When considering the effects of 1, 2, 4 and 5 on the membrane fluidity of the model synthetic vesicle systems, the squaramide based SSAs were shown to increase membrane rigidity to a far greater extent than the analogous thiourea based SSAs, 1 and 2 (Table ). As the proportion of PG present within the synthetic vesicle systems was increased, so was the propensity of 1, 2, 4 and 5 to increase membrane rigidity. However, the presence of increasing proportions of PE led to increased membrane fluidity upon the addition of 1, 2, 4 and 5. Coformulations c, d, f and g which contain both a thiourea based SSA (1, 2) and a squaramide based SSA (4, 5) increased the membrane rigidity of all synthetic vesicles tested, compared to the effects of adding 1 or 2 as single agents. Conversely, co-formulation a, which contained a combination of 1 and 2, caused a decrease in membrane rigidity for all synthetic membrane systems tested, compared to the effects of adding 1 or 2 as single agents. Therefore, through SSA co-formulation we have shown the ability to control the membrane fluidity properties for these synthetic vesicle systems. and Finally, in line with our previous work, we moved to characterise the membrane adhesion and permeation events of 1 -5 and co-formulations a -j with PE:PG 1:1 synthetic phospholipid vesicles. This vesicle composition was prioritised for further analysis as this composition acts as a model for an AMR resistant strain of the ESKAPE pathogen P. aeruginosa, categorised as high priority by the WHO. As summarised in Table , membrane permeation (PF) and membrane adhesion factors (MAF) for the SSA anionic components were calculated through the use of 1 H CPMG NMR spectroscopy experiments, using vesicles produced by extrusion through a 1000 µm polycarbonate membrane.