Polyvinylpyrrolidone (PvP) adsorbs on and interacts with biomembrane-like layers

This communication describes an initial study into the interaction of solution polyvinylpyrrolidone (PvP) with electrode-supported monolayers of dioleoyl phosphatidylcholine (DOPC). Experiments were carried out in phosphate buffered saline (PBS) at pH 7.4, and solutions were screened on a DOPC-coated microfabricated Hg/Pt electrode in flow cell. The effect of the PvP interaction on the form of rapid cyclic voltammograms (RCV) was recorded at 40 Vs −1 . It was found that the PvP-DOPC interaction is strongly dependent on PvP chain length. For shorter chain lengths, the interaction is linearly related to PvP concentration whereas at longer chain lengths, the interaction is Langmuirean; however, the interaction RCV in all cases is representative of adsorption. Both the affinity constant, K 2 , and the limit of detection (LoD) are extracted from these plots, and these values are inversely related to each other. Plots of log K 2 and –log LoD versus the monomer segment number (PvP m ) fit a two-term equation consisting of a power term and an exponential term. Plots of (log K 2 )/PvP m versus PvP m are near reciprocal showing that there is ‘looping’ of the chains on the DOPC surface during the adsorption process. The results fit a model of entropically driven adsorption at short chain lengths and enthalpically driven adsorption at longer chain lengths the latter assumedly due to non-covalent interactions between the PvP chains on the DOPC surface.