Investigation of bacterial interaction on calcium phosphates

Abstract

Calcium phosphates (CaP) are biomaterials widely used in applications for bone regeneration. The success of these materials is due to the similarity in composition of CaP to the mineral phase of bone. An important aspect is the risk of infection during surgery caused by bacterial adhesion onto the implant’s surface. In spite of the use of antibiotics is the most common solution used to combat infections, antimicrobial resistance makes it difficult to eradicate them being necessary the adoption of new strategies. Over the last few years, it has been observed how the topography of materials can minimise bacterial adhesion and even kill them. The aim of this project is to investigate bacterial interaction (Staphylococcus aureus and Escherichia coli) on CaP with different topographies. The project is divided in two parts. The first one is based on the preparation of three CaP materials with different topographies: a material obtained at high temperature with a relatively smooth topography of polyhedral crystals (β-TCP) and two materials obtained at body temperature, one with plate-like crystals topography (C-HA) and the other with nanometric needle-like crystals topography (F-HA). From these materials, compacted samples are prepared with the aim of reducing the effect of topography. The second part is based on the investigation of bacterial adhesion and proliferation (Staphylococcus aureus and Escherichia coli) on these materials. Materials have been characterised by X-Ray diffraction and by scanning electron microscopy. The samples with bacteria have been observed by confocal microscopy in order to analyse the surface coverage and by scanning electron microscopy to visualise bacteria and the topography in detail. Results indicate that bacteria are sensitive to surface topography, adhering and proliferating better on smooth surfaces such as β-TCP, whereas on more complex surfaces such as those of C-HA and FHA, especially in the latter material, there is a significant reduction in bacterial adhesion.