Magnetic fluid hyperthermia (MFH) promises to be a viable alternative in the treatment of localized cancerous tumors.The treatment consists of introducing nanoparticles as energy absorbent agents in tumor tissue under an oscillating magnetic field,where nanoparticles dissipate energy in the form of heat,causing a localized rise in the temperature and tumor cell death.Traditional magnetic fluid under study is artificial magnetic nanoparticles.This work seeks to introduce the new natural biologic magnetic material bacterial magnetosomes (BMs) to be used in MFH.Properties of magnetosomes and chemically synthesized magnetic nanoparticles (MNPs),such as morphology,magnetic properties and their heating effects under magnetic field were compared.Cytotoxicity studies using human breast cancer cells MCF-7 indicated that cell viability could be significantly decreased by the heat derived from BMs and MNPs under alternative magnetic field.Biocompatibility of BMs and MNPs was compared in terms of evaluating their acute toxicity in mice and their decomposition abilities in vitro,and it showed that magnetosomes exhibit a lower toxicity.These findings provide evidence for beneficial activities of magnetosomes in MFH and support the continued investigation of it to be applied in biomedicine.