Authors:	Tolba, Emad
Title:	Bioactive polyphosphate-based biomaterials : an approach towards improved bone replacement implants
Online publication date:	16-Nov-2016
Year of first publication:	2016
Language:	english
Abstract:	New strategies for regeneration of damaged or diseased bone tissue are urgently needed because of difficulties and limitations in conventional therapies for repairing bone defects. Bone tissue engineering is a relatively new method for clinical treatment of massive bone injuries and deficiencies. The concept behind this approach is to deliver osteogenic cells and growth factors to injure site using an artificial matrix called scaffold. Therefore, there is an ever-growing need to design and develop bioactive scaffolding materials that provide the appropriate physical, chemical and biological microenvironments for guiding properly the cells during the regeneration process. Recently, inorganic polyphosphate (polyP), as a potent inducer for osteogenic cell activities, has become one of the most interesting research directions in bone tissue regeneration based on its capability to play numerous functions both in the extracellular and in the intracellular space. To date, there have been many studies dealing with this issue, but the results obtained are somewhat controversial. The mechanisms whereby inorganic polyP induces mineralization of hard tissues likely depend on a number of factors or conditions. In this PhD thesis, calcium polyphosphate (Ca-polyP) nanoparticles were prepared from sodium polyphosphate (Na-polyP) via a calcium/sodium ion exchange in aqueous solution at room temperature and used in cell culture experiments. The results indicate that exogenously administered Ca-polyP granules or nanoparticles indeed significantly promote the growth of cell and expression of the alkaline phosphatase (ALP) of osteoblast, like SaOS-2 cells. Upon these results, an approach has been introduced to incorporate polyP with the most common biominerals hydroxyapatite (HA) and calcium carbonate (CC) to enhance their biological actions. The microstructural characterization of the obtained calcium phosphate or carbonate phases show the ability to control nucleation and growth of these inorganic crystallites as a function of polyP content. After the physical-chemical and morphological characterization of the synthesized materials, they were assessed via studying their effects on cell activity and mineral deposition. The work presented here not only highlights the role of polyP as a morphogenetically active material (i.e. promoting maturation and functional activity of bone forming cells) but also provides strong evidence that amorphous phases of calcium phosphate or carbonate have a potential during biomineralization of bone tissue to act as precursors or nucleation sites for deposition of the bone mineral hydroxyapatite both in vitro and in vivo. Finally, the thesis opens new perspectives and paves a way for the development and fabrication of novel multifunctional hybrid biomaterials for effective bone tissue engineering and other biomedical purposes in the future.
DDC:	570 Biowissenschaften 570 Life sciences
Institution:	Johannes Gutenberg-Universität Mainz
Department:	FB 04 Medizin
Place:	Mainz
ROR:	https://ror.org/023b0x485
DOI:	http://doi.org/10.25358/openscience-4558
URN:	urn:nbn:de:hebis:77-diss-1000008008
Version:	Original work
Publication type:	Dissertation
License:	In Copyright
Information on rights of use:	https://rightsstatements.org/vocab/InC/1.0/
Extent:	X, 132 Blätter
Appears in collections:	JGU-Publikationen