Highly stabilized curcumin nanoparticles tested in an in vitro blood-brain barrier model and in Alzheimer's disease Tg2576 mice

Abstract

The therapeutic effects of curcumin in treating Alzheimer's disease (AD) depend on the ability to penetrate the blood-brain barrier. The latest nanoparticle technology can help to improve the bioavailability of curcumin, which is affected by the final particle size and stability. We developed a stable curcumin nanoparticle formulation to test in vitro and in AD model Tg2576 mice. Flash nanoprecipitation of curcumin, polyethylene glycol-polylactic acid co-block polymer, and polyvinylpyrrolidone in a multi-inlet vortex mixer, followed by freeze drying with β-cyclodextrin, produced dry nanocurcumin with mean particle size <80 nm. Nanocurcumin powder, unformulated curcumin, or placebo was orally administered to Tg2576 mice for 3 months. Before and after treatment, memory was measured by radial arm maze and contextual fear conditioning tests. Nanocurcumin produced significantly (p=0.04) better cue memory in the contextual fear conditioning test than placebo and tendencies toward better working memory in the radial arm maze test than ordinary curcumin (p=0.14) or placebo (p=0.12). Amyloid plaque density, pharmacokinetics, and Madin-Darby canine kidney cell monolayer penetration were measured to further understand in vivo and in vitro mechanisms. Nanocurcumin produced significantly higher curcumin concentration in plasma and six times higher area under the curve and mean residence time in brain than ordinary curcumin. The P(app) of curcumin and tetrahydrocurcumin were 1.8×10(-6) and 1.6×10(-5)cm/s, respectively, for nanocurcumin. Our novel nanocurcumin formulation produced highly stabilized nanoparticles with positive treatment effects in Tg2576 mice.

Fig. 1

Particle size distribution, measured by dynamic light scattering (DLS), of nanocurcumin (NC) at different stages of formulation: blue NC suspension, red NC suspension after dialysis for 24 h, green NC suspension after reconstitution from powder form, purple NC suspension after reconstitution from powder form stored for 1 year

Fig. 2

SEM images of dried NC powder. The measured diameters were approximately 50–56 nm

Fig. 3

In vitro cell monolayer penetration test of NC, CD (curcumin mixed with hydroxypropyl beta cyclodextrin), and CUR (unformulated curcumin): a curcumin concentration in receiver compartment versus time, b THC concentration in receiver compartment versus time. Each time point represents mean ± SD (n = 2)

Fig. 4

Contextual fear conditioning test comparisons (repeated measures ANOVA): a cue memory between NC and control treatment (###p = 0.04); b contextual memory before vs. after treatment (p > 0.05) and among treatments (p > 0.05)

Fig. 5

Curcumin and THC concentration versus time after single oral dose (23 mg/kg body weight) of NC or CUR. Each datapoint represents mean ± SD (n = 4). The AUC of curcumin in a plasma and in b brain was significantly higher after NC than CUR. c THC in plasma peaked earlier with NC than with CUR. d THC in brain was similar for NC and CUR until 80 min, after which THC rose more for CUR than for NC

Fig. 6

Mean area of amyloid plaques in brain for different treatments (log scale). **Among treatments, only CUR and control mice differed (one-way ANOVA, p = 0.046)