Sami-Pekka Hirvonen

Temperature controlled release from polystyrene-block-poly(N-isopropylacrylamide-block-polystyrene block copolymer hydrogel

We report temperature controlled release from thermo-responsive polystyrene-block-poly(N-isopropyl acrylamide)-block-polystyrene triblock copolymer hydrogel. The hydrogel swelling and release of water soluble methyl orange are studied as a function of temperature for bulk and for two nano-confinements: cylindrical electrospun nanofibres and spherical aerosol nanoparticles. The time for 80% release from bulk hydrogel is found to be dependent on temperature. At room temperature the 80% release takes in 3 h whereas at 40 °C the same release takes 60 h. The swelling was found to be dependent on temperature and polymer composition.

Melt-electrospinning as a method to improve the dissolution and physical stability of a poorly water-soluble drug

&NA; The present study introduces a modified melt‐electrospinning (MES) method for fabricating the melt‐electrospun fibers (MSFs) of a poorly water‐soluble drug and carrier polymer. The MES of poorly water‐soluble model drug indomethacin (IND) and hydrophilic carrier polymer, Soluplus® (SOL) were prepared at a 1:3 drug‐polymer weight ratio. Water was used as an external plasticizer to regulate a MES processing temperature and to improve fiber formation. The fiber size, surface morphology, physical solid state, drug‐polymer (carrier) interactions, thermal and chemical stability and dissolution behavior of MSFs were investigated. Solid state nuclear magnetic resonance spectroscopy (NMR) was used to measure T1(1H), and the domain size of IND in MSFs (25–100 nm) was calculated from these results. Solid‐state and thermal analysis confirmed the presence of amorphous solid dispersions of IND and SOL. IND was found to be chemically stable during an entire MES process. Only small drug content variability of different MSF batches was detected with high performace liquid chromatography (HPLC). Given findings were verified with the liquid NMR spectroscopy. The dissolution of MSFs was significantly faster than that of physical mixtures (PMs) or pure drug. The enhanced dissolution of MSFs was caused by high surface area, amorphous state of the drug and solubilizing properties of the carrier polymer (SOL). Graphical abstract Figure. No caption available.