Ultrasensitive detection of trace Hg2+ by SERS aptasensor based on dual recycling amplification in water environment

Due to the nonbiodegradability and accumulation of mercury ion, even in extremely small amount, it will cause varying degrees of harm to environment and human health. Although researchers have developed many strategies to detect and monitor trace Hg²⁺, only a few provide sensitivities of less than 1.0 pM. Surface Enhanced Raman Spectroscopy (SERS) is a common method to detect mercury ion due to its high sensitivity, rapid detection and easy operation. In this work, we report a new SERS aptasensor based on dual recycling amplification for the detection of trace mercury ion, which combines SERS with nucleic acid signal amplification through functional aptamer and elaborately designed hairpin DNA. Under the optimal experimental conditions, this SERS aptasensor exhibits excellent selectivity and high sensitivity. A linear range (0.2-125 fM) and a low detection limit (0.11 fM) are obtained. By using specific aptamers, the strategy will provide a new idea for the trace detection of toxic contaminants in water environment.

Development of a rapid and simple tetracycline detection system based on metal-enhanced fluorescence by europium-doped AgNP@SiO2 core–shell nanoparticles

We herein describe a rapid and selective sensing platform for tetracycline (Tc), which relies on the metal-enhanced fluorescence (MEF) effect of europium (Eu³⁺)-doped silver-silica core–shell nanoparticles (AgNP@SiO₂). The developed assay utilizes AgNP@SiO₂ as a key detection component, which is systematically optimized to have a silica shell thickness suitable for the effective MEF phenomenon. In principle, the AgNP@SiO₂, which binds to Eu³⁺ through the electrostatic interaction, captures Tc by selective chelation with Eu³⁺, leading to significant fluorescence enhancement of the EuTc complex. Based on this novel strategy, we determined Tc as low as 83.1 nM with a total assay time of less than 10 min, which is comparable to or better than that of the previous fluorescence-based methods. Furthermore, the practical applicability of this strategy was successfully demonstrated by detecting Tc in tap water. This work highlights the unique features of AgNP@SiO₂ for MEF-based biosensing applications.

Tetracycline (Tc) selectively binds with europium (Eu³⁺) which emits red fluorescence (615 nm) upon excitation at 400 nm.