title: Artificial biomelanin: highly light-absorbing nano-sized eumelanin by biomimetic synthesis in chicken egg white.
abstract: The spontaneous oxidative polymerization of 0.01-1% w/w 5,6-dihydroxyindole (DHI) in chicken egg white (CEW) in the absence of added solvents leads to a black, water-soluble, and processable artificial biomelanin (ABM) with robust and 1 order of magnitude stronger broadband light absorption compared to natural and synthetic eumelanin suspensions. Small angle neutron scattering (SANS) and transmission electron microscopy (TEM) analysis indicated the presence in the ABM matrix of isolated eumelanin nanoparticles (≤100 nm) differing in shape from pure DHI melanin nanoparticles (SANS evidence). Electron paramagnetic resonance (EPR) spectra showed a slightly asymmetric signal (g ∼ 2.0035) similar to that of solid DHI melanin but with a smaller amplitude (ΔB), suggesting hindered spin delocalization in biomatrix. Enhanced light absorption, altered nanoparticle morphology and decreased free radical delocalization in ABM would reflect CEW-induced inhibition of eumelanin aggregation during polymerization accompanied in part by covalent binding of growing polymer to the proteins (SDS-PAGE evidence). The technological potential of eumelanin nanosizing by biomimetic synthesis within a CEW biomatrix is demonstrated by the preparation of an ABM-based black flexible film with characteristics comparable to those of commercially available polymers typically used in electronics and biomedical applications.
authors.affiliation: Department of Chemical Sciences, University of Naples "Federico II" , Via Cintia 4, 80126, Naples, Italy.
authors.forename: Nicola Fyodor
authors.initials: NF
authors.lastname: della Vecchia
authors.forename: Pierfrancesco
authors.initials: P
authors.lastname: Cerruti
authors.forename: Gennaro
authors.initials: G
authors.lastname: Gentile
authors.forename: Maria Emanuela
authors.initials: ME
authors.lastname: Errico
authors.forename: Veronica
authors.initials: V
authors.lastname: Ambrogi
authors.forename: Gerardino
authors.initials: G
authors.lastname: D'Errico
authors.forename: Sara
authors.initials: S
authors.lastname: Longobardi
authors.forename: Alessandra
authors.initials: A
authors.lastname: Napolitano
authors.forename: Luigi
authors.initials: L
authors.lastname: Paduano
authors.forename: Cosimo
authors.initials: C
authors.lastname: Carfagna
authors.forename: Marco
authors.initials: M
authors.lastname: d'Ischia
mesh_terms: D000818:Animals; D032701:Biomimetics / Q000379:methods; D002645:Chickens / Q000378:metabolism*; D004529:Egg White; D007211:Indoles / Q000737:chemistry / Q000378:metabolism; D008027:Light; D008543:Melanins / Q000737:chemistry* / Q000378:metabolism*; D053758:Nanoparticles / Q000737:chemistry* / Q000378:metabolism*; D010084:Oxidation-Reduction; D058105:Polymerization; D011108:Polymers / Q000737:chemistry / Q000378:metabolism; D053838:Scattering, Small Angle; D014867:Water / Q000737:chemistry
chemical_list: D007211:Indoles; D008543:Melanins; D011108:Polymers; D014867:Water; C041877:eumelanin; C033871:5,6-dihydroxyindole