Breath ammonia detection is a promising non-invasive method for diagnosing Helicobacter pylori infections. However, existing breath ammonia vapor detection techniques face challenges, including high costs, prolonged processing times, complex procedures, and limited selectivity. This study presents a novel sensor based on phospholipid membrane-encapsulated perovskite quantum dots, integrated onto a glass cellulose membrane using electrospinning. The developed sensor undergoes a substitution reaction with ammonia, causing a significant decrease in fluorescence intensity and a visible color change from yellow to colorless. Consequently, a high-sensitivity and high-selectivity sensor for fluorescent quenching and visual detection of breath ammonia vapor was established. The sensor shows a limit of detection of 0.22 ppm, with linear correlations between fluorescence intensity, RGB color changes and ammonia concentration. Compared to traditional perovskite quantum dots, the sensor exhibits enhanced water stability and extended fluorescence lifetime. Additionally, it features rapid response, high stability, and excellent selectivity for ammonia. This sensor demonstrates promising potential for non-invasive detection of Helicobacter pylori infections, offering a new approach for fluorescence-based and visual detection of breath ammonia.
An ultrasensitive enzyme-free electrochemical sandwich DNA biosensor is described for the detection of ssDNA oligonucleotides. A DNA sequence derived from the genom of Helicobacter pylori was selected as a model target DNA. The DNA assay was realized through catching target DNA on capture DNA immobilized gold electrode; then labeling the target DNA with reporter DNA (rpDNA) and initiator DNA (iDNA) co-modified gold nanoparticles (AuNPs). The high density of iDNAs serves as one of the amplification strategies. The iDNA triggers hybridization chain reaction (HCR) between two hairpins. This leads to the formation of a long dsDNA concatamer strand and represents one amplification strategy. The electrochemical probe [Ru(NH 3 ) 5 L] 2+ , where L stands for 3-(2-phenanthren-9-ylvinyl)pyridine, intercalated into dsDNA chain. Multiple probe molecules intercalate into one dsDNA chain, serving as one amplification strategy. The electrode was subjected to differential pulse voltammetry for signal acquisition, and the oxidation peak current at −0.28 V was recorded. On each AuNP, 240 iDNA and 25 rpDNA molecules were immobilized. Successful execution of HCR at the DNA-modified AuNPs was confirmed by gel electrophoresis and hydrodynamic diameter measurements. Introduction of HCR significantly enhances the DNA detection signal intensity. The assay has two linear ranges of different slopes, one from 0.01 fM to 0.5 fM; and one from 1 fM to 100 fM. The detection limit is as low as 0.68 aM. Single mismatch DNA can be differentiated from the fully complementary DNA. Conceivably, this highly sensitive and selective assay provides a general method for detection of various kinds of DNA.
Schematic representation of the detection and the amplification principles of the electrochemical sandwich DNA assay. Purple curl: Captured DNA; Green curl: Reporter DNA; Orange curl: HCR initiator DNA; Yellow solid-circle: Gold nanoparticle; H1 and H2: Two hairpin DNA; [Ru(NH 3 ) 5 L] 2+ : Signal probe.
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