain transfer agent, to mediate reversible addition-fragmentation chain transfer precipitation polymerization (RAFTPP). To simplify the polymerization process while achieving ratiometric fluorescence detection, red fluorescent CdTe quantum dots (QDs) and green fluorescent nitrobenzodiazole (NBD) were introduced as fluorophores (with NBD serving as an enhancer to the template and QDs being inert). This strategy effectively eliminated background noise and significantly improved detection accuracy. Uniform-sized MIP microspheres with high surface hydrophilicity and incorporated ratiometric fluorescent labels were successfully synthesized. In aqueous systems, the hydrophilic ratio fluorescent MIP exhibited a linear response range from 0 to 25 μM for the template molecule 2,4-D with a detection limit of 0.13 μM. These results demonstrate that the ratiometric fluorescent MIP possesses excellent recognition characteristics and selectivity towards 2,4-D, thus, making it suitable for selective detection of trace amounts of pesticide 2,4-D in aqueous systems.

Double lateral flow immunosensing of undeclared pork and chicken components of meat products

Adulteration of meat products is a serious problem in the modern society. Consumption of falsified meat products can be hazardous to health and/or lead to violating religious dietary principles. To identify such products, rapid and simple test systems for point-of-need detection are in demand along with complex laboratory methods. This study presents the first double lateral flow (immunochromatographic) test system, which allows simultaneous revealing two prevalent types of falsifications-undeclared addition of pork and chicken components to meat products. In the proposed test system, porcine myoglobin (MG) and chicken immunoglobulin Y (IgY) were used as specific biomarkers recognizable by antibodies. Within the optimization of the analysis, the concentrations of the immune reagents and regimes of their application on the working membrane were selected, which provided minimal limits of detection (LODs) for both analytes. The developed test system enables the detection of MG and IgY with the LODs of 10 and 12 ng/mL, respectively, which accords to addition of 0.1% of the undeclared meat compounds. The applicability of the test system to control the composition of raw meat mixtures and cooked food products was confirmed. The developed approach can be considered as a promising tool for monitoring composition of meat products.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-024-05944-y.

Emerging trends in sensors based on molecular imprinting technology: Harnessing smartphones for portable detection and recognition

Molecular imprinting technology (MIT) has become a promising recognition technology in various fields due to its specificity, high efficiency, stability and eco-friendliness in the recognition of target. Molecularly imprinted polymers (MIPs), known as 'artificial receptors', are shown similar properties to natural receptors as a biomimetic material. The selectivity of recognition for targets can be greatly improved when MIPs are introduced into sensors, as known that MIPs, are suitable for the pretreatment and analysis of trace substances in complex matrix samples. At present, various sensors has been developed by the combination with MIPs for detecting and identifying trace compounds, biological macromolecules or other substances, such as optical, electrochemical and piezoelectric sensors. Smart phones, with their built-in sensors and powerful digital imaging capabilities, provide a unique platform for the needs of portability and instant detection. MIP sensors based on smart phones are expected to become a new research direction in the future. This review discusses the latest applications of MIP sensors in the field of detection and recognition in recent years, summarizes the frontier progress of MIP sensor research based on smart phones in the past two years, and points out the challenges, limitations and future development prospects.

Post-imprinting modification of molecularly imprinted polymer for proteins detection: A review

Inspired by protein post-translational modification (PTM), post-imprinting modification (PIM) has been proposed and developed to prepare novel molecularly imprinted polymers (MIPs), which are similar to functionalized biosynthetic proteins. The PIM involves site-directed modifications in the imprinted cavity of the MIP, such as introducing high-affinity binding sites and introducing fluorescent signal molecules. This modification makes the MIP further functionalized and improves the shortcomings of general molecular imprinting, such as single function, low selectivity, low sensitivity, and inability to fully restore the complex function of natural antibodies. This paper describes the characteristics of PIM strategies, reviews the latest research progress in the recognition and detection of protein biomarkers such as lysozyme, prostate-specific antigen, alpha-fetoprotein, human serum albumin, and peptides, and further discusses the importance, main challenges, and development prospects of PIM. The PIM technology has the potential to develop a new generation of biomimetic recognition materials beyond natural antibodies. It can be used in bioanalysis and other multitudinous fields for its unique features in molecule recognition.

Molecular imprinting-based indirect fluorescence detection strategy implemented on paper chip for non-fluorescent microcystin

Fluorescence analysis is a fast and sensitive method, and has great potential application in trace detection of environmental toxins. However, many important environmental toxins are non-fluorescent substances, and it is still a challenge to construct a fluorescence detection method for non-fluorescent substances. Here, by means of charge transfer effect and smart molecular imprinting technology, we report a sensitive indirect fluorescent sensing mechanism (IFSM) and microcystin (MC-RR) is selected as a model target. A molecular imprinted thin film is immobilized on the surface of zinc ferrite nanoparticles (ZnFe2O4 NPs) by using arginine, a dummy fragment of MC-RR. By implementation of IFSM on the paper-based microfluidic chip, a versatile platform for the quantitative assay of MC-RR is developed at trace level (the limit of detection of 0.43 μg/L and time of 20 min) in real water samples without any pretreatment. Importantly, the proposed IFSM can be easily modified and extended for the wide variety of species which lack direct interaction with the fluorescent substrate. This work offers the potential possibility to meet the requirements for the on-site analysis and may explore potential applications of molecularly imprinted fluorescent sensors.

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.

A voltammetric immunosensor based on a nanoporous alumina millirod for detection of porcine serum albumin

A voltammetric immunosensor was developed for detection of porcine serum albumin (PSA) to identify raw meat products adulterated with pork. A novel strategy to fabricate multiple individual nanoporous alumina (NPA) millirods (length, 5.0 mm; diameter, 1.0 mm) as the biorecognition platform is described. Each NPA millirod was covalently bioconjugated with anti-PSA capturing antibodies (α-PSAC). Following immunocapture, the PSA bound to the α-PSAC/NPA millirod bioconjugate were tagged with gold nanoparticles (AuNPs) functionalized with anti-PSA detection antibodies as the signaling probe. Subsequently, the AuNPs were voltammetrically analyzed to quantify the target PSA. The immunosensor exhibited 100 % specificity and high sensitivity to PSA with a limit of detection (LoD) of 50 (range, 0-1000) pg/mL (R² = 0.9907). Real-world applicability was successfully validated using pork/beef adulterated mixtures with a LoD of 0.05 % (w/w). Overall, the detection performance of the proposed immunosensor was excellent and, thus, is suitable for surveillance of food safety and quality.

Molecularly Imprinted Polymer-Based Luminescent Chemosensors

Molecularly imprinted polymer (MIP)-based luminescent chemosensors combine the advantages of the highly specific molecular recognition of the imprinting sites and the high sensitivity with the luminescence detection. These advantages have drawn great attention during the past two decades. Luminescent molecularly imprinted polymers (luminescent MIPs) towards different targeted analytes are constructed with different strategies, such as the incorporation of luminescent functional monomers, physical entrapment, covalent attachment of luminescent signaling elements on the MIPs, and surface-imprinting polymerization on the luminescent nanomaterials. In this review, we will discuss the design strategies and sensing approaches of luminescent MIP-based chemosensors, as well as their selected applications in biosensing, bioimaging, food safety, and clinical diagnosis. The limitations and prospects for the future development of MIP-based luminescent chemosensors will also be discussed.

Recent Advances in the Biomedical Applications of Functionalized Nanogels

Nanomaterials have been extensively used in several applications in the past few decades related to biomedicine and healthcare. Among them, nanogels (NGs) have emerged as an important nanoplatform with the properties of both hydrogels and nanoparticles for the controlled/sustained delivery of chemo drugs, nucleic acids, or other bioactive molecules for therapeutic or diagnostic purposes. In the recent past, significant research efforts have been invested in synthesizing NGs through various synthetic methodologies such as free radical polymerization, reversible addition-fragmentation chain-transfer method (RAFT) and atom transfer radical polymerization (ATRP), as well as emulsion techniques. With further polymeric functionalizations using activated esters, thiol-ene/yne processes, imines/oximes formation, cycloadditions, nucleophilic addition reactions of isocyanates, ring-opening, and multicomponent reactions were used to obtain functionalized NGs for targeted delivery of drug and other compounds. NGs are particularly intriguing for use in the areas of diagnosis, analytics, and biomedicine due to their nanodimensionality, material characteristics, physiological stability, tunable multi-functionality, and biocompatibility. Numerous NGs with a wide range of functionalities and various external/internal stimuli-responsive modalities have been possible with novel synthetic reliable methodologies. Such continuous development of innovative, intelligent materials with novel characteristics is crucial for nanomedicine for next-generation biomedical applications. This paper reviews the synthesis and various functionalization strategies of NGs with a focus on the recent advances in different biomedical applications of these surface modified/functionalized single-/dual-/multi-responsive NGs, with various active targeting moieties, in the fields of cancer theranostics, immunotherapy, antimicrobial/antiviral, antigen presentation for the vaccine, sensing, wound healing, thrombolysis, tissue engineering, and regenerative medicine.

Photonic crystal sensor for melamine based on magnetic molecularly imprinted nanoparticles self-assembled with an amphiphilic random copolymer

Magnetic molecularly imprinted nanoparticles (MMINPs) were obtained with a one-step process through miniemulsion self-assembly using an amphiphilic random copolymer as both an emulsifier and MMINP coating, oleic acid-modified magnetite nanoparticles as magnetic cores, and melamine (MEL) as the template molecule. MMINPs were assembled under an external magnetic field to construct photonic crystal (PC) sensor for naked-eye detection of MEL. The MMINPs were characterized by FT-IR, TEM, TGA, and VSM. The analytical performances of the magnetic molecularly imprinted PC sensor for MEL (MEL-MMIPCs) were investigated with respect to sensitivity, response time, selectivity, and stability. As the MEL concentration increases from 1.0 to 1.0 × 10⁶ μg/l, the reflection wavelength of MEL-MMIPCs shifted from 497 to 709 nm, and was linear with the logarithm of MEL concentration in this range. The detection limit was 0.21 μg/l (S/N = 3) and response time was within 30 s. The MEL-MMIPC sensor had an imprinting factor of 5.09, and selectivity factors for the analogs cyanuric acid and atrazine were 8.76 and 5.75, respectively, indicating the high sensitivity and selectivity. After 10 cycles of elution/response, MEL-MMIPCs still had a good ability to recognize MEL.

Ultrasensitive and highly selective "turn-on" fluorescent sensor for the detection and measurement of melatonin in juice samples

Melatonin (MLT), a hormone related to the regulation of brain functions, is directly related to sleep quality and is considered to be a possible adjuvant therapy for patients needing hospitalization for coronavirus disease 2019 pneumonia, and accurate measurement of MLT is crucial. Herein, a new, highly sensitive, and easy operation fluorescent probe was provided based on Zr metal-organic framework encapsulation into the molecularly imprinted polymer (MOF@MIP). By combining unique properties of MIP and fluorescent MOF, selectivity and operation of the applied method were significantly improved. Different characterization methods, such as XRD, FT-IR, and FE-SEM, were used to confirm the synthesis reliability. MOF@MIP was successfully used for the precise identification and ultrasensitive detection for trace amounts of MLT. The detection mechanism for the analytical system is based on the ''turn-on'' fluorescence (FL) signal in 404 nm. The findings proved that it is possible to detect trace amounts of MLT in real samples including grape, cherry, and sour cherry juice. The linear range and the limit of detection (LOD) for trace amounts of MLT were obtained as 1-100 ng/mL and 0.18 ng/mL, respectively.

Recyclable Magnetic Fluorescence Sensor Based on Fe3O4 and Carbon Dots for Detection and Purification of Methcathinone in Sewage

Sensitive, rapid, and low-cost detection of drug traces in sewage is very important for drug monitoring and control. In this study, a dual functional and recyclable magnetic fluorescent molecularly imprinted polymers (MFMIPs) sensor with high sensitivity for rapid detection and purification of methcathinone in sewage was developed. MFMIPs was prepared via molecular imprinting and conjugation with carbon dots as a fluorescent reporter on Fe₃O₄ (Fe₃O₄-MIPs@CDs). With strong recognition and adsorption toward methcathinone by the specific cavities on the surface of MFMIPs, the fluorescence of the sensor could dramatically be quenched once anchored with methcathinone. Under optimal conditions, the MFMIPs sensor presented high sensitivity with a linear range of 0.5-100 nM and a detection limit of 0.2 nM, which would be used to monitor drug prevalence and consumption within a certain region. This sensor was applied to the assay of methcathinone in sewage samples collected from Yuebeiyuan, Yanghu, and Xujiahu sewage pumping stations of Yuelu District. The calculated concentrations of methcathinone were 4.80, 15.33, and 8.59 nM in sewage samples, which were in good agreement with data tested by LC-MS/MS. For another function, MFMIPs exhibited purification toward methcathinone and the adsorption capacity was about 0.27 mg/g in a real sewage sample. Moreover, the sensor could be recycled and reused at least five times with the aid of an external magnetic field. Collectively, with good analytical performance and excellent recognition and selectivity to methcathinone, the proposed sensing system based on the magnetic core and molecularly imprinted polymers would open a door to establish highly sensitive and effective sensing systems for sewage analysis and purification.

A UCMPs@MIL-100 based thermo-sensitive molecularly imprinted fluorescence sensor for effective detection of β-lactoglobulin allergen in milk products

In this study, a thermo-sensitive molecularly imprinted fluorescence sensor was developed for the specific detection of β-Lactoglobulin (β-LG) allergen in milk products. The metal–organic frameworks (MIL-100) with a high specific surface area was coated on the surface of upconversion micro-particles (UCMPs). As the core, an imprinted polymer layer allowing for swelling and shrinking with response to temperature was prepared, which exhibited high adsorption and mass transfer capabilities for β-LG allergen. The fluorescence intensity of UCMPs@MIL-100@MIP decreased linearly with the concentration of β-LG in the range of 0.1–0.8 mg mL⁻¹, and the limit of detection was 0.043 mg mL⁻¹. The imprinting factor reached 3.415, which indicated that excellent specificity of the UCMPs@MIL-100@MIP for β-LG allergen. In the analysis of β-LG allergen in actual milk samples, the proposed UCMPs@MIL-100@MIP fluorescence sensor produced reliable and accurate results (recovery: 86.0–98.4%, RSD: 2.8–6.8%), closely related to the results of standard HPLC method (correlation coefficient: 0.9949), indicating that its feasibility in the detection of β-LG allergen.

BioMIPs: molecularly imprinted silk fibroin nanoparticles to recognize the iron regulating hormone hepcidin

The possibility to prepare molecularly imprinted nanoparticles from silk fibroin was recently demonstrated starting from methacrylated silk fibroin and choosing a protein as template. Here, we attempted the imprinting of fibroin-based molecularly imprinted polymers (MIPs), called bioMIPs, using as a template hepcidin that is a iron-metabolism regulator-peptide, possessing a hairpin structure. A homogeneous population (PDI < 0.2) of bioMIPs with size ~50 nm was produced. The bioMIPs were selective for the template; the estimated dissociation constant for hepcidin was KD = 3.6 ± 0.5 10-7 M and the average number of binding sites per bioMIP was equal to 2. The bioMIPs used in a competitive assay for hepcidin in serum showed a detection range of 1.01 10-7- 6.82 10-7 M and a limit of detection of 3.29 10-8 M.

Recent application of molecular imprinting technique in food safety

Due to the extensive use of chemical substances such as pesticides, antibiotics and food additives, food safety issues have gradually attracted people's attention. The extensive use of these chemicals seriously damages human health. In order to detect trace chemical residues in food, researchers have to find several simple, economical and effective tools for qualitative and quantitative analysis. As a kind of material that specifically and selectively recognize template molecules from real samples, molecular imprinting technique (MIT) has widely applied in food samples analysis. This article mainly reviews the application of molecularly imprinted polymer (MIP) in the detection of chemical residues from food in the past five years. Some recent and novel methods for fabrication of MIP are reviewed. Their application of sample pretreatment, sensors, etc. in food analysis is reviewed. The application of molecular imprinting in chromatographic stationary phase is referred. Additionally, the challenges faced by MIP are discussed.

Biomimetic Sensors to Detect Bioanalytes in Real-Life Samples Using Molecularly Imprinted Polymers: A Review

Molecularly imprinted polymers (MIPs) come with the promise to be highly versatile, useful artificial receptors for sensing a wide variety of analytes. Despite a very large body of literature on imprinting, the number of papers addressing real-life biological samples and analytes is somewhat limited. Furthermore, the topic of MIP-based sensor design is still, rather, in the research stage and lacks wide-spread commercialization. This review summarizes recent advances of MIP-based sensors targeting biological species. It covers systems that are potentially interesting in medical applications/diagnostics, in detecting illicit substances, environmental analysis, and in the quality control of food. The main emphasis is placed on work that demonstrates application in real-life matrices, including those that are diluted in a reasonable manner. Hence, it does not restrict itself to the transducer type, but focusses on both materials and analytical tasks.

Smartphone-based competitive immunoassay for quantitative on-site detection of meat adulteration

Rapid, sensitive, and portable analytical methods for on-site inspection of food fraud are now an urgent requirement to ensure food quality and satisfy the ethnic considerations of consumers. Hence, for the first time, a colorimetric smartphone-based immunoassay was developed for the on-site detection of pork adulteration in meat. In detail, the immunoassay was based on a competitive strategy in which immobilized standard porcine IgG competed with the target porcine IgG extracted in a single step from meat samples. The parameters involved in each step of the immunoassay conception and the digital colorimetric detection were carefully investigated and optimized. Using polystyrene microplates as ready-to-use stable and portable immunoplatforms, TMB as chromogenic substrate, smartphone as signal readout, and Image J software for image processing; the developed immunoassay was able to detect as low as 0.01% of pork in meat mixtures in a total assay time of 30 min. The selectivity of the immunoassay was evaluated for different meat species, and it was shown to selectively respond only to pork. Furthermore, excellent stability of the prepared immunological platform was demonstrated under extreme temperature conditions (50 °C), which confirms its high portability potential for in situ quantification of pork, while being relatively cost effective and non-laborious. The developed method also provides great precision (RSD < 6%) and accuracy (relative error< 6%). Given the universal use of smartphones as portable and affordable devices, such format of immunoassay could be a promising approach for rapid and sensitive real-time monitoring of food fraud.

Molecularly Imprinted Magnetic Fluorescent Nanocomposite-Based Sensor for Selective Detection of Lysozyme

A new strategy for the design and construction of molecularly imprinted magnetic fluorescent nanocomposite-based-sensor is proposed. This multifunctional nanocomposite exhibits the necessary optics, magnetism and biocompatibility for use in the selective fluorescence detection of lysozyme. The magnetic fluorescent nanocomposites are prepared by combining carboxyl- functionalized Fe3O4 magnetic nanoparticles with l-cysteine-modified zinc sulfide quantum dots (MNP/QDs). Surface molecular imprinting technology was employed to coat the lysozyme molecularly imprinted polymer (MIP) layer on the MNP/QDs to form a core-shell structure. The molecularly imprinted MNP/QDs (MNP/QD@MIPs) can rapidly separate the target protein and then use fluorescence sensing to detect the protein; this reduces the background interference, and the selectivity and sensitivity of the detection are improved. The molecularly imprinted MNP/QDs sensor presented good linearity over a lysozyme concentration range from 0.2 to 2.0 μM and a detection limit of 4.53 × 10-3 μM for lysozyme. The imprinting factor of the MNP/QD@MIPs was 4.12, and the selectivity coefficient ranged from 3.19 to 3.85. Furthermore, the MNP/QD@MIPs sensor was applied to detect of lysozyme in human urine and egg white samples with recoveries of 95.40-103.33%. Experimental results showed that the prepared MNP/QD@MIPs has potential for selective magnetic separation and fluorescence sensing of target proteins in biological samples.

“Out of Pocket” Protein Binding—A Dilemma of Epitope Imprinted Polymers Revealed for Human Hemoglobin

The epitope imprinting approach applies exposed peptides as templates to synthesize Molecularly Imprinted Polymers (MIPs) for the recognition of the parent protein. While generally the template protein binding to such MIPs is considered to occur via the epitope-shaped cavities, unspecific interactions of the analyte with non-imprinted polymer as well as the detection method used may add to the complexity and interpretation of the target rebinding. To get new insights on the effects governing the rebinding of analytes, we electrosynthesized two epitope-imprinted polymers using the N-terminal pentapeptide VHLTP-amide of human hemoglobin (HbA) as the template. MIPs were prepared either by single-step electrosynthesis of scopoletin/pentapeptide mixtures or electropolymerization was performed after chemisorption of the cysteine extended VHLTP peptide. Rebinding of the target peptide and the parent HbA protein to the MIP nanofilms was quantified by square wave voltammetry using a redox probe gating, surface enhanced infrared absorption spectroscopy, and atomic force microscopy. While binding of the pentapeptide shows large influence of the amino acid sequence, all three methods revealed strong non-specific binding of HbA to both polyscopoletin-based MIPs with even higher affinities than the target peptides.

Protein-imprinted polymer films prepared via cavity-selective multi-step post-imprinting modifications for highly selective protein recognition

The use of molecularly imprinted polymers (MIPs) for achieving synthetic receptors capable of selective molecular recognition is promising; however, these polymers exhibit low selectivity derived from the heterogeneity of their created, imprinted cavities. To achieve highly selective protein recognition, we herein report the cavity-selective, multi-step, post-imprinting modification of MIPs. An MIP film for lysozyme was prepared by the copolymerization of {[2-(2-methacrylamido)ethyldithio]ethylcarbamoyl}methoxy acetic acid, a functional monomer possessing a modifiable disulfide bond, with acrylamide and N,N'-methylenebisacrylamide in the presence of lysozyme. After the removal of lysozyme, the disulfide bonds were cleaved by treatment with a reductant. A low concentration of lysozyme was then added to occupy the high-affinity cavities of the polymer and sterically protect the thiol groups within them. A poly(ethylene glycol)-based capping agent was reacted with the thiol groups residing in low-affinity cavities to hinder them. After the regeneration of the high-affinity cavities by washing out the bound lysozyme, the remaining thiol groups were reacted with 3-(2-pyridyldithio)propionic acid to introduce interacting groups, which produced capped MIPs. Comparing the capped and uncapped MIPs revealed that off-target protein binding was effectively suppressed by the capping treatment without any reduction in binding affinity (1.1 × 10⁹ M^-1). Further investigation revealed that the lysozyme concentration during the capping process is critical for the selectivity of the capped MIP. In this case, highly selective MIPs were achieved when the lowest lysozyme concentration (100 nM) was used. This facile process for creating highly selective, synthetic polymer receptors is a powerful approach for achieving plastic antibodies.