An Alginate Hydrogel-Based Novel Oral Contrast Agent Designed for Gastric Computed Tomography Imaging

In gastric computed tomography (CT), oral contrast agents can enhance the image quality, thereby improving the diagnostic sensitivity and effectiveness for the early detection of gastrointestinal diseases. However, current oral contrast agents are mostly liquid and suffer from rapid gastric emptying rates and short retention times, resulting in unsatisfactory CT results. Here, we present a contrast agent that enables calcium carbonate and sodium alginate to undergo a gelation reaction in the acidic environment of the stomach, facilitating the in situ formation of an iohexol-incorporated calcium alginate hydrogel-based contrast agent. Results from in vivo high-resolution CT scans in mice demonstrate that this hydrogel-based contrast agent remains stable in the stomach for 40 min, whereas liquid contrast agents (like diluted iohexol) were significantly expelled in less than 20 min. After CT scanning, rapid dissolution and excretion can be achieved within 30 min by oral administration of a chelating agent, demonstrating good safety. Compared with traditional liquid contrast agents, this hydrogel-based contrast agent exhibited stronger gastric mucosa adhesion, better gastric distention, and a longer gastric retention time. Therefore, the inherent properties of hydrogel materials facilitate better imaging during gastric CT scans, and they hold potential for application in the diagnosis of gastric disorders.