Supramolecular assembly of pentamidine and polymeric cyclodextrin bimetallic core-shell nanoarchitectures

Advanced nanoscale antimicrobials, originated from the combination of noble metal nanoparticles (NPs) with conventional antimi-crobial drugs, are considered the next generation of antimicrobial agents. Therefore, there is an increasing demand for rapid, eco-friendly, and relatively inexpensive synthetic approaches for the preparation of nontoxic metallic nanostructures endowed with unique physicochemical properties. Recently, we have proposed a straightforward synthetic strategy that exploits the properties of polymeric beta-cyclodextrin (PolyCD) to act as both the reducing and stabilizing agent to produce monodispersed and stable gold-based NPs either as monometallic (nanoG) structures or core-shell bimetallic (nanoGS) architectures with an external silver layer. Here, we describe the preparation of a supramolecular assembly between nanoGS and pentamidine, an antileishmanial drug endowed with a wide range of therapeutic properties (i.e., antimicrobial, anti-inflammatory, and anticancer). The physicochemical characterization of the supramolecular assembly (nanoGSP) in terms of size and colloidal stability was investigated by complemen-tary spectroscopic techniques, such as UV-vis, zeta-potential, and dynamic light scattering (DLS). Furthermore, the role of PolyCD during the reduction/stabilization of metal NPs was investigated for the first time by NMR spectroscopy.

Automated summary

Advanced nanoscale antimicrobials, combining noble metal nanoparticles with conventional antimicrobial drugs, are considered as the next generation of antimicrobial agents. The demand for rapid, eco-friendly, and relatively inexpensive synthetic approaches for nontoxic metallic nanostructures with unique physicochemical properties is increasing. A straightforward synthetic strategy using polymeric beta-cyclodextrin as the reducing and stabilizing agent has been proposed to produce monodispersed and stable gold-based nanoparticles, either as monometallic structures or core-shell bimetallic architectures with an external silver layer. In this article, the preparation of a supramolecular assembly between these nanoparticles and pentamidine, an antileishmanial drug with a wide range of therapeutic properties, is described. The physicochemical characterization of the supramolecular assembly was investigated by complementary spectroscopic techniques, and the role of PolyCD in the reduction/stabilization of metal nanoparticles was investigated for the first time by NMR spectroscopy.