Adsorption of taxol into ordered mesoporous silicas with various pore diameters

Taxol, an anticancer substance, was adsorbed into FSM-type mesoporous silicas with the pore sizes larger than 1.8 nm, while it was not adsorbed into the channels with the pore size less than 1.6 nm, indicating that mesoporous silicas have a molecular sieving property for relatively large molecules. The adsorption behavior of Taxol depended on the solvents; Taxol was not adsorbed into mesoporous silicas when methanol or acetone was used but was adsorbed when dichloromethane or toluene was used. The adsorption behavior of Taxol is discussed on the basis of the solubility parameters of the solvents. The proton-acceptor solubility parameter (δa) is a predominant factor in this liquid-solid partition system. The adsorption-desorption of an extract from yew needles was performed using the mesoporous silica and several elution solvents. In the adsorption, many components including Taxol were adsorbed into mesoporous silica. When the desorption of the extract components adsorbed into the mesoporous silica was performed with a mixture of methanol and water with varied ratios, the targeted molecule, Taxol, with a few addition of components was separated from the adsorbed components. This adsorption-desorption behavior was elucidated by the solubility parameter (δ) as well as δa.