Encapsulation of camphor in cyclodextrin inclusion complex nanofibers via polymer-free electrospinning: enhanced water solubility, high temperature stability, and slow release of camphor

Abstract

Electrospinning of polymer-free nanofibers (NF) was successfully performed from inclusion complexes (ICs) of modified cyclodextrins [hydroxypropyl-β-cyclodextrin (HPβCD) and hydroxypropyl-γ-cyclodextrin (HPγCD)] and camphor (HPβCD/camphor-IC-NF and HPγCD/camphor-IC-NF). Although camphor is a volatile and hydrophobic essential oil component, the improvement in the aqueous solubility and thermal stability of camphor by inclusion complexation with cyclodextrins was confirmed by phase solubility diagram and thermal analysis, respectively. Moreover, fast-dissolving characteristics of electrospun CD/camphor-IC-NF webs were also observed. Computational modeling study shows preferential orientation of camphor is variable depending on the CD types. In addition, the interaction of camphor molecule is slightly stronger with HPγCD when compared to HPβCD owing to the better allocation of guest (camphor) in host (CD) cavity originating from the better size match. Even though camphor has high volatility, significant amount of camphor was preserved in HPβCD/camphor-IC-NF and HPγCD/camphor-IC-NF after electrospinning. The molar ratio of HPβCD:camphor and HPγCD:camphor was determined as ~ 1.00:0.65 and ~ 1.00:0.90 in HPβCD/camphor-IC-NF and HPγCD/camphor-IC-NF, respectively. In short, encapsulation of camphor in cyclodextrin inclusion complex nanofibers via polymer-free electrospinning was attained, and enhanced water solubility, high temperature stability, and slow release of camphor were achieved for CD/camphor-IC-NF.