Pengqi Guo

Preparation of surface molecularly imprinted polymers as the solid-phase extraction sorbents for the specific recognition of penicilloic acid in penicillin

A method coupling SMIP-SPE with high-performance liquid chromatography (HPLC) was established for the detection of trace amounts of PNLA in penicillin. Highly selective surface molecularly imprinted polymers (SMIPs) were prepared and used as solid-phase extraction sorbents for the specific recognition, enrichment, extraction and detection of penicilloic acid (PNLA) in penicillin. The polymers were characterised in terms of their physical and morphological properties by using SEM, FTIR, thermogravimetric analyses, nitrogen adsorption and desorption analyses and elemental analyses. The adsorption properties of the products obtained were studied, including the adsorption of isotherms, kinetics and selectivity. The results demonstrated that SMIPs possess a high adsorption capacity, rapid mass-transfer rate and high selectivity to PNLA when compared with non-imprinted polymers (SNIPs) and bulk molecularly imprinted polymers (MIPs). SMIPs adopted as the sorbents of solid-phase extraction (SMIP-SPE) were used to extract the penicilloic acid from the parent drug, the reusability and stability of which were investigated. The results of the method validation showed that the intra-day and inter-day accuracy were ≥93.2% and ≥90.9%, respectively. The RSD% of repeatability ranged from 0.7% to 6.8%, and that of the intermediate precision ranged from 4.9% to 7.4%. The limit of detection (LOD) and the limit of quantitation (LOQ) were 0.03 mg g−1 and 0.1 mg g−1, respectively. This work provides a promising method for monitoring the allergenic impurity in penicillin and improving the purity of penicillin.

Development of molecular imprinted column-on line-two dimensional liquid chromatography for selective determination of clenbuterol residues in biological samples

A novel method coupling molecular imprinted monolithic column with two-dimensional liquid chromatography was developed and validated for the analysis of clenbuterol in pork liver and swine urine samples. The polymers were characterized by using Fourier transform infrared spectroscopy, nitrogen adsorption desorption analyses, frontal analysis and the adsorption of selectivity. The results indicated that the imprinted columns were well prepared and possessed high selectivity adsorption capacity. Subsequently, the MIMC-2D-LC (molecular imprinted monolithic column-two dimensional liquid chromatography) method was developed for the selective analysis of clenbuterol in practical samples. The accuracy ranged from 94.3% to 99.7% and from 93.7% to 99.6% for liver and urine, respectively. The relative standard deviation (RSD) of repeatability was lower than 8.6% for both analyses. The limit of detections was 16ng·mL(-1) for liver and 25ng·mL(-1) for urine, respectively. Compared with the reported methods, the disturbance of endogenous impurity could be avoided by the 2D-LC method.

Development of molecularly imprinted column-on line-two dimensional liquid chromatography for rapidly and selectively monitoring estradiol in cosmetics.

Nowadays, the illegal use of estradiol in cosmetics has caused a series of events which endangering public health seriously. Therefore, it is imperative to establish a simple, fast and specific method for monitoring the illegal use of estradiol in cosmetics. In current study, we developed a molecular imprinted monolithic column two dimensional liquid chromatography method (MIMC-2D-LC) for rapid and selective determination of estradiol in various cosmetic samples. The best polymerization, morphology, structure property, surface groups, and the adsorption performance of the prepared material were investigated. The MIMC-2D-LC was validated and successfully used for detecting estradiol in cosmetic samples with good selectivity, sensitivity, efficiency and reproducibility. The linear range of the MIMC-2D-LC for estradiol was 0.5-50μgg-1 with the limit of detection of 0.08μgg-1. Finally, six batches of cosmetic samples obtained from local markets were tested by the proposed method. The test results showed that the illegal use of estradiol still existed in the commercially available samples.

Molecularly imprinted polymer cartridges coupled to liquid chromatography for simple and selective analysis of penicilloic acid and penilloic acid in milk by matrix solid-phase dispersion.

A simple, fast and sensitive method for determination of the degradation products of penicillin (penicilloic acid and penilloic acid) in milk samples has been developed by combining selective surface molecularly imprinted matrix solid-phase dispersion and high performance liquid chromatography (SMIPs-MSPD-HPLC). The selected dispersant SMIPs had high affinity for penicilloic acid and penilloic acid in milk matrix and the obtained extract was sufficiently clean for direct injection for HPLC analysis without any interference from the matrix. The proposed SMIPs-MSPD-HPLC method was validated for linearity, precision, accuracy, limit of detection and limit of quantitation. Linearity ranged from 0.04 to 4 μg g(-1) (correlation coefficient r(2) > 0.999). Recoveries of penicilloic acid from milk samples at different spiked levels were between 79.8 and 90.3%, with RSD values within 5.2-7.4%, and the limit of detection and limit of quantitation values were 0.04 and 0.13 μg g(-1), respectively. Recoveries of penilloic acid from milk samples at different spiked levels were between 77.4 and 86.2%, with RSD values within 3.1-6.4%, and the limit of detection and limit of quantitation values were 0.05 and 0.17 μg g(-1), respectively. The developed SMIPs-MSPD-HPLC method was successfully applied to direct determination of penicilloic acid and penilloic acid in milk samples.

A novel surface molecularly imprinted polymer as the solid-phase extraction adsorbent for the selective determination of ampicillin sodium in milk and blood samples☆

Surface molecularly imprinted polymers (SMIPs) for selective adsorption of ampicillin sodium were synthesized using surface molecular imprinting technique with silica gel as a support. The physical and morphological characteristics of the polymers were investigated by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), elemental analysis and nitrogen adsorption–desorption test. The obtained results showed that the SMIPs displayed great adsorption capacity (13.5 μg/mg), high recognition ability (the imprinted factor is 3.2) and good binding kinetics for ampicillin sodium. Finally, as solid phase extraction adsorbents, the SMIPs coupled with HPLC method were validated and applied for the enrichment, purification and determination of ampicillin sodium in real milk and blood samples. The averages of spiked accuracy ranged from 92.1% to 107.6%. The relative standard deviations of intra- and inter-day precisions were less than 4.6%. This study provides a new and promising method for enriching, extracting and determining ampicillin sodium in complex biological samples.

Enrichment of total steroidal saponins from the extracts of Trillium tschonoskii Maxim by macroporous resin and the simultaneous determination of eight steroidal saponins in the final product by HPLC

An effective and simple method was established for the separation and enrichment of steroidal saponins from Trillium tschonoskii Maxim. The adsorption and desorption properties of seven macroporous resins were investigated. Among the tested resins, AB-8 resin showed the best adsorption and desorption capacities. The adsorption of steroidal saponins on AB-8 at 25°C was quite consistent with both the Freundlich isotherm model and the pseudo-second-order kinetics model. By optimizing the dynamic adsorption and desorption parameters, the content of steroidal saponins increased from 5.20% in the crude extracts to 51.93% in the final product, with a recovery yield of 86.67%. Furthermore, by scale-up separation, the concentration and recovery of total steroidal saponins were 43.8 and 85.5%, respectively, which suggested that AB-8 resin had great industrial and pharmaceutical potential because of its high efficiency and cost-effectiveness. In addition, a high-performance liquid chromatography method for the simultaneous determination of eight steroidal saponins was established for the first time, which was employed to qualitatively and quantitatively analyze the final product. Based on the methodological validation results, the high-performance liquid chromatography method can be widely applied to the quality control of steroidal saponins from Trillium tschonoskii Maxim due to its excellent accuracy, stability, and repeatability.

Study of the allergenic benzypenicilloyl–HSA and its specific separation from human plasma by a pre-designed hybrid imprinted membrane

Benzylpenicilloyl/albumin conjugates (BP–HSA) which have lost all antibacterial activity but possess an immunogenic potential were systematically studied by matrix-assisted laser desorption ionization-time of flight-mass spectrometry, polyacrylamide gel electrophoresis and ultraviolet spectrophotometry. The results showed that the conjugation rate was in the range of 8 : 1–18 : 1. The interaction between human serum albumin (HSA) and penicilloic acid (BPA) was firstly studied by using molecular docking. The results showed that at least 8 activity sites existed on HSA for the conjugation of BPA. BP–HSA was imprinted onto a macroporous chitosan/polyvinylpyrrolidone/carbon nanotubes carrier by using surface precipitation polymerization, and a pre-designed hybrid imprinted membrane (CPC-MIM) was obtained to achieve the specific capturing of BP–HSA from human plasma. The morphologies and physical/chemical properties of membranes were systematically characterized by scanning electron microscopy, atomic force microscopy, Fourier translation infrared spectra, differential scanning calorimeter, thermogravimetric analysis and contact angle measurement. The results indicated that CPC-MIM possessed superior properties for the selective adsorption of BP–HSA and it also had a relatively good thermal stability. The adsorption properties of CPC-MIM were evaluated by comparing with other different constituents of membranes. The results revealed that the maximum adsorptive capacity and imprint factor of CPC-MIM were 0.538 μmol cm−3 and 3.3, respectively. Compared with other proteins, CPC-MIM showed a specific adsorption capacity for BP–HSA, and CPC-MIM could selectively capture BP–HSA from human plasma. This study provides a basis for the further research of the allergic mechanism of penicillins, and the generated hybrid imprinted membrane could potentially be an outstanding separation material for the large-scale continuous selective separation of target proteins from a complex matrix.

Preparation and evaluation of a molecularly imprinted sol–gel material as the solid‐phase extraction adsorbents for the specific recognition of cloxacilloic acid in cloxacillin

Highly selective molecularly imprinted polymers on the surface of silica gels were prepared by a sol-gel process and used as solid-phase extraction adsorbents for the specific recognition, enrichment and detection of cloxacilloic acid in cloxacillin. The obtained polymers were characterized by scanning electron microscopy, FTIR spectroscopy, nitrogen adsorption and desorption, elemental analysis and thermogravimetric analysis. The imprinted polymers not only possessed high adsorption capacity (6.5 μg/mg), but also exhibited fast adsorption kinetics (they adsorb 80% of the maximum amount within 20 min) and excellent selectivity (the imprinted factor was 3.6). A method using the imprinted polymers as solid-phase extraction adsorbents coupled with high-performance liquid chromatography was established with good specificity, linearity (r = 0.9962), precision (ranging from 0.5 to 6.7%), accuracy (ranging from 93.9 to 97.7%) and extraction recoveries (ranging from 78.8 to 89.8%). The limits of detection and quantification were 0.07 and 0.25 mg/g, respectively. This work could provide a promising method in the enrichment, extraction and detection of allergenic impurities in the manufacture, storage and application of cloxacillin.

A porous hybrid imprinted membrane for selectively anchoring target proteins from a complex matrix

A novel porous hybrid imprinted membrane (CP/CNT/DA-MIM) was prepared that could selectively anchor and separate target proteins from a complex matrix. CP/CNT/DA-MIM exhibits many of the advantages of molecularly imprinted polymers and membranes, including the high selectivity of MIPs, the lower energy consumption and the ability to continuously separate mixtures via membrane separation. The surface morphologies and physical/chemical properties of the different membranes were investigated using FTIR, XRD, DSC, XPS and SEM. The results showed that the different molecules contained within CP/CNT/DA-MIM were homogeneous; two different sizes of imprinted cavities were observed in CP/CNT/DA-MIM, which facilitate the selective anchoring property. The adsorption capacities, swelling behaviors and mechanical properties of the different constituent membranes were also compared. The results show that the adhesion and nonspecific adsorption properties of the membrane were manifestly reduced through the addition of PVP. The binding capacity and adsorption selectivity of the membrane were apparently improved because of the presence of dopamine. MWCNTs obviously improved the mechanical strength of the membranes. CP/CNT/DA-MIM was successfully applied to separate bovine serum albumin from bovine blood. CP/CNT/DA-MIM is an economical, hydrophilic and ecofriendly membrane and is a promising separation material for the large-scale continuous selective separation of target proteins from complex matrices in commercial applications.

Preparation and characterization of surface molecularly imprinted films coated on multiwall carbon nanotubes for recognition and separation of lysozyme with high binding capacity and selectivity

In this work, a series of facile and efficient molecularly imprinted polymers (MIPs) for the selective recognition and separation of lysozyme were synthesized by combining self-polymerization and nanosized matrix. The imprinted materials containing recognition sites for the lysozyme were formed via using both carboxyl-functionalized multi-walled carbon nanotubes (MWCNTs-COOH) as a support and dopamine (DA) with excellent biocompatibility as a functional monomer. The obtained polymers were characterized and evaluated by using field-emission scanning electron microscopy (FESEM), field-emission transmission electron microscopy (FETEM), nitrogen physisorption experiments, Fourier transform infrared (FT-IR) spectroscopy and thermogravimetric analysis (TGA). The optimum reaction conditions and adsorption performance of the resultant nanomaterials were also investigated. MIPs synthesized by this method exhibited excellent imprinting factor (4.1) and high binding capacity (418 mg g−1) for lysozyme. After six adsorption–desorption cycles, the adsorption capacity of the MIPs was only reduced by 7.4%. In addition, the prepared MIPs were used to separate and condense lysozyme from chicken egg white successfully, which showed potential values in industrial protein purification, basic biomedical research and clinical diagnostics.