Highly efficient solid-phase derivatization of sugar phosphates with titanium-immobilized hydrophilic polydopamine-coated silica

• A solid-phase derivatization approach for sugar phosphates was newly proposed.
• The approach showed advantages of short derivatization time and high product purity.
• The sensitivity of the method was greatly improved by three orders of magnitude.
• The method was used to analyze the trace sugar phosphates in cell samples.

Sugar phosphates are a type of key metabolic intermediates of glycolysis, gluconeogenesis and pentose phosphate pathway, which can regulate tumor energetic metabolism. Due to their low endogenous concentrations, poor chromatographic retention properties as well as ionization suppression from complex matrix interference, the determination of sugar phosphates in biological samples is very difficult. In this study, titanium-immobilized hydrophilic polydopamine-coated silica microspheres (SiO2@PD-Ti4+) were synthesized for highly efficient solid-phase derivatization of sugar phosphates. Sugar phosphates were selectively captured onto the surface of the SiO2@PD-Ti4+ microspheres by chelating with phosphate groups, and then reacted with 3-amino-9-ethylcarbazole via reductive amination based on solid-phase derivatization, which could not only increase the retention and resolution of sugar phosphates on reversed-phase liquid chromatography (RPLC), but also improve the mass spectrometry (MS) sensitivity of sugar phosphates. The adsorption capacity of SiO2@PD-Ti4+ microspheres towards glucose-6-phosphate is 0.76 mg/g, which is much larger than that of commercial TiO2. Compared with the traditional liquid-phase derivatization, the solid-phase derivatization based on the SiO2@PD-Ti4+ microspheres displayed several superiorities including shorter derivatization time (within 10 min), higher product purity and much lower limit of detection (up to 38 pmol/L). In addition, good linearity (R2 ≥ 0.99), excellent recovery (80.6–118%) and high precision (RSDs with 2.8–7.8%) were obtained when the developed method was used for quantitative analysis of sugar phosphates. Finally, the SiO2@PD-Ti4+ microspheres combined with RPLC–MS were successfully applied to the determination of sugar phosphates from hepatocarcinoma cell lines and could even detect the trace sugar phosphates in thousands of cells.