Huihui Yang,Jun Chen,Yuling Liang,Yanfei Zhang,Wen Yin,Yuzhi Xu,Si-Yang Liu,Zong Dai,Xiaoyong Zou
Dynamic imaging of cell surface pH is extremely challenging due to the slight changes in pH and the fast diffusion of secreted acid to the extracellular environment. In this work, we construct a novel metal–organic framework (MOF)-shell-confined i-motif-based pH probe (MOFC-i) strategy that enables sensitive and dynamic imaging of cell surface pH. The CY3- and CY5-labeled i-motif, which is hybridized via its short complementary chain with two-base mismatches, is optimized for sensing at physiological pH. After efficiently anchoring the optimized pH probes onto the cell membrane with the aid of cholesterol groups, a biocompatible microporous MOF shell is then formed around the cell by cross-linking ZIF-8 nanoparticles via tannic acid. The microporous MOF shell can confine secreted acid without inhibiting the normal physiological activities of cells; thus, the MOFC-i strategy can be used to monitor dynamic changes in the cell surface pH of living cells. Furthermore, this method can not only clearly distinguish the different metabolic behaviors of cancer cells and normal cells but also reveal drug effects on the cell surface pH or metabolism, providing promising prospects in pH-related diagnostics and drug screening.
A label-free, highly sensitive, and selective biosensor for detection of interleukin-6 (IL-6), which is an important inflammatory and cancer progression cytokine, has been achieved by combining gold nanoparticles (NPs) array surface-enhanced Raman spectroscopy (SERS) substrate and DNA aptamer. The SERS substrate consisted of Au NPs array is functionalized with the aptamer which is composed of the IL-6 recognition sequence and the output signal reporter. Upon recognition of target IL-6 in serum, the aptamer changes its conformation, resulting in the corresponding change of the output Raman intensity ratio (I 660 /I 736 ), with which the quantitative evaluation of IL-6 in 10 -12 -10 -7 M range can be realized. This SERS approach was employed to detect IL-6 in mice serum for inspecting the effect of drug and bacterial infection, and particularly, the radiation injury in the treated animals. This work therefore exemplifies that the aptamer-based SERS biosensor can serve as a promising tool for quick and convenient medical diagnosis applications.
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