Activity and stability of alkaline phosphatase (ALP) immobilized onto magnetic nanoparticles (Fe3O4)

Direct binding of alkaline phosphatase (ALP) on magnetic nanoparticles (Fe3O4) in the presence of carbodiimide (CDI) using two different methods is described. The activity and stability of immobilized ALP with both shaking and sonication method were compared. The results indicated the ALP binding efficiency to be in the range of 80-100% with both the immobilization techniques. The activities retained were in the range of 20-38% with shaking method and 30-43% with sonication method, respectively. The activities of the immobilized ALP preparations were found to be stable compared to the free (unbound) ALP for at least 16-week storage period. Moreover, ALP immobilized on magnetic nanoparticles was successfully used for dephosphorylation of plasmid DNA before it was used for ligation reaction. The use of immobilized ALP for plasmid dephosphorylation allows easy manipulation, reduces the procedural time, and also avoids exposure of reaction mixture to high temperature. (C) 2007 Elsevier B.V. All rights reserved.