Directing the fate of human and mouse mesenchymal stem cells by hydroxyl-methyl mixed self-assembled monolayers with varying wettability

Self-assembled monolayers (SAMs) of alkanethiols on gold have been employed as model substrates to investigate the effects of surface chemistry on cell behavior. However, few studies were dedicated to substrates with controlled wettability in studying the stem cell fate. Here, mixed hydroxyl ( OH) and methyl (-CH3) terminated SAMs were prepared to form substrates with varying wettability, which were used to study the effects of wettability on the adhesion, spreading, proliferation and osteogenic differentiation of mesenchymal stem cells (MSCs) from human and mouse origins. The numbers of adhered human fetal MSCs (hMSCs) and mouse bone marrow MSCs (mMSCs) were maximized on -OH/-CH3 mixed SAMs with water contact angles of 40-70 degrees and 70-90 degrees, respectively. Hydrophilic mixed SAMs with a water contact angle of 20-70 degrees also promoted the spreading of both hMSCs and mMSCs. Proliferation of both hMSCs and mMSCs was most favored on hydrophilic SAMs with a water contact angle around 70 degrees. In addition, a moderate hydrophilic surface (with a contact angle of 40-90 degrees for hMSCs and 70 degrees for mMSCs) promoted osteogenic differentiation in the presence of biological stimuli. Hydrophilic mixed SAMs with a moderate wettability tended to promote the expression of alpha(v)beta(1). integrin of MSCs, indicating that the tunable wettability of the mixed SAMs may guide osteogenesis through mediating the alpha(v)beta(1) integrin signaling pathway. Our work can direct the design of biomaterials with controllable wettability to promote the adhesion, proliferation and differentiation of MSCs from different sources.