POLYMERIC FLUORESCENT NANOPARTICLES BASED ON A POLYASPARTAMIDE FOR IMAGING APPLICATIONS: EVALUATION OF GALACTOSE TARGETING ON HEPG2 CELL INTERNALIZATION

In the field of nanomedicine, the use of polymeric fluorescent nanoparticles for in vitro and in vivo imaging is a promising application in order to evaluate passive as well as active targeting strategies [1]. In this work, the synthesis of an amphiphilic galactosylated polylactide-polyaminoacid copolymer bearing rhodamine (RhB) moieties and its use for the preparation of polymeric fluorescent nanoparticles for potential in vitro and in vivo imaging applications are described. To do this, firstly, a fluorescent derivative of α,β-poly(N-2-hydroxyethyl)-D,L-aspartamide (PHEA) was obtained by chemical reaction of PHEA with RhB. Then, a galactosylated derivative of polyethylene glycol, the O-(2-aminoethyl)-O’-galactosyl polyethylene glycol (GAL-PEG-NH2) was obtained by a reductive amination of lactose with primary amine function of poly(ethylene glycol)bis(amine) (H2N-PEG-NH2) in the presence of sodium cyanoborohydride. The fluorescent galactosylated polylactide-polyaminoacid conjugate was obtained by chemical reaction of PHEA-RhB with polylactic acid (PLA), and subsequent reaction with GAL-PEG-NH2, obtaining PHEA-RhB-PLA-PEG-GAL copolymer [2]. Starting from this copolymer, liver-targeted fluorescent nanoparticles, were successfully prepared by high pressure homogenization– solvent evaporation method [2]. Fluorescenti nanoparticles have nanoscaled size and spherical shape as showed by Dinamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM) analyses. Moreover, thanks to the fluorescence given by covalently-linked RhB, by confocal microscopy studies it was demonstrated that these nanoparticles bearing GAL moieties interact with HepG2 cells that are positive for the asialoglycoprotein receptor (ASGP-R), while these do not interact with HeLa cells that are negative for the same receptor, demonstrating the contributor of ASGPR to the internalization process. [1] Vollrath A, S. Schubert, U.S. Schubert, Fluorescence imaging of cancer tissue based on metal-free polimeric nanopaticles - A review, J Mat Chem. 1, 1994 (2013). [2] E.F. Craparo, G. Teresi, M.C. Ognibene, M.P. Casaletto, M.L. Bondì, G. Cavallaro. J Nanoparticle Res. 12, 2629 (2010)