Purpose: Nanocrystals holds good potential in delivering poorly soluble anticancer drugs, the surface of which might by functionally-modified by polydopamine (PDA) coating. The present study was to investigate the potential of cationic functionalized PDA-coated NCs as mucoadhesive drug delivery systems for intravaginal administration of imatinib which may avoid adverse effects associated with systemic administration, improve efficacy by assuring adequate local drug concentration and allow convenient self-administration without needing help from professionals
Methods: In this investigation, positively-charged polydopamine-coated imatinib nanocrystals (NC@PDA-NH2) were prepared, which was further dispersed in Pluronic F127-based in situ hydrogel as the vehicle to allow adequate interaction time between nanocrystals and mucosa. In vitro interaction with mucin and cervical cancer-related cell lines, ex vivo residence on mouse vaginal mucosa, in vivo intravaginal retention and anti-tumor efficacy were investigated.
Results: NC@PDA-NH2 showed a near-spheroid shape with the nanoscale size distribution of 209.8 ± 19.3 nm, the positive zeta potential of +27.2±2.9 mV and a relative high DL 42.06±3.20%. Both XRD and DSC curves revealed changes in crystalline types from bulk drug to nanocrystals. The significance of cationic functionalization on the mucoadhesive was shown in vitro by the increasing amount of mucin adsorption with the value of positive zeta-potential and the appearance of a new size distribution peak during mixing of mucin and NC@PDA-NH2. Cationic functionalization also improved the storage stability of nanocrystals, demonstrated by the basically unchanged size after one-month storage.
Data from cellular uptake, cellular growth inhibition efficacy and induction of apoptosis all demonstrated the superiority of NC@PDA-NH2 over unmodified NC or free imatinib. NC@PDA-NH2-containing Pluronic F127-based thermosensitive hydrogel (NC@PDA-NH2/FG) with the Pluronic F127 concentration at 17.5% (w/w) showed suitable thermosensitive rheology and near zero-order release kinetics. When dropped on ex vivo murine vagina mucosa and continuously flushed with vaginal fluid simulant, NC@PDA-NH2/FG resulted in significantly prolonged fluorescent signal than NC-loaded Pluronic F127-based thermosensitive hydrogel (NC/FG) as well as free probe /FG. Prolonged in vivo intravaginal residence and more penetration into vaginal mucosa were also observed after intravaginal administration of NC@PDA-NH2/FG over NC/FG. In mice bearing the orthotopic TC-1 cervical cancer tumor model. Both NC@PDA-NH2/FG and NC/FG demonstrated dose-dependent tumor growth inhibition effect, respectively. More importantly, NC@PDA-NH2/FG inhibited the growth of model tumors more effectively than NC/FG. NC@PDA-NH2/FG prolonged the median survival time by 6 times than free drug/FG（35 d vs. 20 d）and 1.1 times than NC/FG group (35 d vs. 26d) at the dosage of 4mg/kg/2d. More apoptosis areas were observed in the microscopic sections from the NC@PDA-NH2/FG group than the NC/FG group. The body weight of the mice in the NC@PDA-NH2/FG group slowly increased, reflecting their relative good health state, and the H&E staining sections also demonstrated the maximal anti-tumor efficiency and minimal mucosal toxicity for the NC@PDA-NH2/FG group.
Conclusion: In conclusion, cationic functionalization endowed NC@PDA-NH2 good capability of effective interaction with mucin and cervical cancer-related cell lines. When loaded in F127-based thermosensitive hydrogel, they can be easily administered into the vagina of mice, showing significantly improved ex vivo residence on mouse vaginal mucosa, in vivo intravaginal retention and anti-tumor efficacy against the orthotopic TC-1 cervical cancer tumor model. To our knowledge, this is the first presentation of nanocrystal-based vaginal delivery against cervical cancers.