Study On Enhanced Silk Fibroin/Poloxamer-sodium Alginate Hydrogels

Articular cartilage is mainly composed of chondrocytes and extracellular matrix.Articular cartilage injury can occur in different age groups for a variety of reasons.Degenerative osteoarthritis of the aged is always associated with varying degrees of articular cartilage injury.The commonly used clinical methods are frequently difficult to achieve satisfactory therapeutic outcomes.Tissue engineering methods involving biological materials,seed cells,and signaling molecules have been recognized as an alternative with clear clinical application prospects.Besides the wide use of porous solid scaffold materials in articular cartilage repair,hydrogels have also been largely employed.An attempt was made in this study to build a type of mechanically enhanced injectable thermosensitive hydrogel using silk fibroin and poloxamer-alginate copolymers,and intend to use them for articular cartilage repair.The optimized poloxamer-alginate and silk fibroin were combined to form hydrogels with a semi-interpenetrating network structure.The thermosensitive properties of these gels were regulated by their poloxamer component whereas the significantly enhanced mechanical properties for them were achieved by the physically crosslinked poloxamer-alginate network and the enzyme-mediated chemically crosslinked silk fibroin network.The amino-terminated poloxamer was first synthesized by substituting 4-nitrophenyl chloroformate and ethylenediamine sequentially,and then the amino terminal poloxamer was grafted onto the backbone of sodium alginate by EDC/NHS as catalysts.The structure of the product was confirmed by using infrared spectroscopy,nuclear magnetic resonance spectroscopy and an o-phthalaldehyde testing method.The results of the rheological measurements confirmed that the silk fibroin/poloxamer-sodium alginate has temperature sensitivity,mechanically enhanced properties and injectability under the conditions of physiological temperature and pH.MTT assay was used to test the cellular activity.Bone marrow mesenchymal stem cells(BMSCs)were selected as seed cells to further investigate the cytocompatibility of gels.Purified BMCSs were seeded on the gel surface or innside gels.Scanning electron microscopy was used to observe the growth of cells seeded in the gels,calcein-propidium iodide staining was used to stain the live cells and dead cells.Besides,alkaline phosphatase staining,and alizarin red staining were used to detect the differentiation ability of BMSCs.The optimized silk fibroin/poloxamer-alginate gel was found to have suitable pore size and porosity,and have significantly enhanced mechanical properties and degradation resistance compared to the single component gel.In addition,cell experiments show that the gel has good cell compatibility,and the seeded cells can grow normally inside the pores of the gels.Therefore,this type of hydrogel is expected to develop into an injectable material that can be used for articular cartilage repair given that more cell and animal experiments are further conducted.