Preparation of dual-epitopes imprinted particles with γ-cyclodextrin host-guest interaction and reversible addition-fragmentation chain transfer strategy for cytochrome c collaborative recognition

A dual-epitopes imprinted strategy for cytochrome c selective recognition assisted with γ-cyclodextrin host-guest interaction via N-terminal and C-terminal epitope's simultaneous imprinting and reversible addition-fragmentation chain transfer (RAFT) polymerization was developed. N-terminal and C-terminal nonapeptides of Cyt c (GI-9 and AE-9) were used simultaneously as the epitope to achieve collaborative recognition for cytochrome c. As a supramolecule, γ-cyclodextrin can encapsulate the aromatic functional groups of amino acid residues to capture the peptide and improve the corresponding spatial orientation for epitope or cytochrome c recognition by host-guest interaction. After the γ-cyclodextrin modification and dual-epitopes immobilization, the imprinted polymer was synthesized by RAFT polymerization with 4-cyano-4-(phenyl-carbonothioylthio) pentanoic acid as a chain transfer agent. After the template removal, the obtained dual-epitopes imprinted particles showed well binding ability to AE-9 (26.50 mg·g-1, IF= 4.13), GI-9 (7.36 mg·g-1, IF= 2.18) and cytochrome c (79.56 mg·g-1, IF= 3.27). With the successive addition of RAFT agent, the imprinting factor rising of epitope peptide and cytochrome c further illustrated the regulation of imprinted polymer chains. The imprinted particles had the advantage for cytochrome c recognition compared to other proteins and good reusability with 82.60 % repeated reproduction rate after six cycles of adsorption and desorption. Furthermore, the selective recognition for cytochrome c in bovine serum proved its potentiality to be applied in complex biological samples. It indicated that the combination of dual-templates epitope imprinting, γ-CD host-guest interaction and RAFT polymerization provided an efficient method for collaborative protein recognition with well selectivity, reusability and stability.

Synthesis of Raspberry-like PMMA Particles In a Ternary Solvent Mixture with Binary Initiators

There is continuing interest in the synthesis of raspberry-like polymer particles, among which most of the reports have tended to focus on polymer composite particles, while there are relatively few examples of polymer particles with a single component. In this study, raspberry-like poly(methyl methacrylate)(PMMA) particles were synthesized by a one-step method in a ternary solvent mixture with binary initiators. The effects of different polymerization parameters, including the solvent composition, the initiator composition, the stabilizer component, the polymerization temperature, the stirring rate, and the nature of the monomer, on the morphology and size of the resulting particles were studied. A plausible mechanism for raspberry-like particle formation was suggested based on the monitoring data of the polymerization kinetics. The raspberry-like PMMA particles have a high dispersion stability in a salty aqueous environment.

Facile Preparation of Raspberry-Like SiO2@Polyurea Microspheres with Tunable Wettability and Their Application for Oil-Water Separation

Raspberry-like microspheres have been widely used as superhydrophobic materials, photonic crystals, drug carriers, etc. Nevertheless, their preparation methods, usually consisting of multiple steps, are generally time- and energy-consuming. Herein raspberry-like SiO2@polyurea microspheres (SiO2@PUM) are readily prepared via a one-step precipitation polymerization of isophorone diisocyanate in a H2O/acetone mixture with the presence of SiO2 particles. The sphere size, surface roughness, and SiO2 content of SiO2@PUM are easily adjustable by varying the experimental conditions. TEM and SEM observations reveal that the final SiO2@PUM exhibits a core-shell structure, with polyurea (PU) in the core and SiO2 particles as the shell. In the process, the SiO2 particles were initially located on the PUM surface as a monolayer. With the reaction proceeding, the monolayer of SiO2 particles became thicker, forming a thicker layer of SiO2 particles on PUM due to the accumulation of SiO2 particles, leading to a multilayer structure of SiO2 particles on the shell of SiO2@PUM. The formation mechanism of the raspberry-like SiO2@PUM was thoroughly discussed and ascribed to electrostatic attraction between the positively charged PU and negatively charged SiO2 particles. Once dried, SiO2@PUM was superhydrophobic and turned hydrophilic if water-wetted. Using a layer of SiO2@PUM, effective separation with good reusability for a variety of oil-water mixtures was achieved regardless of the oil density and types of oil-water emulsions. This work presents a novel protocol for the preparation of raspberry-like microspheres with tunable wettability via a rapid and green process, and the resulting microspheres are highly effective for the separation of diverse types of oil-water mixtures.

Enhancing Cytochrome C Recognition and Adsorption through Epitope-Imprinted Mesoporous Silica with a Tailored Pore Size

We have reported the synthesis of epitope-imprinted mesoporous silica (EIMS) with an average pore size of 6.2 nm, which is similar to the geometrical size of the target protein, cytochrome C (Cyt c, 2.6 × 3.2 × 3.3 nm3), showing great recognition and large-scale adsorption performance. The characteristic fragment of Cyt c was used as a template and docked onto the surface of C16MIMCl micelles via multiple interactions. Nitrogen adsorption-desorption and transmission electron microscopy confirmed the successful preparation of EIMS. Due to the ordered pore structure, larger pore size, and high specific surface area, the prepared EIMS show superior specificity (IF = 3.8), excellent selectivity toward Cyt c, high adsorption capacity (249.6 mg g-1), and fast adsorption equilibrium (10 min). This study demonstrates the potential application of EIMS with a controllable pore size for high-effective and large-scale separation of Cyt c, providing a new approach for effective biomacromolecular recognition.

Preparation of lysozyme-imprinted mesoporous Zr-based metal-organic frameworks with remarkable specific recognition

The development of high-performance protein-imprinted materials remains challenging due to defects concerning high mass transfer resistance and non-specific binding, which are crucial for protein purification and enrichment. In this paper, lysozyme-imprinted mesoporous Zr-based MOF (mesoUiO-66-NH2@MIPs) with specific and selective recognition of lysozyme (Lyz) were prepared by surface imprinting technology. In particular, the excellent hydrophilicity mesoporous MOFs (mesoUiO-66-NH2) with a pore size of 10 nm was prepared as a carrier for Lyz immobilization by an auxiliary modulation strategy to regulate the microporous structure of UiO-66-NH2 with the propionic acid solution, enabling massive loading of the macromolecular protein Lyz. The mesoUiO-66-NH2@MIPs reached a maximum saturation adsorption of 206.54 mg g-1 on Lyz in 20 min at 25 °C with an imprinting factor of 2.57 and selection factors of 2.02, 2.34, and 2.45 for cytochrome c (Cyt c), bovine serum albumin (BSA) and bovine hemoglobin (BHb), respectively. More importantly, the mesoUiO-66-NH2@MIPs could specifically recognize Lyz from the mixed protein system. The adsorption capacity of Lyz could still reach 78.55% after 5 cycles with good cyclic regeneration performance. This provides a new research option for developing and applying novel porous MOF in biomolecule imprinting technology and the specific separation of biomolecules.

Functional thiolactone assisted imprinting cavities with abundant amines for strong binding of protein imprinted nanospheres

In order to develop new protein imprinting polymerization methods and to prepare protein imprinted nanomaterials with high recognition, a novel protein imprinted strategy is developed in this study by using polyethyleneimine (PEI) for aminolysis of tailor-made thiolactone-based functional monomers and crosslinkers on amine-modified magnetic nanospheres in an aqueous medium. The prepared protein imprinted nanospheres can seize BSA templates in the imprinting polymerization process through multiple hydrogen bonds, and hydrophobic and electrostatic interactions. In addition, the aminolysis reaction also generates abundant amide bonds in the imprinting polymer network, which not only enhances the hydrogen bonding interactions between the imprinted nanospheres and BSA but also improves the stability of the imprinting cavities by increasing the rigidity of the polymer chains. Based on the above advantages, the protein imprinted nanospheres show excellent rebinding specificity for BSA, for which the rebinding capacity is up to 505 ± 15 mg g^-1 and the imprinting factor is 4.09. The protein imprinted nanospheres exhibit fast adsorption kinetics, outstanding reusability, and can selectively separate BSA from a protein mixture and actual biological samples. The generality of this imprinted method is also verified. Thus, this study will provide a new idea for the design of protein imprinted materials with high recognition.

Ring -opening of polythiolactones to construct protein-imprinted nanospheres with high recognition and regulation capabilities

Developing and preparing novel protein-imprinted nanomaterials with high recognition ability remains challenging because it is difficult to controllably and orderly design and arrange functional groups on the imprinted polymer layers of protein-imprinted nanomaterials to improve their protein identification. Herein, we present a new technology using rationally designed polythiolactone-decorated magnetic nanospheres as the precursor of multifunctionalized imprinted materials. Moreover, the strategy of ring-opening the polythiolactione layers using primary amines with terminal alcohols, acids and pyrrolidines introduces abundant recognition sites, which enhance the recognition for template proteins through multiple hydrogen-bonding and hydrophobic interactions. Thiols generated in situ by the ring-opening reaction provide sufficient crosslinking sites proximate to each recognition site for the formation of imprinting cavities, endowing the imprinted nanospheres with promising regulation capabilities. Based on the rational design, the imprinted nanospheres can be prepared conveniently and present tunable rebinding capacity and specificity for bovine serum albumin (BSA). The maximum saturated rebinding capacity of imprinted materials for BSA is up to 285 ± 15 mg g^-1 and the highest imprinting factor reaches 5.79. The simple and versatile strategy demonstrated in this study shows promise for the design of other protein-imprinted materials with high recognition ability.

A novel ratiometric electrochemical sensor for the selective detection of citrinin based on molecularly imprinted poly(thionine) on ionic liquid decorated boron and nitrogen co-doped hierarchical porous carbon

Citrinin can cause serious human diseases, thus its detection in foods is necessary. Herein, a molecularly imprinted polymer-based ratiometric electrochemical sensor (MIP-RECS) was presented for citrinin detection. The sensor was fabricated by electropolymerization, using thionine as monomer and citrinin as template. The ionic liquid decorated boron and nitrogen co-doped hierarchical porous carbon (BN-HPC) as supporter, provided large surface for anchoring thionine and citrinin. Poly(thionine) not only acted as MIP, but also acted as reference probe. When [Fe(CN)₆] ^3-/4- was adopted as indicating probe, the resulting sensor demonstrated a wide linear detection range (i.e. 1 × 10^-3-10 ng mL^-1) and a low detection limit (i.e. 1 × 10^-4 ng mL^-1).The sensor was applied to the detection of spiked citrinin in real samples, and satisfactory recovery (i.e. 97% - 110%) was obtained. Hence, it was promising for citrinin detection.

Synthetic strategies for raspberry-like polymer composite particles

The strategies used for the preparation of raspberry-like polymer composite particles are summarized comprehensively.

Integrating ionic liquids with molecular imprinting technology for biorecognition and biosensing: A review

As promising alternatives to natural receptors, artificial molecularly imprinted polymers (MIPs) have received great attention in biotechnology. Nevertheless, some bottlenecks limit their further development, including low adsorption capacity, poor recognition efficiency, slow response, and insipid aqueous compatibility. Ionic liquids (ILs) show the features of tailored structures and properties, high conductivity, good solubility, and excellent stability. Because of these advantages, they have found intensive use in MIPs by remedying the latter's shortcomings. In this review, we summarize the integration of ILs and MIPs for biorecognition and biosensing. The versatile roles of ILs in improving the performance of MIPs are firstly summarized, including serving as solvents, porogens, functional monomers, organic surface modifiers, dummy templates, and cross-linkers. Then, specific applications of IL-based MIPs in peptide recognition, protein sensing, and food safety analysis are discussed. Finally, future trends and challenges for the design and development of IL-based MIPs and their applications in the biorecognition and biosensing are proposed.

Molecularly Imprinted Materials for Selective Biological Recognition

Molecular imprinting is an approach of generating imprinting cavities in polymer structures that are compatible with the target molecules. The cavities have memory for shape and chemical recognition, similar to the recognition mechanism of antigen-antibody in organisms. Their structures are also called biomimetic receptors or synthetic receptors. Owing to the excellent selectivity and unique structural predictability of molecularly imprinted materials (MIMs), practical MIMs have become a rapidly evolving research area providing key factors for understanding separation, recognition, and regenerative properties toward biological small molecules to biomacromolecules, even cell and microorganism. In this review, the characteristics, morphologies, and applicability of currently popular carrier materials for molecular imprinting, especially the fundamental role of hydrogels, porous materials, hierarchical nanoparticles, and 2D materials in the separation and recognition of biological templates are discussed. Moreover, through a series of case studies, emphasis is given on introducing imprinting strategies for biological templates with different molecular scales. In particular, the differences and connections between small molecular imprinting (bulk imprinting, "dummy" template imprinting, etc.), large molecular imprinting (surface imprinting, interfacial imprinting, etc.), and cell imprinting strategies are demonstrated in detail. Finally, future research directions are provided.

Non-covalent loading of ionic liquid-functionalized nanoparticles for bovine serum albumin: experiments and theoretical analysis

Biomacromolecule-based nanomaterials have attracted much attention due to their excellent function in sensing, catalysis, medicine, biology and recognition. In this work, a silane-coupling ionic liquid, 1-(3-trimethoxysilylpropyl)-3-methylimidazolium chloride ([TMIM]Cl), was synthesized and applied to prepare ionic liquid-functionalized nanoparticles (SiO₂@IL) using surface grafting technology. By employing multiple non-covalent interactions, including electrostatic interactions, hydrogen bonding and π–π stacking, the obtained functional nanoparticles were able to bind bovine serum albumin (BSA) with strong binding affinity, which has been illustrated through experiments and theoretical calculations. Moreover, the stability of SiO₂@IL further demonstrated that it is promising in applications for biomacromolecule immobilization.

Non-covalent binding between nanosilica and bovine serum albumin has been illustrated by experiments and theoretical calculations.

A simple functionalized silica microsphere for fast PETN vapor detection based on fluorescence color changes via a catalyzed oxidation process

A fluorene substituted vinyl-SiO microsphere performs a rapid fluorescence color change via oxidation with highly selective PETN catalysis.

Enhancing adsorption capacity while maintaining specific recognition performance of mesoporous silica: a novel imprinting strategy with amphiphilic ionic liquid as surfactant

In order to facilitate the broad applications of molecular recognition materials in biomedical areas, it is critical to enhance their adsorption capacity while maintaining their excellent recognition performance. In this work, we designed and synthesized well-defined peptide-imprinted mesoporous silica (PIMS) for specific recognition of an immunostimulating hexapeptide from human casein (IHHC) by using amphiphilic ionic liquid as the surfactant to anchor IHHC via a combination of one-step sol-gel method and docking oriented imprinting approach. Thereinto, theoretical calculation was employed to reveal the multiple binding interactions and dual-template configuration between amphiphilic ionic liquid and IHHC. The fabricated PIMS was characterized and an in-depth analysis of specific recognition mechanism was conducted. Results revealed that both adsorption and recognition capabilities of PIMS far exceeded that of the NIMS's. More significantly, the PIMS exhibited a superior binding capacity (60.5 mg g^-1), which could increase 18.9% than the previous work. The corresponding imprinting factor and selectivity coefficient could reach up to 4.51 and 3.30, respectively. The PIMS also possessed lickety-split kinetic binding for IHHC, where the equilibrium time was only 10 min. All of these merits were due to the high surface area and the synergistic effect of multiple interactions (including hydrogen bonding, π-π stacking, ion-ion electrostatic interactions and van der Waals interactions, etc) between PIMS and IHHC in imprinted sites. The present work suggests the potential application of PIMS for large-scale and high-effective separation of IHHC, which may lead to their broad applications in drug/gene deliver, biosensors, catalyst and so on.

Preparation of Molecularly Imprinted Mesoporous Materials for Highly Enhancing Adsorption Performance of Cytochrome C

Molecularly imprinted mesoporous materials (MIMs) were synthesized to improve the adsorption performance of Cytochrome c (Cyt c) by using an imidazolium-based amphiphilic ionic liquid 1-octadecyl-3-methylimidazolium chloride (C18MIMCl) as surfactant in aqueous solution via the epitope imprinting approach. The surface-exposed C-terminus nonapeptide of Cyt c (residues 96⁻104, AYLKKATNE) was utilized as the imprinted template. The nitrogen adsorption-desorption, thermo-gravimetric analysis, and transmission electron microscopy verified the successful preparation of MIMs with ordered mesoporous structure. The adsorption isotherm studies showed that the obtained MIMs exhibited superior adsorption capacity toward Cyt c of 86.47 mg·g-1 because of the high specific surface areas of 824 m²·g-1, and the appropriate pore size promoted the mass transfer of Cyt c, causing a rapid adsorption equilibrium within 20 min. Furthermore, these MIMs still remained excellent selectivity and recognition ability according to the selective as well as the competitive adsorption studies, suggesting that the molecularly imprinted mesoporous materials is expected to be used in the field of highly efficient separation and enrichment of proteins.

Preparation of highly cross-linked raspberry-like nano/microspheres and surface tailoring for controlled immunostimulating peptide adsorption

The surface functionalities of ionic liquid-functionalized nano/microspheres with a highly cross-linked raspberry-like structure could be well controlled by adjusting the functional chains appropriately.