Insights into Adsorptive Drug Loading on Silica Aerogels from Supercritical CO₂

Abstract

This work gives an insight into the process of adsorptive drug loading in silica aerogels from supercritical CO2 (scCO2). A prevalent method for such loading entails bringing the aerogels into contact with the drug–scCO2 solution followed by slow or isothermal depressurization. Our previous work established that drug precipitates during depressurization. Consequently, the adsorptive drug loading measured by the prevalent method includes precipitation. An alternative method is presented for accurate measurement of adsorption avoiding precipitation. To illustrate the disparity between the two methods, the concentration dependence of drug loadings in scCO2, obtained by both methods, is compared for fenofibrate, ibuprofen, and benzoic acid. A mechanism is proposed, and a mathematical model is developed for comparing the adsorptive drug loadings by both methods. The loading obtained by the present method is found to be much less than that by the prevalent method, though both correlate well with the formalism of the Langmuir adsorption equation with the same equilibrium constant at low concentrations. Equations are developed for the concentration dependence of drug loadings measured by both methods at all concentrations in scCO2.

Exploring the Conformational Equilibrium of Mefenamic Acid Released from Silica Aerogels via NMR Analysis

“…Two critical aspects of drug development are determining the ideal dosage and creating effective formulations for controlled release [ 1 , 2 ]. Recently, several researchers have proposed various methods based on supercritical fluid technology, such as micronization [ 3 ]; the creation of multicomponent crystals [ 4 , 5 ]; microencapsulation [ 6 ]; impregnation [ 7 ]; adsorbing drugs onto porous carriers [ 8 ]; and co-precipitation [ 9 ] to address the issue of low dissolution rate. The dissolution rate of drugs is increased by adsorption in an amorphous state [ 3 ].…”

“…Researchers have noted that the efficiency of such drugs remains unchanged during storage [ 4 , 5 , 6 , 7 ]. Singh N. et al have shown that due to high surface area, silica aerogels (AG) are an effective carrier material for poorly water-soluble drugs [ 8 ]. The results show [ 9 ] that tetraethyl orthosilicate (TEOS) [ 10 ]-doped aerogel had significantly better morphology, structure, and characteristics than the non-TEOS aerogel.…”

“…Recent studies by Singh N. and Tkalec G. [ 8 , 18 ] have indicated that silica aerogels could be viable for drug delivery systems [ 19 , 20 ]. Researchers investigated the silica aerogels impregnated with the number of active pharmaceutical ingredients (API) by conducting adsorption experiments.…”