Catechol-hydrazone conjugates for the rapid functionalization of magnetite nanoparticles with cell targeting groups
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Catechol-hydrazone conjugates for the rapid functionalization of magnetite nanoparticles with cell targeting groups Thomas Coxon,1,2 Andrew Almond,2 Julie E. Gough3 and Simon J. Webb1,2 1
School of Chemistry, The University of Manchester, Manchester M13 9PL, UK. MIB, The University of Manchester, 131 Princess Street, Manchester M1 7DN, UK 3 School of Materials, The University of Manchester, Manchester M1 7HS, UK 2
ABSTRACT The condensation of hydrazides with aldehydes has been found to be a simple and rapid method for synthesizing catechol-terminated coating reagents for magnetite nanoparticles. This approach allowed the production of biotin- and polyethylene glycol-functionalized nanoparticles, whose interaction with 3T3 fibroblast cells has been assessed. The cellular location of these nanoparticles was imaged by fluorescence microscopy, which was made possible by co-coating with a porphyrin-catechol conjugate. Images show significant interactions between biotinylated nanoparticles and 3T3 fibroblasts, but those with a polyethylene glycol coating did not interact. INTRODUCTION Magnetite nanoparticles have been used for a wide variety of applications in the biomaterials field.1 These applications commonly rely on the superparamagnetic properties that are observed in magnetite nanoparticles with a diameter below around 25 nm.2 Such nanoparticles can not only be manipulated by a static magnetic field, but they can also generate heat when exposed to an alternating magnetic field. This process, occurring through Brownian or Néel relaxation, can be exploited for hyperthermia applications3 and has even been utilized for biomolecule delivery.4 However, many applications require surface modification in order for the nanoparticles to function effectively. In the case of magnetite nanoparticles, surface functionalization is most often achieved by dextran coating5, 3-aminopropyltriethoxysilane (APTES) coating6 or adding a catechol-containing molecule.7 The phenolic diol of catechols in particular forms strong chelates with metal-oxide surfaces, and catechols have been exploited to give a range of resilient surface coatings.8 One popular approach is to use dopamine9, which can be covalently functionalized separately or on the nanoparticle surface. However, the conjugates formed, often linked through amide bonds, can be difficult to form and purify. A simple alternative is to take advantage of the facile and selective condensation reaction between hydrazides and aldehydes. The reaction between the highly nucleophilic hydrazide group and an aldehyde carbonyl is selective and rapid when catalyzed by aniline.10 By utilizing 3,4-dihydroxybenzaldehyde, a catechol group can be easily be grafted onto any hydrazide-containing molecule. To exemplify the ease with which this chemistry can be exploited to provide surface-functionalized magnetite nanoparticles, biotinylated and PEGylated nanoparticles have been produced. Biotin coatings have proven to interact with cell surface receptors in a variety of cell types, receptors that are ove
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