Melatonin-Loaded Nanoparticles for Enhanced Antidepressant Effects and HPA Hormone Modulation

Background. The present work aims at formulating the melatonin-loaded nanoparticles (MTNPs) exhibiting the controlled-release and pH-sensitivity to repurpose the use of melatonin in the treatment of depressive-like behaviors and hypothalamus-pituitary-adrenal (HPA) axis dysregulation. Methods. MTNPs were characterized for the size, drug incorporation, and in vitro release in the different pH environments. Its merits were in vivo tested on the pinealectomized rats presenting the depressive-like behaviors and the abnormal HPA axis activity by calculating the improvement on saccharin preference, swimming immobility time, and the negative feedback of HPA axis. Results. Results revealed that MTNPs showed nanometer size, 15.77% of drug loading, 33.82% of encapsulation efficiency, the different controlled-release profiles in different pH environments (pH 1.2, pH 6.8, and pH 7.4), more sensitivity release in simulated intestinal fluid (pH 7.4) and blood (pH 6.8), and less sensitivity release in simulated gastric fluid (pH 1.2). Furthermore, MTNPs displayed better antidepressant actions in reducing the immobility time of forced swimming test, increasing the preference for saccharin, and sensitizing the blunt negative feedback of HPA axis, when compared to the free melatonin. Conclusions. The controlled-release nanoparticles is shown to be an effective improvement on the dosage form for melatonin, which is worthy of futuristic and complete evaluation.