Quantitative analysis of natural cyclodextrins by high-performance liquid chromatography with pulsed amperometric detection: application to cell permeation study.

Simple HPLC-PAD methods were developed for quantitation of cyclodextrins (CDs) in aqueous matrices from in vitro cell permeation studies. C-18 solid-phase extraction was used for sample pretreatment. Samples were analysed using acetonitrile-water mobile phase with post-column alkalization by 0.5M NaOH. Zorbax SB-Aq (for alpha-CD) and Zorbax SB-Phenyl (for beta-CD and gamma-CD) columns gave excellent peak shape and sufficient resolution of CD to glucose (2.7-3.2). The methods showed good concentration-response relationship (r > or = 0.999), precision (RSD% 0.7-5.1), repeatability (RSD% 3.4-13.7) and accuracy (87-107%). The limits of quantitation were 0.78, 0.46 and 0.52 microg/ml for alpha-CD, beta-CD and gamma-CD (RSD% of 10.6, 8.1 and 16.3, respectively).

In vitro toxicity and permeation of cyclodextrins in Calu-3 cells.

Cyclodextrins (CDs) can improve the pulmonary drug delivery by increasing aqueous solubility, absorption and bioavailability of drugs. Although the systemic absorption of CDs from gastrointestinal tract is very limited, their systemic absorption after pulmonary administration cannot be excluded. The aims of this study were 1) to evaluate the in vitro toxicity of various CDs (alpha-, beta-, gamma-, hydroxypropyl-alpha-, hydroxypropyl-beta- and randomly methylated-beta-CD) in pulmonary Calu-3 cells and Calu-3 cell layers using MTT and LDH cytotoxicity tests, and 2) to study the permeation of natural CDs (alpha-, beta- and gamma-CD) at non-toxic concentrations across Calu-3 cell layers. Randomly methylated-beta-CD evoked cell death and membrane damage in Calu-3 cells at lower concentrations compared to the other CDs tested. In terms of their toxicity, gamma-CD, hydroxypropyl-beta-CD and hydroxypropyl-alpha-CD were the safest to the Calu-3 cells. Based on the cumulative penetrated amount at 4 h, the apparent permeability coefficients for alpha-, beta- and gamma-CD were 6.77+/-2.23 x 10(-8), 6.68+/-0.84 x 10(-8) and 6.71+/-0.74 x 10(-8) cm/s, respectively. In conclusion, this study indicates that 1) in terms of their local safety, hydroxypropylated CDs and natural gamma-CD seem to be the safest of the tested CDs in pulmonary drug delivery, and 2) cyclodextrins may be absorbed into the systemic circulation from the lungs.

Crystal structure changes of gamma-cyclodextrin after the SEDS process in supercritical carbon dioxide affect the dissolution rate of complexed budesonide.

PURPOSE: The present study describes the crystal structure changes of gamma-cyclodextrin (gamma-CD) during the solution enhanced dispersion by supercritical fluids (SEDS) process and its effect on dissolution behaviour of complexed budesonide. MATERIALS AND METHODS: gamma-CD solution (10 mg/ml in 50% ethanol) was pumped together with supercritical carbon dioxide through a coaxial nozzle with or without a model drug, budesonide (3.3 mg/ml). The processing conditions were 100 b and 40, 60 or 80 degrees C. gamma-CD powders were characterised before and after vacuum-drying (2-3 days at RT) with XRPD, SEM and NMR. Budesonide/gamma-CD complexation was confirmed with DSC and XRPD. The dissolution behaviour of complexed budesonide was determined in aqueous solution (1% gamma-CD, 37 degrees C, 100 rpm). RESULTS: During the SEDS process (100 b, 40 and 60 degrees C), gamma-CD and budesonide/gamma-CD complexes crystallized in a tetragonal channel-type form. The vacuum-drying transformed crystalline gamma-CD into amorphous form while the complexes underwent a tetragonal-to-hexagonal phase transition. The increase in the processing temperature decreased the crystallinity of gamma-CD. At 80 degrees C, amorphous gamma-CD was obtained while the complexes crystallized in a hexagonal channel-type form. The dissolution behaviour of budesonide/gamma-CD complexes was dependent on their crystal structure: the tetragonal form dissolved faster than the hexagonal form. CONCLUSIONS: The crystal structure of gamma-CD and subsequently, the dissolution rate of complexed budesonide, can be modified with the processing conditions.

Preparation of budesonide/gamma-cyclodextrin complexes in supercritical fluids with a novel SEDS method.

The aim was to investigate if solid drug/cyclodextrin complexes could be produced in a single-step process with a solution enhanced dispersion by supercritical fluids (SEDS) method. Budesonide and gamma-cyclodextrin (CD) solutions (50% or 99.5% ethanol) were pumped from the same (conventional method) or separate (modified method) containers together with supercritical carbon dioxide through a coaxial nozzle into a particle formation chamber. The pressure was maintained at 100, 150 or 200 bar with a temperature of 40, 60 or 80 degrees C. SEDS-processed powders were characterised with HPLC, DSC and XRPD for budesonide content, complexation and crystallinity. The budesonide dissolution rate was determined in 1% gamma-CD aqueous solution. Solid, white budesonide/gamma-CD complex particles were formed using the conventional and modified SEDS processes. The complexation efficiency was dependent on the processing conditions. For example, with the conventional method (100 bar, 60 degrees C) the yield of the powder was 65+/-12% with 0.14+/-0.02 mg budesonide/mg powder, corresponding to 1:2 drug:CD molar ratio. The dissolution rate of this complexed budesonide (93+/-2% after 15 min) was markedly higher compared to unprocessed micronised budesonide (41+/-10%) and SEDS-processed budesonide without CD (61+/-3%). As a conclusion, SEDS is a novel method to produce solid drug/CD complexes in a single-step process.