Recent progress of biomimetic motions-from microscopic micro/nanomotors to macroscopic actuators and soft robotics.

Motion is a basic behavioral attribute of organisms, and it is a behavioral response of organisms to the external environment and internal state changes. Materials with switchable mechanical properties are widespread in living organisms and play crucial roles in the motion of organisms. Therefore, significant efforts have been made toward mimicking such architectures and motion behaviors by making full use of the properties of stimulus-responsive materials to design smart materials/machines with specific functions. In recent years, the biomimetic motions based on micro/nanomotors, actuators and soft robots constructed from smart response materials have been developed gradually. However, a comprehensive discussion on various categories of biomimetic motions in this field is still missing. This review aims to provide such a panoramic overview. From nano-to macroscales, we summarize various biomimetic motions based on micro/nanomotors, actuators and soft robotics. For each biomimetic motion, we discuss the driving modes and the key functions. The challenges and opportunities of biomimetic motions are also discussed. With rapidly increasing innovation, advanced, intelligent and multifunctional biomimetic motions based on micro/nanomotors, actuators and soft robotics will certainly bring profound impacts and changes for human life in the near future.

Enhanced cellular osteogenic differentiation on CoFe2O4/P(VDF-TrFE) nanocomposite coatings under static magnetic field.

Cellular responses can be regulated and manipulated through combining stimuli-responsive biomaterial with external stimulus. In this present, the magneto-responsive CoFe2O4/P(VDF-TrFE) nanocomposite coatings were designed to understand cell behaviors of preosteoblasts, as well as get insight into the underlying mechanism of osteogenic differentiation under static magnetic field (SMF). CoFe2O4/P(VDF-TrFE) nanocomposite coatings with differential magnetic property (low, medium and high magnetization) were prepared by incorporation of different mass fraction of CoFe2O4 nanoparticles (6%, 13 %, 20 %) into P(VDF-TrFE) matrix. Cell experiments indicated that all nanocomposite coatings with the assistance of SMF could promote the cell attachment, proliferation and osteogenic differentiation of MC3T3-E1 cells. Among different nanocomposite coatings, low magnetization coating (6%) showed a higher ALP activity and gene expression of Runx2, Col-I, OCN. Molecular biology assays demonstrated that the combination of nanocomposite coatings and SMF could significantly up-regulate the expression level of α2ß1 integrin and p-ERK. Whereas, the addition of inhibitor U0126 down-regulated sharply the expression level of p-ERK, which indicated that cellular osteogenic differentiation of MC3T3-E1 cells was governed through α2ß1 integrin-mediated MEK/ERK signaling pathways during CoFe2O4/P(VDF-TrFE) nanocomposite coatings were combined with SMF. This work provided a promising strategy to enhance cellular osteogenic differentiation through a remote-control manner, which exhibited great potential in the application of bone tissue repair and regeneration.

Magnetic-Field-Assisted Cellular Osteogenic Differentiation on Magnetic Zinc Ferrite Coatings via MEK/ERK Signaling Pathways.

Combining an external stimulus and stimuli-responsive biomaterials can regulate cellular behaviors. In this paper, a magneto-responsive zinc ferrite (ZnFe2O4) coating was designed to gain insight into the preosteoblasts behaviors and osteogenic differentiation mechanism under a static magnetic field (SMF). ZnFe2O4 coatings with distinct magnetization (low, medium, and high magnetizations) were prepared by being annealed at different temperatures. Cellular biology experiments indicated that all ZnFe2O4 coatings with the assistance of SMF could promote the early proliferation (3 days) and osteogenic differentiation of MC3T3-E1 cells. Among different ZnFe2O4 samples, low and medium magnetization of ZnFe2O4 showed a higher osteogenesis-related gene expression (Runx2, Col-I, OCN) than that of high magnetization ZnFe2O4 under SMF, while cellular adhesion and proliferation cultured on different ZnFe2O4 samples presented insignificant differences. Molecular biology tests showed that the combination of ferromagnetic ZnFe2O4 and SMF could significantly improve the expression level of α2ß1 integrin and p-ERK. However, the addition of the inhibitor U0126 sharply reduced the expression level of p-ERK, which indicated that α2ß1 integrin-mediated MEK/ERK signaling pathways play a key role in SMF-assisted cellular osteogenic differentiation over ZnFe2O4 coatings. This work provides an attractive strategy to enhance cellular osteogenic differentiation in a remote-control way, which exhibited enormous potential in the field of bone tissue repair and regeneration.