Investigation on the uptake and release ability of beta -cyclodextrin functionalized Fe sub(3)O sub(4) magnetic nanoparticles by methylene blue

beta -cyclodextrin functionalized magnetic nanoparticles ( beta -CD-MNPs) having a core-shell structure were fabricated with a layer-by-layer method by combining 3-aminopropyl triethoxysilane coated magnetic Fe sub(3)O sub(4) nanoparticles (AP-MNPs) with 6-O-toluenesulfonyl- beta -cyclodextrin (6-TsO- beta -CD) at 70 degree C. The characterization by transmission electron microscopy revealed beta -CD-MNPs having an average diameter of 12 plus or minus 2 nm and an average hydrodynamic diameter of 56.8 nm in aqueous solution by dynamic light scattering. The beta -CD grafting was confirmed by Fourier-Transformed Infrared spectroscopy, and the amount of beta -CD grafted on MNPs was determined as 60 mg/g by thermogravimetric analysis. The uptake and release ability of beta -CD-MNPs was investigated using methylene blue (MB) as a biological staining dye by spectrophotometric method. The results showed that the uptake and release were greatly influenced by the pH value of dye solution, with a maximum loading capacity of 78.4 mg/g under pH = 8 at 25 degree C, and the release was easily achieved at 73% within the first hour at physiological condition. The adsorption isotherms were examined by Langmuir and Freundlich models, and the satisfactory fitting to the Langmuir model suggested the adsorption on beta -CD-MNPs as a mono-layer coverage.