Bossone Research Center, Room 302, located at 32nd and Market Streets.
BIOMED Master's Thesis Defense
Maximizing Cell Growth per Passage Using Polystyrene Ribbons
Nazmiye Celik, MS Candidate, School of Biomedical Engineering, Science and Health Systems
Li-Hsin Han, PhD, Assistant Professor, Department of Mechanical Engineering and Mechanics, College of Engineering, Drexel University
Kara Spiller, PhD, Assistant Professor, School of Biomedical Engineering, Science and Health Systems, Drexel University
Tissue-engineering strategies often demand a large number of stem cells and cells passaging, which is usually achieved cell expansion on a two-dimensional (2D) substrate, such as a Petri dish or culturing flask. Stem cells on these 2D systems become confluence in about one or two weeks, reaching 3 to 5-fold maximum proliferation, and must be trypsinized, detached and re-plated to continue cell expansions. However, trypsinization exposes stem cells to biochemical and biophysical stresses that are known to accelerate cell senescence, phenotype changes, and the loss of stemness. In this work, I hypothesized that a cell-expanding strategy that maximizes the folds of cell proliferation before trypsinization may promote the phenotype stability of stem cells.
I developed a three-dimensional (3D) cell-expansion system using ribbon-shaped polystyrene, which is the same material used for making culture flasks. In contrast to traditional cell expansion, these microribbons (500 microns wide and 50 microns thick) provide a large surface area per weight to support high cell proliferation, enabling a maximum cell number per passage that is much higher than the traditional system (by more than 10 folds). Cells reaching confluence were re-suspended by trypsin following the similar protocols for the 2D cell expansion. I used human mesenchymal stem cells (MSC) as a model cell type to compare the differences between the results of my 3D cell expansion and that of the 2D cell expansion. These results include the MSC proliferation rate, change of gene expression post passaging, and the capacity for MSC to differentiate into bone and fat-like cells phenotypes.
The result of my study showed that the PS-ribbon is a novel biomaterial that provides a 3D environment for cell expansion with enabling continual cell proliferation, in the absence of the traditional cycles of trypsinization, cell detachment, and re-plating cycles. This study has shed light on a new type of cell expansion technology to enhance the quality of expanded stem cells, which may benefit the tissue engineering community as well as the biology research in general.