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, K2, and the limit of detection (LoD) are extracted from these plots, and these values are inversely related to each other. Plots of log K2 and –log LoD versus the monomer segment number (PvPm) fit a two-term equation consisting of a power term and an exponential term. Plots of (log K2)/PvPm versus PvPm 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.