•A novel zwitterion 1-vinyl-3-sulfopropylimidazolium (VSPIM) was synthesized.•The imprinted hydrogels (MIHs) made by VSPIM showed good anti-biofouling capacity.•The MIHs showed good recognition ability for l-phe.A novel zwitterion was synthesized and used as a functional monomer in the synthesis of l-phenylalanine (l-phe) imprinted hydrogel (MIH). Molecular simulation demonstrated that the binding energy of the zwitterion with l-phe was −23.50 kcal mol−1 in the aqueous phase, which was higher than the binding energies of l-phe with other traditional functional monomers. Binding experiments also showed that MIH made using the zwitterion had a higher adsorption capacity and imprinting factor (IF) compared to MIHs made using either acrylic acid or 4-vinylpyridine. Optimization studies showed that the best recognition ability of MIH was obtained when the molar ratio of zwitterion to l-phe was 2:1 in the synthesis of MIH. Adsorption kinetics experiments showed that MIH could equilibrate within 120 min, and adsorption isotherms obtained experimentally demonstrated that MIH had a good adsorption capacity of 9.8 mg g−1 with a high imprinting factor of 2.0 in 0.3 mg mL−1 concentrated l-phe solution. Circular dichroism spectroscopy confirmed the excellent chiral resolution ability of MIH for racemic phenylalanine. Furthermore, MIH prepared using the zwitterion exhibited strong anti-fouling capability and could be utilized to extract l-phe from the protein solution.

•Template immobilization was combined with surface imprinting technology.•Ionic liquid functionalized Fe3O4 nanoparticles was utilized as substrate.•Dopamine was chosen to prepare template-size tailored imprinted layers.•The imprinted nanoparticle showed high adsorption capacity and excellent selectivity.Combining template immobilization with surface imprinting technology is an effective strategy to overcome the difficulties associated with macromolecular template removal and to achieve high specific recognition ability. In this work, ionic liquid functionalized Fe3O4 nanoparticles were prepared via a simple two-step modification process and were used as substrate to immobilize bovine serum albumin (BSA). The zeta potential study revealed immobilization of BSA on the nanoparticles through multiple interactions, and the immobilization capacity was about nine times higher compared with that of bare Fe3O4. Subsequently, dopamine was utilized as functional monomer to prepare BSA surface imprinted nanoparticles. Fourier transform infrared spectroscopy, thermo-gravimetric analysis and transmission electron microscopy verified the successful preparation of BSA imprinted nanoparticles with core-shell structure. The influence of imprinted layer thickness on recognition ability of imprinted nanoparticles was investigated, and the results suggested that 20 nm was an optimum thickness to achieve the best recognition ability. The adsorption isotherm studies showed that the imprinted nanoparticles had a significantly higher adsorption capacity and stronger binding affinity than the non-imprinted ones. Furthermore, the selective as well as the competitive adsorption studies revealed higher selectivity and recognition ability of the imprinted nanoparticles for BSA. Therefore, the proposed strategy is an effective way to obtain protein imprinted polymers with high adsorption capacity and good recognition ability, thus would be beneficial for the further development and application of protein imprinting technology.Download high-res image (247KB)Download full-size image

•Bovine serum albumin was stabilized and imprinted by using a macromolecular chain.•The sensitive monomer was used to prepare macromolecular chain.•Surface imprinting of BSA by macromolecular chains on silica nanoparticles was prepared.•The imprinted silica nanoparticles exhibited excellent selectivity and recognition ability.Structural stability of the template is one of the most important considerations during the preparation of protein imprinting technology. To address this limitation, we propose a novel and versatile strategy of utilizing macromolecularly functional monomers to imprint biomacromolecules. Results from circular dichroism and synchronous fluorescence experiments reflect the macromolecularly functional monomers tendency to interact with the protein surface instead of permeating it and destroying the hydrogen bonds that maintain the protein’s structural stability, therefore stabilizing the template protein structure during the preparation of imprinted polymers. The imprinted polymers composed of macromolecularly functional monomers or their equivalent micromolecularly functional monomers over silica nanoparticles were characterized and carried out in batch rebinding test and competitive adsorption experiments. In batch rebinding test, the imprinted particles prepared with macromolecularly functional monomers exhibited an imprinting factor of 5.8 compared to those prepared by micromolecularly functional monomers with the imprinting factor of 3.4. The selective and competitive adsorption experiments also demonstrated the imprinted particles made by macromolecularly functional monomers possessed much better selectivity and specific recognition ability for template protein. Therefore, using macromolecularly functional monomers to imprint may overcome the mutability of biomacromolecule typically observed during the preparation of imprinted polymers, and thus promote the further development of imprinting technology.

In this study, an assumption that a micromolecular monomer could easily permeate into the inside of a protein and alter its conformation, while an inflexible macromolecular monomer may interact with the surface of the protein and thus maintain the integrity of the template protein's structure was proposed for the first time and confirmed by using circular dichroism and synchronous fluorescence spectroscopy. The protein imprinted hydrogels composed of macromolecular monomers or their equivalent micromolecular monomers were characterized and carried out in the competitive adsorption and adsorption isotherm experiments. The adsorption isotherm behaviours described by the Langmuir model revealed that a higher binding affinity was observed between the template protein and imprinted hydrogels made by a macromolecular monomer. The competitive adsorption results also demonstrated the imprinted hydrogels prepared by the macromolecular monomer exhibited much better specific recognition ability to the template protein. Therefore, the strategy of using a macromolecule to imprint could effectively overcome the mutability of protein during the preparation of imprinted polymers, and consequently would promote the development of imprinting technology.

•We utilized the Hofmeister series to design and synthesis a biocompatible and polymerizable ionic liquid for stabilizing BSA.•We used the biocompatible and polymerizable ionic liquid as stabilizer and co-monomer to synthesis BSA imprinted hydrogels.•The adsorption isotherm showed hydrogels based on ionic liquids might perform multilayer adsorption at the high range of concentration.•The adsorptive selectivity and competition tests revealed BSA imprinted hydrogels made by biocompatible ionic liquid performed excellent recognition ability.•The adsorptive selectivity and competition tests revealed BSA imprinted hydrogels made by biocompatible ionic liquid performed excellent recognition ability.Through consulting the Hofmeister series, a novel biocompatible and polymerizable ionic liquid (IL) was designed and used as stabilizer and co-monomer to prepare bovine serum albumin (BSA) imprinted hydrogels. N-isopropylacrylamide (NIPA) was chosen as the assistant monomer for imparting environmental sensitivity to the hydrogels. The stabilizing effect of the IL was verified by circular dichroism. Several parameters, such as the mass ratio of the template protein, IL and crosslinker, the drying method of hydrogels and the elution method of MIHs that could affect the performance of molecular imprinted hydrogels (MIHs) were investigated. The optimum mass ratio of BSA, IL and crosslinker was found to be 200:30:6. The best drying and preferred elution method for the MIHs was achieved by slowly evaporating and washing with 0.5 M NaCl solution at 15 °C, respectively. The MIHs prepared under optimized conditions were subsequently used in the adsorption isotherm, adsorption dynamics, adsorption selectivity, and competition test. The adsorption isotherm revealed that the MIHs showed the best imprinted effect at a BSA concentration of 0.2 mg mL−1 and their imprinting factor at 2.66. The adsorption dynamic studies revealed that the adsorptive rate of the MIHs was much faster than the non-imprinted hydrogels (NIHs), and both of them could be equilibrated in 1 h. The adsorption selectivity and competition tests were conducted to estimate the specific recognition property of the MIHs for BSA. The MIHs showed excellent selectivity and recognition ability to BSA. The strategy of applying biocompatible and polymerizable ILs to imprinting technology may provide a new approach for effective biomacromolecular imprinting.A polymerizable and biocompatible ionic liquid is designed and used as co-monomer and stabilizer in preparation of bovine serum albumin imprinted hydrogels.