Development of a microfluidic polyelectrolyte purification device for planetary samples

Europa, Enceladus and other ocean worlds contain potentially habitable environments in their oceans and icy shells that are excellent locations to search for evidence of life. However, challenges exist for biosignature detections in situ, as the planetary environment is extreme (e.g. high radiation at Europa) and samples may contain very low biomass, high salinity, acidic/basic pH, complex chemical compositions, and biology may be in a robust spore/protective structure that must be accessed in order to sample the bio-molecules within. We suggest that searching for polyelectrolytes, e.g. DNA or RNA for earth-based biology, would be a powerful in situ measurement as these molecules transfer heritable information across generations, and these or other classes of polyelectrolytes elsewhere could serve the same function. Therefore, an observation of a polyelectrolyte would indicate life analogous to, yet possibly very different from, terrestrial life. In order to overcome the aforementioned challenges of detecting a polyelectrolyte in an extreme planetary environment, our team is working to develop a microfluidic sample purification device that disrupts, purifies, and captures polyelectrolytes for analysis on a nanopore sequencing platform. The current chip prototype invokes an innovative acoustofluidic method and chip channel design to excite high velocity fluid vortices and optimize disruption at a micro scale. We present here, experimental results for the disruption efficiency of Bacillus atropheus spores for a range of sample spore input concentrations. Extracted spore levels are compared to several standard laboratory environmental sample preparation processes to baseline chip results against: chemical or physical lysis, sonication, or acousto-sonication. For Bacillus spores, acousto-sonication provided the best performance, although only for spore concentrations of 10^7 / mL and greater. These results indicate the difficulty in sample preparation of spores (considered the toughest DNA extraction matrix), while supporting the decision to apply acousto-sonication in our microfluidic device to maximize extraction potential. Future work will integrate the preparation chip with a downstream synthetic nanopore sequencing platform for automated sample to answer functionality.