Tissue Engineering of Intestine
1. Influence of Chemical and Physical Modification to Polydimethylsiloxane (PDMS) Surfaces on Adhesion of Small Intestinal Epithelial Cells
Polydimethylsiloxane (PDMS) silicone elastomer is extensively used in soft lithography processes to fabricate micro- or nano- scale systems for microfluidic or cell culture applications. Though PDMS is biocompatible, it is not an ideal material for cell culture due to its poor cell adhesion properties. PDMS surfaces were modified to promote intestinal cell adhesion, in the interest of testing feasibility of using microfabricated PDMS systems for Caco-2 cell culture. Chemical composition of PDMS (i.e. varying curing to mixing agent ratio, and oxidization of PDMS surface by oxygen plasma), surface treatment of PDMS by coating with charged molecules (i.e. poly-D-lysine, lecithin, a layer by layer coating), and deposition of extra-cellular matrix (ECM) proteins (i.e. laminin, fibronectin, collagen) were all found to influence the attachment and proliferation of Caco-2 cells.
Figure 1. AFM of PDMS with 10:1 mixing ratio, and PDMS after exposed to O2 plasma
2. Influence of Micro-well Biomimetic Topography on Intestinal Epithelial Caco-2 Cell Phenotype
The inner surface of the intestine contains a monolayer of enterocytes resting on a basement membrane with a convoluted topography consisting of finger-like projections (villi) and deep invaginations (crypts) on the order of hundreds of microns in dimension (Figure 2). The phenotype of small intestinal epithelial cells varies with position relative to this topographical structure. It has thus been hypothesized that crypt-villus micro-architecture may induce changes in small intestinal cell (i.e. Caco-2 cell) phenotype. A microfabrication approach was utilized to create topographic analogs of crypts on a polymer substrate (Figure 3) and a collagen substrate (Figure 3). The topography of the PDMS substrates (Figure 4) and collagen substrate (Figure 5) influenced cell spreading after seeding. The Caco-2 cells attached and spread faster and to a greater extent on flat surfaces than on those with micro-well structures. Substrate topography also affected cell metabolic activity; cells had higher initial mitochondrial activity when seeded on micro-well patterned PDMS substrates compared to flat substrates. The study will shed light on important topographical design properties for a scaffold for tissue engineered intestine.
Human Small Intestine
Figure 2 : Morphometric characteristic of normal human small intestine *.
( * source: abpi.org.uk )
Figure 3 : Layout of substrate with villus like topography (a) PDMS Substrate (b) Collagen
* to view cultured cell images
Mouse over to the images above. PDMS Substrate or Collagen image.