Properties Of Melanin Research Articles

Melanin in the Retinal Epithelium and Magnetic Sensing: A Review of Current Studies.

Coming in a variety of forms, melanin is one of the most abundant, stable, diverse, and evolutionarily ancient pigments found in living things in nature. These pigments often serve protective functions, typically well-adapted to their specific roles. One such protective function is metal chelation and cation exchange, which help regulate and buffer metal concentrations within cells. By binding to certain metals, melanin can acquire magnetic properties. Because of this, it may play a role in magnetic effects and possibly in the response of organisms to external magnetic fields and magnetic sensing. While there is melanin in plants, microbes, fungi, and invertebrates, certain types of melanin are specifically associated with the retina in vertebrates, including migrating bird and fish species. In this review, we examine studies focusing on the properties of melanin in these parts of the body and their possible association with magnetic sensing, and generally, magnetic sensing in the retina.

Fungal Peptidomelanin: A Novel Biopolymer for the Chelation of Heavy Metals.

Melanin is an amorphous, highly heterogeneous polymer found across all kingdoms of life. Although the properties of melanin can greatly vary, most forms are insoluble and strongly absorb light, appearing dark brown to black. Here, we describe a water-soluble form of melanin (peptidomelanin) secreted by the spores of Aspergillus niger (strain: melanoliber) during germination. Peptidomelanin is composed of an insoluble L-DOPA core polymer that is solubilized via short, copolymerized heterogeneous peptide chains forming a "corona" with a mean amino acid length of 2.6 ± 2.3. Based on in vitro experiments, we propose a biochemical copolymerization mechanism involving the hydroxylation of tyrosynylated peptides. Peptidomelanin is capable of chelating heavy metals such as lead, mercury, and uranium (as uranyl) in large quantities. Preliminary data indicates that peptidomelanin may have applications for the remediation of heavy metals in situ, including in agricultural settings.

Melanin: Nature's 4th bioorganic polymer.

The pigments known as the melanins are widely recognized for their responsibility in the coloration of human skin, eyes, hair, and minimising the harmful effects of solar ultraviolet radiation. But specialists are aware that the melanins are present in all living kingdoms, barring viruses, and have functionality that extends beyond neutralizing ionising radiation. The ubiquitous presence of melanin in almost all human organs, recognized in recent years, as well as the presence of melanin in organisms that are evolutionarily distant from each other, indicate the fundamental importance of this class of material for all life forms. In this review, we argue for the need to accept melanins as the fourth primordial class of biological polymers, along with nucleic acids, proteins and polysaccharides. We consistently compare the properties of these canonical biological polymers with the properties of melanin and highlight key features that fundamentally distinguish melanins, their function and its mysteries.

Recent Advances and Progress on Melanin: From Source to Application.

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.

The interplay of chemical structure, physical properties, and structural design as a tool to modulate the properties of melanins within mesopores

The design of modern devices that can fulfil the requirements for sustainability and renewable energy applications calls for both new materials and a better understanding of the mixing of existing materials. Among those, surely organic–inorganic hybrids are gaining increasing attention due to the wide possibility to tailor their properties by accurate structural design and materials choice. In this work, we’ll describe the tight interplay between porous Si and two melanic polymers permeating the pores. Melanins are a class of biopolymers, known to cause pigmentation in many living species, that shows very interesting potential applications in a wide variety of fields. Given the complexity of the polymerization process beyond the formation and structure, the full understanding of the melanins' properties remains a challenging task. In this study, the use of a melanin/porous Si hybrid as a tool to characterize the polymer’s properties within mesopores gives new insights into the conduction mechanisms of melanins. We demonstrate the dramatic effect induced on these mechanisms in a confined environment by the presence of a thick interface. In previous studies, we already showed that the interactions at the interface between porous Si and eumelanin play a key role in determining the final properties of composite materials. Here, thanks to a careful monitoring of the photoconductivity properties of porous Si filled with melanins obtained by ammonia-induced solid-state polymerization (AISSP) of 5,6-dihydroxyindole (DHI) or 1,8-dihydroxynaphthalene (DHN), we investigate the effect of wet, dry, and vacuum cycles of storage from the freshly prepared samples to months-old samples. A computational study on the mobility of water molecules within a melanin polymer is also presented to complete the understanding of the experimental data. Our results demonstrate that: (a) the hydration-dependent behavior of melanins is recovered in large pores (≈ 60 nm diameter) while is almost absent in thinner pores (≈ 20 nm diameter); (b) DHN-melanin materials can generate higher photocurrents and proved to be stable for several weeks and more sensitive to the wet/dry variations.

NIR-Mediated drug release and tumor theranostics using melanin-loaded liposomes

BackgroundHeat generation in a drug delivery carrier by exposure to near-infrared (NIR) light with excellent tissue transmittance is an effective strategy for drug release and tumor therapy. Because liposomes have amphiphilic properties, they are useful as drug carriers. Liposomes are also very suitable for drug delivery strategies using heat generation by NIR laser because lipid bilayers are easily broken by heat. Thermally generated bubbles from liposomes not only induce drug release, but also enable ultrasound imaging.MethodsMelanin, perfluorohexane (PFH), and 5-fluorouracil (5-FU)-loaded liposomes (melanin@PFH@5-FU-liposomes) that can generate heat and bubble by NIR laser irradiation were prepared by a thin film method. Conversion of light to heat and bubble generation of melanin@PFH@5-FU-liposomes were evaluated using an infrared (IR) thermal imaging camera and an ultrasound imaging system both in vitro and in vivo. To investigate tumor therapeutic effect, NIR laser of 808 nm was used to irradiate tumor site for 10 min after injecting melanin@PFH@5-FU-liposome into tail veins of CT26-bearing mice.ResultsMelanin@PFH@5-FU-liposomes showed a spherical shape with a size of 209.6 ± 4.3 nm. Upon NIR laser irradiation, melanin@PFH@5-FU-liposomes exhibited effective temperature increase both in vitro and in vivo. In this regard, temperature increase caused a phase transition of PFH to induce bubble generation dramatically, resulting in effective drug release behavior and ultrasound imaging. The temperature of the tumor site was increased to 52 t and contrast was greatly enhanced during ultrasound imaging due to the generation of bubble. More importantly, tumor growth was effectively inhibited by injection of melanin@PFH@5-FU-liposomes with laser irradiation.ConclusionsBased on intrinsic photothermal properties of melanin and phase transition properties of PFH, melanin@PFH@5-FU-liposomes exhibited effective heat and bubble generation upon NIR laser irradiation. The elevated temperature induced bubble generation, resulting in contrast enhancement of ultrasound imaging. Melanin@PFH@5-FU-liposomes under NIR laser irradiation induced the death of cancer cells, thereby effectively inhibiting tumor growth. These results suggest that melanin@PFH@5-FU-liposomes can be utilized as a promising agent for photothermal tumor therapy and ultrasound imaging.

Application of melanin as biological functional material in composite film field

Abstract Melanin comes from a wide range of sources. It can be isolated and characterized from some plants, animals and microorganisms, and can also be simply polymerized by dopamine. It has many biological properties such as antioxidant, ultraviolet shielding and bacteriostasis. Based on the above characteristics, the addition of melanin to film-forming materials can improve the relevant physical properties and functional properties of the film. In this article, the structure and properties of melanin were briefly introduced, and then the advantages and related research progress of melanin as a functional filler in the field of composite film were summarized.

Melanin-Binding Colorants: Updating Molecular Modeling, Staining and Labeling Mechanisms, and Biomedical Perspectives

Melanin and melanoma tumors are two fields of increasing interest in biomedical research. Melanins are ubiquitous biopigments with adaptive value and multiple functions, and occur in the malignant melanoma. Although several chemical structures have been proposed for eumelanin, molecular modeling and orbitals indicate that a planar or spiral benzoquinone-porphycene polymer would be the model that better explains the broad-band light and ultrasound absorption, electric conductivity, and graphite-like organization shown by X-ray crystallography and electron microscopy. Lysosomes and melanosomes are selectively labeled by vital probes, and melanin also binds to metal cations, colorants, and drugs, with important consequences in pharmacology, pathology, and melanoma therapy. In addition to traditional and recent oncologic treatments, photodynamic, photothermal, and ultrasound protocols represent novel modalities for melanoma therapy. Since eumelanin is practically the ideal photothermal and ultrasound sensitizer, the vibrational decay from photo-excited electrons after NIR irradiation, or the electrochemical production of ROS and radicals after ultrasound absorption, induce an efficient heating or oxidative response, resulting in the damage and death of tumor cells. This allows repetitive treatments due to the remaining melanin contained in tumoral melanophages. Given that evolution and prognosis of the advanced melanoma is still a concern, new biophysical procedures based on melanin properties can now be developed and applied.

Treatment of Diabetic Retinopathy with Medical Enhancement of The Unsuspected Intrinsic Property of Melanin to Dissociates the Water Molecule

Treatment of Diabetic Retinopathy with Medical Enhancement of The Unsuspected Intrinsic Property of Melanin to Dissociates the Water Molecule

Melanocytic Tumors

Primary melanocytic neoplasms of the central nervous system(CNS)presumably arise from leptomeningeal melanocytes that are derived from the neural crest. Melanocytic neoplasms associated with neurocutaneous melanosis likely derive from melanocyte precursor cells that reach the CNS after somatic mutations, mostly, of the NRAS. They should be distinguished from other melanotic tumors involving the CNS, including metastatic melanoma and other primary tumors that undergo melanization, such as melanocytic schwannomas, medulloblastomas, paragangliomas, and various gliomas, because these lesions require different patient workups and therapy. Primary melanocytic neoplasms of the CNS that are diffuse and do not form macroscopic masses are called melanocytoses, whereas malignant diffuse or multifocal lesions are collectively called melanomatoses. Benign and intermediate-grade tumoral lesions are called melanocytomas. Discrete malignant tumors are called melanomas. CT and MRI of melanocytosis and melanomatosis show diffuse thickening and enhancement of the leptomeninges, often with focal or multifocal nodularity. Depending on the melanin content, diffuse and circumscribed melanocytic tumors of the CNS may show some characteristics on CT and MRI: iso- to hyperattenuation on CT and paramagnetic properties of melanin on MRI resulting in an isointense signal on T1WIs and iso- to hypointensity on T2WIs.

Near-Infrared Laser-Responsive Photothermal Bubble-Generating PLA Nanoparticles for Controlled Drug Release

Stimuli-responsive drug delivery systems can respond to specific external stimuli, resulting in improved treatment outcomes and reduced side effects from their controllable site-specific release ability. The aim of this study was to develop a thermo-responsive bubble-generating drug release platform by near-infrared (NIR) laser irradiation using melanin-perfluorohexane-methotrexate-polylactic acid (Mel @PFH@MTX-PLA) nanoparticles. Mel@PFH@MTX-PLA nanoparticles were successfully prepared without precipitation or aggregation. By adjusting the amount of perfluorohexane (PFH), a size of Mel@PFH@MTX-PLA nanoparticles with optimal conditions was about 52.75 ± 1.41 nm. Due to the photothermal conversion properties of melanin, the temperature of the Mel@PFH@MTX-PLA nanoparticles was increased to about 59.2 °C after 7 min of 808 nm NIR laser irradiation at a power density of 1.5 W/cm2. The NIR laser-induced temperature increase triggered additional drug release and caused the phase transition of PFH, resulting in dramatic bubble generation. The resultant Mel@PFH@MTX-PLA nanoparticles can be utilized in biomedical applications as promising carriers for localized and controlled drug delivery.

CT and MRI findings in relapsing primary malignant melanoma of the lacrimal sac: a case report and brief literature review

BackgroundPrimary lacrimal sac melanoma is an extremely rare condition with fewer than 50 cases reported so far. Clinically, its symptoms resemble those of dacryocystitis, leading to frequent misdiagnosis. During diagnosis, imaging examination is often performed to differentiate tumors from inflammation. In this report, we present a case of primary lacrimal sac melanoma and summarize the CT and MRI characteristics of lacrimal sac melanoma.Case presentationWe report a 50-year-old female patient who had undergone a dacryocystectomy for the left lacrimal sac mass. Postoperative pathological examination confirmed the presence of primary malignant melanoma. Three months later, a lump in the lacrimal sac area was found. The patient underwent CT and MR examinations. CT scan demonstrated a partially well-defined soft mass in the fossa of left lacrimal sac extending into the nasolacrimal duct and anterior ethmoid sinus. MRI revealed an intermediate signal intensity on T1 and iso-or hyper-signal on T2 weighted images. Histopathological examination on biopsy confirmed recurrence of primary lacrimal sac melanoma.Discussion and conclusionsNone has described the CT and MR findings of primary lacrimal sac melanoma so far. Typically, MR images show hyperintensity signal on T1-weighted images and hypointense signal on T2-weighted images owing to the paramagnetic properties of melanin. In contrast to previous reports and the present case, most cases do not present these typical signals. Thus, reporting such radiological findings is important to create awareness on variant images of primary lacrimal sac melanoma. This will reduce misdiagnosis and mistreatment.

Properties of melanin from Lachnum YM156 and its hepatoprotective effect in Cd-exposure mice

Natural melanin was extracted from Lachnum YM156 (LIM). LIM had better thermostability and light resistance, and its solubility was relatively high under alkaline conditions. Simultaneously, we examined its hepatoprotective effect in Cd-exposure mice. Cd-exposure resulted in decreasing weight growth rate, raised liver index, elevated serum levels of alanine aminotransferase (ALT) and aspartate aminotransaminase (AST), and increased Cd accumulation in livers. Hepatic oxidative stress was evidenced by increased malondialdehyde (MDA) contents, decreased glutathione (GSH) contents, and decreased activities of dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) after CdCl2 administration. Additionally, Cd-exposure also increased the liver level of tumor necrosis factor (TNF)-α and interleukin(IL)-1β. Furthermore, the result of quantitative real-time polymerase chain reaction(qRT-PCR) showed that Cd-exposure reduced the mRNA expression level of NF-E2-related factor 2 (Nrf2), heme oxygenase (HO-1), NADPH quinone oxidoreductase 1 (NQO-1), and elevated the mRNA expression level of factor-kappaB (NF-κB) p65, inducible nitric oxide synthase (iNOS) in livers. However, all these changes were dose-dependently reversed by LIM. Overall, the present findings demonstrated that LIM have the hepatoprotective effect through antioxidant and anti-inflammatory responses in Cd-exposure mice.

Systematic Investigation of the Electrochemical Properties of Natural Melanin for Various Electrode Cells

Melanin is an organic semiconductor from a broad class of functional macromolecules found in nature. It has hybrid properties of an amorphous semiconductor. However, natural melanin has not been widely studied; this is partially due to the lack of processing methods, as melanin is generally extracted and measured as a powder. Thus, better electrical methods are required; one possible solution is the use of electrochemical synthesis. We investigated the electrochemical properties of melanin at different degrees of acidity and for various electrode cells. The electrochemical properties of natural melanin were studied using two different techniques: the constant potential method and cyclic voltammetry. This could allow different types of charge transport and make melanin a contender in this rapidly growing field. Natural melanin is believed to be a hybrid conductor where the dominant charge carriers change between electrons and protons as the acidity degree and water concentration change. Biocompatible and biodegradable features make melanin useful for electrochemical energy storage and it could be an attractive candidate for applications in bioelectronics and electronics devices.

Production and evaluation of albino mutants of Sporothrix schenckii

Melanin is an important factor intrinsically related to the virulence of the Sporothrix schenckii . Mutant albino conidia are usually used as inoculants for the evaluation of the properties of melanin in experimental models for the study of sporotrichosis. The goals of this study were to analyze the presence of melanin in S. schenckii conidia, and to produce and evaluate mutant albino forms of S. Schenckii conidia. Four distinct isolates were cultured in PDA, supplemented or not with triciclazole, and in YEPD. A portion of the samples was exposed to 300 ergs/mm 2 of UV radiation to generate mutants albino forms. Following the incubation, cultures were analyzed, CFU were determined, and fragments were removed for the ultrastructural analysis, to be cultured once more in YEPD e BHI. Albino colonies were exposed to visible light; all S. schenckii isolates produced melanin, and survival and viability were 66% and 96% for albino conidia. Melanin granules were visible in the cell wall of pigmented conidia, but not in albino conidia. All conidia reverted to both the pigmented and the yeast forms, and albino colonies photoreactivated. All isolates analyzed in this study generated DHN melanin. Moreover, despite the exposure to UV radiation (300 ergs/mm 2 ) being lethal to a significant portion of the colonies, the viability and conversions to the pigmented and yeast forms in surviving colonies did not appear to be affected. Also, albino colonies photoreactivated upon exposure to visible light.

Melanin properties at the different stages towards life cycle of the fly Hermetia illucens

<p>Eumelanin type pigments are synthesized at all the stages of the life cycle of the fly Hermetia illucens: in the larvae, pre-pupae,<br />pupae and adult flies (dead flies). The greatest content of melanin was recorded in the cuticles. Melanin was present not only<br />in the cuticle, hence it remained in the cuticle after the emergence of the adult fly. It was also found in the insect body in a<br />complex with lipids. In pupae, it is mostly lauric acid that was associated with melanin. Its proportion in the melanin-chitosan<br />complex was 80%. The isolated melanin-chitosan complex of adult flies showed a wide range of antibacterial activity, inhibiting<br />the growth of 21 out of the 25 of the test cultures. The melanin-chitosan complex of empty pupal membranes and alcohol<br />suspension of pupal melanin inhibited twice as smaller number of test cultures and the above activity was absolutely in the<br />pupal chitosan. The largest zone of growth inhibition was recorded with respect to Aspergillus niger, Candida albicans,<br />salmonella, and Staphylococcus aureus. An alcohol suspension of pupal melanin inhibited the growth of 10 test cultures. In this<br />case the greatest activity was shown in relation to Mycobacterium B5 and Acinetobacter sp. 1182.</p>

Innovative materials that mimic properties of melanin

Innovative materials that mimic properties of melanin

The Unexpected Bioenergetic Function of Neuromelanin. Implications in the Biology of Learning and Memory

Progressive Recent Memory loss is the main complaint in Alzheimer’s disease patients. There is not a simple or congruous explanation yet due to highly complex mechanisms by which the Central Nervous System store and organize experiences every day, developed along 4 billion years of evolution; thereby learning and memory are poorly understood biological processes. The finding of the unsuspected intrinsic property of melanin to transforms light into chemical energy through water dissociation, as chlorophyll in plants; opens a new and wider horizon in the form in which the CNS generate and distribute chemical energy transporting it through molecular hydrogen produced by substantia nigra of mesencephalon and other pigmented structures. The mechanisms by which human modifies their behavior through learning and memory remain a mystery despite several decades of research. However, the unexpected role of melanin molecule bioenergetics of first order, very above the chlorophyll and glucose, indicates that the study of the fascinating processes involved in learning and memory several levels, needs to be started with the study of the generation and distribution of energy neuro-melanin-releasing to all the brain. In this article, we explain succinctly, the way hydrogen molecular (H2)-gas-, from the dissociation of water by the neuro melanin, moves from its source and permeates easily through the different structures of the Central Nervous System, as well as be the smaller atom, does not combine with water, moving through it in accordance with the laws of the simple diffusion. Molecular hydrogen is the main carrier of energy that nature uses in the entire universe, so that, once the neuro melanin separates it from the water, this displaces transporting its precious cargo of energy and its remarkable antioxidant capacity capable of reduce oxygen and form water.

Unsuspected Intrinsic Property of Melanin to Dissociate Water Can Be Used for the Treatment of CNS Diseases

Retinal adhesion mechanisms in mammals are quite complex and multifactorial in nature. To date, these mechanisms are incompletely understood due to a variety of chemical, physical, and physiological forces impinging upon retinal tissue: retinal pigment epithelium, nearby tissues as sclera and vitreous, the subretinal space, and the highly complex interphotoreceptor matrix that fills subretinal space. The adhesion of the retina to the choroid, rather than anatomical, is a dynamic process, as the retina detaches a few minutes after life ceases. The adhesion mechanisms described in the literature, such as intraocular pressure and the oncotic pressure of the choroid that seems to push the retina towards the choroid, the delicate anatomical relationships between the rod and cone photoreceptors, the retinal pigment epithelium, the existence of a complex material called interphotoreceptor matrix, as well as other metabolic and structural factors, still cannot explain the remarkable features observed in the adhesion mechanisms between the photoreceptor layer and retinal pigment epithelium cells. The unexpected intrinsic property of melanin to absorb light energy and transform it into chemically based free energy can explain normal adhesion of the sensory retina to the pigment epithelium. In this article, we explore and highlight this explanation, which states that it is definitely able to provide a new treatment avenue against devastating neurodegenerative properties.

БІОХІМІЧНІ ЗМІНИ В СИРОВАТЦІ КРОВІ ЩУРІВ ЗА УМОВ ЕКСПЕРИМЕНТАЛЬНОЇ ОПІКОВОЇ ХВОРОБИ ТА ЇХ КОРЕКЦІЯ МЕЛАНІНОМ

During modeling of esophageal alkali burns 1 and 2 degrees in immature rats were observed violations of various metabolic systems, melanin administration helped to normalize the biochemical parameters. It was shown that under the esophageal burns there occurred violations of protein (total protein, albumin), nitrogen metabolism (creatinine, urea) metabolism of carbohydrate (glucose) and lipids (cholesterol), changed the activity of enzymes (GOT, GPT, CC), violated fluid and electrolyte balance (K +, Na +, Cl-, Ca2 +, Mg2 +, phosphates), while the introduction of melanin contributed to the normalization of these indicators. The most effective dose were of 0.5 mg/ kg and 1 mg/kg. There were found anti-toxic properties of melanin, which may be a promising drug for the normalization of metabolism in patients with burns of esophagus and prevent its complications.