Fluorescent DTPA-Silk Fibroin Nanoparticles Radiolabeled with ¹¹¹ In: A Dual Tool for Biodistribution and Stability Studies

摘要： This work aims to provide an effective and novel dual tool for the biodistribution studies of biopolimeric nanoparticles by using modified silk fibroin nanoparticles as a model. This is an indispensable step in the evaluation of the applicability of biopolymeric nanoparticles as drug delivery systems. In this paper, we report a new facile method for radiolabeling silk fibroin nanoparticles conjugated to the chelating agent diethylenetriamine pentaacetic acid (DTPA) and tagged with fluorescein isothiocyanate (FITC). Nanoparticles were characterized by means of dynamic light scattering (DLS), scanning electron microscopy (SEM), infrared and fluorescence spectroscopy. The in vitro studies included the stability in biological media and the evaluation of the cytotoxicity of the nanoparticles in a cell culture. The in vivo study was focused in the scintigraphic study over 24 h conducted on New Zealand rabbits, after intra-articular injection of [111In]In-nanoparticles containing 8.03 ± 0.42 MBq. Biodistribution of the nanoparticles was assessed also ex vivo by fluorescence microscopy of post mortem biopsied organs. This radiolabeling method was reproducible and robust with high radiolabeling efficiency (~80 %) and high specific activity suitable for the in vivo studies. Radiolabeled nanoparticles, having hydrodynamic radius of 113.2 ± 2.3 nm, a polydispersity index (PdI) of 0.101 ± 0.015 and Z-potential of -30.1 ± 2.0 mV, showed and optimum retention in the articular space, without activity clearance up to 24 h post injection. Thus, an easy and robust radiolabeling method has been developed, and its applicability is demonstrated in vitro and in vivo studies, showing its value for future investigation of silk fibroin nanoparticles as versatile and stable (steady) local drug delivery systems for consideration as a therapeutic option, particularly in the treatment of joint disorders.