Thermosensitive hydrogels are of great interest for in situ gelling drug delivery. The thermosensitive vehicle with a gelation temperature in a range of 30-36°C would be convenient to be injected as liquid and transform into gel after injection. To prepare novel hydrogels gelling near body temperature, the gelation temperature of poloxamer 407 (PX) were tailored by mixing PX with poly(acrylic acid) (PAA). The gelation behaviors of PX/PAA systems as well as the interaction mechanism were investigated by tube inversion, viscoelastic, shear viscosity, DSC, SEM, and FTIR studies. The gelation temperature of the plain PX solutions at high concentration of 18, 20, and 22% (w/w) gelled at temperature below 28°C, which is out of the suitable temperature range. Mixing PX with PAA to obtain 18 and 20% (w/w) PX with 1% (w/w) PAA increased the gelation temperature to the desired temperature range of 30-36°C. The intermolecular entanglements and hydrogen bonds between PX and PAA may be responsible for the modulation of the gelation features of PX. The mixtures behaved low viscosity liquid at room temperature with shear thinning behavior enabling their injectability and rapidly gelled at body temperature. The gel strength increased, while the pore size decreased with increasing PX concentration. Metronidazole, an antibiotic used for periodontitis, was incorporated into the matrices, and the drug did not hinder their gelling ability. The gels showed the sustained drug release characteristic. The thermosensitive PX/PAA hydrogel could be a promising injectable in situ gelling system for periodontal drug delivery.
From the controlled drug release and muco/bioadhesive properties of these coated AMX-alginate beads, we suggest that the alginate-coated beads might be a promising drug delivery system to assist with the eradication of Helicobacter pylori infections.
Solid dispersions of felodipine in polyvinylpyrrolidone (PVP) K90 films were prepared by a solvent evaporation method using various volume ratios of dichloromethane (DM) and ethanol (E). Compared to the others, the solubility parameter of the binary mixtures of DM/E at 5/5 was most close to the solubility parameter of PVP. DSC analysis revealed a single glass transition temperature (Tg) of the felodipine/PVP films, suggesting that felodipine and PVP were miscible. As indicated by DSC and dynamic mechanical analysis, the Tg of the felodipine/PVP film prepared by using a DM/E of 5/5 was higher than those prepared using other DM/E ratios. This high Tg could reflect the high rigidity of this felodipine/PVP film and a high interaction between felodipine and PVP. Using this DM/E ratio, which is a good solvent for this system, the PVP chain elongation could be promoted and provided for a better interaction with felodipine. This strong interaction accounts for the felodipine/PVP film rigidity. Furthermore, according to the texture analysis, the felodipine/PVP film prepared by a DM/E of 5/5 gave the highest Young's modulus and indicated a high polymer chain rigidity. FTIR indicated an interaction of PVP and felodipine. According to the PXRD, all felodipine/PVP films were in the amorphous state and this amorphous state remained for more than 2 months. Thus a film prepared by a DM/E of 5/5 showed the highest stability of its amorphous state after being kept for 2 months.
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