Ferrofluids and magnetic particles for biomedical applications

The interest aroused by magnetic particles for biomedical applications (sample preparation, specific extraction of analytes, generic extraction of biomolecules, etc.) has recently resulted in a large number of works and books, as well as the development of a large number of colloidal magnetic supports. In general, the success of a test in biomedical diagnostics lies not only in the development of high-performance detection tools, but also in the preparation of samples, which necessarily require pre-treatment. For example, in the case of analysis tests based on the detection and identification of nucleic acids, this pre-treatment consists of releasing the nucleic material into the medium, capturing and purifying it before the amplification and detection steps can be implemented. The use of magnetic particles not only makes it possible to increase the sensitivity of certain tests, but also to envisage their automation or integration into microsystems, where the speed of magnetic separation under the action of an external magnetic field is an essential asset, replacing filtration and centrifugation. The development of bionanotechnology applications has led to the use of magnetic colloids (submicron in size) as biomolecule carriers for a variety of applications: in vitro as solid carriers for the extraction, purification, concentration and transport of biomolecules, or simply as detection tools, and in vivo as contrast agents (in vivo diagnostics), cancer treatment and the release of active molecules (therapeutics).

The most commonly used magnetic colloids are either inorganic nanoparticles or hybrid particles (composed of a mixture of organic and inorganic particles) between 10 nm and 10 μm in size.) These particles are generally composed of iron oxide nanoparticles (between 5 and 12 nm in size), and their production involves obtaining a dispersion of magnetic nanoparticles known as a "ferrofluid".

The main aim of this article is to introduce the concept of ferrofluid, the preparation of dispersible magnetic nanoparticles in aqueous or organic phase and their uses in the biomedical field in vitro and in vivo.