Novel silicon‐doped hydroxyapatite (Si‐HA) for biomedical coatings: An in vitro study using acellular simulated body fluid

Abstract

Magnetron co-sputtering was used to produce silicon-doped hydroxyapatite (Si-HA) as coatings intended for potential applications such as orthopedic and dental implants. It was found that the crystallinity of the as-sputtered coatings increased after annealing, resulting in a nanocrystalline apatite structure. Subsequently, the bioactivity of the coatings was evaluated in an acellular simulated body fluid (SBF). Physicochemical evaluation demonstrated that a carbonate-containing apatite layer, which is essential for bonding at the bone/implant interface, was formed on the coating surfaces after immersion in SBF between 4 and 7 days. The annealed coatings exhibited enhanced bioactivity and chemical stability under physiological conditions, as compared with the as-sputtered coatings. It is proposed that the rate at which the carbonate-containing apatite layer forms is dependent on the scale factor of the structure. A nanocrystalline structure can provide a higher number of nucleation sites for the formation of apatite crystallites, leading to a more rapid precipitation of carbonate-containing apatite layer. This work shows that Si-HA coatings offer considerable potential for applications in hard tissue replacement, owing to their ability to form a carbonate-containing apatite layer rapidly.

Bioceramics: Past, present and for the future

“…59,60 In vitro studies have shown that these coatings exhibit enhanced bioactivity and biomineralisation over uncoated samples and pure HA coatings. [61][62][63] Fig. 3 shows a typical example of osteoblast response to a magnetron co-sputtered Si-HA thin film.…”

Bioceramic Coatings for Metallic Implants

“…Silicate-substituted HA, Ca 10 (PO 4 ) 6Àx (SiO 4 ) x (OH) 2Àx , has received a great deal of interest recently as a potential bone substitute material [9,89]. The silicatecontaining HA-based (Si-HA) coatings have shown an improvement in biological performance over their undoped counterparts [90,91]. Cells were either kept in proliferation medium (a, c) or in osteogenic medium (b, d) [87] As a measure to achieve the dual aims of bacterial inhibition and enhancement of osteoblast functions of implant materials, silver-containing HA (Ag-HA) composite coatings are of special interest.…”

“…Silver or silicate could be incorporated into HA prior to the deposition process, or Ag (or Si) and HA could be utilized as two separate coating targets. Based on the success of Si-substituted apatite bone grafts, the coatings prepared via RF magnetron co-sputtering of HA and Si targets were investigated by Thian et al [90,91,98].…”

“…The annealed silicate-containing HA-based coatings have shown an improvement in biological performance over their undoped counterparts [90,91].…”

Biomimetic Hydroxyapatite Deposition on Titanium Oxide Surfaces for Biomedical Application

“…Otherwise, rough and porous surfaces could stimulate cell attachment and formation of extra-cellular matrix [73]. The biological benefits/effects of biomimetic HA [63,[74][75][76] and the possibilities to use them as coatings on titanium implants for improving the biological responses have been reported. However, only a few of the developed ion-substituted and/or ion doped hydroxyapatite coatings have been tested in vitro and/or in vivo, and the improvement of the biological response due to ion substitution is thus still just a hypothesis [20,27,[77][78][79].…”