Dissolution Kinetics of a Bioactive Glass by Continuous Measurement

Abstract

Understanding the detailed dissolution behavior is of importance when novel glasses are designed for different clinical applications. The goal of this work was to develop a sensitive on-line analysis method to study the dissolution of bioactive glasses. An inductively coupled plasma optical emission spectrometer together with a flow-through microvolume pH electrode were utilized to continuously measure the concentration profile of the ions dissolving from glass particles into aqueous solutions. The method was tested with the bioactive glass 1-98 consisting of seven oxides: 6Na 2 O, 11K 2 O, 5MgO, 22CaO, 1B 2 O 3 , 2P 2 O 5 , and 53SiO 2 (wt%). The influence of flow rate and temperature on the dissolution profile and kinetics of 1-98 was studied in ultrapure water. In addition, the influence of the solution composition was studied using ultrapure water and with tris(hydroxymethyl)aminomethane (TRIS) buffer. The strength of the method is that the initial dissolution can be accurately determined simultaneously both qualitatively and quantitatively. When using the highest flow rates, the dissolution rate changed from a diffusion-controlled toward a surfacecontrolled mechanism. As a result of the temperature increase, the overall dissolution increased according to Arrhenian behavior and led more rapidly to steady-state dissolution. The change of solution from unbuffered (ultrapure water) to TRIS changed the dissolution mechanism from uniform to preferential. In addition, higher concentrations of all ions were measured in TRIS than in pure water. The method develop is promising for fast screening of the dissolution mechanism of glasses in different experimental conditions. II. Experimental ProcedureThe effect of surface area, flow rate, temperature, and solution composition on the dissolution behavior of bioactive glass 1-98 was measured using a flow-through cell connected to an inductively coupled plasma optical emission spectrometer, ICP-OES (Optima 5300 DV; Perkin Elmer, Waltham, MA). The ion concentrations of the solution were measured on-line every 12 s (one replicate per measurement). The pH values were C. Jantzen-contributing editor Manuscript No. 31143.

Increase in VEGF secretion from human fibroblast cells by bioactive glass S53P4 to stimulate angiogenesis in bone

“…The dissolution profile of both BAGs, S53P4 and 45S5, in aqueous media such as simulated body fluid (SBF), has been extensively investigated. Using a sensitive continuous on‐line analysis method, combining a plasma optical emission spectrometer with a flow‐through micro‐volume pH electrode, the qualitative and quantitative ion release kinetic can be measured in situ and immediately from the moment the glass is placed in the solution . A continuous release of Ca, Na, P, and Si from both glasses has been demonstrated to occur immediately when they are placed in aqueous solution and the ion release profile of BAGs has also an effect on angiogenesis as discussed in the literature …”

Bioactive Glasses—Structure and Properties

“…[66] According to the original mechanism of bioactivity published by Hench, [72] the initial ion exchange and pH rise is followed by alkaline hydrolysis of Si-O-Si bonds and subsequent condensation reactions between Si-OH groups, which leads to repolymerization of asilica gel layer. [73] This,h owever,d oes not take account of the possibility that the pH value may be well above that locally,for example,directly at the glass/solution interface.Silicon-containing species have been detected in solution after immersion of bioactive glasses in both static ( Figure 11) and dynamic dissolution experiments, [61,63,74] thus showing that dissolution of parts of the silicate network does occur to some extent. Ty pical in vitro immersion or cell culture studies using buffered media tend to use glass/solution ratios which keep the pH value well below 9, as the aim is to mimic in vivo conditions with their constant fluid exchange.…”

Dissolution, bioactivity behavior, and cytotoxicity of rare earth‐containing bioactive glasses (RE = Gd, Yb)

“…All these steps are well reported in the literature, 25,39 and they are used as a general dissolution theory of glasses. In the first stage (K 1 ), such process is dominated by the exchange of alkali ions with protons in solution in which the dissolution rate varies with the square root of time.…”

“…25,26 In order to perform the test, 75 mg of each glass was immersed into 1.5 mL of Tris-buffer solution, and placed in an orbital shaker for periods of 1, 6, 12, 24, 72, 120, and 168 hours. In brief, a trisbuffer solution prepared with 13.25 g of (Hydroxymethyl) aminomethane (Tris) per liter of ultrapure water, and pH adjusted for 7.4 with 1 mol/L HCl at 37°C, was used as dissolution medium.…”

“…In brief, a trisbuffer solution prepared with 13.25 g of (Hydroxymethyl) aminomethane (Tris) per liter of ultrapure water, and pH adjusted for 7.4 with 1 mol/L HCl at 37°C, was used as dissolution medium. 25,26 In order to perform the test, 75 mg of each glass was immersed into 1.5 mL of Tris-buffer solution, and placed in an orbital shaker for periods of 1, 6, 12, 24, 72, 120, and 168 hours. The concentration of ions released from glass was measured by inductively coupled plasma optical emission spectrometry model with axial vision series 710 (Varian), using the emission lines: Si (λ = 250.690 nm), Na (λ = 588.995 nm), P (λ = 213.618 nm), Ca (λ = 422.673 nm), Gd (λ = 342.246 nm), and Yb (λ = 328.937 nm).…”