The oxidized ordered mesoporous carbons of cubic and hexagonal structure obtained by two templating methods (soft and hard) were applied for the first time as delivery systems for paracetamol-the most common antipyretic and analgesic drug in the world. The process of carbon oxidation was performed using an acidic ammonium persulfate solution at 60 °C for 6 h. The functionalization was found to reduce the specific surface area and pore volume of carbon materials, but it also led to an increasing number of acidic oxygen-containing functional groups. The most important element and the novelty of the presented study was the evaluation of adsorption and release ability of carbon carriers towards paracetamol. It was revealed that the sorption capacity and the drug release rate were mainly affected by the materials' textural parameters and the total amount of surface functional groups, notably different in pristine and oxidized samples. The adsorption of paracetamol on the surface of ordered mesoporous carbons occurred according to different mechanisms: donor-acceptor complexes and hydrogen bond formation. The adsorption kinetics was assessed using pseudo-first- and pseudo-second-order models. The regression results indicated that the adsorption kinetics was more accurately represented by the pseudo-second-order model. Paracetamol was adsorbed onto the carbon materials studied following the Langmuir type isotherm. The presence of oxygen-containing functional groups on the surface of ordered mesoporous carbons enhanced the amount of paracetamol adsorbed and its release rate. The optimal drug loading capacity and expected release pattern exhibited oxidized ordered mesoporous carbon with a hexagonal structure obtained by the hard template method.
Keywords: active pharmaceutical ingredients; adsorption of paracetamol; carbon carriers; kinetic modelling; permeability study.