Tomography and static-mechanical properties of adherent cells.

A tomography approach is used to reconstruct 3D cell shapes and, simultaneously, the shapes/positions of the nuclei within these cells. Subjecting the cells to well-defined microconfinements of various diameters allow for relating the steady-state shapes of cells to their static-mechanical properties. The observed shapes show striking regularities between different cell types and all fit to a model that takes into account the cell membrane, cortical actin, and the nucleus.

Design, Implementation, Simulation, and Visualization of a Highly Efficient RIM Microfluidic Mixer for Rapid Freeze-Quench of Biological Samples.

Rapid freeze-quench (RFQ) trapping of short-lived reaction intermediates for spectroscopic study plays an important role in the characterization of biological reactions. Recently there has been considerable effort to achieve submillisecond reaction deadtimes. We present here a new, robust, high-velocity microfluidic mixer that enables such rapid freeze-quenching.

Carboxybetaine methacrylate polymers offer robust, long-term protection against cell adhesion.

Films of poly(carboxybetaine methacrylate), poly(CBMA), grafted onto microetched gold slides are effective in preventing nonspecific adhesion of cells of different types. The degree of adhesion resistance is comparable to that achieved with the self-assembled monolayers, SAMs, of oligo(ethylene glycol) alkanethiolates. In sharp contrast to the SAMs, however, substrates protected with poly(CBMA) can be stored in dry state without losing their protective properties for periods up to 2 weeks.

Short-term molecular polarization of cells on symmetric and asymmetric micropatterns.

The ability of cells to sense geometrical/physical constraints of local environment is important for cell movements during development, immune surveillance, and in cancer invasion. In this paper, we quantify "front-rear" polarization - the crucial step in initiating cell migration - based on cytoskeleton and substrate adhesion anisotropy in micropatterned cells of well-defined shapes. We then show that the general viewpoint that asymmetric cell shape is one of the defining characteristics of polarized cells is incomplete.

Nanoparticle-based solution deposition of gold films supporting bioresistant SAMs.

Thin films of gold on glass are prepared by solution deposition of functionalized gold nanoparticles followed by thermal treatment. The processed films adhere strongly to glass without any adhesion layers and can be micropatterned/microetched without delamination from the substrate. The formation of self-assembled monolayers (SAMs) of oligo(ethylene glycol) alkane thiols (EG SAMs) renders the films resistant to cell adhesion and allows for cell patterning.

Cell motility on micropatterned treadmills and tracks.

Surfaces micropatterned with disjointed cell adhesive/non-adhesive regions allow for precise control of cell shape, internal organization and function. In particular, substrates prepared by the reaction-diffusion ASoMic (nisotropic lid roetching) method localize cells onto transparent micro-islands or tracks surrounded by an opaque, adhesion-resistant background. ASoMic is compatible with several important imaging modalities ( wide-field, fluorescent, TIRF and confocal microscopies), and can be used to study and quantify various intracellular and cellular processes related to cell motility.

Application of the lag-after-pulsed-separation (LAPS) flow meter to different protein solutions.

A lag after pulsed separation (LAPS) meter was previously developed to measure flow rates of protein solutions. The LAPS meter operates on the time-of-flight principle. An upstream event (electrophoretic concentration of the particles in one section of the device) is detected downstream (by change in ac resistance).