Here, we present a mapping tool based on individual light-driven nano-oscillators for label-free single-molecule monitoring of microRNA. This design uses microRNA as a single-molecule damper for nano-oscillators by forming a rigid dual-strand structure in the gap between nano-oscillators and the immobilized surface. The ultrasensitive detection is attributed to comparable dimensions of the gap and microRNA. A developed surface plasmon-coupled scattering imaging technology enables us to directly measure the real-time gap distance vibration of multiple nano-oscillators with high accuracy and fast dynamics. High-level and low-level states of the oscillation amplitude indicate melting and hybridization statuses of microRNA. Lifetimes of two states reveal that the hybridization rate of microRNA is determined by the three-dimensional diffusion. This imaging technique contributes application potentials in a single-molecule detection and nanomechanics study.
Classic electrochemiluminescence (ECL) assays relying on the change in luminescence intensity face a challenge in the quantitative analysis of complex samples. Here, we report the design and implementation of a new sensing strategy, using the maximum luminescence wavelength (λ) shift as the readout to achieve quantitative detection. This approach includes an ECL luminophore (RuSiO@GO) and a HS-sensitive inner filter absorber (CouMC). The absorbance of CouMC illustrates a dependence on the HS concentration, which induces a change in the maximum luminescence wavelength (Δλ) of the ECL luminophore. Both experimental and simulated results suggest that the spectral shift of ECL effectively avoids the interference of the total luminescence intensity fluctuations, enabling a highly reliable quantitative analysis. This spectral shift-based ECL assay strategy offers a wide application potential by extending types of ECL luminophores and absorptive chemodosimeters, based on an inner filter effect.
A feasible label-free electrochemiluminescence (ECL) aptasensor that uses an Au-nanoparticle-functionalized g-C 3 N 4 nanohybrid (Au-g-C 3 N 4 NH) as the luminophore was constructed for highly sensitive acetylcholinesterase (AChE) detection. The sensor was fabricated by successively modifying a glassy carbon electrode with Au-g-C 3 N 4 NH and thiol-modified AChE-specific aptamers. In the presence of AChE, the ECL signal decreased significantly, because AChE could hydrolyze the substrate acetylthiocholine to generate acetic acid, which could react with the co-reactant triethylamine (Et 3 N), leading to evident consumption of the coreactant. The ECL response of the aptasensor was linearly proportional to the concentration of AChE ranging from 0.1 pg/ mL to 10 ng/mL, with a detection limit of 42.3 fg/mL (S/N = 3). This novel ECL sensing strategy demonstrated a highly sensitive and selective method for AChE detection and was expected to possess potential applications in clinical diagnosis and biomedical technology.
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