Levothyroxine combined with selenium nanoparticles in one liposomal delivery system for hypothyroidism

Levothyroxine, as a thyroid-stimulating hormone, is the primary drug used for hypothyroidism treatment, but it has poor bioavailability. Selenium (Se) plays an important role in regulating thyroid function; moreover, selenium nanoparticles (SeNPs) offer advantages over other Se forms. Liposomal delivery systems, especially those coated with polyethylene glycol (PEG), can increase the oral bioavailability of drugs and provide controlled release. In our research, as described in this paper, we aimed to develop an orally applicable liposomal delivery system to achieve enhanced treatment of hypothyroidism with SeNP characteristics, controlled levothyroxine release, and improved bioavailability of both drug and SeNPs. The SeNPs have been prepared using ascorbic acid with a hydrothermal method and an ecofriendly approach. The SeNPs have been 75-100 nm in size and have shown a Fourier transform infrared spectroscopy (FTIR) peak at 479 cm^-1, which corresponds to the stretching and bending vibrations of the Se-O. Liposomes have been easily synthesized using the thin film technique, and levothyroxine and SeNPs have both been loaded by encapsulation. The encapsulation yield of levothyroxine into liposomes has been found to be 91.4%, which has been calculated spectrophotometrically. The SeNP content in the liposomes has been determined using inductively coupled plasma mass spectrometry (ICP-MS). The SeNPs and drug-encapsulated liposomes have been coated with PEG for potential oral usage, and their structure has been verified with FTIR. The levothyroxine release from the liposomal form has been higher in a pH 6.8 buffer than that in a pH 7.4 buffer, and the release has been observed to be in a controlled and constant manner with diffusion characteristics. Thus, we suggest that a PEG-coated liposomal delivery system containing both levothyroxine and SeNPs has been developed successfully, and it could be a promising approach for enhanced oral treatment of hypothyroidism.