Two consecutive steepest descent minimizations were performed to remove any undesirable steric artefacts. These energy minimizations were followed by a temperature equilibration simulation in the NVT ensemble (4 ns) at 303.15 K, using the leap-frog integrator with a 20 fs time step. The velocity-rescale thermostat was used, with separate thermostat groups assigned to the EEK molecules, PEG-PLGA polymers, ions and water molecules.