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Alessandro Pezzella - One of the best experts on this subject based on the ideXlab platform.
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silver nanoparticles as plasmon resonant enhancers for Eumelanin s photoacoustic signal in a self structured hybrid nanoprobe
Materials Science and Engineering: C, 2019Co-Authors: Brigida Silvestri, Alessandro Pezzella, Giuseppe Vitiello, Paolo Armanetti, Gennaro Sanita, Annalisa Lamberti, Gaetano Cali, Giuseppina Luciani, Luca Menichetti, Stefano LuinAbstract:Developing safe and high efficiency contrast tools is an urgent need to allow in vivo applications of photoacoustics (PA), an emerging biomolecular imaging methodology, with poor invasiveness, deep penetration, high spatial resolution and excellent endogenous contrast. Eumelanins hold huge promise as biocompatible, endogenous photoacoustic contrast agents. However, their huge potential is still unexplored due to the difficulty to achieve at the same time poor aggregation in physiologic environment and high PA contrast. This study addresses both issues through the design of a biocompatible photoacoustic nanoprobe, named MelaSil_Ag-NPs, relying on silica-templated Eumelanin formation as well as Eumelanins redox and metal chelating properties to reduce Ag+ ions and control the growth of generated metal nanoparticles. This strategy allowed self-structuring of the system into a core-shell architecture, where the Ag core was found to boost PA signal, despite the poor Eumelanin content. Obtained hybrid nanoplatforms, showed stable photoacoustic properties even under long irradiation. Furthermore, conjugation with rhodamine isothiocyanate allowed particles detection through fluorescent imaging proving their multifunctional potentialities. In addition, they were stable towards aggregation and efficiently endocytosed by human pancreatic cancer cells (BxPC3 and Panc-1) displaying no significant cytotoxicity. Such numerous features prove huge potential of those nanoparticles as a multifunctional platform for biomedical applications.
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On the antioxidant activity of Eumelanin biopigments: a quantitative comparison between free radical scavenging and redox properties
2019Co-Authors: Teresa Cecchi, Eduardo Di Mauro, Alessandro Pezzella, Samuel Cestola, David Ginsburg, Mattia Luzi, Alessandro Rigucci, Clara SantatoAbstract:The antioxidant activity of Eumelanin, a ubiquitous pigment in flora and fauna, constitutes one of its most fascinating physicochemical properties. To shed light on free radical scavenging vs redox facets of such activity, we applied hydrogen atom transfer- and electron transfer-based assays to pristine Sepia ink, Eumelanin from Sepia ink, chemically controlled Eumelanins and their precursor building blocks. Our work contributes to the rational use of the antioxidant properties of Eumelanin for health, cosmetics and environmental applications.
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Data_Sheet_1_Evidence of Unprecedented High Electronic Conductivity in Mammalian Pigment Based Eumelanin Thin Films After Thermal Annealing in Vacuum.docx
2019Co-Authors: Ludovico Migliaccio, Paola Manini, Carla Minarini, Paolo Tassini, Maria Grazia Maglione, Davide Altamura, Cinzia Giannini, Alessandro PezzellaAbstract:Melanin denotes a variety of mammalian pigments, including the dark electrically conductive Eumelanin and the reddish, sulfur-containing, pheomelanin. Organic (bio)electronics is showing increasing interests in Eumelanin exploitation, e.g., for bio-interfaces, but the low conductivity of the material is limiting the development of Eumelanin-based devices. Here, for the first time, we report an abrupt increase of the Eumelanin electrical conductivity, revealing the highest value presented to date of 318 S/cm. This result, obtained via simple thermal annealing in vacuum of the material, designed on the base of the knowledge of the Eumelanin chemical properties, also discloses the actual electronic nature of this material's conduction.
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bioinspired hybrid Eumelanin tio2 antimicrobial nanostructures the key role of organo inorganic frameworks in tuning Eumelanin s biocide action mechanism through membrane interaction
RSC Advances, 2018Co-Authors: Giuseppe Vitiello, Alessandro Pezzella, Anna Zanfardino, Olimpia Tammaro, Michela Di Napoli, Maria Federica Caso, Mario Varcamonti, Brigida Silvestri, Gerardino Derrico, Aniello CostantiniAbstract:Intrinsic biocide efficacy of Eumelanins can be markedly enhanced through a templated formation in the presence of a TiO2-sol, leading to hybrid TiO2–melanin nanostructures. However, mechanisms and processes behind biocide activity still remain poorly understood. This paper discloses the fundamental mechanism of action of these systems providing mechanistic information on their peculiar interaction with Escherichia coli strains. To this purpose biocide characterization is combined with Electron Paramagnetic Resonance (EPR) spectroscopy to investigate radical species produced by the hybrids as well as their interactions with Gram(−) external bacterial membranes. Experimental results indicate that TiO2 mediated Eumelanin polymerization leads to a peculiar mechanism of action of hybrid nanostructures, whose strong interactions with bacterial membranes enhance the action of reactive oxygen species (ROS) produced by Eumelanin degradation itself, also concurring with the final biocide action. These findings provide strategic information for the development of Eumelanin-based systems with enhanced activity against drug-resistant strains.
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Bioinspired hybrid Eumelanin–TiO2 antimicrobial nanostructures: the key role of organo–inorganic frameworks in tuning Eumelanin's biocide action mechanism through membrane interaction
RSC Advances, 2018Co-Authors: Giuseppe Vitiello, Alessandro Pezzella, Anna Zanfardino, Olimpia Tammaro, Michela Di Napoli, Maria Federica Caso, Mario Varcamonti, Brigida Silvestri, Gerardino D'errico, Aniello CostantiniAbstract:Intrinsic biocide efficacy of Eumelanins can be markedly enhanced through a templated formation in the presence of a TiO2-sol, leading to hybrid TiO2–melanin nanostructures. However, mechanisms and processes behind biocide activity still remain poorly understood. This paper discloses the fundamental mechanism of action of these systems providing mechanistic information on their peculiar interaction with Escherichia coli strains. To this purpose biocide characterization is combined with Electron Paramagnetic Resonance (EPR) spectroscopy to investigate radical species produced by the hybrids as well as their interactions with Gram(−) external bacterial membranes. Experimental results indicate that TiO2 mediated Eumelanin polymerization leads to a peculiar mechanism of action of hybrid nanostructures, whose strong interactions with bacterial membranes enhance the action of reactive oxygen species (ROS) produced by Eumelanin degradation itself, also concurring with the final biocide action. These findings provide strategic information for the development of Eumelanin-based systems with enhanced activity against drug-resistant strains.
Alessandra Napolitano - One of the best experts on this subject based on the ideXlab platform.
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Eumelanin broadband absorption develops from aggregation modulated chromophore interactions under structural and redox control
Scientific Reports, 2017Co-Authors: Raffaella Micillo, Kenzo Koike, Lucia Panzella, Alessandra Napolitano, Mariagrazia Iacomino, Giacomo Prampolini, Ivo Cacelli, Alessandro Ferretti, Orlando Crescenzi, Marco DischiaAbstract:Eumelanins, the chief photoprotective pigments in man and mammals, owe their black color to an unusual broadband absorption spectrum whose origin is still a conundrum. Excitonic effects from the interplay of geometric order and disorder in 5,6-dihydroxyindole (DHI)-based oligomeric/polymeric structures play a central role, however the contributions of structural (scaffold-controlled) and redox (π-electron-controlled) disorder have remained uncharted. Herein, we report an integrated experimental-theoretical entry to Eumelanin chromophore dynamics based on poly(vinyl alcohol)-controlled polymerization of a large set of 5,6-dihydroxyindoles and related dimers. The results a) uncover the impact of the structural scaffold on Eumelanin optical properties, disproving the widespread assumption of a universal monotonic chromophore; b) delineate Eumelanin chromophore buildup as a three-step dynamic process involving the rapid generation of oxidized oligomers, termed melanochromes (phase I), followed by a slow oxidant-independent band broadening (phase II) leading eventually to scattering (phase III); c) point to a slow reorganization-stabilization of melanochromes via intermolecular redox interactions as the main determinant of visible broadband absorption.
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Fifty Shades" of Black and Red or How Carboxyl Groups Fine Tune Eumelanin and Pheomelanin Properties.
International Journal of Molecular Sciences, 2016Co-Authors: Raffaella Micillo, Kenzo Koike, Giuseppe Monfrecola, Lucia Panzella, Alessandra Napolitano, Marco D'ischiaAbstract:Recent advances in the chemistry of melanins have begun to disclose a number of important structure-property-function relationships of crucial relevance to the biological role of human pigments, including skin (photo) protection and UV-susceptibility. Even slight variations in the monomer composition of black Eumelanins and red pheomelanins have been shown to determine significant differences in light absorption, antioxidant, paramagnetic and redox behavior, particle morphology, surface properties, metal chelation and resistance to photo-oxidative wear-and-tear. These variations are primarily governed by the extent of decarboxylation at critical branching points of the Eumelanin and pheomelanin pathways, namely the rearrangement of dopachrome to 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA), and the rearrangement of 5-S-cysteinyldopa o-quinoneimine to 1,4-benzothiazine (BTZ) and its 3-carboxylic acid (BTZCA). In Eumelanins, the DHICA-to-DHI ratio markedly affects the overall antioxidant and paramagnetic properties of the resulting pigments. In particular, a higher content in DHICA decreases visible light absorption and paramagnetic response relative to DHI-based melanins, but markedly enhances antioxidant properties. In pheomelanins, likewise, BTZCA-related units, prevalently formed in the presence of zinc ions, appear to confer pronounced visible and ultraviolet A (UVA) absorption features, accounting for light-dependent reactive oxygen species (ROS) production, whereas non-carboxylated benzothiazine intermediates seem to be more effective in inducing ROS production by redox cycling mechanisms in the dark. The possible biological and functional significance of carboxyl retention in the Eumelanin and pheomelanin pathways is discussed.
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Polydopamine and Eumelanin: From Structure–Property Relationships to a Unified Tailoring Strategy
Accounts of Chemical Research, 2014Co-Authors: Marco D'ischia, Vincent Ball, Chun-teh Chen, Alessandra Napolitano, Markus J. BuehlerAbstract: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...
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Polydopamine and Eumelanin: from structure-property relationships to a unified tailoring strategy
Accounts of chemical research, 2014Co-Authors: Marco D'ischia, Vincent Ball, Chun-teh Chen, Alessandra Napolitano, Markus J. BuehlerAbstract: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...
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Engineering polydopamine films with tailored behaviour for next-generation Eumelanin-related hybrid devices
J. Mater. Chem. C, 2013Co-Authors: Marianna Ambrico, Alessandra Napolitano, Antonio Cardone, Teresa Ligonzo, Vincenzo Augelli, Paolo F. Ambrico, Stefania R Cicco, Nicola Fyodor Della Vecchia, Maurizio Mastropasqua Talamo, Gianluca M FarinolaAbstract:Eumelanin-type biopolymers have attracted growing interest in the quest for soft bioinspired functional materials for application in organoelectronics. Recently, a metal-insulator-semiconductor device with a good quality interface was produced by spin coating of a commercial synthetic Eumelanin-like material on a dry plasma-modified silicon surface. As a proof-of-concept step toward the design and implementation of next-generation Eumelanin-inspired devices, we report herein an expedient chemical strategy to bestow n-type performance to polydopamine, a highly popular Eumelanin-related biopolymer with intrinsic semiconductor behaviour, and to tune its electrical properties. The strategy relies on aerial co-oxidation of dopamine with suitable aromatic amines, e.g. 3-aminotyrosine or p-phenylenediamine, leading to good quality black polymeric films. Capacitance–voltage experiments on poly(dopamine/3-aminotyrosine) and poly(dopamine/p-phenylenediamine)-based metal insulator semiconductor devices on p-Si indicated a significant increase in flat band voltage with respect to polydopamine and previous synthetic Eumelanin-based diodes. Variations of the flat band voltage under vacuum were observed for each device. These results point to polydopamine as a versatile Eumelanin-type water-dependent semiconductor platform amenable to fine tuning of its electronic properties through incorporation of π-conjugating aromatic amines to tailor functionality.
Markus J. Buehler - One of the best experts on this subject based on the ideXlab platform.
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Polydopamine and Eumelanin molecular structures investigated with ab initio calculations
Chemical science, 2016Co-Authors: Chun-teh Chen, Francisco J. Martin-martinez, Gang Seob Jung, Markus J. BuehlerAbstract:A set of computational methods that contains a brute-force algorithmic generation of chemical isomers, molecular dynamics (MD) simulations, and density functional theory (DFT) calculations is reported and applied to investigate nearly 3000 probable molecular structures of polydopamine (PDA) and Eumelanin. All probable early-polymerized 5,6-dihydroxyindole (DHI) oligomers, ranging from dimers to tetramers, have been systematically analyzed to find the most stable geometry connections as well as to propose a set of molecular models that represents the chemically diverse nature of PDA and Eumelanin. Our results indicate that more planar oligomers have a tendency to be more stable. This finding is in good agreement with recent experimental observations, which suggested that PDA and Eumelanin are composed of nearly planar oligomers that appear to be stacked together via π–π interactions to form graphite-like layered aggregates. We also show that there is a group of tetramers notably more stable than the others, implying that even though there is an inherent chemical diversity in PDA and Eumelanin, the molecular structures of the majority of the species are quite repetitive. Our results also suggest that larger oligomers are less likely to form. This observation is also consistent with experimental measurements, supporting the existence of small oligomers instead of large polymers as main components of PDA and Eumelanin. In summary, this work brings an insight into the controversial structure of PDA and Eumelanin, explaining some of the most important structural features, and providing a set of molecular models for more accurate modeling of Eumelanin-like materials.
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Polydopamine and Eumelanin: From Structure–Property Relationships to a Unified Tailoring Strategy
Accounts of Chemical Research, 2014Co-Authors: Marco D'ischia, Vincent Ball, Chun-teh Chen, Alessandra Napolitano, Markus J. BuehlerAbstract: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...
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Polydopamine and Eumelanin: from structure-property relationships to a unified tailoring strategy
Accounts of chemical research, 2014Co-Authors: Marco D'ischia, Vincent Ball, Chun-teh Chen, Alessandra Napolitano, Markus J. BuehlerAbstract: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...
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Comparison of synthetic dopamine-Eumelanin formed in the presence of oxygen and Cu2+ cations as oxidants.
Langmuir : the ACS journal of surfaces and colloids, 2013Co-Authors: Vincent Ball, José Grácio, Mercedes Vila, Manoj Kumar Singh, Marie-hélène Metz-boutigue, Marc Michel, Jérôme Bour, Valérie Toniazzo, David S. Ruch, Markus J. BuehlerAbstract:Eumelanin is not only a ubiquitous pigment among living organisms with photoprotective and antioxidant functions, but is also the subject of intense interest in materials science due to its photoconductivity and as a possible universal coating platform, known as “polydopamine films”. The structure of Eumelanin remains largely elusive, relying either on a polymeric model or on a heterogeneous aggregate structure. The structure of Eumelanin as well as that of the closely related “polydopamine films” can be modified by playing on the nature of the oxidant used to oxidize dopamine or related compounds. In this investigation, we show that dopamine–Eumelanins produced from dopamine in the presence of either air (O2 being the oxidant) or Cu2+ cations display drastically different optical and colloidal properties in relation with a different supramolecular assembly of the oligomers of 5,6 dihydroxyindole, the final oxidation product of dopamine. The possible origin of these differences is discussed on the basis o...
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self assembly of tetramers of 5 6 dihydroxyindole explains the primary physical properties of Eumelanin experiment simulation and design
ACS Nano, 2013Co-Authors: Chun-teh Chen, Vincent Ball, José Grácio, Manoj Kumar Singh, Valérie Toniazzo, David Ruch, Markus J. BuehlerAbstract:Eumelanin is a ubiquitous pigment in nature and has many intriguing physicochemical properties, such as broad-band and monotonous absorption spectrum, antioxidant and free radical scavenging behavior, and strong nonradiative relaxation of photoexcited electronic states. These properties are highly related to its structural and mechanical properties and make Eumelanin a fascinating candidate for the design of multifunctional nanomaterials. Here we report joint experimental–computational investigation of the structural and mechanical properties of Eumelanin assemblies produced from dopamine, revealing that the mass density of dry Eumelanin is 1.55 g/cm3 and its Young’s modulus is ≈5 GPa. We also find that wet Eumelanin has a lower mass density and Young’s modulus depending on the water-to-melanin ratio. Most importantly, our data show that Eumelanin molecules tend to form secondary structures based on noncovalent π stacking in both dry and wet conditions, with an interlayer distance between Eumelanin molecu...
Marco D'ischia - One of the best experts on this subject based on the ideXlab platform.
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Deciphering Molecular Mechanisms of Interface Buildup and Stability in Porous Si/Eumelanin Hybrids.
International journal of molecular sciences, 2017Co-Authors: Elisa Pinna, Marco D'ischia, Aleandro Antidormi, Claudio Melis, Luciano Colombo, Roberto Cardia, E. Sechi, Giancarlo Cappellini, Guido MulaAbstract:Porous Si/Eumelanin hybrids are a novel class of organic–inorganic hybrid materials that hold considerable promise for photovoltaic applications. Current progress toward device setup is, however, hindered by photocurrent stability issues, which require a detailed understanding of the mechanisms underlying the buildup and consolidation of the Eumelanin–silicon interface. Herein we report an integrated experimental and computational study aimed at probing interface stability via surface modification and Eumelanin manipulation, and at modeling the organic–inorganic interface via formation of a 5,6-dihydroxyindole (DHI) tetramer and its adhesion to silicon. The results indicated that mild silicon oxidation increases photocurrent stability via enhancement of the DHI–surface interaction, and that higher oxidation states in DHI oligomers create more favorable conditions for the efficient adhesion of growing Eumelanin.
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Fifty Shades" of Black and Red or How Carboxyl Groups Fine Tune Eumelanin and Pheomelanin Properties.
International Journal of Molecular Sciences, 2016Co-Authors: Raffaella Micillo, Kenzo Koike, Giuseppe Monfrecola, Lucia Panzella, Alessandra Napolitano, Marco D'ischiaAbstract:Recent advances in the chemistry of melanins have begun to disclose a number of important structure-property-function relationships of crucial relevance to the biological role of human pigments, including skin (photo) protection and UV-susceptibility. Even slight variations in the monomer composition of black Eumelanins and red pheomelanins have been shown to determine significant differences in light absorption, antioxidant, paramagnetic and redox behavior, particle morphology, surface properties, metal chelation and resistance to photo-oxidative wear-and-tear. These variations are primarily governed by the extent of decarboxylation at critical branching points of the Eumelanin and pheomelanin pathways, namely the rearrangement of dopachrome to 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA), and the rearrangement of 5-S-cysteinyldopa o-quinoneimine to 1,4-benzothiazine (BTZ) and its 3-carboxylic acid (BTZCA). In Eumelanins, the DHICA-to-DHI ratio markedly affects the overall antioxidant and paramagnetic properties of the resulting pigments. In particular, a higher content in DHICA decreases visible light absorption and paramagnetic response relative to DHI-based melanins, but markedly enhances antioxidant properties. In pheomelanins, likewise, BTZCA-related units, prevalently formed in the presence of zinc ions, appear to confer pronounced visible and ultraviolet A (UVA) absorption features, accounting for light-dependent reactive oxygen species (ROS) production, whereas non-carboxylated benzothiazine intermediates seem to be more effective in inducing ROS production by redox cycling mechanisms in the dark. The possible biological and functional significance of carboxyl retention in the Eumelanin and pheomelanin pathways is discussed.
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Polydopamine and Eumelanin: From Structure–Property Relationships to a Unified Tailoring Strategy
Accounts of Chemical Research, 2014Co-Authors: Marco D'ischia, Vincent Ball, Chun-teh Chen, Alessandra Napolitano, Markus J. BuehlerAbstract: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...
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Polydopamine and Eumelanin: from structure-property relationships to a unified tailoring strategy
Accounts of chemical research, 2014Co-Authors: Marco D'ischia, Vincent Ball, Chun-teh Chen, Alessandra Napolitano, Markus J. BuehlerAbstract: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...
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Exploring the frontiers of synthetic Eumelanin polymers by high-resolution matrix-assisted laser/desorption ionization mass spectrometry.
Journal of mass spectrometry : JMS, 2012Co-Authors: Samantha Reale, Marco D'ischia, Alessandro Pezzella, Marcello Crucianelli, Francesco De AngelisAbstract:New trends in material science and nanotechnologies have spurred growing interest in Eumelanins black insoluble biopolymers derived by tyrosinase-catalysed oxidation of tyrosine via 5,6-dihydroxyindole (DHI) and its 2-carboxylic acid (DHICA). Efficient antioxidant and photoprotective actions, associated with peculiar optoelectronic properties, are recognised as prominent functions of Eumelanin macromolecules within the human and mammalian pigmentary system, making them unique candidates for the realisation of innovative bio-inspired functional soft materials, with structure-based physical–chemical properties. An unprecedented breakthrough into the mechanism of synthetic Eumelanin buildup has derived from a detailed investigation of the oxidative polymerization of DHI and its N-methyl derivative (NMDHI) by linear and reflectron matrix-assisted laser/desorption ionization mass spectrometry. Regular collections of oligomers of increasing masses, spanning the entire m/z ranges up to 5000 Da (>30-mer) and 8000 Da (> 50-mer) for the two building blocks, respectively, were disclosed. It is the first time that the in vitro polymerisation of dihydroxyindoles to form synthetic Eumelanins is explored up to its high mass limits, giving at the same time information on the polymerisation mode, whether it follows a stepwise pattern (being this the conclusion in our case) or a staking sequencing of small-sized entities. It also highlighted the influence of the N-methyl substituent on the polymerization process; this opens the way to the production of N-functionalized, synthetic Eumelanin-inspired soft materials, for possible future technological applications. Copyright © 2012 John Wiley & Sons, Ltd.
Marco Dischia - One of the best experts on this subject based on the ideXlab platform.
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Eumelanin broadband absorption develops from aggregation modulated chromophore interactions under structural and redox control
Scientific Reports, 2017Co-Authors: Raffaella Micillo, Kenzo Koike, Lucia Panzella, Alessandra Napolitano, Mariagrazia Iacomino, Giacomo Prampolini, Ivo Cacelli, Alessandro Ferretti, Orlando Crescenzi, Marco DischiaAbstract:Eumelanins, the chief photoprotective pigments in man and mammals, owe their black color to an unusual broadband absorption spectrum whose origin is still a conundrum. Excitonic effects from the interplay of geometric order and disorder in 5,6-dihydroxyindole (DHI)-based oligomeric/polymeric structures play a central role, however the contributions of structural (scaffold-controlled) and redox (π-electron-controlled) disorder have remained uncharted. Herein, we report an integrated experimental-theoretical entry to Eumelanin chromophore dynamics based on poly(vinyl alcohol)-controlled polymerization of a large set of 5,6-dihydroxyindoles and related dimers. The results a) uncover the impact of the structural scaffold on Eumelanin optical properties, disproving the widespread assumption of a universal monotonic chromophore; b) delineate Eumelanin chromophore buildup as a three-step dynamic process involving the rapid generation of oxidized oligomers, termed melanochromes (phase I), followed by a slow oxidant-independent band broadening (phase II) leading eventually to scattering (phase III); c) point to a slow reorganization-stabilization of melanochromes via intermolecular redox interactions as the main determinant of visible broadband absorption.
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irreversible evolution of Eumelanin redox states detected by an organic electrochemical transistor en route to bioelectronics and biosensing
Journal of Materials Chemistry B, 2013Co-Authors: Giuseppe Tarabella, Marco Dischia, Alessandro Pezzella, Agostino Romeo, Pasquale Dangelo, Nicola Coppede, M Calicchio, R Mosca, Salvatore IannottaAbstract:Organic electrochemical transistors (OECTs) are currently emerging as powerful tools for biosensing, bioelectronics and nanomedical applications owing to their ability to operate under liquid phase conditions optimally integrating electronic and biological systems. Herein we disclose the unique potential of OECTs for detecting and investigating the electrical properties of insoluble Eumelanin biopolymers. Gate current measurements on fine aqueous suspensions of a synthetic Eumelanin sample from 5,6-dihydroxyindole (DHI) revealed a well detectable hysteretic response similar to that of the pure monomer in solution, with the formal concentration of the polymer as low as 10−6 M. Induction of the gate current would reflect electron transfer from solid Eumelanin to the Pt-electrode sustained by redox active catechol/quinone components of the polymer. A gradual decrease in gate current and areas subtended by hysteretic loops were observed over 5 cycles both in the Eumelanin- and DHI-based devices, suggesting evolution of the polymer from a far-from-the-equilibrium redox state toward a more stable electronic arrangement promoted by redox exchange with the gate electrode. OECTs are thus proposed as valuable tools for the efficient heterogeneous-phase sensing of Eumelanins and to gauge their peculiar electrical and redox behaviour.
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the Eumelanin intermediate 5 6 dihydroxyindole 2 carboxylic acid is a messenger in the cross talk among epidermal cells
Journal of Investigative Dermatology, 2012Co-Authors: Daniela Kovacs, Lucia Panzella, Alessandra Napolitano, Enrica Flori, Vittoria Maresca, Monica Ottaviani, Nicaela Aspite, Maria Lucia Dellanna, Mauro Picardo, Marco DischiaAbstract:Interest in colorless intermediates of melanocyte metabolism has traditionally been related to their role as melanin precursors, though several lines of evidence scattered in the literature suggested that these compounds may exert an antioxidant and protective function per se unrelated to pigment synthesis. Herein, we disclose the remarkable protective and differentiating effects of 5,6-dihydroxyindole-2-carboxylic acid (DHICA), a diffusible dopachrome tautomerase (DCT)-dependent Eumelanin intermediate, on primary cultures of human keratinocytes. At micromolar concentrations, DHICA induced: (a) time- and dose-dependent reduction of cell proliferation without concomitant toxicity; (b) enhanced expression of early (spinous keratins K1 and K10 and envelope protein involucrin) and late (loricrin and filaggrin) differentiation markers; (c) increased activities and expression of antioxidant enzymes; and (d) decreased cell damage and apoptosis following UVA exposure. The hitherto unrecognized role of DHICA as an antiproliferative, protective, and antiapoptotic endogenous cell messenger points to a reappraisal of the biological functions of melanocytes and DCT in skin homeostasis and photoprotection beyond the mere provision of melanin pigments, and provides, to our knowledge, a previously unreported possible explanation to the higher resistance of the dark-skinned eumelanic phenotypes to sunburn and skin cancer.
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exploring the frontiers of synthetic Eumelanin polymers by high resolution matrix assisted laser desorption ionization mass spectrometry
Journal of Mass Spectrometry, 2012Co-Authors: Samantha Reale, Marco Dischia, Alessandro Pezzella, Marcello Crucianelli, Francesco De AngelisAbstract:New trends in material science and nanotechnologies have spurred growing interest in Eumelanins black insoluble biopolymers derived by tyrosinase-catalysed oxidation of tyrosine via 5,6-dihydroxyindole (DHI) and its 2-carboxylic acid (DHICA). Efficient antioxidant and photoprotective actions, associated with peculiar optoelectronic properties, are recognised as prominent functions of Eumelanin macromolecules within the human and mammalian pigmentary system, making them unique candidates for the realisation of innovative bio-inspired functional soft materials, with structure-based physical–chemical properties. An unprecedented breakthrough into the mechanism of synthetic Eumelanin buildup has derived from a detailed investigation of the oxidative polymerization of DHI and its N-methyl derivative (NMDHI) by linear and reflectron matrix-assisted laser/desorption ionization mass spectrometry. Regular collections of oligomers of increasing masses, spanning the entire m/z ranges up to 5000 Da (>30-mer) and 8000 Da (> 50-mer) for the two building blocks, respectively, were disclosed. It is the first time that the in vitro polymerisation of dihydroxyindoles to form synthetic Eumelanins is explored up to its high mass limits, giving at the same time information on the polymerisation mode, whether it follows a stepwise pattern (being this the conclusion in our case) or a staking sequencing of small-sized entities. It also highlighted the influence of the N-methyl substituent on the polymerization process; this opens the way to the production of N-functionalized, synthetic Eumelanin-inspired soft materials, for possible future technological applications. Copyright © 2012 John Wiley & Sons, Ltd.
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disentangling Eumelanin black chromophore visible absorption changes as signatures of oxidation state and aggregation dependent dynamic interactions in a model water soluble 5 6 dihydroxyindole polymer
Journal of the American Chemical Society, 2009Co-Authors: Alessandro Pezzella, Lucia Panzella, Alessandra Napolitano, Alfonso Iadonisi, Silvia Valerio, Matteo Adinolfi, Marco DischiaAbstract:A fundamental unsettled issue concerning Eumelanins, the functional biopolymers of human skin and hair, is why they are black. The experimental difficulty lies in the virtual insolubility of these pigments, causing marked scattering effects and hindering characterization of the intrinsic absorption properties of the heterogeneous species produced by oxidative polymerization of 5,6-dihydroxyindole (DHI) and related monomer precursors. The synthesis of spectrally robust, water-soluble DHI polymers is therefore an important goal in the prospects of disentangling intrinsic absorption properties of Eumelanin components by circumventing scattering effects. Reported herein is the first water-soluble DHI polymer produced by oxidation of ad hoc designed 5,6-dihydroxy-3-indolyl-1-thio-β-D-galactopyranoside (1). The dark brown polymer exhibited a distinct band at 314 nm and a broad visible absorption, resembling that of natural Eumelanins. Main isolable oligomer intermediates including 2,7′- and 2,4′-biindolyls 2 an...
