Direct interaction of hydrophilic gold nanoparticles with dexamethasone drug: Loading and release study Iole Venditti a , Laura Fontana a , Ilaria Fratoddi a,b,⇑ , Chiara Battocchio c , Cesare Cametti d , Simona Sennato d , Francesco Mura b , Fabio Sciubba a , Maurizio Delfini a , Maria Vittoria Russo a a Department of Chemistry, Sapienza University of Rome, P.le A. Moro 5, 00185 Rome, Italy b Center for Nanotechnology for Engineering (CNIS), Sapienza University of Rome, P.le A. Moro 5, 00185 Rome, Italy c Department of Science, Roma Tre University of Rome, Via della Vasca Navale 79, 00146 Rome, Italy d Department of Physic and CNR-IPCF UOS of Rome, P.le A. Moro 5, 00185 Rome, Italy article info Article history: Received 3 October 2013 Accepted 23 November 2013 Available online 4 December 2013 Keywords: Hydrophilic gold nanoparticles Drug loading Dexamethasone Drug delivery Functionalized nanoparticles abstract Water-soluble gold nanoparticles functionalized by sodium 3-mercapto-1-propansulfonate (Au-3MPS) were synthesized with different Au/thiol molar ratios for their ability to interact with biomolecules. In particular, a synthetic glucocorticoid steroid, i.e. dexamethasone (DXM) was selected. Herein, the forma- tion of the Au-3MPS/DXM bioconjugate is reported. Au-3MPS nanoparticles show a plasmon resonance at 520 nm, have a spherical morphology and average size of 7–10 nm. The total number of gold atoms was estimated to be about 10600, with a surface component of 8800 atoms and a number of thiol ligands of about 720, roughly one anchored thiol every 10 surface gold atoms. The drug-nanoparticle interaction occurs through the fluorine atom of DXM and Au(I) atoms on the gold nanoparticle surface. The 3MPS ligands closely pack apart each other to leave room for the DXM, that lies at the gold surface in an unu- sual, almost parallel feature. The loading efficiency of DXM on Au-3MPS was assessed in the range 70– 80%, depending on the thiol content. Moreover, our studies confirmed the drug release of about 70% in 5 days. Thanks to their unique properties, i.e. high water solubility, small size and almost monodispersity, Au-3MPS display high potential in biotechnological and biomedical applications, mainly for the loading and release of water insoluble drugs. Ó 2013 Elsevier Inc. All rights reserved. 1. Introduction Nanostructured materials play a key role in the scientific com- munity for their fascinating properties that allow their use in ad- vanced applications [1–3]. The transport and release of therapeutic materials to specific target, represents one of the most interesting challenges to which the biomedicine is called; an example is represented by gold nanoparticles (AuNPs) that can be used in the hyperthermia treatment [4,5]. For this purpose sev- eral delivery systems have been investigated, including polymers, liposomes, polymeric micelles and vesicles, dendrimers and metal- lic nanoparticles [6–9]. Gold nanoparticles have proved to be a promising carrier towards different cell types, thanks to a variety of physical–chemical properties, that make these particles a privi- leged candidate in drug transport and release applications. More specifically, the gold core is substantially inert, non-toxic and biocompatible, and represents an ideal starting point for the building up of a composite carrier. Gold nanoparticles can be produced with a good control of shape or size dispersity and func- tionality [10]. Several techniques for AuNPs characterization allow a good estimation of the grafting density, in particular for covalent functionalization [11,12]. Moreover, it is possible to address the synthesis towards a specific target, with size comparable with bio- molecules, such as proteins or DNA, facilitating particle integration into biological systems. Furthermore, the high surface/volume ra- tio allows a tunable degree of functionalization, both with mole- cules able to bind the target and with therapeutic and drug compounds [13]. Dexamethasone (DXM), a synthetic glucocorticoid steroid, is one of the most widely used drugs for the treatment of myeloma [14]. This drug has been used as a therapeutic agent for several inflammatory diseases, because of the suppression of the expres- sion of inflammatory genes [15,16]. DXM is also used in the treat- ment of inflammatory diseases such as asthma [17], meningitis [18], and rheumatoid arthritis [19]. Finally, DXM is an hydrophobic bioactive compound largely used in tissue engineering applications [20]. Because of the above stated characteristics of this bioactive molecule, DXM-loaded AuNPs may represent a promising candi- date to be an effective carrier in drug delivery. However, the drug 0021-9797/$ - see front matter Ó 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jcis.2013.11.063 ⇑ Corresponding author at: Department of Chemistry, Sapienza University of Rome, P.le A. Moro 5, 00185 Rome, Italy. Fax: +39 06490324. E-mail address: ilaria.fratoddi@uniroma1.it (I. Fratoddi). Journal of Colloid and Interface Science 418 (2014) 52–60 Contents lists available at ScienceDirect Journal of Colloid and Interface Science www.elsevier.com/locate/jcis