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I‑motif Formed at Physiological pH Triggered by Spatial Confinement of Nanochannels: An Electrochemical Platform for pH Monitoring in Brain Microdialysates
journal contribution
posted on 2020-02-25, 16:42 authored by Lu Shi, Feifei Cao, Limin Zhang, Yang TianThe
development of switches responding to specific pH changes was
particularly useful in wide application fields. Owing to flexible
switches simulated by pH, i-motif DNAs are widely used as a pH sensor.
But its character of structure transition strongly dependent on acidic
pH severely hampers the application of i-motif DNA in physiological
media. Herein, we report the stable i-motif structure formed at a
physiological pH triggered by spatial confinement of silica nanochannels.
Three classic DNA chains containing 21-mer i-motif domain base-pairs
and a single-stranded multiply (T)n spacer, 5′-COOH-(T)n-CCCTAACCCTAACCCTAACCC-3′, were employed to evaluate
the enhanced stability of i-motif structure. Compared to their free
states in a dilute solution, the transition pH of all i-motif DNAs
decorated in nanochannels remarkably shifts toward a neutral pH. Moreover,
the transition midpoint can be tuned sensitively over the physiologically
relevant pH range through slightly varying the length of T base spacer.
Density functional theory (DFT) calculations validate that the increased
proton density in a nanochannel triggers the formation of an i-motif
structure under a neutral pH. Finally, this i-motif DNA based nanochannels
electrode was successfully employed to monitor pH in brain microdialysates
followed by cerebral ischemia. The present approach is not limited
by fundamental investigation for DNA conformation but may extend toward
the manipulation of i-motif based structures for artificial molecular
machines and signaling systems.