Development of an Au nanoclusters based activatable nanoprobe for NIR-II fluorescence imaging of gastric acid.

Gastric acid is an important functional substance secreted by the stomach of the living organisms, reflecting the gastric physiological condition. The sensing of gastric acid in vivo is of great significance for evaluation of gastric function, diagnosis and treatment of gastric diseases and maintenance of organism health but remains challenging due to the harsh acid and digestive environment of stomach. This study developed an activatable nanoprobe based on Au nanoclusters (Au NCs) for sensitive and real-time noninvasive near-infrared II (NIR-II) fluorescence imaging detection of gastric acid in vivo for the first time. The Au NCs were encapsulated by polydopamine to have enhanced NIR-II luminescence and high stability and combined with methylene blue to possess the pH responsiveness for gastric acid imaging. The developed nanoprobe could not only monitor gastric acid secretion in vivo but also imaging the changes of gastric acid caused by feeding, acid-inhibition drugs and gastric ulcer disease. This study provides a promising avenue for the improvement of the application performance of Au NCs and imaging analysis of gastric acid and related gastric diseases.