Preparation of Electrochemical Microfluidic Device Based onPulse Driving and Controlling of Microfluids Technique / 分析化学

The fabrication system for the electrochemical microfluidic device was set up based on the pulse driving and controlling of microfluids technology.The nano silver ink and glycerol solution were jetted on the glass substrates to form the microelectrode pattern and the liquid mold pattern for the microchannel.Then the microelectrode and microchannel were obtained through a sintering process and a molding process, respectively.The electrochemical mircrofluidic device was Finally prepared through a bonding process with the microelectrode and the microchannel.The influences of the system parameters on the formation of the droplet were studied, as well as the influences of the droplets diameter and the overlap on the formation of the liquid lines.The minimal width, the thickness and the resistance of the prepared microelectrode were 45 μm, 2.2 μm and 5.2 μΩ cm, respectively.The minimal width of the microelectrode was 35 μm and the surface was smooth.The electrochemical flow detection of glucose concentration was carried out with the device, and the results showed that the glucose concentration had a high linear correlation with the response current, which could be used in the quantitative detection of glucose concentration.The fabrication of the electrochemical microfluidic device based on the pulse driving and controlling of micro fluids technology has many advantages such as simple system structure, lower cost and higher accuracy of the micro droplet and can be used in the preparation of the devices in the biochemical analysis and biosensor areas.

Indirect Co-Culture of Stem Cells from Human Exfoliated Deciduous Teeth and Oral Cells in a Microfluidic Platform

Oral epithelial-mesenchymal interactions play a key role in tooth development and assist differentiation of dental pulp. Many epithelial and mesenchymal factors in the microenvironment influence dental pulp stem cells to differentiate and regenerate. To investigate the interaction between oral cells during differentiation, we designed a microfluidic device system for indirect co-culture. The system has several advantages, such as consumption of low reagent volume, high-throughput treatment of reagents, and faster mineralization analysis. In this study, stem cells from human exfoliated deciduous teeth were treated with media cultured with human gingival fibroblasts or periodontal ligament stem cells. When human exfoliated deciduous teeth was incubated in media cultured in human gingival fibroblasts and human periodontal ligament stem cells under the concentration gradient constructed by the microfluidic system, no remarkable change in human exfoliated deciduous teeth mineralization efficiency was detected. However, osteoblast gene expression levels in human exfoliated deciduous teeth incubated with human gingival fibroblasts media decreased compared to those in human exfoliated deciduous teeth treated with human periodontal ligament stem cells media, suggesting that indirect co-culture of human exfoliated deciduous with human gingival fibroblasts may inhibit osteogenic cytodifferentiation. This microfluidic culture device allows a co-culture system set-up for sequential treatment with co-culture media and differentiation additives and facilitated the mineralization assay in a micro-culture scale.

Colorimetric Determination of Lactate Dehydrogenase on Paper-Based Microwell Arrays Microfluidic Device / 分析化学

A low-cost, simple, sensitive detection method of lactate dehydrogense ( LDH) was developed on paper-based microwell arrays microfluidic device. The phenazine methyl sulfate/nitrotetrazolium blue chloride ( PMS/NBT) detection system was used for LDH detection and the colorimetric results were recorded by both Gel Documentation System and a common camera. Under the optimized conditions, the colorimetric intensity showed a linear correlation to the activity of LDH in the range of 10 to 150 U/L with a limit of detection (LOD) of 9. 44 U/L (3σ) by Gel Documentation System;and the linear range was 15-150 U/L by camera with a LOD of 12. 36 U/L (3σ). Foremost, it was found that human serum albumin (HSA) had an effect on the colorimetric enhancement in this detection system. This low-cost, portable paper-based analytical platform could be suitable for the application in the point-of-care with high sensitivity and reproducibility.

Microfluidics-based assay on the effects of microenvironmental geometry and aqueous flow on bacterial adhesion behaviors / 药物分析学报

Abstract A new microfluidic system with four different microchambers （a circle and three equilateral concave polygons） was designed and fabricated using poly（dimethylsiloxane） （PDMS） and the soft lithography method. Using this microfluidic device at six flow rates （5, 10, 20, 30, 40, and 50 μL/h）, the effects of microenvironmental geometry and aqueous flow on bacterial adhesion behaviors were investigated. Escherichia coli HB101 pGLO, which could produce a green fluorescent protein induced by L-arabinose, was utilized as the model bacteria. The results demonstrated that bacterial adhesion was significantly related to culture time, microenvironment geometry, and aqueous flow rates. Adhered bacterial density increased with the culture time. Initially, the adhesion occurred at the microchamber sides, and then the entire chamber was gradually covered with increased culture time. Adhesion densities in the side zones were larger than those in the center zones because of the lower shearing force in the side zone. Also, the adhesion densities in the complex chambers were larger than those in the simple chambers. At low flow rates, the orientation of adhered bacteria was random and disorderly. At high flow rates, bacterial orientation became close to the streamline and oriented toward the flow direction; All these results implied that bacterial adhesion tended to occur in complicated aqueous flow areas.The present study provided an on-chip flow system for physiological behavior of biological cells, as well as provided a strategic cue for the prevention of bacterial infection and biofilm formation.

Microfluidics-based assay on the effects of microenvironmental geometry and aqueous flow on bacterial adhesion behaviors / 药物分析学报

A new microfluidic system with four different microchambers (a circle and three equilateral concave polygons) was designed and fabricated using poly(dimethylsiloxane) (PDMS) and the soft lithography method.Using this microfluidic device at six flow rates (5,10,20,30,40,and 50 μL/h),the effects of microenvironmental geometry and aqueous flow on bacterial adhesion behaviors were investigated.Escherichia coli HB101 pGLO,which could produce a green fluorescent protein induced by L-arabinose,was utilized as the model bacteria.The results demonstrated that bacterial adhesion was significantly related to culture time,microenvironment geometry,and aqueous flow rates.Adhered bacterial density increased with the culture time.Initially,the adhesion occurred at the microchamber sides,and then the entire chamber was gradually covered with increased culture time.Adhesion densities in the side zones were larger than those in the center zones because of the lower shearing force in the side zone.Also,the adhesion densities in the complex chambers were larger than those in the simple chambers.At low flow rates,the orientation of adhered bacteria was random and disorderly.At high flow rates,bacterial orientation became close to the streamline and oriented toward the flow direction.All these results implied that bacterial adhesion tended to occur in complicated aqueous flow areas.The present study provided an on-chip flow system for physiological behavior of biological cells,as well as provided a strategic cue for the prevention of bacterial infection and biofilm formation.