Synthesis and application of poly(ethylene glycol)-cholesterol (Chol-PEGm) conjugates in physicochemical characterization of nonionic surfactant vesicles.

Vesicles possessing poly(ethylene glycol) (PEG) chains on their surface have been described as a blood-persistent drug delivery system with potential applications for intravenous drug administration. In this research with different molecular weights (400-10,000g/mol) of PEG, a series of Chol-PEG(m) conjugates were generated by the DCC (N,N'-dicyclohexylcarbodiimide, DCC)/(4-dimethylaminopyridine, 4-DMAP) esterification method, and confirmed by FT-IR and (1)H NMR spectrum. Then their properties in aqueous solution were studied by electron microscopy images, associative behavioral and systematic tensiometric studies over a wide concentration range. In order to elucidate the application of this Chol-PEG(m) in vesicles, conventional nonionic surfactant vesicles (niosomes) composed of span 60 and cholesterol were prepared and the influence of various hydrophilic chains of the Chol-PEG(m) conjugates was investigated. Results indicated that all the niosomes prepared, with or without Chol-PEG(m) composition were similar in micrograph with diameter between 120 nm and 180 nm. The fixed aqueous layer thickness (FALT) around niosomes increased as Chol-PEG(m) chain length increase, particularly in the Chol-PEG(10,000) modified niosomes with 9.33+/-0.67 nm. In vitro release experiments indicated that release rate of nimodipine from Chol-PEG(m) modified niosomes was enhanced. Chol-PEG(m) modified niosomes showed greater accumulative release than that of plain niosomes over a period of 24 h. These studies have shed some light on the suitability of Chol-PEG(m) containing niosome preparation.

Deposition of insulin powders for inhalation in vitro and pharmacodynamic evaluation of absorption promoters in rats.

AIM: To prepare insulin powder for inhalation by spray-drying technology, determine the deposition of the insulin powder formulation in vitro and preliminarily investigate hypoglycemic response of the dry powder with/without absorption promoters. METHODS: The depositions of the insulin powder for inhalation were determined by the China Pharmacopoeia 2000 version addenda XH and hypoglycemic effects were evaluated by testing serum glucose with glucose oxidase-peroxidase (GOD-PAP) method. RESULTS: The depositions of the spray-dried insulin powder for inhalation were more than 40% under various humidity and their changes were not significant when air flow was no less than 18 L x min(-1). The coadministration of insulin with 8 mmol x L(-1)/dose sodium taurocholate [PA = 59.91%, Cnadir = (33 +/- 6) %] and 10 mmol x L(-1)/dose sodium deoxycholate [PA = 47.46% , Cnadir = (32 +/- 7)%] induced a significantly greater decline in blood glucose levels, while coadministration with 1% sodium caprylate, 1% sodium dodecyl sulfate, 250 microg/dose lecithin, 10 mmol x L(-1)/dose EDTA appeared to have no significant effect (P > 0.05). CONCLUSION: Insulin powder for inhalation was relatively stable under various humidity conditions and different flow current. The use of 8 mmol x L(-1)/dose sodium taurocholate and 10 mmol x L(-1)/dose sodium deoxycholate could be able to potentially improve the bioavailability of insulin by pulmonary route.