Nucleoside Isolation Performance of Ti⁴⁺/Zr⁴⁺ Immobilized Polydopamine Coated, Monodisperse-Porous Titania Microbeads

Abstract

A Ti⁴⁺/Zr⁴⁺ ion immobilized sorbent was developed by starting from monodisperse-porous titania microbeads, for the isolation of nucleosides via immobilized metal affinity chromatography (IMAC). For the synthesis of IMAC sorbent, the monodisperse-porous titania microbeads were coated with a polydopamine (PDA) layer. PDA coated titania microbeads were then interacted with TiCl₄ or ZrOCl₂ solution for the immobilization of Ti⁴⁺ or Zr⁴⁺ ions onto the PDA layer. Five nucleosides (adenosine, uridine, cytidine, thymidine and guanosine) were individually adsorbed onto Ti⁴⁺ or Zr⁴⁺ immobilized titania microbeads in aqueous buffer in a pH range of 4–9. The desorption of nucleosides was performed in an aqueous formic acid solution. The nucleoside isolation performance of Ti⁴⁺ immobilized sorbent was also compared with Zr⁴⁺ immobilized sorbent, PDA coated titania and bare titania microbeads. The highest equilibrium adsorptions and the highest desorption yields were obtained with Ti⁴⁺ immobilized sorbent for all nucleosides. It was demonstrated that pH 7 was found as the most appropriate for the adsorption of all nucleosides onto Ti⁴⁺ immobilized sorbent, which was also close to the physiological pH of urine. The highest equilibrium adsorption was observed with adenosine as 12.67 mg adenosine/g Ti⁴⁺ immobilized sorbent. Almost quantitative desorption yields were achieved with all nucleosides adsorbed in a wide range of pH onto Ti⁴⁺ immobilized sorbent. With respect to the similar sorbents developed previously, we believe that the proposed sorbent is a promising candidate for being a stationary phase particularly for the construction of micro-column based IMAC systems used in the continuous isolation of nucleosides.