Nanoemulsions containing a synthetic chalcone: Photodegradation, in vitro release, and interaction studies

• Release and photodegradation profiles of chalcone-loaded nanoemulsions were assessed.
• Interactions between the chalcone and components were evaluated by DSC, NMR and FTIR.
• System structural arrangement influences the chalcone release and photodegradation.

Two different nanoemulsions containing a synthetic chalcone (SC) were prepared and characterized with respect to SC release and photodegradation profiles using Franz diffusion cells and a short-wavelength ultraviolet radiation (UVC) light chamber, respectively. In order to explain the differences observed in the behavior of these two formulations, the interactions between the SC and the components of the nanocarriers were investigated by Differential Scanning Calorimetry (DSC), Nuclear Magnetic Resonance (NMR) and Fourier Transform Infrared (FTIR) techniques. DSC and NMR measurements showed that SC seems to interact with the polysorbate 20 and medium chain triglycerides groups in the formulation composed by soy lecithin and polysorbate 20 (LP20). On the other hand, the interaction of SC with the formulation composed by sorbitan monooleate and polysorbate 80 (SP80) seems to affect the sorbitan monooleate and medium chain triglycerides groups. FTIR findings showed that SC decreases the mobility of the methylene group and displaces phosphate one in the LP20 system. In the SP80 formulation, it was observed that SC displaces the methylene chains groups, increasing the mobility of the carbonyl group. Our results indicate that the system structural arrangement might influence the SC release profile and photodegradation, since LP20 presented lower fluidity, thereby lower amount of SC released and higher photostability, whereas the opposite behavior was observed for SP80.