Development of Gold Coated Superparamagnetic Iron Oxide Nanoparticles for Nitroreductase Delivery

Directed enzyme prodrug therapies (DEPT) currently suffer from inherent problems associated with localising and retaining enzymes at tumours. Superparamagnetic iron oxide nanoparticles (SPION) have been synthesised (≈10 nm) and surface functionalised with gold by direct reduction and by attachment of pre-synthesised Au seeds; these Au-SPION sols are stable in aqueous solution and are susceptible to magnetic manipulation. We have genetically modified the nitroreductase (NTR) yfkO from Bacillus Licheniformis to include a sequence of 12 cysteine residues, this modified NTR retains activity with CB1954 and has been immobilised onto gold via the 12 Au-S bonds. The yfkO-cys12 can therefore be immobilised with controlled orientation onto the Au-SPION to allow a magnetically directed enzyme prodrug therapy (MDEPT) to be developed; creating a novel strategy to target and localise prodrug activation to cancer tumour sites using magnetism.