Application of multifunctional microfluidic chips to suspension cell-cell communication research

Abstract

A series of microfluidic chips were developed for the research of suspension cells. These microfluidic chips could be used to precisely manipulate cells and control cell environment at single and multiple cell levels. These microdevices provide novel platforms, open new avenues for cell biology research and contribute to breaking the bottleneck of biology research. Following is an outline of the contents and results of the thesis: (1) On the basis of sandbag structures developed by our lab, the design of cell immobilization structures was improved. In one chip, a single cell array, containing approximate 600 single Jurkat cells, could be formed for eight-channel analysis in parallel. The responses of calcium-release activated Ca2+ (CRAC) channels to activators and inhibitors from the cell array were recorded and analyzed at the single cell level. The variation of CRAC channel response was observed. Although the variation of the CRAC channel response was common in single cells, the average values of 50 single cells could reflect the effects of inhibitors at high concentrations. These results demonstrated that our microfluidic chip could provide a platform to form single cell arrays for the multi-channel studies of the heterogeneity of calcium channel responses. (2) A microfluidic microdevice was developed to exert mechanical stimulation on a single suspension cell for mechanosensation research. In this microfluidic chip, a single cell could be isolated from a population, and subsequently trapped. Mechanical stimulation could then be exerted on the trapped cell. Using this chip, the mechanosensation of HL60 cells (leukemic cells) was studied. It was found that mechanical stimulation could trigger extracellular calcium to flow into HL60 cells through channels on cell membranes. The cytoskeleton, such as microfilament (consist of actins) and microtubules (consist of tubulins), was not a prerequisite for the mechanosensation of HL60 cells. Additionally, two function units for the entrapment of single cells and the exertion of mechanical stimulation were integrated into one chip for mechanosensation study in parallel. HL60 cells (leukemic cells) and Jurkat cells (lymphocytes) both responded to direct mechanical stimulation. These results demonstrate that the developed microfluidic device can be used to investigate the mechanosensation in a single suspension cell and so make it possible to conduct studies in parallel. (3) Cell immobilization structures, a cell entrapment and a cell compressive component and microvalves were integrated in one microfluidic chip. In this microfluidic chip, suspension cell-cell communication could be in real time monitored. Using the chip, the influence of different factors, including fluid states (static or flowing) and mechanical stimulation modes (single or persistent), was evaluated. Additionally, calcium oscillations were observed in some of the recipient cells when mechanical stimulation was exerted on a small number (10 or 31) of donor cells in the compressive component. In this thesis, a serial of components were developed to provide the capabilities of cell manipulation and the exactly control of chemical and physical environment. With the integration of these components in chips, biological analysis and cell research could be conducted, including CRAC channel analysis in parallel, the mechanosensation study at the single suspension cell level and suspension cell-cell communication. These results demonstrated that the application of microfluidic chips extended to the research of mechanosensation and intercellular communication at the single cell level and the development of these microfluidic chips also open the new avenue for suspension cell research, which could be conducted using traditional methods.