An Insulin-like Growth Factor-1 Conjugated Bombyx mori Silk Fibroin Film for Diabetic Wound Healing: Fabrication, Physicochemical Property Characterization, and Dosage Optimization In Vitro and In Vivo.

This study aimed to develop a silk fibroin (SF)-film for the treatment of chronic diabetic wounds. Silk fibroin was purified through a newly developed heating degumming (HD) process and casted on a hydrophobic surface to form SF-films. The process allowed the fabricated film to achieve a 42% increase in transparency and a 32% higher proliferation rate for BALB/3T3 fibroblasts compared to that obtained by conventional alkaline degumming treatment. Fourier transform infrared analysis demonstrated that secondary structure was retained in both HD- and alkaline degumming-derived SF preparations, although the crystallinity of beta-sheet in SF-film after the HD processing was slightly increased. This study also investigated whether conjugating insulin-like growth factor-1 (IGF-1) would promote diabetic wound healing and what the optimal dosage is. Using BALB/3T3 cells grown in hyperglycemic medium as a model, it was demonstrated that the optimal IGF-1 dosage to promote the cell growth was approximately 0.65 pmol. Further analysis of wound healing in a diabetic mouse model indicated that SF-film loaded with 3.25 pmol of IGF-1 showed significantly superior wound closure, a 13% increase at the 13th day after treatment relative to treatment with 65 pmol of free IGF-1. Improvement in diabetic wound healing was exerted synergistically by SF-film and IGF-1, as reflected by parameters including levels of re-epithelialization, epithelial tissue area, and angiogenesis. Finally, IGF-1 increased the epithelial tissue area and micro-vessel formation in a dose-dependent manner in a low dosage range (3.25 pmol) when loaded to SF-films. Together, these results strongly suggest that SF-film produced using HD and loaded with a low dosage of IGF-1 is a promising dressing for diabetic wound therapy.

Growth factor-loaded microspheres in mPEG-polypeptide hydrogel system for articular cartilage repair.

We developed an injectable hydrogel system with a sustained release of TGF-ß3 through growth factor-loaded microsphere to mimic the cartilage-like microenvironment. Poly(lactic-co-glycolic acid) (PLGA) microspheres incorporated in three dimensional (3D) scaffolds were chosen because of its regulatory approval, good biodegradability, and acting as carriers with sustained release behavior. We evaluated sustained release of TGF-ß3 by PLGA microspheres encapsulated in methoxy poly(ethylene glycol)-poly(alanine) (mPA) hydrogels and the resulting enhanced chondrogenic effects. We reported here the effect of the proposed system for sustained release of growth factors on chondrogenesis in cartilage regeneration. PLGA microspheres were used in our thermosensitive mPA hydrogel system with bovine serum albumin as a stabilizing and protecting agent for the emulsion and TGF-ß3 enabling sustained release. Gelation, structural properties, and in-vitro release of this composite, that is, microspheres in hydrogel, system were investigated. Using PLGA microspheres to carry growth factors could complement the mPA hydrogel's ability to provide an excellent 3D microenvironment for the promotion of chondrogenic phenotype as compared the systems using mPA hydrogel or microspheres alone. Our study demonstrated that this synthesized composite hydrogel system is capable of modulating the biosynthetic and differentiation activities of chondrocytes. The sustained release of TGF-ß3 in this novel hydrogel system could improve biomedical applicability of mPEG-polypeptide scaffolds. The distinctive local growth factor delivery system successfully combined the use of both polymers to be a suitable candidate for prolonged articular cartilage regeneration.