Multiscale Simulation Study of Synthetic Melanin Nanoparticle Self-Assembly

Self-assembled melanin-containing structures are leveraged by multiple organisms to create so-called structural colors; these biomaterials exhibit tunable color and iridescence based on the ordering and spacing of the melanin-containing assemblies. Recent work has demonstrated similar structural colors in micron-sized supraballs created using reverse emulsion assembly of ~100 nm polydopamine nanoparticles [Xiao et al. Sci. Adv. 2017, 3 (9), e1701151]. However, the supraball structure at multiple lengthscales (nm to micron), and how these structures can be controllably tuned to obtain a specific color response, remains unclear. In this poster, we describe our multiscale molecular dynamics simulation approach to explore a wide parameter space of nanoparticle chemistries, sizes, and emulsion assembly conditions and study their effects on the supraball structure. We use atomistic simulations to understand molecule-level structure and interactions between synthetic melanin monomers and common reverse emulsion solvents (water, octanol). These results inform nm-scale coarse-grained simulations to explore interactions between nanoparticles and the boundary of the emulsion droplet, which then parameterize ultra-coarse-grained simulations that mimic the micron-scale supraball assembly.