Effects of hydroxypropyl-β-cyclodextrin grafted polyethylenimine (HP-β-CD-PEI) including HP-β-CD-PEI 600 , HP-β-CD-PEI 1800 , HP-β-CD-PEI 10000 on the pulmonary absorption of insulin, calcitonin, 5(6)-carboxyfluorescein (CF) and fluorescein isothiocyanate dextrans (FDs) with various molecular weights (FD4, FD10 and FD70) were examined by an pulmonary absorption study in rats. Pulmonary absorptions of these poorly absorbable drugs were significantly enhanced by HP-β-CD-PEI 1800 and HP-β-CD-PEI 10000 , and HP-β-CD-PEI 1800 with the concentration of 5% (w/v) provided maximal absorption enhancing effect on pulmonary absorption of these model drugs. The toxicity study demonstrated that HP-β-CD-PEI did not induce any toxic action to rat pulmonary membranes. In addition, zeta potential of insulin solution changed to positive by addition of various HP-β-CD-PEI, meanwhile, the degree of positive charge was linearly correlated with absorption enhancing effect of HP-β-CD-PEI, suggesting that positive charge of HP-β-CD-PEI might be related to their absorption enhancing mechanisms for enhancing pulmonary absorption of insulin in rats. In conclusion, HP-β-CD-PEI is a potential and safe absorption enhancer for improving absorption of hydrophilic macromolecules especially peptide and protein drugs by pulmonary delivery.
Context: Oral bioavailability of some hydrophilic therapeutic macromolecules was very poor, thus leading to their limited application in clinic.Objective: To investigate the efficacy, safety and mechanism of HP-β-CD-PEI polymers on the intestinal absorption of some poorly absorbable drugs in rats.Methods: Effects of HP-β-CD-PEI polymers on the intestinal absorptions of drugs were investigated by an in situ closed loop method in rats. The safety of HP-β-CD-PEI polymer was evaluated by measurement of lactate dehydrogenase (LDH) activity and amount of protein released from rat intestinal perfusate. The absorption enhancing mechanisms were explored by the measurement of zeta potential, transepithelial electrical resistance (TEER) and in vitro transport of FD4 (a paracellular marker) across rat intestinal membranes, respectively.Results: HP-β-CD-PEI polymers, especially HP-β-CD-PEI1800, demonstrated excellent absorption enhancing effects on drug absorption in a concentration-dependent manner and the enhancing effect was more efficient in the small intestine than that in the large intestine. Five percent (w/v) HP-β-CD-PEI1800 obviously decreased the TEER, accompanied with increase in the intestinal transport of FD4, indicating that absorption enhancing actions of HP-β-CD-PEI polymers were possibly performed by loosening tight junctions of intestinal epithelium cells, thereby increasing drug permeation via a paracellular pathway. A good liner relationship between absorption enhancing effects of HP-β-CD-PEI polymers and their zeta potentials suggested the contribution of positive charge on the surface of these polymers to their absorption enhancing effects.Conclusion: HP-β-CD-PEI polymers might be potential and safe absorption enhancers for improving oral delivery of poorly absorbable macromolecules including peptides and proteins.
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