Antibacterial and osteo-stimulatory effects of a borate-based glass series doped with strontium ions

Abstract

This work considered the effect of both increasing additions of Strontium (Sr) and incubation time on solubility and both antibacterial and osteo-stimulatory effects of a series of glasses based on the BO-PO-CaCO-NaCO-TiO-SrCO series. The amorphous nature of all the glasses was confirmed by X-ray diffraction. Discs of each glass were immersed in de-ionized water for 1, 7 and 30 days, and the water extracts were used for ion release profiles, pH measurements and cytotoxicity testing. Atomic absorption spectroscopy was employed to detect the release of Na, Ca and Sr ions from the glasses with respect to maturation, which indicated that the addition of Sr retarded solubility of the glass series. This effect was also confirmed by weight loss analysis through comparing the initial weight of glass discs before and after periods of incubation. The incorporation of Sr in the glasses did not influence the pH of the water extracts when the glasses were stored for up to 30 days. Cytotoxicity testing with an osteoblastic cell line (MC3T3-E1) indicated that glasses with the higher (20 mol% and 25 mol%) Sr incorporation promoted proliferation of osteoblast cells, while the glasses with lower Sr contents inhibited cell growth. The glass series, except for Ly-B5 (which contained the highest Sr incorporation; 25 mol%), were bacteriostatic against S. aureus in the short term (1-7 days) as a result of the dissolution products released.

Antimicrobial Potential of Strontium Hydroxide on Bacteria Associated with Peri-Implantitis

“…Furthermore, in the higher concentrations, where the liquid/Sr ratio was smaller than in the lower concentrations, the liquid may have evaporated during the incubation before the Sr was able to diffuse properly into the agar mass. A similar observation has been reported by Li Y et al [31], where the highest concentration used in their study did not show any zone of inhibition, compared to lower concentrations (25 mol% SrCO 3 vs. 5 and 10 mol% SrCO 3, respectively) that showed the highest zones of inhibition against S. aureus in an Agar disk-diffusion test.…”

Multiple and Promising Applications of Strontium (Sr)-Containing Bioactive Glasses in Bone Tissue Engineering

“…Another proposed mechanism for the antibacterial effect of Sr is related to its intervention to bacterial metabolism at concentrations above 180 mM since Sr 2+ ions can act as a competitor to iron for specific binding sites in iron-sensing proteins (Brown et al, 2006). In contrast to the studies mentioned above, other scientists showed that the release of increased levels of Sr 2+ has no positive effect on the bacteria inhibition (Dabsie et al, 2009; Li et al, 2016). On this matter, Dabsie et al showed that Sr 2+ ions have no significant antibacterial effect at the concentrations of 0.19, 0.37, 0.74, and 1.11 mol/L.…”

“…Moreover, some researchers have proposed the immunomodulatory effects of Sr element, which provides an appropriate environment for enhancing bone regeneration (Zhang et al, 2016). It was reported that Sr 2+ ions might have antibacterial property when released from different product formulations (Li et al, 2016; Liu et al, 2016). Having the above-mentioned characteristics, Sr is being currently used in various types of glasses (melt-derived and sol-gel) for bone tissue engineering applications.…”

Investigating the Fracture Resistance of Bioactive Glass Coatings on Metallic Implants

“…A previous study 120 revealed that the weight loss of powder discs (2.2 × ϕ6.4 mm,) of Ly-B0, Ly-B3 and Ly-B5 after 24-hours incubation were ~35.5%, ~5.75% and ~3.42% respectively, which were significantly lower than those of the glass coatings after 24-hours incubation (Figure 6.4). Since weight loss of the glasses resulted from their degradation in de-ionized water 98 glass coatings degrade more intensely in the first 24 hours than the glasses discs.…”

“…Nevertheless, the high dissolution rate may induce cell damage [117][118][119] and loss of the coating-substrate bond strength, subsequently retarding implant fixation 36 . In order to address the problem, in Chapters 5 and 6 of the present dissertation, Strontium ions (Sr 2+ ) were incorporated into the borate-based glasses to modify the dissolution rate 120 , increase the proliferation of osteoblast cells in vivo 121 and stimulate bone formation in vitro 122 . Also, since no previous study has investigated the mechanical performance of bioactive coatings, Chapter 6 of the present dissertation has focused on measuring the fracture toughness of bioactive glass coatings after degradation.…”