Boosting the mechanical strength and solubility-enhancement properties of hydroxypropyl-β-cyclodextrin nanofibrous films.

2-hydroxypropyl-s-cyclodextrin (HPsCD) nanofiber films have high surface-to-volume ratio and show high dissolution rate of hydrophobic drugs. However, the solubility-enhancement effect of HPsCD films may not be enough to include an effective dose in a sublingually administrable film. Moreover, unmodified HPsCD films are very brittle and difficultly transported and/or handled. So, the addition of polyethylene glycol (PEG) as a plasticizer was suggested to improve their ultimate tensile strength (UTS) and solubilization of hydrophobic drugs. Accordingly, six nanofiber films were developed and characterized, using three molecular weights of PEG (400, 1500 and 6000 Da) with two concentrations each (1:100 and 2:100 PEG:HPsCD), in addition to the unmodified HPsCD nanofibrous film. The results revealed that adding 1:100 of PEG 400 increases the UTS (∼2-fold) and the average fiber diameter (AFD) (∼3-fold). Moreover, the addition of PEG 400 significantly increased the solubility of two hydrophobic model drugs; coumarin (up to 7.7-fold of the original solubility) and 2-nitroimidazole (up to 1.6-fold of the original solubility). However, with higher PEG concentration/molecular weight, both AFD and UTS of the films decreased. On the other hand, it was noted that the solubility of the two model drugs decreased upon using 1500-Da PEG, and then increased with 6000-Da PEG.