An attractive strategy for bone tissue engineering is the use of extracellular matrix (ECM) analogous biomaterials capable of governing biological response based on synthetic cell-ECM interactions. In this study, peptide amphiphiles (PAs) were investigated as an ECM-mimicking biomaterial to provide an instructive microenvironment for human mesenchymal stem cells (hMSCs) in an effort to guide osteogenic differentiation. PAs were biologically functionalized with ECM isolated ligand sequences (i.e. RGDS, DGEA), and the osteoinductive potential was studied with or without conditioned medium, containing the supplemental factors of dexamethasone, β-glycerol phosphate and ascorbic acid. It was hypothesized that the ligand-functionalized PAs would synergistically enhance osteogenic differentiation in combination with conditioned medium. Concurrently, comparative evaluations independent of osteogenic supplements investigated the differentiating potential of the functionalized PA scaffolds as promoted exclusively by the inscribed ligand signals, thus offering the potential for therapeutic effectiveness under physiological conditions. Osteoinductivity was assessed by histochemical staining for alkaline phosphatase (ALP) and quantitative real-time polymerase chain reaction analysis of key osteogenic markers. Both of the ligand-functionalized PAs were found to synergistically enhance the level of visualized ALP activity and osteogenic gene expression compared to the control surfaces lacking biofunctionality. Guided osteoinduction was also observed without supplemental aid on the PA scaffolds, but at a delayed response and not to the same phenotypic levels. Thus, the biomimetic PAs foster a symbiotic enhancement of osteogenic differentiation, demonstrating the potential of ligand-functionalized biomaterials for future bone tissue repair. © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.