Development of a Colorimetric Urease Test Based on Au NPS Capped with Anthocyanin for the Rapid Detection of <i>Helicobacter pylori</i> through Multiple Readouts

In this work, we have reported use of anthocyanin capped gold nanoparticles (Ant@Au NPs)-incorporated colorimetric urease test for rapid, sensitive and economic detection of Helicobacter pylori (H. pylori). This test containing Ant@Au NPs, urea, sodium phosphate buffer (PBS) and sodium azide (NaN3) was prepared at pH 5 with red solution owing to dispersity of Ant@Au NPs, urease enzyme secreted from H. pylori cause production of ammonia (NH3) via hydrolysis of urea, then which makes reaction environment alkaline (pH 8.2). The limit of detection for this Ant@Au NPs based urease test was determined to be to 10(2) CFU/mL with proportional to increasing incubation time. However, distinct color change was observed with 10(4) CFU/mL H. pylori suspensions in 15 min. The anthocyanin molecules existing on surface of Ant@Au NPs were easily deprotonated from hydroxyl groups in the alkaline condition, which caused various changes on Ant@Au NPs including quite much negative charges on the surface of Ant@Au NPs analyzed by Zeta potential, aggregation of Ant@Au NPs demonstrated by STEM, DLS and spectrophotometer, and turning the color of test solution to purple evaluated by a naked eye and digital process imaging system.