We have previously confirmed SSAs to selectively interact, permeate and/or lyse phospholipid membranes of differing compositions, depending on the chemical composition of the anionic component of this amphiphilic salt. We have also shown an SSA to act as a potassium or sodium phospholipid membrane transport agent when working cooperatively with a known anionophore. These findings are further supported by a series of fluorescent live cell microscopy studies, in which intrinsically fluorescent SSAs can be observed forming spherical aggregates, which then interact with a target cell surface, morphing into a coating, and then permeating into the cell, enabling the entry of other molecules previously unable to gain cellular entry. To confirm selectivity of the SSA anionic component for the phosphate species contained within the phospholipid headgroups over other biologically relevant anionic species, a series of 1 H NMR spectroscopy titrations were performed in DMSO-d6 0.5 % H2O. Here H2PO4 -was used to represent the phosphate present in the phospholipid headgroup, while Cl -was incorporated into these studies as a common biologically relevant anion. However, these data should be treated with caution, due to the strength of the SSA anion self-association events present, see Table . In those instances where evidence of a hydrogen bonded SSA host:guest complex could be observed, the data was fitted to a 1:1 binding isotherm model using Bindfit v0.5 (Section S16 † ). Here, we obtained limited data supporting the formation of a 1:1 host:guest complex, with an enhanced strength of interaction noted for H2PO4 -over Cl -(e.g. TBACl:7 Kass = 0 M -1 ; TBAH2PO4:7 Kass = 30 M -1 ± 7.5 %).