In Vivo Evaluation of Innovative Gadolinium-Based Contrast Agents Designed for Bioimaging Applications

Abstract

The aim of this study was the investigation of biochemical and histological changes induced in different tissues, as a result of the subcutaneous administration of Gd nanohydrogels (GdDOTA⸦CS-TPP/HA) in a CD-1 mouse strain. The nanohydrogels were obtained by encapsulating contrast agents (GdDOTA) in a biocompatible polymer matrix composed of chitosan (CS) and hyaluronic acid (HA) through the ionic gelation process. The effects of Gd nanohydrogels on the redox status were evaluated by measuring specific activities of the antioxidant enzymes catalase (CAT), glutathione peroxidase (GPx), and superoxide dismutase (SOD), as well as oxidative stress markers, such as reduced glutathione (GSH), malondialdehyde (MDA), advanced oxidation protein products (AOPP), and protein-reactive carbonyl groups (PRCG), in the liver, kidney, and heart tissues. The nitrosylated proteins expression were analyzed with Western Blot and the serum biochemical markers were measured with spectrophotometric methods. Also, a histological analysis of CD-1 mouse tissues was investigated. These results indicated that Gd nanohydrogels could potentially be an alternative to current MRI contrast agents thanks to their low toxicity in vivo.

Keywords: gadolinium-based contrast agents; magnetic resonance imaging; nanohydrogels.

Figure 1

Experimental design. (a) Before administration; (b) injection; and (c) injection site after administration.

Figure 2

The histological aspect of the (a) liver, (b) myocardial tissue, and (c) kidney following administration of GdDOTA⊂CS-TPP/HA for 24 and 48 h, respectively. Hematoxylin and eosin (H&E) staining; * Hypertrophied renal glomeruli; Magnification objective 10× (a), 40× (b) and 20× (c).

Figure 3

(A) The specific activity of superoxide dismutase (SOD), (B) catalase (CAT), and (C) glutathione peroxidase (GPx) in the liver, kidney, and heart 24 and 48 h after the subcutaneous injection of GdDOTA⊂CS-TPP/HA nanohydrogels. Data are calculated as mean value ± SD (n = 6) and expressed relative to the corresponding control. * p < 0.05 (significant, compared to control); ** p < 0.01 (distinctly significant, compared to control); *** p < 0.001 (very significant, compared to control); # p < 0.05 (significant, between the two time intervals); and ### p < 0.001 (highly significant, between the two time intervals).

Figure 4

Total nitrosylated protein expression 24 and 48 h after GdDOTA NGs injection in liver, kidney, and heart. (A) represents the profile of nitrosylated proteins, and (B) represents the quantifying of the bands and the graphic representation of the protein expression compared to the control. The asterisks represent the statistical significance obtained with the Student’s t-test, as follows: p < 0.05 *; The vertical bars represent the standard deviation.