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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 the substrates with a controlled wettability in studying 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 a water contact angle of 40~70° and 70~90°, respectively. Hydrophilic mixed SAMs with a water contact angle of 20~70° also promoted the spreading of both hMSCs and mMSCs. Both hMSCs and mMSCs proliferation was most favored on hydrophilic SAMs with a water contact angle around 70°. In addition, a moderate hydrophilic surface (with a contact angle of 40~90° for hMSCs and 70° for mMSCs) promoted osteogenic differentiation in the presence of biological stimuli. Hydrophilic mixed SAMs with a moderate wettability tended to promote the expression of αvβ1 integrin of MSCs, indicating that the tunable wettability of the mixed SAMs may guide osteogenesis through mediating the αvβ1 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.

Titanium (Ti) alloy implants can repair bone defects at load-bearing sites. However, they mechanically mismatch with the natural bone and lack customized adaption with the irregularly major-sized load-bearing bone defects, resulting in the failure of implant fixation. Mineralized collagen (MC), a building block in bone, can induce angiogenesis and osteogenesis, and 3D printing technology can be employed to prepare scaffolds with an overall shape customized to the bone defect. Hence, we induced the formation of MC, made of hydroxyapatite (HAp) nanocrystals and collagen fibers, in 3D-printed porous Ti6Al4V (PT) scaffolds through in situ biomimetic mineralization. The resultant MC/PT scaffolds exhibited a bone-like Young’s modulus and were customized to the anatomical contour of actual bone defects of rabbit model. We found that the biocompatibility and osteogenic differentiation are best when the mass ratio between HAp nanocrystals and collagen fibers is 1 in MC. We then implanted the MC/PT scaffolds into the customized radius defect rabbit model and found that the MC/PT scaffolds significantly improved the vascularized bone tissue formation and integration between new bone and the implants. Therefore, a combination of 3D printing and biomimetic mineralization could lead to customized 3D PT scaffolds for enhanced angiogenesis, osteogenesis, and osteointegration. Such scaffolds represent novel patient-specific implants for precisely repairing irregular major-sized load-bearing bone defects.