Multiplex microfluidic system integrating sequential operations of microalgal lipid production.

The unit cost for the production of algal biofuel needs to be reduced in order to be a substitute for fossil fuel. To achieve this goal, the development of a novel system is needed for a rapid screening of numerous microalgal species to isolate superior strains with the highest lipid productivity. Here, we developed a PDMS-based multiplex microfluidic system with eight chambers and micropillar arrays to expedite multiple steps for lipid sample preparation from different microalgal strains. We could rapidly and efficiently perform sequential operations from cell culture to lipid extraction of eight different microalgal strains simultaneously on a single device without harvesting and purification steps, which are labor- and energy-intensive, by the simple injection of medium and solvent into the central inlet due to the integrated micropillar arrays connecting the chambers and central inlet. The lipid extraction efficiency using this system was comparable (94.5-102.6%) to the conventional Bligh-Dyer method. We investigated the cell growth and lipid productivity of different strains using the microfluidic device. We observed that each strain has a different lipid accumulation pattern according to stress conditions. These results demonstrate that our multiplex microfluidic approach can provide an efficient analytical tool for the rapid analysis of strain performances (e.g. cell growth and lipid productivities) and the determination of the optimal lipid induction condition for each strain.

Engineering controllable architecture in matrigel for 3D cell alignment.

We report a microfluidic approach to impart alignment in ECM components in 3D hydrogels by continuously applying fluid flow across the bulk gel during the gelation process. The microfluidic device where each channel can be independently filled was tilted at 90° to generate continuous flow across the Matrigel as it gelled. The presence of flow helped that more than 70% of ECM components were oriented along the direction of flow, compared with randomly cross-linked Matrigel. Following the oriented ECM components, primary rat cortical neurons and mouse neural stem cells showed oriented outgrowth of neuronal processes within the 3D Matrigel matrix.

Live cell imaging compatible immobilization of Chlamydomonas reinhardtii in microfluidic platform for biodiesel research.

This paper describes a novel surface immobilization method for live-cell imaging of Chlamydomonas reinhardtii for continuous monitoring of lipid droplet accumulation. Microfluidics allows high-throughput manipulation and analysis of single cells in precisely controlled microenvironment. Fluorescence imaging based quantitative measurement of lipid droplet accumulation in microalgae had been difficult due to their intrinsic motile behavior. We present a simple surface immobilization method using gelatin coating as the "biological glue." We take advantage of hydroxyproline (Hyp)-based non-covalent interaction between gelatin and the outer cell wall of microalgae to anchor the cells inside the microfluidic device. We have continuously monitored single microalgal cells for up to 6 days. The immobilized microalgae remain viable (viability was comparable to bulk suspension cultured controls). When exposed to wall shear stress, most of the cells remain attached up to 0.1 dyne/cm(2) . Surface immobilization allowed high-resolution, live-cell imaging of mitotic process in real time-which followed previously reported stages in mitosis of suspension cultured cells. Use of gelatin coated microfluidics devices can result in better methods for microalgae strain screening and culture condition optimization that will help microalgal biodiesel become more economically viable.