Both human embryonic stem (hES) cells and induced pluripotent stem (hiPS) cells can self-renew indefinitely in culture, however current methods to clonally grow them are inefficient and poorly-defined for genetic manipulation and therapeutic purposes. Here we develop the first chemically-defined, xeno-free, feeder-free synthetic substrates to support robust self-renewal of fully-dissociated hES and hiPS cells. Materials properties including wettability, surface topography, surface chemistry and indentation elastic modulus of all polymeric substrates were quantified using high-throughput methods to develop structure/function relationships between materials properties and biological performance. These analyses show that optimal hES cell substrates are generated from monomers with high acrylate content, have a moderate wettability, and employ integrin αvβ3 and αvβ5 engagement with adsorbed vitronectin to promote colony formation. The structure/function methodology employed herein provides a general framework for the combinatorial development of synthetic substrates for stem cell culture.

In this study, we investigated the molecular adhesion between the major constituents of cartilage extracellular matrix, namely, the highly negatively charged proteoglycan aggrecan and the type II/IX/XI fibrillar collagen network, in simulated physiological conditions. Colloidal force spectroscopy was applied to measure the maximum adhesion force and total adhesion energy between aggrecan end-attached spherical tips (end radius R ≈ 2.5 μm) and trypsin-treated cartilage disks with undamaged collagen networks. Studies were carried out in various aqueous solutions to reveal the physical factors that govern aggrecan–collagen adhesion. Increasing both ionic strength and [Ca2+] significantly increased adhesion, highlighting the importance of electrostatic repulsion and Ca2+-mediated ion bridging effects. In addition, we probed how partial enzymatic degradation of the collagen network, which simulates osteoarthritic conditions, affects the aggrecan–collagen interactions. Interestingly, we found a significant increase in aggrecan–collagen adhesion even when there were no detectable changes at the macro- or microscales. It is hypothesized that the aggrecan–collagen adhesion, together with aggrecan–aggrecan self-adhesion, works synergistically to determine the local molecular deformability and energy dissipation of the cartilage matrix, in turn, affecting its macroscopic tissue properties.