Polyvinylpyrrolidone (PvP) Interaction with Biomembrane-Like Layers

Polvinylpyrrolidone (PvP) is a water soluble polymer made from the monomer N-vinylpyrrolidone (N-vP) and has extensive use in the synthesis and stabilisation of nanomaterials. Recently, this laboratory found that PvP interacted very strongly with the HISENTS biomembrane sensor, a response which is directly related to cell membrane damage by compounds. Comprehensive studies were therefore instigated to look at the effect of PvP on the HISENTS biomembrane sensor element. 5 lengths of PvP were investigated of monomer number (PvPm) from 31 to 11697 and dissolved in MilliQ water as stock solutions. Working solutions were prepared therefrom in phosphate buffered saline (PBS) at pH 7.4 and screened on the dioleoyl phosphatidylcholine (DOPC) sensor element. Interactions of PvP with the sensor element are shown as depressions of the two capacitance current peaks on the rapid cyclic voltammogram (1a). The limit of detection (LoD) metric of the PvP affinity for the sensor element is the lowest solution concentration of PvP, which can structurally modify the DOPC layer. Calibration curves are linear for low PvPm (31, 90) but Langmuirean for higher PvPm (495, 3239, 11697) indicating that PvP is adsorbing on and damaging the DOPC layer surface and structure. Plots of -log LoD versus PvPm show an increase corresponding to a greater interaction of the PvP with the DOPC layer with increasing length (1b). However a plot of (-log LoD)/PvPm versus PvPm gives a reciprocal relationship (1c) from which a realistic value of LoD for N-vP can be extracted. A plot of log (1/(PvPm x LoD)) versus PvPm shows a sharp decrease at low PvPm values and an increase at higher PvPm values (1d). If the physical nature of the PvP plays no role in the PvP interaction with DOPC, the value of log (1/(PvPm x LoD)) should remain constant (blue line in 1d). The reason for the decrease at low PvPm values is due to the decrease in entropy as the PvP chain moves from a 3D to a 2D environment. The increase in values at higher PvPm is caused by the increased self-assembly forces between the longer chains on the DOPC surface.

This work was funded by EU Horizon 2020: HISENTS GA: 685817 and SABYDOMA GA: 862296.