Papers by Author: Emilia Pecheva

Abstract: The aim of this study was to find if nanocrystal layers obtained by well-established nanotechnology are able to induce deposition of hydroxyapatite [Ca10(PO4)6(OH)2]. It is known that nanosized objects and porous structures influence biological events and they may be used to create biologically integrated multifunctional devices including biomaterials and sensors. In this work, sequential physical vapour deposition of CdSe and SiO, or SiOx film was used to modify glass substrates. To study the ability of the nanostructured surfaces to induce hydroxyapatite deposition, samples were immersed in a simulated body fluid and simultaneously irradiated with a scanning laser beam for a few minutes. This resulted in a porous sponge-like non homogeneous hydroxyapatite layer, consisting of networks of aggregates of nano dimensions on the modified surfaces. Analysis showed higher Ca and P contents in the stripes of the laser-substrate interaction, which indicated the influence of the laser energy. The method of laser-liquid-solid interaction used has led to a synergistic effect due to the simultaneous use of the nanostructured substrate, aqueous solution and laser energy.

Abstract: Opal is a natural nanostructure model. It possesses nanosized close packed silica spheres and a regular sublattice of voids, filled with molecular water and accessible for filling by other substances. Using natural opal as a substrate, no complimentary technique is needed to produce a patterned surface as it is present naturally. Thus, the possession of nano-dimensions for efficient influencing of different biological events can be used in the laboratory and biologically integrated multifunctional devices (biomaterials, sensors) could be created. Additionally, biomineralization mechanisms may be studied using model systems. The main purpose of the work is to use nanostructured or other functionalized materials as models to contribute to the study of biomineralization. Particularly this paper reports on the ability of natural opal from Bulgaria's Eastern Rhodopes mountain to induce the deposition of a surface layer of calcium phosphate from simulated body fluid. Raman, infrared spectroscopy and XRD were used to show that opal consists of two main phases: microcrystalline quartz and cristobalite and that the observed with optical microscopy layer deposited from the simulated body fluid on both phases was calcium phosphate.