Development of liposomes containing ethanol for skin delivery of temoporfin: characterization and in vitro penetration studies.

The aim of this study was to develop ethanol-containing (3.3-20%, w/v) liposomes loaded with temoporfin (mTHPC), which presents a highly hydrophobic photosensitizer with low percutaneous penetration, and to investigate their skin penetration enhancing effect. Characterization parameters of liposomes were measured by photon correlation spectroscopy, lamellarity was analyzed by cryo-electron microscopy and mTHPC-content in formulations was determined spectrofotometrically. In order to assess the stability of mTHPC-liposomes at 4 and 23 degrees C, at predetermined time intervals characterization parameters and mTHPC-content were measured. The in vitro skin penetration of mTHPC was investigated using human abdominal skin mounted in Franz cells. The results indicated that mTHPC-liposomes were of a small particle size, small polydispersity index, negative surface charge, unilamellar or oligolamellar, and of a spherical or oval shape. All liposomes were stable during 12 months' storage at 4 degrees C. Increasing the amount of ethanol in mTHPC-liposomes the skin deposition of mTHPC increased also. Liposomes without ethanol delivered the lowest amount of mTHPC into the skin, while liposomes containing 20% ethanol showed the highest penetration enhancement. In conclusion, mTHPC-liposomes containing 20% ethanol could be a promising tool for delivering temoporfin to the skin, which would be beneficial for the photodynamic therapy of cutaneous malignant or non-malignant diseases.