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Journal ArticleDOI

Melanins and melanogenesis: methods, standards, protocols

TL;DR: The aim of the paper was to define an unprecedented frame of reference built on cutting‐edge knowledge and state‐of‐the‐art methodology, to enable reliable comparison of results among laboratories and new progress in the field based on standardized methods and shared information.
Abstract: Despite considerable advances in the past decade, melanin research still suffers from the lack of universally accepted and shared nomenclature, methodologies, and structural models. This paper stems from the joint efforts of chemists, biochemists, physicists, biologists, and physicians with recognized and consolidated expertise in the field of melanins and melanogenesis, who critically reviewed and experimentally revisited methods, standards, and protocols to provide for the first time a consensus set of recommended procedures to be adopted and shared by researchers involved in pigment cell research. The aim of the paper was to define an unprecedented frame of reference built on cutting-edge knowledge and state-of-the-art methodology, to enable reliable comparison of results among laboratories and new progress in the field based on standardized methods and shared information.
Citations
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Journal ArticleDOI
TL;DR: Rational tailoring strategies directed to critical control points of the synthetic pathways, such as dopaquinone, DAquinone, and dopachrome are proposed, with a view to translating basic chemical knowledge into practical guidelines for material manipulation and tailoring.
Abstract: ConspectusPolydopamine (PDA), a black insoluble biopolymer produced by autoxidation of the catecholamine neurotransmitter dopamine (DA), and synthetic eumelanin polymers modeled to the black functional pigments of human skin, hair, and eyes have burst into the scene of materials science as versatile bioinspired functional systems for a very broad range of applications. PDA is characterized by extraordinary adhesion properties providing efficient and universal surface coating for diverse settings that include drug delivery, microfluidic systems, and water-treatment devices. Synthetic eumelanins from dopa or 5,6-dihydroxyindoles are the focus of increasing interest as UV-absorbing agents, antioxidants, free radical scavengers, and water-dependent hybrid electronic–ionic semiconductors. Because of their peculiar physicochemical properties, eumelanins and PDA hold considerable promise in nanomedicine and bioelectronics, as they are biocompatible, biodegradable, and exhibit suitable mechanical properties for i...

470 citations

Journal ArticleDOI
TL;DR: Considering the above issues, age‐related accumulation of neuromelanin in dopamine neurons shows an interesting link between aging and neurodegeneration.

454 citations


Cites background or methods from "Melanins and melanogenesis: methods..."

  • ...…melanogenesis by an international group of experts, melanins are ubiquitous pigments of diverse structure and origin derived by the oxidation and polymerization of tyrosine, or related compounds, in animals or phenolic compounds in lower organisms (d’Ischia et al., 2013; Wakamatsu and Ito, 2002)....

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  • ...…EPR spectroscopy, nuclear magnetic resonance spectroscopy, X-ray diffraction, mass spectrometry and advanced quantum chemical calculations were used, seem to support a stacked-aggregate model of the eumelanin structure (d’Ischia et al., 2013; Meredith and Sarna, 2006; Zajac et al., 1994)....

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  • ...The least studied melanins, the pyomelanins, are dark pigments produced mainly by microorganisms from homogentisate (d’Ischia et al., 2013)....

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  • ...In some cases, also hydrogen peroxide has been used, but an excess of peroxide could degrade the forming melanin (d’Ischia et al., 2013)....

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  • ...Results of numerous studies, carried out on synthetic and natural eumelanins, in which atomic force microscopy, EPR spectroscopy, nuclear magnetic resonance spectroscopy, X-ray diffraction, mass spectrometry and advanced quantum chemical calculations were used, seem to support a stacked-aggregate model of the eumelanin structure (d’Ischia et al., 2013; Meredith and Sarna, 2006; Zajac et al., 1994)....

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Journal ArticleDOI
20 Feb 2015-Science
TL;DR: Melanin may be carcinogenic as well as protective against cancer, and validate the long-standing suggestion that chemically generated excited electronic states are relevant to mammalian biology.
Abstract: Mutations in sunlight-induced melanoma arise from cyclobutane pyrimidine dimers (CPDs), DNA photoproducts that are typically created picoseconds after an ultraviolet (UV) photon is absorbed at thymine or cytosine. We found that in melanocytes, CPDs are generated for >3 hours after exposure to UVA, a major component of the radiation in sunlight and in tanning beds. These "dark CPDs" constitute the majority of CPDs and include the cytosine-containing CPDs that initiate UV-signature C→T mutations. Dark CPDs arise when UV-induced reactive oxygen and nitrogen species combine to excite an electron in fragments of the pigment melanin. This creates a quantum triplet state that has the energy of a UV photon but induces CPDs by energy transfer to DNA in a radiation-independent manner. Melanin may thus be carcinogenic as well as protective against cancer. These findings also validate the long-standing suggestion that chemically generated excited electronic states are relevant to mammalian biology.

391 citations

Journal ArticleDOI
TL;DR: All melanins show a common feature, a protective role, but they are not merely photoprotective pigments against UV sunlight; in pathogenic microorganisms, melanization becomes a virulence factor since melanin protects microbial cells from defense mechanisms in the infected host.
Abstract: This review presents a general view of all types of melanin in all types of organisms. Melanin is frequently considered just an animal cutaneous pigment and is treated separately from similar fungal or bacterial pigments. Similarities concerning the phenol precursors and common patterns in the formation routes are discussed. All melanins are formed in a first enzymatically-controlled phase, generally a phenolase, and a second phase characterized by an uncontrolled polymerization of the oxidized intermediates. In that second phase, quinones derived from phenol oxidation play a crucial role. Concerning functions, all melanins show a common feature, a protective role, but they are not merely photoprotective pigments against UV sunlight. In pathogenic microorganisms, melanization becomes a virulence factor since melanin protects microbial cells from defense mechanisms in the infected host. In turn, some melanins are formed in tissues where sunlight radiation is not a potential threat. Then, their redox, metal chelating, or free radical scavenging properties are more important than light absorption capacity. These pigments sometimes behave as a double-edged sword, and inhibition of melanogenesis is desirable in different cells. Melanin biochemistry is an active field of research from dermatological, biomedical, cosmetical, and microbiological points of view, as well as fruit technology.

373 citations


Cites background from "Melanins and melanogenesis: methods..."

  • ...There are detailed and updated reviews about HPLC quantitation, structure of those fragments, and their utility as markers for qualitative and quantitative melanin determination [10, 27, 28]....

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  • ...Regarding this concept, other bacterial species have no polyphenol oxidase but are able to form a yellowish pigment that is also named pyomelanin [8, 10, 124]....

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Journal ArticleDOI
TL;DR: An interdisciplinary perspective of melanin pigments and related pathway is provided with a view to showing how it is possible to translate current knowledge about physical and chemical properties and control mechanisms into new bioinspired solutions for biomedical, dermocosmetic, and technological applications.
Abstract: During the past decade, melanins and melanogenesis have attracted growing interest for a broad range of biomedical and technological applications. The burst of polydopamine-based multifunctional coatings in materials science is just one example, and the list may be expanded to include melanin thin films for organic electronics and bioelectronics, drug delivery systems, functional nanoparticles and biointerfaces, sunscreens, environmental remediation devices. Despite considerable advances, applied research on melanins and melanogenesis is still far from being mature. A closer intersectoral interaction between research centers is essential to raise the interests and increase the awareness of the biomedical, biomaterials science and hi-tech sectors of the manifold opportunities offered by pigment cells and related metabolic pathways. Starting from a survey of biological roles and functions, the present review aims at providing an interdisciplinary perspective of melanin pigments and related pathway with a view to showing how it is possible to translate current knowledge about physical and chemical properties and control mechanisms into new bioinspired solutions for biomedical, dermocosmetic, and technological applications.

328 citations

References
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Journal ArticleDOI
19 Oct 2007-Science
TL;DR: Inspired by the composition of adhesive proteins in mussels, dopamine self-polymerization is used to form thin, surface-adherent polydopamine films onto a wide range of inorganic and organic materials, including noble metals, oxides, polymers, semiconductors, and ceramics.
Abstract: We report a method to form multifunctional polymer coatings through simple dip-coating of objects in an aqueous solution of dopamine. Inspired by the composition of adhesive proteins in mussels, we used dopamine self-polymerization to form thin, surface-adherent polydopamine films onto a wide range of inorganic and organic materials, including noble metals, oxides, polymers, semiconductors, and ceramics. Secondary reactions can be used to create a variety of ad-layers, including self-assembled monolayers through deposition of long-chain molecular building blocks, metal films by electroless metallization, and bioinert and bioactive surfaces via grafting of macromolecules.

8,669 citations


"Melanins and melanogenesis: methods..." refers methods in this paper

  • ...Oxidation of dopamine, originally investigated as a model approach to neuromelanin, has recently become popular as a method for preparing a dark eumelanin-like material known as polydopamine, with extraordinary adhesion and coating properties (Lee et al., 2007)....

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Journal ArticleDOI
TL;DR: A full understanding of melanin function, and indeed its role in retarding or promoting the disease state, can only be obtained through a full mapping of key structure-property relationships in the main pigment types.
Abstract: In this article, we review the current state of knowledge concerning the physical and chemical properties of the eumelanin pigment. We examine properties related to its photoprotective functionality, and draw the crucial link between fundamental molecular structure and observable macroscopic behaviour. Where necessary, we also briefly review certain aspects of the pheomelanin literature to draw relevant comparison. A full understanding of melanin function, and indeed its role in retarding or promoting the disease state, can only be obtained through a full mapping of key structure-property relationships in the main pigment types. We are engaged in such an endeavor for the case of eumelanin.

860 citations


"Melanins and melanogenesis: methods..." refers background in this paper

  • ...Because eumelanin is a good chelator of multivalent transition metal ions (Meredith and Sarna, 2006) and metal ions bound to eumelanin can modulate the intensity of the observable EPR signal of melanin radicals (Sarna et al., 1976), quantitative determination of eumelanin by EPR spectroscopy may…...

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Book
01 Jan 1992
TL;DR: An introduction to melanin research melanin producing cells tyrosinase natural and synthetic melanins eumelanins neuromelanin pheomelAnins and trichochromes pigment cell metabolism - enzymatic and chemical control.
Abstract: An introduction to melanin research melanin producing cells tyrosinase natural and synthetic melanins eumelanins neuromelanin pheomelanins and trichochromes pigment cell metabolism - enzymatic and chemical control genetic and hormonal regulation of melanogenesis photobiology and photochemistry of melanogenesis.

617 citations

Journal ArticleDOI
TL;DR: The latest advances in the field are reviewed to show how the emerging knowledge is not only helping to explain eumelanin functionality, but may also be translated into effective strategies for exploiting their properties to create a new class of biologically inspired high-tech materials.
Abstract: Eumelanins, the characteristic black, insoluble, and heterogeneous biopolymers of human skin, hair, and eyes, have intrigued and challenged generations of chemists, physicists, and biologists because of their unique structural and optoelectronic properties. Recently, the methods of organic chemistry have been combined with advanced spectroscopic and imaging techniques, theoretical calculations, and methods of condensed-matter physics to gradually force these materials to reveal their secrets. Herein we review the latest advances in the field with a view to showing how the emerging knowledge is not only helping to explain eumelanin functionality, but may also be translated into effective strategies for exploiting their properties to create a new class of biologically inspired high-tech materials.

506 citations


"Melanins and melanogenesis: methods..." refers background in this paper

  • ...…characterization A detailed understanding of the optical, electrical, and microstructural properties of melanin not only provides another tool to define and identify melanins, but also opens the intriguing possibility of melanin bioelectronics (Bothma et al., 2008; d’Ischia et al., 2009)....

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Journal ArticleDOI
TL;DR: The proper selection of substrate concentration and buffer is proposed as a practical means of tailoring polydopamine functionality via control of competing pathways downstream of dopamine quinone.
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 quinone.

466 citations


"Melanins and melanogenesis: methods..." refers background in this paper

  • ...Commonly used protocols for the preparation of polydopamine or dopamine melanin are based on prolonged aerial oxidation of the catecholamine (10 mM) in Tris or other buffers at pH 8.5 leading to black insoluble materials (Della Vecchia et al., 2013)....

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  • ...It has been shown to consist of both cyclized (DHI) and uncyclized units in variable proportions depending on the mode of preparation (Della Vecchia et al., 2013) and is therefore different from pure DHImelanin in that it contains non-cyclized catecholamine units....

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