A smart nanopaper sensor for optical diagnosis of infection

Despite a decline in its prevalence, Helicobacter pylori ( H. pylori ), as the most common causative agent of chronic gastrointestinal diseases, still infects more than half of the world's population. Although effective, current H. pylori infection diagnostic approaches entail some drawbacks and hurdles, including requiring endoscopy and multiple biopsies, harmful chemicals, and expensive and bulky apparatus. Herein, to tackle some of state-of-the-art limitations, we have developed a biocompatible nanosensor for diagnosis of H. pylori infection. The developed optical sensor comprises NaYF 4 :Yb,Er,Lu@PEG-NH 2 upconversion nanoparticles, red cabbage-extracted anthocyanins, and iron oxide nanoparticles embedded within chitin nanopaper. The enzymatic reaction of H. pylori urease enzyme with urea, which leads to pH changes, and consequently changes in the pH-dependent fluorescence/color profile of the developed sensor via an inner filter effect mechanism, was utilized as a sensing strategy for H. pylori infection diagnosis. A portable 3D-printed smartphone-based imaging platform was also fabricated for monitoring the developed sensor. We believe that our developed smart nanosensor can not only potentially be exploited as an ingestible sensor for non-invasive diagnosis of H. pylori infection, its therapeutic monitoring, and gastrointestinal pH monitoring, but also provide fresh insights into the development of a variety of innovative ingestible/swallowable sensors for non-invasive gastrointestinal diagnostics. Herein, a low cost, non-toxic, and easy-to-fabricate/use optical nanosensor has been developed capable of potentially being exploited as a smart ingestible sensor for on-body and non-invasive monitoring of gastric pH/ H. pylori infection.