Design and characterization of spring water hydrogels with natural inorganic excipients

Abstract An essential first step to deep into the knowledge of the mechanisms of action that underlie the use of clay-based spring water gels is their design and development according to standardized protocols and procedures. Hydrogels with two spring waters and two clay excipients, sepiolite (PS9) and palygorskite (G30), were studied. The excipients were fully characterized as regards their identity, purity and richness, as well as their textural features, cation exchange capacities and zeta-potential. Conductivity, pH and ionic composition of spring waters were also assessed. Rheological and thermal properties of hydrogels were monitored through time. PS9 complied with identity, richness and purity descriptions of “Magnesium silicate” (or “Magnesium trisilicate”) United States and European Pharmacopoeia monographs', whereas G30 satisfied “Attapulgite” monograph. Cooling rates of 10% w/w spring water hydrogels were adequate for topical application as thermotherapic agents. Gel-like systems obtained with PS9 showed higher viscosities and yield values than G30 hydrogels, the type of spring water not exerting significant influence. The properties remained almost constant during a period of 2 months, ensuring quality standards. Longer periods resulted in unforeseeable changes in properties ascribed to water losses.