In vitro and in vivo dissolution of biocompatible S59 glass scaffolds.

Fabrication of porous tissue-engineering scaffolds from bioactive glasses (BAG) is complicated by the tendency of BAG compositions to crystallize in thermal treatments during scaffold manufacture. Here, experimental biocompatible glass S59 (SiO2 59.7 wt%, Na2O 25.5 wt%, CaO 11.0 wt%, P2O5 2.5 wt%, B2O3 1.3 wt%), known to be resistant to crystallization, was used in sintering of glass granules (300-500 µm) into porous scaffolds. The dissolution behavior of the scaffolds was then studied in vivo in rabbit femurs and under continuous flow conditions in vitro (14 days in vitro/56 days in vivo). The scaffolds were osteoconductive in vivo, as bone could grow into the scaffold structure. Still, the scaffolds could not induce sufficiently rapid bone ingrowth to replace the strength lost due to dissolution. The scaffolds lost their structure and strength as the scaffold necks dissolved. In vitro, S59 dissolved congruently throughout the 14-day experiments, resulting in only a slight reaction layer formation. Manufacturing BAG scaffolds from S59 that retain their amorphous structure was thus possible. The relatively rapid and stable dissolution of the scaffold implies that the glass S59 may have the potential to be used in composite implants providing initial strength and stable, predictable release of ions over longer exposure times.

Effect of bioactive glass air-abrasion on the wettability and osteoblast proliferation on sandblasted and acid-etched titanium surfaces.

The aim of this study was to evaluate the hydrophilicity, surface free energy, and proliferation and viability of human osteoblast-like MC3T3-E1 cells on sandblasted and acid-etched titanium surfaces after air-abrasion with 45S5 bioactive glass, zinc-containing bioactive glass, or inert glass. Sandblasted and acid-etched titanium discs were subjected to air-abrasion with 45S5 bioactive glass, experimental bioactive glass (Zn4), or inert glass. Water contact angles and surface free energy were evaluated. The surfaces were studied with preosteoblastic MC3T3-E1 cells. Air-abrasion with either type of glass significantly enhanced the hydrophilicity and surface free energy of the sandblasted and acid-etched titanium discs. The MC3T3-E1 cell number was higher for substrates air-abraded with Zn4 bioactive glass and similar to that observed on borosilicate coverslips (controls). Confocal laser scanning microscopy images showed that MC3T3-E1 cells did not spread as extensively on the sandblasted and acid-etched and bioactive glass-abraded surfaces as they did on control surfaces. However, for 45S5- and Zn4-treated samples, the cells spread most at the 24 h time point and changed their morphology to more spindle-like when cultured further. Air-abrasion with bioactive glass and inert glass was shown to have a significant effect on the wettability and surface free energy of the surfaces under investigation. Osteoblast cell proliferation on sandblasted and acid-etched titanium discs was enhanced by air-abrasion with 45S5 bioactive glass and experimental Zn4 bioactive glass compared with air-abrasion with inert glass or no air-abrasion.

Air Abrasion With Bioactive Glass Eradicates Streptococcus mutans Biofilm From a Sandblasted and Acid-Etched Titanium Surface.

Streptococcus mutans is able to form a high-affinity biofilm on material surfaces. S mutans has also been detected around infected implants. Bioactive glasses (BAGs) have been shown to possess antibacterial effects against S mutans and other microorganisms. This in vitro study was performed to investigate the influence of BAG air abrasion on S mutans biofilm on sandblasted and acid-etched titanium surfaces. Sandblasted and acid-etched commercially pure titanium discs were used as substrates for bacteria (n = 107). The discs were immersed in an S mutans solution and incubated for 21 hours to form an S mutans biofilm. Twenty colonized discs were subjected to air abrasion with Bioglass 45S5 (45S5 BAG), experimental zinc oxide containing BAG (Zn4 BAG), and inert glass. After the abrasion, the discs were incubated for 5 hours in an anaerobic chamber followed by an assessment of viable S mutans cells. Surface morphology was evaluation using scanning electron microscopy (n = 12). The thrombogenicity of the glass particle-abraded discs (n = 75) was evaluated spectrophotometrically using whole-blood clotting measurement at predetermined time points. Air abrasion with 45S5 and Zn4 BAG eradicated S mutans biofilm. Significantly fewer viable S mutans cells were found on discs abraded with the 45S5 or Zn4 BAGs compared with the inert glass (P < .001). No significant differences were found in thrombogenicity since blood clotting was achieved for all substrates at 40 minutes. Air abrasion with BAG particles is effective in the eradication of S mutans biofilm from sandblasted and acid-etched titanium surfaces. Zn4 and 45S5 BAGs had similar biofilm-eradicating effects, but Zn4 BAG could be more tissue friendly. In addition, the steady release of zinc ions from Zn4 may enhance bone regeneration around the titanium implant and may thus have the potential to be used in the treatment of peri-implantitis. The use of either BAGs did not enhance the speed of blood coagulation.

Dissolution of Amorphous S53P4 Glass Scaffolds in Dynamic In Vitro Conditions.

The silicate-based bioactive glass S53P4 is clinically used in bone regenerative applications in granule form. However, utilization of the glass in scaffold form has been limited by the high tendency of the glass to crystallize during sintering. Here, careful optimization of sintering parameters enabled the manufacture of porous amorphous S53P4 scaffolds with a strength high enough for surgical procedures in bone applications (5 MPa). Sintering was conducted in a laboratory furnace for times ranging from 25 to 300 min at 630 °C, i.e., narrowly below the commencement of the crystallization. The phase composition of the scaffolds was verified with XRD, and the ion release was tested in vitro and compared with granules in continuous flow of Tris buffer and simulated body fluid (SBF). The amorphous, porous S53P4 scaffolds present the possibility of using the glass composition in a wider range of applications.

Bone morphogenic protein expression and bone formation are induced by bioactive glass S53P4 scaffolds in vivo.

The two-stage induced-membrane (IM) technique is increasingly used for treatment of large bone defects. In stage one, the bone defect is filled with polymethylmethacrylate (PMMA), which induces a membrane around the implant. In stage two, PMMA is replaced with bone graft. Bioactive glasses (BAGs) are bone substitutes with bone-stimulating and angiogenic properties. We have previously shown that a certain type of BAG can also induce a foreign-body membrane similar to PMMA. The aim of this study was to evaluate the bone-forming capacity of sintered BAG-S53P4 and poly(lactide-co-glycolide) (PLGA)-coated BAG-S53P4 scaffolds for potential use as bone substitutes in a single-stage IM technique. Sintered porous rods of BAG-S53P4, BAG-S53P4-PLGA, or PMMA were implanted in rabbit femurs for 2, 4, or 8 weeks. The expression of bone morphogenic protein (BMP)-2, -4, and -7 in the IMs of implanted materials were analyzed with real-time quantitative polymerase chain reaction. Micro-computed tomography imaging was used to evaluate bone growth and further verified with scanning electron microscopy. BAG-S53P4 and BAG-S53P4-PGLA scaffold IMs show similar or superior expression of BMP-2, -4, and -7 compared with PMMA IM. Bone ingrowth into BAG scaffolds increased over time. Active bone formation occurred inside the BAG scaffolds and the respective BMP expressions were similar or superior for the BAG IMs compared with PMMA, thus making BAGs a promising device for single-stage treatment of bone defects. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res B Part B: Appl Biomater, 2018. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 847-857, 2019.