SEM image analysis provides information that the nanoparticles are formed within the first hour of the reaction, and there is no more change in particle size or yield after 3 h. As established in our stability study, at least 86 % of the prodrug monomer 2 is still intact after completion of the particle synthesis (see Table ). As our reference, we synthesize particles without prodrug from N-methylimidazole and 2,5-diiodo-N-methylimidazole (Ref); and to study the limits of drug loading, we prepare nanoparticles with different amounts of prodrug monomer 2 and different ratios of N-methylimidazole and 2,5-diiodo-N-methylimidazole (see P1, P2, and P6 in Table ).