-
[show abstract]
[hide abstract]
ABSTRACT: A fast, low-cost and facile spray method was proposed. It can deposit highly sensitive surface enhanced Raman spectroscopy (SERS) silver nanoparticles (AgNPs) on the paper-microfluidic scheme. The procedures for substrate preparation were studied including different strategies to synthesize AgNPs and the optimization of spray cycles. In addition, the morphologies of the different kinds of paper substrates were characterized by SEM and investigated by their SERS signals. The established method was found to be favorable for obtaining good sensitivity and reproducible results. The relative standard deviations (RSD) of Raman intensity of randomly analyzing 20 spots on the same paper or different filter papers depositing with AgNPs are both below 15%. The SERS enhancement factor is approximately 2 × 10(7) . The whole fabrication is very rapid, robust and does not require specific instruments. Furthermore, the total cost for 1000 pieces of chip is less than $20. These advantages demonstrated the potential for growing SERS applications in the area of environmental monitoring, food safety and bio-analysis in the future. This article is protected by copyright. All rights reserved.
Electrophoresis 05/2013; · 3.30 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Micro total analysis systems (-TAS) or labs-on-achip, have been spreading rapidly due to their desirable characteristics, including reductions in reagent consumption, space requirements and analysis time. This work aimed at establishing an integrated microfluidic system which can supply the cells with fresh medium of oxygen and nutrition continuously at a control flow rate mimicking the microenvironment in vivo. Human non-small cell lung cancer cell line SPCA1 was seeded in a microchip supplied with fresh medium at a constant rate of 15 mm/24 h controlled by a pump. The expression of P-gp for verapamil-pretreated or non-pretreated cells was assayed with immunofluorescence. Both groups cells were exposed to anticancer drug VP-16 at 30 microM for 6 h before the apoptosis analysis online. The results indicated that the cells could grow and spread well for 4 days in the microfluidic system successively furnished with fresh medium. Immunofluorescence assay showed that the intensity of the fluorescence for the verapamil-pretreated cells was obvious weak compared with that of nonpretreated cells. Apoptosis analysis demonstrated that the percentage of apoptotic cells for verapamil-pretreated group increased around twofold compared with that of nonverapamil pretreated group (26.5+/-2.5% versus 10.9+/- 0.85%, p<0.05), showing a similar results as by flow cytometry analysis. All these indicate that P-gp plays an important role in the resistance to VP-16 in SPCA1, the microfluidic system provides a suitable environment for cells survival and is valuable in long time cell culture and bioassays mimicking the microenvironment in vivo and deserved to be studied further.
Biomedical Microdevices 04/2010; 12(2):325-32. · 3.03 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: DNA computing is a new computation form based on DNA biochemical reactions, which is mainly composed of sticker and splicing computation models. In this work, a microfluidic chip-based approach was established for splicing model-based DNA computing. A finite automaton with two input symbols (a, b) and three states (S0, S1, and S2) was applied in the pattern recognition for isosceles triangles. The DNA computation processes of automaton were realized through DNA digestion, ligation, DNA separation, and detection on the microfluidic chip. The established approach is efficient, controllable, and easy to integrate, which paves the way for the building of complete biomolecular computers in the future.
Electrophoresis 10/2009; 30(20):3514-8. · 3.30 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A micropump-actuated negative pressure pinched injection method is developed for parallel electrophoresis on a multi-channel LIF detection system. The system has a home-made device that could individually control 16-port solenoid valves and a high-voltage power supply. The laser beam is excitated and distributes to the array separation channels for detection. The hybrid Glass-PDMS microfluidic chip comprises two common reservoirs, four separation channels coupled to their respective pneumatic micropumps and two reference channels. Due to use of pressure as a driving force, the proposed method has no sample bias effect for separation. There is only one high-voltage supply needed for separation without relying on the number of channels, which is significant for high-throughput analysis, and the time for sample loading is shortened to 1 s. In addition, the integrated micropumps can provide the versatile interface for coupling with other function units to satisfy the complicated demands. The performance is verified by separation of DNA marker and Hepatitis B virus DNA samples. And this method is also expected to show the potential throughput for the DNA analysis in the field of disease diagnosis.
Electrophoresis 09/2009; 30(17):3053-7. · 3.30 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Integrated microvalves have been used to precisely and flexibly control the generation, size, composition of individual droplets and fusion of different droplets in microfluidic devices.
Lab on a Chip 06/2009; 9(10):1340-3. · 5.67 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A simple negative pressure pinched sample injection method was presented. This method combined diaphragm micropumps and a single voltage supply to generate controllable well-defined sample plug, and led to effective electrophoresis separation. The pinched plug was found to be favorable for obtaining representative and reproducible results that the RSD of the migration time and peak height of sodium fluorescein were 0.5 and 2.1%, respectively (n=25). The established method had been applied in separation of amino acid samples. This method has the advantages of well-defined plug, free sample bias effect, high reproducibility and convenience of controlling the negative pressure by the integrated pumps on the microchip. In addition, the single high voltage supply and the world-to-chip interface simplified the instrumentation, which is of benefit to the minimization and automation. These advantages demonstrate the potential of this method for a wide range of applications.
Electrophoresis 02/2009; 29(24):4906-13. · 3.30 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A microfluidic system combining temperature-controlled reactor, analyte delivery, chip electrophoresis (CE) separation, and fluorescence detection was developed, in which the heaters, resistance temperature detectors, enzymatic reactors, CE channels, and pneumatic valves/pumps were integrated onto a single glass-PDMS chip. The microdevice was used to perform the digestion reaction, followed by on-line electrophoresis separation and detection of the resulting fragments with endonuclease BamHI and FokI as models. Pneumatic valves/pumps served not only for isolating the reaction region from the separation medium to prevent contamination, but also for delivering and quantitatively diluting the fluid from the reaction chamber to the CE section. Thus enzymatic reaction and electrophoresis separation could be insulated and connected as needed. A dynamic coating procedure with the use of PVP and mannitol was firstly adopted for glass-PDMS hybrid chip-based DNA separations, leading to an improved separation efficiency with reproducible migration time and theoretical plates. The expected 263- and 287-bp digestion products of BamHI and FokI were definitely verified by the size-based electrophoretic separation and detection. The whole integrated reaction-CE system can be manipulated in a simple manner with good reproducibility, which is expected to be applied in other on-line analysis of various biochemical reactions.
Electrophoresis 02/2009; 29(24):4956-63. · 3.30 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A microfluidic chip featuring parallel gradient-generating networks etched on glass plate was designed and fabricated. The dam and weir structures were fabricated to facilitate cell positioning and seeding, respectively. The microchip contains five gradient generators and 30 cell chambers where the resulted concentration gradients of drugs are delivered to stimulate the on-chip cultured cells. This microfluidics exploits the advantage of lab-on-a-chip technology by integrating the generation of drug concentration gradients and a series of cell operations including seeding, culture, stimulation and staining into a chip. Steady parallel concentration gradients were generated by flowing two fluids in each network. The microchip described above was applied in studying the role of reduced glutathione (GSH) in MCF-7 cells' chemotherapy sensitivity. The parental breast cancer cell line, MCF-7 and the derived adriamycin resistant cell line MCF-7(adm) were treated with concentration gradients of arsenic trioxide (ATO) and N-acetyl cysteine (NAC) for GSH modulation, followed by exposure to adriamycin. The intracellular GSH level and cell viability were assessed by fluorescence image analysis. GSH levels of both cell lines were down-regulated upon ATO treatment and up-regulated upon NAC treatment. For both cell lines, suppression of intracellular GSH by treatment with ATO has been shown to increase chemotherapy sensitivity; conversely, elevation of intracellular GSH by treatment with NAC leads to increased drug resistance. The results indicated that high intracellular GSH level has negative effect on chemotherapy sensitivity, while depletion of cellular GSH may serve as an effective way to improve chemotherapy sensitivity. The integrated microfluidic chip is able to perform multiparametric pharmacological profiling with easy operation, thus, holds great potential for extrapolation to the high-content drug screening.
Journal of Biotechnology 10/2007; 131(3):286-92. · 3.05 Impact Factor
