a spray dryer to produce nanoparticles using the conditions specified in table 1 a b u00fcchi mini spray dryer model b 290 b u00fcchi lab switzerland with a standard nozzle 0 7 mm diameter was used to produce the dry powders of the various formulations the conditions used are compiled in table 1 the spray dryer was provided with a high performance cyclone designed to get an excellent recovery of the material in the receiver vessel and reduce the adhesion of the product on the wall of the drying chamber particle size and particle size distributions were measured by dynamic laser scattering or photon correlation spectroscopy using a malvern zetasizer nano zs malvern instruments ltd uk for each sample 3 5 mg of spray dried powder were prepared by suspending the particles in filtered water 0 2 u03bcm filter vortexing and or sonicating for 2 min if necessary each sample was measured in triplicate the zeta potential of the particles was measured using the zetasizer nano zs malvern instruments ltd uk for that a sample of 3 mg of the spray dried nanoparticles was suspended in 1 2 ml of de ionised water and then vortexed or sonicated before the measurement each measurement was.