Development of a Dynamic Cell Patterning Strategy on a Hyaluronic Acid Hydrogel

Cell behavior is influenced to a large extent by the surrounding microenvironment. Therefore, in the body, the cellular microenvironment is highly controlled with cells growing within well-defined tissue architectures. However, traditional culture techniques allow only for the random placement of cells onto culture dishes and biomaterials. Cell micropatterning strategies aim to control the spatial localization of cells on their underlying material and in relation to other cells. Developing such strategies provides us with tools necessary to eventually fabricate the highly-controlled microenvironments found in multicellular organisms. Employing natural extracellular matrix (ECM) materials in patterning techniques can increase biocompatibility. In the future, with such technologies, we can hope to conduct novel studies in cell biology or optimize cell behavior and function towards the development of new cell-based devices and tissue engineering constructs. Herein, a novel cell patterning platform was developed on a hydrogel base of crosslinked hyaluronic acid (HA). Hydrogels are often employed in tissue engineering due to their ability to mimic the physicochemical properties of natural tissues. HA is a polymer present in all connective tissues. Cell-adhesive regions on the hydrogel were created using the RGDS peptide sequence, found within the cell-adhesive ECM protein, fibronectin. The peptide was bound to a 2-nitrobenzyl “caging group” via a photolabile bond to render the peptide light-responsive. Finally, this “caged” peptide was covalently bound to the hydrogel to form a novel HA hydrogel with a cell non-adhesive surface which could be activated with near-UV light to become adhesive. In this way, we successfully formed chemically patterned cell-adhesive regions on a HA hydrogel using light as a stimulus to form controlled cell patterns. While the majority of cell patterning strategies to date are limited to patterning one cell population and cannot be changed with time, our strategy was novel in using small, adhesive, caged peptides combined with multiple, aligned light exposure steps to allow for dynamic chemical cell patterning on a hydrogel. Multiple cell populations, even held apart from one another, were successfully patterned on the same hydrogel. Furthermore, cell patterns were deliberately modified with time to direct cell growth and/or migration on the hydrogel base