Agnieszka A. Gola

Theoretical kinetic study of the formation reactions of methanol and methyl hypohalites in the gas phase.

CH3OX molecules (X = H, F, Cl and Br) can be formed in the atmosphere by the CH3 + OX and CH3O + X recombination reactions. In the present study the results of a theoretical analysis of the kinetics and thermochemistry of this class of reactions are presented. The molecular properties of the reactants and products were derived from ab initio calculations. The high-pressure limiting rate constants for the recombination reactions were evaluated using a version of the statistical adiabatic channel model. The kinetic equations derived in this study allow a description of the kinetics of the reactions under investigation in the temperature range of 200–500 K.

Synthesis and Formulation of Thermosensitive Drug Carrier for Temperature Triggered Delivery of Naproxen Sodium

Nanospheres and microspheres are known as a multipurpose compounds and are used in various branches of science. Recent controlled delivery systems for drugs are also based on poly-micro and nanospheres. In our study we describe an investigation of the influence of thermosensitive polymer N-isopropylacrylamide (NIPA) on the release of the drug naproxen sodium (NS) with a hydrogel hydroxypropyl methylcellulose (HPMC) base. The hydrodynamic diameter (DH) of the obtained polymer was measured by using dynamic light scattering (DLS) at a wavelength of 678 nm. Hydrogel formulations of NS were prepared in a specific way ex tempore. NS was sprinkled on the surface of a distilled water, then polymer soluted in water was added. Afterward, HPMC was affixed to the solution. Prepared samples were stored at room temperature for 24 h. Release tests showed that modification of thevcross-linker type influenced the properties of synthesized polymeric particles. The NIPA derivatives obtained via surfactant free precipitation polymerization (SFPP) may be formulated as hydrogel preparations using HPMC. The obtained formulations presented varied half-release times, depending on the type of applied NIPA derivatives in hydrogel formulations. At 18 °C, the release rates were lower comparing to the reference HPMC hydrogel, whereas at 42 °C, the release rates were significantly higher. The synthesized thermosensitive polymers enabled temperature-triggered release of NS.

The Influence of Anionic Initiator on the Selected Properties of Poly-N-Isopropyl Acrylamide Evaluated for Controlled Drug Delivery

The aim of the study was to monitor the influence of increasing initiator concentrations on the properties of poly-N-isopropylacrylamide (polyNIPA) nanoparticles obtained via surfactant free precipitation polymerization (SFPP). In all studied systems P-001 to P-1, the same amount of monomer was used, and increasing amounts of potassium persulphate (KPS). The course of each reaction was monitored by measuring the conductivity of the whole system. The resulting composition of products was confirmed by attenuated total reflectance within Fourier transformed infrared spectroscopy (ATR-FTIR) measurements. The hydrodynamic diameters with polydispersity index (PDI) and zeta potential (ZP) were measured in aqueous dispersions of the synthesized polymers in dynamic light scattering (DLS) device (λ = 678 nm), and were found to be for P-1: 20.33 nm (PDI = 0.49) and −7 mV, for P-05: 22.24 nm (PDI = 0.39) and −5 mV, for P-01: 50.14 nm (PDI = 0.49) and −3 mV, for P-005: 62.75 nm (PDI = 0.54) and −3 mV and for P-001: 509.4 nm (PDI = 0.61) and −12 mV at 18 °C, respectively. Initiator concentration affects the size and ZP of particles. The hydrodynamic diameter decreases with initiator concentration increase, whereas the time of the reaction decreases when the initiator concentration increases. This fact is reflected in the observed values of conductivity in the course of the performed reaction. Evaluated volume phase transition temperature in the range of 32 °C enables further research of the nanoparticles as thermosensitive drug carriers.