Development of a Multisectorial Electroactive Nanowell Platform for Selective Single-Cell Sorting and Quantification

Abstract

The rapid isolation of specific rare target cells is of rising importance in current targeted patient treatment plans. Common cell sorting approaches such as stream-based dielectrophoresis (DEP) based cell sorters are limited by their spatial dimensions as only a number of cell types corresponding to the number of output channels of the platform can be sorted. In this thesis, a microfluidic platform for selective single-cell sorting and subsequent quantification of sorted cells is presented, which can be upscaled to a high number of unique cell types without facing the same technical difficulties as previously developed devices. The platform consists of interdigitated electrodes (IDEs) and uses dielectrophoresis to capture target cells in a layer of 10 000 nanoliter wells placed on top. By splitting the design into 10 individually addressable IDE sectors, a large number of different cell types can be captured. This sectorial approach is highly modifiable and allows for complex samples to be captured over different sectors instead of requiring separate output channels for each cell type. The microfluidic behaviour of the platform regarding flow rate and DEP signal strength was examined to determine valid parameters for cell sorting and capture. A clinically relevant mixed sample of benign (MCF-10A) and malignant (MDA-MB-231) breast cells was used to validate the cell sorting performance of the platform and a target to non-target sorting accuracy of over 95\% could be achieved. To monitor sector occupancy and determine how much sample has been sorted, the capabilities of electrochemical impedance spectroscopy were examined. Experimental results revealed that impedimetric measurements can be used to quantify the number of captured cells, removing the need for an additional cell counting structure on the platform and hence reducing system complexity. Lastly, it was discussed how the presented microfluidic platform could be potentially expanded to facilitate single-cell RNA sequencing. The inability of current sequencing platforms to selectively capture and sequence cells from a mixed sample is a major problem of these designs. Since the platform presented in this thesis solves this problem, it may be a good candidate for future on-chip single-cell sequencing. Overall, the presented microfluidic cell sorting platform shows great promise to be used as either a point-of-care device or in clinical environments where reliable sorting of varying cell samples is important.