Thermostable iron oxide nanoparticle synthesis within recombinant ferritins from the hyperthermophile Pyrococcus...

Thermostable nanoparticles have numerous applications in catalysis and in the oil/gas industry. However, synthesizing these nanoparticles requires expensive polymers. Here, a novel thermostable ferritin named PcFn, originally from the hyperthermophilic archaeon Pyrococcus yayanosii CH1, was overexpressed in Escherichia coli, purified and characterized, which could successfully direct the synthesis of thermostable magnetoferritins (M-PcFn) with monodispersed iron oxide nanoparticles in one step. Transmission electron microscopy and magnetic measurements show that the cores of the M-PcFn have an average diameter of 4.7 nm, are well-crystalline and superparamagnetic. Both the PcFn and M-PcFn can resist temperatures up to 110 °C, which is significantly higher than for human H-chain ferritin (HFn) and M-HFn, and comparable to temperatures previously reported for Pyrococcus furiosus ferritin (PfFn) and M-PfFn. After heating at 110 °C for 30 minutes, PcFn and M-PcFn maintained their secondary structures and PcFn retained 87.4% of its iron uptake activity. This remarkable thermostability of PcFn and M-PcFn suggests potential applications in elevated temperature environments.