(728g) Size-Specific Microfluidic Devices to Capture Marine Microorganisms from the Environment

Capturing single bacterial cells is challenging, particularly when cells are in heterogeneous samples. Marine ecosystems are home to thousands of bacterial cells, most of which are not yet studied. Therefore, the isolation of marine species is critical to understanding more about these microorganisms. In recent years, micro- and nano-scale isolation and detection techniques such as droplets and flow cytometry have been incorporated in microbiology to improve the studies; however, these methods are very costly, require tedious sample preparation, and cannot be used in-situ. Hence new methods are needed to capture cells from the environment.

We designed and fabricated a microfluidic device containing nanochannels that connects a sample inlet to sample collection chambers. The nanochannels are size-specific to the morphology of bacteria to capture single cells. When a sample is introduced to the device, only a single species can enter the nanochannel and reach the sample collection chamber. Nanochannels were fabricated with electron-beam lithography while the sample inlet and collection chambers were fabricated with photolithography. The height of the nanochannels (700-950 nm) was obtained by metal sputtering. Once the design on the master wafer is completed, poly (dimethylsiloxane) (PDMS) polymer was poured onto the wafer, heat-cured, and pealed off. Access holes were drilled and the devices were bonded to a glass coverslip by oxygen plasma.

We previously showed that our devices could separate model microorganisms such as Escherichia coli and Bacillus subtilis. In this study, we modified our set-up to isolate marine species. Two marine microorganisms that differ in morphology (Psychroserpens sp. and Roseobacter sp.) were introduced into the device and incubated for two days at room temperature. Fluorescent images showed that while both species were present in the sample inlet, only Roseobacter sp. was able to enter the nanochannel and reach the sample collection chamber. Hence this size-specific isolation technique shows promise for capturing cells from the environment.