Magnetic tumor targeting of β-glucosidase immobilized iron oxide nanoparticles

Directed enzyme/prodrug therapy (DEPT) has promising application for cancer therapy. However, most current DEPT strategies face shortcomings such as the loss of enzyme activity during preparation, low delivery and transduction efficiency in vivo and difficultly of monitoring. In this study, a novel magnetic directed enzyme/prodrug therapy (MDEPT) was set up by conjugating beta-glucosidase (beta-Glu) to aminated, starch-coated, iron oxide magnetic iron oxide nanoparticles (MNPs), abbreviated as beta-Glu-MNP, using glutaraldehyde as the crosslinker. This beta-Glu-MNP was then characterized in detail by size distribution, zeta potential, FTIR spectra, TEM, SQUID and magnetophoretic mobility analysis. Compared to free enzyme, the conjugated beta-Glu on MNPs retained 85.54% +/- 6.9% relative activity and showed much better temperature stability. The animal study results showed that beta-Glu-MNP displays preferable pharmacokinetics characteristics in relation to MNPs. With an adscititious magnetic field on the surface of a tumor, a significant quantity of beta-Glu-MNP was selectively delivered into a subcutaneous tumor of a glioma-bearing mouse. Remarkably, the enzyme activity of the delivered beta-Glu in tumor lesions showed as high as 20.123 +/- 5.022 mU g(-1) tissue with 2.14 of tumor/non-tumor beta-Glu activity.