We propose a novel method to obtain versatile droplets arrays on a regional hydrophilic chip that is fabricated by PDMS soft lithography and regional plasma treatment. It enables rapid liquid dispensation and droplets array formation just making the chip surface in contact with solution. By combining this chip with a special Christmas Tree structure, the droplets array with concentrations in gradient is generated. It possesses the greatly improved performance of convenience and versatility in bioscreening and biosensing. For example, high throughput condition screening of toxic tests of CdSe quantum dots on HL-60 cells are conducted and cell death rates are successfully counted quickly and efficiently. Furthermore, a rapid biosensing approach for cancer biomarkers carcinoma embryonic antigen (CEA) is developed via magnetic beads (MBs)-based sandwich immunoassay methods.
In this work a novel microfluidic platform for cell culture and assay is developed. On the chip a static cell culture region is coupled with dynamic fluidic nutrition supply structures. The cell culture unit has a sandwich structure with liquid channels on the top, the cell culture reservoir in the middle and gas channels on the bottom. Samples can be easily loaded into the reservoir and exchange constantly with the external liquid environment by diffusion. Since the flow direction is perpendicular to the liquid channel on the top of the reservoir, the cells in the reservoir are shielded from shear-force. By assembling the basic units into an array, a steady concentration gradient can be generated. Cell culture models both for continuous perfusion and one-off perfusion were established on the chip. Both adherent and suspended cells were successfully cultured on the chip in 2D and 3D culture modes. After culturing, the trapped cells were recovered for use in a later assay. As a competitive candidate for a standard cell culture and assay platform, this chip is also adaptable for cytotoxicity and cell growth assays.
Though microfluidic paper analytical devices (μPADs) have attracted paramounting attentions in recent years as promising devices for low cost point-of-care tests, their real applications for blood analysis are still challenged by integrating sample preparation with different detection modes on a same μPAD. Herein, we developed a novel μPAD, which well coupled automatic serum extraction with reliable dual mode iron health tests: fluorescent analysis for Fe and colorimetric ELISA for ferritin. All these functions are made available by in situ carbon dots (CDs) and AuNPs sequential patterning techniques. For CDs immobilization, hydrothermal reaction was taken on paper, to which a patterned through-hole polydimethylsiloxane (PDMS) mask was applied. None fluorescence CDs (nF-CDs) were generated on exposed regions, while the fluorescent CDs (F-CDs) were generated simultaneously on covered regions. Sensitive serum iron quantification was realized on the F-CDs modified regions, where Fe ion can selectively quench the fluorescence of F-CDs. For AuNPs immobilization, electroless plating was taken on nF-CDs modified regions. The resulting AuNPs on nF-CDs layer on one hand triggered the coagulation of blood cells and thus led to the longest ever wicking distance for serum separation, on the other hand facilitated colorimetric enzyme linked immunosorbent assay (ELISA) for detection of serum ferritin. Combining the two readings, the μPAD can provide reliable measurement for serum iron and serum ferritin in whole blood. Furthermore, as CDs and AuNPs modified μPAD has the features of easy handling, low-cost, lightweight, and disposability, it is accounting for a promising prototype for whole blood point-of-care analysis.
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