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Surface Patterning (Publications)

Parylene Peel-Off Arrays to Study Tumor Cell-Cell Interactions

Microenvironmental conditions, such as cell-cell interactions, have been known to influence cell behavior and may be involved in cancer progression. However the underlying biological mechanisms are poorly understood. We have developed a simple micropatterning approach utilizing a parylene peel-off template for controlling cell-cell contact in a reproducible manner. This has enabled the systematic investigation into the role of cell-cell interactions in tumorigenesis.

Marked Glass Surfaces for Identifying and Studying Individual Particles

We use patterned glass surfaces to immobilize pre-treated biomass particles that are rich in cellulose. By dividing a glass cover slip into more than a hundred identifiable areas, we can not only count the total number of immobilized particles, but also address individual particles of interest, and observe them using optical microscopy, as well as scanning electron microscopy.

Patterning Cell Arrays Using a Versatile Polymer Template

Cell-cell interactions play a critical role in tissue homeostasis, and dysregulation of this interplay may contribute to cancer initiation and progression. The goal of this study is to create tailored, cell-patterned surfaces to study the angiogenic capability of tumor cells in the absence and presence of cell-cell interactions. To this end, we fabricated a versatile polymer template on a glass cover slip that enables the patterning individual cells and clusters in a well-defined manner. Our polymer template offers several advantages over the widely popular polydimethylsiloxane (PDMS) used in micro-patterning.

Micropatterned Substrates with Improved Uniformity of Deposition for DNA Microarrays

Biomolecular arrays have become a core technology used in numerous fields for parallel analysis. However, it has become obvious that current microarrays are hindered by methodological and technological barriers that limit their sensitivity, reproducibility, and therefore their utility. A fundamental problem with DNA microarrays is the relative insensitivity in detecting weakly expressed transcripts; this is especially significant when examining gene expression in complex tissues. While it has been proposed that a marked improvement in the detection limit of microarrays could be achieved if a uniform DNA layer can be spotted, the issue of its implementation has not been fully addressed. In an effort to resolve this problem, we have fabricated micropatterned substrates for the uniform deposition of DNA with a polymer lift-off technique. We pursued a methodology compatible with existing microarray technologies, which constrained the substrate area where the probe DNA were spotted. This yields a uniform layer of deposited DNA and improves the microarray data reproducibility between replicates on a single slide, and also across multiple slides.

Micrometer-Sized Supported Lipid Bilayer Arrays for Bacterial Toxin Binding Studies

We report the use of micron-sized lipid domains to assay the binding of bacterial toxins via total internal reflection fluorescence microscopy (TIRFM). Supported lipid bilayer (SLB) patterns containing either ganglioside GT1b or GM1 were formed on substrates by vesicle fusion followed by polymer lift-off. The ganglioside-populated arrays were then exposed to either Cholera toxin subunit B (CTB) or Tetanus toxin fragment C (TTC). Binding was assayed by TIRFM and constants were extracted from a logistic model. Patterning of SLBs inside microfluidic channels allowed preparation of lipid domains with different compositions on a single device, which were used to achieve segregation from a binary mixture of the toxin fragments.

Polymer Dry-Lift Off Patterning of Cells and Proteins

Precise placement of biochemicals on device structures and controlling of the cell culture environment are important for tissue engineering, sensors and fundamental studies of cell behavior. We present a novel dry lift-off method that allows precise patterning of chemically sensitive biological materials on a variety of surfaces with lateral dimensions of 100nm. Our dry lift-off technique uses a conformal Parylene layer, which is a pinhole-free and biocompatible vapor phase deposited inert polymer. This layer is photolithographically patterned using standard ultraviolet sensitive photoresists, and dry etching in a reactive ion etch chamber using oxygen plasma.