A Pretreatment‐Free,Polymer‐Based Platform Prepared by Molecular Imprinting and Post‐Imprinting Modifications for Sensing Intact Exosomes

Exosomes are small (30–100 nm) membrane vesicles that serve as regulatory agents for intercellular communication in cancers. Currently, exosomes are detected by immuno‐based assays with appropriate pretreatments like ultracentrifugation and are time consuming (>12 h). We present a novel pretreatment‐free fluorescence‐based sensing platform for intact exosomes, wherein exchangeable antibodies and fluorescent reporter molecules were aligned inside exosome‐binding cavities. Such antibody‐containing fluorescent reporter‐grafted nanocavities were prepared on a substrate by well‐designed molecular imprinting and post‐imprinting modifications to introduce antibodies and fluorescent reporter molecules only inside the binding nanocavities, enabling sufficiently high sensitivity to detect intact exosomes without pretreatment. The effectiveness of the system was demonstrated by using it to discriminate between normal exosomes and those originating from prostate cancer and analyze exosomes in tear drops.     

A Programmable Signaling Molecular Recognition Nanocavity Prepared by Molecular Imprinting and Post‐Imprinting Modifications

Inspired by biosystems, a process is proposed for preparing next‐generation artificial polymer receptors with molecular recognition abilities capable of programmable site‐directed modification following construction of nanocavities to provide multi‐functionality. The proposed strategy involves strictly regulated multi‐step chemical modifications: 1) fabrication of scaffolds by molecular imprinting for use as molecular recognition fields possessing reactive sites for further modifications at pre‐determined positions, and 2) conjugation of appropriate functional groups with the reactive sites by post‐imprinting modifications to develop programmed functionalizations designed prior to polymerization, allowing independent introduction of multiple functional groups. The proposed strategy holds promise as a reliable, affordable, and versatile approach, facilitating the emergence of polymer‐based artificial antibodies bearing desirable functions that are beyond those of natural antibodies.     

An Epitope‐Imprinted Biointerface with Dynamic Bioactivity for Modulating Cell–Biomaterial Interactions

In this study, an epitope‐imprinting strategy was employed for the dynamic display of bioactive ligands on a material interface. An imprinted surface was initially designed to exhibit specific affinity towards a short peptide (i.e., the epitope). This surface was subsequently used to anchor an epitope‐tagged cell‐adhesive peptide ligand (RGD: Arg‐Gly‐Asp). Owing to reversible epitope‐binding affinity, ligand presentation and thereby cell adhesion could be controlled. As compared to current strategies for the fabrication of dynamic biointerfaces, for example, through reversible covalent or host–guest interactions, such a molecularly tunable dynamic system based on a surface‐imprinting process may unlock new applications in in situ cell biology, diagnostics, and regenerative medicine.     

Elucidating Molecule–Plasmon Interactions in Nanocavities with 2 nm Spatial Resolution and at the Single‐Molecule Level

The fundamental understanding of the subtle interactions between molecules and plasmons is of great significance for the development of plasmon‐enhanced spectroscopy (PES) techniques with ultrahigh sensitivity. However, this information has been elusive due to the complex mechanisms and difficulty in reliably constructing and precisely controlling interactions in well‐defined plasmonic systems. Herein, the interactions in plasmonic nanocavities of film‐coupled metallic nanocubes (NCs) are investigated. Through engineering the spacer layer, molecule–plasmon interactions were precisely controlled and resolved within 2 nm. Efficient energy exchange interactions between the NCs and the surface within the 1–2 nm range are demonstrated. Additionally, optical dressed molecular excited states with a huge Lamb shift of ≈7 meV at the single‐molecule (SM) level were observed. This work provides a basis for understanding the underlying molecule–plasmon interaction, paving the way for fully manipulating light–matter interactions at the nanoscale.     

Semi‐Covalent Surface Molecular Imprinting of Polymers by One‐Stage Mini‐emulsion Polymerization: Glucopyranoside as a Model Analyte

This paper describes a new type of surface imprinting technique that combines the advantages of both the semi‐covalent approach and one‐stage miniemulsion polymerization. This process has been successfully applied for the preparation of glucose surface‐imprinted nanoparticles. The selective artificial receptors for glucopyranoside were fully characterized by IR, TEM and BET analyses, and their molecular recognition abilities by binding experiments carried out in batch processes. The molecular affinity and selectivity of the glucose molecularly imprinted polymers were accurately quantified. These characteristics are essential for verification of the efficiency of the developed surface imprinting process. The imprinting effect was clearly demonstrated using the batch rebinding method. We have found that the glucose imprinted polymers produced using the optimized one‐stage mini‐emulsion exhibited quite fast kinetics of binding and equilibration with glucopyranoside templates, compared to polymers prepared by bulk polymerization technique, as well as extremely low levels of unspecific bindings. We also demonstrated that glucose molecular imprinted polymer (MIP) exhibited very good selectivity for its original template compared to other glycopyranoside derivatives, such as galactose. Finally, the extraction of the binding properties from isotherms of binding by fitting to the bi‐Langmuir and Freundlich models allowed the determination of the affinity constant distribution of the binding sites. This imprinting protocol allowed the determination of an affinity constant (K_D), involving exclusively H‐bonding interactions, for the glucose MIP ( P2C ) with the best template 1 , in CH₃CN as the solvent system.

     

A Double‐Imprinted Diffraction‐Grating Sensor Based on a Virus‐Responsive Super‐Aptamer Hydrogel Derived from an Impure Extract

The detection of viruses is of interest for a number of fields including biomedicine, environmental science, and biosecurity. Of particular interest are methods that do not require expensive equipment or trained personnel, especially if the results can be read by the naked eye. A new “double imprinting” method was developed whereby a virus‐bioimprinted hydrogel is further micromolded into a diffraction grating sensor by using imprint‐lithography techniques to give a “Molecularly Imprinted Polymer Gel Laser Diffraction Sensor” (MIP‐GLaDiS). A simple laser transmission apparatus was used to measure diffraction, and the system can read by the naked eye to detect the Apple Stem Pitting Virus (ASPV) at concentrations as low as 10 ng mL⁻¹, thus setting the limit of detection of these hydrogels as low as other antigen‐binding methods such as ELISA or fluorescence‐tag systems.     

Plasmonic Nanocavities Enable Self‐Induced Electrostatic Catalysis

The potential of strong interactions between light and matter remains to be further explored within a chemical context. Towards this end herein we study the electromagnetic interaction between molecules and plasmonic nanocavities. By means of electronic structure calculations, we show that self‐induced catalysis emerges without any external stimuli through the interaction of the molecular permanent and fluctuating dipole moments with the plasmonic cavity modes. We also exploit this scheme to modify the transition temperature T_1/2 of spin‐crossover complexes as an example of how strong light–matter interactions can ultimately be used to control a materials responses.     

Active Targeting of Tumors through Conformational Epitope Imprinting

Inspired by the knowledge that most antibodies recognize a conformational epitope because of the epitope’s specific three‐dimensional shape rather than its linear structure, we combined scaffold‐based peptide design and surface molecular imprinting to fabricate a novel nanocarrier harboring stable binding sites that captures a membrane protein. In this study, a disulfide‐linked α‐helix‐containing peptide, apamin, was used to mimic the extracellular, structured N‐terminal part of the protein p32 and then serve as an imprinting template for generating a sub‐40 nm‐sized polymeric nanoparticle that potently binds to the target protein, recognizes p32‐positive tumor cells, and successfully mediates targeted photodynamic therapy in vivo. This could provide a promising alternative for currently used peptide‐modified nanocarriers and may have a broad impact on the development of polymeric nanoparticle‐based therapies for a wide range of human diseases.     

Fluorescent Triazole Urea Activity‐Based Probes for the Single‐Cell Phenotypic Characterization of Staphylococcus aureus

Phenotypically distinct cellular (sub)populations are clinically relevant for the virulence and antibiotic resistance of a bacterial pathogen, but functionally different cells are usually indistinguishable from each other. Herein, we introduce fluorescent activity‐based probes as chemical tools for the single‐cell phenotypic characterization of enzyme activity levels in Staphylococcus aureus. We screened a 1,2,3‐triazole urea library to identify selective inhibitors of fluorophosphonate‐binding serine hydrolases and lipases in S. aureus and synthesized target‐selective activity‐based probes. Molecular imaging and activity‐based protein profiling studies with these probes revealed a dynamic network within this enzyme family involving compensatory regulation of specific family members and exposed single‐cell phenotypic heterogeneity. We propose the labeling of enzymatic activities by chemical probes as a generalizable method for the phenotyping of bacterial cells at the population and single‐cell level.     

Boronate‐Affinity Glycan‐Oriented Surface Imprinting: A New Strategy to Mimic Lectins for the Recognition of an Intact Glycoprotein and Its Characteristic Fragments

Lectins possess unique binding properties and are of particular value in molecular recognition. However, lectins suffer from several disadvantages, such as being hard to prepare and showing poor storage stability. Boronate‐affinity glycan‐oriented surface imprinting was developed as a new strategy for the preparation of lectin‐like molecularly imprinted polymers (MIPs). The prepared MIPs could specifically recognize an intact glycoprotein and its characteristic fragments, even within a complex sample matrix. Glycan‐imprinted MIPs could thus prove to be powerful tools for important applications such as proteomics, glycomics, and diagnostics.     

Enzyme‐Initiated Free‐Radical Polymerization of Molecularly Imprinted Polymer Nanogels on a Solid Phase with an Immobilized Radical Source

An enzyme‐mediated synthetic approach is described for the preparation of molecularly imprinted polymer nanoparticles (MIP‐NPs) in aqueous media. Horseradish peroxidase (HRP) was used to initiate the polymerization of methacrylate or vinyl monomers and cross‐linkers by catalyzing the generation of free radicals. To prevent entrapment of the enzyme in the cross‐linked polymer, and to enable it to be reused, HRP was immobilized on a solid support. MIPs based on 4‐vinylpyridine and 1,4‐bis(acryloyl)piperazine for the recognition of 2,4‐dichlorophenoxyacetic acid (2,4‐D) and salicylic acid were synthesized in an aqueous medium. MIPs for the protein trypsin were also synthesized. MIP nanoparticles with sizes between 50 and 300 nm were obtained with good binding properties, a good imprinting effect, and high selectivity for the target molecule. The reusability of immobilized HRP for MIP synthesis was shown for several batches.     

Imprinted Photonic Hydrogels for the Size‐ and Shell‐Selective Recognition of Nanoparticles

Sensors based on responsive photonic hydrogels have recently attracted considerable attention for visual medical diagnostics, pharmaceutical bioassays, and environmental monitoring. However, the use of these promising materials for the detection of nanoparticles (NPs) has never been explored so far, although the sensing of nanoobjects is a rapidly evolving area of research. To address this issue, we have combined the concepts of inverse‐opal hydrogels and nanoparticle‐imprinted polymers. In this way, we could obtain a NP‐imprinted photonic hydrogel consisting of a three‐dimensional, highly ordered poly(methacrylic acid) macroporous array, in which nanocavities complementary to the target NPs, in this case colloidal quantum dots, are distributed. This novel type of NP‐imprinted photonic hydrogel sensor was shown to display high sensitivity and selectivity, thus opening new prospects for the development of equipment‐free and cost‐efficient sensing devices for NPs.     

分子印迹水相分离技术及其在分析化学中的应用

分子印迹分离技术通过模拟抗体-抗原相互作用原理,专一地与目标分子互补性结合,从而将目标分子与杂质分离,是一种非常具有发展前景的分离技术。传统的分子印迹技术通常是在有机相中制备对印迹分子具有选择性的印迹聚合物,然而分子印迹技术的实际应用环境大多是水相体系。近年来,分子印迹水相分离技术受到了科学工作者的广泛关注。本文分别从以下几个方面总结了分子印迹水相分离技术的最新研究进展:水相中分子印迹聚合物的设计原理与合成方法;印迹聚合物在水相中的作用机制;印迹水相分离技术在分析化学中的应用。最后讨论了该项技术现存的问题,并对其未来发展进行了展望。     

Rhodamine Spiroamides for Multicolor Single‐Molecule Switching Fluorescent Nanoscopy

The design, synthesis, and evaluation of new rhodamine spiroamides are described. These molecules have applications in optical nanoscopy based on random switching of the fluorescent single molecules. The new markers may be used in (co)localization studies of various objects and their (mutual) positions and shape can be determined with a precision of a few tens of nanometers. Multicolor staining, good photoactivation, a large number of emitted photons, and selective chemical binding with amino or thiol groups were achieved due to the presence of various functional groups on the rhodamine spiroamides. Rigidized sulfonated xanthene fragment fused with six‐membered rings, N,N′‐bis(2,2,2‐trifluoroethyl) groups, and a combination of additional double bonds and sulfonic acid groups with simple aliphatic spiroamide residue provide multicolor properties and improve performance of the rhodamine spiroamides in photoactivation and bioconjugation reactions. Having both essential parts of the photoswitchable assembly—the switching and the fluorescent (reporter) groups—combined in one chemical entity make this approach attractive for further development. A series of rhodamine spiroamides is presented along with characterizations of their most relevant properties for application as fluorescent probes in single‐molecule switching and localization microscopy. Optical images with resolutions on the nanometer scale illustrate the potential of the labels in the colocalization of biological objects and the two‐photon activation technique with optical sectioning.     

Preparation and application of hollow molecularly imprinted polymers with a super‐high selectivity to the template protein

Protein‐imprinted polymers with hollow cores that have a super‐high imprinting factor were prepared by etching the core of the surface‐imprinted polymers that used silica particles as the support. Lysozyme as template was modified onto the surface of silica particles by a covalent method, and after polymerization and the removal of template molecules, channels through the polymer layer were formed, which allowed a single‐protein molecule to come into the hollow core and attach to the binding sites inside the polymer layer. The adsorption experiments demonstrated that the hollow imprinted polymers had an extremely high binding capacity and selectivity, and thus a super‐high imprinting factor was obtained. The as‐prepared imprinted polymers were used to separate the template lysozyme from egg white successfully, indicating its high selectivity and potential application in the field of separation of protein from real samples.     

Rational Fabrication of Anti‐Freezing,Non‐Drying Tough Organohydrogels by One‐Pot Solvent Displacement

Tough hydrogels, polymeric network structures with excellent mechanical properties (such as high stretchability and toughness), are emerging soft materials. Despite their remarkably mechanical features, tough hydrogels exhibit two flaws (freezing around the icing temperatures of water and drying under arid conditions). Inspired by cryoprotectants (CPAs) used in the inhibition of the icing of water in biological samples, a versatile and straightforward method is reported to fabricate extreme anti‐freezing, non‐drying CPA‐based organohydrogels with long‐term stability by partially displacing water molecules within the pre‐fabricated hydrogels. CPA‐based Ca‐alginate/polyacrylamide (PAAm) tough hydrogels were successfully fabricated with glycerol, glycol, and sorbitol. The CPA‐based organohydrogels remain unfrozen and mechanically flexible even up to −70 °C and are stable under ambient conditions or even vacuum.     

Surface‐imprinted microspheres prepared by a template‐oriented method for the chiral separation of amlodipine

The surface imprinting technique has been developed to overcome the mass‐transfer difficulty, but the utilization ratio of template molecules in the imprinting procedure still remains a challengeable task to be improved. In this work, specifically designed surface‐imprinted microspheres were prepared by a template‐oriented method for enantioseparation of amlodipine besylate. Submicron mesoporous silica microspheres were surface‐modified with double bonds, followed by polymerizing methacrylic acid to generate carboxyl modified mesoporous silica microspheres (PMAA@SiO₂). Afterwards, PMAA@SiO₂ was densely adsorbed with (S )‐amlodipine molecules to immobilize template molecules through multiple hydrogen bonding interactions. Then surface molecular imprinting was carried out by cross‐linking the carboxyl group of PMAA@SiO₂ with ethylene glycol diglycidyl ether. The surface‐imprinted microspheres showed fast binding kinetics of only 20 min for equilibrium adsorption, and the saturation adsorption capacity reached 137 mg/g. The imprinted materials displayed appreciable chiral separation ability when used as column chromatography for enantioseparation of amlodipine from amlodipine besylate, and the enantiomeric excess of (S )‐amlodipine reached 13.8% with only 2.3 cm column length by no extra chiral additives. Besides, the imprinted materials exhibited excellent reusability, and this allows the potential application for amplification production of amlodipine enantiomer.     

Imaging Endogenous Metal Ions in Living Cells Using a DNAzyme–Catalytic Hairpin Assembly Probe

DNAzymes are a promising platform for metal ion detection, and a few DNAzyme‐based sensors have been reported to detect metal ions inside cells. However, these methods required an influx of metal ions to increase their concentrations for detection. To address this major issue, the design of a catalytic hairpin assembly (CHA) reaction to amplify the signal from photocaged Na⁺‐specific DNAzyme to detect endogenous Na⁺ inside cells is reported. Upon light activation and in the presence of Na⁺, the NaA43 DNAzyme cleaves its substrate strand and releases a product strand, which becomes an initiator that trigger the subsequent CHA amplification reaction. This strategy allows detection of endogenous Na⁺ inside cells, which has been demonstrated by both fluorescent imaging of individual cells and flow cytometry of the whole cell population. This method can be generally applied to detect other endogenous metal ions and thus contribute to deeper understanding of the role of metal ions in biological systems.     

Selective Engineering of Linkage‐Specific α2,6‐N‐Linked Sialoproteins Using Sydnone‐Modified Sialic Acid Bioorthogonal Reporters

The metabolic oligosaccharide engineering (MOE) strategy using unnatural sialic acids has recently enabled the visualization of the sialome in living systems. However, MOE only reports on global sialylation and dissected information regarding subsets of sialosides is missing. Described here is the synthesis and utilization of sialic acids modified with a sydnone reporter for the metabolic labeling of sialoconjugates. The positioning of the reporter on the sugar significantly altered its metabolic fate. Further in vitro enzymatic assays revealed that the 9‐modified neuraminic acid is preferentially accepted by the sialyltransferase ST6Gal‐I over ST3Gal‐IV, leading to the favored incorporation of the reporter into linkage‐specific α2,6‐N‐linked sialoproteins. This sydnone sugar presents the possibility of investigating the roles of specific sialosides.