New Biocompatible Nanoparticles: Multistep Chemical Modifications and Biological Applications

We have developed new biocompatible, non-degradable NPs well tolerated both in vitro and in vivo with the particularity that peptide synthesis can be carried out on their surface. Although the NP's have a large range of well-defined sizes going from 20 to 400 nm, they are all composed of the same monomers. Their shell composition, in contact with the biological media, is uniformly composed of polyethylene-glycol, thus their biocompatibility remains high along the different sizes. A proposed peculiar mechanism of formation allowed maintaining uniform their shell composition. The conjugation of molecules to the NPs was a real challenge since they are nano-hydrogels with high colloidal stability that can only be dialyzed for eventual removal of reagents. Therefore we have designed and proved a novel solid phase peptide synthesis method for Merrifield synthesis on nanoparticles based on the embedment of the NPs in a permeable and removable magnetic matrix. The platform composed of the NPs and the synthetic peptide is a useful tool for imaging methods for intracellular localization of the NPs using microscopy as we have shown in vitro for PC-3 cells a system using TAT, NLS and TAT-NLS peptides on the nanoparticles, and for in vivo tracking using the Zebra fish model. In a semi-quantitative confocal microscopy study, we have shown that nanoparticles bearing both TAT and NLS sequences not only mediate cell penetration and nuclear localization, but also has a dramatic effect on the amount of material that penetrates into the cell as compared to nanoparticles bearing TAT alone. This result suggests that NLS plays a role not only in nuclear penetration but also in cell penetration when properly combined with cell penetrating peptides.