Development and evaluation of polymer nanoparticles for oral delivery of estradiol to rat brain in a model of Alzheimer's pathology

The purpose of this study was to develop tween 80 (T-80) coated polylactide-co-glycolide (PLGA) nanoparticles that can deliver estradiol to the brain upon oral administration. Estradiol containing nanoparticles were made by a single emulsion technique and T-80 coating was achieved by incubating the re-constituted nanoparticles at different concentrations of T-80. The process of T-80 coating on the nanoparticles was optimized and the pharmacokinetics of estradiol nanoparticles was studied as a function of T-80 coating. The nanoparticles were then evaluated in an ovariectomized (OVX) rat model of Alzheimer's disease (AD) that mimics the postmenopausal conditions. The nanoparticles bound T-80 were found to proportionally increase from 9.72 +/- 1.07 mg to 63.84 +/- 3.59 mg with an increase in the initial concentration T-80 from 1% to 5% and were stable in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF). Orally administered T-80 coated nanoparticles resulted in significantly higher brain estradiol levels after 24 h (1.969 +/- 0.197 ng/g tissue) as compared to uncoated ones (1.105 +/- 0.136 ng/g tissue) at a dose of 0.2 mg/rat suggesting a significant role of surface coating. Moreover, these brain estradiol levels were almost similar to those obtained after administration of the same dose of drug suspension via 100% bioavailable intramuscular route (2.123 +/- 0.370 ng/g tissue), indicating the increased fraction of bioavailable drug reaching the brain when administered orally. Also, the nanoparticle treated group was successful in preventing the expression of amyloid beta-42 (A beta 42) immunoreactivity in the hippocampus region of brain. Together, the results indicate the potential of nanoparticles for oral delivery of estradiol to brain. (C) 2010 Elsevier B.V. All rights reserved.