The relationship between childhood socioeconomic status and depression level in older adults: the mediating role of adult socioeconomic status and subjective well-being.

BACKGROUND: There is a causal link between childhood socioeconomic status and health status in adulthood and beyond. It's vital to comprehend the relationship between childhood socioeconomic status and mental health among older Chinese individuals from the current generation who have undergone significant social changes in China. This understanding is critical to foster healthy demographic and social development in China. METHODS: Using data from the 2020 China Family Panel Studies, we investigate the relationship between childhood socioeconomic status and depression in older adults. Additionally, we examine the mediating role of adult socioeconomic status and subjective well-being. RESULTS: 1) Childhood socioeconomic status of Chinese older adults differences by region of residence, while depression levels differences by gender, region of residence, and marital status. 2) Adult socioeconomic status mediated the relationship between childhood socioeconomic status and depression in older adults. 3) Adult socioeconomic status and subjective well-being had a chain-mediated role in the relationship between childhood socioeconomic status and depression in older adults. CONCLUSIONS: In terms of childhood socioeconomic status, older adults in urban regions were significantly higher than those in rural regions. As for depression level, female older adults were more depressed than males; married older people have the lowest depression levels, while unmarried and widowed older people have higher depression levels; older adults in rural regions had higher depression levels than those in urban regions. Evidence from our study further suggests that childhood socioeconomic status can suppress the depression level in older adults through adult socioeconomic status; it can also further reduce the depression level in older adults through the chain mediation of adult economic status affecting subjective well-being. As depression is more prevalent among older individuals with a lower childhood socioeconomic status, it is vital to prioritize the extensive impact of childhood socioeconomic status as a distal factor and investigate "upstream" solutions to enhance childhood socioeconomic status and reduce the gap during the early years of life.

Controlled synthesis of PEGylated surface protein-imprinted nanoparticles.

High recognition selectivity has been the main object in developing protein-imprinted materials. Here, we demonstrate a novel strategy for the controlled synthesis of PEGylated surface protein-imprinted nanoparticles with reduced nonspecific binding, which is based on sequential two steps of surface-initiated reversible addition-fragmentation chain transfer aqueous precipitation polymerization (SI-RAFT APP). Click chemistry was employed to construct hydrophilic nanocores with both high-density RAFT chain transfer agents and template-capturing groups. Through the first-step SI-RAFT APP, protein-imprinted nanoshells were formed over the nanocores using lysozyme as a model template. By the second-step SI-RAFT APP, nonlinear PEG chains were grafted from the core-shell imprinted nanoparticles before the removal of the template. Both the thickness of the imprinted nanoshells and the length of the grafted chains could be readily controlled by the polymerization time. Thus the obtained PEGylated core-shell particles exhibited greatly improved template binding selectivity compared with the non-PEGylated controls, typically with the imprinting factor increasing from 2.1 to 9.1. Meanwhile, the PEGylation process did not impair but significantly enhance the protein binding capacity. The generality of the established approach was preliminarily proved by imprinting another template protein, bovine hemoglobin. This work represents the first example for the controlled synthesis and post-imprinting functionalization of surface protein-imprinted nanoparticles via SI-RAFT polymerization.

Synthesis of thermo-responsive bovine hemoglobin imprinted nanoparticles by combining ionic liquid immobilization with aqueous precipitation polymerization.

Surface molecular imprinting over functionalized nanoparticles has proved to be an effective approach for construction of artificial nanomaterials for protein recognition. Herein, we report a strategy for synthesis of core-shell protein-imprinted nanoparticles by the functionalization of nano-cores with ionic liquids followed by aqueous precipitation polymerization to build thermo-responsive imprinted polymer nano-shells. The immobilized ionic liquids can form multiple interactions with the protein template. The polymerization process can produce thermo-reversible physical crosslinks, which are advantageous to enhancing imprinting and facilitating template removal. With bovine hemoglobin as a model template, the imprinted nanoparticles showed temperature-sensitivity in both dispersion behaviors and rebinding capacities. Compared with the ionic-liquid-modified core nanoparticles, the imprinted particles exhibited greatly increased selectivity and two orders of magnitude higher binding affinity for the template protein. The imprinted nanoparticles achieved relatively high imprinting factor up to 5.0 and specific rebinding capacity of 67.7 mg/g, respectively. These nanoparticles also demonstrated rapid rebinding kinetics and good reproducibility after five cycles of adsorption-regeneration. Therefore, the presented approach may be viable for the fabrication of high-performance protein-imprinted nanoparticles with temperature sensitivity.

Oriented surface imprinting of epitopes anchored on silica nanoparticles containing quantum dots by thiol-disulfide exchange reactions for the enhanced fluorescence detection of proteins.

As artificial receptors for protein recognition, epitope-imprinted polymers combined with fluorescence sensing based on quantum dots (QDs) can be potentially used for biological analysis and disease diagnosis. However, the usual way for fabrication of QD sensors through unoriented epitope imprinting is confronted with the problems of disordered imprinting sites and low template utilization. In this context, a facile and efficient oriented epitope surface imprinting was put forward based on immobilization of the epitope templates via thiol-disulfide exchange reactions. With N-succinimidyl 3-(2-pyridyldithio)-propionate (SPDP) as a heterobifunctional reagent, cysteine-modified epitopes of cytochrome c were anchored on the surface of pyridyl disulfide functionalized silica nanoparticles sandwiching CdTe QDs. After surface imprinting via a sol-gel process, the epitope templates were removed from the surface-imprinted layers simply by reduction of the thiol-disulfide, affording oriented epitope-imprinted sites. By this method, the amount of epitope templates was only 1/20 of traditionally unoriented epitopes. The resulting sensors demonstrated significantly enhanced imprinting performance and high sensitivity, with the imprinting factor increasing from 2.6 to 3.9, and the limit of detection being 91 nM. Such epitope-oriented surface-imprinted method may offer a new design strategy for the construction of high-affinity protein recognition nanomaterials with fluorescence sensing.

Facile and green synthesis of core-shell structured magnetic chitosan submicrospheres and their surface functionalization.

Submicrometer-sized magnetite colloid nanocrystal clusters (MCNCs) provide a new avenue for constructing uniformly sized and highly magnetic composite submicrospheres. Herein, a facile and eco-friendly method is described for the synthesis of Fe3O4@poly(acrylic acid) (PAA)/chitosan (CS) core-shell submicrospheres using MCNCs bearing carboxyl groups as the magnetic cores. It is based on the self-assembly of positively charged CS chains on the surface of the oppositely charged MCNCs dispersed in the aqueous solution containing acrylic acid (AA) and a cross-linker N,N'-methylenebis(acrylamide) (MBA), followed by radical induced cross-linking copolymerization of AA and MBA along the CS chains. The resulting polymer shell comprises a medium shell of cross-linked PAA/CS polyelectrolyte complexes and an outer shell of protonated CS chains. It was found that the shell thickness could be tuned by varying either the concentration of radical initiator or the molar ratio of AA to aminoglucoside units of CS. To the surface of thus obtained Fe3O4@PAA/CS particles, Au nanoparticles, a variety of functional groups such as fluorescein, carboxyl, quaternary ammonium, and aliphatic bromide, and even functional polymer chains were successfully introduced. Therefore, such Fe3O4@PAA/CS submicrospheres may be used as versatile magnetic functional scaffolds in biorelated areas like bioseparation and medical assay, considering the unique features of CS like nontoxicity and biocompatibility.

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.

Synthesis of surface protein-imprinted nanoparticles based on metal coordination and anchored carbon dots for enhanced fluorescence detection.

Molecularly imprinted polymers endowed with photo-luminescent properties have attracted wide research interest in many fields such as biological analysis and diseases diagnosis. Herein, we illustrate a versatile method for the construction of surface protein-imprinted nanoparticles based on metal coordination and anchored carbon dots (CDs) for enhanced fluorescence detection of the target protein. As the fluorescent nanosupports for surface imprinting, CDs-attached SiO2 nanoparticles were synthesized via thiol-ene click chemistry. With histidine (His)-exposed protein as templates, imprinted nanoshells were formed over the nanosupports via copolymerization of a Cu2+-chelating monomer and an oligo (ethylene glycol) monomer, hence producing high-quality imprinted cavities because of both the relatively strong coordination and inhibited non-specific binding. Using lysozyme as a model His-exposed template, the imprinted nanoparticles showed fluorescence enhancement while binding the target protein, and exhibited significantly increased specific fluorescence response than the controls without the metal coordination. They achieved a high imprinting factor of 5.8 and a low limit of detection of 10.1 nM. Furthermore, such sensors were applied to determine lysozyme in diluted chicken egg-white samples with satisfactory recoveries at three spiking levels ranging from 97.9 to 101.4%. Human serum albumin was also used as another template protein for preliminary confirming the generality of the presented strategy.

Oral iron supplementation in patients with heart failure: a systematic review and meta-analysis.

AIMS: This review aimed to assess whether oral iron supplementation in a chronic heart failure (HF) population with iron deficiency (ID) or mild anaemia is safe and effective according to evidence-based medicine. METHODS: We retrieved 1803 records from the PubMed, Embase, and the Cochrane Library databases from 1 January 1991 to 15 September 2021. The clinical outcome of oral iron supplementation for ID anaemia in patients with HF was the primary endpoint. The primary safety measures included adverse events and all-cause mortality, and efficacy measures included transferrin saturation (Tsat), ferritin levels, and the 6-min walk test (6MWT). The rate ratio (RR) was used to pool the efficacy measures. RESULTS: Five randomized controlled trials that compared oral iron treatment for patients with the placebo group and included a combined total of 590 participants were analysed. No significant difference was found in all-cause death between oral iron treatment and placebo groups (RR = 0.77; 95% confidence intervals (CI), 0.46-1.29, Z = 0.98; P = 0.33). However, adverse events were not significantly higher in the iron treatment group (RR = 0.83; 95% CI, 0.60-1.16, Z = 1.07; P = 0.28). In addition, ferritin levels and Tsat were slightly increased after iron complex administration in patients with HF but were not statistically significant (ferritin: mean difference [MD] = 2.70, 95% CI, -2.41 to 7.81, Z = 1.04; P = 0.30; Tsat: MD = 27.42, 95% CI, -4.93 to 59.78, Z = 1.66; P = 0.10). No significant difference was found in exercise capacity, as indicated by the 6MWT results (MD = 59.60, 95% CI, -17.89 to 137.08, Z = 1.51; P = 0.13). We also analysed two non-randomized controlled trials with follow-up results showing that oral iron supplementation increased serum iron levels (MD = 28.87, 95% CI, 1.62-56.12, Z = 2.08; P = 0.04). CONCLUSIONS: Based on the current findings, oral iron supplementation can increase serum iron levels in patients with HF and ID or mild anaemia but does not improve Tsat and 6MWT. In addition, oral iron supplementation is relatively safe.

Enhanced lysozyme imprinting over nanoparticles functionalized with carboxyl groups for noncovalent template sorption.

Surface molecular imprinting, in particular over nanosized support materials, is very suitable for a template of bulky structure like protein. Inspired by the surface template immobilization method reported previously, we herein demonstrate an alternative strategy for enhancing specific recognition of core-shell protein-imprinted nanoparticles through prefunctionalizing the cores with noncovalent template sorption groups. For proof of this concept, silica nanoparticles chosen as the core materials were modified consecutively with 3-aminopropyltrimethoxysilane and maleic anhydride to introduce polymerizable double bonds and terminal carboxyl groups, hence capable of physically adsorbing the print protein. With lysozyme as a template, thin protein-imprinted shells were fabricated according to our newly developed approach for surface protein imprinting over nanoparticles. The rebinding experiments confirmed that the introduction of the carboxyl groups could remarkably improve the imprinting effect in relation to a significantly increased imprinting factor and specific rebinding capacity. Moreover, in contrast to the harsh template removal conditions required for the covalent template coupling approach, the template removal during the imprinted particle synthesis as well as desorption after rebinding could be mildly achieved via washing with salt solution.

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%.

Well-water-dispersed N-trimethyl chitosan/Fe3O4 hybrid nanoparticles as peroxidase mimetics for quick and effective elimination of bacteria.

Fe3O4 nanoparticles, used as peroxidase mimetics, exhibit splendid future in the biomedical field. However, the functionalization on Fe3O4 nanoparticles always goes with the loss of superparamagnetism and decrease in peroxidase-activity. Here, we synthesized green polyethylene glycol (PEG)-functionalized magnetic/N-trimethyl chitosan (CS) hybrid nanoparticles (Fe3O4@PAA/TMC/PEG NPs) with improved water dispersibility, superparamagnetism, high saturation magnetization and well peroxidase-like activity. The functionalized coating was divided in two steps, one involved a cross-linked PEG/PAA/CS middle layer to protect the nanocrystal Fe3O4 from oxidization, the other was a hydrophilic PEG/TMC outer layer improving the water dispersion, biocompatibility, as well as supplying positive quaternary ammonium groups for a potential increase of cell binding efficiency. The structure, composition and morphology of Fe3O4@PAA/TMC/PEG NPs were characterized by TEM, FT-IR spectroscopy, DLS, zeta potential measurement, respectively. Thermal performance was characterized by TGA, and the peroxidase-like mimics activity was tested by TMB·2HCl colour development experiments. The magnetic property of the as-prepared hybrid nanoparticles was first confirmed by VSM, and then proved by the bacterial pathogens adsorption, especially at ultralow pathogen concentration. Particularly, with an external magnet, the Fe3O4@PAA/TMC/PEG NPs, combined cationic quaternary ammonium groups and peroxidise-mimetic catalytic activity, were tested for antibacterial effect by plating method.

PEGylation of protein-imprinted nanocomposites sandwiching CdTe quantum dots with enhanced fluorescence sensing selectivity.

Fluorescent sensors combining the selective recognition of protein molecularly imprinted polymers (MIPs) and the fluorescent sensing of quantum dots (QDs) have been studied considerably, but their fluorescence sensing selectivity for the target proteins remains to be increased. Herein, we propose a strategy for increasing the sensing selectivity by post-imprinting PEGylation of surface protein-imprinted nanocomposites with embedded QDs. With bovine hemoglobin (BHb) as a model protein template, protein MIP nanolayers were anchored over the CdTe QD decorated SiO2 nanoparticles by the sol-gel process using aminopropyltriethoxy silane and tetraethoxysilicane. PEG chains were then grafted onto the surface of the imprinted nanostructures via the nucleophilic reaction of the surface amine groups with N-hydroxysuccinimide ester-terminal methoxy-PEG, followed by template removal. The resultant PEGylated sensors showed significantly improved aqueous dispersion stability compared with the non-PEGylated controls. More importantly, such PEGylation greatly increased the fluorescence response selectivity, with the Stern-Volmer equation based imprinting factor increasing from 2.7 to 5.4. The PEGylated sensors were applied to determine BHb in bovine serum samples with satisfactory recoveries at three spiking levels ranging from 94.3 to 103.7%, indicating their potential application in real samples.

Imprinting effect of protein-imprinted polymers composed of chitosan and polyacrylamide: a re-examination.

In this paper the imprinting effects recently reported with protein-imprinted polymers based on chitosan and polyacrylamide are re-assessed. Molecularly imprinted polymers (MIPs) from which the embedded template molecules were removed by washing with a solution of sodium dodecyl sulfate and acetic acid were prepared. In batch template rebinding experiments, the MIPs displayed quite high template binding capacity as reported previously. However, the non-imprinted polymers (NIPs), after washing with the same solution, also showed large binding capacity nearly equal to that of the MIPs. X-ray diffraction and scanning electronic microscope investigations confirmed remarkable property changes of the NIPs after the washing process. These findings indicate that the non-specific adsorption resulting from the template removing process rather than the imprinted sites generated on the MIPs themselves may account for the high template rebinding capacity of the reported protein-imprinted polymers.

Double-responsive polymer brushes on the surface of colloid particles.

Well-defined poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes were synthesized on the surface of polystyrene latex particles by atom transfer radical polymerization (ATRP). It was found that the surface-initiated polymerization of DMAEMA catalyzed by CuCl/CuCl(2)/bpy was under good control in the solvent of acetone/water at ambient temperature (35 degrees C). High-density PDMAEMA brushes with low polydispersity (PDI 1.21) were obtained. TEM results demonstrate that the PDMAEMA-grafted particles have core-shell structure. Dynamic light scattering studies indicate that the particles with PDMAEMA brushes are both pH and temperature responsive.

Synthesis of surface protein-imprinted nanoparticles endowed with reversible physical cross-links.

Researches on protein molecularly imprinted polymers have been challenged by the difficulties in facilitating biomacromolecular transfer, in particular upon the template removal step, and enhancing their recognition performance. Addressing these issues, herein we report synthesis of core­shell structured surface protein-imprinted nanoparticles with reversible physical cross-links formed in the imprinted nanoshells. The imprinted layers over nanoparticle supports are fabricated via aqueous precipitation polymerization (PP) of di(ethylene glycol) methyl ether methacrylate (MEO2MA), a thermo-responsive monomer bearing no strong H-bond donor, and other functional and cross-linking monomers. During polymerization, physical cross-links together with chemical cross-links are in site produced within the imprinted shells based on hydrophobic association among the PMEO2MA, favoring formation of high-quality imprints. While cooled appropriately below the polymerization temperature, these physical cross-links can be dissociated rapidly, thus facilitating removal of the embedded template. For proof of this concept, lysozyme-imprinted nanoparticles were synthesized at 37 °C over the nanoparticles functionalized with carboxylic and vinyl groups. The template removal from the imprinted nanoparticles was readily achieved by washing with a dilute acidic detergent solution at 4 °C. As-prepared imprinted nanoparticles showed greatly higher imprinting factor and specific rebinding than obtained with the same recipe but by solution polymerization (SP). Moreover, such imprinted nanomaterials exhibited satisfactory rebinding selectivity, kinetics and reusability.

Enhanced surface imprinting of lysozyme over a new kind of magnetic chitosan submicrospheres.

Surface protein imprinting over nano- or micron-sized substrates is an effective approach for improving the biomacromolecule mass transfer and rebinding capacity. For achieving high recognition performance, it is necessary to introduce certain functional groups onto the surface of the support materials which can interact with the template protein. Herein, we report a surface protein imprinting approach using a new kind of core-shell magnetic chitosan submicrospheres as the supports. The surface of these magnetic chitosan particles is tethered with uncross-linked chitosan chains, hence bearing plenty of amino and hydroxyl groups, where a large amount of functional ligands can be readily coupled for capturing of the protein template. With lysozyme as a model print protein, the magnetic supports were functionalized with maleic acid and then coated with imprinted polymer layers. The resulting imprinted microspheres show significantly selective rebinding for lysozyme. In particular, they exhibit a specific rebinding capacity about three times higher than achieved with our previous lysozyme-imprinted particles synthesized in similar way but with maleic acid modified silica nanoparticles as the supports. This can be attributed to the much higher template binding capacity to the modified magnetic chitosan submicrospheres. Also, the resultant imprinted particles can be easily collected by a magnet. Therefore, such kind of chitosan submicrospheres may be a versatile carrier for constructing high-capacity and magnetically recyclable surface protein-imprinted particles.

Facile synthesis of hairy core-shell structured magnetic polymer submicrospheres and their adsorption of bovine serum albumin.

Highly magnetic polymer submicrospheres with a hairy core-shell structure were facilely synthesized by combining distillation-precipitation polymerization (DPP) with subsequent surface-initiated atom transfer radical polymerization (SI-ATRP), and then investigated for protein adsorption. A robust polymer shell consisting of poly(divinylbenzene-co-chloromethylstyrene) (P(DVB-co-CMS)) was coated on superparamagnetic submicrometer-sized magnetite colloid nanocrystal clusters (MCNCs) via DPP. With the benzyl chloride groups on the shell as initiator, poly(2-(dimethylamino) ethyl methacrylate) (PDMAEMA) hairs were grafted by SI-ATRP approach. The resulting hairy core-shell structured Fe3O4@ P(DVB-co-CMS)-PDMAEMA microspheres showed pH- and temperature-sensitivity, and high-magnetization. The composite microspheres were further investigated for adsorption of a typical acidic protein, i.e. bovine serum albumin (BSA). They exhibited a high binding capacity up to over 660 mg/g (corresponding to 158 DMAEMA monomer units cooperating for binding one BSA molecule) and could rapidly reach binding equilibrium within 5 min. Moreover, the adsorption of BSA was found to be remarkably dependent on the pH and salt concentration of the protein solutions, and the bound protein could be quantitatively desorbed by washing with a medium with lowered pH or raised salt concentration.

Preparation of lysozyme imprinted magnetic nanoparticles via surface graft copolymerization.

Molecular imprinting as a facile and promising separation technique has received considerable attention because of their high selectivity for target molecules. In this study, we imprinted lysozyme (Lys) on the surface of core-shell magnetic nanoparticles via surface imprinting. The magnetic supports were functionalized with maleic acid and then coated with imprinted polymer layers. The structure and morphology of the resulting magnetic imprinted nanoparticles were characterized by transmission electron microscopy, scanning electron microscope, dynamic light scatting, vibrating sample magnetometer, and thermogravimetric analysis. Binding experiments were carried out to evaluate the properties of magnetic molecularly imprinted polymers (magnetic MIPs) and magnetic non-molecularly imprinted polymers (magnetic NIPs). The protein adsorption results showed that the magnetic MIPs had significant specific recognition toward the template protein and could be easily separated from solution by an external magnetic field. Moreover, the MIPs exhibited fast kinetics for the rebinding of the target protein due to the thin-imprinted layer and showed good reusability by four adsorption-desorption cycles. Therefore, the surface imprinting approach combined with magnetic nanoparticles provided an easy and fast method for the specific recognition of Lys.

Fabrication of Surface Protein-Imprinted Nanoparticles Using a Metal Chelating Monomer via Aqueous Precipitation Polymerization.

Molecular imprinting is a promising way for constructing artificial protein recognition materials, but it has been challenged by difficulties such as restricted biomacromolecule transfer in the cross-linked polymer networks, and reduced template-monomer interactions that are due to the required aqueous media. Herein, we propose a strategy for imprinting of histidine (His)-exposed proteins by combining previous approaches such as surface imprinting over nanostructures, utilization of metal coordination interactions, and adoption of aqueous precipitation polymerization capable of forming reversible physical crosslinks. With lysozyme as a model template bearing His residues, imprinted polymer nanoshells were grafted over vinyl-modified nanoparticles by aqueous precipitation copolymerization of a Cu(2+) chelating monomer with a temperature-responsive monomer carried out at 37 °C, above the volume phase-transition temperature (VPTT) of the final copolymer. The imprinted nanoshells showed significant temperature sensitivity and the template removal could be facilitated by swelling of the imprinted layers at 4 °C, below the VPTT. The resultant core-shell imprinted nanoparticles exhibited strikingly high rebinding selectivity against a variety of nontemplate proteins. An imprinting factor up to 22.7 was achieved, which is among the best values reported for protein imprinting, and a rather high specific binding capacity of 67.3 mg/g was obtained. Moreover, this approach was successfully extended to preliminary imprinting of hemoglobin, another protein with accessible His. Therefore, it may be a versatile method for fabrication of high-performance surface-imprinted nanoparticles toward His-exposed proteins.

Synthesis of surface molecularly imprinted nanoparticles for recognition of lysozyme using a metal coordination monomer.

Molecularly imprinted polymers against proteins are regarded as promising substitutes for natural antibodies, but have been frustrated with the problems including reduced interaction between functional monomers and protein template in the aqueous media required during their synthesis and restricted mass transfer across the resulting crosslinked polymer matrixes. For addressing these issues, herein we proposed a strategy for imprinting of a protein on the surface of nanoparticles using a metal chelating monomer. With lysozyme as a model protein template and Cu(2+) chelating N-(4-vinyl)-benzyl iminodiacetic acid as the coordination monomer along with other monomers, protein imprinted polymer nanoshells were formed over vinyl-modified silica nanoparticles via surface polymerization in high-dilution monomer solution. The feed concentration of the crosslinking monomer was optimized toward achieving the best imprinting effect. Compared with the related imprinted materials reported previously, the resultant core-shell imprinted particles showed greatly faster binding kinetics, elevated rebinding capacity and selectivity. More importantly, noticeably high binding affinity was achieved with an estimated dissociation constant of 4.1 × 10(-8)M which is comparable to that of conventional antibodies.