Klavs Jensen

Biosketch

Ph.D. Chemical Engineering • 1980
University of Wisconsin

Research in Microsystems

Research in the Jensen lab focuses on chemistry and transport phenomena related to the development of functional micro- and nano-structured materials and devices for chemical and biological applications. Microfabrication of biological devices provides several improvements over more conventional methods by enabling integration of cellular manipulations (stimulus, selecting, sorting, and lysing) and cellular component handling (fractionation, identification, and lysing) with biochemical assays.

The challenge for many CDP efforts is efficient cellular analysis of small populations of cells, their subcellular components and intracellular proteins. Current laboratory techniques involve laborious and time-consuming procedures with large sample volumes (>million cells). Protein profiling of cells in different physiological states requires a very large number of experiments in which cells are subjected to a stimulus (chemical, thermal, mechanical, etc.) and then analyzed for protein localization, modification and macromolecular assembly. Investigations typically start with complete cell lysis by chemical or mechanical means followed by a detailed study of the particular proteins chemistry of interest. However, in many cases it also desirable to be able to minimize the potential impact of the cell membrane rupture and moreover, to identify the localization of proteins within the cellular structure. In collaboration with other CDP labs, we have developed microfluidic systems that handle a small number of cells (~thousands), lyse them, and isolate the organelles of interest, e.g. mitochondria.

The overall aim of the effort is integration cell manipulations (growth, stimulus, selection, sorting, and lysing) and cellular component handling (fractionation, identification, and lysing) in new biological assays. A small population of cells is subjected to a stimulus and a subset of these cells is then selected by a particular response. Rupturing of the plasma membranes of selected cells to release cytosolic contents, including vesicles and organelles, is achieved by electrical, mechanical and chemical microfluidic approaches. Electroporation is particularly useful for opening the cell membrane, since the electrical potential and frequency can be adjusted so that the outer cell membrane is ruptured without affecting organelles, such as mitochondria and nuclei. Microfabricated devices enable tuning of alternating electric fields to maximize cross cell membrane potential while minimizing impact on the membranes of the organelles.

We also develop microfluidic devices for monitoring cellular response to stimuli as a step to towards obtaining the large sets of data for protein activities, concentrations, and states of modification needed to understand cell signaling pathways. Soft lithography techniques are used to realize devices for cell growth, stimulus, and lysis, as well as separation of organelles and proteins. Simulations support device design and provide quantitative interpretation of experimental observations. Multiphase rapid mixing, cell stimulus and lysis components integrated with antibody arrays are used to explore cell signaling pathway kinetics. Separation of organelles and proteins is achieved by a new free flow isoelectric focusing device capable of achieving rapid separation. The device uses chemically modified hydrogel electrode regions as a simple, reliable means of applying high electric fields to micro free flow electrophoresis and avoiding bubble generation.

Selected Publications

Lu, H., Koo. L.Y., Wang, W.M., Lauffenburger ,D.A., Griffith, L.G., and Jensen, K.F. (2004)“Microfluidic Shear Devices for Quantitative Analysis of Cell Adhesion,” Analytical Chemistry 76, 5257-5264.

Lu, H.,Gaudet, S.,Schmidt, M.A.,and Jensen, K.F. (2004) “Microfluidic Device for Subcellular Organelle Sorting,” Anal Chemistry,76, 5705-5712.

Lu, H., and Jensen, K.F. (2004) “Cellular and Subcellular Analysis on Chip,” in Lab-on-Chips for Cellomics -Micro and Nanotechnologies for Life Science, H. Andersson and A. van den Berg (Eds.), Springer, Berlin, 2004, pp. 273-298

El-Ali, J., Gaudet, S., Gunther, A., Sorger, P.K. and Jensen, K.F. (2005) Cell stimulus and lysis in a microfluidic device with segmented gas-liquid flow. Anal Chem, 77, 3629-3636.

Lu, H., Schmidt, M.A. and Jensen, K.F. (2005) “Microfluidic Electroporation Device for Controlled Cell Lysis,” Lab Chip 5, 23-29.

Gervais, T and Jensen, K.F (2006) “Mass transport and surface reactions in microfluidic systems,” Chem. Eng. Sci. 61 1102–1121 (2006).

Gervais, T., El-Ali, J., Gunther, A. and Jensen, K.F. (2006) Flow-induced deformation of shallow microfluidic channels. Lab Chip, 6, 500-507.

Gervais, T. and. Jensen, K.F. (2006) Mass transport and surface reactions in microfluidic systems,” Chem. Eng. Sci, 61, 1102–1121.

El-Ali, J., Sorger, P.K. and Jensen, K.F. (2006) Cells on Chips. Nat Insight, in press.

Szita, N., Boccazzi, P., Zhang, Z., Boyle, P., Sinskey, A.J., and Jensen, K.F. (2005). “Development of a multiplexed microbioreactor system for high-throughput bioprocessing,” Lab Chip 5, 819–826.

Zhang, Z., Boccazzi, P., Choi, H.-G., Perozziello, G., Sinskey, A.J., and Jensen, K.F. (2006) “Microchemostat – microbial continuous culture in a polymer-based, instrumented microbioreactor, “Lab Chip in press