Dissolution of bioactive glasses in acidic solutions with the focus on lactic acid

This work reports the dissolution of bioactive glasses in acidic solutions. The focus was on lactic acid, thus mimicking the conditions that may develop locally during in vivo degradation of polylactic acid/bioactive glass composites. First, the dis-solution of glasses 45S5, S53P4, and S68 was studied in 1.2 M lactic acid. The leaching of ions from 45S5 in lactic acid solution was further compared with the reactions in hydrochloric acid solution. Finally, Tris-buffered solutions in which the pH was adjusted to 7.4 using hydrochloric or lactic acid were used to study the effect of the acidic components on the dissolution of 45S5. The dissolution extent followed the initial acid concentrations: greater in lactic acid and lower in hydrochloric acid of the same initial pH. Rapid, preferential dissolution of Na, Ca, and P took place in lactic acid solution, thus suggesting that locally high concentrations of degradation products of lactic acid may enhance the dissolution of bioactive glass in Polylactic acid composites. When solution pH exceeded 4, calcium phosphate started to form on the glass surface.