Composition-structure-properties relationship of strontium borate glasses for medical applications

Abstract

We have synthesized TiO2 doped strontium borate glasses, 70B2O3-(30-x)SrO-xTiO2 and 70B2 O3 -20SrO(10-x)Na2 O-xTiO2 . The composition dependence of glass structure, density, thermal properties, durability, and cytotoxicity of degradation products was studied. Digesting the glass in mineral acid and detecting the concentrations of various ions using an ICP provided the actual compositions that were 5-8% deviated from the theoretical values. The structure was investigated by means of (11)B magic angle spinning (MAS) NMR spectroscopy. DSC analyses provided the thermal properties and the degradation rates were measured by measuring the weight loss of glass disc-samples in phosphate buffered saline at 37°C in vitro. Finally, the MTT assay was used to analyze the cytotoxicity of the degradation products. The structural analysis revealed that replacing TiO2 for SrO or Na2 O increased the BO3/BO4 ratio suggesting the network-forming role of TiO2 . Thermal properties, density, and degradation rates also followed the structural changes. Varying SrO content predominantly controlled the degradation rates, which in turn controlled the ion release kinetics. A reasonable control (2-25% mass loss in 21 days) over mass loss was achieved in current study. Even though, very high concentrations (up to 5500 ppm B, and 1200 ppm Sr) of ions were released from the ternary glass compositions that saturated the degradation media in 7 days, the degradation products from ternary glass system was found noncytotoxic. However, quaternary glasses demonstrated negative affect on cell viability due to very high (7000 ppm) Na ion concentration. All the glasses investigated in current study are deemed fast degrading with further control over degradation rates, release kinetics desirable.

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

“…The very similar field strength of Ca 2+ and Sr 2+ ions resulted in no significant shielding/de-shielding of the 29 Si nuclei (Fredholm et al, 2010). Anyway, the larger size of the Sr 2+ ion compared to that of Ca 2+ was found to expand and weaken the network, thus leading to a modification of the thermal properties of the glass (Lotfibakhshaiesh et al, 2010; Goel et al, 2011; Hasan et al, 2015; Li et al, 2015; Bellucci et al, 2017).…”

“…MgO, SrO and BaO are conventional modifiers that enter the glass network by disrupting B–O–B, P–O–P and B–O–P bonds. In particular, the addition of modifying oxides in borate glasses can augment the network via the following events: (i) breaking of B–O–B bonds with the contiguous creation of non-bridging oxygens; (ii) increasing the oxygen coordination of boron; and (iii) combining both mechanisms mentioned above (Hasan et al, 2015).…”

“…The ion movements within the network are, in fact, partially inhibited by the expansion of the network caused by the larger size of Sr 2+ ion (Pan et al, 2009). Moreover, while Na and B are easily released into the external environment, SrO uses to form Sr (OH) 2 species, which are chemically more resistant and difficult to dissolve (Hasan et al, 2015).…”

Cationic Substitutions in Hydroxyapatite: Current Status of the Derived Biofunctional Effects and Their In Vitro Interrogation Methods

“…Half-maximal cytotoxic concentration (in mM) of various cationic species: Li [428,429,430], Na [431,432,433,434], Mg [435,436,437,438], Sr [439,440,441], Al [442,443,444], Ga [408,445], Sn [406,446,447], Te [448,449,450], Pb [427,451], Bi [452,453,454,455], Ti [406,408,443,444,456,457], V [408,442,443,444], Cr [408,442,443,444], Mn [443,458,459,460], Fe [426,442,443,461], Co [406,408,442,443,444,462,463], Ni [406,408,430,443,…”

The anomaly in bioactive sol–gel borate glasses

“…25 SGBGs have also been incorporated into polymer matrices to enhance composite bioactivity, 26 while compositions doped with silver, have demonstrated antibacterial properties. 27 Interest in bioactive borate glasses has led to many 'unique' compositions [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43] such as ''1605''. [44][45][46] However, despite fundamental differences between borate and silicate glass structure, many borate compositions, including our previous work, [23][24][25][26]47 have been based on ''traditional'' silicate glass compositions like Bioglass s ''45S5'', 15,[23][24][25][26][47][48][49][50] ''13-93'', 14,16,17,[51][52][53][54][55][56][57]…”