Recognition, neutralization, and clearance of target peptides in the bloodstream of living mice by molecularly imprinted polymer nanoparticles: a plastic antibody

Tailor-made molecular imprints for biological event intervention

Molecular imprints, which are crosslinked architectures containing specific molecular recognition cavities for targeting compounds, have recently transitioned from in vitro diagnosis to in vivo treatment. In current application scenarios, it has become an important topic to create new biomolecular recognition pathways through molecular imprinting, thereby inhibiting the pathogenesis and regulating the development of diseases. This review starts with a pathological analysis, mainly focusing on the corresponding artificial enzymes, enzyme inhibitors and antibody mimics with enhanced functions that are created by molecular imprinting strategies. Recent advances are highlighted in the use of molecular imprints as tailor-made nanomedicines for the prevention of three major diseases: metabolic syndrome, cancer, and bacterial/viral infections.

Bidirectional Regulation of Intracellular Enzyme Activity Using Light-Driven Nano-Inhibitors

Photochemical regulation provides precise control over enzyme activities with high spatiotemporal resolution. A promising approach involves anchoring "photoswitches" at enzyme active sites to modulate substrate recognition. However, current methods often require genetic mutations and irreversible enzyme modifications for the site-specific anchoring of "photoswitches", potentially compromising the enzyme activities. Herein, we present a pioneering reversible nano-inhibitor based on molecular imprinting technique for bidirectional regulation of intracellular enzyme activity. The nano-inhibitor employs a molecularly imprinted polymer nanoparticle as its body and azobenzene-modified inhibitors ("photoswitches") as the arms. By using a target enzyme as the molecular template, the nano-inhibitor acquires oriented binding sites on its surface, resulting in a high affinity for the target enzyme and non-covalently firm anchoring of the azobenzene-modified inhibitor to the enzyme active site. Harnessing the reversible isomerization of azobenzene units upon exposure to ultraviolet and visible light, the nano-inhibitor achieves bidirectional enzyme activity regulation by precisely docking and undocking inhibitor at the active site. Notably, this innovative approach enables the facile in situ regulation of intracellular endogenous enzymes, such as carbonic anhydrase. Our results represent a practical and versatile tool for precise enzyme activity regulation in complex intracellular environments.

Chiral acidic molecularly imprinted polymer for enantio-separation of norepinephrine racemate

We are looking into how well a copolymeric material made of poly (maleic acid-co-4-vinylpyridine) cross-linked with divinylbenzene can separate L-norepinephrine (L-NEP) from (±)-NEP. The initial step in this direction was the synthesis and subsequent analysis of L-NEP-maleimide chiral derivative. A 4-vinylpyridine/divinylbenzene combination was copolymerized with the resultant chiral maleimide. After heating the polymer materials in a high-alkaline environment to breakdown the connecting imide bonds, they were acidified in an HCl solution to eliminate the incorporated L-NEP species. Fourier transform infrared spectroscopy (FTIR) and a scanning electron microscope were used to examine the imprinted L-NEP-imprinted materials. The manufactured L-NEP-imprinted materials exhibited selectivity characteristics that were over 11 times greater for L-NEP than D-norepinephrine. The highest capacity observed in Langmuir adsorption studies was 170 mg/g at a pH of 7. After optical separation using a column technique, it was determined that the enantiomeric excess levels of D-norepinephrine and L-NEP in the first feeding and subsequent recovery solutions were 95% and 81%, respectively.

Control of polymer-protein interactions by tuning the composition and length of polymer chains

Nanomoduling the 3D shape and chemical functionalities in a synthetic polymer may create recognition cavities for biomacromolecule binding, which serves as an attractive alternative to natural antibodies with much less cost. To obtain fundamental understanding and predict molecular design rules of the polymer antibody, we analyze the complex structure between the biomarker protein epithelial cell adhesion molecule (EpCAM) and a series of polymer ligands via molecular dynamics (MD) simulations. For monomeric ligands, strong enrichment of aromatic residues in protein binding sites is revealed, in line with the reported observations for natural antibodies. Yet, for linear polymers with a growing degree of polymerization, for the first time, a drastic change is revealed on the type of enriched protein residues and the location of protein binding sites, driven by the increasing steric hindrance effect that makes the adsorption of the polymer in the protein exterior feasible. Varying the polymer length and monomeric composition also significantly affects the ligand binding affinity. Here, we have captured three distinct dependences of the ligand binding free energy on the degree of polymerization: for NIPAm based hydrophilic polymers, TBAm dominated hydrophobic polymers and AAc dominated charged polymers. These results can be rationalized by the complex structure and the composition of protein residues at the binding interface. The entire analysis demonstrates unique binding features for polymer ligands and the possibility to modulate their binding sites and affinity by engineering the polymer structure.

Construction of Highly Active and Selective Molecular Imprinting Catalyst for Hydrogenation

Surface molecular imprinting (MI) is one of the most efficient techniques to improve selectivity in a catalytic reaction. Heretofore, a prerequisite to fabricating selective catalysts by MI strategies is to sacrifice the number of surface-active sites, leading to a remarkable decrease of activity. Thus, it is highly desirable to design molecular imprinting catalysts (MICs) in which both the catalytic activity and selectivity are significantly enhanced. Herein, a series of MICs are prepared by sequentially adsorbing imprinting molecules (nitro compounds, N) and imprinting ligand (1,10-phenanthroline, L) over the copper surface of Cu/Al2O3. The resulting Cu/Al2O3-N-L MICs not only offer promoted catalytic selectivity but also enhance catalytic activity for nitro compounds hydrogenation by an creating imprinting cavity derived from the presorption of N and forming new active Cu-N sites at the interface of the copper sites and L. Characterizations by means of various experimental investigations and DFT calculations disclose that the molecular imprinting effect (promoted activity and selectivity) originates from the formation of new active Cu-N sites and precise imprinting cavities, endowing promoted catalytic selectivity and activity on the hydrogenation of nitro compounds.

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 Chalcone-Branched Polyimide-Based Chemosensors with Stripe Nanopatterns for the Detection of Melittin

In this study, a chalcone-branched polyimide (CB-PI) was synthesized by the Steglich esterification reaction for selective recognition of the toxic peptide melittin (MEL). MEL was immobilized on a nanopatterned poly(dimethylsiloxane) (PDMS) mold using a conventional surface modification technique to increase binding sites. A stripe-nanopatterned thin CB-PI film was formed on a quartz crystal (QC) substrate by simultaneously performing microcontact printing and ultraviolet (UV) light dimerization using a MEL-immobilized mold. The surface morphology changes and dimensions of the molecularly imprinted polymer (MIP) films with stripe nanopatterns (S-MIP) were analyzed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The sensing signals (Δf and Qe) of the S-MIP sensor were investigated upon adsorption in a 100-μL dilute plasma solution containing 30 μg/mL MEL, and its reproducibility, reuse, stability, and durability were investigated. The S-MIP sensor showed high sensitivity (5.49 mL/mg) and coefficient of determination (R2 = 0.999), and the detection limit (LOD) and the quantification limit (LOQ) were determined as 0.3 and 1.1 μg/mL, respectively. In addition, the selectivity coefficients (k*) calculated from the selectivity tests were 2.7-5.7, 2.1-4.3, and 2.8-4.6 for bovine serum albumin (BSA), immunoglobulin G (IgG), and apamin (APA), respectively. Our results indicate that the nanopatterned MIP sensors based on CB-PI demonstrate great potential as a sensing tool for the quantitative analysis of biomolecules.

Receptor-based detection of microplastics and nanoplastics: Current and future

Plastic pollution is an emerging environmental concern, gaining significant attention worldwide. They are classified into microplastics (MP; defined from 1 μm to 5 mm) and smaller nanoplastics (NP; <1 μm). NPs may pose higher ecological risks than MPs. Various microscopic and spectroscopic techniques have been used to detect MPs, and the same methods have occasionally been used for NPs. However, they are not based on receptors, which provide high specificity in most biosensing applications. Receptor-based micro/nanoplastics (MNP) detection can provide high specificity, distinguishing MNPs from the environmental samples and, more importantly, identifying the plastic types. It can also offer a low limit of detection (LOD) required for environmental screening. Such receptors are expected to detect NPs specifically at the molecular level. This review categorizes the receptors into cells, proteins, peptides, fluorescent dyes, polymers, and micro/nanostructures. Detection techniques used with these receptors are also summarized and categorized. There is plenty of room for future research to test for broader classes of environmental samples and many plastic types, to lower the LOD, and to apply the current techniques for NPs. Portable and handheld MNP detection should also be demonstrated for field use since the current demonstrations primarily utilized laboratory instruments. Detection on microfluidic platforms will also be crucial in miniaturizing and automating the assay and, eventually, collecting an extensive database to support machine learning-based classification of MNP types.

Molecularly Imprinted Nanoparticle Ensembles for Rapidly Identifying S. epidermidis

Staphylococcus epidermidis (S. epidermidis) belongs to methicillin-resistant bacteria strains that cause severe disease in humans. Herein, molecularly imprinted polymer (MIP) nanoparticles resulting from solid-phase synthesis on entire cells were employed as a sensing material to identify the species. MIP nanoparticles revealed spherical shapes with diameters of approximately 70 nm to 200 nm in scanning electron microscopy (SEM), which atomic force microscopy (AFM) confirmed. The interaction between nanoparticles and bacteria was assessed using height image analysis in AFM. Selective binding between MIP nanoparticles and S. epidermidis leads to uneven surfaces on bacteria. The surface roughness of S. epidermidis cells was increased to approximately 6.3 ± 1.2 nm after binding to MIP nanoparticles from around 1 nm in the case of native cells. This binding behavior is selective: when exposing Escherichia coli and Bacillus subtilis to the same MIP nanoparticle solutions, one cannot observe binding. Fluorescence microscopy confirms both sensitivity and selectivity. Hence, the developed MIP nanoparticles are a promising approach to identify (pathogenic) bacteria species.

Emerging nanoparticle designs against bacterial infections

The rise of antibiotic resistance has caused the prevention and treatment of bacterial infections to be less effective. Therefore, researchers turn to nanomedicine for novel and effective antibacterial therapeutics. The effort resulted in the first-generation antibacterial nanoparticles featuring the ability to improve drug tolerability, circulation half-life, and efficacy. Toward developing the next-generation antibacterial nanoparticles, researchers have integrated design elements that emphasize physical, broad-spectrum, biomimetic, and antivirulence mechanisms. This review highlights four emerging antibacterial nanoparticle designs: inorganic antibacterial nanoparticles, responsive antibacterial nanocarriers, virulence nanoscavengers, and antivirulence nanovaccines. Examples in each design category are selected and reviewed, and their structure-function relationships are discussed. These emerging designs open the door to nontraditional antibacterial nanomedicines that rely on mechano-bactericidal, function-driven, nature-inspired, or virulence-targeting mechanisms to overcome antibiotic resistance for more effective antibacterial therapy. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease.

Fluorescent Molecularly Imprinted Polymers Loaded with Avenanthramides for Inhibition of Advanced Glycation End Products

Encapsulating bioactive avenanthramides (AVAs) in carriers to respond to the environmental changes of food thermal processing allows the controlled release of AVAs for the effective inhibition of biohazards. In this study, fluorescent molecular imprinted polymers (FMIPs) loaded with AVAs were prepared by reverse microemulsion. The fluorescent signal was generated by carbon dots (CDs), which were derived from oat bran to determine the load of AVAs. The FMIPs were uniformly spherical in appearance and demonstrated favorable properties, such as thermal stability, protection of AVAs against photodegradation, high encapsulation efficiency, and effective scavenging of free radicals. After consideration of the different kinetics models, the release of AVAs from the FMIPs matched the Weibull model and followed a Fickian diffusion mechanism. The FMIPs exhibited good inhibition of pyrraline in a simulated casein-ribose system and in milk samples, indicating the release of AVAs could inhibit the generation of pyrraline.

In Vivo Electrochemical Biosensors: Recent Advances in Molecular Design, Electrode Materials, and Electrochemical Devices

Electrochemical biosensors provide powerful tools for dissecting the dynamically changing neurochemical signals in the living brain, which contribute to the insight into the physiological and pathological processes of the brain, due to their high spatial and temporal resolutions. Recent advances in the integration of in vivo electrochemical sensors with cross-disciplinary advances have reinvigorated the development of in vivo sensors with even better performance. In this Review, we summarize the recent advances in molecular design, electrode materials, and electrochemical devices for in vivo electrochemical sensors from molecular to macroscopic dimensions, highlighting the methods to obtain high performance for fulfilling the requirements for determination in the complex brain through flexible and smart design of molecules, materials, and devices. Also, we look forward to the development of next-generation in vivo electrochemical biosensors.

Rational Development of Hypervalent Glycan Shield-Binding Nanoparticles with Broad-Spectrum Inhibition against Fatal Viruses Including SARS-CoV-2 Variants

Infectious virus diseases, particularly coronavirus disease 2019, have posed a severe threat to public health, whereas the developed therapeutic and prophylactic strategies are seriously challenged by viral evolution and mutation. Therefore, broad-spectrum inhibitors of viruses are highly demanded. Herein, an unprecedented antiviral strategy is reported, targeting the viral glycan shields with hypervalent mannose-binding nanoparticles. The nanoparticles exhibit a unique double-punch mechanism, being capable of not only blocking the virus-receptor interaction but also inducing viral aggregation, thereby allowing for inhibiting the virus entry and facilitating the phagocytosis of viruses. The nanoparticles exhibit potent and broad-spectrum antiviral efficacy to multiple pseudoviruses, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its major variants (D614G, N501Y, N439K, Δ69-70, Delta, and Omicron; lentiviruses expressing only the spike proteins), as well as other vital viruses (human immunodeficiency virus 1 and Lassa virus), with apparent EC50 values around the 10^-9  m level. Significantly, the broad-spectrum inhibition of authentic viruses of both wild-type SARS-CoV-2 and Delta variants is confirmed. Therefore, this hypervalent glycan-shield targeting strategy opens new access to broad-spectrum viral inhibition.

Snapshot imprinting as a tool for surface mapping and identification of novel biomarkers of senescent cells

Cellular senescence has proved to be a strong contributor to ageing and age-related diseases, such as cancer and atherosclerosis. Therefore, the protein content of senescent cells is highly relevant to drug discovery, diagnostics and therapeutic applications. However, current technologies for the analysis of proteins are based on a combination of separation techniques and mass spectrometry, which require handling large sample sizes and a large volume of data and are time-consuming. This limits their application in personalised medicine. An easy, quick and inexpensive procedure is needed for qualitative and quantitative analysis of proteins expressed by a cell or tissue. Here, we describe the use of the "snapshot imprinting" approach for the identification of proteins differentially expressed by senescent cells. Molecularly imprinted polymer nanoparticles (MIPs) were formed in the presence of whole cells. Following trypsinolysis, protein epitopes protected by complex with MIPs were eluted from the nanoparticles and analysed by LC-MS/MS. In this work, "snapshot imprinting" was performed parallel to a standard proteomic "shaving approach", showing similar results. The analysis by "snapshot imprinting" identified three senescent-specific proteins: cell division cycle 7-related protein kinase, partitioning defective three homolog B and putative ATP-dependent RNA helicase DHX57, the abundance of which could potentially make them specific markers of senescence. Identifying biomarkers for the future elimination of senescent cells grants the potential for developing therapeutics for age-related diseases.

In Vivo Applications of Molecularly Imprinted Polymers for Drug Delivery: A Pharmaceutical Perspective

Molecularly imprinted polymers (MIPs) have been proven to be a promising candidate for drug delivery systems (DDS) due to their ability to provide a sustained and controlled drug release, making them useful for treating a wide range of medical conditions. MIP-based DDS offer many advantages, including the administration of a smaller drug doses, due to the higher drug payload or targeted delivery, resulting in fewer side effects, as well as the possibility of attaining high concentrations of the drug in the targeted tissues. Whether designed as drug reservoirs or targeted DDS, MIPs are of great value to drug delivery as conventional drug formulations can be redesigned as DDS to overcome the active pharmaceutical ingredient's (APIs) poor bioavailability, toxic effects, or other shortcomings that previously made them less efficient or unsuitable for therapy. Therefore, MIP design could be a promising alternative to the challenging research and development of new lead compounds. Research on MIPs is primarily conducted from a material science perspective, which often overlooks some of their key pharmaceutical requirements. In this review, we emphasize the specific features that make MIPs suitable for clinical use, from both a material science and a biopharmaceutical perspective.

Molecularly imprinted nanoparticles with recognition properties towards diphtheria toxin for ELISA applications

Plastic antibodies can be used for in vitro neutralization of biomacromolecules with different fragments due to their potential in separation, purification, chemical sensor, catalysis and drug production studies. These polymer nanoparticles with binding affinity and selectivity comparable to natural antibodies were prepared using functional monomer synthesis and copolymerization of acrylic monomers via miniemulsion polymerization. As a result, the in vitro cytotoxic effect from diphtheria toxin was reduced by MIPs. In vitro imaging experiments of polymer nanoparticles (plastic antibodies) were performed to examine the interaction of diphtheria toxin with actin filaments, and MIPs inhibited diphtheria toxin damage on actin filaments. The enzyme-linked immunosorbent assay (ELISA) was performed with plastic antibodies labeled with biotin, and it was determined that plastic antibodies could also be used for diagnostic purposes. We report that molecularly imprinted polymers (MIPs), which are biocompatible polymer nanoparticles, can capture and reduce the effect of diphtheria toxic and its fragment A.

Molecularly Imprinted Ligand-Free Nanogels for Recognizing Bee Venom-Originated Phospholipase A2 Enzyme

In this study, ligand-free nanogels (LFNGs) as potential antivenom mimics were developed with the aim of preventing hypersensitivity and other side effects following massive bee attacks. For this purpose, poly (ethylene glycol) diacrylate was chosen as a main synthetic biocompatible matrix to prepare the experimental LFNGs. The overall concept uses inverse mini-emulsion polymerization as the main route to deliver nanogel caps with complementary cavities for phospholipase A2 (PLA2) from bee venom, created artificially with the use of molecular imprinting (MI) technologies. The morphology and the hydrodynamic features of the nanogels were confirmed by transmission electron microscopy (TEM) and dynamic light scattering (DLS) analysis. The following rebinding experiments evidenced the specificity of molecularly imprinted LFNG for PLA2, with rebinding capacities up to 8-fold higher compared to the reference non-imprinted nanogel, while the in vitro binding assays of PLA2 from commercial bee venom indicated that such synthetic nanogels are able to recognize and retain the targeted PLA2 enzyme. The results were finally collaborated with in vitro cell-viability experiments and resulted in a strong belief that such LFNG may actually be used for future therapies against bee envenomation.

Inhibition of Melittin Activity Using a Small Molecule with an Indole Ring

We investigated d-amino acids as potential inhibitors targeting l-peptide toxins. Among the l- and d-amino acids tested, we found that d-tryptophan (d-Trp) acted as an inhibitor of melittin-induced hemolysis. We then evaluated various Trp derivatives and found that 5-chlorotryptamine (5CT) had the largest inhibitory effect on melittin. The indole ring, amino group, and steric hindrance of an inhibitor played important roles in the inhibition of melittin activity. Despite the small size and simple molecular structure of 5CT, its IC₅₀ was approximately 13 μg/mL. Fluorescence quenching, circular dichroism measurements, and size-exclusion chromatography revealed that 5CT interacted with Trp19 in melittin and affected the formation of the melittin tetramer involved in hemolysis. Molecular dynamics simulation of melittin also indicated that the interaction of 5CT with Trp19 in melittin affected the formation of the tetramer.

How Molecularly Imprinted Polymers can be Used for Diagnostic and Treatment of Tropical Diseases?

Molecularly imprinted polymers (MIPs) have been widely used in nanomedicine in the last few years. However, their use for diagnostic and treatment of tropical diseases is limited. Through this review, we aim to illustrate how MIPs were used to detect tropical disease and we show that they are not exploited enough in treatment. We finally show how MIPs could be used in the future in the treatment of tropical disease.

Rationally Screened and Designed ABCG2-Binding Aptamers for Targeting Cancer Stem Cells and Reversing Multidrug Resistance

The ATP-binding cassette, subfamily G, isoform 2 protein (ABCG2), as an important member of ABC transporters, plays a key role in multidrug resistance (MDR) in cancer and has been widely considered as a marker of cancer stem cells (CSC). Reagents capable of simultaneously targeting ABCG2 and reversing MDR have great clinical application values, but their development is highly challenging. Herein, ABCG2 glycosylated extracellular region-binding aptamers were efficiently screened by a cladded molecularly imprinted polymer (cMIP)-based in vitro screening method and further rationally engineered into cyclic bivalent aptamers. Experiments showed that both the monovalent and cyclic bivalent aptamers could specifically bind ABCG2 and thereby specially target CSC of human colorectal carcinomas (CoCSC), while the latter could effectively reverse MDR in drug-resistant liver cancer cells (HepG2/ADR). Different from currently predominant small molecule inhibitors, the reversal of MDR relied on a different mechanism; the cyclic bivalent aptamers bound the two monomers of ABCG2 dimers simultaneously and thereby blocked the ABCG2-mediated drug-pumping channel, resulting in increased intracellular accumulation of substrate drugs. This study opened a new access to the development of affinity reagents for targeting CSC and reversing MDR, holding great prospects in cancer diagnosis and treatment.

Molecularly Imprinted Polymers with Enzymatic Properties Reduce Cytokine Release Syndrome

A core-shell molecularly imprinted polymer nanoparticle with biological enzyme functional characteristics was developed by oxidative polymerization of template protein and polydopamine on the surface of protease-copper phosphate hybrid nanoflowers by molecular imprinting technology and enzyme immobilization technology. The obtained molecularly imprinted polymer showed specific binding characteristics with the template protein. It recognized and enriched the target molecules through the surface molecularly imprinted sites of the shell structure. In addition, the bound target molecules were further degraded into fragments by nanozymes with biological enzyme characteristics in the core. In this study, molecular imprinting technology and biotechnology were combined to obtain bifunctional molecularly imprinted polymer nanoparticles that can not only enrich template molecules but also degrade them into fragments. Herein, we selected interleukin 6 (IL-6), the target molecule of cytokine release syndrome (CRS), as a template molecule, and reported a molecularly imprinted polymer with degrading enzyme properties that can rapidly reduce IL-6 levels in vivo, including a molecularly imprinted layer that can recognize and bind IL-6 and nanozymes that can degrade IL-6 and deactivate it. It is used to clear the excessive secretion of IL-6 in CRS and reduce the level of IL-6 in the body to achieve the purpose of adjuvant treatment of CRS.

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.

Molecular imprinting and cladding produces antibody mimics with significantly improved affinity and specificity

Molecularly imprinted polymers (MIPs), as important mimics of antibodies, are chemically synthesized by polymerization in the presence of a target compound. MIPs have found wide applications in important fileds. However, the current molecular imprinting technology suffers from a dilemma; there is often a compromise between the best affinity and the best specificity for MIPs prepared under optimized conditions. Herein, we proposed a new strategy called molecular imprinting and cladding (MIC) to solve this issue. The principle is straightforward; after molecular imprinting, a chemically inert cladding thinlayer is generated to precisely cover non-imprinted area. We further proposed a special MIC approach for controllably engineering protein binders. The prepared cladded MIPs (cMIPs) exhibited significantly improved affinity and specificity. The general applicability of the proposed strategy and method was verified by engineering of cMIPs for the recognition of a variety of different proteins. The feasibility of cMIPs for real applications was demonstrated by fluorescence imaging of cancer cells against normal cells and immunoassay of C-peptide in human urine. This study opened up a new avenue for controllably engineering protein-specific antibody mimics with excellent recognition properties, holding great prospective in important applications such as disease diagnosis and nanomedicine.

The Evolution of Molecular Recognition: From Antibodies to Molecularly Imprinted Polymers (MIPs) as Artificial Counterpart

Molecular recognition is a useful property shared by various molecules, such as antibodies, aptamers and molecularly imprinted polymers (MIPs). It allows these molecules to be potentially involved in many applications including biological and pharmaceutical research, diagnostics, theranostics, therapy and drug delivery. Antibodies, naturally produced by plasma cells, have been exploited for this purpose, but they present noticeable drawbacks, above all production cost and time. Therefore, several research studies for similar applications have been carried out about MIPs and the main studies are reported in this review. MIPs, indeed, are more versatile and cost-effective than conventional antibodies, but the lack of toxicity studies and their scarce use for practical applications, make it that further investigations on this kind of molecules need to be conducted.

Rational development of molecularly imprinted nanoparticles for blocking PD-1/PD-L1 axis

Blocking the PD-1/PD-L1 immune checkpoint has emerged as a promising strategy in cancer immunotherapy, in which monoclonal antibodies are predominately used as inhibitors. Despite their remarkable success, monoclonal antibody-based therapeutics suffer from drawbacks due to the use of antibodies, such as high cost, low stability and high frequency of immune-related adverse effects. Therefore, novel anti-PD-1/PD-L1 therapeutics that can address these issues are of significant importance. Herein, we report a molecularly imprinted polymer (MIP) based PD-1 nano inhibitor for blocking the PD-1/PD-L1 axis. The anti-PD-1 nanoMIP was rationally designed and engineered by epitope imprinting using the N-terminal epitope of PD-1 as the binding site. The anti-PD-1 nanoMIP showed good specificity and high affinity towards PD-1, yielding a disassociation constant at the 10⁻⁸ M level, much better than that between PD-1 and PD-L1. Via steric hindrance, this inhibitor could effectively block PD-1/PD-L1 interaction. Besides, it could effectively reactivate T cells and reverse the chemoresistance of tumor cells. Therefore, this present study not only provides a novel and promising immune checkpoint blockade inhibitor but also boosts further development of MIPs for cancer immunotherapy.

A nanoscale molecularly imprinted polymer (MIP) for blocking the PD-1/PD-L1 axis was rationally developed. The anti-PD-1 nanoMIP was able to effectively block PD-1/PD-L1 interaction, reactivate T cells and reverse the chemoresistance of tumor cells.

Modulation of Acetylcholinesterase Activity Using Molecularly Imprinted Polymer Nanoparticles

Modulation of enzyme activity allows for control over many biological pathways and while strategies for the pharmaceutical design of inhibitors are well established; methods for promoting activation, that is an...

Mass spectrometric detection of KRAS protein mutations using molecular imprinting

Cancer is a disease of cellular evolution where single base changes in the genetic code can have significant impact on the translation of proteins and their activity. Thus, in cancer research there is significant interest in methods that can determine mutations and identify the significant binding sites (epitopes) of antibodies to proteins in order to develop novel therapies. Nano molecularly imprinted polymers (nanoMIPs) provide an alternative to antibodies as reagents capable of specifically capturing target molecules depending on their structure. In this study, we used nanoMIPs to capture KRAS, a critical oncogene, to identify mutations which when present are indicative of oncological progress. Herein, coupling nanoMIPs (capture) and liquid chromatography-mass spectrometry (detection), LC-MS has allowed us to investigate mutational assignment and epitope discovery. Specifically, we have shown epitope discovery by generating nanoMIPs to a recombinant KRAS protein and identifying three regions of the protein which have been previously assigned as epitopes using much more time-consuming protocols. The mutation status of the released tryptic peptide was identified by LC-MS following capture of the conserved region of KRAS using nanoMIPS, which were tryptically digested, thus releasing the sequence of a non-conserved (mutated) region. This approach was tested in cell lines where we showed the effective genotyping of a KRAS cell line and in the plasma of cancer patients, thus demonstrating its ability to diagnose precisely the mutational status of a patient. This work provides a clear line-of-sight for the use of nanoMIPs to its translation from research into diagnostic and clinical utility.

Molecularly Imprinted Polymer Hydrogel Nanoparticles: Synthetic Antibodies for Cancer Diagnosis and Therapy

Cancer is a leading cause of death worldwide and according to the World Health Organization (WHO) accounted for 10 million deaths in 2020. Promising theranostic (therapy and diagnostic) agents in the treatment of cancer are nanomaterials, which have come to the forefront because of their small size approaching those of protein complexes in the human body, and of their easy functionalization giving access to nanocomposite materials with diverse functions (fluorescence, magnetic, stimuli-responsiveness, etc.), and improved biocompatibility. Among them, affinity nanoparticles, often decorated with highly specific targeting ligands such as antibodies, aptamers, lectins and peptides, have enabled enhanced binding and exquisite recognition of biomarkers overexpressed in cancer cells. In this review, we describe an emerging class of targeting ligands, molecularly imprinted polymer hydrogel nanoparticles for their application in the early detection of disease, with the aim to improve diagnosis and treatment.

Advanced bioactive nanomaterials for biomedical applications

Bioactive materials are a kind of materials with unique bioactivities, which can change the cellular behaviors and elicit biological responses from living tissues. Bioactive materials came into the spotlight in the late 1960s when the researchers found that the materials such as bioglass could react with surrounding bone tissue for bone regeneration. In the following decades, advances in nanotechnology brought the new development opportunities to bioactive nanomaterials. Bioactive nanomaterials are not a simple miniaturization of macroscopic materials. They exhibit unique bioactivities due to their nanoscale size effect, high specific surface area, and precise nanostructure, which can significantly influence the interactions with biological systems. Nowadays, bioactive nanomaterials have represented an important and exciting area of research. Current and future applications ensure that bioactive nanomaterials have a high academic and clinical importance. This review summaries the recent advances in the field of bioactive nanomaterials, and evaluate the influence factors of bioactivities. Then, a range of bioactive nanomaterials and their potential biomedical applications are discussed. Furthermore, the limitations, challenges, and future opportunities of bioactive nanomaterials are also discussed.

Fighting Antibiotic-Resistant Bacteria : Promising Strategies Orchestrated by Molecularly Imprinted Polymers

Infections caused by antibiotic-resistant bacteria are difficult and sometimes impossible to treat, making them one of the major public health problems of our time. We highlight how one unique material , molecularly imprinted polymers (MIPs), can orchestrate several strategies to fight this major societal issue. MIPs are tailor-made biomimetic supramolecular receptors that recognize and bind target molecules with a high affinity and selectivity, comparable to those of antibodies. While research on MIPs for combatting cancer has been constantly flourishing, comprehensive work on their involvement in combatting resistant superbugs has been rather scarce. This review aims at filling this gap. We will describe what are the causes of bacterial resistance and at which level MIPs can deploy their weapons. MIPs' targets can be biofilm constituents, quorum sensing messengers, bacterial surface proteins and antibiotic-deactivating enzymes, among others. We will conclude on the current challenges and future developments in this field.

Epitope-imprinted polymers: Design principles of synthetic binding partners for natural biomacromolecules

Molecular imprinting (MI) has been explored as an increasingly viable tool for molecular recognition in various fields. However, imprinting of biologically relevant molecules like proteins is severely hampered by several problems. Inspired by natural antibodies, the use of epitopes as imprinting templates has been explored to circumvent those limitations, offering lower costs and greater versatility. Here, we review the latest innovations in this technology, as well as different applications where MI polymers (MIPs) have been used to target biomolecules of interest. We discuss the several steps in MI, from the choice of epitope and functional monomers to the different production methods and possible applications. We also critically explore how MIP performance can be assessed by various parameters. Last, we present perspectives on future breakthroughs and advances, offering insights into how MI techniques can be expanded to new fields such as tissue engineering.

The promising use of nano-molecular imprinted templates for improved SARS-CoV-2 detection, drug delivery and research

Molecular imprinting (MI) is a technique that creates a template of a molecule for improving complementary binding sites in terms of size and shape to a peptide, protein, bacteria, mammalian cell, or virus on soft materials (such as polymers, hydrogels, or self-assembled materials). MI has been widely investigated for over 90 years in various industries but is now focused on improved tissue engineering, regenerative medicine, drug delivery, sensors, diagnostics, therapeutics and other medical applications. Molecular targets that have been studied so far in MI include those for the major antigenic determinants of microorganisms (like bacteria or viruses) leading to innovations in disease diagnosis via solid-phase extraction separation and biomimetic sensors. As such, although not widely investigated yet, MI demonstrates much promise for improving the detection of and treatment for the current Coronavirus Disease of 2019 (COVID-2019) pandemic as well as future pandemics. In this manner, this review will introduce the numerous applications of MI polymers, particularly using proteins and peptides, and how these MI polymers can be used as improved diagnostic and therapeutic tools for COVID-19.

A Supramolecular Antidote to Macromolecular Toxins Prepared through Coassembly of Macrocyclic Amphiphiles

Poisoning is a leading cause of admission to medical emergency departments and intensive care units. Supramolecular detoxification, which involves injecting supramolecular receptors that bind with toxins to suppress their biological activity, is an emerging strategy for poisoning treatment; it has few requirements and a broad application scope. However, it is still a formidable challenge to design supramolecular therapeutic materials as an antidote to macromolecular toxins, because the large size, flexible conformation, and presence of multiple and diverse binding sites of biomacromolecules hinder their recognition. Herein, a supramolecular antidote to macromolecular toxins is developed through the coassembly of macrocyclic amphiphiles, relying on heteromultivalent recognition between the coassembled components and toxic macromolecules. The coassembly of amphiphilic cyclodextrin and calixarene strongly and selectively captures melittin, a toxin studied herein; this imparts various therapeutic effects such as inhibiting the interactions of melittin with cell membranes, alleviating melittin cytotoxicity and hemolytic toxicity, reducing the mortality rate of melittin-poisoned mice, and mitigating damage to major organs. The use of the proposed antidote overcomes the limitation of supramolecular detoxification applicability to only small-molecular toxins. The antidote can also detoxify other macromolecular toxins as long as selective and strong binding is achieved because of the coassembling tunability.

Substrate Protection in Controlled Enzymatic Transformation of Peptides and Proteins

Proteins are involved in practically every single biological process. The many enzymes involved in their synthesis, cleavage, and posttranslational modification (PTM) carry out highly specific tasks with no usage of protecting groups. Yet, the chemists' strategy of protection/deprotection potentially can be highly useful, for example, when a specific biochemical reaction catalyzed by a broad-specificity enzyme needs to be inhibited, during infection of cells by enveloped viruses, in the invasion and spread of cancer cells, and upon mechanistic investigation of signal-transduction pathways. Doing so requires highly specific binding of peptide substrates in aqueous solution with biologically competitive affinities. Recent development of peptide-imprinted cross-linked micelles allows such protection and affords previously impossible ways of manipulating peptides and proteins in enzymatic transformations.

Targeted Mitochondrial Fluorescence Imaging-Guided Tumor Antimetabolic Therapy with the Imprinted Polymer Nanomedicine Capable of Specifically Recognizing Dihydrofolate Reductase

As we all know, inhibiting the activity of dihydrofolate reductase (DHFR) has always been an effective strategy for folate antimetabolites to treat tumors. In the past, it mainly relied on chemical drugs. Here, we propose a new strategy, (3-propanecarboxyl)triphenylphosphonium bromide (CTPB)-modified molecularly imprinted polymer nanomedicine (MIP-CTPB). MIP-CTPB prepared by imprinting the active center of DHFR can specifically bind to the active center to block the catalytic activity of DHFR, thereby inhibiting the synthesis of DNA and ultimately inhibiting the tumor growth. The modification of CTPB allows the nanomedicine to be targeted and enriched in mitochondria, where DHFR is abundant. The confocal laser imaging results show that MIP-CTPB can target mitochondria. Cytotoxicity experiments show that MIP-CTPB inhibits HeLa cell proliferation by 42.2%. In vivo experiments show that the tumor volume of the MIP-CTPB-treated group is only one-sixth of that of the untreated group. The fluorescent and paramagnetic properties of the nanomedicine enable targeted fluorescence imaging of mitochondria and T2-weighted magnetic resonance imaging of tumors. This research not only opens up a new direction for the application of molecular imprinting, but also provides a new idea for tumor antimetabolic therapy guided by targeted mitochondrial imaging.

Synthesis, characterization, and evaluation of selective molecularly imprinted polymers for the fast determination of synthetic cathinones

As a kind of new psychoactive substance (NPS), synthetic cathinones have drawn great worldwide attention. In this study, molecularly imprinted polymers (MIPs), as adsorbents for the extraction and determination of 4-methyldimethcathinone (4-MDMC), were first synthesized by coprecipitation polymerization. The physicochemical analyses of MIPs were successfully performed by XRD, FTIR, FESEM and TGA techniques. Furthermore, rebinding properties of temperature and pH dependence, and selectivity and reusability tests for MIPs and non-imprinted polymers (NIPs) were performed using an ultraviolet-visible spectrometer (UV-vis). The obtained results indicate that the imprinting efficiency has strong dependence on temperature and pH, and the optimal adsorption for targets is achieved under the condition of 318 K and pH = 6.0. This means that the combination between the polymers and 4-MDMC is a strong spontaneous and endothermic process. Compared with NIPs, MIPs exhibit prominent adsorption capacity (Q_e = 9.77 mg g⁻¹, 318 K). The selectivity coefficients (k) of MIPs for 4-MDMC, methylenedioxypentedrone (βk-MBDP), 4-ethylmethcathinone (4-EMC), methoxetamine (MXE) and tetrahydrofuranylfentanyl (THF-F) were found to be 1.70, 3.49, 7.14 and 5.82, respectively. Moreover, it was found that the adsorption equilibrium was achieved within 30 min. The aim of this work is the simple synthesis of MIPs and the optimal performance of the molecular recognition of 4-MDMC. Moreover, the synthesized MIPs can be easily regenerated and repeatedly used with negligible loss of efficiency (only 9.94% loss after six times adsorption–desorption tests). Satisfying recoveries in the range of 69.3–78.9% indicate that MIPs have good applicability for analyte removal from urine samples. Ultimately, this material shows great promise for the rapid extraction and separation of synthetic cathinones, which are dissolved in the liquid for the field of criminal sciences.

Molecularly imprinted polymers, as an adsorbent for extraction and selective recognition of 4-methyldimethcathinone, were firstly synthesized through coprecipitation polymerization.

Protein Denaturation Through the Use of Magnetic Molecularly Imprinted Polymer Nanoparticles

The inhibition of the protein function for therapeutic applications remains challenging despite progress these past years. While the targeting application of molecularly imprinted polymer are in their infancy, no use was ever made of their magnetic hyperthermia properties to damage proteins when they are coupled to magnetic nanoparticles. Therefore, we have developed a facile and effective method to synthesize magnetic molecularly imprinted polymer nanoparticles using the green fluorescent protein (GFP) as the template, a bulk imprinting of proteins combined with a grafting approach onto maghemite nanoparticles. The hybrid material exhibits very high adsorption capacities and very strong affinity constants towards GFP. We show that the heat generated locally upon alternative magnetic field is responsible of the decrease of fluorescence intensity.

Abiotic Mimic of Matrix Metalloproteinase-9 Inhibitor against Advanced Metastatic Cancer

As the most representative family of proteinases related to tumorigenesis, matrix metalloproteinase-9 (MMP-9) represents a key player in cancer cell migration and regulation of the tumor microenvironment. The inhibition of MMP-9 activity has been pursued as a target for anticancer therapy. However, most synthetic MMP-9 inhibitors have failed in clinical trials because of their lack of selectivity. Here, an abiotic mimic based on molecularly imprinted nanoparticles has been designed as an inhibitor for MMP-9. To attain fast mass transfer and facilitate multifunctional roles, we synthesized the imprinted polymer thin layer on the surface of gold nanorods by reversible addition-fragmentation chain transfer polymerization using MMP-9 as the template, which captures MMP-9 selectively and inhibits its activity by providing steric hindrance to the activity-related domain of MMP-9. In vitro cell experiments and in vivo studies in mice demonstrate that the imprinted artificial antibody suppresses the migration and growth of metastatic tumors. The tumor growth inhibition rate reaches up to 54 ± 15%. Compared with the typical photothermal therapy induced by gold nanorods, the use of MMP-9-imprinted synthetic antibody could better inhibit the lung tumor metastasis by quenching the enzyme activity of MMP-9. This study offers a new paradigm in the engineering of imprinted nanoparticles as inhibitors for cancer therapy.

Sequence-Selective Protection of Peptides from Proteolysis

Proteolysis of proteins and peptides is involved in the infection of cells by enveloped viruses and also in the invasion and spread of cancer cells. Shutting down broad‐specificity proteases, however, is problematic because normal functions by these proteases will be affected. Herein, nanoparticle receptors were prepared from molecular imprinting for complex biological peptides. Their strong and selective binding enabled them to protect their targeted sequences from proteolysis in aqueous solution at stoichiometric amounts. Generality of the method was demonstrated by the protection of hydrophobic and hydrophilic peptides from different proteases, selective protection of a segment of a long peptide, and selective protection of a targeted peptide in a mixture. Most interestingly, two receptors targeting different parts of a long peptide could work in cooperation to protect the overall sequence, highlighting the versatility of the method.

Epitope recognition of magnetic peptide-imprinted chitosan composite nanoparticles for the extraction of CRISPR/dCas9a proteins from transfected cells

The clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein (Cas9) technology is a powerful method for genetic modification (and regulation) that is of great current interest. The development of new, economical methods of detecting and extracting Cas9 (and/or dCas9) from transfected cells is thus an important advance. In this work, we employed molecular imprinting, using two peptides from the Cas9 protein, to make magnetic peptide-imprinted chitosan nanoparticles. dCas9 was encoded in a plasmid which was then transfected into human embryonic kidney (HEK293T) cells. The expression of dCas9 protein was measured by using total protein kits. Finally, the imprinted nanoparticles were used to extract dCas9 from transfected cell homogenates.

Advances in epitope molecularly imprinted polymers for protein detection: a review

Epitope molecularly imprinted polymers (EMIPs) are novel imprinted materials using short characteristic peptides as templates rather than entire proteins. To be specific, the amino acid sequence of the template peptide is the same as an exposed N- or C-terminus of a target protein, or its amino acid composition and sequence replicate a similar conformational arrangement as the same amino acid residues on the surface of the target protein. EMIPs have a good application prospect in protein research. Herein, we focus on classification of epitope imprinting techniques, methods of epitope immobilization on matrix materials including boronate affinity immobilization, covalent bonding immobilization, physical adsorption immobilization and metal ion chelation immobilization, and application of EMIPs in peptides, proteins, target imaging and target therapy fields. Finally, the main problems and future development are summarized.

Synthesis of molecularly imprinted polymers based on boronate affinity for diol-containing macrolide antibiotics with hydrophobicity-balanced and pH-responsive cavities

In this research, in order to separate and purify diol-containing macrolide antibiotics, like tylosin, from complex biological samples, molecularly imprinted polymer (MIP) based on boronate affinity for tylosin was synthesized by using precipitation polymerization method with 4-vinylphenylboronic acid (VPBA) and dimethyl aminoethyl methacrylate (DMAEMA) as pH-responsive functional monomers, and N,N'-methylene bisacrylamide (MBAA)/ ethylene glycol dimethacrylate (EGDMA) as the co-crosslinkers that balance the hydrophobicity of the MIP. The synthesized tylosin-MIP had the advantages of high adsorption capacity (120 mg/g), fast pH-responsiveness responsible for the accessibility of imprinted cavities, and high selectivity coefficient towards tylosin versus its analogues (2.8 versus spiramycin, 7.3 versus desmycosin) in an aqueous environment. The mechanism of boronate affinity between tylosin and VPBA in the form of charged hydrogen bonding was analyzed via density functional theory (DFT). MIPs were used to successfully separate diol-containing macrolides through molecularly imprinted solid phase extraction (MISPE). The results show that MIPs prepared in this method have a good application prospect in the separation and purification of the diol-containing macrolide antibiotics.

Molecularly Imprinted Polymer-Based Smart Prodrug Delivery System for Specific Targeting, Prolonged Retention, and Tumor Microenvironment-Triggered Release

Prodrug and drug delivery systems are two effective strategies for improving the selectivity of chemotherapeutics. Molecularly imprinted polymers (MIPs) have emerged as promising carriers in targeted drug delivery for cancer treatment, but they have not yet been integrated with the prodrug strategy. Reported here is an MIP-based smart prodrug delivery system for specific targeting, prolonged retention time, and tumor microenvironment-triggered release. 5'-Deoxy-5-fluorocytidine (DFCR) and sialic acid (SA) were used as a prodrug and a marker for tumor targeting, respectively. Their co-imprinted nanoparticles were prepared as a smart carrier. Prodrug-loaded MIP specifically and sustainably accumulated at the tumor site and then gradually released. Unlike conventional prodrug designs, which often require in-liver bioconversion, this MIP-based prodrug delivery is liver-independent but tumor-dependent. Thus, this study opens new access to the development of smart prodrug delivery nanoplatforms.