Beschreibung:
<jats:title>Abstract</jats:title><jats:p>Colloidal ferrite spinel nanoparticles (Co<jats:italic><jats:sub>x</jats:sub></jats:italic>Ni<jats:sub>1–<jats:italic>x</jats:italic></jats:sub>Fe<jats:sub>2</jats:sub>O<jats:sub>4</jats:sub>) were prepared by a microwave‐stimulated Bradley technique under nonhydrolytic conditions. The effect of Ni<jats:sup>2+</jats:sup> doping on the structural properties was studied by powder XRD. The particle size, hydrodynamic size, and morphology were evaluated by transmission electron microscopy (TEM) and dynamic light scattering (DLS), which showed mean crystallite sizes of ca. 10 and 60 nm for powder and colloidal suspensions of Co<jats:italic><jats:sub>x</jats:sub></jats:italic>Ni<jats:sub>1–<jats:italic>x</jats:italic></jats:sub>Fe<jats:sub>2</jats:sub>O<jats:sub>4</jats:sub>, respectively. The cytotoxicity of the nanoparticles was tested against murine macrophages J774.E, osteosarcoma D17 cells, and human red blood cells (RBCs). The adsorption of bovine serum albumin (BSA) was studied, and the BSA showed a high affinity for the surface of the nanoparticles. The Co<jats:italic><jats:sub>x</jats:sub></jats:italic>Ni<jats:sub>1–<jats:italic>x</jats:italic></jats:sub>Fe<jats:sub>2</jats:sub>O<jats:sub>4</jats:sub> nanoparticles in colloidal suspension showed dose‐dependent cytotoxicity against all of the studied cell lines, and less harmful effects were observed against RBCs at concentrations of up to 0.1 mg/mL. The cytotoxicity towards the D17 and J774.E cells suggests that internalization by the living cells seems to be the key step to elicit the toxic response. Thus, the cytotoxicity of the particles under investigation seems to be cell‐type‐dependent and not uniform. The Co<jats:italic><jats:sub>x</jats:sub></jats:italic>Ni<jats:sub>1–<jats:italic>x</jats:italic></jats:sub>Fe<jats:sub>2</jats:sub>O<jats:sub>4</jats:sub> colloids exhibited superparamagnetic behavior with blocking temperatures (<jats:italic>T</jats:italic><jats:sub>B</jats:sub>) below 300 K. The magnetic characteristics are well preserved in colloidal form and are similar to those of the powdered ferrites.</jats:p>