Synthesis and characterization of porous silicon as hydroxyapatite host matrix of biomedical applications

Abstract

In this work, porous-silicon samples were prepared by electrochemical etching on p-type (B-doped) Silicon (Si) wafers. Hydrofluoric acid (HF)-ethanol (C2H5OH) [HF:Et] and Hydrofluoric acid (HF)-dimethylformamide (DMF-C3H7NO) [HF:DMF] solution concentrations were varied between [1:2]—[1:3] and [1:7]—[1:9], respectively. Effects of synthesis parameters, like current density, solution concentrations, reaction time, on morphological properties were studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements. Pore sizes varying from 20 nm to micrometers were obtained for long reaction times and [HF:Et] [1:2] concentrations; while pore sizes in the same order were observed for [HF:DMF] [1:7], but for shorter reaction time. Greater surface uniformity and pore distribution was obtained for a current density of around 8 mA/cm2 using solutions with DMF. A correlation between reflectance measurements and pore size is presented. The porous-silicon samples were used as substrate for hydroxyapatite growth by sol-gel method. X-ray diffraction (XRD) and SEM were used to characterize the layers grown. It was found that the layer topography obtained on PS samples was characterized by the evidence of Hydroxyapatite in the inter-pore regions and over the surface.

Physico-Chemical Properties and In Vitro Antifungal Evaluation of Samarium Doped Hydroxyapatite Coatings

“…These results are in good agreement with previously reported studies regarding the lack of antimicrobial properties of hydroxyapatite [20,59,60]. Moreover, previous studies [15,[56][57][58][59][60][61][62][63][64] reported that the antifungal effect of samarium could be explained by the fact that samarium ions have the ability to attach to the cell membrane leading to changes of its permeability. Furthermore, samarium ions that are released from the composite matrix could disrupt the bacterial membrane integrity thus affecting a multitude of cellular processes such like adhesion, ion conductivity and cell signaling [61].…”

“…Thus, the development of 5SmHAp coatings with enhanced osteoblastic cell response given by the hydroxyapatite matrix and possessing antibacterial activity due to the presence of samarium ions could lead to a better outcome of bone graft implantation. The choice of Si as a substrate started from the intention to extend the applicability of these biocompatible materials with antimicrobial properties from dental field to devices that could be used in tissue engineering [62] or human prosthetic [63] in order to prevent postoperative infections. Ruffino and Torrisi [64] in their studies regarding the influence of interaction between film and substrate on the nanoscale film morphology showed that between Ag films deposited on SiO 2 /Si and TiO 2 /Ti substrates exist various differences.…”