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Biomedical subjects

Bingcheng Lin

Publications and source records attributed to Bingcheng Lin.

At least 19 recordsLinked to original sources
PubMed2006

Double-cross hydrostatic pressure sample injection for chip CE: variable sample plug volume and minimum number of electrodes.

A novel sample injection method for chip CE was presented. This injection method uses hydrostatic pressure, generated by emptying the sample waste reservoir, for sample loading and electrokinetic force for dispensing. The injection was performed on a double-cross microchip. One cross, created by the sample and separation channels, is used for formation of a sample plug. Another cross, formed by the sample and controlling channels, is used for plug control. By varying the electric field in the controlling channel, the sample plug volume can be linearly adjusted. Hydrostatic pressure takes advantage of its ease of generation on a microfluidic chip, without any electrode or external pressure pump, thus allowing a sample injection with a minimum number of electrodes. The potential of this injection method was demonstrated by a four-separation-channel chip CE system. In this system, parallel sample separation can be achieved with only two electrodes, which is otherwise impossible with conventional injection methods. Hydrostatic pressure maintains the sample composition during the sample loading, allowing the injection to be free of injection bias.

Electrodes↗
PubMed2006

Isotachophoresis preconcentration integrated microfluidic chip for highly sensitive genotyping of the hepatitis B virus.

The genotyping of hepatitis B virus (HBV) has become recently a valuable tool not only for epidemiological reasons but also for the clinical practice. Conventional methods for HBV genotyping typically include amplification of the target DNA sequences with a two-round nested PCR followed by separation of the amplified fragments by gel electrophoresis. A microfluidic chip that couples isotachophoresis (ITP) preconcentration and zone electrophoresis (ZE) separation may provide great advantages for sensitive, rapid and cost-effective clinical analysis. In this study, an HBV genotyping method with only one amplification round was developed by the application of the ITP-ZE chip. All the analysis steps of the ITP-ZE separation including sample injection, stacking and separation were performed continuously, controlled by sequential high-voltage switching. A 2.1cm sample plug was preconcentrated between discontinuous buffers in ITP process, followed by ZE separation. Sensitivity enhancement was obtained through the increase of sample loading volume. The average LOD value of the ITP-ZE microfluidic chip was determined to be 0.0021pg/muL. In a large-scale HBV genotyping test, single round PCR products were analyzed by ITP-ZE microfluidic chip, and the results were compared with that of the conventional method. Among the 200 cases studied, the classification rate obtained with microfluidic chip was 93%, which was 6% higher than that obtained with the conventional method. Method with ITP-ZE chip analysis provides HBV genotyping information in reduced PCR amplification time with higher detection rate when compared with conventional method. This method holds great potential for extrapolation to the abundance of similar molecular biology-based techniques in clinical diagnosis.

Base Sequence↗
PubMed2006

Isolation and characterization of angiotensin I-converting enzyme inhibitory peptides derived from porcine hemoglobin.

Animal blood is potentially an untapped source of drugs and value-added food production. More than 400 million pigs are slaughtered each year but porcine blood is usually discarded in China. This study describes the isolation and characterization of angiotensin I-converting enzyme (ACE) inhibitory peptides derived from porcine hemoglobin. The most active hydrolysate was obtained from the peptic digestion of porcine hemoglobin. After the purification of ACE-inhibitory peptides with Sephadex LH-20 gel chromatography and reversed-phase high-performance liquid chromatography (RP-HPLC) on C(18) column, two active fractions were obtained. They were analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS) and electrospray ionization tandem mass spectrometry (ESI-MS/MS). They were LGFPTTKTYFPHF and VVYPWT, corresponding to the 34-46 fragment of the alpha chain and the 34-39 fragment of the beta chain of porcine hemoglobin, with IC(50) values of 4.92 and 6.02 microM, respectively. They were the first found from porcine hemoglobin; in particular, LGFPTTKTYFPHF was a novel ACE-inhibitory peptide. In addition, the purified ACE inhibitors both competitively inhibited ACE, and maintained inhibitory activity even after incubation with gastrointestinal proteases. This suggests that these peptides might have a potential antihypertensive effect.

Amino Acid Sequence↗
PubMed2006

Structural features in carrageenan that interact with a heparin-binding hematopoietic growth factor and modulate its biological activity.

The effects of carrageenans' structural features on its interaction with granulocyte colony-stimulating factor (G-CSF) and on the growth and differentiation of a G-CSF dependent leukemia cell line (NFS-60) were studied. lambda, iota, and kappa carrageenans, with decreasing contents of sulfation, bound to G-CSF with binding constants of (6.2+/-0.6) x 10(5)M(-1), (7.4+/-0.5) x 10(5)M(-1) and (6.0+/-0.4) x 10(5)M(-1), and with 27.7+/-0.2, 17.4+/-0.1 and 8.4+/-0.1 binding sites, respectively. However, kappa carrageenan oligosaccharide had no affinity for G-CSF. The three carrageenans significantly inhibited G-CSF-induced growth of NFS-60 cells. The high sulfate content lambda carrageenan could also induce the maturation of the cells, but relatively low sulfate content iota and kappa carrageenans could not. The results suggested that G-CSF-carrageenan bindings were dependent on carrageenans' sulfate contents and chain lengths, which could also affect the growth and differentiation of NFS-60 cells.

Carbohydrate Conformation↗
PubMed2006

Grafting epoxy-modified hydrophilic polymers onto poly(dimethylsiloxane) microfluidic chip to resist nonspecific protein adsorption.

In order to achieve a simple covalent hydrophilic polymer coating on poly(dimethylsiloxane) (PDMS) microfluidic chip, epoxy modified hydrophilic polymers were synthesized in aqueous solution with a persulfate radical initiation system, and crosslinked onto PDMS pretreated by oxygen plasma and silanized with 3-aminopropyl-triethoxysilanes (APTES). Glycidyl methacrylate (GMA) was copolymerized with acrylamide (poly(AAM-co-GMA)) or dimethylacrylamide (poly(DAM-co-GMA)), and graft polymerized with polyvinylpyrrolidone (PVP-g-GMA) or polyvinylalcohol (PVA-g-GMA). The epoxy groups in the polymers were determined by UV spectra after derivation with benzylamine. Reflection absorption infrared spectroscopy (RAIRS) confirmed covalent grafting of GMA-modified polymers onto PDMS surface. Electroosmotic flow (EOF) in the polymer grafted microchannel was strongly suppressed within the range pH 3-11. Surface adsorption of lysozyme and bovine serum albumin (BSA) was reduced to less than 10% relative to that on the native PDMS surface. On the GMA-modified polymer coated PDMS microchip, basic proteins, peptides, and sodium dodecyl sulfate (SDS) denatured proteins were separated successfully.

Acrylamides↗
PubMed2006

Recent advances of microfluidics in Mainland China.

The history and current status of research on microfluidics in China is summarized in this review. The recent representative contributions in this field by Chinese scientists are cited. A perspective on some trends in future development of this field in China is presented.

Animals↗
PubMed2006

Parallel analysis of biomolecules on a microfabricated capillary array chip.

This paper focused on a self-developed microfluidic array system with microfabricated capillary array electrophoresis (mu-CAE) chip for parallel chip electrophoresis of biomolecules. The microfluidic array layout consists of two common reservoirs coupled to four separation channels connected to sample injection channel on the soda-lime glass substrate. The excitation scheme for distributing a 20 mW laser beam to separation channels in an array is achieved. Under the control of program, the sample injection and separation in multichannel can be achieved through six high-voltage modules' output. A CCD camera was used to monitor electrophoretic separations simultaneously in four channels with LIF detection, and the electropherograms can be plotted directly without reconstruction by additional software. Parallel multichannel electrophoresis of series biomolecules including amino acids, proteins, and nucleic acids was performed on this system and the results showed fine reproducibility.

Amino Acids↗
PubMed2006

Interactions of dextran sulfates with granulocyte colony-stimulating factor and their effects on leukemia cells.

The interactions between granulocyte colony-stimulating factor (G-CSF) and dextran sulfate (DS) with different chain lengths and sulfate contents were studied by capillary zone electrophoresis. It was found that DS with a molecular mass of 500 kDa (DS500) could bind to G-CSF and the binding constant and binding sites were determined using Scatchard plot to be 1.17 x 10(6) M(-1) and 3, respectively. DS with a molecular mass of 40 kDa also had the affinity to G-CSF and the binding constant and binding sites were 1.01 x 10(6) M(-1) and 8, respectively. However, DS with a molecular mass of 8 kDa and the non-sulfated saccharide, dextran, had no affinity to G-CSF. The results indicate that the interactions between G-CSF and DS are dependent on the chain lengths and sulfate contents of the saccharides. In addition, the effects of G-CSF-binding DS on a G-CSF-dependent leukemia cell line were investigated using biological methods. Results show that DS500 plus G-CSF has potential therapeutic effect on cancers because their combination could inhibit the growth and induce the differentiation of the leukemia cells.

Animals↗
PubMed2006

Studying protein-drug interaction by microfluidic chip affinity capillary electrophoresis with indirect laser-induced fluorescence detection.

We developed a microfluidic chip-affinity CE method based on indirect LIF detection to study protein-drug interactions. The interaction between heparin and BSA was quantitatively studied, as a model system. In our method, sodium fluorescein was chosen as background, and redistilled water as marker to monitor EOF. The electrophoretic mobility changes of BSA were measured, with various concentrations of heparin added to the running buffer. Each run was completed within 80 s. The binding constant was determined to be (1.24 +/- 0.05) x 10(3) M(-1), which was in good agreement with that reported in the literature.

Electrophoresis, Microchip↗
PubMed2006

Integration of nanoporous membranes for sample filtration/preconcentration in microchip electrophoresis.

Microfluidic devices integrating membrane-based sample preparation with electrophoretic separation are demonstrated. These multilayer devices consist of 10 nm pore diameter membranes sandwiched between two layers of PDMS substrates with embedded microchannels. Because of the membrane isolation, material exchange between two fluidic layers can be precisely controlled by applied voltages. More importantly, since only small molecules can pass through the nanopores, the integrated membrane can serve as a filter or a concentrator prior to microchip electrophoresis under different design and operation modes. As a filter, they can be used for separation and selective injection of small analytes from sample matrix. This has been effectively applied in rapid determination of reduced glutathione in human plasma and red blood cells without any off-chip deproteinization procedure. Alternatively, in the concentrator mode, they can be used for online purification and preconcentration of macromolecules, which was illustrated by removing primers and preconcentrating the product DNA from a PCR product mixture.

DNA↗
PubMed2006

Studying drug-plasma protein interactions by two-injector microchip electrophoresis frontal analysis.

We developed a simple, rapid, and sensitive two-injector microchip electrophoresis frontal analysis (MCE-FA) method for studying drug-plasma protein interactions. In this method, large volumes of a reference sample and drug-plasma protein mixture were simultaneously introduced into the respective sections of the microchannel through the separated injectors and then electrophoresed. Since the reference sample did not meet with the interacting species during migration, it could be used as an external standard. The interaction between heparin and HSA was quantitatively characterized as a model system. The binding constant was found to be (1.53 +/- 0.01) x 10(4) M(-1).

Anticoagulants↗
PubMed2006

A sheath-flow nanoelectrospray interface of microchip electrophoresis MS for glycoprotein and glycopeptide analysis.

Microchip was coupled with MS through a stable, sensitive, and controllable sheath-flow nanoelectrospray (nES) interface for glycoprotein and glycopeptide analysis. The nano-ESI (nESI) was made with a delivery capillary, a commercial nES capillary, and a stainless steel (SS) tube which were connected together through a tee unit. High voltage for nES was applied on the SS tube and the commercial nES capillary was used as nES emitter. The delivery capillary was attached to the microchannel for delivering liquid from microchip to the nESI source. The flow rate of sheath liquid was optimized to be 100-200 nL/min which largely reduced the sample dilution. The detection limit of peptides on this microchip/MS platform was at femtomole level. Glycoprotein and glycopeptides were also successfully analyzed on the platform. All the glycoforms and glycopeptides of ribonuclease B (RNase B) were identified with this method. Some structures of the glycopeptides from RNase B were further characterized with MS/MS on the microchip, coupled with a quadrupole IT-MS.

Amino Acid Sequence↗
PubMed2006

Integrated isotachophoretic preconcentration with zone electrophoresis separation on a quartz microchip for UV detection of flavonoids.

A quartz microchip integrated isotachophoretic (ITP) preconcentration with zone electrophoresis (ZE) separation was fabricated using a novel multi-point pressure method featured in normal temperature and lower pressure during bonding process. ITP followed by subsequential ZE of two flavonoids, quercetin and isorhamnetin on the microchip was performed consecutively on the homemade microfluidic workstation with UV detection, resulting in a decreased detectable concentration of 32-fold, compared to the ZE mode only, and their detection limits decreased down to 0.2 microg/mL and 1.2 microg/mL, respectively.

Electrophoresis, Microchip↗
PubMed2006

Quantitative investigation of the interaction between granulocyte-macrophage colony-stimulating factor and heparin by capillary zone electrophoresis.

The interactions between granulocyte-macrophage colony-stimulating factor (GM-CSF) and heparin or low-molecular weight heparin (LMWH) were studied by CZE. It was found that GM-CSF could bind to both heparin and LMWH. The binding constants were calculated from Scatchard regression to be (6.5 +/- 0.8) x 10(5)/M and (11.2 +/- 0.7) x 10(5)/M, respectively. The specificity of the interaction between GM-CSF and heparin was also studied by employing another sulfated K carrageenan oligosaccharide as a control. Results showed that K carrageenan oligosaccharide could not interact with GM-CSF, indicating that GM-CSF could specifically interact with heparin.

Carrageenan↗
PubMed2005

Pharmacological studies of anti-diarrhoeal activity of Gentianopsis paludosa.

The pharmacological studies of anti-diarrhoeal activity of Gentianopsis paludosa were carried out. The 75% ethanol extract (100-400 mg/kg) of Gentianopsis paludosa inhibited castor oil-induced diarrhoea and also reduced gastrointestinal motility in the charcoal meal test in mice. In the rabbit-isolated ileum, the extract showed inhibitory effects not only on its spontaneous contraction, but also on acetylcholine (Ach, 0.1 mM)- and KCl (60 mM)-induced contractions. Furthermore, the ethanol extract (0.4-0.6 mg/ml) shifted the CaCl2 dose-effect curves to the right in a non-competitive manner and significantly reduced the acetylcholine-induced contraction of isolated ileum in Ca2+-free solution like verapamil (0.1 mM), which suggest that the extract interferes with Ca2+ movement. These results support the traditional use of Gentianopsis paludosa in the treatment of diarrhoea.

Acetylcholine↗
PubMed2005

Microwave plasma treatment of polymer surface for irreversible sealing of microfluidic devices.

Microwave plasma was generated in a glass bottle containing 2-3 Torr of oxygen for plasma treatment of a polymer surface. A "kitchen microwave oven" and a dedicated microwave digestion oven were used as the power source. Poly(dimethylsiloxane)(PDMS) slabs treated by a 30 W plasma for 30-60 s sealed irreversibly to form microfluidic devices that can sustain solution flow of an applied pressure of 42 psi without leaking. Experimental set up and conditions for the production of a homogeneous plasma to activate the PDMS surface for irreversible sealing are described in detail. The surface of a microwave plasma-treated PDMS slab was characterized using atomic force microscopy (AFM) and attenuated total reflection-Fourier Transform infrared spectroscopy (ATR-FTIR). The plasma-treated surface bears silica characteristics.

Dimethylpolysiloxanes↗
PubMed2005

Mini-electrochemical detector for microchip electrophoresis.

This paper presents the development of a mini-electrochemical detector for microchip electrophoresis. The small size (3.6 x 5.0 cm2, W x L) of the detector is compatible with the dimension of the microchip. The use of universal serial bus (USB) ports facilitates installation and use of the detector, miniaturizes the detector, and makes it ideal for lab-on-a-chip applications. A fixed 10 M ohm feedback resistance was chosen to convert current of the working electrode to voltage with second gain of 1, 2, 4, 8, 16, 32, 64 and 128 for small signal detection instead of adopting selectable feedback resistance. Special attention has been paid to the power support circuitry and printed circuit board (PCB) design in order to obtain good performance in such a miniature size. The working electrode potential could be varied over a range of +/-2.5 V with a resolution of 0.01 mV. The detection current ranges from -0.3 x 10(-7) A to 2.5 x 10(-7) A and the noise is lower than 1 pA. The analytical performance of the new system was demonstrated by the detection of epinephrine using an integrated PDMS/glass microchip with detection limit of 2.1 microM (S/N = 3).

Computers↗