Biomedical subjects

Yunhua Gao

Publications and source records attributed to Yunhua Gao.

7 recordsLinked to original sources

PubMed2005

An artificial aspartic proteinase system.

A series of aza crown ether derivatives with or without carboxyl groups in their side arms were synthesized and the former showed deacylation activities toward amino acid p-nitrophenyl ester hydrohalides. Substrate-selective phenomena were also observed. The relationship between the structures and deacylation activities of corresponding compounds suggested a nucleophilic catalytic mechanism. The results partially simulate some aspartic proteinases in the case of catalytic mechanism and are also useful for us to understand the detailed catalytic process of aspartic proteinases.

Aspartic Acid Endopeptidases↗

PubMed2005

Magnetically actuated micromixing on an array-pattern microfluidic chip for immunoassay of human thyrotropin.

A novel array-pattern ring microfluidic chip has been designed and fabricated with ITO glass, and a low-cost, easy-to-use active magnetic mixer is developed. The mixer consists of externally driven magnetic stir plates and ferromagnetic microneedles as active mobile stirrers in the microchannel. Mixing performance in the microfluidic chip has been experimentally characterized by chemiluminescence immunoassay of human thyrotropin (TSH) and compared with tube-based chemiluminescence immunoassay. The mixing method proposed in this study can be readily applied to integrated microfluidic systems, such as micro-total-analysis systems, lab-on-a-chip, and so on.

Equipment Design↗

PubMed2005

[Immobilization of von Willebrand factor antibody on solid host membranes].

This study aimed at immobilizing the antibodies on the surfaces of the solid host membranes in order to improve the property of the biomaterial. The von Willebrand factor (vWf) antibodies were immobilized on the surface of Bombyx mori silk fibroin and PLA (Poly Lactic Acid) membrane by NH3 plasma treatment followed by covalent cross-linking reaction. The immobilization efficiency was evaluated by two methods including the antibody surplus and enzyme-linked immunosorbent assay (ELISA). The in vitro antithrombogenicity representing the activity of immobilized vWf antibody was determined by the method of Activated Partial Thromboplastin Time (APTT), Prothrombin Time (PT) and Thrombin Time (TT) test. The results demonstrate that the vWf antibodies are immobilized on silk fibroin and PLA membranes in an efficient way with the efficiency of antibody surplus up to 23.88% and ELISA reaction is positive. APTT and TT exceeded the upper limits distinctly, but the value of PT did not change noticeably. The in vitro antithrombogenicity represented the is activity-retaining form of antibodies. These results extend the application of antibody immobilization technique and provide a new idea about the design of biomaterials relating to the coagulation factors.

Antibodies↗

PubMed2004

Vacuum-assisted thermal bonding of plastic capillary electrophoresis microchip imprinted with stainless steel template.

An improved fabrication of poly(methyl methacrylate) (PMMA)-based capillary electrophoresis microchips has been demonstrated. The microchannel structures on PMMA substrates were generated by one-step hot embossing procedure using a stainless steel template. Hundreds of patterned PMMA substrates have been successfully obtained using the single metal template. Sequent microchannel enclosure with high yield up to 90% was accomplished by a vacuum-assisted thermal bonding method. The results of profilometric scanning of separated substrates showed the dimensions of the channels were well preserved during the bonding process. Finally, analytical functionalities of these PMMA microchips were demonstrated by performing fast electrophoretic separations and high sensitive end-column amperometric detections of dopamine and catechol. The entire fabrication methodology may also be useful for preparation of other thermoplastic microfluidic systems.

Electrophoresis, Capillary↗

PubMed2004

Purification and characterization of an extracellular b-glucosidase with high transglucosylation activity and stability from Aspergillus niger No. 5.1.

An extracellular beta-glucosidase was extracted from the culture filtrate of Aspergillus niger No. 5.1 and purified to homogeneity by using ammonium sulfate precipitation, Chitopearl-DEAE chromatography, and Sephadex G-100 chromatography. The specific activity of the enzyme was enriched 6.33-fold, with a recovery of 11.67%. The enzyme was a monomer and the molecular mass was 67.5 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis and 66.5 kDa by gel-filtration chromatography. The enzyme had optimum activity at pH 6.0 and 60 degrees C and was stable over the pH range of 3.0-9.0. It showed specificity of hydrolysis for p-nitrophenyl-beta-D-glucoside and cellobiose. The Km and Vmax values of the enzyme for cellobiose and salicin were 5.34 mM, 2.57 micromol/(mL.s), and 3.09 mM, 1.34 micromol/(mL.s), respectively. Both amino acid composition and N-terminal amino acid sequence of the enzyme were determined, which provides useful information for cloning of this enzyme.

Amino Acid Sequence↗

PubMed2003

Fabrication and characterization of poly(methyl methacrylate) microchannels by in situ polymerization with a novel metal template.

A stainless steel template for the fabrication of plastic microfluidic devices has been developed by photolithography and chemical etching technique. The preparation process of the template is simple, rapid, and low-cost. The cross sectional profiles of raised microchannels on the template are trapezoidal. The surface roughness of the templates was controlled down to 190 nm. The template can be used repeatedly to generate devices reproducibly. The microfluidic devices of poly(methyl methacrylate) (PMMA) were fabricated by in situ polymerization using the templates. The reproducibility of the fabricated microchannel is high and the relative standard deviation is 0.7% by the in situ polymerization approach. Some physical properties of the polymerized microchannels were characterized including the transparency, the thermal deformation temperature, and the dimensional information. Current monitoring was used to evaluate the electroosmotic flow within the microchannels under the electric field strength of 300 V/cm.

Equipment Design↗

PubMed2002

Development of column-pretreatment chelating resins for matrix elimination/multi-element determination by inductively coupled plasma-mass spectrometry.

Chelating resins, two kinds of iminodiacetate derivatives (IDA) of cross-linked chitosan (CCS) were synthesized and investigated for adsorption capacity, matrix elimination and collection/concentration of analytes by a column pretreatment in a multi-element ICP-MS determination method. The adsorption behavior of 54 elements at the 10 ng ml(-1) level on chitosan derivatives in a packed mini-column was systematically examined. Almost 30 kinds of metal ions were recovered quantitatively at pH 5 with CCS-HP/IDA (cross-linked chitosan possessing N-2-hydroxypropyl iminodiacetic acid groups) column. Compared with available chitosan-iminodiacetate resin, CHITOPEARL CI-03, the recovery of the metal ions such as Cu, Pb and La is satisfactory with CCS-IDA (cross-linked chitosan possessing N,N-iminodiacetic acid groups) and CCS-HP/IDA using 2 M nitric acid as an eluent, which may be attributed to the difference of cross-linking and macroporous structure. Compared with Chelex-100, the adsorption efficiency is in the order: Chelex-100 > CCS-IDA > CCS-HP/IDA, especially in the chelating ability for alkaline earth metals. The resin with a longer spacer (CCS-HP/IDA) showed higher adsorption selectivity between heavy metal ions and alkaline earth metals at pH < 7. The separation efficiency of the major matrix cations in seawater (Na. K, Mg, Ca) has also been investigated, and matrix interference was negligible even in a seawater sample at pH 5 with CCS-HP/IDA. The recoveries of Mn at pH 5 with CCS-HP/IDA or Chelex-100 were almost 100%. However, those of Mg with each resin were 4 or 98%, respectively. The adsorption capacities of synthesized CCS-HP/IDA for Cu(II), Pb(II) and La(III) were 0.90, 0.65 and 0.34 mmol g(-1), respectively. Therefore, the chelating chitosan resins developed are applicable to the pretreatment of trace amounts of elements in various kinds of water samples.

Chelating Agents↗