Chitosan–sEPDM and Melatonin–Chitosan–sEPDM Composite Membranes for Melatonin Transport and Release

Abstract

Melatonin is the hormone that focuses the attention of the researchers in the medical, pharmaceutical, materials, and membranes fields due to its multiple biomedical implications. The variety of techniques and methods for the controlled release of melatonin is linked to the multitude of applications, among which sports medicine occupies a special place. This paper presents the preparation and characterization of composite membranes based on chitosan (Chi) and sulfonated ethylene-propylene-diene terpolymer (sEPDM). The membranes were obtained by controlled vacuum evaporation from an 8% sEPDM solution in toluene (w/w), in which chitosan was dispersed in an ultrasonic field (sEPDM:Chi = 1:1, w/w). For the comparative evaluation of the membranes’ performances, a melatonin-chitosan-sulfonated ethylene-propylene-diene terpolymer (Mel:Chi:sEPDM = 0.5:0.5:1.0, w/w/w) test membrane was made. The prepared membranes were morphologically and structurally characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), energy-dispersive spectroscopy analysis (EDAX), thermal analysis (TG, DSC), thermal analysis coupled with chromatography and infrared analysis, and contact angle measurements, but also from the point of view of performance in the process of transport and release of melatonin in dedicated environments (aqueous solutions with controlled pH and salinity). The prepared membranes can release melatonin in amounts between 0.4 mg/cm2·per day (sEPDM), 1.6 mg/ cm2·per day (Chi/sEPDM), and 1.25 mg/cm2·per day (Mel/Chi/SEPDM).

Simultaneously Recovery of Thorium and Tungsten through Hybrid Electrolysis–Nanofiltration Processes

“…Membranes of sulfonated polyether–ether–ketone (sPEEK) [ 44 , 45 ] or sPEEK polymer composites [ 46 ] are used in ultrafiltration, nanofiltration, or reverse osmosis processes [ 44 ]. Three samples of 1 cm 2 each from the membrane obtained after fixing with calcium hydroxide and after being kept in ultrapure water are introduced into a Dewar vessel with liquid nitrogen and fractured.…”

“…The membranes based on chitosan have been frequently used to carry out membrane processes for the separation of ions and molecules [ 57 , 58 , 59 , 60 ], but in this work, chitosan membranes are obtained on a polypropylene hollow fiber (C–PHF–M) support. Practically, the polypropylene hollow fiber (PHF) support, which has previously presented ultrafiltration performances [ 44 , 45 , 46 ], is transformed in nanofiltration composite membranes (C–PHF–M) by ultrafiltration of a chitosan solution to obtain in situ a selective layer of chitosan. Samples of 3 cm of the polypropylene hollow fiber membrane and the chitosan–polypropylene hollow fiber membrane were fractured in liquid nitrogen and covered with a superficial layer (50 nm) of gold and characterized by scanning electron microscopy (SEM) ( Figure 8 and Figure 9 ).…”

“…The hollow fibers’ polypropylene support membranes (PHF–M) were provided by GOST Ltd., Perugia, Italy [ 44 ].…”

“…The removal of the sulfate ion is followed by the identification reaction with a 2 mol/L barium chloride solution. The main macroscopic observations, which can be highlighted, in the case of incomplete washing are as follows [ 44 , 45 ]: Undulation of the membrane; The occurrence of defects (microcracks; holes); Local re-solubilizations (transparencies; gelations). …”

Hydrogen Sulphide Sequestration with Metallic Ions in Acidic Media Based on Chitosan/sEPDM/Polypropylene Composites Hollow Fiber Membranes System

“…Two sealing elements were attached to the ends of the assembly of fibers, by immobilization with acrylic polymer ( Figure 2 c). In parallel, the Chi/sEPDM composite membranes and the sEPDM membranes required for characterization as control samples were prepared [ 55 ].…”