NEW DELIVERY SYSTEMS FOR RETINOIDS APPLICATION

Vitamin A is essential for the growth, differentiation and function of epithelial tissue. Low serum retinol levels have been associated with an increased risk of malignant disease. Natural and synthetic retinoids are active in several types of premalignant skin lesions such as keratoacanthoma, actinic keratosis and basal cell carcinoma One of the less toxic vitamin A analogues studied is fenretinide (4 hydroxypropyl phenyl retinamide), a synthetic amide derivative of all-trans- retinoic acid. It has been applied in the chemoprevention and in the treatment of different types of malignancies including breast cancer, neuroblastoma, prostate, ovary, and skin tumours (e.g. basal cell carcinoma) and some other skin diseases (e.g. actinic keratosis). Advanced topical formulations to be applied on skin should be desirable in order to locally treat cutaneous pathologies. Scientific researches are always in progress in order to develop new specialized vehicles able to assure targeted delivery of actives, minimizing at the same time toxic systemic effects. Solid Lipid Nanoparticles (SLN) have been firstly designed for i.v. administration and recently investigated for peroral and transdermal application. Their solid matrix should be able to protect chemically labile agents from degradation and to modulate drug release profiles. Skin care studies performed by the use of SLN indicate an increase in skin hydration and a reduction in wrinkle depth, moreover SLN can improve uptake of cosmetic agents. The lecithin organogel consists of reversed polymer-like micelles. They are generated from the initial spherical ones by dissolving trace amounts of water in a nonaqueous solution. The micellar aggregates entangle, forming a temporal three-dimensional network in the bulk phase. These gel-like reverse micellar systems are particularly interesting for dermocosmetic applications due to their ability to solubilize substances with different chemico-physical properties, their thermodynamic stability and their biocompatibility. Niosomes, vesicles prepared by non-ionic surfactants, have recently been largely proposed as drug delivery systems. This class of vesicles, structurally very similar to liposomes, was introduced in reason of the higher chemical stability of the surfactants compared to that of phospholipids. In particular the present study concerns the design and characterization of SLN, organogels and niosomes as vehicles for retinoids such as fenretinide and rethinyl acetate.