Violeta Turcuş

TG/DTG/DTA data used for determining the kinetic parameters of the thermal degradation process of an immunosuppressive agent: mycophenolate mofetil

Mycophenolate mofetil is a strong immunosuppressive therapeutic agent that was primely licensed to prevent rejection of transplanted organs. The decomposition reactions of pharmaceuticals, alongside other processes that occur, are important ones from both fundamental and practical point of view. The thermal stability of pharmaceuticals is important from both fundamental and clinical point of view. Kinetic analysis is one of the best method for an objective and less speculative determination of the Life Time Prediction. Following the ICTAC 2000 Protocol, the thermal behavior of mycophenolate was recorded at five different heating rates, in air atmosphere. The activation energy for the main degradation process was obtained by using four isoconversional methods of kinetic analysis: Friedman, Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose and modified nonparametric kinetic methods. The obtained values of the activation energy were in a very close range.

Thermogravimetric and calorimetric studies performed on memantine hydrochloride to determine its thermal behaviour and possible drug–excipient interactions

Memantine hydrochloride is an adamantane derivative used for the treatment of moderate-to-severe Alzheimer’s disease. Pharmaceutical active compounds and the excipients are in contact with each other a period of time before the pharmaceutical formulation is used by a patient; hence, the storage conditions are very important—humidity and temperature can trigger interactions between a drug and an excipient and these interactions may affect drug bioavailability and even drug safety. For this study, TG/DTG/HF curves were recorded in air flow and they were used to determine the thermal behaviour and some indications about the compatibility of memantine, the single excipients and of the binary mixtures, while FTIR and DSC analysis of the pure compounds and the binary mixtures were used to evaluate possible interactions between the compounds.

Nanoencapsulation techniques for compounds and products with antioxidant and antimicrobial activity - A critical view

Oxidative decay and microbial spoilage are issues of concern, as they constitute threats to human health. Natural antioxidants and antimicrobials hamper the negative impact of synthetic compounds and they need appropriate delivery systems. Different nanostructures can be developed: association colloids-based nanostructures, nanoemulsions, nanoliposomes, nanolaminates, nanofibers, carbon nanotubes, nanocomposites. The main nanoencapsulation techniques applied to antioxidants and antimicrobials are described: association colloid-based nanoincorporation, lipid-based nanoencapsulation techniques, encapsulation techniques based on biologically-derived polymeric nanocarriers, encapsulation techniques based on non-biological polymeric nanocarriers, cyclodextrin incorporation, electrospraying and electrospinning, carbon nanotubes and nanocomposite encapsulation. Several nanoencapsulation methods can be followed by freeze-drying or spray-drying. Protection of bioactive compounds and controlled release are achieved, but the impact of the nanomaterials on human health and on the environment should be considered. The influence of the nanoencapsulation techniques on the antioxidant/antimicrobial activity is discussed. The choice of the appropriate encapsulation method is vital. Bioactivity increase, preservation or decrease, depend on the interactions established between the functional groups of encapsulated compound and the encapsulating nanomaterial.