Imprinting Layer Research Articles

Quantum-dots-encoded-microbeads based molecularly imprinted polymer

Quantum dots encoded microbeads have various advantages such as large surface area, superb optical properties and the ability of multiplexing. Molecularly imprinted polymer that can mimic the natural recognition entities has high affinity and selectivity for the specific analyte. Here, the concept of utilizing the quantum dots encoded microbeads as the supporting material and the polydopamine as the functional monomer to form the core-shell molecular imprinted polymer was proposed for the first time. The resulted imprinted polymer can provide various merits: polymerization can complete in aqueous environment; fabrication procedure is facile and universal; the obvious economic advantage; the thickness of the imprinting layer is highly controllable; polydopamine coating can improve the biocompatibility of the quantum dot encoded microbeads. The rabbit IgG binding and flow cytometer experiment result showed the distinct advantages of this strategy: cost-saving, facile and fast preparation procedure. Most importantly, the ability for the multichannel detection, which makes the imprinted polydopamine modified encoded-beads very attractive in protein pre-concentration, recognition, separation and biosensing.

Novel polydopamine imprinting layers coated magnetic carbon nanotubes for specific separation of lysozyme from egg white

Novel core–shell nanocomposites, consisting of magnetic carbon nanotubes (MCNTs) core surrounded by a thin polydopamine (PDA) imprinting shell for specific recognition of lysozyme (Lyz), were fabricated for the first time. The obtained products were characterized and the results showed that the PDA layer was successfully attached onto the surface of MCNTs and the corresponding thickness of imprinting layer was just about 10nm which could enable the template access the recognition cavities easily. The polymerization conditions and adsorption performance of the resultant nanomaterials were investigated in detail. The results indicated that the obtained imprinted polymers showed fast kinetic and high affinity towards Lyz and could be used to specifically separate Lyz from real egg white. In addition, the prepared materials had excellent stability and no obvious deterioration after five adsorption–regeneration cycles. Easy preparation, rapid separation, high binding capacity, and satisfactory selectivity for the template protein make this polymer attractive in biotechnology and biosensors.

Selective removal of 2,4-dichlorophenol in aqueous solutions by nanoparticles modified yeast using miniemulsion imprinting polymerization

This research reports a surface molecularly imprinted polymers (SMIPs) which is synthesized by miniemulsion polymerization based on yeast as substrate material. Then, the obtained SMIPs were characterized by several techniques including Fourier transmission infrared spectrometry (FT-IR), scanning electron microscope (SEM), transmission electron microscope (TEM), thermogravimetric analysis (TGA) and elemental analysis. The results demonstrated that the obtained elliptical-shaped molecular imprinting polymer was coated with thickness imprinting layer. Then, SMIPs were used as sorbents to selective removal of 2,4-dichlorophenol (2,4-DCP) from aqueous solutions. Batch mode of binding experiments was carried out to determine the equilibrium isotherm, kinetics, regeneration and selectivity recognition of SMIPs. The results indicated that the selective adsorption behaviors of SMIPs were well described by the Langmuir isotherm model and the pseudo-second-order kinetics model. The SMIPs exhibited outstanding specific recognition capacity for 2,4-DCP (29.25mgg−1 at 298K). SMIPs also possessed excellent selective recognition for 2,4-DCP in the presence of other competitive compounds (such as 2,4,6-TCP, 3-CP and 2,6-DCP). Finally, the SMIPs were successfully adopted to the selective adsorption of 2,4-DCP from the environmental samples.

Preparation of Molecularly Imprinted Regenerated Cellulose Composite Membranes by Surface-Initiated Atom Transfer Radical Polymerization Method for Selective Recognition of Lysozyme

Novel types of polymeric membranes containing molecular recognition sites for selective recognition of lysozyme (Lyz) have been prepared using a surface-initiated atom transfer radical polymerization approach. The surface compositions of the regenerated cellulose (RC) membranes before and after polymerization were characterized by X-ray photoelectron spectroscopy analysis, which demonstrated that the molecular imprinting layer was successfully fabricated onto the surface of RC membranes. The selective recognition of Lyz molecularly imprinted membranes (Lyz–MIMs) for Lyz was evaluated by protein adsorption penetration tests. It was found that Lyz–MIMs have excellent adsorption capacity and specific recognition for Lyz adsorption from aqueous solutions. In the presence of competitive substances, a separation factor of 23.08 was achieved. The molecularly imprinted RC composite membrane is promising for separation and purification of specific protein compositions in biosamples. In addition, it may have good p...

Synthesis of porous molecularly imprinted polymers for selective adsorption of glutathione

An effective approach overcome the classical deficiencies of biomolecules molecularly imprinted polymers (MIPs), that is, low binding capacity and slow mass transfer rate, is proposed. With glutathione (GSH) as target molecule, porous imprinted layers were fabricated according to our newly developed method the introduction of a mixture of acetontrile and dimethylsulfoxide as porogen in surface-initiated polymerization systems. The resultant MIPs particles exhibited a large surface area could remarkably improve the imprinting effect in relation to a significantly increased imprinting factor and mass transfer rate, compared to the MIPs prepared by using aqueous solution as solvent. The batch static binding tests were carried out to evaluate the adsorption kinetics, adsorption isotherms and selective recognition of the MIPs particles. The binding behavior followed the pseudo-second order kinetic model, revealing that the process was chemically carried out. Two binding isotherm models were applied to analyze equilibrium data, obtaining the best description by Langmuir isotherm model. In addition, the selective of separation and extraction of GSH from a mixture of GSH and its structural analogs could be achieved on the MIPs solid-phase extraction cartridge, indicating that the possibility for the separation and enrichment of the template from complicated matrices.

Preparation and evaluation of polydopamine imprinting layer coated multi-walled carbon nanotubes for the determination of testosterone in prostate cancer LNcap cells

A novel type of core–shell imprinted nanocomposite was synthesized for selective extraction and detection of testosterone (TSTO) in prostate cancer cell samples.

Thermal-responsive ion-imprinted polymer based on magnetic mesoporous silica SBA-15 for selective removal of Sr(II) from aqueous solution

Highly thermal-responsive magnetic Sr(II)-imprinted polymer (Sr(II)-TMIIP) was successfully synthesized as a potential effective adsorbent for selective removal of Sr(II) in aquatic environments. First, magnetic polyethyleneimine-loaded mesoporous SBA-15 (Fe3O4@PEI-SBA-15) was prepared via a simple polymer-mediated self-assembly method. Then, the surface of Fe3O4@PEI-SBA-15 was endowed with reactive vinyl groups through modification with 3-(methacryloyloxy)propyl trimethoxysilane (MPS). With the aid of vinyl groups, free radical polymerization of N-isopropylacrylamide (NIPAM), methacrylic acid (MAA), and N,N′-methylenebisacrylamide (BIS) in the presence of Sr(II) was performed with 2,2′-azobisisobutyronitrile (AIBN) as initiator, which provided a desired imprinted layer coating onto Fe3O4@PEI-SBA-15. The as-prepared Sr(II)-TMIIP was characterized by Fourier transmission infrared spectra (FT-IR), X-ray diffractometer (XRD), thermogravimetric analysis (TGA), scanning electron microscope (SEM), transmission electron microscope (TEM), vibrating sample magnetometer (VSM), UV, and N2 adsorption–desorption techniques. The results showed that the Sr(II)-TMIIP exhibited thermal stability, temperature and magnetic sensitivity (M s = 10.34 emu/g), and ordered mesoporous structure. Batch mode adsorption studies were conducted to investigate the specific binding kinetics, adsorption equilibrium, and selective recognition ability of Sr(II)-TMIIP. Adsorption equilibrium experiments showed that the adsorption amount strongly depended on temperature and reached a maximum around the lower critical solution temperature (LCST). Regeneration experiments indicated that repeated adsorption and desorption by temperature swings were possible. Compared with the nonimprinted polymer (NIP), the Sr(II)-TMIIP had good temperature response and excellent selectivity and reusability, making it possible in applying for Sr(II) separation and controlled release.

An epitope imprinting method on the surface of magnetic nanoparticles for specific recognition of bovine serum album.

In this study, we reported an epitope imprinting method on the surface of core-shell magnetic nanoparticles (NPs) for the recognition of target bovine serum album (BSA). The epitope was selected as the template molecule from the nonapeptide of surface-exposed C-terminus of BSA. The core-shell magnetic epitope molecularly imprinted polymers (Fe3O4@EMIPs) exhibited a specific capture activity for the corresponding target protein, BSA. The magnetic NPs made it easy to separate the imprinted material from solution by an external magnetic field, and the thin imprinted layer presented fast kinetics for the rebinding of the target protein. Moreover, the Fe3O4@EMIPs could separate BSA from the bovine blood sample. The epitope imprinting approach combined with magnetic NPs provided an easy and fast method for the specific recognition of BSA.

Fast separation and determination of erythromycin with magnetic imprinted solid extraction coupled with high performance liquid chromatography

In this paper a novel composite imprinted material based on poly(methyl methacrylate) (PMMA) coated magnetic multi-walled carbon nanotubes was successfully synthesized using erythromycin as the template and methacrylic acid as the functional monomer. The magnetic carbon nanotube molecularly imprinted polymers (mag-MWCNTs-MIPs) were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and vibrating sample magnetometery (VSM) in detail. The results showed that a magnetic imprinted layer was coated steadily on the surface of the multi-walled carbon nanotubes. Experiments of adsorption dynamics, static adsorption and selective recognition were conducted to evaluate the adsorption performance. The results showed that the mag-MWCNTs-MIPs displayed rapid dynamic adsorption toward erythromycin, which only needed 30 min to achieve adsorption equilibrium with a maximum adsorption capacity of 31.07 mg g−1. The mag-MWCNTs-MIPs were applied, coupled with high performance liquid chromatography (HPLC), to quickly enrich and detect erythromycin from fish tissue samples with recoveries of 82.7–88.5%. The mag-MWCNTs-MIPs can not only be collected and separated quickly and easily by an external magnet, but also have outstanding mechanical properties and specific recognition toward erythromycin.

Affinity-tunable specific recognition of glycoproteins via boronate affinity-based controllable oriented surface imprinting

The molecular imprinting of proteins is of great importance but remains a challenge. Particularly, efficient, universal and facile approaches for protein imprinting are limited. Here we report a new general approach, boronate affinity-based controllable oriented surface imprinting, for the efficient and facile imprinting of glycoproteins. A glycoprotein template was first covalently anchored onto the surface of a boronic acid-functionalized substrate by boronate affinity binding. The substrate surface was then deposited with a thickness-controllable imprinting coating generated by in-water self-copolymerization of dopamine and m-aminophenylboronic acid (APBA). After removal of the template with an acidic solution, 3D cavities complementary to the molecular shape of the template were formed in the imprinting layer. The imprinting layer was hydrophilic and showed limited residual boronic acid, thus non-specific binding was avoided. The approach has significant advantages, including high specificity, high imprinting efficiency, and widely applicable substrates (from 2D to 3D, from regular size to nanoscale). Uniquely, the prepared molecularly imprinted polymers can rebind the templates in dual modes: a high affinity mode (boronate affinity interaction is on) and a low affinity mode (boronate affinity interaction is off), and the overall binding strength can be tuned by adjusting the surrounding pH. Such an affinity-tunable dual-mode binding mechanism enables the binding strength to be adjusted while keeping the specificity, which allows for wider applications, and also sheds new light on the role of affinity-determining factors in molecular imprinting.

Fabrication and evaluation of temperature responsive molecularly imprinted sorbents based on surface of yeast via surface-initiated AGET ATRP

Temperature responsive molecularly imprinted polymers (T-MIPs) were prepared based on the surface of yeast by electron transfer atom transfer radical polymerization (AGET ATRP). The as-prepared T-MIPs were charcterized by FT-IR, SEM, TGA and elemental analysis, which indicated that T-MIPs exhibited thermal stability and composed of temperature responsive imprinted layer. Then T-MIPs were evaluated as sorbents to selectively recognise and release cefalexin (CFX) molecules. The results suggested binding properties of T-MIPs were related to the testing temperature. The maximum adsorption capacity of T-MIPs at 303K was 59.4mgg−1, and the maximum release proportion for T-MIPs at 293K in water for 24h was 71.08%. The selective recognition experiments demonstrated high affinity and selectivity of T-MIPs towards CFX over competitive compounds, and the specific recognition of binding sites may be based on the distinct size, structure and functional group to the template molecules.

Preparation and characterization of bovine serum albumin surface-imprinted thermosensitive magnetic polymer microsphere and its application for protein recognition

A novel bovine serum albumin surface-imprinted thermosensitive magnetic composite microsphere was successfully prepared by the surface grafting copolymerization method in the presence of temperature-sensitive monomer N-isopropylacrylamide (NIPAM), functional monomer methacrylic acid (MAA) and cross-linking agent N,N′-methylenebisacrylamide (MBA). The structure and component of the thermosensitive magnetic molecularly imprinted microsphere were investigated by transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), vibrating sample magnetometer (VSM) and thermogravimetric analysis (TGA). The results of thermosensitivity, adsorption capacity, selectivity and reusability showed the formation of a thermosensitivity grafting polymer layer P(NIPAM–MAA–MBA) on the surface of Fe3O4@SiO2 and the good adsorption capacity and specific recognition for template protein. When the adsorption temperature was higher than the lower critical solution temperature (LCST) of poly(N-isopropylacrylamide) (PNIPAM), shape memory effect of imprinted cavities would be more effective. In other words, it was more conducive to capture template molecules under this condition and the imprinting factor would be higher. On the other hand, when the desorption temperature was lower than LCST of PNIPAM, the decrease of shape memory effect between imprinted cavities and template molecules would facilitate the release of template molecules from the imprinted cavities. Based on this property, the adsorption and desorption of template molecules could be regulated by system temperature indirectly which benefited from the existence of thermosensitivity imprinting layer.

Removal of cefalexin using yeast surface‐imprinted polymer prepared by atom transfer radical polymerization

The first use of yeast as a support in the molecular imprinting field combined with atom transfer radical polymerization was described. Then, the as-prepared molecularly imprinted polymers were characterized by Fourier transmission infrared spectrometry, scanning electron microscope, thermogravimetric analysis, and elemental analysis. The obtained imprinted polymers demonstrated elliptical-shaped particles with the thickness of imprinting layer of 0.63 μm. The batch mode experiments were adopted to investigate the adsorption equilibrium, kinetics, and selectivity. The kinetic properties of imprinted polymers were well described by the pseudo-second-order kinetic equation, indicating the chemical process was the rate-limiting step for the adsorption of cefalexin (CFX). The equilibrium data were well fitted by the Freundlich isotherm, and the multimolecular layers adsorption capacity of imprinted polymers was 34.07 mg g(-1) at 298 K. The selectivity analysis suggested that the imprinted polymers exhibited excellent selective recognition for CFX in the presence of other compounds with related structure. Finally, the analytical method based on the imprinted polymers extraction coupled with high-performance liquid chromatograph was successfully used for CFX analysis in spiked pork and water samples.

Cholesterol Detection by Self-Assembled Dodecyl Thiol Layers Extracted Cholesterol on the Ce-Sb Codoped SnO<sub>2</sub> Film Electrodes

Cerium (Ce) and antimony (Sb) codoped tin dioxide (SnO2) films (Ce:Sb:Sn=2:3:95 molar ratio) have been prepared on the surface of titanium (Ti) substrate by sol-gel method. A self-assembled layer (SAL) of dodecyl thiol with cholesterol was formed on the surface of Ce-Sb codoped SnO2films/Ti electrode. The SAL was then used with the cholesterol as the template forming the molecular imprinting layer. The extraction of cholesterol has resulted in formation of sites in the layer of dodecyl thiol which could have been used as channels for the ferro-ferric cyanide coupled redox reaction to quantify recombining cholesterol on the sites. This sensor prototype could detect cholesterol concentrations between 40 and 60 μM. X-ray diffraction (XRD) and scanning electron microscopy (SEM) have been used to analyze the structure and morphology of the samples.

Switched recognition and release ability of temperature responsive molecularly imprinted polymers based on magnetic halloysite nanotubes

CoFe2O4/halloysite nanotube magnetic composites (MHNTs) were firstly achieved via a wet impregnation technique, and then a thermal polymerization under (NH4)2S2O8 chain initiation in water was employed to obtain methacrylic acid-functionalized MHNTs (MAA-MHNTs). By decorating the MAA-MHNTs with the temperature responsive monomer N-isopropylacrylamide (NIPAM), a novel temperature responsive molecularly imprinted material based on the obtained NIPAM-MHNTs (TMMIPs) was synthesized by a surface imprinting technique. The results of characterization indicated that the TMMIPs exhibited magnetic sensitivity (Ms = 1.758 emu g−1), magnetic stability (in the pH range of 2.0–8.0), thermal stability (especially below 200 °C) and contained a temperature responsive imprinted layer (the lower critical solution temperature was 33.96 °C). Then the TMMIPs were applied to switched recognition and release of 2,4,5-trichlorophenol molecules (5-TCP) by changing the medium temperature. TMMIPs showed outstanding recognition ability towards the imprinted species under high temperature conditions (such as 60 °C), due to the loss of hydration and a collapsed state of inter-poly(N-isopropylacrylamide), which resulted in the formation of a specific structure between 5-TCP and the polymer network. In contrast, at relatively low temperatures (such as 20 °C), the captured 5-TCP was released from the swelled TMMIPs, which resulted from increasing the distance between 5-TCP and the polymer network. The selective analysis demonstrated the high affinity and selectivity of TMMIPs towards 5-TCP over competitive phenolic compounds, and the specific recognition of binding sites may be based on the distinct size, structure and functional groups of the template molecules.

PREPARATION OF URSOLIC ACID IMPRINTED POLYMERS BASED ON MULTI-WALLED CARBON NANOTUBES AND THEIR APPLICATION IN SOLID PHASE EXTRACTION

A novel surface molecularly imprinted polymer was synthesized using poly(vinyl alcohol) modified multi-walled carbon nanotubes(MWCNTs) as supporting matrix,ursolic acid(UA) as the template molecule,methacrylic acid(MAA) as the functional monomer and ethylene glycol dimethacrylate(EGDMA) as the cross-linking agent.Effect of different molar ratios of the functional monomer to the template on the performance of the synthesized MWCNTs-MIPs was discussed and the results showed that the optimum ratio was 4∶1.The multi-walled carbon nanotubes-molecularly imprinted polymers(MWCNTs-MIPs) were characterized by Fourier transform infrared spectroscopy(FTIR) and scanning electron microscopy(SEM).The results showed that a stable imprinted layer was grafted on the MWCNTs surface successfully.The adsorption properties were demonstrated by static adsorption and adsorption kinetic experiments.The results demonstrated that the MWCNTs-MIPs had specific selectivity for UA,yielding a maximum adsorption capacity of 53.1 μmol/g and the equilibrium time took about 60 min.Solid phase extraction condition was optimized,and the optimal condition was washing with 100% methanol and eluting with 10% acetic acid methanol solution.The solid-phase extraction column packed with MWCNTs-MIPs could be applied to separate ursolic acid(UA) from similar structure oleanolic acid(OA).

Thin layer molecularly imprinted composite membranes for selective separation of erythromycin from water

Molecularly imprinted composite membranes for selective binding of erythromycin were synthesized by UV initiated photo-copolymerization using polysulfone ultrafiltration (PSF) membranes as porous supports. The thin imprinted layers deposited on the surface of the support membranes were formed by copolymerization of acrylic acid (AA) as functional monomer and ethylene glycol dimethacrylate (EGDMA) as cross-linker in the presence of erythromycin as template molecule in acetonitrile solution. Fourier transform infrared spectroscopy (FT-IR) was used to study the binding mechanism between the imprinted sites and the template. Scanning electron microscope (SEM) was utilized to visualize surface and cross-sections of membranes to gain better understanding in the analysis of imprinted layers deposited on PSF support membranes. The modification degrees for imprinted and nonimprinted membranes are 2.04 and 2.15 mg/cm2, respectively. Static equilibrium binding and recognition properties of the imprinted and nonimprinted membranes to erythromycin (EM) and its analogue roxithromycin (RM) in aqueous system were tested. The results showed that saturated binding capacity of imprinted membranes to erythromycin was about 0.185 mg/cm2, nearly eight times that of nonimprinted ones, and the selectivity factor of αEM/RM was 3.24. The results of this study implied that the synthesized molecularly imprinted composite membranes could be used as selective separation materials for erythromycin enrichment from water.

Sub-20-nm Alignment in Nanoimprint Lithography Using Moiré Fringe

Accurate multi-level overlay capability for nanoimprint lithography (NIL) is essential to integrated circuit manufacturing and other multilayer imprint applications. Using the "beat" grating image (Moiré fringe) generated by overlaying two sets of gratings that have slightly different periods, we obtained an alignment signal with a sensitivity better than 10 nm in nanoimprint lithography. The alignment signal is, as expected, independent of the size of the gap between the wafer and the imprint mold. We achieved a single-point overlay accuracy (error distribution) of sub-20 nm between the first and second imprinted layers by using two sets of Moiré fringes. With higher precision nanopositioning stages, better single-point alignment accuracy is expected. Furthermore, we achieved sub-150 nm alignment over an area of 1 sq in and sub-250 nm over the entire area of a 4 in wafer using simple low-resolution stages without temperature control or wafer-mold mismatch compensation. With better stages, precision temperature control, and wafer-mold mismatch compensation, we believe that much higher overlay alignment accuracy over large areas (either in a 1 sq in die or a full wafer) is feasible.

Development of a molecular imprinting thick film electrochemical sensor for cholesterol detection

A combined molecular imprinting and thick film electrochemical sensor for cholesterol concentration detection had been developed. The ferro-ferric cyanide coupled redox reaction was used as the means to quantify the cholesterol presented in the test medium. This electrochemical sensor employed a modified gold working electrode, a platinum counter electrode and an Ag/AgCl reference electrode. The alkanethiol was used to form the self-assembled monolayer (SAM) on the gold working electrode. The SAM was then used with the cholesterol as the template forming the molecular imprinting layer. This sensor prototype could detect cholesterol concentrations between 66 and 700 nM and only a 1 μL of the sample volume was required.

Sensors based on fingerprints of neutral and ionic analytes in polymeric materials

In this paper chemically sensitive layers in combination with universally applicable mass-sensitive devices are suggested for the development of integrated systems for multicomponent analyses of liquids. Completely reversible solid-phase extraction for the detection of ions by sol–gel phases are possible. The layers, applied to the quartz microbalance (QMB) in a one-step process, show excellent sensitivity and do not suffer from bleeding effects. For the measurement of polycyclic aromatic hydrocarbons (PAHs) in water, a new concept of generating selectivity is presented by the use of double imprinted layers, which allows to tune additional parameters such as accessibility to the bulk. By different combinations of template molecules every desired PAH selectivity pattern can be generated.