DHA and l-carnitine loaded chitosan hydrogels as delivery systems for topical applications A Physicochemical and engineering aspects

The development of biocompatible hydrogels that allow the controlled release of active components has important applications. In this paper, we report the preparation and characterization of genipin crosslinked chitosan hydrogels loaded with two active components, namely dihydroxyacetone (DHA) or 3-hydroxy-4-trimethylammonium butyrate (l-carnitine), which are used in cosmetics for skin tanning and antiaging effects, respectively. The rheological properties of these hydrogels, as well as their gelling time were investigated. The oscillatory time sweep method was used to monitor the dynamic viscoelastic parameters during in situ gelation experiments, enabling the determination of the gelation time. On the other hand, the effect of the crosslinker concentration, the concentration of active component loaded, and aging time on the rheological properties of hydrogels was also evaluated. It was found that the presence of DHA prolonged hydrogel gelation, if compared to non-loaded or l-carnitine loaded hydrogels at a constant genipin concentration. The slower gelation process observed for DHA loaded hydrogels was due to the existence of DHA-polymer interactions, demonstrated through NMR and DSC characterization. Finally, DHA and l-carnitine release from crosslinked chitosan hydrogels was measured. The results showed that crosslinked hydrogels produced a retarded and more sustained release, in comparison to aqueous solutions and non-crosslinked hydrogels. Such information could give a clear picture on the potential use of chitosan hydrogels, loaded with either DHA or l-carnitine, as delivery systems for topical application of cosmetic ingredients.