Ratiometric Fluorescent Sensing of pH Values in Living Cells by Dual-Fluorophore-Labeled
i‑Motif Nanoprobes
- Publication date
- Publisher
Abstract
We
designed a new ratiometric fluorescent nanoprobe for sensing
pH values in living cells. Briefly, the nanoprobe consists of a gold
nanoparticle (AuNP), short single-stranded oligonucleotides, and dual-fluorophore-labeled
i-motif sequences. The short oligonucleotides are designed to bind
with the i-motif sequences and immobilized on the AuNP surface via
Au–S bond. At neutral pH, the dual fluorophores are separated,
resulting in very low fluorescence resonance energy transfer (FRET)
efficiency. At acidic pH, the i-motif strands
fold into a quadruplex structure and leave the AuNP, bringing the
dual fluorophores into close proximity, resulting in high FRET efficiency,
which could be used as a signal for pH sensing. The nanoprobe possesses
abilities of cellular transfection, enzymatic protection, fast response
and quantitative pH detection. The <i>in vitro</i> and intracellular
applications of the nanoprobe were demonstrated, which showed excellent
response in the physiological pH range. Furthermore, our experimental
results suggested that the nanoprobe showed excellent spatial and
temporal resolution in living cells. We think that the ratiometric
sensing strategy could potentially be applied to create a variety
of new multicolor sensors for intracellular detection