Preparation And Properties Of Bacterial Cellulose/Hydroxyapatite Composites

Hydroxyapatite(HAp)is the main inorganic component of bones and teeth.Due to its biological activity,biocompatibility and osteoconductivity,HAp is widely used in tissue engineering.Despite that HAp can significantly promote the adhesion,proliferation and differentiation of bone cells due to its large specific surface area,and porous structure,the disadvantages such as high brittleness and low bending strength limits its biomedical applications.This problem,however,can be effectively solved by combining hydroxyapatite with biopolymer materials such as cellulose.At present,many studies have combined bacterial cellulose(BC)with HAp to prepare composite materials,which found that BC/HAp composite materials not only integrate the characteristics of the two materials,but also have excellent synergistic properties.The conventional method fabricates this composite by biomimetic mineralization,which takes a long time with unsatisfactory mechanical properties and biocompatibility.In this study,we deposited hydroxyapatite on bacterial cellulose matrix materials by in-situ calcium ion activation mediated bionic mineralization method and in situ biological mineralization method,respectively,which provides new ideas and methods for the development of new organic/inorganic composite as materials for tissue engineering.The contents are as follows:(1)Using calcium gluconate as the carbon source,we prepared the calcium-containing BC nanocomposite by the microbial in-situ fermentation method,and then prepared the BC/HAp nanocomposite by the biomimetic mineralization method.The results show that a large number of inorganic substances were deposited on the surface of the calcium-activated bacterial cellulose after 3 days of mineralization in the simulated body fluids,which was faster than that in the direct mineralization process of cellulose.Meanwhile,compared with common mineralized cellulose,the tensile strength and Young's modulus of CBC are increased by 49.2% and 63.8%.Cytocompatibility experiments show that the composite material significantly promotes the growth of bone cells.(2)In situ synthesis of BC/HAP composites was achieved by adding simulated body fluid in the fermentation and metabolic environment of Acetobacter xylinum.This is accomplished by integrating two separate steps into one,i.e.,the crystallization of cellulose and hydroxyapatite,enabling efficient preparation of mineralized bacterial cellulose within 48 hours.The results show that the tensile strength and Young's modulus of MBC are up to 13.11 MPa and 90.41 MPa.Meanwhile,compared with CBC,MBC could significantly promote the growth and proliferation of osteocytes.This method provides a new idea for the preparation of novel organic/inorganic composite as functional materials.