Controlled Release of Model Substances from pH-Sensitive Hydrogels

pH-Sensitive hydrogels of the poly(methacrylic acid-comethyl methacrylate) (MAA/MMA) type, 22/78 molar % with different cross-linking percentages (0.3 and 0.5%) were synthesized. These gels were loaded with a model hydrophilic compound (dichlorobromophenol blue dye, DCBFB) with the aim of evaluating its release at different pH values (1.2, 5.0, 6.8, 7.4). The swelling degree and the release from these hydrogels are highly dependent on the pH of the dissolution medium and on the cross-linking degree. Scanning electron microscopy and differential scanning calorimetry studies demonstrated that part of the dye is embedded in crystal form within the hydrogel. The release profiles of the hydrogels assessed at pH = 6.8 and 7.4 were adjusted to the Higuchi model, regarding them asmatrix delivery systems.

Improvement of N-Acetylcysteine Loaded in PLGA Nanoparticles by Nanoprecipitation Method

N-Acetylcysteine (NAC) is a hydrophilic compound with a low bioavailability. It has been used as an effective antioxidant agent. This research seeks to enhance the entrapment of NAC in PLGA nanoparticles for drug delivery systems. The nanoparticles were made using the nanoprecipitation method and changing the following parameters: the solvent/nonsolvent nature, its viscosity, pH, NAC addition to the nonsolvent, the polymer concentration and molecular weight, and NAC concentration in the solvent. The results showed that an increase in the nonsolvent viscosity produces NAC concentration in the solvent, and the nonsolvent rises its entrapment in the nanoparticles. Nanoparticles with 235.5 ± 11.4 nm size with an entrapment efficiency of 0.4 ± 0.04% and a specific load of 3.14 ± 0.33% were obtained. The results suggest that besides efficiently entrapping hydrophobic compounds, the nanoprecipitation method also has a high potential as an alternative entrapment method for hydrophilic compounds as well. However, its use in the pharmaceutical industry, as a proper specific load vehicle, still depends on the improvement of the load capacity.

Effect of Various Nonionic Surfactants Incorporated in Liposomes on Dermal Delivery of Hydrophilic Compound

Various surfactants-containing vesicles have been widely used as a carrier in drug delivery to enhance skin penetration of encapsulated therapeutic agents. The purpose of this study was to investigate the effect of nonionic surfactants-containing liposome vesicles on the penetration of hydrophilic compounds through the porcine skin. Ultradeformable liposomes composed of phosphatidylcholine (PC), cholesterol (Chol) and various surfactants e.g. Tween 20, Labrasol and Gelucire 44/14) were prepared as NaFI carrier. The physicochemical characteristic of liposomes and in vitro skin penetration were investigated. The particle size of surfactant-containing liposome vesicles showed smaller particle sizes (36 to 54 nm) than conventional liposome (CLs) and had negative surface charge. The EE% and LE% order of surfactants incorporated in liposome formulations were: Labrasol liposomes (LALs) > Gelucire 44/14 liposomes (GELs) > Tween20 liposomes (TWLs) > CLs. The flux of NaFI from ultradeformable liposomes was significantly higher than from CLs. Among various liposomes, Labrasol containing ultradeformable liposomes showed the highest skin permeation in 24 h, and their flux was significantly higher (p < 0.05) than the flux of CLs. The result suggests that the surfactant-containing liposomes were small and deformable vesicles due to incorporating of an edge activators. In addition, surfactants could act as a penetration enhancer to promote dermal delivery of NaFI.