Characterization of a Biomimetic Calcium-Deficient Hydroxyapatite-Bacterial Cellulose Composite

Bone is the second most implanted tissue next to blood causing approximately 2.2 million people to receive bone grafts each year. Developing safe synthetic bone grafts allows quick and safe restoration of bone function while avoiding the surgical risks associated with bone autografting (self donation), and risks of disease transmission and immunogenic response associated with allografts (bone donated from other humans) and xenografts (grafts derived from animal tissue). This dissertation entails the study and development of a novel potential synthetic bone graft consisting of a composite of calcium-deficient hydroxyapatite (CdHAP) biomimetically deposited in a bacterial cellulose (BC) hydrogel.

To determine which conditions provided optimum cellulose growth from Gluconacetobacter hansenii (ATCC 10821), a statistical analysis of the effects of different culture parameters was carried out. This utilized fractional factorial design which allowed a large number of factors to be tested using an abbreviated set of experiments. Statistical software was also used to process the data to determine which factors and factor interactions were significant to bacterial cellulose production.

Purified bacterial cellulose was mineralized by sequential incubations in solutions of calcium chloride followed by sodium phosphate dibasic. This material was characterized using X-Ray Diffractometry, Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, Electron Dispersive Spectroscopy, and mechanical testing. Characterization revealed that the CdHAP formed biomimetically in the BC in a manner similar to natural bone. It was also determined that the CdHAP had comparable structure, size, and composition to that found in natural bone.

An ideal bone replacement material will degrade after stimulating new osseous tissue production. A chemical modification of the cellulose was carried out with periodate oxidation to render it degradable in-vivo. The BC structure was preserved as well as its ability to mineralize CdHAP after periodate oxidation. This composite was characterized and its capacity to degrade was analyzed by subjecting the samples to a simulated aqueous physiological environment.

The last chapter discusses how the BC-CdHAP composite may have clinical use in the major bone grafting procedures currently being administered. Several surgeons were surveyed for this portion of the study to determine which grafts they used, the reasons for graft selection, and to obtain their opinion of the BC-CdHAP material. It was ultimately determined that the BC-CdHAP composite has ideal properties for dental bone grafting procedures including site extraction preservation and sinus lifts.