Numerous biodegradable hydrogels for cartilage regeneration have been widely used in the field of tissue engineering. However, to non-invasively monitor hydrogel degradation and efficiently evaluate cartilage restoration in situ is still challenging.Methods: A ultrasmall superparamagnetic iron oxide (USPIO)-labeled cellulose nanocrystal (CNC)/silk fibroin (SF)-blended hydrogel system was developed to monitor hydrogel degradation during cartilage regeneration. The physicochemical characterization and biocompatibility of the hydrogel were evaluated in vitro. The in vivo hydrogel degradation and cartilage regeneration of different implants were assessed using multiparametric magnetic resonance imaging (MRI) and further confirmed by histological analysis in a rabbit cartilage defect model for 3 months.Results: USPIO-labeled hydrogels showed sufficient MR contrast enhancement and retained stability without loss of the relaxation rate. Neither the mechanical properties of the hydrogels nor the proliferation of bone-marrow mesenchymal stem cells (BMSCs) were affected by USPIO labeling in vitro. CNC/SF hydrogels with BMSCs degraded more quickly than the acellular hydrogels as reflected by the MR relaxation rate trends in vivo. The morphology of neocartilage was noninvasively visualized by the three-dimensional water-selective cartilage MRI scan sequence, and the cartilage repair was further demonstrated by macroscopic and histological observations.Conclusion: This USPIO-labeled CNC/SF hydrogel system provides a new perspective on image-guided tissue engineering for cartilage regeneration.

Burn wounds are associated with a series of risks, such as infection and pathologic scar tissue formation, which significantly delay wound healing and lead to complications. In this study, we successfully fabricated a dextran-hyaluronic acid (Dex-HA) hydrogel enriched with sanguinarine (SA) incorporated into gelatin microspheres (GMs), which had high porosity, good swelling ratio, enhanced NIH-3T3 fibroblast cell proliferation, and sustained SA release profile. The in vitro degradation results indicate that the SA/GMs/Dex-HA hydrogel can be degraded. The in vitro antibacterial tests showed that the SA/GMs/Dex-HA hydrogel can inhibit methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli (E. coli). We evaluated the wound-healing effects and antibacterial properties of SA/GMs/Dex-HA hydrogels in a rat full-thickness burn infection model. The hematoxylin-eosin (H&E) and Masson's trichrome staining results of the SA/GMs/Dex-HA hydrogel showed that it improved re-epithelialization and enhanced extracellular matrix remodeling, and immunohistochemistry results showed that the expression of TGF-β1 and TNF-α was decreased, while the TGF-β3 expression was increased. Our findings suggest that the SA/GMs/Dex-HA hydrogel provides a potential way for infected burn treatment with high-quality and efficient scar inhibition.

Drug/gene co-delivery carriers are a promising strategy for cancer treatment.

The objective of this study was to develop heparin-conjugated strontium-substituted hydroxyapatite/silk fibroin (Sr-nHAp/SF-Hep) scaffold loaded bone morphogenetic proteins-2 (BMP-2) with sustained release to improve bone regeneration. The average pore diameters and porosity of Sr-nHAp/SF scaffolds were respectively approximately 150 μm and 90%. The mechanical properties and thermostability of the Sr-nHAp/SF scaffolds were significantly stronger than those of the SF scaffold. The weight of composite scaffolds is higher than that of the SF scaffold in simulated body fluids. The Sr-nHAp/SF scaffold exhibited excellent biological function of bone marrow mesenchymal stem cell (BMSC) proliferation and adhesion. The expression of related osteogenic genes, including osteocalcin, osteopontion, and alkaline phosphatase activity was elevated by Sr-nHAp/SF-Hep-BMP-2 scaffold, which promoted the differentiation of BMSCs into osteoblasts. In vivo results showed that Sr-nHAp/SF-Hep-BMP-2 scaffolds enhanced bone mineral density and improved new bone regeneration, which was accomplished through microcomputed tomography (micro-CT) and histological and histochemical staining analysis. These results demonstrated Sr-nHAp/SF-Hep-BMP-2 scaffolds with favorable biocompatibility and good mechanical properties have great potential to repair bone defects.

Thus, in this paper, we review the application and progress of non-viral gene vector therapy in bone regeneration.