Release properties of melatonin loaded mesoporous silica materials

Melatonin is a hormone produced by the pineal gland and involved in the regulation of circadian rhythms (e.g. sleep/wake cycle). Exogenous melatonin is used in the treatment of circadian disorders (e.g. delayed sleep phase syndrome, jet-lag or shift-work). In currently available commercial formulations melatonin has low bioavailability. Tailored formulations are needed to treat diverse and specific circadian disorders. Mesoporous silica materials can be efficient drug carriers as they are non-toxic biodegradable materials possessing high surface area, large pore volume and pore dimensions in the mesoscale range. This study focused on the preparation of mesoporous silica formulations for controlling the release of melatonin. Mesoporous materials (MCM-41) were synthesised and characterized through different physicochemical techniques. They were loaded with melatonin and their release properties were investigated in simulated gastro and intestinal fluids under sink conditions. Results suggested that MCM-41 alone did not delay the release of melatonin significantly. Thus, the particles were coated with polyacrylic acid (PAA) to further slow the rate of release. Preliminary biological assays revealed that both uncoated and PAA-coated MCM-41 with melatonin did not significantly increase apoptosis nor ROS production compared to the control (no treatment) when added for 24 h to mouse microglial cells (BV2).