Optimally Designed Nanoshell and Matryoshka-Nanoshell as a Plasmonic-Enhanced Fluorescence Probe

Nanoshell and Matryoshka-nanoshell constructs are rationally optimized utilizing the finite-difference time-domain method to design probes with enhanced fluorescence. Through the systematical investigation of interactions between the spontaneous emission of a single emitter and a metal-based nanostructure, the plasmonic-enhanced fluorescence is found maximal for certain morphologies that balance two competitive factors: field enhancement and quantum efficiency. For instance, key parameters such as the emitter’s position, its orientation, and the spectral overlaps between molecular bands and plasmon resonance are investigated to fully understand the complete behavior of the system. In the case of metal nanoshells, it is shown that the molecular fluorescence is differently enhanced inside or outside the shell. In that of Matryoshka-nanoshells that consist of concentric gold core and shell, the construct appears as an exceptionally promising probe especially when the fluorophore lies within the gap layer. Indeed, the strong coupling between the adjacent core and shell allows electromagnetic excitation to be squeezed within the gap, so resulting in giant fluorescence and photostability. Such a construct opens a way for still increasing the sensitivity of fluorescence detection, which is promising for almost all biological imaging applications

Functionalization of Small Rigid Platforms with Cyclic RGD Peptides for Targeting Tumors Overexpressing α_vβ₃‑Integrins

Gadolinium based Small Rigid Plaforms (SRPs) have previously demonstrated their efficiency for multimodal imaging and radiosensitization. Since the RGD sequence is well-known to be highly selective for α_vβ₃ integrins, a cyclic pentapeptide containing the RGD motif (cRGDfK) has been grafted onto the SRP surface. An appropriate protocol led to the grafting of two targeting ligands per nano-object. The resulting nanoparticles have demonstrated a strong association with α_vβ₃ integrins in comparison with cRADfK grafted SRPs as negative control. Flow cytometry and fluorescence microscopy have also been used to highlight the ability of the nanoparticles to target efficiently HEK293­(β3) and U87MG cells. Finally the grafted radiosensitizing nanoparticles were intravenously injected into <i>Nude</i> mice bearing subcutaneous U87MG tumors and the signal observed by optical imaging was twice as high for SRP-cRGDfK compared to their negative analogue