Enhancement of biomimetic enzymatic mineralization of gellan gum polysaccharide hydrogels by plant-derived gallotannins

Douglas, Timothy and Keppler, Julia K. and Vandrovcova, Marta and Plnencer, Martin and Beranova, Jana and Feuereisen, Michelle and Parakhonskiy, Bogdan V and Svenskaya, Yulia and Atkin, Vsevolod and Ivanova, Anna and Ricquier, Patrick and Balcaen, Lieve and Vanhaecke, Frank and Schieber, Andreas and Bacakova, Lucie and Skirtach, Andre G. (2020) Enhancement of biomimetic enzymatic mineralization of gellan gum polysaccharide hydrogels by plant-derived gallotannins. International Journal of Molecular Sciences, 21 (7): 2315. ISSN 1422-0067

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Abstract

Mineralization of hydrogel biomaterials with calcium phosphate (CaP) is considered advantageous for bone regeneration. Mineralization can be both induced by the enzyme alkaline phosphatase (ALP) and promoted by calcium-binding biomolecules, such as plant-derived polyphenols. In this study, ALP-loaded gellan gum (GG) hydrogels were enriched with gallotannins, a subclass of polyphenols. Five preparations were compared, namely three tannic acids of differing molecular weight (MW), pentagalloyl glucose (PGG), and a gallotannin-rich extract from mango kernel (Mangifera indica L.). Certain gallotannin preparations promoted mineralization to a greater degree than others. The various gallotannin preparations bound differently to ALP and influenced the size of aggregates of ALP, which may be related to ability to promote mineralization. Human osteoblast-like Saos-2 cells grew in eluate from mineralized hydrogels. Gallotannin incorporation impeded cell growth on hydrogels and did not impart antibacterial activity. In conclusion, gallotannin incorporation aided mineralization but reduced cytocompatibility.