A fast and reliable DSC-based method to determine the monomolecular loading capacity of drugs with good glass-forming ability in mesoporous silica

Publication date: 10 June 2018 Source:International Journal of Pharmaceutics, Volume 544, Issue 1 Author(s): Nele-Johanna Hempel, Katharina Brede, Niels Erik Olesen, Natalja Genina, Matthias Manne Knopp, Korbinian Löbmann The aim of this study was to introduce a fast and reliable differential scanning calorimetry (DSC)-based method to determine the monomolecular loading capacity of drugs with good glass-forming ability in mesoporous silica (MS). The proposed method is based on a solvent-free melting/fusion of drug into the MS during a heat-cool-heat cycle in the DSC. Overloaded drug-MS systems were analyzed in the DSC at different drug ratios (50, 60, 70, 80 and 90% w/w) to quantify the excess drug in the (the fraction not adsorbed to the MS surface). During the first heating, the drug will melt and fuse into the pores of the MS and upon subsequent quench cooling, the drug that is not adsorbed to the surface of the MS will amorphize into a separate phase (as drugs with good glass-forming ability do not crystallize upon quench-cooling from the melt). The drug molecules adsorbed to the MS surface are “immobilized” and will not contribute to a glass transition in the DSC and thus, the excess drug can be quantified simply by determining the change in the heat capacity over the glass transition (ΔC p). Since the ΔC p of overloaded samples decrease linearly with decreasing drug content, the monomolecular loading capacity of the drug in the MS can be determined by ext...
Source: International Journal of Pharmaceutics - Category: Drugs & Pharmacology Source Type: research