Characterization of fatty acid coated polymer/nucleotide droplets

In protocell research, both coacervation and molecular self-assembly processes are used to design the protocell model due to their easiness formation of droplets under laboratory condition, involved with simple mixing of two or more polymers and compartmentalization properties owned by the droplets. In this research, droplets comprising poly-diallyldimethylammonium chloride (PDDA) and adenosine 5’triphosphate (ATP) in aqueous solutions were prepared via coacervation. The spontaneous formation of coacervate droplets was studied using changes in turbidity (UV-Vis), dynamic light scattering (DLS) and ζ-potentials measurement. Result showed that the droplets’ were formed when approximately 60% of fixed charges on polymer chain (polycationic) were neutralized by the nucleotide molecules (anionic). Nano-complexes were formed prior to droplet formation and droplets size was in nano-range. The droplets had low net positive charges and susceptible to coalescence. The self-assembly of FA molecules onto droplets’ surface was investigated using DLS, ζ-potentials and fluorescence microscope. Results showed that the FA coated droplets had high net negative charges suggesting that the coated droplets were more stable to coalescence. The presence of membrane dye (BODIPY FL-C16) at the surface of droplets suggesting the formation FA membrane. The addition of fatty acid FA molecules into the droplets aqueous solution successfully formed biological membrane (vesicle) that coated the droplets.