Fabrication Considerations for Bridged Microfluidic Cell Cultures

A novel bridged-microfluidic for cell-based assays was developed by combining a microstructured optical fiber (MOF) with a microfluidic network with the purpose of continuously monitoring the state of hepatocellular carcinoma (HepG2) cells. In this configuration a solid core MOF with channels in the cladding serves as a bridge for cell transport as well as an evanescent wave-based monitoring system to detect cells labeled with fluorescent nanomaterials. The device was fabricated by positioning an MOF to bridge two polydimethylsiloxane (PDMS) microfluidic networks. Alignment strategies and pressurization considerations to produce this system are presented. Pump systems that support fluid transport through the MOF demonstrated the tendency of flow rate fluctuations even for constant microfluidic pump rates. Spectroscopic measurements confirm the delivery and motion of cells between the two neighboring microfluidic chips. The linewidth of the spectra demonstrated oscillations that were consistent with pressure broadening caused by hydrodynamic fluctuations. Fluctuations in the microfluidic flow ranging from 0.005 to 0.016 Hz were observed. These results are consistent with theoretical principles and provide important information regarding syringe pump artifacts, i.e. fluctuations, observed during spectroscopic measurements in MOF/microfluidic systems.