The role of the conformational profile of polysaccharides on skin penetration : the case of hyaluronan and sulfates thereof

The information on passive diffusion of hyaluronic acid through the human skin is scantily investigated and contrasting data are reported in literature. As an example, some authors reported that hyaluronic acid (HA) was unable to penetrate the stratum corneum in in vitro experiments due to its high hydrophilicity. Another study, performed in vivo by applying to human forearm a gel loaded by 3% w/w radiolabelled HA, revealed that HA was able to penetrate into the skin reaching the dermis within 30 min. Aiming to elucidate the penetration mechanism of HA through human epidermis, the present work focused the attention on the impact of molecular weight, conformation and polarity on the diffusion process of polysaccharides using low- and medium-molecular weight HA and the corresponding derivatives at different degree of sulfation (HASx).