Controlled synthesis of open-mouthed epitope-imprinted polymer nanocapsules with a PEGylated nanocore and their application for fluorescence detection of target protein

Epitope imprinting is an effective way to create artificial receptors for protein recognition. Surface imprinting with immobilized templates and sacrificial supports can generate high-quality imprinted cavities of homogeneous orientation and good accessibility, but it is still challenging to fabricate nanoscale imprinted materials by this approach. Herein, we propose a method for the controlled synthesis of open-mouthed epitope-imprinted polymer nanocapsules (OM-MIP NCs) by limiting the imprinting polymerization on the template-bearing side of the Janus nanoparticles (JNPs). Concurrent bromoacetyl (Ac–Br) and 2-bromoisobutyryl (iB–Br) functionalization of the major portion of SiO₂ nanoparticles is achieved via the molten-wax-in-water Pickering emulsion approach. The cysteinyl-derived epitope templates are immobilized through the Ac–Br groups, and then surface imprinting is fulfilled via ATRP initiated by the iB–Br groups. The SiO₂ supports are partially etched and then PEGlated, affording OM-MIP NCs with a PEGylated nanocore. The inside nanocore can facilitate collection of the NCs by centrifugation, and its PEGylation can inhibit non-specific binding. The surface imprinting can be optimized through the ATRP time, and the etching can be tailored via the concentration of NH₄HF₂ employed. For proof-of-concept, with a C-terminus nonapeptide of bovine serum albumin (BSA) chosen as a model epitope and polymerizable carbon dots added to the pre-polymerization solution, fluorescent OM-MIP NCs were fabricated for BSA sensing. The as-synthesized NCs exhibited satisfactory detection performance, with an imprinting factor of 6.1, a limit of detection of 38.1 nM, a linear range of 0.25–6 μM, and recoveries of 98.0 to 104.0% in bovine serum samples.

Surface epitope imprinting over the one side of Janus SiO₂ NPs via ATRP affords open-mouthed epitope-imprinted nanocapsules with imprinted cavities of homogeneous orientation and good accessibility for fluorescence detection of target protein.

A method for synthesis of oriented epitope-imprinted open-mouthed polymer nanocapsules and their use for fluorescent sensing of target protein

Epitope imprinting has proved to be an effective way for fabricating artificial receptors for protein recognition. Surface imprinting over sacrificial supports is particularly favorable for generating high-quality epitope-imprinted cavities, but obtaining nanomaterials by this way is still a challenge. Herein, we propose a method for the synthesis of oriented surface epitope-imprinted open-mouthed polymer nanocapsules (OM-MIP NCs) by sacrificing asymmetric template-modified Janus nanocores. Amine/aldehyde functionalized SiO₂ Janus nanoparticles were prepared via the molten-wax-in-water Pickering emulsion approach, an easy scale-up technique. Epitope templates and vinyl groups were coupled to the aldehyde-bearing major side, whereas polyethylene glycol (PEG) chains were grafted to the amine-modified side. Incomplete imprinted shells were then generated principally on the non-PEGylated side via aqueous precipitation polymerization, hence affording OM-MIP NCs after etching the SiO₂ nanocores. With a C-terminus nonapeptide of bovine serum albumin (BSA) chosen as a model epitope and polymerizable carbon dots added to the pre-polymerization solution, fluorescent OM-MIP NCs were synthesized for sensing of BSA. Such NCs reached maximal fluorescent response within 15 min, greatly faster than the closed imprinted NCs within 130 min, proving good accessibility of their inner-surface imprinted cavities thanks to the open mouths. Furthermore, they showed excellent target protein detection performance, with an imprinting factor of 7.8, a limit of detection of 43.8 nM and a linear range of 0.2-6 μM. The recoveries in bovine serum samples at four spiking levels ranged from 99.2 to 107.2%, with relative standard deviations of 1.2-5.9%.

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.

Molecular Imprints Frozen by Strong Intermolecular Interactions in Place of Cross-Linking

A new way to freeze molecular imprints in a polymer material is reported. So far, molecular imprinted polymers (MIP) involve copolymerization of a functional monomer and large amounts of cross-linking agent, which keeps the template shape memory in rigid molecular imprints. MIP materials are prepared herein without cross-linking agent. Stiff chains of polyaniline grafted on a solid support as a brush-like material achieve the necessary rigidity. Differential adsorption to imprinted and non-imprinted materials provides evidence of molecular imprints. A correct adsorption isotherm for mobile adsorbed layers (Volmer isotherm) is introduced instead of the popular but inadequate Langmuir isotherm. Non-selective adsorption is entropic, whereas adsorption to molecular imprints has an enthalpic contribution coming from specific interactions. Fast adsorption kinetics are a definite benefit with regards to applications such as chromatographic separations and chemical sensors.

Selective Binding of Dopamine and Epinephrine in Water by Molecularly Imprinted Fluorescent Receptors

Catecholamines play important roles in biology but their structural similarity makes it challenging to construct synthetic receptors with selective binding. A combination of covalent and noncovalent binding groups in the hydrophobic core of water-soluble nanoparticles enabled them to recognize dopamine and epinephrine with an association constant (Ka ) of 3-4×104  M-1 in water, an order of magnitude higher than those of previously reported synthetic hosts. In addition, minute structural changes among analogues were detected including the addition or removal of a single hydroxyl or methyl group.

Pipette-like action of a reusable and NIR light-responsive film for the aspiration and removal of viable cancer cells

A reusable and NIR light-responsive composite membrane is developed to capture/release viable cancer cells.

Preparation of Protein Molecular-Imprinted Polysiloxane Membrane Using Calcium Alginate Film as Matrix and Its Application for Cell Culture

Bovine serum albumin (BSA) molecular-imprinted polysiloxane (MIP) membrane was prepared by sol-gel technology, using silanes as the functional monomers, BSA as the template and CaAlg hydrogel film as the matrix. The stress-strain curves of wet CaAlg membrane and molecular-imprinted polysiloxane membrane were investigated. We evaluate the adsorption and recognition properties of MIP membrane. Results showed that the adsorption capacity of BSA-imprinted polysiloxane for BSA reached 28.83 mg/g, which was 2.18 times the non-imprinted polysiloxane (NIP) membrane. The adsorption rate was higher than that of the protein-imprinted hydrogel. BSA-imprinted polysiloxane membrane could identify the protein template from competitive proteins such as bovine hemoglobin, ovalbumin and bovine γ-globulin. In order to obtain the biomaterial that can promote cell adhesion and proliferation, fibronectin (FN)-imprinted polysiloxane (FN-MIP) membrane was obtained by using fibronectin as the template, silanes as functional monomers, and CaAlg hydrogel membrane as the substrate or matrix. The FN-MIP adsorbed more FN than NIP. The FN-imprinted polysiloxane membrane was applied to culture mouse fibroblast cells (L929) and the results proved that the FN-MIP had a better effect on cell adhesion than NIP.