Nava showed that the osteogenic differentiation of hMSCs in hydrogels functionalized with phosphate groups can be attributed to serum protein adsorption.
N.R. Gandavarapu, P.D. Mariner, M.P. Schwartz, and K.S. Anseth, "Extracellular Matrix Protein Adsorption to Phosphate-Functionalized Gels from Serum Promotes Osteogenic Differentiation of Human Mesenchymal Stem Cells," Acta Biomaterialia (2012).