In Vivo Quantitative Photoacoustic Diagnosis of Gastric and Intestinal Dysfunctions with a Broad pH-Responsive Sensor

Gastrointestinal diseases affect many people in the world and significantly impair life quality and burden the healthcare system. The functional parameters of the gastrointestinal tract such as motility and pH can effectively reflect the changes of gastrointestinal activity in physiological and pathological conditions. Thus, a noninvasive method for real-time and quantitative measurement of gastrointestinal functional parameters in vivo is highly desired. At present, there are many strategies widely used for the diagnosis of gastrointestinal diseases in clinic, including X-ray barium meal examination, ultrasound imaging, radionuclide examination, endoscopy, etc. However, these methods are limited in determining the gastrointestinal status and cannot provide comprehensive quantitative information. Photoacoustic imaging (PAI) is a rapid noninvasive real-time imaging technique in which multiple types of functional and quantitative information can be simultaneously obtained. Unfortunately, very few ratiometric PAI contrast agents have been reported for quantification of gastrointestinal functional parameters in vivo. In this work, a broad, pH-responsive ratiometric sensor based on polyaniline and Au triangular nanoplates was developed. Utilizing the sensor as a contrast agent, PAI served as an all-in-one technique, accurately measuring the gastrointestinal functional parameters in a single test. Notably, this sensor was examined to be ultrasensitive with pH responses as fast as 0.6 s and durability as long as 24 h, and was repeatable and reversible for longitudinal monitoring. The quantitative results demonstrated a significant disorder in motility and decrease in pH for gastric and duodenal ulcers. Collectively, the combination of PM and this broad pH-responsive sensor might be a promising candidate for quantitative diagnosis of gastrointestinal diseases.