(5db) Engineering Optimal Cell Culture Platform Using Micro- and Nanotechnology

The microenvironment in living tissues comprises numerous cells, extracellular matrix (ECM) proteins and a variety of soluble and ECM bound factors. The ECM with which cells interact often includes topography at the nanoscale and provides, in concert with the spatio-temporally arranged signaling molecules and external stimuli, cues for cell adhesion, migration, proliferation and differentiation. Through the ECM, small fluid flows called interstitial flows, driven by dynamic stress, help to transport nutrients and play an important role in tissue maintenance and pathobiology. Knowledge of these interactions is crucial to the understanding of many fundamental biological questions and to the design of medical devices. This fact brings up the need to investigate cell-substrate interactions at the nanoscale in a dynamic environment. It is thus important to engineer dynamic 3D cell culture platform with nanostructures for advanced studies of cell-substrate interactions.

Based on polymer thin film technology, I have developed a cost-effective technique to generate a large nanopatterned surface from small nanostructured patterns, so that enough cells can be seeded for subsequent biochemical and molecular biology analyses. Taking advantage of polymer thin film and microcontact printing technologies, a simple technique has been developed to embed nanostructures into polymeric microfluidic platform. Moreover, I have also invented a biologically benign technique to process and assemble polymeric structures at the micro-/nanoscale. By using supercritical fluids (e.g., CO₂, N₂), the degree of enhanced chain mobility can be controlled to result in entanglement or patterning of surface chains without altering the integrity of the substrate. With this technique biomolecules and even cells can be incorporated into polymeric micro-/nanodevices without damaging their bioactivity. Preliminary studies with human mesenchymal stem cells (hMSCs) on the multifunctional microfluidic platform show that the nanotopography, flow-induced mechanical stress and chemical cue play a role in attachment, migration, spreading, and gene expression of hMSCs.

Equipped with tools to precisely control topographical, chemical and mechanical cues on cell culture, I am able to systematically investigate how these cues affect proliferation and differentiation of stem cells. In particular, I am interested in the expansion of hematopoietic stems cells (HSCs). I am expecting to a clear picture of the expansion performance of HSCs in the microfluidic cell culture platform with respect to the phenotypic analysis and engraftment assay. I hope to develop a clinically relevant culture technology for fully realizing the potential of HSC transplantation. Beyond expansion of HSCs, the broad objective of this research is to create an optimal microenvironment that can regulate the fate of stem cells and eventually expand specific stem cell phenotypes for clinical applications.