Glutaraldehyde-crosslinked chitosan-polyethylene oxide nanofibers as a potential gastroretentive delivery system of nizatidine for augmented gastroprotective activity.

Nizatidine (NIZ), a histamine H2-receptor antagonist, is soluble and stable in the stomach, however, it exhibits a short half-life and a rapid clearance. Therefore, chitosan (CS) and polyethylene oxide (PEO) nanofibers (NFs) at different weight ratios were prepared by electrospinning and characterized. The selected uncrosslinked and glutaraldehyde-crosslinked NFs were investigated regarding floating, solid-state characteristics, in vitro release, and in vitro cytotoxicity. The cytoprotective activity against ethanol-induced gastric injury in rats was evaluated through macroscopical, histopathological, immunohistochemical, and oxidative stress examinations. NFs based on 8:2 CS:PEO exhibited the smallest diameter (119.17 ± 22.05 nm) and the greatest mucoadhesion (22.82 ± 3.21 g/cm2), so they were crosslinked with glutaraldehyde. Solid-state characterization indicated polymers interaction, a successful crosslinking, and NIZ dispersion in NFs. Crosslinking maintained swollen mats at pH 1.2 (swelling% = 29.47 ± 3.50% at 24 h), retarded their erosion at pH 6.8 (swelling%= 84.64 ± 4.91% vs. 25.40 ± 0.79% for the uncrosslinked NFs at 24 h), augmented the floating up to 24 h vs. 10 min for the uncrosslinked NFs at pH 1.2 and prolonged the drug release (%drug released ≥ 93% at 24 h vs. 4 and 5 h for the uncrosslinked NFs at pHs 1.2 and 6.8, respectively). The viability of Caco-2 cells ≥ 86.87 ± 6.86% revealed NFs biocompatibility and unreacted glutaraldehyde removal. Crosslinking of 8:2 CS:PEO NFs potentiated the antiulcer activity (38.98 vs. 8.67 for the uncrosslinked NFs) as well as it preserved the gastric wall architecture, COX-2 expression, and oxidative stress markers levels of the normal rats.

In vitro-in vivo evaluation of chitosan-PLGA nanoparticles for potentiated gastric retention and anti-ulcer activity of diosmin.

BACKGROUND: Diosmin showed poor water solubility and low bioavailability. Poly(d,l-lactide-co-glycolide) (PLGA) nanoparticles were successfully used to improve the drugs solubility and bioavailability. Coating of PLGA nanoparticles with chitosan can ameliorate their gastric retention and cellular uptake. METHODOLOGY: PLGA nanoparticles of diosmin were prepared using different drug and polymer amounts. Nanoparticles were selected based on entrapment efficiency% (EE%) and particle size measurements to be coated with chitosan. The selected nanoparticles either uncoated or coated were evaluated regarding morphology, ζ-potential, solid-state characterization, in vitro release, storage stability, and mucoadhesion. The anti-ulcer activity (AA) against ethanol-induced ulcer in rats was assessed through macroscopical evaluation, histopathological examination, immunohistochemical localization of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and transmission electron microscopic examination of gastric tissues compared to free diosmin (100 mg/kg) and positive control. RESULTS: Based on EE% and particle size measurements, the selected nanoparticles, either uncoated or coated with 0.1% w/v chitosan, were based on 1:15 drug-PLGA weight ratio and 20 mg diosmin employing methylene chloride as an organic phase. Examination by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed nanoscopic spherical particles. Drug encapsulation within the selected nanoparticles was suggested by Fourier transform-infrared, differential scanning calorimetry (DSC) and X-ray diffractometry results. Chitosan-coated nanoparticles were more stable against size enlargement probably due to the higher ζ-potential. Only coated nanoparticles showed gastric retention as revealed by SEM examination of stomach and duodenum. The superior AA of coated nanoparticles was confirmed by significant reduction in average mucosal damage, the majority of histopathological changes and NF-κB expression in gastric tissue when compared to positive control, diosmin and uncoated nanoparticles as well as insignificant difference relative to normal control. Coated nanoparticles preserved the normal ultrastructure of the gastric mucosa as revealed by TEM examination. CONCLUSION: The optimized chitosan-coated PLGA nanoparticles can be represented as a potential oral drug delivery system of diosmin.

Enhanced ocular bioavailability of fluconazole from niosomal gels and microemulsions: formulation, optimization, and in vitro-in vivo evaluation.

Fungal keratitis may cause vision loss if it is not treated. Methods other than ocular delivery exhibited several limitations. No previous studies investigated and compared ocular bioavailability of fluconazole (FLZ) from niosomal gels and microemulsions. Niosomal gels of FLZ (0.3% w/w) based on Span® 60 and cholesterol (CH) using 1% w/w carbopol® 934 (CP) were evaluated. FLZ microemulsions (0.3% w/v) containing isopropyl myristate (IPM, as oil phase) and a 3:1 mixture of Tween® 80 (as surfactant) and polyethylene glycol 400 (PEG 400, as cosurfactant) were characterized. Optimized formulations were compared for their ocular bioavailability in rabbit's. Nanoscopic niosomes (63.67-117.13 nm) and microemulsions (57.05-59.93 nm) showed respective negative zeta potential ranges of -45.37 to -61.40 and -20.50 to -31.90 mV and sustained release up to 12 h. Entrapment efficiency (EE%) of niosomes ranged from 56.48% to 70.67%. Niosomal gels were more sustainable than niosomes and microemulsions. The most stable niosomal gel based on Span® 60 and CH at a molar ratio of 5:5 and microemulsion containing 45% w/w IPM and 40% w/w of 3:1 Tween® 80-PEG 400 mixture significantly (p < 0.0001) enhanced FLZ ocular bioavailability compared with its solution. Niosomal gel showed higher bioavailability than microemulsion by ≈2-fold.

Potential Use of Cyclodextrin Complexes for Enhanced Stability, Anti-inflammatory Efficacy, and Ocular Bioavailability of Loteprednol Etabonate.

Loteprednol etabonate (LE) is a soft corticosteroid that maintains therapeutic activity with much reduced adverse effects. Yet, its ocular bioavailability is hindered by its poor aqueous solubility. Early attempts of LE complexation with cyclodextrins (CDs) did not involve the study of the effects of various complexation methods on the characteristics of the complexes formed. Formulation of complexes into different delivery systems as well in vitro and in vivo assessments has not been accomplished in the earlier studies. In this study, complexation of LE with each of hydroxypropyl-ß-cyclodextrin (HP-ß-CD) and ß-cyclodextrin (ß-CD) by kneading, freeze drying, and co-precipitation was attempted. These complexes were incorporated into gels, drops, and ocuserts using hydroxypropyl methylcellulose (HPMC), methylcellulose (MC), and sodium alginate (ALG). These formulae were examined with respect to drug content, pH, viscosity, in vitro release, and stability for 6 months. Kinetic analysis of release data was done. Selected formulations were assessed for their efficacy in the treatment of ocular allergic conjunctivitis and their ocular bioavailability in rabbits' eyes. All formulations exhibited accepted drug content, pH, and viscosity. The drug release was increased by complexation particularly with HP-ß-CD in the order of ocuserts ≥ drops > gels, being the highest for HPMC preparations that also exhibited the greatest stability and anti-inflammatory activity especially in case of LE-HP-ß-CD complexes. Ocuserts of co-precipitated LE-HP-ß-CD using HPMC (5% w/w) and Carbopol 934P (0.1% w/w) provided a significantly enhanced stability (p < 0.05), ocular anti-inflammatory efficacy (p < 0.05), and ocular bioavailability (p < 0.0001), to be represented as a potential ocular delivery system of LE.