Preparation and ex vivo evaluation of TEC as an absorption enhancer for poorly absorbable compounds in colon specific drug delivery

In previous studies, it was established that chitosan and its quaternized derivatives are potent enhancers of hydrophilic compounds absorption across intestinal epithelia. The aim of this study was to evaluate the application of a new quaternized chitosan, triethyl chitosan (TEC), in pharmaceutical approaches. TEC was synthesized by a one step process via a 2(2) factorial design to optimize the preparation conditions. In ex vivo experiments, everted rat colon sac was used to determine the effect of TEC on the penetration of hydrophilic compounds of different molecular masses (e.g., sodium fluorescein and brilliant blue) through colonic epithelia in comparison with chitosan at pH 7.4. These studies indicated a significant increase in absorption of sodium fluorescein and brilliant blue in the presence of TEC compared to chitosan. TEC bearing positive charge is able to interact with the tight junctions of colon epithelia and hence increase the permeation of sodium fluorescein and brilliant blue through the tight junctions. This investigation has shown that triethyl chitosan could be used as a penetration enhancer for poorly absorbable compounds in the colon drug delivery system.     

Oxidation of bisphenol A, 17beta-estradiol, and 17alpha-ethynyl estradiol and byproduct estrogenicity

A human breast cancer cell line (MCF-7) was used to investigate the cumulative estrogenicity profiles elicited during the oxidation of three estrogenic compounds [bisphenol A (BPA), 17beta-estradiol (E2), and 17alpha-ethynyl estradiol (EE2)]. High-performance liquid chromatography (HPLC) with a method detection limit (MDL) of approximately 1 nM was used to measure the initial and final concentrations of test compounds during oxidation. Both chlorination and ozonation removed from 75% to >99% of the test compounds in distilled water. Increasing contact time and chlorination dose improved compound removal. Chlorination byproducts of BPA, E2, and EE2 elicited low levels of estrogenicity over an extended period of time. For equivalent molar oxidant dosages, ozone and chlorine had comparable residual proliferative effect values and >99% loss of the parent compounds. For oxidation studies of estrogenic chemicals, ammonium chloride was found to adequately quench residual chlorine without interfering with cell culture assay. Oxidation of test compounds with chlorine and ozone resulted in a similar estrogenicity trend, with a relative higher level of estrogenicity elicited during the early phases of oxidation, which gradually dissipated over the extended exposure time to a stable point. Oxidation with ozone resulted in the rapid transformation of test compounds, reaching a stabilized estrogenic level in 10 min, whereas for chlorination it took more than 120 min for elicited estrogenicity to stabilize.     

The effect of vehicle on physical properties and aerosolisation behaviour of disodium cromoglycate microparticles spray dried alone or with L-leucine

The aim of this study was to improve the aerosolisation behaviour of disodium cromogycate (DSCG), using spray drying technique. The effect of vehicle on the drug particle properties was investigated. L-leucine was selected as a natural antiadherent amino acid to improve the deagglomeration of DSCG particles. Spray dried samples of DSCG alone or with L-leucine were prepared from water and ethanol under the same conditions. The powder properties of the samples were examined by laser diffraction, helium densitometer, X-ray diffraction, differential scanning calorimetry and thermogravimetric analysis. The in vitro deposition was determined, using an Andersen cascade impactor with a Spinhaler at a flow rate of 60 l/min. An amorphous form of the drug was obtained when water was used. However, crystal transformation of original DSCG in the presence of ethanol during spray drying resulted in production of elongated particles. These particles exhibited improved aerodynamic properties, compared to the amorphous and commercial materials. Significant differences in fine particle fraction were observed using the two vehicles. Co-spray drying of DSCG and L-leucine improved the deposition profiles of the drug. These results indicated that the change in crystal structure of DSCG during spray drying process was susceptible to the nature of the vehicle. A crystalline form of DSCG with good aerodynamic properties was achieved during spray drying process. In addition, the processing of DSCG with L-leucine in a single step using ethanol resulted in an improvement in dispersion properties of the drug particles.     

Purification of recombinant adeno-associated virus type 8 vectors by ion exchange chromatography generates clinical grade vector stock

Recombinant vectors based on the recently isolated AAV serotype 8 (rAAV-8) shows great promise for gene therapy, particularly for disorders affecting the liver. Transition of this vector system to the clinic, however, is limited by the lack of an efficient scaleable purification method. In this report, we describe a simple method for purification of rAAV-8 vector particles based on ion exchange chromatography that generates vector stocks with greater than 90% purity. The average yield of purified rAAV-8 from five different vector preparation was 41%. Electron microscopy of these purified stocks revealed typical icosohedral virions with less than 10% empty particles. Liver targeted delivery of ion-exchange purified rAAV-8 vector encoding the human factor IX (hFIX) gene, resulted in plasma hFIX levels approaching 30% of normal in immunocompetent mice, which is 20-fold higher than observed with an equivalent number of rAAV-5 ion exchange purified vector particles. The method takes less then 5 h to process and purify rAAV-8 vector from producer cells and represents a significant advance on the CsCl density centrifugation technique in current use for purification of rAAV-8 vector systems and will likely facilitate the transition of the rAAV-8 vector system to the clinic.     

Dysprosium chloride as a nonabsorbable gastrointestinal marker for studies of stable isotope-labeled triglyceride excretion in man

OBJECTIVE: The aim of this work was to determine if dysprosium chloride (DyCl(3)) is a suitable nonabsorbable marker for studies of labeled-triglyceride excretion in cystic fibrosis patients allowing excretion to be determined accurately after analysis of one or two stools. METHODS: A series of 66 absorption studies were conducted in 36 young cystic fibrosis patients over a five year period. All tests consisted of ingesting a single test meal containing both (13)C-labeled triglyceride (TG*) and DyCl(3); in most studies the food colorant brilliant blue (FD&C blue #1) was administered along with the DyCl(3). Ingestion of the test meal was followed by collection of individual stools for 72 to 96 hours. Stools were analyzed for (13)C-Excess ((13)C*) and Dy. RESULTS: Excretion of Dy in cystic fibrosis patients who exhibited a wide-range of steatorrhea was quantitative. Fractional excretion of Dy and (13)C* in individual stools showed a high linear correlation (r(2) = 0.969) with a slope and y-intercept close to unity and zero, respectively. As a result, estimates of TG* excretion based on analysis of only two stools (partial pool method, PPM) were not different from those based on the analysis of all stools or stool composites. This was true both when Dy content and when stool color due to ingested brilliant blue was used to determine which stools to analyze for the PPM. CONCLUSIONS: Combining the use of Dy and brilliant blue permits reasonably accurate estimates of fecal TG* excretion after analysis of samples from two easily identified stools. This practical method can be used to address many important clinical and experimental questions regarding triglyceride digestion and absorption that may otherwise go unanswered.     

Effect of triglyceride structure on fecal excretion of 13C-labeled triglycerides

OBJECTIVE: The aim of this work was to determine the effects of specific changes in the structure of (13)C-labeled triglyceride (TG*) on its fecal excretion relative to total stool fat excretion determined simultaneously in patients with reduced exocrine pancreatic function. METHODS: A series of 47 studies were conducted in 26 young cystic fibrosis (CF) patients and 11 adult patients with chronic pancreatitis over a five year period. Each test consisted of ingesting a single high fat test meal containing both (13)C-labeled triglyceride (TG*) and dysprosium chloride (DyCl(3)) a nonabsorbable marker of intestinal transit; in most studies the food colorant brilliant blue (FD&C blue #1) was administered along with the DyCl(3). The TG*s tested were: P*P*P* = TRIPALMITIN-1,1,1-(13)C(3); SO*S = 2-OCTANOYL-1,3-DISTEARIN-2-octanoyl-1,2-(13)C(2); and P*LP* = 2-LAURYL-1,3-DIPALMITIN-dipalmitoyl-1,1,2,2-(13)C(4). Ingestion of the test meal was followed by collection of individual stools for at least 72 hours. Stools were analyzed for (13)C-Excess ((13)C*), total fat, and Dy. RESULTS: Excretion of P*LP* showed a high degree of linear correlation with stool fat (r(2) = 0.924) over a wide-range of fecal fat values. Excretion of SO*S was also significantly correlated with stool fat, but its excretion was less than 10% at all levels of steatorrhea and the slope of the regression line relating TG* excretion to stool fat was some four to five times smaller than observed for P*LP*. Fecal excretion of P*P*P* was highly correlated with stool fat (r(2) = 0.941) in patients with moderate steatorrhea (<25 g fat/24 hours) and the slope of the regression line (3.20) was considerably greater than for P*LP*. Only results from those studies in which stool collections were complete (Dy excretion >90%) were utilized in the statistical comparisons (36 of 47 studies). CONCLUSIONS: The observed highly significant linear correlation between P*LP* and stool fat over the entire range of steatorrhea suggests that P*LP* excretion may be a suitable surrogate for fecal fat in patients with reduced exocrine pancreatic function. Because fecal excretion of TG* administered as described can be accurately determined by sampling only two visually marked stools, development of a noninvasive test to replace the current 72-hour stool fat test using this approach is possible. Use of other engineered TG*s and/or labeled fatty acids, may provide a method for non-invasive in vivo assessment of the specific defect(s) leading to steatorrhea in other patient groups.     

A study of the photo-degradation kinetics of nifedipine by multivariate curve resolution analysis

A multivariate curve resolution method based on the combination of Kubista approach and iterative target transformation method of Gemperline has been proposed. This method is a soft model and need no information about the spectrum of the product and mechanism of the reaction. The method was used to study the degradation kinetics of nifedipin, 1,4-dihydro-2,6-dimethyl-4-(2-nitrophenyl)-3,5-pyridine dicarboxilic acid dimethyl ester, upon exposure to the light of a 40 W tungsten lamp. The spectra of the nifedipine, collected at different lighting times, were subjected to the factor analysis and two chemical components were detected in the reaction system. Pure spectra of the components involved and their concentration profiles were obtained. The results revealed that the photodecomposition kinetics of nifedipine is zero-order at the beginning of the reaction. However, when the reaction preceded more than 50%, the kinetics of reaction changed to a first-order manner. The rate constants for the zero-order and first order regions were estimated as regions (4.96+/-0.13) x 10(-9) M(-1) s(-1) and (6.22+/-0.10) x 10(-5) s(-1), respectively.