Synthesis of silica-coated aqueous ferrofluids through ligand exchange with a new organosilica precursor
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Synthesis of silica-coated aqueous ferrofluids through ligand exchange with a new organosilica precursor Ana Arizaga • Angel Milla´n • Ulrich Schubert Fernando Palacio
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Received: 26 September 2012 / Accepted: 21 November 2012 / Published online: 4 December 2012 Ó Springer Science+Business Media New York 2012
Abstract A new method for the production of aqueous dispersions of superparamagnetic iron oxide nanoparticles with applications in biomedicine is reported. The method is based on the use of a triethoxisilyl dodecanoic acid ligand that has been specially synthesized for this purpose. The nanoparticles were grown in organic medium using oleic acid as surfactant. Subsequently, oleic acid was exchanged for the alkoxysilane ligand, then hydrolysis was performed in a hydrocarbon solvent, and the nanoparticles were transferred into water. The organic and aqueous ferrofluids have been characterized and their magnetic properties have been determined. The resulting maghemite/silica nanoparticles were single core, and stable in aqueous suspension.
Introduction The application of superparamagnetic nanoparticles (SPN) in biomedicine has opened very appealing perspectives [1–3]. They were first applied in biotechnology in the 70s as enzyme carriers, and later in separation, purification, analysis, catalysis, and processing [4, 5]. Nowadays, they are also employed in diagnosis for the fabrication of biosensors and as magnetic resonance imaging (MRI) contrast agents [6, 7]. The advantage of SPN with respect to usual contrast agents is their high sensitivity that is expected to
A. Arizaga (&) A. Milla´n F. Palacio Facultad de Ciencias, ICMA, CSIC-Universidad de Zaragoza, Pza. San Francisco s/n, 50009 Zaragoza, Spain e-mail: [email protected] U. Schubert Institut fu¨r Materialchemie, Technische Universita¨t Wien, Getreidemarkt 9/165, 1060 Wien, Austria
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reach single cell detection [8]. Among the applications that are currently under development, targeted drug delivery and cancer therapy are especially important. The use of SPN in cancer therapy is based on their heating capacity under the effects of an alternating magnetic field. This technique is already in clinical phase for particles directly injected in the tumor [9]. Developing biologically vectorized particles, however, would be a major achievement in the treatment of cancer because it would allow reaching tumors that, due to their location and/or small size, are currently not accessible by other therapies [10]. An additional advantage associated with this technology is that it would avoid most of the undesirable secondary effects associated with radiotherapy and chemotherapy treatments [11]. The utility of SPN in medicine can go even further as they may allow performing therapy and diagnosis simultaneously, thus entering the most promising area of theranostics [12]. The standard magnetic nanoparticle systems used in biomedical applications comprise: (1) a magnetic part that consists of a single or several magnetic nanoparticles; (2) a shell that makes them s
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