Biomedical Engineered Ferrofluids
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1032-I15-07
Biomedical Engineered Ferrofluids Birgit Fischer1, Leidong Mao1, Mustafa Gungormus2, Candan Tamerler-Behar2,3, Mehmet Sarikaya2, and Hur Koser1 1 Electrical Engineering, Yale University, New Haven, CT, 06520 2 Materials Science and Engineering, University of Washington, Seattle, WA, 98195 3 Molecular Biology and Genetics, Istanbul Technical University, Istanbul, Turkey ABSTRACT Ferrofluids have a wide application potential in the field of biomedicine, including cellular manipulation and sorting, hyperthermia and targeted drug delivery. For such applications to be practical, the colloidal suspension of magnetic nanoparticles within a ferrofluid needs to be stable under physiological conditions. Current approaches that utilize non-specific adsorption of surfactants onto nanoparticle surfaces do not provide stability against agglomeration under dilution or increased ionic strength. Here, we present a new approach to synthesizing waterbased and bio-compatible ferrofluids using genetically engineered peptides for inorganics (GEPI’s) that are selected for specific and strong binding to the surface of the nanoparticles. Initial results demonstrate the efficacy of GEPI’s in significantly reducing agglomeration with increasing ionic strength when used in a ferrofluid comprised of cobalt-ferrite nanoparticles surrounded with a thin silica shell. The same approach could easily allow direct biological functionalization of the nanoparticles, rendering such ferrofluids useful in a wide range of applications. INTRODUCTION Ferrofluids are colloidal suspensions comprised of nanosized magnetic particles that are stabilized with a surfactant [1]. Their unique properties have led to a myriad of industrial and medical applications, including their use as liquid seals and bearings, in hard disk drives and speakers, as contrast agents in magnetic resonance imaging and as targeted drug delivery platforms [2]. In most of these applications, stability of the colloidal suspension is critical. Agglomeration of particles eventually leads to deterioration in product performance. In biomedical applications, particle agglomeration in vivo may even lead to dangerous scenarios, such as artery blockages and tissue damage. It is therefore not surprising that significant research effort in the field of ferrofluids goes to improving their stability. Typically, surfactants that non-specifically adsorb to the surface of magnetic nanoparticles are used to stabilize water-based ferrofluids through steric and/or electrostatic mechanisms [1]. Either approach can create ferrofluids that can remain stable on their own for extended periods, but these colloidal suspensions end up being sensitive to dilution, as well as pH and ionic strength changes [3]. Often, biomedical applications require that ferrofluids are stable within a pH of 7.4 and a high ionic strength (up to 500 mM of salt concentration). Using large polymeric surfactants (such as Dextran [4]) for steric repulsion, it is possible to obtain a magnetic liquid that is stable at physiological
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