D-amino acid oxidase-nanoparticle system: a potential novel approach for cancer enzymatic therapy

Aim: The authors propose a new magnetic nanoparticle-enzyme system for cancer therapy capable of targeting the enzyme and consequently decreasing the adverse effects, meanwhile improving the patient's life quality. Materials & methods: The authors have functionalized Fe3O4 nanoparticles with 3-amino-propyltriethoxysilane (APTES) and conjugated it to yeast D-amino acid oxidase (DAAO) by coupling this with glutaraldehyde. Results & conclusion: The authors have tested the Fe3O4-APTES-DAAO system on three tumor cell lines. Exposed cells show, at the electron microscope level, nanoparticles on the surface of the plasma membrane and inside endocytic vesicles. Fe3O4-APTES-DAAO caused a substantial decrease of cell viability greatly augmented when D-alanine, a DAAO substrate, was added. Fe3O4-APTES-DAAO was demonstrated to be more effective than free DAAO, confirming the validity of the system in cancer therapy. Original submitted 27 March 2012; Revised submitted 20 September 2012; Published online 5 February 2013