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Collagen films have been widely used in the field of biomedical engineering. However, the poor mechanical properties of collagen have limited its application. Here, rod-like cellulose nanocrystals (CNCs) were fabricated and used to reinforce collagen films. A series of collagen/CNCs films were prepared by collagen solution with CNCs suspensions homogeneously dispersed at CNCs: collagen weight ratios of 1, 3, 5, 7, and 10. The morphology of the resulting films was analyzed by scanning electron microscopy (SEM), the enhancement of the thermomechanical properties of the collagen/CNCs composites were demonstrated by thermal gravimetric analysis (TGA) and mechanical testing. Among the CNCs contents used, a loading of 7 wt % led to the maximum mechanical properties for the collagen/CNCs composite films. In addition, in vitro cell culture studies revealed that the CNCs have no negative effect on the cell morphology, viability, and proliferation and possess good biocompatibility. We conclude that the incorporation of CNCs is a simple and promising way to reinforce collagen films without impairing biocompatibility. This study demonstrates that the composite films show good potential for use in the field of skin tissue engineering.

Tissue-engineered dermis is thought to be the best treatment for skin defects; however, slow vascularization of these biomaterial scaffolds limits their clinical application. Exogenous administration of angiogenic growth factors is highly desirable for tissue regeneration. In this study, biodegradable gelatin microspheres (GMs) containing basic fibroblast growth factor (bFGF) were fabricated and incorporated into a porous collagen/cellulose nanocrystals (CNCs) scaffold, as a platform for long-term release and consequent angiogenic boosting. The physicochemical properties of these scaffolds were examined and the in vitro release pattern of bFGF from scaffolds was measured by ELISA. Collagen/CNCs scaffolds with and without bFGF-GMs were incubated with human umbilical vein endothelial cells for 1 week, results showed that the scaffolds with bFGF-GMs significantly augmented cell proliferation. Then, four different groups of scaffolds were implanted subcutaneously into Sprague-Dawley rats to study angiogenesis in vivo via macroscopic observation, and hematoxylin and eosin and immunohistochemical staining. The results suggested that the collagen/CNCs/bFGF-GMs scaffolds had a significantly higher number of newly formed and mature blood vessels, and the fastest degradation rate. This study demonstrated that collagen/CNCs/bFGF-GMs scaffolds have great potential in skin tissue engineering.

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Evidence indicates that microRNAs (miRNAs) play vital roles in regulating osteogenic differentiation and bone formation. Methods : Here, we show that a polyethyleneimine (PEI)-functionalized graphene oxide (GO) complex efficiently loaded with the miR-214 inhibitor is assembled into silk fibroin/hydroxyapatite (SF/HAP) scaffolds that spatially control the release of the miR-214 inhibitor. Results : SF/HAP/GO scaffolds with nanosized GO show high mechanical strength, and their hierarchical microporous structures promote cell adhesion and growth. The SF/HAP/GO-PEI scaffolds loaded with mir-214 inhibitor (SF/HAP/GPM) were tested for their ability to enhance osteogenic differentiation by inhibiting the expression of miR-214 while inversely increasing the expression of activating transcription factor 4 (ATF4) and activating the Akt and ERK1/2 signaling pathways in mouse osteoblastic cells (MC3T3-E1) in vitro . Similarly, the scaffolds activated the osteoblastic activity of endogenous osteoblast cells to repair critical-sized bone defects in rats without the need for loading osteoblast cells. Conclusion : This technology is used to increase osteogenic differentiation and mineralized bone formation in bone defects, which helps to achieve cell-free scaffold-based miRNA-inhibitor therapy for bone tissue engineering.