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Current Biology : CB Feb 2020Melanins are a unique class of pigments found throughout the biosphere with a wide variety of functions, structures, and presentations. Cordero and Casadevall highlight...
Melanins are a unique class of pigments found throughout the biosphere with a wide variety of functions, structures, and presentations. Cordero and Casadevall highlight the wide range of places melanins are found and the diverse functions they play in nature.
Topics: Melanins
PubMed: 32097632
DOI: 10.1016/j.cub.2019.12.042 -
The International Journal of... Nov 1997Melanin is an irregular light-absorbing polymer containing indoles and other intermediate products derived from the oxidation of tyrosine. Melanin is widely dispersed in... (Review)
Review
Melanin is an irregular light-absorbing polymer containing indoles and other intermediate products derived from the oxidation of tyrosine. Melanin is widely dispersed in the animal and plant kingdoms. It is the major pigment present in the surface structures of vertebrates. The critical step in melanin biogenesis is the oxidation of tyrosine by the enzyme tyrosinase. In vertebrates this enzyme is active only in specialized organelles in retinal pigment epithelium and melanocytes. In mammals melanin is formed as intracellular granules. Melanin granules are transferred from melanocytes to epithelial cells and form the predominant pigment of hair and epidermis. Melanin has many biological functions. Reactive quinone intermediates in the melanin biosynthetic pathway exhibit antibiotic properties and the polymer is an important strengthening element of plant cell walls and insect cuticle. Light absorption by melanin has several biological functions, including photoreceptor shielding, thermoregulation, photoprotection, camouflage and display. Melanin is a powerful cation chelator and may act as a free radical sink. Melanin is used commercially as a component of photoprotective creams, although mainly for its free radical scavenging rather than its light absorption properties. The pigment is also a potential target for anti-melanoma therapy.
Topics: Anti-Bacterial Agents; Chelating Agents; Humans; Hypopigmentation; Light; Melanins; Oxidation-Reduction; Photons; Structure-Activity Relationship
PubMed: 9451820
DOI: 10.1016/s1357-2725(97)00013-7 -
Journal of Basic Microbiology Mar 2021Melanins are a diverse group of dark pigments with similar properties. In fungi, the most studied is the dihydroxynaphtalene (DHN)-melanin, present in several species... (Review)
Review
Melanins are a diverse group of dark pigments with similar properties. In fungi, the most studied is the dihydroxynaphtalene (DHN)-melanin, present in several species including all the chromoblastomycosis agents, a chronic, disabling, and recalcitrant subcutaneous mycosis. It is synthesized in a pathway known as the pentaketide pathway, which has the agrochemical tricyclazole as an inhibitor, widely used in in vitro studies because it does not prevent the growth of fungi. There are different methodologies for qualitative and quantitative analyses of DHN-melanin, which made it possible to discover its important structural and antioxidant functions, with melanin acting as a protective factor against the host's immune system. Also, it can interact with some of the main antifungals of medical interest, reducing its activity and the susceptibility of fungi to these agents. This review aims to discuss the aspects of DHN-melanin, focusing on chromoblastomycosis, bringing the main findings of the published scientific studies, and highlighting the need for further research to understand this important fungal pathogenicity and a virulence factor.
Topics: Antifungal Agents; Antioxidants; Ascomycota; Chromoblastomycosis; Humans; Melanins; Naphthols
PubMed: 33576034
DOI: 10.1002/jobm.202000664 -
Journal of Materials Chemistry. B Sep 2023Melanin, a widely distributed pigment found in various organisms, possesses distinct structures that can be classified into five main types: eumelanin (found in animals... (Review)
Review
Melanin, a widely distributed pigment found in various organisms, possesses distinct structures that can be classified into five main types: eumelanin (found in animals and plants), pheomelanin (found in animals and plants), allomelanin (found in plants), neuromelanin (found in animals), and pyomelanin (found in fungi and bacteria). In this review, we present an overview of the structure and composition of melanin, as well as the various spectroscopic identification methods that can be used, such as Fourier transform infrared (FTIR) spectroscopy, electron spin resonance (ESR) spectroscopy, and thermogravimetric analysis (TGA). We also provide a summary of the extraction methods of melanin and its diverse biological activities, including antibacterial properties, anti-radiation effects, and photothermal effects. The current state of research on natural melanin and its potential for further development is discussed. In particular, the review provides a comprehensive summary of the analysis methods used to determine melanin species, offering valuable insights and references for future research. Overall, this review aims to provide a thorough understanding of the concept and classification of melanin, its structure, physicochemical properties, and structural identification methods, as well as its various applications in the field of biology.
Topics: Animals; Melanins; Electron Spin Resonance Spectroscopy; Spectroscopy, Fourier Transform Infrared; Forecasting
PubMed: 37432655
DOI: 10.1039/d3tb01132a -
World Journal of Microbiology &... Oct 2020Melanins are natural biopolymers that are known to contribute to different biological processes and to protect organisms from adverse environmental conditions. During... (Review)
Review
Melanins are natural biopolymers that are known to contribute to different biological processes and to protect organisms from adverse environmental conditions. During the past decade, melanins have attracted increasing attention for their use in organic semiconductors and bioelectronics, drug delivery, photoprotection and environmental bioremediation. Although considerable advances in these fields have been achieved, real-world applications of melanins are still scarce, probably due to the limited and expensive source of natural melanin. Nevertheless, recent biotechnological advances have allowed for relatively large-scale production of microbial melanins, which could replace current commercial melanin. In this review, we first describe different melanin sources and highlight the advantages and disadvantages of each production method. Our focus is on the microbial synthesis of melanins, including the methodology and mechanism of melanin formation. Applications of microbial melanins are also discussed, and an outlook on how to push the field forward is discussed.
Topics: Bacteria; Biopolymers; Biotechnology; Chemical Phenomena; Drug Delivery Systems; Fungi; Humans; Melanins; Molecular Structure
PubMed: 33043393
DOI: 10.1007/s11274-020-02941-z -
Biotechnology Advances Dec 2021Melanin is a common name for a group of biopolymers with the dominance of potential applications in medical sciences, cosmeceutical, bioremediation, and bioelectronic... (Review)
Review
Melanin is a common name for a group of biopolymers with the dominance of potential applications in medical sciences, cosmeceutical, bioremediation, and bioelectronic applications. The broad distribution of these pigments suggests their role to combat abiotic and biotic stresses in diverse life forms. Biosynthesis of melanin in fungi and bacteria occurs by oxidative polymerization of phenolic compounds predominantly by two pathways, 1,8-dihydroxynaphthalene [DHN] or 3,4-dihydroxyphenylalanine [DOPA], resulting in different kinds of melanin, i.e., eumelanin, pheomelanin, allomelanin, pyomelanin, and neuromelanin. The enzymes responsible for melanin synthesis belong mainly to tyrosinase, laccase, and polyketide synthase families. Studies have shown that manipulating culture parameters, combined with recombinant technology, can increase melanin yield for large-scale production. Despite significant efforts, its low solubility has limited the development of extraction procedures, and heterogeneous structural complexity has impaired structural elucidation, restricting effective exploitation of their biotechnological potential. Innumerable studies have been performed on melanin pigments from different taxa of life in order to advance the knowledge about melanin pigments for their efficient utilization in diverse applications. These studies prompted an urgent need for a comprehensive review on melanin pigments isolated from microorganisms, so that such review encompassing biosynthesis, bioproduction, characterization, and potential applications would help researchers from diverse background to understand the importance of microbial melanins and to utilize the information from the review for planning studies on melanin. With this aim in mind, the present report compares conventional and modern ideas for environment-friendly extraction procedures for melanin. Furthermore, the characteristic parameters to differentiate between eumelanin and pheomelanin are also mentioned, followed by their biotechnological applications forming the basis of industrial utilization. There lies a massive scope of work to circumvent the bottlenecks in their isolation and structural elucidation methodologies.
Topics: Bacteria; Biopolymers; Fungi; Laccase; Melanins
PubMed: 34022328
DOI: 10.1016/j.biotechadv.2021.107773 -
Critical Reviews in Food Science and... 2022Melanin is a dark brown to black biomacromolecule with biologically active multifunctional properties that do not have a precise chemical structure, but its structure... (Review)
Review
Melanin is a dark brown to black biomacromolecule with biologically active multifunctional properties that do not have a precise chemical structure, but its structure mainly depends on the polymerization conditions during the synthesis process. Natural melanin can be isolated from various animal, plant, and microbial sources, while synthetic melanin-like compounds can be synthesized by simple polymerization of dopamine. Melanin is widely used in various areas due to its functional properties such as photosensitivity, light barrier property, free radical scavenging ability, antioxidant activity, etc. It also has an excellent ability to act as a reducing agent and capping agent to synthesize various metal nanoparticles. Melanin nanoparticles (MNP) or melanin-like nanoparticles (MLNP) have the unique potential to act as functional materials to improve nanocomposite films' physical and functional properties. Various food packaging and biomedical applications have been made alone or by mixing melanin or MLNP. In this review, the general aspects of melanin that highlight biological activity, along with a description of MNP and the use as nanofillers in packaging films as well as reducing and capping agents and biomedical applications, were comprehensively reviewed.
Topics: Animals; Biotechnology; Food Packaging; Melanins; Metal Nanoparticles; Nanocomposites
PubMed: 33523716
DOI: 10.1080/10408398.2021.1878097 -
Journal of the American Chemical Society Mar 2021Commonly known as a skin pigment, melanin has a vital role in UV radiation protection, primarily acting as a radical scavenger. However, a lesser known natural property...
Commonly known as a skin pigment, melanin has a vital role in UV radiation protection, primarily acting as a radical scavenger. However, a lesser known natural property of melanin, observed in some melanized organisms, is its capacity to adsorb toxins, including metals and organic molecules. Inspired by this, we set out to generate a synthetic porous melanin that would pave the way to enhancing the natural adsorbent properties of melanin and melanin-like materials. Here, we developed a method for the synthesis of porous polydopamine-based melanin utilizing a mesoporous silica (MS) nanoparticle template and characterized its physical properties. Through the oxidative polymerization of dopamine, followed by the etching of silica, we generated synthetic porous melanin (SPM) with the highest measured surface area of any known polydopamine-based material. The prepared SPM was effective for the uptake of various gases and organophosphate toxins, with the material exhibiting high selectivity for CO over CH and high potential for ammonia capture. Given the demonstrated advantages provided by synthetic porous melanin and melanin's role as an adsorbent in nature, we anticipate the discovery of porous analogues in biological systems.
Topics: Carbon Dioxide; Indoles; Melanins; Methane; Polymers; Porosity
PubMed: 33600146
DOI: 10.1021/jacs.0c10465 -
International Journal of Molecular... Feb 2023Melanin is a biological pigment formed by indoles and phenolic compounds. It is widely found in living organisms and has a variety of unique properties. Due to its... (Review)
Review
Melanin is a biological pigment formed by indoles and phenolic compounds. It is widely found in living organisms and has a variety of unique properties. Due to its diverse characteristics and good biocompatibility, melanin has become the focus in the fields of biomedicine, agriculture, the food industry, etc. However, due to the wide range of melanin sources, complex polymerization properties, and low solubility of specific solvents, the specific macromolecular structure and polymerization mechanism of melanin remain unclear, which significantly limits the further study and application of melanin. Its synthesis and degradation pathways are also controversial. In addition, new properties and applications of melanin are constantly being discovered. In this review, we focus on the recent advances in the research of melanin in all aspects. Firstly, the classification, source, and degradation of melanin are summarized. Secondly, a detailed description of the structure, characterization, and properties of melanin is followed. The novel biological activity of melanin and its application is described at the end.
Topics: Melanins; Indoles; Solvents; Solubility
PubMed: 36901791
DOI: 10.3390/ijms24054360 -
Acta Biomaterialia Mar 2020Melanin is a biopolymer of easy and cheap availability that can be found among the living organisms and excels for its biocompatibility and biodegradability properties,... (Review)
Review
Melanin is a biopolymer of easy and cheap availability that can be found among the living organisms and excels for its biocompatibility and biodegradability properties, along with scavenging abilities, metal chelation and electronic conductance. This biomaterial can act as a nanocarrier or agent itself to be used in diverse biomedical applications, such as imaging, controlled drug release, bioengineering and bioelectronics, antioxidant applications and theranostics. In this review, the melanin source and structure, its physicochemical properties, melanin-like polymers as well as the differences among those will be elucidated. The focus will be the discussion of the current approaches that apply melanin nanoparticles (MNPs) and melanin-like nanoparticles (MLNPs) in the biomedical field, to which promising capabilities have been attributed, regarding optoelectronic, photoconductivity and photoacoustic. The use of these nanoparticles, in the last 10 years, in topics as drug delivery or theranostics will be detailed and the major achievements will be discussed. Overall, we anticipate that melanin can drive us toward a new paradigm in medical diagnostics and treatments, since applying melanin features possibly its use as a theranostics nanocarrier agent, not only for diagnostics, but also for photothermal therapy and controlled drug release through chemotherapy. STATEMENT OF SIGNIFICANCE: We present here a timely and opportune review article focusing the significant potential of melanin nanoparticles in biomedical applications, which will be discussed thoroughly. This biomaterial presents multiple capabilities that may be taken into consideration towards cancer theranostics, expecting a high future impact in the nanosized-platforms design and performance.
Topics: Animals; Antioxidants; Biomedical Technology; Drug Delivery Systems; Humans; Melanins; Nanoparticles; Theranostic Nanomedicine
PubMed: 32014585
DOI: 10.1016/j.actbio.2020.01.044