LC-UV Determination of Melatonin from Chitosan Nanoparticles

Up-to-date studies regarding the determination of melatonin by chromatographic methods

Melatonin is an indolic compound that has been reported in the literature to exist in human-based samples, vertebrates, vegetables, fruits, and pharmaceutical products. Melatonin is considered a dietary supplement and can regulate circadian rhythms, although it has not been classified as a drug by the US Food and Drug Administration. Several analytical methods have been used for its detection. This study aimed to summarize the recent outcomes of the chromatographic methods such as electrophoretic methods, gas chromatography, and liquid chromatography, which have been used for the determination of melatonin in the last three decades, with the focus on gas chromatography and high-performance liquid chromatography methods.

Melatonin-loaded silica coated with hydroxypropyl methylcellulose phthalate for enhanced oral bioavailability: Preparation, and in vitro-in vivo evaluation

Melatonin (MLT) is a small molecule with low water solubility and high permeability. According to the Biopharmaceutics Classification System, MLT is a class II drug exhibiting a very short half-life and minimal and variable bioavailability. This work aimed to establish a delivery system composed of an enteric MLT nanosphere with favorably controlled and sustained release characteristics superior to those of raw MLT. The nanosphere was composed of hydroxypropyl methylcellulose phthalate (HP55) and silica (SiO₂) with MLT. As a carrier, SiO₂ contains numerous surface pores with high adsorption capacity advantageous for permeability and slow release. HP55 is a good enteric coating material. MLT-loaded SiO₂ was obtained through adsorption in acetone solution. A MLT-loaded SiO₂ coated with HP55 (MLT-SiO₂-HP55) nanosphere was prepared via desolvation. The characteristics of this nanosphere were analyzed through transmission electron microscopy, Brunauer-Emmett-Teller surface area analysis, diffuse reflectance infrared Fourier transform spectroscopy, X-ray diffraction, differential scanning calorimetry, and thermogravimetric analysis. Results show that MLT was loaded mostly in the pores of SiO₂. HP55 was coated on a large portion of MLT-SiO₂. In vitro release studies revealed that the release rate of MLT from MLT-SiO₂ was higher than that of raw MLT in simulated gastric fluid (SGF). The amount of MLT released from MLT-SiO₂-HP55 in SGF was lower than that released from simulated intestinal fluid because of HP55 coated on MLT-SiO₂. In vivo evaluation demonstrated the controlled drug release of MLT-SiO₂-HP55 in rats. Compared with raw MLT, MLT-SiO₂-HP55 prolonged peak time (T_max) from 15min to 30min and increased peak concentration (C_max) from 168.86ng/mL to 383.71ng/mL. The corresponding area under the curve (AUC) of MLT-SiO₂-HP55 was 3.5 times higher than that of raw MLT. This finding illustrated the sustained release of MLT-SiO₂-HP55. Our in vitro release and in vivo absorption studies indicated that the proposed preparation of MLT-SiO₂-HP55 is an effective method to facilitate the controlled and sustained release of MLT with enhanced bioavailability.

Biomedical exploitation of chitin and chitosan via mechano-chemical disassembly, electrospinning, dissolution in imidazolium ionic liquids, and supercritical drying

Recently developed technology permits to optimize simultaneously surface area, porosity, density, rigidity and surface morphology of chitin-derived materials of biomedical interest. Safe and ecofriendly disassembly of chitin has superseded the dangerous acid hydrolysis and provides higher yields and scaling-up possibilities: the chitosan nanofibrils are finding applications in reinforced bone scaffolds and composite dressings for dermal wounds. Electrospun chitosan nanofibers, in the form of biocompatible thin mats and non-wovens, are being actively studied: composites of gelatin + chitosan + polyurethane have been proposed for cardiac valves and for nerve conduits; fibers are also manufactured from electrospun particles that self-assemble during subsequent freeze-drying. Ionic liquids (salts of alkylated imidazolium) are suitable as non-aqueous solvents that permit desirable reactions to occur for drug delivery purposes. Gel drying with supercritical CO₂ leads to structures most similar to the extracellular matrix, even when the chitosan is crosslinked, or in combination with metal oxides of interest in orthopedics.