Magnetic Apatites for Biomedical Applications

Biomedical applications utilizing magnetic nanoparticles have the ability to impact diagnostic and therapeutic outcomes and beneficially affect numerous patients worldwide. Paramagnetic nanoparticles can potentially be used to improve targeting in drug delivery systems, improve contrast in biomedical imaging, and treat cancer via hyperthermia. Unfortunately, the most widely used type of nanoparticles for several biomedical applications are currently iron oxides. Safety is a constant concern when using these types of materials as toxicity limits therapeutic efficiency, as well as having the potential to induce new damage and problems in the patient’s cells. For these reasons, iron oxide particles often require the application of a biocompatible coating, which can be unstable. Hydroxyapatite, the main inorganic component of natural bone, is widely studied as a biomaterial due to its excellent biocompatibility. Furthermore, the crystal structure of hydroxyapatite lends itself to a wide variety of substitutions and ion doping, which allows for tailoring of material properties. Substituted hydroxyapatite with paramagnetic properties is of interest as a promising biomaterial to be used to replace iron oxides in biomedical applications. In this work, both iron- and cobalt-substituted hydroxyapatite powders were synthesized. Iron-substituted hydroxyapatite (FeHA) was created by subjecting pure hydroxyapatite to a simple room temperature ion exchange procedure. Cobalt-substituted hydroxyapatite (CoHA) was synthesized using both ion exchange and via wet synthesis. All resulting powders were carefully characterized to verify that the ion of interest had substituted into the apatite lattice, thus yielding a phase-pure material. Iron- and cobalt-substituted hydroxyapatites were further found to be materials with paramagnetic properties. Both materials were subjected to sintering and cell culture studies to evaluate their stability and suitability for the proposed applications of drug delivery, MRI contrast agents, and nanoparticles for hyperthermia based cancer treatments. Characterization of these substituted apatite materials indicate that FeHA and CoHA are biodegradable and biocompatible materials with paramagnetic properties, thus resulting in a wider range of potential applications than pure HA, including, but not limited to, cell stimulation in bone repair, cell labelling and separation, and combined therapies, as well as drug delivery, MRI contrast agents, and hyperthermia based cancer treatments