Biotechnology & Bioengineering II 3627-Pos Board B488 Effects of Biomaterial Chemical Heterogeneity on Fibrinogen Activity- Platelet Adhesion Relationships Christopher A. Siedlecki, Bryan M. Scheetz, Li-Chong Xu. Pennsylvania State University, Hershey, PA, USA. Fibrinogen adsorbed on material surfaces undergoes conformational changes that expose the platelet binding epitope located in the gamma-chain dodecapeptide. Circulating blood platelets bind to this exposed region, leading to platelet adhesion and activation, eventually forming a surface-induced thrombus. We have devel- oped an AFM technique utilizing an antibody-modified probe that allows us to calculate the probability of this epitope being available following fibrinogen ad- sorption to solid surfaces, and have shown that the time-dependent changes in this probability of antibody binding correlate with temporal changes in platelet ad- hesion to materials. Recently, we have begun to explore how well this probability of adhesion correlates to platelet adhesion across a variety of different polymeric biomaterials. Results demonstrate that there is a strong relationship between this probability and measured platelet adhesion for 3 different homopolymer materials (figure 1), but two different phase-separated polyurethane (PU) materials possessing heterogeneous surface chemistries appear to deviate from this probability/adhesion re- lationship. These results suggest that the ~50 to 100 nm sized phases in PU materials may affect the ability of platelets to bind to fibrinogen in a manner that leads to the im- proved blood compatibility seen with PU materials. 3628-Pos Board B489 High Throughput Screening Methodology to Probe Cell Deformability Dongping Qi, Amy Rowat. Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, CA, USA. Cell and nucleus mechanical properties are implicated in a wide range of bio- logical contexts: for example, the multi-lobed nucleus of neutrophil cells cor- relates with increased cell deformability; cancer cells show decreased stiffness compared to benign cells. The mechanical properties of cells and nuclei could thus be valuable label-free markers for a cell’s physiological state. Most con- ventional techniques used to study cell mechanics are labor-intensive and lim- ited in throughput - typically < 10-20 cell types can be probed within a reasonable timeframe. Here we introduce a novel high throughput method to probe cell deformability. The device uses filtration to simultaneously probe several hundreds of different cell types; the entire assay is complete within ~30 min. The key component of the technique is a porous membrane interfacing with a 96- or 384-well plate; cells are placed on top of this membrane; an ap- plied pressure generates physical forces on them, causing the cells to pass through the membrane pores and into the collection well; the number of pas- saged cells is counted and provides a measure of cell mechanical properties. We characterize the number of passaged cells as a function of initial loading density, pressure amplitude and duration, membrane pore size, and cell deform- ability; in parallel we develop a theoretical description of cell passage building on theories describing bulk filtration. In proof of concept experiments, we apply the method to probe differentiated versus non-differentiated human promyelo- cytic leukemia (HL60) cells: a larger number of differentiated, neutrophil-type cells passaged compared to the non-differentiated cells; these results are con- sistent with previous literature. We also show differences in cell deformability due to cytoskeletal perturbing drugs. These results validate the feasibility of this technique for high throughput screening of cells based on their deformabil- ity, for example, against a library of drugs. 3629-Pos Board B490 Frustrated Differentiation of Mesenchymal Stem Cell Cultured on Microelastically-Patterned Photocurable Gelatinous Gels Satoru Kidoaki, Shuhei Jinnouchi. IMCE, Kyushu University, Fukuoka, Japan. Cells sense surface rigidity of culture substrate, interpret the mechanical condition as mechano-signals, and modulate their functions and behaviors in- cluding proliferation, differentiation, motility, etc. In relation to this, matrix- elasticity-dependent lineage specification of mesenchymal stem cells (MSCs) has recently drawn growing attention in the stem cell mechanobilogy. Discher’s group has reported that MSCs exhibit differentiation to different lineage after one week culture on hydrogel surface with a certain level of elasticity. On the other hands, if we could prepare the culture substrate in which both high and low elasticity region coexist, and could induce the alternate movement of MSCs between those regions in a certain culture period, how should the lin- eage specification occur? In general, since the adherent cells show directional movement toward harder region, so-called mechanotaxis, MSCs should accu- mulate in hard region with enough large area. However, if the area of hard re- gion is set to be smaller than single cell spread area, MSCs will fail to completely spread in the hard region and return to soft region. The returned MSC will try to re-enter to hard region according to the mechanotaxis charac- ter, so MSC will keep on moving between hard and soft regions on such kind of microelastically-patterned gel surface. In this study, we aimed to confirm what effect on lineage specification should appear for the MSCs which experienced the alternative movement between hard and soft region on the microelasticity patterned gels. To design such microelasticity-patterned gels, we have applied the photolithographic microelasticity patterning using photoculable gelatins. To the MSCs cultured with the above-mentioned process, immunofluorescence observation of selection markers and differentiation markers showed significant tendency of simultaneous suppression of differentiation for neurogenic, myo- genic, and osteogenic lineage. The functional mode of ‘‘frustrated differentia- tion’’ of MSCs is discussed. 3630-Pos Board B491 Cell Aspect Ratio Alters Stem Cell Traction Stresses and Lineage Ludovic G. Vincent 1 , TayChor Yong 2 , Juan Carlos del Alamo 1 , Lay Poh Tan 2 , Adam J. Engler 1 . 1 University of California San Diego, La Jolla, CA, USA, 2 Nanyang Technical University, Singapore, Singapore. Adult mesenchymal stem cells (MSCs) ‘‘feel’’ the stiffness of their environ- ment and differentiate in response to it; thus aberrant stiffness resulting from fibrosis in muscle dystrophies could misdirect MSCs into the wrong lineage. Conversely, MSCs have been shown to respond in a myosin-dependent manner to adipogenic and osteogenic media when cell spread area changes from 10 3 to 10 4 mm 2 or when cultured in specific shapes, e.g. circles versus rectangles, and polygons, respectively. When both cues are present in a disparate fashion, e.g. highly elongated cells similar to muscle despite the presence of an abnormally stiff microenvironment, we hypothesized that a myosin contraction-dependent balance could induce a subset of MSCs to differentiate in to a muscle-like phe- notype despite residing in a dystrophic-like stiffness. To regulate MSC mor- phology, we patterned fibronectin in shapes of varying aspect ratios but common area on polyacrylamide substrates of known stiffness. MSCs spread to the patterns and localized their focal adhesion in a stiffness and shape- dependent manner. Using traction force microscopy, we found that strain en- ergy from cell-generated forces scaled with stiffness, but decreased as a func- tion of cell elongation with isotropic cell patterns producing the highest contractile energy in contrast to our hypothesis. Muscle-specific myosin heavy chain (mMHC), an indicator of early muscle differentiation, also was expressed in a stiffness and elongation dependent manner. On muscle-like stiffness of 11 kiloPascals (kPa), cells with only minimal elongation, i.e. 1:1 and 3:1 patterns, expressed mMHC most strongly. In contrast on osteogenic-like matrices of 34 kPa, highest MHC expression corresponded to the most elongated patterns. These shape- and stiffness-dependent lineage changes with muscle markers correlated to contractility-based observations suggest that muscle induction may be possible in non-permissive stiffer environments and could prove bene- ficial to treat fibrotic muscle diseases. 3631-Pos Board B492 Engineered Microenvironments to Study Mechanisms of Tissue Tropism in Metastasis Erinn Dandley 1 , Nathan Colon 1 , Shireen Rudina 2 , Shannon Alford 2 , Shelly Peyton 1 . 1 University of Massachusetts, Amherst, Amherst, MA, USA, 2 Massachusetts Institute of Technology, Cambridge, MA, USA. Breast cancer is the second leading cause of cancer death. With 90% of breast cancer deaths associated with metastasis of the original cancer to other organs, metastasis is a vital area of research. Breast cancer preferentially me- tastasizes to a subset of organs, including the brain, bone, and lung. Different clinical subtypes of breast cancer have different metastatic profiles to these very diverse organs; however, there is no biophysical explanation for meta- static site preference. Through the use of engineered metastatic microenvi- ronments (EMMs), we are investigating how the physiochemical properties of these tissues influence metastatic site preference. Our EMMs consist of cover slips, which present the characteristic adhesive matrix proteins of brain, bone, and lung. Utilizing these EMMs, we have observed that the EMM pro- tein specificity regulates cell area, shape, adhesion, migration speed, and 716a Wednesday, February 29, 2012