Seung Kyu Choi

Fabrication of nanostructures of polyethylene glycol for applications to protein adsorption and cell adhesion

A simple method was developed to fabricate polyethylene glycol (PEG) nanostructures using capillary lithography mediated by ultraviolet (UV) exposure. Acrylate-containing PEG monomers, such as PEG dimethacrylate (PEG-DMA, MW = 330), were photo-cross-linked under UV exposure to generate patterned structures. In comparison to unpatterned PEG films, hydrophobicity of PEG nanostructure modified surfaces was significantly enhanced. This could be attributed to trapped air in the nanostructures as supported by water contact angle measurements. Proteins (fibronectin, immunoglobulin, and albumin) and cells (fibroblasts and P19 EC cells) were examined on the modified surfaces to test for the level of protein adsorption and cell adhesion. It was found that proteins and cells preferred to adhere on nanostructured PEG surfaces in comparison to unpatterned PEG films; however, this level of adhesion was significantly lower than that of glass controls. These results suggest that capillary lithography can be used to fabricate PEG nanostructures capable of modifying protein and cell adhesive properties of surfaces.

Modulation of Adhesion and Growth of Cardiac Myocytes by Surface Nanotopography

We have introduced well-defined nanopillar arrays of polyethylene glycol (PEG) as a platform for studying the adhesion and growth of cultured cardiomyocytes. The nanopillar arrays were fabricated by using a simple molding technique involving the placement of a patterned polyurethane acrylate mold on top of a drop-dispensed ultraviolet (UV) curable PEG polymer followed by UV exposure and mold removal. The adhesion and growth of cardiomyocytes turned out be guided by an external nanotopography, which has been characterized in terms of cell morphology and cytoskeletal arrangement. In particular, the nanopillars provided guiding posts to both elongating filopodia and expanding lamellipodia. Interestingly, the 3D growth of cardiomyocytes was mediated by the increased hydrophobicity of the nanostructured PEG substrate, indicating that the cell adhesion and growth is very sensitive to the nanotopography. The precise nanostructures of PEG-based polymer with controlled geometrical features presented in this study not only open opportunities for understanding and tailoring cell adhesion and growth, but could serve as a template for better tissue engineering by controlling cellular activities at the molecular level

Micropatterning of cardiomyocytes using adhesion-resistant polymeric microstructures

This work describes a simple approach to patterned growth of cardiomyocytes with high activity aided by three-dimensional physical barrier of polyethylene glycol (PEG) microstructures. The morphology and mobility of patterned cardiomyocytes were analyzed with different topographical heights of the PEG barrier. It was found that isolated aggregates of cardiomyocytes showed various beating activities depending on the morphology and the number of cells. Furthermore, three-dimensionally grown cardiac muscle cells medicated by a higher physical barrier generated higher contraction force with faster beating frequency than those of cells attached to the collagen-coated surface on culture dish (control), suggesting that control over cell growth and shape would be critical for optimizing the activity and functions of patterned cardiomyocytes.

Three-dimensionally patterned cardiomyocytes with high activity for powering bio-hybrid microdevices

We have demonstrated a simple method for patterning cardiac muscle cells with high activity on a micron scale for powering bio-hybrid microdevices. The morphology and mobility of patterned cardiac muscle cells within micro wells were analyzed with different topographical heights of the barrier. We found that three-dimensionally grown cardiac cells mediated by a higher physical barrier generated higher contraction force with faster beating frequency than those of cells attached to the collagen-coated surface on the culture dish (control), suggesting that control over cell growth and shape would be critical for potential engineered cellular motors. Thus, the micro patterned cardiac muscle cells presented here would provide a primary platform for building up 3-D bioactuated microdevices including an engineered cell motor.