orabase and fluorexon

pH-sensitive microgels were prepared by crosslinking carboxymethylcellulose (CMC) and polymeric beta-cyclodextrin (PbetaCD) using (2-hydroxyethyl)trimethylammonium chloride benzoate (TMACB) as a crosslinker. PbetaCD was prepared by reacting epichlorohydrin and beta-CD in an aqueous phase (NaOH solution, 30% (w/w)). TMACB will interact with CMC by an electrostatic interaction and it will also interact with PbetaCD by a hydrophobic interaction. The size of microgel was tens of nanometers to several micrometers. The degree of calcein release in 24h from the microgels was as low as 23% at pH 8.0. The degree of release at pH 3.0 was almost 100%. The carboxyl groups of CMC will lose their charge in an acidic condition and they would lose their ability to form salt bridges with TMACB, leading to the disintegration of microgels. The degree of release at pH 11, about 47%, was less than the value at pH 3.0 but it was greater than the value at pH 8.0. The CMC will be strongly electrostatically charged in the alkali condition, so the microgels would swell due to the electrostatic repulsion among CMC molecules, which could promote the release of their contents.

Topics: beta-Cyclodextrins; Carboxymethylcellulose Sodium; Chemistry, Pharmaceutical; Cross-Linking Reagents; Drug Carriers; Fluoresceins; Gels; Hydrogen-Ion Concentration; Hydrophobic and Hydrophilic Interactions; Particle Size; Quaternary Ammonium Compounds; Salts; Static Electricity

Liposome entrapment in films consisting of gelatin (GEL) or GEL/sodium carboxymethylcellulose (NaCMC) mixtures, as a method to alter drug release kinetics from polymeric films and/or incorporate sensitive bioactive molecules in solid films, was investigated. Bulk or thin complex (liposome trapping) films were formed by crosslinking (with glutaraldehyde) solutions of GEL or GEL/NaCMC in presence of calcein-encapsulating or rhodamine-labeled liposomes (Rho-Lip). Rho-Lip were observed by confocal microscopy to be homogenously distributed in the films. Calcein release from films was evaluated for periods up to 25 d, and it was found that several possibilities, concerning the release of the liposome-encapsulated molecule from the films, are offered; (i) Release can be sustained, if large liposomes are entrapped in the films. In this case the liposome-encapsulated molecules are released from the films only after they have been released from the vesicles, and the release can be controlled by modifying the film composition, the network density and/or the film geometry. (ii) Intact small unilamellar liposomes (SUV) can be released from the polymeric films depending on their swelling degree. The later can be controlled by modulating the film composition and amount of crosslinker. Film composition also affects the integrity of the film-entrapped liposomes during the crosslinking process, possibly due its effect on the density of the polymeric network of the film.

Topics: Carboxymethylcellulose Sodium; Fluoresceins; Gelatin; Liposomes; Microscopy, Confocal