Nanocellulose reinforced gellan gum hydrogels as potential biological substitutes for annulus fibrosus tissue regeneration

Intervertebral disc (IVD) degeneration is related to both structural damage and aging. Annulus fibrosus (AF) defects such as annular tears, herniation and discectomy require novel strategies to functionally repair AF tissue. An ideal construct will repair the AF by providing physical and biological support and by facilitating regeneration. The present strategy proposes a gellan gum-based construct reinforced with cellulose nanocrystals (nCell) as a biological self-gelling AF substitute. Nanocomposite hydrogels were fabricated and characterized for their swelling capacity and stability and physico-chemical properties. Rheological evaluation on the nanocomposites demonstrated the GGMA reinforcement with nCell and thus matrix entanglements with higher stiffness upon ionic crosslinking.  Compressive mechanical tests demonstrate values close to those of the human AF tissue. Furthermore,cell culture studies by means of gel loading with bovine AF cells indicated that the construct promoted cell viability and a physiologically relevant morphology for up to fourteen days in vitro.