A facile one-pot method for synthesizing aminefunctionalized nonspherical Fe3O4 nanoparticles in gram-scale quantities is presented using just a single source of iron (iron(II) chloride) and an amine (triethylamine). The amine not only transforms iron salt to Fe3O4, but also directs the morphology of the nanoparticles along with the temperature of the reaction and functionalizes them, making the synthesis very economical. By modifying the surface further, these nanoparticles promise to offer useful biomedical applications. For example, after biocide coating, the particles are found to be 100% effective in deactivating methicillin-resistant Staphylococcus aureus (MRSA) bacteria in 2 h. Cellular-uptake studies using biocompatible EDTA-Na-3 (N-(trimethoxysilyl-propyl)ethylenediaminetriacetate, trisodium salt) coated nanoparticles in human glioblastoma U-251 cells show that the majority of the particles are internalized by the cells in the presence of a small dc-magnetic field, making these particles potential candidate as drug carriers for magnetic field-targeted delivery and hyperthermia.