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

Abstract

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 work, we report a new facile method for radiolabeling silk fibroin nanoparticles conjugated to the chelating agent diethylenetriamine pentaacetic acid and tagged with fluorescein isothiocyanate. Nanoparticles were characterized by means of dynamic light scattering, scanning electron microscopy, and infrared and fluorescence spectroscopy. The in vitro studies included stability in biological media and evaluation of the cytotoxicity of the nanoparticles in a cell culture. The in vivo study was focused on a 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 also assessed 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 in vivo studies. Radiolabeled nanoparticles, having a hydrodynamic radius of 113.2 ± 2.3 nm, a polydispersity index of 0.101 ± 0.015, and a Z-potential of −30.1 ± 2.0 mV, showed an 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.

The Effect of Sterilization on the Characteristics of Silk Fibroin Nanoparticles

“…SFNs were prepared via nanoprecipitation in methanol, adapting our previously described method [ 30 ]. Briefly, SF was dissolved at 10% ( w / v ) in the solvent mixture CaCl 2 /ethanol/H 2 O (1:2:8, molar ratio), also known as Ajisawa’s reagent [ 31 ].…”

“…The size distribution and superficial charge density of nanoparticles were determined by DLS using a Zetasizer Nano ZSP instrument (Malvern Panalytical Ltd., Malvern, UK) following the procedure described previously [ 30 ].…”

Optimizing the Preparation of Silk Fibroin Nanoparticles and Their Loading with Polyphenols: Towards a More Efficient Anti-Inflammatory Effect on Macrophages

“…SFN were prepared using a new nanoprecipitation method evolved from our previously described method [ 35 ]. Briefly, for nanoparticle preparation, the un-dialyzed SF LiBr-aqueous solution was diluted with ultrapure water to 1% SF ( w / v ) and slowly dripped into vigorously stirred methanol.…”

“…The characterization of the nanoparticles was performed using common techniques, such as field emission scanning electron microscopy (FESEM), DLS, attenuated total reflectance-Fourier transformed infrared spectroscopy (ATR-FTIR) and ultraviolet–visible spectroscopy following the procedure described previously [ 35 ].…”

Quantitative Functionalization of the Tyrosine Residues in Silk Fibroin through an Amino‐Tyrosine Intermediate

“…[ 14 ] Carbodiimide‐mediated reactions targeting the carboxylic acid residues have been more widely used as they can be carried out in mild, aqueous conditions. [ 10,11,15–21 ] While simple to execute, silk has a very low number of carboxylic acids (1.1 mol%) which severely limits the density of functionalization possible with carbodiimide coupling. In addition, many biomolecules targeted for attachment to silk contain multiple carboxylic acid or amine groups so exposure to carbodiimide reagents can result in crosslinking and inactivation.…”