Enzymatic mineralization of gellan gum hydrogel for bone tissue-engineering applications and its enhancement by polydopamine

Abstract

Interest is growing in the use of hydrogels as bone tissue-engineering (TE) scaffolds due to advantages such as injectability and ease of incorporation of active substances such as enzymes. Hydrogels consisting of gellan gum (GG), an inexpensive calcium-crosslinkable polysaccharide, have been applied in cartilage TE. To improve GG suitability as a material for bone TE, alkaline phosphatase (ALP), an enzyme involved in mineralization of bone by cleaving phosphate from organic phosphate, was incorporated into GG hydrogels to induce mineralization with calcium phosphate (CaP). Incorporated ALP induced formation of apatite-like material on the submicron scale within GG gels, as shown by FTIR, SEM, EDS, XRD, ICP-OES, TGA and von Kossa staining. Increasing ALP concentration increased amounts of CaP as well as stiffness. Mineralized GG was able to withstand sterilization by autoclaving, although stiffness decreased. In addition, mineralizability and stiffness of GG was enhanced by the incorporation of polydopamine (PDA). Furthermore, mineralization of GG led to enhanced attachment and vitality of cells in vitro while cytocompatibility of the mineralized gels was comparable to one of the most commonly used bone substitute materials. The results proved that ALP-mediated enzymatic mineralization of GG could be enhanced by functionalization with PDA.

Modified gellan gum hydrogels for tissue engineering applications

“…Blending GG with other types of biomolecules (e.g. 40 polysaccharides and enyzmes) for TE applications have also been considered [75][76][77][78][79][80][81] .…”

Oxygen-Producing Gellan Gum Hydrogels for Dual Delivery of Either Oxygen or Peroxide with Doxorubicin

“…These applications include bone regeneration, 1 cartilage repair, 2 intervertebral disc regeneration, [3][4] neuronal cell culture [5][6][7] and spinal cord injury therapies. 8 The divalent calcium cation derived from calcium chloride is typically used to physically crosslink gellan gum into a hydrogel structure.…”

Tissue engineering with gellan gum

“…In most cases, GG products need to be sterilised prior to use in cell culture and TE. Various techniques are in use for this purpose including autoclaving [34][35][36] , ethylene oxide treatment 37 , microfiltration 38 , and antibiotic supplements 39 . Although no studies directly compare these methods with respect to their impacts on GG, equivalent investigations using other polysaccharides [40][41][42][43] and ECM materials 40,44,45 provide a good indication of the likely effects on GG.…”

“…For bone tissue, researchers have used combined blending and bioconditioning processes to mineralise GG scaffolds. Douglas et al mineralised GG scaffolds using the alkaline phosphatase enzyme to improve strength and stiffness of the material, as well as promote cell attachment and differentiation 35,77 . Douglas and others have also explored incorporating bioglass into GG hydrogels to improve mineralisation, bone regeneration and antibacterial properties 78,79 .…”