Saffron extract self-assembled nanoparticles to prolong the precorneal residence of crocin

Saffron has been widely proposed for the treatment of different ocular pathologies, thanks to the anti-inflammatory properties of crocin and crocetin. The aim of this study was to prepare self-assembling saffron extract nanoparticles (SE-NPs) in the presence of chitosan without the addition of any cross-linker. After lyophilization by adding trehalose, SE-NP resulted spherical, 311.6 ± 7.7 nm in size and having a zeta potential of 25.4 ± 0.9 mV. Furthermore, SE-NP were able to protect both polyphenols and crocin from degradation for at least 4 h in simulated tear fluid. NPs formation was due to hydrogen bonds and hydrophobic interaction between saffron extract and chitosan, as demonstrated by FTIR spectra. Thanks to their positive surface charge, SE-NP were able to increase the residence time of crocin in the precorneal area by 2.7 times compared to free crocin. Since lyophilized SE-NP showed a good storage stability they could represent a manageable formulation for application in the eyes.