Release properties of chemical and enzymatic crosslinked gelatin-gum Arabic microparticles containing a fluorescent probe plus vetiver essential oil.

Oil-containing gelatin-gum Arabic microparticles were prepared by complex coacervation followed by crosslinking with glutaraldehyde or transglutaminase. A fluorescent mixture, khusimyl dansylate (KD) as the fluorescent compound mixed to the vetiver essential oil, was used as oil model. The effect of the type of crosslinking of the coacervated gelatin-gum Arabic membrane, the physical state of microparticles, wet or freeze-dried and the type of release media, aqueous with surfactants, Sodium Dodecyl Sulphate (sds) or Tween 80 (tw) and anhydrous ethanol as organic media on the release rate of the KD from the microparticles, was experimentally investigated. It was shown that the oil was dispersed uniformly throughout the microparticles and the chemical crosslinked microparticles were more resistant to swelling, presenting smaller sizes after hydration. Also the crosslinking effect, transglutaminase or glutaraldehyde, could be confirmed by the integrity of the crosslinked gelatin-gum Arabic microparticles after incubation in the aqueous sds media, compared to complete dissolution of the uncrosslinked microparticles in this media. The cumulative fluorescent KD release from the gelatin-gum Arabic microparticles decreased in the following order of dissolution media: anhydrous ethanol>tw>sds and the wet microparticles have shown a faster KD release than freeze-dried ones. A mathematical model was used to estimate the diffusion coefficient (D). The chemically crosslinked gelatin-gum Arabic microparticles ensured a pronounced retard effect in the KD diffusion, presenting a D varying from 0.02 to 0.6 x 10(-11)cm(2)/s, mainly in an aqueous media, against D varying from 1.05 to 13.9 x 10(-11)cm(2)/s from the enzymatic crosslinked microparticles.

Rate-modulating PHBHV/PCL microparticles containing weak acid model drugs.

In this work, we aimed to evaluate the influence of the proportions of poly(epsilon-caprolactone) (PCL) in the poly(hydroxybutyrate-co-hydroxyvalerate) (PHBHV) blended microparticles on the drug release profiles of drug models and to determine the drug release mechanism. Diclofenac and indomethacin used as drug models showed encapsulation efficiencies close to 85%. The average diameters (122-273microm) and the specific surface areas (26-120m(2)g(-1)) of the microparticles were dependent on the PCL concentration in the blends. Differential scanning calorimetry (DSC) analyses showed that the microparticle preparation process influenced the thermal behavior of PHBHV, as well as the glass transition temperature of PHBHV increased with the presence of indomethacin. The release profiles, described by a biexponential equation, showed sustained phase half-lives varying from 131 to 912min (diclofenac) and from 502 to 6300min (indomethacin) depending on the decrease of the PCL concentration. The product between the diffusion coefficient and the drug solubility in the matrix (DC(s,m)), which was proportional to the PCL concentration, was calculated by fitting the release data to the Baker-Lonsdale equation. The mechanism of release was mainly controlled by the drug diffusion and the drug release profiles were controlled by varying the PCL concentration systematically in the blended PHBHV/PCL microparticles.

Microparticles prepared with poly(hydroxybutyrate-co-hydroxyvalerate) and poly(epsilon-caprolactone) blends to control the release of a drug model.

The objective of this work was to verify the influence of the poly(epsilon-caprolactone) PCL concentration in poly(hydroxybutyrate-co-hydroxyvalerate) P(HBHV)/PCL microparticles, prepared by an emulsion/solvent evaporation process, on the release behavior of a drug. Differential Scanning Calorimetry analyses demonstrated that the preparation process increased the crystallite heterogeneity for the P(HBHV) in the particles. The drug caused an increase in the glass transition of the P(HBHV) in the microparticles. Dexamethasone acetate-loaded microparticles demonstrated drug sustained releases (up to 250 h), which profiles fit the biexponential model. The release of dexamethasone acetate caused an increase in the surface area of the microparticles. The kinetic constants of the sustained phase increased with the augmentation of the PCL content in the blend. The drug release mechanism was dependent on the presence of PCL in the microparticles. A Fickian release was determined for the microparticles prepared exclusively with P(HBHV), while non-Fickian release behaviors were found for the P(HBHV)/PCL microparticles.