Silica-coated bismuth sulfide nanorods as multimodal contrast agents for a non-invasive visualization of the gastrointestinal tract

Abstract

Non-invasive and real-time imaging of the gastrointestinal (GI) tract is particularly desirable for research and clinical studies of patients with symptoms arising from gastrointestinal diseases. Here, we designed and fabricated silica-coated bismuth sulfide nanorods (Bi₂S₃@SiO₂ NRs) for a non-invasive spatial-temporally imaging of the GI tract. The Bi₂S₃ NRs were synthesized by a facile solvothermal method and then coated with a SiO₂ layer to improve their biocompatibility and stability in the harsh environments of the GI tract, such as the stomach and the small intestine. Due to their strong X-ray- and near infrared-absorption abilities, we demonstrate that, following oral administration in mice, the Bi₂S₃@SiO₂ NRs can be used as a dual-modal contrast agent for the real-time and non-invasive visualization of NRs distribution and the GI tract via both X-ray computed tomography (CT) and photoacoustic tomography (PAT) techniques. Importantly, integration of PAT with CT provides complementary information on anatomical details with high spatial resolution. In addition, we use Caenorhabditis Elegans (C. Elegans) as a simple model organism to investigate the biological response of Bi₂S₃@SiO₂ NRs by oral administration. The results indicate that these NRs can pass through the GI tract of C. Elegans without inducing notable toxicological effects. The above results suggest that Bi₂S₃@SiO₂ NRs pave an alternative way for the fabrication of multi-modal contrast agents which integrate CT and PAT modalities for a direct and non-invasive visualization of the GI tract with low toxicity.