Microfluidic Platforms for Investigating Cellular Growth and Sub-Cellular Component Separation

Abstract

A static droplet array was used for growth investigation of single-and multiple cells of two Saccharomyces cerevisiae strains (FY2 and SM14/P1A2). The observed encapsulation efficiency for single cells was 36.4% which was close to the random encapsulation efficiency of 28.9%. For the SM14/P1A2 strain, we observed an average specific growth rate of 0.236 hr^-1 in YNB media and for the FY2-GFP strain we observed an average growth rate of 0.257 hr^-1. The results for the P1A2 strain from the droplet experiment were comparable with the results from the bioreactor studies of the strains. In addition to the static droplet array, we also investigated a perfusion chip to understand the growth heterogeneities of Chlorella vulgaris single and multiple cells. Cell growth can be monitored for multiple days, with preliminary results showing good qualitative agreement between growth and size distributions obtained in bulk and in droplet experiments.

We also studied the enzymatic etching of poly(lactic acid) (PLA) substrates to obtain nano- and micron sized channels. The aim of the project was to etch channels separated by a weir of height in the sub-micron range, enabling the possible separation of sub-cellular components. Characteristic etch rates of 1.45 μm h^-1 and 0.16 μm h^-1 for the poly(lactic acid) at 37⁰C and 24.4⁰C using the enzyme proteinase K were obtained. Lower temperature (24.4⁰C) provided a better control over etch depths of the channels at sub-micron scale. The proposed architecture with the weir depth in the sub-micron range could be used for separation of sub-cellular components like exosomes.