Silica Coated Multifunctional Plasmonic Nanoparticles for Theranostics
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Silica Coated Multifunctional Plasmonic Nanoparticles for Theranostics G.A. Sotiriou* and S.E. Pratsinis Particle Technology Laboratory, [email protected] Institute of Process Engineering, Department of Mechanical and Process Engineering Swiss Federal Institute of Technology (ETH Zurich) ABSTRACT Hybrid magnetic/plasmonic nanoparticles possess properties originating from each individual material. Such properties are beneficial for biological applications including bio-imaging, targeted drug delivery, in vivo diagnosis and therapy. Limitations regarding their stability and toxicity, however, challenge their safe use. Here, the one-step flame synthesis of composite SiO2-coated Ag/Fe2O3 nanoparticles is demonstrated. The hermetic SiO2 coating does not influence the morphology, the superparamagnetic properties of the iron oxide particles and the plasmonic optical properties of the silver particles. Therefore, the hybrid SiO2-coated Ag/Fe2O3 nanoparticles exhibit desired properties for their employment in bio-applications. INTRODUCTION Plasmonic (Au or Ag) nanoparticles are superior markers for cell monitoring in bio-imaging, diagnosis (1) and therapy (2). Such nanoparticles can be readily detected and traced by optical microscopy techniques such as dark-field illumination (3), two-photon fluorescence imaging (4), photon illumination confocal microscopy (5). Alternatives to plasmonic nanoparticles for bioimaging are the commonly used fluorescent organic dyes and semiconducting nanoparticles (6). Fluorescent organic dyes, however, exhibit the so-called photobleaching and degrade during bioimaging (7). Semiconducting nanoparticles, on the other hand, exhibit optical blinking (8) while concerns arise for their toxicity as most contain cadmium or lead (6). Even though plasmonic nanoparticles also induce toxicity (9-12), they are functionally advantageous over fluorescent organic dyes and semiconducting nanoparticles because they have superior photostability (13, 14) and can be used also as photothermal therapeutic agents (e.g. tumor treatment) (5), offering an extra functionality in bio-applications (15). When plasmonic nanoparticles are combined with another material, e.g. a magnetic component, multifunctional nanostructured materials are created (2, 15, 16), that can be detected and guided by multiple imaging and control techniques (17, 18). Magnetic resonance imaging (MRI) is an example of a traditional technique, with which small magnetic particles can be used as contrast agents (19) and for targeted drug delivery by directing them to organs, tissues or tumors using an external magnetic field or for magnetically-assisted cell sorting and separation (17). Furthermore, a hermetic SiO2 coating (20-22) on the surface of such magnetic nanoparticles facilitates their surface bio-functionalization and prevents their magnetic particle-particle interaction and flocculation or agglomeration (21, 23). Composite plasmonic-magnetic nanostructures are typically made by multi-step wet methods. Usually, the magnetic particles ar
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