(162w) Engineering of Collagen/Heparin Microcarrier Coatings for Human Mesenchymal Stromal Cell Manufacturing

Layer-by-layer (LbL) assembly is a surface modification method that uses charged polymers to create alternating negative and positive layers on a surface. In this study, two different techniques are studied to evaluate their efficacy in creating LbL films on spherical microcarriers used in human mesenchymal stromal cell (hMSC) culture. Our group has previously shown that LbL films on flat surfaces provide a growth environment for hMSCs that improves cell proliferation, immunosuppression, and cytokine expression. This project will expand upon our previous results by scaling up hMSC cell culture. Instead of a flat film, microcarriers are used to perform cell cultures. Microcarriers provide a large surface area for cells to adhere to and are commonly used in bioreactors. The goal for this study is to create an easily scalable system to create LbL films of heparin and collagen on spherical microcarriers that are 125-220 µm in diameter.

The charged polymers used in this study are heparin (negative) and collagen (positive). A fluidized-bed (FB) system and a tangential flow filtration (TFF) system are separately studied. A total of six bilayers of collagen/heparin are assembled on microcarriers using the two systems and then characterized to observe the differences. The samples are characterized using three techniques – Scanning Electron Microscopy coupled with Energy-dispersive X-ray spectroscopy (SEM+EDX), Particle Size Analysis (PSA) and a Zeta Potential test (ZP). SEM+EDX are used to observe physical and chemical changes on the surface of individual microcarriers after LbL assembly. PSA is used observe the increase in sizes of the microcarriers. Finally, ZP is used after each monolayer application to analyze the surface charge and confirm that the heparin and collagen layers are forming as expected. The results of this study are expected to be useful in countering the negative effects of a common antiviral (Interferon-γ) used during the manufacture of hMSCs. The proposed cell-culture method using LbL assembly of collagen/heparin on microcarriers is hypothesized to double the proliferation of the cells.