Imaging Endogenous Metal Ions in Living Cells Using a DNAzyme–Catalytic Hairpin Assembly Probe

Abstract

DNAzymes have been shown as a promising platform for metal ions detection and a few DNAzyme-based sensors have been reported to detect metal ions inside cells. However, these methods required an influx of metal ions to increase their concentrations for detection. To address this major issue, we herein report the design of a catalytic hairpin assembly (CHA) reaction to amplify the signal from photocaged Na+-specific DNAzyme to detect endogenous Na+ inside cells. Upon light activation and in the presence of Na+, NaA43 DNAzymes cleave the substrate strands and release initiator DNA that trigger the followed CHA amplification reaction. This strategy has allowed detection of endogenous Na+ inside cells, which has been demonstrated by both fluorescent imaging of individual cells and flow cytometry of the whole cell population. This method can be generally applied to detect other endogenous metal ions and thus contribute to deeper understanding of the role of metal ions in biological systems.

Nucleic‐Acid Structures as Intracellular Probes for Live Cells

“…The ribonucleotide adenosine site in the substrate strand was protected by photocleavable 2′‐O‐nitrobenzyl protection group to enable controlled activation of the DNAzyme after probe internalization. Later, Wu et al developed a catalytic hairpin assembly‐based strategy for amplification of signal coming from Na + ‐specific activity of the NaA43 DNAzyme …”

Target Self‐Enhanced Selectivity in Metal‐Specific DNAzymes

“…[6][7][8][9] DNAzymes are single-stranded catalytic DNA sequences. Most DNAzymes require polyvalent metal ions for activity, and they have been intentionally evolved for metal detection [10][11][12][13][14][15][16] and intracellular RNA cleavage. [17] So far, RNAcleaving DNAzymes with excellent selectivity for metals such as Pb 2+ , [18,19] Ca 2+ , [20] UO 2 2+ ions, [21,22] and lanthanides have been isolated.…”

Light‐Activated Nanoprobes for Biosensing and Imaging

“…Lu's group has demonstrated appealing applications of light‐activated DNAzymes for metal ion sensing in living cells . By replacing the normal adenosine at the cleavage site of the substrate strand with a photocaged adenosine (2′‐O‐nitrobenzyl adenosine), they could render the DNAzyme inactive and prevent binding with metal ions during cellular delivery.…”