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

Electrospinning of polymer-free nanofibers (NF) was successfully performed from inclusion complexes (ICs) of modified cyclodextrins [hydroxypropyl-beta-cyclodextrin (HP beta CD) and hydroxypropyl-gamma-cyclodextrin (HP gamma CD)] and camphor (HP beta CD/camphor-IC-NF and HP gamma CD/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 HP gamma CD when compared to HP beta CD 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 HP beta CD/camphor-IC-NF and HP gamma CD/camphor-IC-NF after electrospinning. The molar ratio of HP beta CD:camphor and HP gamma CD:camphor was determined as similar to 1.00:0.65 and similar to 1.00:0.90 in HP beta CD/camphor-IC-NF and HP gamma CD/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.