Electrochemical tuning of the stability of PLL/DNA multilayers

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Abstract
The deposition and subsequent electrochemical dissolution of (PLL/DNA)6 films on ITO electrodes was studied by means of ecOWLS and in situAFM. ecOWLS experiments showed that (PLL/DNA)6 films fabricated at 0 V are stable in physiological buffer (pH 7.4) and that applying a potential above 1.8 V induces only a partial and slow dissolution. On the contrary, the dissolution is much more effective and quicker if a potential is applied already during the deposition of the film. AFM experiments showed that (PLL/DNA)6 films are constituted of 30 nm high, 100 nm diameter nanodroplets. The film morphology was not affected by the application of a potential during the fabrication. A custom made flow-cell allowed in situ following of the electrochemical dissolution revealing the continuous shrinking of the nanodroplets. The results were interpreted in the light of a model describing the variation of pH induced by the water electrolysis in the proximity of the ITO electrode.