A simple approach to obtain hybrid Au-loaded polymeric nanoparticles with a tunable metal load.

Edurne Luque-Michel,Edurne Luque-Michel,Edurne Luque-Michel,Edurne Imbuluzqueta,Edurne Imbuluzqueta,Edurne Imbuluzqueta,Jesús Santamaría,Jesús Santamaría,Ane Larrea,Manuel Arruebo,Manuel Arruebo,Víctor Sebastian,María J Blanco-Prieto,María J Blanco-Prieto,María J Blanco-Prieto,Celia Lahuerta

doi:10.1039/c5nr06850a

Abstract

A new strategy to nanoengineer multi-functional polymer-metal hybrid nanostructures is reported. By using this protocol the hurdles of most of the current developments concerning covalent and non-covalent attachment of polymers to preformed inorganic nanoparticles (NPs) are overcome. The strategy is based on the in situ reduction of metal precursors using the polymeric nanoparticle as a nanoreactor. Gold nanoparticles and poly(DL-lactic-co-glycolic acid), PLGA, are located in the core and shell, respectively. This novel technique enables the production of PLGA NPs smaller than 200 nm that bear either a single encapsulated Au NP or several smaller NPs with tunable sizes and a 100% loading efficiency. In situ reduction of Au ions inside the polymeric NPs was achieved on demand by using heat to activate the reductive effect of citrate ions. In addition, we show that the loading of the resulting Au NPs inside the PLGA NPs is highly dependent on the surfactant used. Electron microscopy, laser irradiation, UV-Vis and fluorescence spectroscopy characterization techniques confirm the location of Au nanoparticles. These promising results indicate that these hybrid nanomaterials could be used in theranostic applications or as contrast agents in dark-field imaging and computed tomography.

Highlights

An important advance concerning the production of polymeric nanoparticles (NPs) is the ability to nanoengineer biocompatible polymer–metal hybrid nanostructures with remarkable optoelectronic and biomedical properties.[1]
PLGA particles entrapping the previously synthesized Au NPs were prepared by a water inoil-in-water (w/o/w) emulsion method followed by solvent evaporation of the volatile organic phase at room temperature under stirring (Fig. 2a)
It is likely that some citrate molecules located at the surface of Au NPs form hydrogen bonds between the hydroxyl groups of citrate and the surfactant used in the synthesis of PLGA NPs

Summary

Introduction

An important advance concerning the production of polymeric nanoparticles (NPs) is the ability to nanoengineer biocompatible polymer–metal hybrid nanostructures with remarkable optoelectronic and biomedical properties.[1]. The metallic ions are trapped in the polymeric particle and the reduction reaction is in situ activated by a reducing agent,[19] UV-light[20] or even ultrasounds.[21] this is a more effective and lower-cost protocol than the previous one, the control on the loading and selective encapsulation of metal NPs must be still considerably improved.[10] In addition, to the best of our knowledge, this technique has only been applied to the production of hybrid microparticles,[22,23] but not to NPs. The latter require a higher degree of accuracy regarding encapsulation control especially whenever biomedical applications are considered, where the size of the carriers used in many applications is typically below 200 nm.[24,25]

Results

Conclusion