Polymer coated inorganic nanoparticles: tailoring the nanocrystal surface for designing nanoprobes with biological implications† Alessandra Quarta, a Alberto Curcio, b Hamilton Kakwere b and Teresa Pellegrino * ab Received 3rd February 2012, Accepted 12th March 2012 DOI: 10.1039/c2nr30271c The use of inorganic nanoparticles in biomedicine, in particular in the field of diagnosis and therapy of human diseases, has rapidly grown in the last few decades. Water solubilisation of the nanoparticles, especially for particles synthesized in non-polar solvents, is an essential prerequisite for their biological exploitation. The encapsulation of surfactant coated nanoparticles into polymer shells represents one of the most suitable and most popular methods to make them water soluble. Herein we provide an overview of the amphiphilic polymer molecules used and the efforts undertaken to further tailor the surface of polymer coated nanoparticles with fluorescent dyes, chemical sensor molecules and small or large biomolecules for the preparation of bio-functional nanoprobes. Their biological implications, highlighting limitations and challenges, are also discussed. 1. Introduction Inorganic nanocrystals of magnetic, semiconductor and metallic materials have become cutting-edge tools in nanomedicine. They consist of crystalline clusters of atoms (from few to several tens of thousands) and when the size of the materials is reduced to the nanometre scale, their intrinsic properties can be drastically modified and new physical properties can arise. It soon became clear that the size-dependent optical features of semiconductor nanocrystals, also known as quantum dots, could make them exploitable as fluorescent markers in many biological studies, while gold nanoparticles which exhibit size dependent adsorp- tion/scattering of light could also be exploited as bio-imaging tools for the colorimetric detection of analytes/species in many nano/micro-chip technologies. 1–5 On the other hand, the superparamagnetic behaviour of magnetic nanocrystals, in particular the iron oxide nanoparticles (IONPs), has made them appealing as nanocarriers in drug delivery and as contrast agents in magnetic resonance imaging (MRI). 6,7 Additionally, in the last 30 years IONPs have gained popularity as heating probes in hyperthermia treatments. The heat generated by the magnetic nanocrystals under appropriate alternating magnetic field can induce the selective death of tumour cells since they are more sensitive to heat than normal cells. 8,9 For a similar therapeutic approach, other metallic nanoparticles are also of interest. Gold nanorods, nanocages, nanostars, or nanostructures containing many gold and silver nanoparticles can generate heat when excited with a laser irradiation and can therefore be exploited for photothermal ablation of tumours. 10–12 Besides the intrinsic properties of nanocrystals of different compositions, at the nanoscale several physical–chemical parameters, including the size, the shape, the surface to volume ratio, and the surface chemistry individually or in combination, Alessandra Quarta is researcher at the Nanoscience Institute of CNR, Lecce (NNL-Lab, Lecce, Italy). She received an MSc degree in biology from University of Salento and in 2008 obtained a PhD degree in Innovative Materials and Technologies from the National Nanotechnology Laboratory (NNL), Lecce, with a thesis on ‘‘Biofunctionalization of inorganic nanocrystals and their exploitation in life science.’’ Her current research interests include the development and functionalization of inorganic nanocrystals with biomolecules for applications in the biomedical field. Alberto Curcio is a PhD student at the Nanochemistry division of the Italian Institute of Technology of Genoa (Italy). He graduated in Medical Biotechnology at the University of Naples, with a thesis on cancer cell migration and signaling transduction. He is currently working on exploitation of magnetic nanostructures as anticancer drug delivery tools combined with hyperthermia therapy mediated by magnetic nanoparticles. a National Nanotechnology Laboratory of CNR-NANO, via per Arnesano km 5, 73100 Lecce, Italy. E-mail: teresa.pellegrino@unisalento.it; Fax: +39 0832 298 230; Tel: +39 0832 298 214 b Istituto Italiano di Tecnologia, via Morego 30, 16163 Genova, Italy † Electronic supplementary information (ESI) available: Experimental section and additional details on structural characterization of the various nanoparticles functionalized conjugates are included. See DOI: 10.1039/c2nr30271c This journal is ª The Royal Society of Chemistry 2012 Nanoscale, 2012, 4, 3319–3334 | 3319 Dynamic Article Links C < Nanoscale Cite this: Nanoscale, 2012, 4, 3319 www.rsc.org/nanoscale FEATURE ARTICLE Published on 26 March 2012. Downloaded on 30/07/2014 14:55:22. View Article Online / Journal Homepage / Table of Contents for this issue