UC Irvine

Dissecting the regulation of gene expression processes is fundamental to understand how cells function. Techniques used to obtain our current view of gene expressions rely on isolating mRNAs from large numbers of cells, which often associates with a loss or damage of the material, as well as the loss of spatial information. Also, individual cells within a population are unlikely to behave all in the same way, and current standard techniques are unable to detect cell-to-cell differences that can result from genetic variation, biological noise and different characteristics of genes within a population.

To solve these limitations, we developed a sensitive and non-destructive method and apparatus for tracking gene expressions on single cell level within a population of cells, either on a collagen cell culture gel or in a microfluidic environment. The developed bench-top instrument utilizes a modified AFM (Atomic Force Microscopy) probes for in situ extraction of mRNA molecules from single cells. The modified coaxial AFM probe serves as nanotweezer, and wherein the application of an alternating potential between the inner and outer electrodes of the co-axial cable creates a dielectrophoretic force for attracting target molecules toward the tip-end. For adherent cell lines, the samples are cultured on collagen gel for select-and-probe analysis. An integrated microfluidic/nanoprobe platform is also developed for gene expression analysis of suspension cells on single cell level.

This system directly targets and samples down to a few molecules within a single living cell, without the need for purification and averaging typically of conventional technologies. By providing reliable and exceptional sensitivity to identify differences between individual cells in a seemingly homogeneous population, the system creates possibilities for assaying the genomic analysis in living cells and tracking them in response to external stimuli. This technique has potential impacts on understanding the heterogeneity of transcriptional responses as well as its implications for cell function and disease. It is going to have broad application areas ranging from systems biology to cancer research.