Enzymatic Synthesis of Selenium-Doped Manganese Phosphate Nanoparticles

The nanoparticles of Se-MnP were synthesized by an enzymatic reaction, using an organic phosphorylated molecules of Fructose disodium diphosphate (C₆H₁₂Na₂O₁₂P₂, Na₂FDP) (Sigma-Aldrich Co., US) to instead traditional phosphate salts. In a typical process in synthesis of Se-MnP, 0.66 g of Na₂FDP was dissolved in 40 mL of deionized water, 0.02 g of Na₂SeO₃ (Sigma-Aldrich Co., US) was dissolved in 40 mL of deionized water, separately. Then, the above solutions were mixed and stirred for 5 min at 37 °C within a water bath. Thereafter, 1 mL of ALP aqueous solution (20 U/mL) was added to the mixed solution and magnetically stirred. Then, 0.19 g of MnCl₂·4H₂O (Aladdin Biochemical Technology Co., China) dissolved in 20 mL of water was dropwise added into the above solution. During the whole reaction process, the pH value of the reaction solution was kept between 8.0 and 8.5 by continually adding a dilute NaOH aqueous solution (0.5 M). Finally, the as-prepared samples were collected by centrifugation and washed with ethanol twice, deionized water twice, and freeze-dried into powders for further use. The MnP without Se element was used as a control sample. The synthesis procedure of the MnP sample is as follows: 0.66 g of Na₂FDP was dissolved in 80 mL of deionized water and then mixed with 1 mL of ALP (20 U/mL) aqueous solution. The rest of process is same to the preparation of Se-MnP sample.