Biomedical subjects

Chun-Che Lin

Publications and source records attributed to Chun-Che Lin.

4 recordsLinked to original sources

PubMed2002

Flow-through sampling for electrophoresis-based microchips and their applications for protein analysis.

This work presents a model behind the operation of a flow-through sampling chip and its application for immunoseparation, as well as its integration with a wash/elution bed for protein purification, concentration, and detection. This device used hydrodynamic pressure to drive the sample flow, and a gating voltage was applied to the electrophoretic channel on the microchip to control the sample loading for the separation and to inhibit sample leakage. The deduced model indicates that the critical gating voltage (VC) that is defined as the minimum gating voltage applied to the microchip for sampling is a function of the pump flow rate, the configuration of the microchannel on the chip, and the electroosmosis of the buffer solution. It was found that the theoretical V(C) values calculated from the measured electroosmotic mobilities and flow split ratios were comparable to those experimentally obtained from two microchips with different sampling channel sizes. This had an error percentage ranging from 1 to 20%. Because the hydrodynamic flow is insensitive to electrophoretic mobility, this electrophoresis-based microchip device was free of injection bias due to different ionic strength and electrophoretic mobility in the sample. Additionally, the usefulness of this device was demonstrated for the study of affinity interactions. Mixtures of Cy5-labeled bovine serum albumin (Cy5-BSA) and anti-BSA in various proportions were introduced into the microchip via a syringe pump, and the immunocomplex was electrophoretically separated from the free Cy5-BSA on the microchip. Based on the relative intensity of the free and complex BSA, the binding constant of BSA and anti-BSA was estimated as 3.3 x 10(7) M(-1). Furthermore, a C18 microcartridge (20 microL) was connected to the hydrodynamic inlet of the microchip. Using this device, the wash/elution step can be integrated on-line with the electrophoretic separation and detection on the microchip. Results show that the calibration curve of Cy5-BSA obtained from this integrated device has an R2 value greater than 0.99 and a minimum of quantitation at approximately 10 ng. This direct sampling method is another means of subfractionation, resulting in a relatively greater concentration factor than the average concentration of the whole fraction. Moreover, the electrical field-free bed ensures that the protein interaction will not be affected by the electric field during the wash/elution step.

Algorithms↗

PubMed2002

Automation for continuous analysis on microchip electrophoresis using flow-through sampling.

Automation of electrophoretic microchips for sequential analysis of different samples is demonstrated. This system used an autosampler, which was on-line connected to the microchip and the whole process including sample loading and injection, analysis and data acquisition as well as washing were all automated. Rhodamin B at different concentrations was first loaded into a hydrodynamic flow stream by an autosampler, delivered to the microchip, and then sequentially injected into the electrophoretic microchannel for analysis and detection. Automation was achieved by running two independent programs, one for sample loading by an autosampler and the other one for electrophoretic injection by voltage switching, on the same computer. Using this sampling chip, each loaded volume (0.2-1 microL) can be injected for dozens of electrophoretic analyses (1-10 nL for each injection). The variances caused by the external connections, which did not affect the electrophoretic analysis but would cause band broadening of the loaded sample in the hydrodynamic flow stream, were theoretically deduced. Results indicate that the dead volume (approximately 300 nL) due to the connection fitting on the chip could lead to dilution of the loaded sample by a factor of one when 0.2 microL of sample was loaded. Such a design allows sequential analysis of a series of samples while the running buffer is continuously pumped into the connection capillary as well as microchannels for washing between two loaded samples to minimize cross contamination without human intervention. Using this sampling chip, the required sample amount and handling time can be greatly reduced compared to the manual method.

Automation↗

PubMed2002

Endoscopic hemostasis of a bleeding marginal ulcer: hemoclipping or dual therapy with epinephrine injection and heater probe thermocoagulation.

BACKGROUND AND AIMS: Endoscopic hemoclipping and dual therapy with epinephrine injection and heater probe thermocoagulation have been proven effective in the hemostasis of bleeding peptic ulcers. However, the hemostatic efficacy has not been investigated in bleeding marginal ulcers. The aim of this study is to investigate the hemostatic efficacy of endoscopic hemoclipping and dual therapy with epinephrine injection and heater probe thermocoagulation in bleeding marginal ulcers. METHODS: From November 1997 to July 2000, 50 patients with active marginal ulcer bleeding underwent either hemoclipping (20 patients) or dual therapy (30 patients) for hemostasis. The demographic data, clinicopathological characteristics, endoscopic findings, initial hemostatic rates, rebleeding rates, amount of blood transfusion, the need of surgery, and mortality rates were collected and analyzed. RESULTS: Marginal ulcers were located at the anastomotic site (64%), saddle portion (22%), efferent loop (10%), or at the afferent loop (4%). The bleeding stigmata were classified into spurting artery (32%), oozing vessel (38%), visible vessel (20%), and blood clot adhesion (10%). The overall therapeutic results in 50 patients were initial hemostasis (100%), rebleeding rate (22%), need for surgery (4%), and hospital mortality rate (4%). There was no significant difference in demographic data and clinicopathological characteristics between the two modes of treatments, whereas recurrent bleeding developed in 5% in the hemoclipping group and 33% in the dual therapy group. No complication related to the procedure occurred in either mode of therapy. The hospital mortality rates were 0 and 6.7%, respectively. CONCLUSION: Endoscopy is effective in achieving initial hemostasis from bleeding marginal ulcers. However, the rebleeding rate remains high and repeated endoscopy may be needed to arrest the hemorrhage.

Adrenergic Agonists↗

PubMed2002

Endoscopic hemoclip placement and epinephrine injection for Mallory-Weiss syndrome with active bleeding.

BACKGROUND: Mallory-Weiss syndrome with active bleeding requires effective hemostasis. This is an investigation of the respective efficacy and safety of endoscopic hemoclip placement and endoscopic epinephrine injection in Mallory-Weiss syndrome. METHODS: Thirty-five patients with Mallory-Weiss syndrome with spurting vessels or oozing in a university hospital were enrolled prospectively and randomly assigned to endoscopic hemoclip placement (18 patients) or endoscopic epinephrine injection (17 patients) performed by 4 endoscopists with similar clinical experiences. Demographic characteristics, endoscopic variables, and outcome parameters as well as rates of hemostasis and recurrent bleeding were analyzed. RESULTS: The mean (SD) number of hemoclips applied was 2.5 (1.2) and the mean volume of injection was 7.9 (4.3) mL. Primary hemostasis was achieved in all 35 patients. In each group there was 1 case of recurrent bleeding. Secondary hemostasis was achieved by repeating the same procedures as at randomization in both cases. There were no significant differences in age, gender, prior ingestion of alcohol, presenting symptoms, hemoglobin level, shock, comorbid diseases, bleeding stigmata, tear location, blood transfusion, or hospitalization between the groups. There were no procedure-related complications in either group; surgery was not required in any patient. For both groups, there were no second episodes of recurrent bleeding, procedure-related complication, or need of operation. CONCLUSION: Endoscopic hemoclip placement and endoscopic epinephrine injection are equally effective and safe for the management of active bleeding in Mallory-Weiss syndrome, even in patients with shock or comorbid diseases.

Adult↗