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Title:   Author  item
                                            KRESS, HOLGER - Yale Universityitem
                                            PARK, JASON - Yale Universityitem
                                            MEJEAN, CECILE - Yale Universityitem
                                            FORSTER, JASON - Yale Universityitem
                                            PARK, J - Yale Universityitem
                                            Walse, Spenceritem
                                            WEINER, ORIAN - University Of San Franciscoitem
                                            FAHMY, TAREK - Yale Universityitem
                                            DUFRESNE, ERIC - Yale University
  Submitted to: Nature Methods
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 10/15/2009
                                    Publication  Date: 11/15/2009
                                    Citation: Kress, H., Park, J., Mejean, C.O., Forster, J.D., Park, J., Walse, S.S., Weiner, O.D., Fahmy, T.M., Dufresne, E.R. 2009. Cell stimulation with optically manipulated microsources. Nature Methods. 6:905-909.Interpretive Summary: Over the past quarter century, the characterization of natural strategies for intra-organism chemical communication has been a focus of intense research. The concentration gradient of the signalling molecule typically plays a very important role in the communication process. Here we present a study that reinforces this concept and we present a new strategy for cell stimulation with a high degree of chemical, spatial and temporal flexibility. This technique is based on optically manipulated microsources - microparticles that provide a controlled release of soluble molecules. Multiple microsources are individually trapped and independently manipulated with holographic optical tweezers.  We demonstrate this method by inducing chemotaxis in single neutrophils. Microsources releasing the chemoattractant formyl-Methionine-Leucine-Phenylalanine (fMLP) were fabricated from poly-lactic-co-glycolic acid (PLGA). These microsources release fMLP in a sustained fashion and at rates which are suitable to induce attraction.
                                Technical Abstract: Many cells are sensitive to spatial and temporal heterogeneities in concentrations of molecules. Polarization of tissues and cells in molecular gradients plays a critical role for a large variety of biological processes including embryogenesis, and the response of immune cells to chemical ques. The investigation of these phenomena requires control over the chemical microenvironment of cells. Here we present a technique to set up molecular concentration patterns that are chemically, spatially and temporally flexible. Our strategy uses optically manipulated microsources which steadily release molecules. Our technique enables the control of concentrations of soluble molecules over length scales down to about 1 micrometer at frequencies up to 20 Hz. We demonstrate this technique by inducing directed cell polarization and migration of single neutrophils with optically manipulated microparticles emitting a peptide stimulus.


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