(2-Hydroxypropyl)-β-cyclodextrin (HP-β-CD)

HP-β-CD molecules were not only nontoxic to cells, but also greatly inhibited Aβ fibrillization and reduced Aβ-induced toxicity in a concentration-dependent manner. Too low concentrations of HP-β-CD caused insufficient interactions with Aβ, while too high concentrations of HP-β-CD caused HP-β-CD to self-aggregate into inactive species. HP-β-CD interacted preferentially with some of the hydrophobic residues of Aβ, which prevented Aβ oligomers from further growing into mature fibrils via peptide elongation and lateral association^[1].

Cells that was cultured at 37 ℃ in the mixture of sterile-filtered Eagle's minimum essential medium and Ham's F-12 medium mixed at a 1 : 1 ratio with 10% fetal bovine serum, 1% penicillin/streptomycin and humidified air with 5% CO2 was employed as a model neuron. Cells were cultured to confluence and harvested using 0.25 mg/mL trypsin/EDTA solution. Before adding Aβ1-42 and HP-β-CD, cells were resuspended in Opti-MEM reduced serum medium and counted using a hemocytometer. Cells were then plated in a 96-well tissue culture plate with approximately 100 000 cells per well in 200 μL medium. To determine the cell viability, colorimetric MTT metabolic activity assay was performed. SH-SY5Y cells were cultured in a 96-well plate at 37 1C. Then, Aβ1-42, HP-β-CD and Aβ1-42-HP-β-CD solutions were individually added to the cultured cells, which were then continually cultured for additional 24 h and 48 h. After removing the supernatant of each well, 20 μL of MTT solution (5 mg/mL in PBS) and 100 mL of medium were then added into the systems. After incubation for another 4 h, the formazan crystals were dissolved in dimethyl sulfoxide (150 μL) and the absorbance intensity was measured using a microplate reader at 570 nm.

HP-β-CD, due to its excellent biocompatibility, has been widely used in drug delivery systems, environmental remediation, food additives, and pharmacotherapy. HP-β-CD can readily cross the BBB and target nerve cells^[1]. HP-β-CD is well tolerated in the animal species tested (rats, mice and dogs), particularly when dosed orally, and shows only limited toxicity. After a single 200 mg/kg intravenous dose in rats and dogs, 14C-HP-β-CD was eliminated rapidly (more than 90% in 4 h), almost completely as the intact compound and mostly by renal excretion. The excretion in faeces and expired air was minimal. The plasma elimination half-life was 0.4 h in rats and 0.8 h in dogs. After oral administration of HP-β-CD in both rats and dogs, 86% was excreted via the faeces in both species, where as less than 5% was excreted in the urine. The absolute bioavailability was estimated at 3.3% in the dog and less in the rat. In both rats and dogs following intravenous administration, tissue distribution was limited: in rats the highest concentration was found in the kidney and lung and in dogs, the highest concentrations were in the kidney and the liver. Plasma levels of unchanged HP-β-CD declined rapidly and showed a bi-phasic decline after single intravenous and oral dosing in healthy volunteers. The utility of a 45%w/v HP-β-CD aqueous dosing vehicle in preclinical studies is very common. This vehicle is useful with poorly aqueous drugs^[2].