Evaluating the effect of pharmaceuticals encapsulated in silica by the sol–gel method on algal growth inhibition

Gentamicin was comparatively encapsulated within silica matrices by sol–gel processes that use a base-catalyzed gelation, base-catalyzed precipitation, or acid-catalyzed gelation route. Acid-catalyzed gelation was chosen to encapsulate several pharmaceuticals (fluoxetine, lidocaine, morphine, nifedipine, paracetamol, and tetracycline). The xerogels were characterized by their carbon content and nitrogen adsorption values. The encapsulated systems had high surface areas ranging from 280 to 650 m² g⁻¹. Their inhibition of Desmodesmus subspicatus growth was evaluated. The systems with bulkier pharmaceuticals and greater surface areas showed the highest drug-related algal growth inhibition. The encapsulated systems were less toxic to Desmodesmus subspicatus than the free drugs. Silica-encapsulated paracetamol was the xerogel that inhibited algal growth the least, while the encapsulated nifedipine was the most toxic to the algae. Compared with the free drugs, the encapsulated systems were 17–55% less toxic to algae based on the Desmodesmus subspicatus growth inhibition data.