Release of liposome-encapsulated calcein from liposome entrapping gelatin-carboxymethylcellulose films: A presentation of different possibilities

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 cl, 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.