Building‐Block Diversity in Polydopamine Underpins a Multifunctional Eumelanin‐Type Platform Tunable Through a Quinone Control Point

Abstract

Rational approaches to engineering polydopamine films with tailored properties for surface coating and functionalization are currently challenged by the lack of detailed information about the polymer structure and the mechanism of buildup. Using an integrated chemical and spectroscopic approach enables the demonstration of: a) a three-component structure of polydopamine, comprising uncyclized (catecholamine) and cyclized (indole) units, as well as novel pyrrolecarboxylic acid moieties; b) remarkable variations in the relative proportions of the cyclized and uncyclized units with starting dopamine concentration; c) the occurrence of oligomer components up to the tetramer level; d) the covalent incorporation of Tris buffer; and e) the role of dopamine quinone as a crucial control point for directing the buildup pathways and tuning the properties. The importance of the uncyclized amine-containing units in polydopamine adhesion is also highlighted. The proper selection of substrate concentration and buffer is thus proposed as a practical means of tailoring polydopamine functionality via control of competing pathways downstream of dopamine quinon

Purification and characterisation of a sulphur rich melanin from edible mushroom Termitomyces albuminosus Heim

“…TAliphatic amine structural elements are proposed to arise in 13 C NMR spectrum from coupling of dopamine/quinone structural units which are unique to dopamine melanins (Della Vecchia et al 2013; Chatterjee et al 2014). Tian et al (2003) reported that carbon-near sulphur shows chemical shift at 45–40 ppm and CH 2 carbon–CH 2 –CH(NH 2 )–COOH of tyrosine/DOPA can also be seen around 40–35 ppm in 13 C NMR spectrum which is consistent with our sulphur-containing melanin claim.…”

Solid-state NMR Reveals the Carbon-based Molecular Architecture of Cryptococcus neoformans Fungal Eumelanins in the Cell Wall

“…To date, the eumelanin structural arrangements for indole-based aromatics, cell wall-derived polysaccharide components, and associated "lipid-like" aliphatic moieties have been deduced partially and indirectly from chemical shift trends observed in cross-polarization magic-angle spinning (CPMAS) 3 NMR experiments on intact solid samples or bonded spin-spin interactions observed by high resolution MAS of the aliphatic fraction of the pigment-cell wall assembly that is capable of swelling (8, 19 -21). Although the major 5,6-dihydroxyindole and 5,6-dihydroxyindole-2-carboxylic acid building blocks have been deduced by chemical analysis of degraded melanins (1,22,23), key architectural questions regarding the aromatic core of the intact pigment produced in cell-free or fungal systems have just begun to be addressed (24).…”

Turn-on Fluorescent Dopamine Sensing Based on in Situ Formation of Visible Light Emitting Polydopamine Nanoparticles

“…23−25 The resulting polymer is commonly referred to as polydopamine (PDA), which is structurally very similar to the natural eumelanin polymers. 26 Although, the fluorescence property of eumelanins is known for more than 40 years and there is ongoing research to understand the interesting optical properties of these materials; 27−29 the fluorescence of PDA is largely unexplored. To our knowledge, only very recently Zhang et al 30 reported that purified PDA nanoparticles are fluorescent and can be used for cellular imaging.…”