Sparing methylation of beta-cyclodextrin mitigates cytotoxicity and permeability induction in respiratory epithelial cell layers in vitro

摘要

Cyclodextrins (CDs) are promising solubility enhancers for inhaled drug delivery. However, they have dose-dependent effects on the respiratory epithelium, which may have advantages for permeability enhancement but also gives rise to safety concerns. In this study, the methyl thiazol tetrazolium (MTT) assay was used to compare a new sparingly methylated beta-CD, Kleptose (R) Crysme beta (Crysmeb) with the more established CD derivatives hydroxypropyl-gamma-cyclodextrin (HP gamma CD), randomly methylated beta-cyclodextrin (Rameb) and hydroxypropyl-beta-cyclodextrin (HP beta CD). The beta CD derivatives affected cell metabolism in A549 cells in a concentration dependent manner with LD50 of 56, 31 and 11 mM obtained for HP beta CD, Crysmeb and Rameb, respectively. Calu-3 cells were less susceptible to beta CD with an LD50 of 25 mM being obtained for Rameb only. Permeability increases in Calu-3 cell layers were observed with beta CD derivatives and a concentration dependency shown. The mechanism of permeability enhancement and its reversibility was investigated. Rameb produced an irreversible loss of cell layer barrier function at >= 25 mM, but perturbations of epithelial integrity were moderate and reversible in the case of HP beta CD and Crysmeb (25-50 mM). Given its high solubilisation capacity, the low toxicity and transient absorption promoting properties, this study identifies Crysmeb as a promising adjuvant in formulations for inhalation.