Biomedical subjects

Chia-Chi Ho

Publications and source records attributed to Chia-Chi Ho.

11 recordsLinked to original sources

PubMed2005

Spatially controlled co-culture of neurons and glial cells.

The ability to create and maintain neuron and glial cell co-cultures is important for neuronal regeneration as well as for fundamental studies on neuron and glial cell interactions. We demonstrate here a method for spatially controlling the arrangement of neurons and glial cells. Line patterns of cell resistant, poly(oligoethyleneglycol methacrylate-co-methacrylic acid), was microcontact printed on various substrates to spatially control the attachment of neurons. Neuron-like cells, PC12 and SH-SY5Y cells, were confined within the unprinted line patterns and extended neurites along the line patterns. Subsequent attachment of glial cells was accomplished by converting the originally cell-resistant line patterns of poly(oligoethyleneglycol methacrylate-co-methacrylic acid) to cell adhesive by electrostatic adsorption of cationic poly-lysine, chitosan, or poly(ethyleneimine). This method for creating patterned co-cultures of neuron and glial cells provides a useful tool for investigating neuron-glial cell interactions and has potential applications in the repair or regeneration of nervous systems.

Animals↗

PubMed2005

Cell motility assays on tissue culture dishes via non-invasive confinement and release of cells.

In vitro cell migration assays are useful for screening bioactive agents that regulate angiogenesis, tumor metastasis, would healing, and immune responses by effecting changes in the rate of cell migration. Here we have developed a noninvasive in vitro migration assay that operates through release of confluent groups of cells initially confined within patterns of cell-resistant polyelectrolyte. Cell-resistant patterns of polyelectrolyte, separating groups of confluent cells, are rendered cell adhesive by adsorption of a second, cell adhesive polyelectrolyte of opposite charge; thereby, resulting in migration of cells into the separating regions. By dynamically controlling cell-surface interactions through self-assembly of cell-adhesive and cell resistant polyelectrolytes, this method eliminates the need to mechanically wound cells, as is done in current cell migration assays. The utility of this technique in identifying molecules and mechanisms that regulate cell migration is demonstrated by its application as an assay for the effects of platelet derived growth factors, cytoskeleton disrupting agents, and Merlin overexpression, on the migration of NIH 3T3 fibroblasts.

Animals↗

PubMed2005

Liquid-core capsules via interfacial polymerization: a free-radical analogy of the nylon rope trick.

Liquid-core capsules have wide-ranging applications in the high-efficiency encapsulation and controlled release of drugs, dyes, enzymes, and other substrates. Their great utility has driven the rapid development of various preparation techniques. However, there remains no convenient technique for the preparation of submicrometer liquid-core capsules with shell thicknesses less than 100 nm. Here, we demonstrate a new interfacial free-radical polymerization approach for the straightforward preparation of liquid-core polymer capsules. Conceptually, this interfacial free-radical polymerization is analogous to the classical "nylon rope trick" wherein hydrophobic and hydrophilic monomers alternately copolymerize to constrain the polymerization at interfaces, but its free-radical mechanism allows precise control of initiation, which makes it possible to finely disperse the immiscible phases prior to polymerization.

Journal Article↗

PubMed2005

Biocompatible micropatterning of two different cell types.

The spatial arrangement of individual cell types can now be routinely controlled using soft-lithography-based micropatterning of complementary cell-adhesive and cell-resistant patterns. However, the application of these tools in tissue engineering to recreate tissue complexity in vitro has been hampered by the challenge of finding noncytotoxic procedures for converting complementary cell-resistant regions that define the arrangement of the first cell type into cell-adhesive regions to allow for the attachment of other cell types. A polyelectrolyte assembly approach is presented here for the first time, which allows for this noncytotoxic conversion and, thus, micropatterning of two different cell types, for example, endothelial cells and fibroblasts, on biodegradable substrates. The flexibility of this approach is further demonstrated by inducing organized capillary formation by endothelial cells on micropatterned lines followed by subsequent assembly of fibroblasts.

3T3 Cells↗

PubMed2005

Micropatterning proteins and cells on polylactic acid and poly(lactide-co-glycolide).

Techniques for micropatterning proteins and cells on biomaterials are important in tissue engineering applications. Here, we present a method for patterning proteins and cells on poly(lactic acid) (PLA) and poly(lactide-co-glycolide) (PLGA) substrates that are routinely used as scaffolds in engineering tissues. Poly(oligoethyleneglycol methacrylate) (poly-OEGMA) or poly(oligoethyleneglycol methacrylate-co-methacrylic acid) (poly(OEGMA-co-MA)) was microcontact printed onto substrates to create cell resistant areas. Proteins adsorbed onto the unprinted regions whereas the polymer printed regions effectively repel non-specific protein adsorption. NIH 3T3 fibroblasts remain confined within the patterns on the PLGA and PLA films for up to 2 weeks and aligned their actin cytoskeleton along the line patterns. In comparison to unpatterned cells, fibroblasts confined within line-shaped patterns show fewer actin filaments. This method for controlling the spatial morphology and distribution of cells on synthetic biomaterials could have significant applications in tissue engineering.

Adsorption↗

PubMed2005

Alteration of human neuroblastoma cell morphology and neurite extension with micropatterns.

The spatial orientation of nerve cells plays a pivotal role in nerve regeneration. Here we report a new method for regulating neuronal cell morphology and guiding neurite extension on standard tissue culture dishes. Random copolymers of oligoethyleneglycol methacrylate and methacrylic acid [poly(OEGMA-co-MA)], microcontact printed on standard tissue culture dishes, resist cell attachment and remain intact in serum-containing medium for up to 2 weeks. Cell viability assay of SH-SY5Y cells demonstrated that poly(OEGMA-co-MA) on the substrate or in solution has no cytotoxic effect. When retinoic acid was added to SH-SY5Y cells, they extended neurites along the line patterns that are significantly longer than cells cultured on non-patterned culture dishes. The ability to guide neurite extension with micrometer precision is valuable for guiding directional growth of neurites and path finding of regenerating nerves.

Actins↗

PubMed2004

Sugar-based microemulsion glass templates.

Complex fluids comprising of surfactants with water and/or oil form a rich variety of dynamic self-assembled structures, ranging from spherical swollen micelles, viscous rod-like micelles, and bicontinuous microemulsions to ordered liquid crystalline phases. The wide range of practical and specialized applications of complex fluids has made them the subject of intense research for many decades. Here, we demonstrate for the first time how bicontinuous microemulsions containing equal masses of oil and sugar can be driven to the glassy state without phase separation at ambient temperatures by controlled desiccation of sugar-rich microemulsions. The robust nanostructure of these microemulsion glasses allows polymerization of hydrophobic liquid monomers within the interstices of the glassy microemulsion template without macroscopic phase separation. Yet after polymerization, the sugar and surfactant template can be easily removed by dissolution in water.

Carbohydrates↗

PubMed2004

Micropatterning of proteins and mammalian cells on biomaterials.

Controlling the spatial organization of cells is vital in engineering tissues that require precisely defined cellular architectures. For example, functional nerves or blood vessels form only when groups of cells are organized and aligned in very specific geometries. Yet, scaffold designs incorporating spatially defined physical cues such as microscale surface topographies or spatial patterns of extracellular matrix to guide the spatial organization and behavior of cells cultured in vitro remain largely unexplored. Here we demonstrate a new approach for controlling the spatial organization, spreading, and orientation of cells on two micropatterned biomaterials: chitosan and gelatin. Biomaterials with grooves of defined width and depth were fabricated using a two-step soft lithography process. Selective attachment and spreading of cells within the grooves was ensured by covalently modifying the plateau regions with commercially available protein resistant triblock copolymers. Precise spatial control over cell spreading and orientation has been observed when human microvascular endothelial cells are cultured on these patterned biomaterials, suggesting the potential of this technique in creating tissue culture scaffolds with defined chemical and topographical features.

Biocompatible Materials↗

PubMed2003

Effect of membrane morphology on system capacity during normal flow microfiltration.

Understanding the effects of membrane fouling on system capacity is critical for the successful design and scale-up of microfiltration systems. The underlying morphology and structure of the microfiltration membrane can have a significant effect on system capacity by altering the rate and extent of fouling. Experimental data were obtained for system capacity during protein microfiltration using several model membranes with both homogeneous and composite structures. Data were compared with predictions of a new model that can account for both pore blockage and cake formation, and also includes the effects of membrane morphology on internal flow profiles within the membrane. Membranes with highly interconnected pores have a significantly higher capacity due to the reduction in flux decline arising from the fluid flow under and around any surface blockage. The model calculations are in good agreement with the flux decline data, allowing far more accurate predictions of system capacity than for the commonly used V(max) analysis.

Animals↗

PubMed2003

Geometric determinants of directional cell motility revealed using microcontact printing.

Mammalian cells redirect their movement in response to changes in the physical properties of their extracellular matrix (ECM) adhesive scaffolds, including changes in available substrate area, shape, or flexibility. Yet, little is known about the cell's ability to discriminate between different types of spatial signals. Here we utilize a soft-lithography-based, microcontact printing technology in combination with automated computerized image analysis to explore the relationship between ECM geometry and directional motility. When fibroblast cells were cultured on fibronectin-coated adhesive islands with the same area (900 micrometers2) but different geometric forms (square, triangle, pentagon, hexagon, trapezoid, various parallelograms) and aspect ratios, cells preferentially extended new lamellipodia from their corners. In addition, by imposing these simple geometric constraints through ECM, cells were directed to deposit new fibronectin fibrils in these same corner regions. These data indicate that mammalian cells can sense edges within ECM patterns that exhibit a wide range of angularity and that they use these spatial cues to guide where they will deposit ECM and extend new motile processes during the process of directional migration.

Animals↗

PubMed2002

Application of a pore-blockage--cake-filtration model to protein fouling during microfiltration.

Although protein fouling is a critical factor governing the performance of microfiltration systems, there have been relatively few studies comparing the fouling behavior of different proteins. Flux-decline data were obtained for the filtration of bovine serum albumin, lysozyme, pepsin, immunoglobulin G, and myoglobin through polycarbonate track-etch membranes. The data were analyzed using a recently developed model that accounts for simultaneous pore blockage and cake formation. The model was in very good agreement with the data for all five proteins, demonstrating the general applicability of this new theoretical framework. The initial fouling due to pore blockage is directly related to the concentration of protein aggregates in solution, which was measured independently by quasi-elastic light scattering. The results provide important insights into the mechanisms of protein fouling during microfiltration.

Adsorption↗