Hydrophilic gels containing chlorophyllin-loaded liposomes: development and stability evaluation

The aim of this study was to develop and characterize hydrophilic gels containing chlorophyllin(CHL)-loaded liposomes as well as to evaluate their stability. Two different CHL-loaded liposome dispersions using non-hydrogenated and hydrogenated soybean lecithin were prepared, characterized for their particle size, polydispersity index and trapping efficiency and incorporated in Carbopol 940 NF hydrogel. The gels obtained were analyzed for flow properties, pH values and CHL content. The control liposome-free gel was obtained by incorporating the CHL solution in the hydrogel. The stability of the gels was evaluated in terms of rheological properties, pH values and CHL content during 6 months' storage at 20 +/- 2 degrees C. Suitable gel formulations for topical use were obtained revealing shear-thinning plastic flow behaviour without significant thixotropy during the whole period of examination. High yield values of the samples during the whole period indicated a long-term stability of the gel formulations. The gel formulations expressed a mild acid value acceptable for topical preparations. After 6 months' storage the CHL content was highest in the gel containing non-hydrogenated lecithin liposomes, followed by the gel containing hydrogenated lecithin liposomes and liposome-free gel, indicating that the encapsulation of CHL in liposomes led to a greater stability of CHL.