Microfluidics for cell biology and protein folding


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The main area of research of our group is the development and application of new devices and techniques based on micro-flows and soft materials for cell biology and protein folding research. We collaborate with many bio-research laboratories in San Diego area and outside.

Chemotaxis and gradient response
We have designed and built a variety microchannel networks generating stable linear and exponential gradients of soluble factors, temperature and gas concentrations. These microchannel devices have been used to study the chemotaxis of neutrophil-like HL60 cells, primary neutrophils, and D. discoideum amoebas, the chemotropism of yeast, and the thermotaxis and aerotaxis of E. coli bacteria.

Microbial cultures in microchambers
We built a series of microfluidic devices for on-chip cultures of bacteria and yeast. The devices enable culturing cells at constant medium conditions up to very high cell densities and reaching extremely high densities, tracking a colony starting from a single cellfor >10 generations at a single-cell resolution, rapidly adding and removining soluble factors without loosing cells, testing a range of medium conditions and multiple cell lines in a single experiment, controlling the oxygen tension in the medium, and temporarily immobilizing cells for high-resolution imaging.

Perfusion chambers to study rolling, adhesion, migration of blood cells
We designed and applied novel microfluidic perfusion devices for experiments on blood cells: rolling and adhesion of platelets, rolling of neutrophils, and shear stress reponse of endothelial cells. In addition we built and applied microfluidic perfusion chamber to study the strength of adhesion of platelets, neutrophils, and D. discoideum amoebas. To seal the perfusion devices against substrates with plated cells, we developed an original magnetc clamp.

Substrate regidity sensing and TIRF microscopy of mammalian cells
We developed a technology of high refractive index gels with physiological rigidity that enables combining the traction force and TIRF microscopy of adherent animal cells. We applied it to concurrently visualize the maps of traction forces and points of adhesion of human endothelial cells. We also developed a microfluidic technique to measure the elastic moduli of thin layers of soft gels.

Imaging of the development and behavior of C. elegans worms
We developed a microwell device enabling the extraction of shell-free eggs from C. elegans and the imaging of their early stages of development with the possibility to add and remove desired soluble factors at well-defined time points. We also developed an easy-to-use device that enables adjustable immobilization of C. elegans at different larval and adult stages for extended high-resolution imaging.

Oxygen tension and hypoxia
We designed and built a computer 10-channel gas mixer and used it together with several microfluidic and multiwell plate setups to study cellular behavior and gene expression as a function of oxygen tension in the medium at a high throughput.

Kinetics and thermodynamics of protein folding
We developed and applied a series of microfluidic devices to study the kinetics of protein folding and to obtain equilibrium diagrams of protein conformations at high resolution using measurement of the Foester resonance energy transfer (FRET) from proetin molecules labeled with two fluorescent dyes. We greatly increased the dye photostability by in-situ reagent-free deoxygenation, and brought the time resolution of single-molecule kinetics to 0.2 ms.

Biolistic delivery with a gene gun
We designed and built a series of gene guns for biolistic delivery of nucleic acids and fluorescent dyes into cell in internal layers of tissues and organisms, using our patented technology that eliminates the gas shock wave emerging from the gun barrel, thus preventing mechanical damage to the target tissue. We currently apply the guns to sparsely stain and transfect brain slices and live mouse brain and to transfect cells in the germ line of C. elegans worms.



Alex Groisman

Associate Professor of Physics
phone (858) 822 18 38
fax (858) 534 76 97