Biomimetic designing of scaffolds based on hydroxyapatite for encapsulation of antibiotics with controlled release

The subject of this PhD thesis is derived from current problems of bone tissue engineering, related to processes of osteointegration, implantation and resolution of the problems arising from the implantation site inflammation. The first part of the thesis examines problems of biocompatibility and osteointegration of materials used as implants in bone tissue engineering. Thus, the formation of bioactive coatings of calcium hydroxyapatite (CHA) on two potential types of implants, metal and ceramic, using biomimetic method, was investigated. This method is appropriate because it enables formation of CHA with similar structural and morphological properties of a natural bone. It is based on the use of the solution of similar ionic composition as human plasma (they are known as simulated body fluids- SBF) and the conditions of CHA nucleation are similar to the conditions found in biological systems. The metal surface (stainless steel) was previously activated by spraying with the thin silica film, with OH groups that act as active centers of heterogeneous nucleation of apatite. Ceramic substrate- porous CHA scaffold was treated in biomimetic medium in order to improve nanotopology of scaffold inner walls, optimal for growth and activation of bone tissue cells. Three different polymers (PLGA, cellulose and alginate) were used for the functionalization of the scaffold walls in order to achieve its additional nanodesigning and increase of its surface activity. SBF, as well as the SBF combined with fetal calf serum and Eagle’s minimal essential medium, were used as bioactive liquid medium, where biomimetic nucleation of apatite occurs. The analysis of the phases formed in the biomimetic medium, using X ray diffraction method, confirmed that CHA was formed on the surface of all samples. Infrared spectroscopy showed that this is CHA of slightly shifted stoichiometry. Atomic force microscopy pointed the mechanism of nucleation, while scanning electron microscopy showed the morphology of nucleated phases. Mass measurements, with volume corrections made using the BET method, showed that the thickness of nucleated CHA film depends on the aging time of samples in SBF and the type of selected III IV biomimetic medium. Also, bio-acceptability of these materials was investigated in vitro and in vivo and very good results were obtained. The second part of the thesis focuses on resolving the problem of frequent inflammation that occurs during implantation, as well as the proble