We have studied the synthesis of magnetite (Fe3O4) nanoparticles functionalized with crosslinked dextran for magnetic fluid hyperthermia in human colon cancer cells (CaCo-2). X-Ray diffraction was used to characterize the structure of the synthesized nanoparticles, showing a crystallite size of 9.0 nm. FTIR spectroscopy indicated the presence of dextran in the magnetite samples. SQUID magnetometry was employed to measure the DC magnetization response of the samples, demonstrating superparamagnetic behavior at room temperature, with a saturation magnetization of about 50 A/m, and a magnetic core diameter of about 7.0 nm. TEM was used to confirm an average size of about 9.0 nm. Viability and apoptosis of CaCo-2 cell culture in contact with the nanoparticles were determined at different contact times. No cytotoxic effects were observed. A decrease in cell culture viability of about 60 % was found upon the application of an AC magnetic field of 3.0 kA/m and 1.0 kHz for about 45 min.