Construction of Specific and Reversible Nanoreceptors for Proteins via Sequential Surface-Imprinting Strategy

Epitope-imprinted biomaterials with tailor-made molecular targeting for biomedical applications

Molecular imprinting technology (MIT), a synthetic strategy to create tailor-made molecular specificity, has recently achieved significant advancements. Epitope imprinting strategy, an improved MIT by imprinting the epitopes of biomolecules (e.g., proteins and nucleic acids), enables to target the entire molecule through recognizing partial epitopes exposed on it, greatly expanding the applicability and simplifying synthesis process of molecularly imprinted polymers (MIPs). Thus, epitope imprinting strategy offers promising solutions for the fabrication of smart biomaterials with molecular targeting and exhibits wide applications in various biomedical scenarios. This review explores the latest advances in epitope imprinting techniques, emphasizing selection of epitopes and functional monomers. We highlight the significant improvements in specificity, sensitivity, and stability of these materials, which have facilitated their use in bioanalysis, clinical therapy, and pharmaceutical development. Additionally, we discuss the application of epitope-imprinted materials in the recognition and detection of peptides, proteins, and cells. Despite these advancements, challenges such as template complexity, imprinting efficiency, and scalability remain. This review addresses these issues and proposes potential directions for future research to overcome these barriers, thereby enhancing the efficacy and practicality of epitope molecularly imprinting technology in biomedical fields.

Rational design based on multi-monomer simultaneous docking for epitope imprinting of SARS-CoV-2 spike protein

Among biomimetic strategies shaping engineering designs, molecularly imprinted polymer (MIP) technology stands out, involving chemically synthesised receptors emulating natural antigen-antibody interactions. These versatile 'designer polymers' with remarkable stability and low cost, are pivotal for in vitro diagnostics. Amid the recent global health crisis, we probed MIPs' potential to capture SARS-CoV-2 virions. Large biotemplates complicate MIP design, influencing generated binding site specificity. To precisely structure recognition sites within polymers, we innovated an epitope imprinting method supplemented by in silico polymerization component screening. A viral surface Spike protein informed epitope selection was targeted for MIP development. A novel multi-monomer docking approach (MMSD) was employed to simulate classical receptor-ligand interactions, mimicking binding reinforcement across multiple amino acids. Around 40 monomer combinations were docked to the epitope sequence and top performers experimentally validated via rapid fluorescence binding assays. Notably, high imprinting factor polymers correlated with MMSD predictions, promising rational MIP design applicable to diverse viral pathologies.

Fabrication of magnetic hydrophilic imprinted polymers via two-step immobilization approach for targeted detecting bisphenol A

Molecularly imprinted polymer with water-compatibility for effective separation and enrichment of targeted trace pollutants from complicated matrix has captured extensive attention in terms of their high selectivity and matrix compatibility. This study focuses on modified β-cyclodextrin is used as a hydrophilic functional monomer to develop magnetic molecularly imprinted polymers (MMIPs). MMIPs were prepared using Fe3O4 nanoparticles as carriers and bisphenol A (BPA) as templates using a two-step fixation strategy and surface imprinting technology. The structural characteristic and binding properties of the prepared MMIPs were thoroughly studied. The MMIPs exhibited high crystallinity, high adsorption capacity, fast rebinding rate, remarkable selectivity and distinguish reusability. In addition, through magnetic solid-phase extraction separation technology and high-performance liquid chromatography ultraviolet quantitative detection technology, MMIPs are used for selective enrichment and detection of BPA in complex media such as environmental water and milk. This work provides a new route to construct the hydrophilic molecularly imprinted materials and a new sight on developing more effective sample pretreatment strategies for monitoring targeted pollution in complicated aqueous media.

Recent Advances in Molecular Imprinting for Proteins on Magnetic Microspheres

The separation of proteins in biological samples plays an essential role in the development of disease detection, drug discovery, and biological analysis. Protein imprinted polymers (PIPs) serve as a tool to capture target proteins specifically and selectively from complex media for separation purposes. Whereas conventional molecularly imprinted polymer is time-consuming in terms of incubation studies and solvent removal, magnetic particles are introduced using their magnetic properties for sedimentation and separation, resulting in saving extraction and centrifugation steps. Magnetic protein imprinted polymers (MPIPs), which combine molecularly imprinting materials with magnetic properties, have emerged as a new area of research hotspot. This review provides an overview of MPIPs for proteins, including synthesis, preparation strategies, and applications. Moreover, it also looks forward to the future directions for research in this emerging field.

Surface imprinted-covalent organic frameworks for efficient solid-phase extraction of fluoroquinolones in food samples

Molecularly imprinting on covalent organic frameworks (MI-COF) is a promising way to prepare selective adsorbents for effective extraction of fluoroquinolones (FQs). However, the unstable framework structure and complex imprinting process are challenging for the construction of MI-COF. Here, we report a facile surface imprinting approach with dopamine to generate imprinted cavities on the surface of irreversible COF for highly efficient extraction of FQs in food samples. The irreversible-linked COF was fabricated from hexahydroxytriphenylene and tetrafluorophthalonitrile to ensure COF stability. Moreover, the introduction of dopamine surface imprinted polymer into COF provides abundant imprinted sites and endows excellent selectivity for FQs recognition against other antibiotics. Taking enrofloxacin as a template molecule, the prepared MI-COF gave an exceptional adsorption capacity of 581 mg g-1, a 2.2-fold enhancement of adsorption capacity compared with nonimprinted COF. The MI-COF was further explored as adsorbent to develop a novel solid-phase extraction method coupled with high-performance liquid chromatography for the simultaneous determination of enrofloxacin, norfloxacin and ciprofloxacin. The developed method gave the low limits of detection at 0.003-0.05 ng mL-1, high precision with relative standard deviations less than 3.5%. The recoveries of spiked FQs in food samples ranged from 80.4% to 110.7%.

Fabrication of superparamagnetic bovine haemoglobin surface-imprinted core-shell nanocomposite adsorbent via emulsion-free sol-gel polymerization

A new strategy has been developed to fabricate a bovine haemoglobin surface-imprinted core-shell nanocomposite adsorbent, demonstrating superparamagnetism via emulsion-free and sol-gel techniques. The obtained magnetic surface-imprinted polymers (MSIPs) possess a porous core-shell nanocomposite structure with a remarkable imprinted recognition ability for template protein in aqueous medium. The MSIPs display higher affinity, adsorption efficiency and selectivity, for template protein compared to the non-target protein. The morphology, adsorption, and recognition properties of the MSIPs have been evaluated by using several characterisation techniques, such as scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, and vibrating sample magnetometry. The results show the average diameter of MSIPs ranging between 400 and 600 nm with a saturation magnetization value of 52.6 emu/g and adsorption capacity of 43.75 mg/g_. And because the obtained MSIPs possessed easily accessible recognition sites and performed fast kinetics for template immobilization, it could achieve equilibrium within 60 min. All this revealed the potential application of this approach as an alternative methodology for the generation of protein imprinted biomaterials.

New Insights into High-Performance Nanocomposite Membranes with Threefold-Imprinted Layers for Selective Recognition and Separation

Herein, we reported on mixed-matrix membranes with polydopamine (PDA)-based threefold-imprinted layers (MMMs-PTIs), in which the dopamine molecules were simultaneously regarded as functional monomers and cross-linking agents during the first-in-class ternary-PDA-based imprinted method. Threefold-ibuprofen-imprinted layers were constructed into and onto the MMMs-PTIs through the phase inversion process, followed by suction filtration strategy, in which the PDA-based ibuprofen-imprinted activated carbon (AC)/SiO₂ and TiO₂/GO were chosen as fillers. Based on the threefold-imprinted SiO₂/AC and polymer and TiO₂/GO-loaded structure, rebinding capacities and permselectivity of MMMs-PTIs had been successfully enhanced, and the selective recognition and separation mechanism had been finally evaluated based on the static adsorption/permeation results. Both high rebinding capacity (53.22 mg/g) and adsorption selectivity (α > 2.0) had been achieved. Importantly, as to the permselectivity performance of MMMs-PTIs toward different compounds, the ibuprofen-permeation efficiencies (β value) of MMMs-PTIs reached 4.07, 4.08, and 3.77, respectively. That is to say, remarkable and stable permselectivity performance could be obtained, which demonstrated the successful preparation of good recognizability and permeability toward ibuprofen.

On-line monitoring of the dopamine-based molecular imprinting processes for protein templates with the assistance of a fluorescent indicator

On-line monitoring of the dopamine (DA)-based molecular imprinting processes over Fe₃O₄@SiO₂-NH₂ nanoparticles (SiMNPs) is reported by using a real-time quantitative PCR machine. Taking advantages of the efficient fluorescence quenching capability of polydopamine (PDA) and its high binding affinity to rhodamine B (RhB), we performed molecular imprinting against different proteins with free dopamine as the functional monomer and RhB as a fluorescent indicator. Along with the template molecules, the fluorescent indicators were continuously encapsulated into the PDA layer formed on the surface of the SiMNPs, resulting in immediate quenching of the fluorescence, which can be conveniently monitored in real time. As proteins showed sequence-dependent influences on the oxidation of dopamine and subsequent self-assembly on the surface of the SiMNPs, the observed fluorescence signals clearly indicated the polymerization progress in the presence of the template proteins, allowing precise control of the reaction time for different templates at a given initial concentration. The optimum end point of the reaction was found to be when 90 ± 3% of the templates had been encapsulated into the polymer, which offered the highest imprinting factor and selectivity. We applied the approach to prepare a primary PDA-based surface imprinted polymer for a multifunctional protein apurinic/apyrimidinic endonuclease/redox effector factor 1 (APE1). After further introduction of 3-hydroxyphenylboronic acid to the interfaces between APE1 and PDA, the resultant molecularly imprinted polymers (MIP-II) enabled quantitative isolation APE1 from cell lysate samples. The developed approach will be useful for the quantitative preparation of PDA-based MIPs for precious template proteins with limited input quantity. It is also applicable for further study on the effects of different proteins or peptides on the PDA formation reactions.

Novel composite nanomaterials based on magnetic molecularly imprinted polymers for selective extraction and determination of rutin in fruit juice

In this work, with the attempt to further improve the selectivity, magnetism and loading proportion of existing adsorbents, a novel composite (MGO/MHNTs@MIPs) was synthesized by electrostatically combining molecularly imprinted polymer based on the surface of magnetic halloysite nanotubes (MHNTs@MIPs) with magnetic graphene oxide (MGO). Then some characterizations were done to prove its successful synthesis. Besides, the bonding experiment showed that it possessed a loading capacity of up to 132 mg·g^-1, and the adsorption behavior of MGO/MHNTs@MIPs was elucidated by Langmuir isotherm model and Pseudo-second order model. By comparing its adsorption capacity to analogues, we concluded that the MGO/MHNTs@MIPs with the MHNTs@MIPs as basic elements exhibited higher selectivity (imprinting factor = 2.25) than that of MGO/MHNTs@NIPs based on MHNTs@NIPs for template rutin. Furthermore, a series of solid phase extraction conditions were optimized, and then the materials were used for the extraction and detection of rutin in fruit juice under the optimal conditions.

Polydopamine-based multilevel molecularly imprinted nanocomposite membranes comprising metal organic frameworks for selective recognition and separation

Molecularly imprinted nanocomposite membranes with three-dimensional metal-organic frameworks (MOFs)-based structure (MINMs-TM) were successfully prepared by using propranolol as template molecule. Importantly, for the first time, polycarbonate track etch membranes had been used as the supporting surfaces to construct the polydopamine (PDA)-induced MOFs composite structure, in which the as-prepared PDA-modified surface would promote the crystallization and nucleation of ZIF-8-based composite layer. Based on the entire preparation processes of our design, the as-prepared PDA-induced ZIF-8-modified surfaces could be regarded as the imprinted-initiated units of sol-gel imprinting polymerization. Abundant recognition sits of propranolol were achieved in MINMs-TM, which showed characteristic properties of permeability and selectivity. Therefore, high adsorption capacity (41.31 mg/g) and fast adsorption equilibrium rate (within 30 min) had been successfully achieved. Meanwhile, excellent permselectivity rates (β) of MINMs-TM toward propranolol were also obtained as 5.04, 4.79 and 5.14, which MINMs-TM the successful synthesis of high-affinity and high-density propranolol-imprinted sites. Overall, for the practical selective separation and scalability, we had successfully MINMs-TM the preparation of MINMs-TM-based to selective rebinding and separation of propranolol from complex solution system and mimetic water sample, which had further confirmed the desired and potential applications of many environmental pollutants.

Dual-imprinted organic/inorganic nanocomposite membranes with highly selective polydopamine-intimated nanostructures for pharmaceutically active compound separation

Here, the graphene oxide (GO)/SiO₂-loaded dual-imprinted membranes (GS-DIMs) were constructed based on the self-polymerization imprinting technique of dopamine, in which a twice polydopamine (PDA)-based imprinting strategy had been successfully developed to obtain the three-dimensional nanocomposite membrane-based separation system. Meanwhile, the pollution-intensive antibiotics of tetracycline (TC) was used as template molecule throughout the GS-DIMs synthesis, and the dopamine molecules were simultaneously used as functional monomer and cross-linking agent during the twice polydopamine (PDA)-based imprinting processes. Therefore, dual-TC-imprinted sites had been prepared based on the as-designed dual imprinting processes, the as-prepared GS-DIMs-based separation system with dual-TC-imprinted structures could not only allow for the largely enhanced rebinding result of 65.61 mg/g and faster adsorption equilibrium rate within 20 min, but also facilitate the permselectivity performance from TC-based complex separation system and mimetic water sample. Importantly, we demonstrated the applications and effects of the dual-imprinted membrane-based separation materials to selective rebinding and separation of TC from complex solution systems and mimetic water samples. The as-obtained permselectivity factors (β) around 4.0 strongly illustrated the efficiently selective separation ability and high-intensitive recognizability of TC than any other non-template molecules based on our GS-DIMs-based separation system. Overall, the as-designed GS-DIMs had great potential for selective separation applications and provided critical comparisons based on the as-achieved excellent rebinding and permselectivity performance, which encompassed innovative GO/SiO₂-loaded nanocomposite and PDA-based dual-TC-imprinted system.

Improved detection and recognition of glycoproteins using fluorescent polymers with a molecular imprint based on glycopeptides

Highly specific novel glycopeptide-based fluorescent molecularly imprinting polymers (g-FMIPs) were constructed to recognize and determine the target glycoprotein in complex biological samples. The glycopeptide of ovalbumin (OVA), with the unique structural characteristics of glycan and peptide, and potential application in improving the specificity recognition of g-FMIPs, was selected as the template molecule. The nitrogen-doped graphene quantum dots (N-GQDs) were introduced for fluorescence response. The obtained g-FMIPs possessed rapid binding kinetics and high adsorption capacity. Notably, the g-FMIPs exhibited remarkable selectivity and sensitivity with a high imprinting factor of 6.57, good linearity of 0.625 - 5.00 μM, and limit of detection of 0.208 μM. After treatment with g-FMIPs, the concentration of OVA in eluted solution was 1.07 μM. The obtained recoveries at 1.43 μM, 2.86 μM, and 4.29 μM spiked concentrations were 97.2%, 93.5%, and 101%, respectively, and the relative standard deviations were 2.6%, 4.2%, and 1.1%, respectively. In summary, the proposed strategy will expand the MIPs construction method and its application prospects in precision recognition and sensitive detection of trace glycoproteins from complex biosamples.

Dual-imprinted mixed matrix membranes for selective recognition and separation: A synergetic imprinting strategy based on complex initiation system

Molecularly imprinted membranes (MIMs) with sufficient and even-distributed recognition sites that can break the permeability-selectivity trade-off phenomenon are desirable in chemical field of selective separation. Herein graphene oxide (GO)/TiO₂-loaded nanocomposite fibrous membranes were prepared by developing two kinds of tetracycline (TC)-imprinted systems in the same MIMs-based material. Thereinto, polydopamine-based and sol-gel-based imprinting processes were applied to the synthesis of GO/TiO₂-loaded dual-imprinted mixed matrix membranes (GT-DIMs). The as-prepared GT-DIMs encompassed innovative GO/TiO₂-based nanocomposite fibrous channels and two kinds of TC-imprinted systems, and critical comparisons regarding the fluxes, rebinding capacities and permselectivity were provided and studied. Importantly, dual-imprinted system of GT-DIMs could not only allow for largely enhanced rebinding result (70.63 mg/g) and fast adsorption equilibrium rate within 30 min, but also facilitate the high permselectivity of TC in complex separation systems and lab-simulated wastewater samples. The permselectivity factors were all around 5.0, which strongly demonstrated the efficiently selective recognition and separation performance of GT-DIMs. Overall, based on testing results of practical separation and scalability, excellent structural stability and separation continuity had been successfully obtained for selective separation applications of pollutants.

Molecular Imprinting: Green Perspectives and Strategies

Advances in revolutionary technologies pose new challenges for human life; in response to them, global responsibility is pushing modern technologies toward greener pathways. Molecular imprinting technology (MIT) is a multidisciplinary mimic technology simulating the specific binding principle of enzymes to substrates or antigens to antibodies; along with its rapid progress and wide applications, MIT faces the challenge of complying with green sustainable development requirements. With the identification of environmental risks associated with unsustainable MIT, a new aspect of MIT, termed green MIT, has emerged and developed. However, so far, no clear definition has been provided to appraise green MIT. Herein, the implementation process of green chemistry in MIT is demonstrated and a mnemonic device in the form of an acronym, GREENIFICATION, is proposed to present the green MIT principles. The entire greenificated imprinting process is surveyed, including element choice, polymerization implementation, energy input, imprinting strategies, waste treatment, and recovery, as well as the impacts of these processes on operator health and the environment. Moreover, assistance of upgraded instrumentation in deploying greener goals is considered. Finally, future perspectives are presented to provide a more complete picture of the greenificated MIT road map and to pave the way for further development.

A sandwich sensor based on imprinted polymers and aptamers for highly specific double recognition of viruses

Highly selective and highly efficient identification of large viruses has been a major obstacle in the field of virus detection. In this work, a novel sandwich resonance light scattering sensor was designed based on molecularly imprinted polymers (MIPs) and aptamers for the first time. One of the recognition probes was obtained by molecular imprinting using environmentally friendly carbon spheres as carriers and the other by modification of the aptamer that can specifically recognize hepatitis B virus (HBV) on the surface of silicon spheres. In the presence of both probes, an MIP-HBV-aptamer sandwich structure was formed continuously in the system with the increase in HBV concentration, resulting in a strong resonance light scattering response. Finally, satisfactory selectivity and sensitivity were obtained, and the imprinting factor was as high as 7.56, which was higher than that reported in previous works of viral molecular imprinting sensor. In addition, it is of great significance to solve the problem of insufficient selectivity of traditional detection methods for macromolecular targets.

Selective recognition of a cyclic peptide hormone in human plasma by hydrazone bond-oriented surface imprinted nanoparticles

As a kind of artificial recognition material, molecularly imprinted polymers (MIPs) offer a promising perspective to be developed as synthetic chemical binders capable of selectively recognize biomacromolecules. However, owing to the large size and conformational flexibility of proteins and peptides, imprinting of these biomacromolecules remains a challenge. Novel imprinting strategies still need exploration for the improvement of recognition performance of MIPs. Herein, we developed a hydrazone bond-oriented surface imprinting strategy for an endogenous peptide hormone, human atrial natriuretic peptide (ANP). Surface-oriented imprinting of peptide via reversible covalent bond anchoring approach increased the orientation homogeneity of imprinted cavities as well as the utility of templates. The prepared nanoparticles exhibited high selectivity and fast recognition kinetics for ANP epitope. The dissociation constant between ANP epitope and MIP was measured as 5.3 μM. The applicability of the material in real samples was verified by the selective magnetic extraction of ANP from human plasma samples. This hydrazone bond-oriented surface imprinting strategy provides an alternative approach for the separation of peptides or proteins in complex bio-samples.