Silver nanoparticles functionalized with a fluorescent cyclic RGD peptide: a versatile integrin targeting platform for cells and bacteria

The arginine-glycine-aspartic acid (RGD) peptide sequence is known to specifically interact with integrins, which are chief receptors participating at various stages of cancer disease and in bacterial adhesion/invasion processes. In particular, vitronectin receptor (αvβ3) and fibronectin receptor (α5β1) integrins are involved respectively in tumour cell targeting and bacteria internalization inhibition. Silver nanoparticles (AgNPs) elicited a lot of interest as theranostic platform, owing to their unique optoelectronic as well as self-therapeutic properties as bactericide. The goal of this work was the comprehensive physicochemical characterization of a hybrid peptide-metal nanoparticle biointerface fabricated by the immobilisation, through thiol chemistry, of a fluorescent cyclic RGD peptide onto AgNPs of 13 nm of diameter. RGD peptide-functionalized AgNPs were investigated by a multi-technique approach, including various spectroscopic (XPS, FTIR and UV-visible), spectrometric (ToF-SIMS) and microscopic (SEM, TEM, AFM) methods as well as dynamic light scattering and ζ-potential measurements. Proof-of-work experiments by confocal microscopy imaging of the cellular uptake by human neuroblastoma SH-SY5Y and chronic myelogenous leukaemia K562 cells, overexpressing respectively αvβ3 and α5β1 integrins, demonstrated a receptor-specific activity of the RGD peptide-functionalised AgNPs, which make them very promising as multifaceted platform in applications with cells and bacteria.