miR-29b-Loaded Gold Nanoparticles Targeting to the Endoplasmic Reticulum for Synergistic Promotion of Osteogenic Differentiation

Precise control of stem cells, such as human bone marrow-derived mesenchymal stem cells (hMSCs), is critical for the development of effective cellular therapies for tissue engineering and regeneration medicine. Emerging evidence suggests that several miRNAs act as key regulators of diverse biological processes, including differentiation of various stem cells. In this study, we have described a delivery system for miR-29b using PEI-capped gold nanoparticles (AuNPs) to synergistically promote osteoblastic differentiation. The cell proliferation assay revealed that AuNPs and AuNPs/miR-29b exert negligible cytotoxicity to hMSCs and MC3T3-E1 cells. With the assistance of AuNPs as a delivery vector, miR-29b could efficiently enter the cytoplasm and regulate osteogenesis. AuNPs/miR-29b more effectively promoted osteoblast differentiation and mineralization through induced the expression of osteogenesis genes (RUNX2, OPN, OCN, ALP) for the long-term, compared to the widely used commercial transfection reagent, Lipofectamine. With no obvious cytotoxicity, PEI-capped AuNPs showed great potential as an adequate miRNA vector for osteogenesis differentiation. Interestingly, we observed loading of AuNPs as well as AuNPs/miR-29b into the lumen of the endoplasmic reticulum (ER). Our findings collectively suggest that AuNPs, together with miR-29b, exert a synergistic promotory effect on osteogenic differentiation of hMSCs and MC3T3-E1 cells

Effective Spatial Separation of PC12 and NIH3T3 Cells by the Microgrooved Surface of Biocompatible Polymer Substrates

Most organs and tissues are composed of more than one type of cell that is spatially separated and located in different regions. This study used a microgrooved poly­(lactic-<i>co</i>-glycolic acid) (PLGA) substrate to guide two types of cocultured cells to two spatially separated regions. Specifically, PC12 pheochromocytoma cells are guided to the inside of microgrooves, whereas NIH3T3 fibroblasts are guided to the ridge area in between neighboring parallel microgrooves. In addition, the microgrooved structures can significantly promote the proliferation and neural differentiation of PC12 cells as well as the osteogenic differentiation of NIH3T3 cells. Therefore, the microgrooved PLGA surface with separated PC12 and NIH3T3 cells can serve as a potential model system for studying nerve reconstruction in bone-repairing scaffolds

Tough and Cell-Compatible Chitosan Physical Hydrogels for Mouse Bone Mesenchymal Stem Cells in Vitro

Most hydrogels involve synthetic polymers and organic cross-linkers that cannot simultaneously fulfill the mechanical and cell-compatibility requirements of biomedical applications. We prepared a new type of chitosan physical hydrogel with various degrees of deacetylation (<i>DD</i>s) via the heterogeneous deacetylation of nanoporous chitin hydrogels under mild conditions. The <i>DD</i> of the chitosan physical hydrogels ranged from 56 to 99%, and the hydrogels were transparent and mechanically strong because of the extra intra- and intermolecular hydrogen bonding interactions between the amino and hydroxyl groups on the nearby chitosan nanofibrils. The tensile strength and Young’s modulus of the chitosan physical hydrogels were 3.6 and 7.9 MPa, respectively, for a <i>DD</i> of 56% and increased to 12.1 and 92.0 MPa for a <i>DD</i> of 99% in a swelling equilibrium state. In vitro studies demonstrated that mouse bone mesenchymal stem cells (mBMSCs) cultured on chitosan physical hydrogels had better adhesion and proliferation than those cultured on chitin hydrogels. In particular, the chitosan physical hydrogels promoted the differentiation of the mBMSCs into epidermal cells in vitro. These materials are promising candidates for applications such as stem cell research, cell therapy, and tissue engineering

Reinforced Mechanical Properties and Tunable Biodegradability in Nanoporous Cellulose Gels: Poly(l‑lactide-<i>co</i>-caprolactone) Nanocomposites

Incorporation of nanofillers into aliphatic polyesters is a convenient approach to create new nanomaterials with significantly reinforced mechanical properties compared to the neat polymers or conventional composites. Nanoporous cellulose gels (NCG) prepared from aqueous alkali hydroxide/urea solutions can act as alternative reinforcement nanomaterials for polymers with improved mechanical properties. We report a simple and versatile process for the fabrication of NCG/poly­(l-lactide-<i>co</i>-caprolactone) (NCG/P­(LLA-<i>co</i>-CL) nanocomposites through in situ ring-opening polymerization of l-lactide (LLA) and ε-caprolactone (ε-CL) monomers in the NCG. The volume fraction of the NCG in the nanocomposites was tunable and ranged from 4.5% to 37%. Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and differential scanning calorimetry (DSC) results indicated that P­(LLA-<i>co</i>-CL) were synthesized within the NCG and partially grafted onto the surface of the cellulose nanofibrils. The glass-transition temperature (<i>T</i>_g) of the NCG/P­(LLA-<i>co</i>-CL) nanocomposites could be altered by varying the molar ratio of LLA/ε-CL and was affected by the volume fraction of NCG. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) images confirmed that the interconnected nanofibrillar cellulose network structure of the NCG was finely distributed and preserved in the P­(LLA-<i>co</i>-CL) matrix after polymerization. The dynamic mechanical analysis (DMA) results showed remarkable reinforcement of the tensile storage modulus (<i>E</i>′) of the P­(LLA-<i>co</i>-CL) nanocomposites in the presence of NCG, especially above the <i>T</i>_g of the P­(LLA-<i>co</i>-CL). The modified percolation model agreed well with the mechanical properties of the NCG/P­(LLA-<i>co</i>-CL) nanocomposites. The introduction of NCG into the P­(LLA-<i>co</i>-CL) matrix improved the mechanical properties and thermal stability of the NCG/P­(LLA-<i>co</i>-CL) nanocomposites. Moreover, the NCG/P­(LLA-<i>co</i>-CL) nanocomposites have tunable biodegradability and biocompatibility and potential applications in tissue engineering repair, biomedical implants, and packing