Novel electroactive nanotags of Cu(II) functionalized polyethylenimine (PEI)/SiO2 nanoparticles (abbreviated as Cu2+/PEI/SiO2 NPs) were conveniently synthesized using a strong coordination reaction between Cu(II) and the multi-amino groups of PEI. These electroactive nanotags were easily coated on the overoxidized polypyrrole (OPPy) modified Nafion/multi-walled carbon nanotubes (abbreviated as Nafion/MWNTs) electrode surface through Cu-N bonds and strong electrostatic interactions. The Cu2+/PEI/SiO2 NPs@OPPy/MWNTs hybrid nanomaterial was formed without the addition of extra membrane-forming substances. The experimental results demonstrate that the OPPy/MWNTs composite membrane coupled with electrocatalytic Cu(Tris)42+ complexes in tris(hydroxymethyl)aminomethane (Tris)-HCl buffer medium amplified the electrochemical signals of nanotags based on the mutual synergistic effects. As an application, a label-free electrochemical immunosensor for epithelial ovarian cancer biomarker-carbohydrate antigen-125 (CA125) was constructed by covalently immobilizing CA125 antibody onto the hybrid nanomaterial modified electrode. With the increasing concentrations of CA125 antigen, different decreases in the electrochemical signals of the nanotags were observed due to the formation of antigen-antibody immune complexes. The electrochemical immunosensor showed a linear relationship from 0.001 to 500 U·mL−1 for CA125 with a detection limit of 3.4 × 10−4 U·mL−1. In addition, the proposed immunosensor was applied to the determination of CA125 in human serum with satisfactory results.
Ya-Qi Zhao,Zhi-Peng Li,Shi-Chao Dong,Hao Wang,Yi-Mei Zhao,Lin-Yi Dong,Zhen-Yu Zhao,Xian-Hua Wang
The effective method for trypsin purification should be established because trypsin has important economic value. In this work, a novel and simple strategy was proposed for fabricating micron-sized magnetic Fe 3 O 4 @agarose-benzamidine beads (MABB) with benzamidine as a ligand, which can efficiently and selectively capture trypsin. The micro-sized MABB, with clear spherical core-shell structure and average particle size of 6.6 μm, showed excellent suspension ability and magnetic responsiveness in aqueous solution. The adsorption capacity and selectivity of MABB towards target trypsin were significantly better than those of non-target lysozyme. According to the Langmuir equation, the maximum adsorption capacity of MABB for trypsin was 1946 mg g −1 at 25 °C, and the adsorption should be a physical sorption process. Furthermore, the initial adsorption rate and half equilibrium time of MABB toward trypsin were 787.4 mg g −1 min −1 and 0.71 min, respectively. To prove the practicability, MABB-based magnetic solid-phase extraction (MSPE) was proposed, and the related parameters were optimized in detail to improve the purification efficiency. With Tris-HCl buffer (50 mM, 10 mM CaCl 2 , pH 8.0) as extraction buffer, Tris-HCl buffer (50 mM, 100 mM CaCl 2 , pH 8.0) as rinsing buffer, acidic eluent (0.01 M HCl, 0.5 M NaCl, pH 2.0) as eluent buffer and alkaline buffer (1 M Tris-HCl buffer, pH 10.0) as neutralization solution, the MABB-based MSPE was successfully used for trypsin purification from the viscera of grass carp ( Ctenopharyngodon idella ). The molecular weight of purified trypsin was determined as approximate 23 kDa through sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The purified trypsin was highly active from 30 °C to 60 °C, with an optimum temperature of 50 °C, and was tolerant to pH variation, exhibiting 85 % of maximum enzyme activity from pH 7.0 to 10.0. The results demonstrated that the proposed MABB-based MSPE could effectively purify trypsin and ensure the biological activity of purified trypsin. Therefore, we believe that the novel MABB could be applicable for efficient purification of trypsin from complex biological systems.
Hydrogel is a good drug carrier, widely used in the sustained-release aspect of tumor drugs, which can achieve the continuous release of drugs to the tumor sites. In this study, diethylene glycol monomethyl ether methacrylate (MEO2MA) and poly (ethylene glycol) methyl ether methacrylate (OEGMA) are temperature-sensitive monomers. N-Methacryloyl-L-Histidine (Mist) is pH sensitive monomer and ligand for metal coordination bond. The temperature-sensitive monomers and pH sensitive monomer with stereocomplex of modified polylactic acid (HEMA-PLLA30/PDLA30) were mixed, under 2,2’-azobis (2-methylpropionitrile) (AIBN) as radical initiator, polymer was formed by free-radical polymerization. The polymer was then immersed in ZnSO4solution, the imidazole group of Mist monomer forms a tridentate metal coordination bond with Zn2+, temperature/pH double-responsive and physical double-crosslinked hydrogel was finally obtained. Comparing the hydrogen bond hydrogel, hydrogen bond and metal coordination bond double crosslinking hydrogel, metal coordination bond hydrogel, testing thermal stability, viscoelasticity, swelling, and morphology of three hydrogels. In addition, using UV-Visible spectroscopy (UV-Vis) to test the sustained release of the hydrophobic drug doxorubicin hydrochloride (DOX-HCl) in the human tumor environment (37 °C, pH = 5). We found that the temperature/pH double-responsive and physical double-crosslinked hydrogel had the most potential for the sustained drug release.
危险品化学品经营许可证（带存储）