della Vecchia Nicola Fyodor, Cerruti Pierfrancesco, Gentile Gennaro, Errico Maria Emanuela, Ambrogi Veronica, D'Errico Gerardino, Longobardi Sara, Napolitano Alessandra, Paduano Luigi, Carfagna Cosimo, d'Ischia Marco
Department of Chemical Sciences, University of Naples "Federico II" , Via Cintia 4, 80126, Naples, Italy.
Biomacromolecules. 2014 Oct 13;15(10):3811-6. doi: 10.1021/bm501139h. Epub 2014 Sep 29.
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.
在不添加溶剂的情况下，0.01-1% w/w的5,6-二羟基吲哚（DHI）在鸡蛋白（CEW）中自发进行氧化聚合，生成一种黑色、水溶性且可加工的人工生物黑色素（ABM）。与天然和合成真黑素悬浮液相比，该ABM具有更强的宽带光吸收能力，强度高出一个数量级。小角中子散射（SANS）和透射电子显微镜（TEM）分析表明，ABM基质中存在孤立的真黑素纳米颗粒（≤100 nm），其形状与纯DHI黑色素纳米颗粒不同（SANS证据）。电子顺磁共振（EPR）光谱显示出一个略微不对称的信号（g ∼ 2.0035），与固态DHI黑色素的信号相似，但幅度较小（ΔB），这表明生物基质中自旋离域受到阻碍。ABM中增强的光吸收、改变的纳米颗粒形态以及自由基离域的减少，反映出CEW在聚合过程中对真黑素聚集的抑制作用，部分伴随着生长聚合物与蛋白质的共价结合（SDS-PAGE证据）。通过制备一种基于ABM的黑色柔性薄膜，展示了在CEW生物基质中通过仿生合成实现真黑素纳米尺寸化的技术潜力，该薄膜的特性与电子和生物医学应用中常用的市售聚合物相当。
