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Combining quantum dots with molecular imprinting techniques, a fluorescent molecularly imprinted membrane (MIM) is prepared by embedding l -cysteine-capped Mn2+-doped ZnS quantum dots (QDs) into molecularly imprinted polymer matrix. This fluorescent MIM is used as biosensor for specific recognition of a target protein (lysozyme). The key point of this approach is that the fluorescent quantum dots embedded into a molecularly imprinted membrane, which enables the optical readout characteristic and high selectivity within a thin hydrogel membrane. When the fluorescent MIM selectively captures the target protein, the electron transfer between the QDs and the target protein will result in the fluorescence quenching of the membrane. And the quenched fluorescence emission intensity was proportional to the concentration of the analytes. The as-prepared membrane was successfully applied to selectively and sensitively detect target proteins without any time-consuming pretreatments. Under optimal conditions, the linear detection of the fluorescence MIM ranged from 1.0 × 10−7 to 1.0 × 10−6 mol L−1 with the detection limit of 10.2 nM. Furthermore, the MIM was applied to determine lysozyme in real samples with recoveries of 93%–103%. Experimental results showed that the fluorescent MIM might serve as a simple and sensitive fluorescent biosensor for detecting target protein in complex biological samples.

Four geminal ionic liquids (GILs), namely, 1,4-bis(1,1′-butyl-3,3′- methylene- imidazolium)-benzene bis[(trifluoromethyl)sulfonyl]imide (BBMIB-NTf2), 1,4- bis(1,1′-butyl-3,3′-methylene-imidazolium)-benzene tetrafluoroborate (BBMIB-BF4), 1,4- bis(1,1′-butyl-3,3′-methylene-imidazolium)-benzene hexafluophosphate (BBMIB-PF6), and 1,4-bis(1,1′-methyl-3,3′-methylene-imidazolium)-benzene bis[(trifluoromethyl) sulfonyl] imide (BMMIB-NTf2), were synthesized. They were statically coated onto the inner walls of fused-silica capillary columns and used as stationary phases for gas chromatography. The evaluation of BBMIB-NTf2, BBMIB-BF4, BBMIB-PF6, and BMMIB-NTf2 as stationary phases is reported here for the first time. These new stationary phases exhibit efficiencies of at least 2.3 × 103 plates per meter. Abraham solvation parameter model was used to evaluate the solvation characteristics. The system constants indicated that the dipolarity/polarizability and the hydrogen-bond basicity play a major role among five mol...

Graphical abstract Schematic 1 Electrochemical determination of human IgG using CuFe2O4 nanospheres molecularly imprinted polymers modified with MoS2@N-GQDs-IL., Highlights • A selective and rapid electrochemical sensing method was developed to determine IgG. • MoS2@N-GQDs-IL with excellent performance was first prepared to modify electrodes. • IgG was successfully determined in the human serum specimens. • This method reveals superior limit of detection and linear concentration range., An advanced molecularly imprinted electrochemical sensor with high sensitivity and selectivity for the detection of Human immunoglobulin G (IgG) was successfully constructed. With acrylamide imprinting systems, surface imprinting on the nanoparticles CuFe2O4 targeted at IgG was employed to prepare molecularly imprinted polymer, which served as recognition element for the electrochemical sensor. Furthermore, the sensor harnessed a molybdenum disulfide (MoS2)@nitrogen doped graphene quantum dots (N-GQDs) with ionic liquid (IL) nanocomposite for signal amplification. Under optimized experimental conditions, the sensor shortened the response time to less than 8 min, and the response was linear at the IgG concentration of 0.1–50 ng·mL−1 with a low detection limit of 0.02 ng·mL−1 (S/N = 3). Our findings suggested that, the sensor exhibited high detectability and long-time stability. The satisfactory results of human serum sample analysis showed that the developed IgG sensor had promising potential clinical applications in detecting IgG content.

Chiral metal-organic cages (MOCs) are a new type of porous materials with unique molecular recognition ability, which have received research attention as a chiral stationary phase (CSP) for gas chromatography (GC). Herein, we report the detailed investigation of a chiral MOC ([Cu12(LPA)12(H2O)12], PA = L-phenylalanine, MOC-PA) as a novel stationary phase for GC separations. The MOC-PA capillary column exhibited a high-resolution performance for a wide range of analytes, including n-alkanes, n-alcohols, esters, aromatic compounds and the Grob mixture, positional isomers and racemates. In particular, MOC-PA coated column displayed good resolution and performance for amino acid derivatives. Moreover, the MOC-PA column showed excellent separation repeatability and reproducibility. The relative standard deviation (RSD) values for the retention times were in the range of 0.16-0.30% for run to run (n = 3), 0.31-0.77% for day-to-day (n = 3), and 3.6-4.7% for column-to-column (n = 3), respectively. The experimental results showed that MOC-PA had great potential as a GC stationary phase.

This paper demonstrated a new method for preparing fluorescent molecularly imprinted polymer (MIP) for specific recognition of a target protein. The MIP-based fluorescent receptor was developed by coating MIP layer on the surface of l-cysteine modified Mn2+-doped ZnS quantum dots (QDs) using the surface molecular imprinting process. These MIP-QDs composites demonstrated fast adsorption kinetics, high stability, and good dispersibility in aqueous media. Since the fluorescence quenching of MIP-QDs composites is proportional to the concentration of the lysozyme, the MIP-based fluorescent receptor was successfully applied to the direct fluorescence quantification of lysozyme without further pretreatment. The MIP-based fluorescent receptor exhibited good selectivity and sensitivity for lysozyme detection. The optimum fluorescence intensity of the MIP-QDs was found to be at pH 6.0, and the linear range of lysozyme was from 0.1 to 2.0 μM with the detection limit of 25.2 nM. Moreover, the proposed fluorescent receptor was satisfactorily applied to the determination of lysozyme in real samples. This study provides a new approach for recognizing and detecting of specific proteins in biological samples.

Protein imprinting is still a challenge due to the low binding kinetics and poor binding selectivity. In this study, a facile method of the preparation of magnetic molecularly imprinted polymers (MIPs) for selective protein separation was reported. Carboxyl group functionalized Fe $$_{3}$$ O $$_{4}$$ nanoparticles (NPs) were synthesized using a solvothermal method. After pre-assembly of caroxyl group functionalized Fe $$_{3}$$ O $$_{4}$$ NPs and template protein lysozyme (Lyz) to form Lyz–Fe $$_{3}$$ O $$_{4}$$ complex, magnetic MIPs were synthesized by a sol–gel process of 3-aminopropyltriethoxylsilane and tetraethyl silicate with Lyz–Fe $$_{3}$$ O $$_{4}$$ complex incorporated. Then Fe $$_{3}$$ O $$_{4}$$ –MIPs particles with magnetic response could be collected by simple crush of bulk polymers. This preparation process avoid the need of high dilution of monomer for anti-agglomeration in the surface imprinting, and large amount of solvent is spared. The morphology and structure property of the prepared magnetic NPs were characterized by transmission electronic microscopy, Fourier transform infrared spectroscopy, and vibrating sample magnetometer. Binding experiments were carried out to evaluate Fe $$_{3}$$ O $$_{4}$$ –MIPs particles’ binding performance and selectivity. And results showed fast binding kinetics, high binding capacity, and favorable specific recognition behavior toward template protein, which is due to the role of carboxyl group functionalized Fe $$_{3}$$ O $$_{4}$$ NPs as both magnetic source and importantly as co-functional monomer incorporated in the polysiloxane imprinting system. Real egg white sample tests demonstrate good separation effect. This report provides a possibility of the selective separation of protein in complex matrix.

This paper demonstrates a new strategy for producing fluorescent molecularly imprinted membranes (MIMs) for specific recognition of a target molecule. 3-Mercaptopropyltriethoxysilane-capped quantum dots (QDs) were first incorporated into hydrogel membranes of acrylamide and N,N′-methylenediacrylamide to fabricate QD-entrapped molecularly imprinted membranes. The fluorescence intensity of the QDs entrapped in the hydrogel membrane was quenched after being activated by the electron transfer between the QDs and bisphenol A. The quenched fluorescence emission intensity was proportional to the concentration of bisphenol A. Herein, trace levels of bisphenol A were rapidly detected through the quenching of the fluorescence intensity of the QD-entrapped membranes without any preconcentration processes. The linear detection ranges from 0.005 μM to 0.1 μM and with recoveries of 92–108% for bisphenol A. The QD-entrapped hydrogel membranes also showed quite good selectivity for the detection of bisphenol A.

In this paper, molecularly imprinted photonic crystal hydrogels (MIPHs) were prepared by combining photonic crystals with molecular imprinting technology. The MIPHs were used as optical sensors for the rapid reorganization and detection of melamine in water samples. In this experiment, melamine was used as a template molecule, and the MIPHs were prepared by successive self-assembly, polymerization, and template removal. Morphological characterization by scanning electron microscopy (SEM) showed that the MIPHs possessed a highly ordered three-dimensional (3D) macroporous structure containing nanocavities. As optical sensors, the MIPHs were able to transform molecular recognition events into fluorescence signals for rapid and highly selective and sensitive recognition of the target molecule. Based on color changes of the MIPHs, the target analyte could be quickly identified by analysis with image software or even by observation with the naked eye. Under optimal conditions, the Bragg diffraction peak of the MIPHs shifted from 563 to 608 nm when exposed to melamine in mass concentrations of 10-11 to 10-6mol/L, whereas there were no obvious peak shifts when it was exposed to structural analogues of melamine.

In this work, a novel polymer membrane molecularly imprinted on a silanized glass substrate was prepared. Lysozyme was chosen as the template protein, and acrylamide and N,N'-methylenebisacrylamide were used as the functional monomer and crosslinking agent, respectively. The adsorption equilibrium time, maximum adsorption capacity, specific recognition ability, reusability, and application of the prepared lysozyme-imprinted polymer membrane were investigated experimentally. The prepared polymer membrane exhibited special recognition ability and could quickly adsorb lysozyme. Under optimal conditions, the adsorption equilibrium time of the prepared polymer membrane for lysozyme was 5 min, and the adsorption behavior conformed to the Langmuir adsorption model; the theoretical maximum adsorption capacity was 42.5 mg/g, and the adsorption capacity for an egg sample was 30 mg/g. Additionally, the polymer membrane showed a high selectivity toward the template protein, lysozyme, and exhibited no obvious adsorption of several interfering proteins; the imprinting factor was 3.0. The maximum adsorption capacity of the polymer membrane decreased by 5% after being reused five times. The polymer membrane was used for the adsorption of lysozyme in samples, and good results were obtained. This strategy has potential for the separation and enrichment of target proteins in complex biological samples.

Saliva protein separation by one-step aqueous two-phase extraction (ATPE) in the system of 15% (mass ratio if not specified) PEG-4000/8% NaH2PO4 was presented. The proteins extracted from the top and bottom phases were separated and characterized by high performance liquid chromatography (HPLC) respectively. Under the optimized gradient elution procedure, more saliva protein peaks in the two phases were shown. Saliva protein peaks in 50 min gradient were divided into ten specific groups which were classified into six sections based on the protein distribution in the top and bottom phases. Then, the top or bottom phase was performed the second step ATPE. Possible reasons for protein partition and retention difference are discussed briefly. Results show that some proteins can be separated completely in one-step ATPE, while some can be separated in the following two-step ATPE. The combination of two steps ATPE and HPLC provides a new way to achieve selective separation.

Poly(methyl methacrylate) (PMMA), poly(diallyl phthalate) (PDAP) and nine poly(MMA—DAP) standard samples whose compositions were known were investigated by means of pyrolysis capillary gas chromatography(Py—CGC) and their pyrolysis products were identified by pyrolysis capillary gas chromatography—mass spectrometry(Py—CGC/MS). The relationship between monomer feed ratio in copolymer and quantity of pyrolysates was drawn in a standard working curve. On these bases, the structure and composition of 14 cutting plates of a poly(MMA—DAP) GRIN material polymerized by a vapor transfer diffusion technique were analyzed by Py—CGC.

Liposomes have very similar structure to cell plasma membranes. Using liposomes as stationary phase in liquid chromatography (LC) or micellar electrokinetic chromatography (MEKC) has been demonstrated to be a good, dynamic method for the study of the interaction between cell membranes and important biomolecules. There has been no report on integrating plasma membrane proteins with phospholipids as pseudo-stationary phase in MEKC. In this paper, a novel mode of capillary electrophoresis (CE) is developed, that is, protein-liposome conjugate. This protein-liposome biomimetic membrane is demonstrated for the first time to be applicable as pseudo-stationary phase in MEKC. The protein is able to significantly improve chromatographic performance and stability. The experimental phenomena are further confirmed in terms of specific capacity factors and free binding energy. This new CE mode is used to investigate the interaction between dopamine transporter and dopamine-nomifensine.

In this paper, immobilized artificial membrane (IAM) was selected as the model biomembrane, and packed into capillary column as stationary phase of liquid chromatography to screen the proteins having strong interaction with biomembrane rapidly. The affinity between IAM and ten common proteins (pepsin, bovine serum albumin, casein, transferring, myosin, insulin, hemoglobin, cytochrome C, trypsin, lysozyme), whose pI ranged from 2.0-11.5, were analyzed in different pH mobile phase including acidic, neutral and alkaline buffer. The optimized condition was obtained for the affinity of IAM and proteins. The proteins having strong affinity with IAM were screened out under each pH mobile phase. It can provide the experimental foundation for proteins to be immobilized onto biomembrane to study the membrane related interaction, separation, protein bioactivity, and drug screening and so on.

A new fluorescence imaging method was used for the characterization of the immobilized pH gradient formed in capillary, which was based on charge carried quantum dots (QDs). It was found that the positive charged QDs were concentrated in the same positive region in capillary after CIEF, no matter which terminal of the capillary was used for injection. Furthermore, the formation of the pH gradient and their effect in the practical separation was tested by BSA enrichment experiment, which showing that the sensitivity of detection of BSA was improved remarkably compared with capillary zone electrophoresis (CZE).