Saeed Sattari

Block copolymer micelles for the encapsulation and delivery of amphotericin B

AbstractPurpose. To assess the effect of fatty acid substitution of a micelle-forming poly(ethylene oxide)-block-poly(N-hexyl stearate-L-aspartamide) (PEO-b-PHSA) on the encapsulation, hemolytic properties and antifungal activity of amphotericin B (AmB). Methods. PEO-b-PHSA with three levels of stearic acid substitution were synthesized and used to encapsulate AmB by a solvent evaporation method. Size exclusion chromatography and UV spectroscopy were used to confirm and measure levels of encapsulated AmB. The hemolytic activity of encapsulated AmB toward human red blood cells and its minimum inhibitory concentration against Candida albicans, Aspergillus fumigatus and Cryptococcus neoformans were obtained and compared to AmB alone. Results. An increase in the level of stearic acid substitution on PEO-b-PHSA improved the encapsulation of AmB while reducing its hemolytic activity. PEO-b-PHSA micelles having 50% and 70% stearic acid substitution (mol fatty acid: mol reacted and unreacted hydroxyls) were completely non-hemolytic at 22 μg/ml. At 11% stearic acid substitution, AmB caused 50% hemolysis at 1 μg/ml. AmB in PEO-b-PHSA micelles was as effective as AmB alone against pathogenic fungi. Conclusions. PEO-b-PHSA micelles with a high level of stearic acid side chain substitution can effectively solubilize AmB, reduce its hemolytic activity yet retain its potent antifungal effects.

Synthesis and in vitro antifungal and cytotoxicity evaluation of thiazolo-4H-1,2,4-triazoles and 1,2,3-thiadiazolo-4H-1,2,4-triazoles.

The increasing clinical importance of drug‐resistant fungal pathogens has lent additional urgency to microbiological and antifungal research. Various thiazolo(or 1,2,3‐thiadiazolo)thiosemicarbazides (2a—2e), 3‐thiono‐1,4‐dihydrotriazolothiazoles‐(or 1,2,3‐thiadiazoles) (3a—3e), their related substituted thio‐4H‐1,2,4‐triazoles (4a—4p) and sulfones (5a—5o) were synthesized. Most of the compounds tested for antifungal activity exhibited significant effects against Cryptococcus neoofrmans and Sacchromyces cerevisiae at MIC ranges of 0.53 to 12.5μg/mL, whereas their activities were moderate against Candida albicans and weak against Aspergillus fumigatus. At 10 ppm concentration, all compounds showed low toxicity on brine shrimps (higher than 80% survival), except compounds 4c and 2c. At 100 ppm concentration most of the compounds showed toxicity except compounds 2b, 2e, 3c, 3d, 3e, and 4e. Compounds 4b, 4c, and 4h showed in vitro cytotoxicity against Kbalb cell lines and compounds 4c and 4g against 143B cell lines at 0.1 mM concentration.

Drug-disease interactions : reduced β-adrenergic and potassium channel antagonist activities of sotalol in the presence of acute and chronic inflammatory conditions in the rat

Inflammation may influence response to pharmacotherapy. We investigated the effect of inflammation on response to sotalol, a β‐adrenergic receptor and potassium channel antagonist. Racemic sotalol (40 mg kg−1) was administered to healthy, acutely (interferonα 2a‐induced) and chronically (Mycobacterium butyricum‐induced adjuvant arthritis) inflamed male Sprague‐Dawley rats (n=4 – 6/group). Another group of interferon‐treated rats received 3 mg kg−1 of anti‐TNF antibody infliximab. Electrocardiogram (ECG) recorded and plasma sotalol concentration monitored for 6 h. The study was repeated in acutely inflamed rats following administration of stereochemically pure individual sotalol enantiomers [40 mg kg−1 S (potassium channel blocker) or 20 mg kg−1 R (β‐adrenergic/potassium channel blocker)]. Chronic arthritis was readily evident. Acute arthritis was associated with elevated segmented neutrophils and increased plasma nitrite and tumour necrosis factor (TNF) concentrations. Sotalol affected ECG in all rats. In both inflamed groups, however, response to sotalol in prolongation of QT interval (potassium channel sensitivity) was reduced. The effect of PR interval (β‐adrenergic activity) was also reduced following administration of the racemate and R‐enantiomer. No significant differences in pharmacokinetics were observed between control and inflamed rats. Infliximab reduced nitrite and TNF concentrations and reversed the effect of acute inflammation on both PR and QT intervals. The reduced electrocardiographic responses to sotalol is likely due to the influence of inflammation on the action of the drug on both β‐adrenergic and potassium channel receptors secondary to over‐expression of pro‐inflammatory cytokines and/or nitric oxide. Our observation may have therapeutic consequences in all conditions where inflammatory mediators are increased.

Synthesis and in vitro antifungal and cytotoxicity evaluation of substituted 4,5-dihydronaphtho[1,2-d][1,2,3]thia(or selena)diazoles

Unsubstituted 4,5-dihydronaphtho[1,2-d][1,2,3]thia (or selena)diazoles (2a, 2b), prepared from the semicarbazone (1a), were nitrated using fuming nitric acid at 0 degrees C to yield various mono-nitrated dihydronaphthalenes (3a-3e). Related sulfamoyl derivatives (4a, 4b) were prepared using chlorosulfonic acid, followed by the addition of ammonia solution. Synthesis of 6,9-dimethoxy-4,5-dihydronaphtho[1,2-d][1,2,3]thiadiazole derivative (2c) was performed using 5,8-dimethoxy-alpha-tetralone semicarbazone (1b) and thionylchloride at low temperature. At 10 ppm concentration, all compounds showed low toxicity (higher than 80% survival) on brine shrimps, while at 100 ppm concentration compounds 2d, 3d, and 4b exhibited toxicity (less than 60% survival). Compounds 3a, 3e, and especially 4a showed significant antifungal activity against Cryptococcus neoformans. Compound 4a, while being the most active antifungal agent in this series, possessed low toxicity.

Improved high-performance liquid chromatographic assay method for the enantiomers of ibuprofen

A rapid, inexpensive and sensitive high-performance liquid chromatographic method for the quantitation of ibuprofen enantiomers from a variety of biological fluids is reported. This method uses a commercially available internal standard and has significantly less interference from endogenous co-extracted solutes than do previously reported methods. The method involves the acid extraction of drug and internal standard [(+/-)-fenoprofen] from the biological fluid with isooctane-isopropanol (95:5) followed by evaporation and derivatization with ethylchloroformate and R-(+)-alpha-phenylethylamine. Excellent linearity was observed between the peak-area ratio and enantiomer concentration (r > 0.99) over a concentration range of 0.25-50 micrograms/ml. This method is suitable for the quantitation of ibuprofen from single-dose pharmacokinetic studies involving either rats or humans.

Despite increased plasma concentration, inflammation reduces potency of calcium channel antagonists due to lower binding to the rat heart.

Rheumatoid arthritis reduces verapamil oral clearance thereby increases plasma concentration of the drug. This coincides with reduced drug effects through an unknown mechanism. The effect of interferon‐induced acute inflammation on the pharmacokinetics and electrocardiogram of verapamil (20 mg kg−1, p.o.) and nifedipine (0.1 mg kg−1, i.v.) was studied in Sprague–Dawley rats. The effect of both acute and chronic inflammation on radioligand binding to cardiac L‐type calcium channels was also investigated. Acute inflammation resulted in increased plasma concentration of verapamil but had no effect on that of nifedipine. Verapamil binding to plasma proteins was unaffected. As has been reported for humans, the increased verapamil concentration coincided with a reduction in the degree to which PR interval is prolonged by the drug. The effect of nifedipine on PR interval was also reduced by inflammation. Maximum binding of 3H‐nitrendipine to cardiac cell membrane was significantly reduced from 63.2±2.5 fmol mg−1 protein in controls to 46.4±2.0 in acute inflammation and from 66.8±2.2 fmol mg−1 protein in controls to 42.2±2.0 in chronic inflammation. Incubation of the normal cardiac cell membranes with 100 and 1000 pg ml−1 of rat tissue necrosis factor‐α did not influence the binding indices to the calcium channels. Our data suggest that the reduced calcium channel responsiveness is because of altered binding to channels.

The effect of inflammation on ligand binding and density of L‐type calcium and erg K‐channels in rat myocardium

The purpose of this study was to investigate the effect of inflammation on ligand binding and density of L‐type calcium channels (LCC) and erg potassium channels (EKC) in the rat heart. Acute and chronic inflammation were induced, hearts were removed and either their myocytes were isolated or they were homogenized to provide cardiac cell membranes. Equilibrium ligand binding of 3H‐nitrendipine (NIT) to LCC and 3H‐dofetilide (DOF) to EKC was performed. Direct effect of TNF on ligand binding was examined using normal rat cardiac membranes. Western blotting of LCC was performed to estimate the density of the target protein. The results indicate that inflammation had no significant effects on dissociation constants (KD). However, the maximum binding (Bmax) for NIT was significantly reduced in chronic (38.7 ± 6.8%) and acute (26.1 ± 8.1%) inflammation. Binding of DOF to EKC in isolated myocytes was not affected by inflammation. The presence of TNF did not affect the binding parameters of NIT to LCC. Western blotting revealed that inflammation had no effect on the density of α1C subunit of LCC. In summary, decrease in efficacy of cardiovascular drug seen in inflamed states could be mainly due to reduced binding to their ligands. Reduced binding may explain, in part, the reduced pharmacological response to calcium channel blockers such as verapamil, in spite of higher plasma concentrations, in the presence of inflammatory diseases such as rheumatoid arthritis. Supported by CIHR.