Xuetao Shi

Myotube formation on gelatin nanofibers – Multi-walled carbon nanotubes hybrid scaffolds

Engineering functional muscle tissue requires the formation of densely packed, aligned, and mature myotubes. To enhance the formation of aligned myotubes with improved contractibility, we fabricated aligned electrospun gelatin multi-walled carbon nanotubes (MWNTs) hybrid fibers that were used as scaffolds for the growth of myoblasts (C2C12). The MWNTs significantly enhanced myotube formation by improving the mechanical properties of the resulting fibers and upregulated the activation of mechanotransduction related genes. In addition, the fibers enhanced the maturation of the myotubes and the amplitude of the myotube contractions under electrical stimulation (ES). Such hybrid material scaffolds may be useful to direct skeletal muscle cellular organization, improve cellular functionality and tissue formation.

Stretchable and micropatterned membrane for osteogenic differentation of stem cells.

Stem cells have emerged as potentially useful cells for regenerative medicine applications. To fully harness this potential, it is important to develop in vitro cell culture platforms with spatially regulated mechanical, chemical, and biological cues to induce the differentiation of stem cells. In this study, a cell culture platform was constructed that used polydopamine (PDA)-coated parafilm. The modified parafilm supports cell attachment and proliferation. In addition, because of the superb plasticity and ductility of the parafilm, it can be easily micropatterned to regulate the spatial arrangements of cells, and can exert different mechanical tensions. Specifically, we constructed a PDA-coated parafilm with grooved micropatterns to induce the osteogenic differentiation of stem cells. Adipose-derived mesenchymal stem cells that were cultured on the PDA-coated parafilm exhibited significantly higher osteogenic commitment in response to mechanical and spatial cues compared to the ones without stretch. Our findings may open new opportunities for inducing osteogenesis of stem cells in vitro using the platform that combines mechanical and spatial cues.

Gradient-Regulated Hydrogel for Interface Tissue Engineering: Steering Simultaneous Osteo/Chondrogenesis of Stem Cells on a Chip

Injury to articular cartilage, especially the defects induced by degenerative diseases has presented insurmountable challenges. Elaborating a replacement of articular cartilage using biomimic tissue-engineering strategies provides a promising remedy. However, none of the previous osteo/chondrogenic methodologies can not only simultaneously induce osteo/chondrogenesis of stem cells in one scaffolding niche, but also generate a biomimic interface between the formed osteogenic and chondrogenic zones. We report here an innovative method using biomicrofluidic techniques to simultaneously steer distinct specialized differentiation of stem cells into chondrocytes and osteoblasts in one hydrogel slab. Importantly, a gradient that mimics the interface of bone-to-cartilage was generated in the middle of the hydrogel slab. We compared this format with the conventional method for osteochondrogenesis; this format using the gradient-generating microfluidic device indicated outstanding superiorities in stem cell culture and differentiation. Our findings will have a major impact on the design of versatile biomicrofluidic devices for interfacial tissue regeneration.

Enhanced Osteogenesis by a Biomimic Pseudo‐Periosteum‐Involved Tissue Engineering Strategy

Elaborating a bone replacement using tissue-engineering strategies for bone repair seems to be a promising remedy. However, previous platforms are limited in constructing three-dimensional porous scaffolds and neglected the critical importance of periosteum (a pivotal source of osteogenic cells for bone regeneration). We report here an innovative method using the periosteum as a template to replicate its exquisite morphologies onto the surfaces of biomaterials. The precise topographic cues (grooved micropatterns) on the surface of collagen membrane inherited from the periosteum effectively directed cell alignment as the way of natural periosteum. Besides, we placed the stem-cell and endothelial-cell-laden collagen membrane (pseudo-periosteum) onto a three-dimensional porous scaffold. The pseudo-periosteum-covered scaffolds showed remarkable osteogenesis when compared with the pseudo-periosteum-free scaffolds, indicating the significant importance of pseudo-periosteum on bone regeneration. This study gives a novel concept for the construction of bone tissue engineering scaffold and may provide new insight for periosteum research.

Spatial coordination of cell orientation directed by nanoribbon sheets

Spatial coordination of cell orientation is of central importance in tissue/organ construction. In this study, we developed microfabricated poly(lactic-co-glycolic acid) (PLGA) nanoribbon sheets with unique structures, using spin-coating and micropatterning techniques, in order to generate a hierarchically assembled cellular structure consisting of murine skeletal myoblasts (C2C12). The nanoribbon sheets were composed of aligned PLGA nanoribbons in the center, and strips on four sides which take a role as bridges to connect and immobilize the aligned nanoribbons. Such unique structures facilitated the alignment of C2C12 cells into bilayer cell sheets, and cellular alignment was directed by the aligned direction of nanoribbons. The nanoribbon sheets also facilitated the construction of multilayer cell sheets with anisotropic (orthogonal) and isotropic (parallel) orientations. The enhanced expression of myogenic genes of C2C12 cells on the bilayer cell sheets demonstrated that the nanoribbons induced C2C12 cell differentiation into mature myoblasts. The micropatterned nanoribbon sheets may be a useful tool for directing cellular organization with defined alignment for regenerative medicine and drug screening applications.

Nanostructured Zr-Pd Metallic Glass Thin Film for Biochemical Applications

Zr-Pd metallic glassy thin films with a hierarchical nano-scale structure, produced by magnetron sputtering of the Zr and Pd powder mixture, demonstrate a unique combination of physical and biochemical properties. Thermal stability of the nano-structured glassy samples, their resistance to oxidation in dry air and phase transformation behavior are discussed in the present work. These binary alloy samples also show exceptionally high corrosion resistance and spontaneous passivation in a simulated body fluid. Experiments on the catalytic activity and biocompatibility of this nanostructured metallic glass indicate that this is a very suitable material for biochemical applications. Compared to the multicomponent alloys studied earlier this binary alloy has much simpler chemical composition, which makes preparation of the sample with defined stoichiometry easier, especially when the elements have different sputtering rates.

Microfluidic Generation of Polydopamine Gradients on Hydrophobic Surfaces

Engineered surface-bound molecular gradients are of great importance for a range of biological applications. In this paper, we fabricated a polydopamine gradient on a hydrophobic surface. A microfluidic device was used to generate a covalently conjugated gradient of polydopamine (PDA), which changed the wettabilty and the surface energy of the substrate. The gradient was subsequently used to enable the spatial deposition of adhesive proteins on the surface. When seeded with human adipose mesenchymal stem cells, the PDA-graded surface induced a gradient of cell adhesion and spreading. The PDA gradient developed in this study is a promising tool for controlling cellular behavior and may be useful in various biological applications.

Generation of microgrooved silica nanotube membranes with sustained drug delivery and cell contact guidance ability by using a Teflon microfluidic chip

Abstract Silica nanotubes have been extensively applied in the biomedical field. However, very little attention has been paid to the fabrication and application of micropatterned silica nanotubes. In the present study, microgrooved silica nanotube membranes were fabricated in situ by microgrooving silica-coated collagen hybrid fibril hydrogels in a Teflon microfluidic chip followed by calcination for removal of collagen fibrils. Scanning electron microscopy images showed that the resulting silica nanotube membranes displayed a typical microgroove/ridge surface topography with ∼50 μm microgroove width and ∼120 μm ridge width. They supported adsorption of bone morphogenetic protein 2 (BMP-2) and exhibited a sustained release behavior for BMP-2. After culturing with osteoblast MC3T3-E1 cells, they induced an enhanced osteoblast differentiation due to the release of biologically active BMP-2 and a strong contact guidance ability to directly align and elongate osteoblasts due to the presence of microgrooved surface topography, indicating their potential application as a multi-functional cell-supporting matrix for tissue generation.

One-step generation of engineered drug-laden poly(lactic-co-glycolic acid) micropatterned with Teflon chips for potential application in tendon restoration.

Regulating cellular behaviors such as cellular spatial arrangement and cellular phenotype is critical for managing tissue microstructure and biological function for engineered tissue regeneration. We herein pattern drug-laden poly(lactic-co-glycolic acid) (PLGA) into grooves using novel Teflon stamps (that possess excellent properties of resistance to harsh organic solvents and molecular adsorption) for engineered tendon-repair therapeutics. The drug release and biological properties of melatonin-laden PLGA grooved micropatterns are investigated. The results reveal that fibroblasts cultured on the melatonin-laden PLGA groove micropatterns not only display significant cell alignment that mimics the cell behavior in native tendon, but also promote the secretion of a major extracellular matrix in tendon, type I collagen, indicating great potential for the engineering of functional tendon regeneration.

Partial transfection of cells using laminar flows in microchannels

This manuscript describes a convenient method for partial transfection using a Y-shaped microchannel polydimethylsiloxane (PDMS)-glass chip and on-chip cationic lipid-mediated transfection. Enhanced green fluorescent protein genes (pEGFP-N2) were introduced into the COS-7 cells cultured in half of the channel, while red fluorescent protein genes (pDsRed-N1) were introduced into the cells cultured in another half of the channel. This on-chip partial transfection technique provides an avenue for the spatial control of transfection. It is possible to use this technique to perform parallel transfection on chips in order to study cell behaviors under two or more gene transfections in the same culture.