Accurate and facile differentiation of cell types is essential for accurate diagnosis and therapy of diseases. However, it remains challenging due to low specificity, requirement of sophisticated instruments, and tedious operation steps. Herein, a simple, washing- and label-free chemical tongue was constructed for differentiation of cell types. In the array-based sensing platform, DNA-ligand ensembles adsorbed on the surface of MnO 2 nanosheets were used as sensing probes. Instead of aptamers from cell-SELEX, the randomly designed DNA strands were used, offering versatile interactions with cells. The property that MnO 2 nanosheets can be degraded by intracellular glutathione makes the platform avoid the washing step. Eight types of cell lines were distinguished from each other after the data were treated with principal component analysis (PCA). In addition, a 95% of identification accuracy for the randomly selected unknown samples was achieved. The strategy shows an excellent performance not only in distinguishing cell lines but also in the identification of unknown cell samples.
Noble metal nanoparticles are promising materials for heterogeneous enantioselective catalysis because of their high surface-to-volume ratios, large concentrations of highly undercoordinated surface sites, and quantum confinement effects. In this work, we report on the use of DNA as an environment-responsive chiral ligand to engineer the selective catalytic behaviors of glucose oxidase-mimicking gold nanoparticles (AuNPs), with glucose enantiomers as the substrates. DNA can be stimulated externally to switch between random-coiled and multistranded structures (e.g., duplex, i-motif, or G-quadruplex). Random-coiled DNA-capped nanoparticles preferentially catalyze oxidation of l-glucose, and structured DNA-capped nanoparticles show higher activity toward d-glucose. pH-induced selectivity diminishment of DNA-treated AuNPs is also found, further demonstrating the chiral selector effect of DNA ligands. In the end, the selective catalysis of AuNPs allows control of the size enlargement of nanoparticles through self-catalytic Au0 deposition, in ligand- and substrate chirality-dependent manners. It is found that the effect of substrate chirality on the self-growth rate can be reversed by the hybridization of the capping DNA. The structural and chemical features of DNA grooves in the multistranded structures render binding sites with higher affinity to d-glucose than l-glucose. The results suggest a simple strategy for engineering the responsive enantioselective catalysis of metallic nanoparticles and advance the understanding of chiral interactions between nucleic acids and saccharide.
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