In Situ Encapsulation of Hydrogen Peroxide in a Silica Matrix in the Presence of Divalent Metal Ions (Mg²⁺ and Ca²⁺)

Abstract

Encapsulating hydrogen peroxide (H2O2) in silica hydrogels is a simple, environmentally friendly, and cost-effective method that is easy to scale up. Sodium silicate is the most commonly used aqueous silicate in sol–gel chemistry. Previously, we studied the effects of Na+ and K+ ions in the starting silicate precursor on the structure of hydrogels and the stability of entrapped H2O2. In the present study, we present the results obtained when divalent ions, Mg2+ and Ca2+, were introduced in the sol. The use of divalent metal ions resulted in hydrogel structures that are different from those previously obtained. H2O2 stability increased with the addition of Mg2+ and Ca2+ ions and with decreasing pH. At low pH values, 93% of the peroxide was retained at the end of 10 days with Mg2+-containing hydrogels, compared to 91% retention with Ca2+-containing hydrogels, 87% retention with K+-containing hydrogels, and 68% retention with a unmodified sodium silicate precursor. The results show that the structure of the hydrogels can be changed using different types and amounts of metal ions to tailor the release of H2O2 for an intended application.

Oxygen-Releasing Composites: A Promising Approach in the Management of Diabetic Foot Ulcers

“…Silica gel, polyvinylpyrrolidone (PVP), and small molecules (e.g., urea, sodium carbonate, and sodium borate) entrapped H 2 O 2 molecules within the composite [ 79 , 80 ]. In such silica-based encapsulation, divalent metal ions, Mg 2+ and Ca 2+ , also contributed to the release of H 2 O 2 from silica hydrogels [ 81 ]. Such engineerable characteristics of materials that modulate the extended H 2 O 2 delivery indicate that liquid H 2 O 2 molecules hold great potential for the realization of topical oxygen delivery in diabetic wounds repair.…”