Signal-On and Highly Sensitive Electrochemiluminescence Biosensor for Hydrogen Sulfide in Joint Fluid Based on Silver-Ion-Mediated Base Pairs and Hybridization Chain Reaction.

Hydrogen sulfide (H₂S) in joint fluid acts as a signal molecule to regulate joint inflammation. Direct detection of H₂S in joint fluid is of great significance for the diagnosis and treatment of arthritis. However, due to the low volume of joint fluid and low H₂S concentration, existing methods face the problem of the insufficient limit of detection. In this study, a highly sensitive biosensor was proposed by designing a primer probe and combining it with hybrid chain reaction (HCR) under the strong interaction between metal ions and H₂S to achieve H₂S detection. The primer probe containing multiple cytosine (C) sequences was fixed on a gold electrode, and the C–Ag–C hairpin structure was formed under the action of Ag⁺. In the presence of H₂S, it can combine with Ag⁺ in the hairpin structure to form Ag₂S, which leads to the opening of the hairpin structure and triggers the hybridization chain reaction (HCR) with another two hairpin structures (H1 and H2). A large number of double-stranded nucleic acid structures can be obtained on the electrode surface. Finally, Ru(phen)₃²⁺ can be embedded into the double chain structure to generate the electrochemiluminescence (ECL) signal. The linear response of the H₂S biosensor ranged from 0.1000 to 1500 nM, and the limit of detection concentration of H₂S was 0.0398 nM. The developed biosensor was successfully used to determine H₂S in joint fluid. [ABSTRACT FROM AUTHOR]