Gold nanoparticles allow detection of early-stage edema in mice via computed tomography imaging

Abstract

Due to their high X-ray attenuation, gold nanoparticles (GNPs) emerged as preclinical contrast agents by giving high vasculature contrast. For this reason, GNPs are regularly applied for computed tomography (CT) imaging of tumors but not for the visualization of inflammation. The aim of this study was to evaluate the biocompatibility and applicability of preclinical GNPs (AuroVist™) of two different sizes (1.9 nm and 15 nm) for the detection of inflammation-associated phagocytes in early-stage edema. Both GNP variants were stable under in vitro conditions and achieved high micro-CT (mCT) contrast after embedment into agarose. Fifteen-nanometer GNPs were detected after uptake into macrophages via mCT imaging exhibiting higher X-ray contrast than cells treated with 1.9 nm GNPs and untreated ones. Both 1.9 nm and 15 nm GNPs exhibited good biocompatibility on murine macrophages according to ATP and cellular dehydrogenase levels. Reactive oxygen species levels produced by phagocytic cells decreased significantly (P≤0.05) after co-incubation with GNPs regardless of the size of the nanoparticle (NP) in comparison to untreated control cells. In vivo mCT studies of inflammation imaging revealed that GNPs with a diameter of 15 nm accumulated within subcutaneous edema 2 hours after injection with a maximum signaling 8 hours postinjection and could be detected up to 48 hours within the edema region. In contrast, 1.9 nm GNPs were not shown to accumulate at the site of the inflammation region and were mostly excreted via the renal system 2–4 hours after injection. In conclusion, our study demonstrated that both GNP variants (1.9 nm and 15 nm) were stable and biocompatible under in vitro conditions. However, only 15 nm NPs have the potential as contrast agent for phagocyte labeling and applications in CT imaging of inflammation on a cellular level.

Keywords:

• inflammation
• GNP
• phagocytes
• AuroVist™
• biocompatibility

Supplementary material

Figure S1 In vitro mCT imaging of AuroVist™ 1.9 nm and 15 nm after embedding in 1% agarose and after uptake into murine macrophages.

Notes: (A) Ascending concentrations of AuroVist™ 1.9 nm and 15 nm NPs were embedded in 1% agarose (a), and contrast properties investigated via mCT (b). (B) Murine macrophages (J774A.1 cells) were co-incubated for 24 hours with 100 μg/mL AuroVist™ 1.9 nm and 15 nm. Untreated cells were used as a control for natural cell contrast. After 24 hours of co-incubation, cells were investigated under the microscope (a) (scale bar: 25 μm), subsequently harvested, and CT values of cell pellets were investigated via mCT measurement (b).

Abbreviations: mCT, micro-computed tomography; CT, computed tomography; AV, AuroVist™.

Acknowledgments

The authors would like to kindly acknowledge the support of the Bundesministerium für Bildung und Forschung (BMBF) (project NanoMed). They would also like to thank Yvonne Ozegowski and Heidi Dähring for technical assistance and valuable directions during the mCT-imaging studies. Furthermore, they thank Ian Wright for proofreading the manuscript.

Disclosure

The authors report no conflicts of interest in this work.