**3.5 Tissue engineering approaches**

Tissue engineering is a regenerative medicine discipline that combines growth factors, cells and scaffolds to restore, preserve or improve damaged tissues or whole organs [32]. Growth factors are proteins that promote and activate cell proliferation by stimulating angiogenesis and the transcription of certain genes. Growth factors such as epidermal growth factor (EGF), platelet-derived growth factor (PDGF), fibroblast growth factor (FGF), transforming growth factor beta (TGF) and vascular endothelial growth factor (VEGF) are examples of growth factors. All of these growth factors have been shown to be beneficial in DFU tissue healing [33]. Cells obtained from bone marrow and umbilical cord blood such as mesenchymal stem cells (MSCs), fibroblasts and keratinocytes have also been employed for tissue repair in DFU [33, 34, 35]. Furthermore, biomaterials derived from natural resources such as collagen, hyaluronic acid, fibrin, chitosan and alginate, as well as synthetic materials such as poly (acrylic acid) (PAA), polyglycolic acid (PGA), PCL-poly (ethylene glycol) (PEG), gelatin methacrylate (GelMA) have been used as hydrogels, bandages, foam and films in DFU treatment. These biomaterials have been recommended for used in DFU treatment because of their ease of degradation, good biocompatibility and resistance to the scaffolding material [36].
