Characterization and application of controllable local chemical changes produced by reagent delivery from a nanopipet.
We introduce a versatile method that allows local and repeatable delivery (or depletion) of any water-soluble reagent from a nanopipet in ionic solution to make localized controlled changes in reagent concentration at a surface. In this work, Na(+) or OH(-) ions were dosed from the pipet using pulsed voltage-driven delivery. Total internal reflection fluorescence from CoroNa Green dye in the bath for Na(+) ions or fluorescein in the bath for pH quantified the resulting changes in local surface concentration. These changes had a time response as short as 10 ms and a radius of 1-30 microm and depended on the diameter of the pipet used, the applied voltage, and the pipet-surface separation. After the pipet dosing was characterized in detail, two proof-of-concept experiments on single cells and single molecules were then performed. We demonstrated local control of the sodium-sensitive flagellar motor in single Escherichia coli chimera on the time scale of 1 s by dosing sodium and monitoring the rotation of a 1 microm diameter bead fixed to the flagellum. We also demonstrated triggered single-molecule unfolding by dosing acid from the pipet to locally melt individual molecules of duplex DNA, as observed using fluorescent resonance energy transfer.
Piper
Joe D
JD
Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.
Li
Chao
C
Lo
Chien-Jung
CJ
Berry
Richard
R
Korchev
Yuri
Y
Ying
Liming
L
Klenerman
David
D
D000143:Acids; D000468:Alkalies; D035843:Biomedical Research / Q000295:instrumentation / Q000379:methods*; D004247:DNA; D004926:Escherichia coli / Q000737:chemistry; D005407:Flagella; D031541:Fluorescence Resonance Energy Transfer; D005456:Fluorescent Dyes; D012964:Sodium; D017186:Titrimetry; D014894:Weights and Measures
D000143:Acids; D000468:Alkalies; D005456:Fluorescent Dyes; D004247:DNA; D012964:Sodium