Directing cell migration and organization via nanocrater-patterned cell-repellent interfaces.

Although adhesive interactions between cells and nanostructured interfaces have been studied extensively, there is a paucity of data on how nanostructured interfaces repel cells by directing cell migration and cell-colony organization. Here, by using multiphoton ablation lithography to pattern surfaces with nanoscale craters of various aspect ratios and pitches, we show that the surfaces altered the cells focal-adhesion size and distribution, thus affecting cell morphology, migration and ultimately localization. We also show that nanocrater pitch can disrupt the formation of mature focal adhesions to favour the migration of cells towards higher-pitched regions, which present increased planar area for the formation of stable focal adhesions. Moreover, by designing surfaces with variable pitch but constant nanocrater dimensions, we were able to create circular and striped cellular patterns. Our surface-patterning approach, which does not involve chemical treatments and can be applied to various materials, represents a simple method to control cell behaviour on surfaces

Recombinant phage coated 1D Al2O3 nanostructures for controlling the adhesion and proliferation of endothelial cells

A novel synthesis of a nanostructured cell adhesive surface is investigated for future stent developments. One-dimensional (1D) Al2O3 nanostructures were prepared by chemical vapor deposition of a single source precursor. Afterwards, recombinant filamentous bacteriophages which display a short binding motif with a cell adhesive peptide (RGD) on p3 and p8 proteins were immobilized on these 1D Al2O3 nanostructures by a simple dip-coating process to study the cellular response of human endothelial EA hy.926. While the cell density decreased on as-deposited 1D Al2O3 nanostructures, we observed enhanced cell proliferation and cell-cell interaction on recombinant phage overcoated 1D Al2O3 nanostructures. The recombinant phage overcoating also supports an isotropic cell spreading rather than elongated cell morphology as we observed on as-deposited Al2O3 1D nanostructures

Quantitative analysis of single bacterial chemotaxis using a linear concentration gradient microchannel

A microfluidic device to quantify bacterial chemotaxis has been proposed, which generates a linear concentration gradient of chemoattractant in the main channel only by convective and molecular diffusion, and which enables the bacteria to enter the main channel in a single file by hydrodynamic focusing technique. The trajectory of each bacterium in response to the concentration gradient of chemoattractant is photographed by a CCD camera and its velocity is acquired by a simple PTV (Particle Tracking Velocimetry) algorithm. An advantage of this assay is to measure the velocity of a single bacterium and to quantify the degree of chemotaxis by analyzing the frequency of velocities concurrently. Thus, the parameter characterizing the motility of wild-type Escherichia coli strain RP437 in response to various concentration gradients of L-aspartate is obtained in such a manner that the degree of bacterial chemotaxis is quantified on the basis of a newly proposed Migration Index

Biomaterials Design for Control of Cell Behavior by Femtosecond Laser Processing

The last decade has seen exciting and unprecedented work at the interface between biology and materials science, particularly in the form of exquisite control of cell attachment, shape, traction, motility, and differentiation. Recent progress in developing techniques for microfabrication of biomaterials helps recapitulate many extracellular matrix (ECM) cues, making them progressively more useful for applications in biology and tissue engineering. This dissertation presents a study of femtosecond laser assisted micro- and nano-fabrication applicable for the biomaterials design aiming at achieving deliberate control of the cell behavior. Cell mechanics connected to cell alignment and migration, from speculation of cell response to the biomaterials surface to control of the response by topographic and chemical patterns, was studied. Cell migration is an essential cellular process for a variety of physiological and pathological phenomena. Migration of leukocytes mediates phagocytic and immune responses. Migration of fibroblasts, vascular endothelial cells, and osteoblasts contributes to wound healing and tissue regeneration, and tumor cell migration is essential to metastasis. The cell migration process can be initiated by mechanical and chemical cues from the extracellular microenvironment. Factors affecting cell migration can be both soluble and insoluble macromolecules that comprise the ECM or mediate extracellular communication. We apply femtosecond laser induced two-photon polymerization and multiphoton laser ablation lithography to fabricate precisely defined two-dimensional patterned surface in nanometer to micrometer length scale and three-dimensional filamentous materials to be used in studies addressing fundamental issues concerning control of cell adhesion and migration. We studied microscale topographical patterned surface for cell alignment and migration. Anisotropic micronscale ridge/groove patterned surfaces are powerful cues to control cell shape and to enhance or obstruct cell migration. However, they have limited ability to independently control the size and the distribution of the cell adhesive domains and the ligand density. Thus, we applied chemically and topographically patterned surfaces in the nanoscale to control cell adhesion and guide directional cell migration to overcome constraints of microscale patterns. During cell migration, contractile force is needed to move the cell body forward. We also studied the contractile force exerted by an individual locomoting cell using fiber scaffolds

Genetically Engineered Phage Induced Selective H9c2 Cardiomyocytes Patterning in PDMS Microgrooves

A micro-patterned cell adhesive surface was prepared for future design of medical devices. One-dimensional polydimethylsiloxane (PDMS) micro-patterns were prepared by a photolithography process. Afterwards, recombinant filamentous phages that displayed a short binding motif with a cell adhesive peptide (-RGD-) on p8 proteins were immobilized on PDMS microgrooves through simple contact printing to study the cellular response of rat H9c2 cardiomyocyte. While the cell density decreased on PDMS micro-patterns, we observed enhanced cell proliferation and cell to surface interaction on the RGD-phage coated PDMS microgrooves. The RGD-phage coating also supported a better alignment of cell spreading rather than isotropic cell growths as we observed on non-pattered PDMS surface

Collective Migration of Lens Epithelial Cell Induced by Differential Microscale Groove Patterns

Herein, a micro-patterned cell adhesive surface is prepared for the future design of medical devices. One-dimensional polydimethylsiloxane (PDMS) micro patterns were prepared by a photolithography process. We investigated the effect of microscale topographical patterned surfaces on decreasing the collective cell migration rate. PDMS substrates were prepared through soft lithography using Si molds fabricated by photolithography. Afterwards, we observed the collective cell migration of human lens epithelial cells (B-3) on various groove/ridge patterns and evaluated the migration rate to determine the pattern most effective in slowing down the cell sheet spreading speed. Microgroove patterns were variable, with widths of 3, 5, and 10 µm. After the seeding, time-lapse images were taken under controlled cell culturing conditions. Cell sheet borders were drawn in order to assess collective migration rate. Our experiments revealed that the topographical patterned surfaces could be applied to intraocular lenses to prevent or slow the development of posterior capsular opacification (PCO) by delaying the growth and spread of human lens epithelial cells