On the importance of physicochemical parameters of copper and aminosilane functionalized mesoporous silica for hydroxychloroquine release

Recently, great attention has been paid to hydroxychloroquine which after promising in vitro studies has been proposed to treat the severe acute respiratory syndrome caused by SARS-CoV-2. The clinical trials have shown that hydroxychloroquine was not as effective as was expected and additionally, several side effects were observed in patients cured with this medicament. In order to reduce them, it is suggested to deliver hydroxychloroquine in a controlled manner. Therefore, in this study non-modified (SBA-15, SBA-16) and modified with copper and aminosilane mesoporous silica materials were applied as novel nanocarriers for hydroxychloroquine. First, pristine and functionalized samples were synthesized and characterized by X-ray diffraction, low-temperature nitrogen sorption, transmission electron microscopy, X-ray photoelectron spectroscopy, infrared spectroscopy, laser diffraction. Then the influence of physicochemical parameters of materials obtained on the adsorption and release processes of hydroxychloroquine was analyzed. The mechanism of hydroxychloroquine binding to non-modified silicas was based on the formation of hydrogen bonds, while in the case of copper and aminosilane functionalized materials the complexes with drug molecules were generated. The release behavior of hydroxychloroquine from silica samples obtained was determined by different factors including pH conditions, textural parameters, surface charge, and presence of surface functional groups. The greatest differences in hydroxychloroquine release profiles between materials were observed at pH 7.2. The amount of drug desorbed from silica decreased in the following order: functionalized SBA-15 (84%) > functionalized SBA-16 (79%) > SBA-15 (59%) > SBA-16 (33%). It proved that a higher amount of drug was released from materials of hexagonal structure.