Green Synthesis of Bioactive Hydroxyapatite/Cellulose Composites from Food Industrial Wastes

Abstract

This work aimed at conversion of worthless indurtial wastes to valuable product. Herein, bioactive composites based on bacterial cellulose (BC) and eggshell or eggshell-derived hydroxyapatite (HAp) were prepared by a green method using Gluconacetobacter xylinum bacteria. The effect of addition of eggshell (BC/Eg) and eggshell-derived HAp (BC/HAp-Eg) on the bacterial cellulose yield, biodegradation and biocompatibility was studied. For comparison, HAp derived from chemical precursors was synthesized (BC/HAp-ch). The resultant composites were characterized by XRD, FTIR, and SEM/EDX. Furthermore, the biodegradation and bioactivity were assessed in SBF, and the cell viability was studied against oral normal cells. The results showed that the productivity of BC applied HAp-derived eggshell (1.83 g/L) was higher than that of using (1.37 g/L). Interestingly, the eggshell was converted to Ca3(PO4)2 during incubation in the bacterial culture medium, while Ca3(PO4)2 was formed as a secondary phase when using either eggshell-derived HAp or chemically-derived. The in vitro bioactivity test in SBF showed that all composites were induced the formation of a bone-like apatite layer on their surface with Ca/P ratio, 1.49, 1.35, and 1.41 for BC/Eg, BC/HAp-ch, and BC/HAp-Eg, respectively, near to the ratio in the natural HAp. Finally, the in vitro cell viability test was confirmed good biocompatibility against the composites. However, at high sample concentration (250 µg/mL), BC/HA-Eg showed the higher cell viability (95.2%) than that of BC/Eg (80.5%) and BC/HA-ch (86.2%). In conclusion, eggshell waste could be used directly with bacterial cellulose to produce bioactive composites without the need to convert it to HAp which reduced the cost of production and thus has a higher economic return. Obiviously, eggshell waste can act as calcium, organic matter source, pH preservation, nuterilizing agent along with potential instead of costly buffering agent in the BC culture medium and further for increased the BC production.