Self-colored nanoparticles containing naphthalene-bisimide derivatives: Synthesis and protein adsorption study

An approach to covalently bound the novel polymerizable dyes, 2,3,6,7-tetrathienyl-1,4,5,8-naphthalenetetracarboxylic-N,N′-di(2-methylallyl)-bisimide (ALN4T) and 2,3,6,7-tetra(2,2′-bithiophene)-1,4,5,8-naphthalenetetracarboxylic-N,N′-di(2-methylallyl)-bisimide (ALN8T), and vinyl monomers for tailoring the self-colored nanoparticles (NPs) was demonstrated. Using the miniemulsion polymerization technique, the NPs with high conversion were synthesized. Examining the particles by scanning electron micrograph (SEM) revealed a uniform size distribution. UV/vis spectroscopy results showed that the colored NPs comprising of ALN4T exhibited the same absorption maxima compared to that of the parent dye, while a hypsochromic shift was observed when using ALN8T. By using bovine serum albumin (BSA) as a model, the amount of protein adsorption (Γads) onto the surface of the colored NPs was evaluated. The Γads on the colored NPs was found to be dictated by synergistic effects of the conformation change of BSA at a given pH and the electrostatic interaction between the protein and the particle surface. The good colloidal stability of the NPs after BSA adsorption was observed by zeta potential measurement. Therefore, the prepared self-colored NPs have potential application in biomedical areas.