Mesoporous Strontium-Doped Phosphate-Based Sol-Gel Glasses for Biomedical Applications

Mesoporous phosphate-based glasses have great potential as biomedical materials being able to simultaneously induce tissue regeneration and controlled release of therapeutic molecules. In the present study, a series of mesoporous phosphate-based glasses in the P₂O₅-CaO-Na₂O system, doped with 1, 3, and 5 mol% of Sr²⁺, were prepared using the sol-gel method combined with supramolecular templating. A sample without strontium addition was prepared for comparison. The non-ionic triblock copolymer EO₂₀PO₇₀EO₂₀ (P123) was used as a templating agent. Scanning electron microscopy (SEM) images revealed that all synthesized glasses have an extended porous structure. This was confirmed by N₂ adsorption-desorption analysis at 77 K that shows a porosity typical of mesoporous materials. ³¹P magic angle spinning nuclear magnetic resonance (³¹P MAS-NMR) and Fourier transform infrared (FTIR) spectroscopies have shown that the glasses are mainly formed by Q¹ and Q² phosphate groups. Degradation of the glasses in deionized water assessed over a 7-day period shows that phosphate, Ca²⁺, Na⁺, and Sr²⁺ ions can be released in a controlled manner over time. In particular, a direct correlation between strontium content and degradation rate was observed. This study shows that Sr-doped mesoporous phosphate-based glasses have great potential in bone tissue regeneration as materials for controlled delivery of therapeutic ions.