Property-Dependent Applications of Melanin: Comparison
View Latest Version
Please note this is a comparison between Version 2 by Catherine Yang and Version 1 by ERMINTA TSOUKO.

Melanin is among the most important natural pigments produced by various organisms, from microbes to plants and mammals. Melanins possess great properties such as radioprotective and antioxidant activity, heavy metal chelation and absorption of organic compounds. Melanin constitutes a complex polymer that can be exploited in multiple biotechnological, medicinal, and environmental sectors due to its unique properties of radioprotection, antioxidant activity, chelation of heavy metals and absorption of organic compounds.

  • eumelanin
  • pheomelanin
  • allomelanins
  • pyomelanin
  • neuromelanin

1. Absorption and Binding Capacities of Melanin and Related Properties

The radiation absorption capacity of melanin at a wide range of wavelengths within the UV and visible electromagnetic spectrum can be extremely useful in environmental applications, such as hybrid photovoltaics and photodetectors, promoting green energy [61][1]. In fact, it is proven that melanin has the capacity to diffuse almost 99% of the UV radiation that it absorbs through non-radiative media and also eliminates the reactive oxygen species (ROS) [31,61][1][2]. The high UV absorption potential of melanin derives from the absorption and scattering of light by molecules that are coupled in the melanin polymer [62][3]. The presence of melanin in the black yeast E. lecanii-corni significantly increased its resistance to elevated doses of UV-C and γ-radiation. The potential of melanin to absorb UV radiation is well demonstrated while the protective action of melanin against ionizing radiation is not well studied and understood [26][4]. The fungus Aureobasidium pullulans is well known for its capability to resist against gamma and ionizing forms of radiation. This makes it a ‘sunscreen’ of nature, which can provide multivarious applications in the cosmetic industry, including sun protection [2][5]. Additionally, Pseudomonas sp. SSA has been used for cosmetic purposes to its ability to produce extracellular melanin with enhanced UV protection properties.
Melanin can be efficiently used as a biosorbent for removal of heavy metals from aquatic territories. The integration of melanin with polymers such as polycaprolactone or polyurethane can result in the removal of up to 94% Pb in aqueous systems [2][5]. Liquid effluents that possess a heavy load of metal ions have been conventionally remediated via chemical precipitation, reverse osmosis, ion-exchange, and filtration techniques, thus these methods are efficient only in metal concentrations higher than 100 ppm. However, lower concentrations than that are also toxic and dangerous for human life. To add, it has been reported that treatment with Ca(OH)₂ and flocculants of acidic waster containing high levels of uranium in the Osamu Utsumi mine area are extremely cost intensive (from USD 200,000 to USD 250,000 at a monthly basis) [67,68][6][7]. Melanin produced via green technology, was efficiently used for the biosorption of uranium from aqueous solution. Melanin demonstrated good uptake over a wide pH range while uranium was fastly removed after 2 h of contact [68][7].
Melanogenic fungi and bacteria can be used to isolate toxins from contaminated environments. Melanin contributes to their survival in adverse environments while their ability to catabolize organic volatile compounds is enhanced. Thus, this makes them ideal microorganisms for the development of combined strategies that are based in bioprocessing and biocatalysis [69][8]. The aforementioned render melanin capable to successfully find application in bioremediation of contaminated soils and as biocatalysts in air biofilters [33][9].

2. Antimicrobial Activity

The increasing and extensive use of commercial antimicrobial agents in several applications have resulted in the widespread antimicrobial resistance of pathogens and thus scientific research seeks for novel antimicrobial agents that can deal with this alarming threat. Human infections from pathogenic bacterial and fungal strains are a problem that affects the food industry, and medical equipment since ineffective prevention of infections can lead to serious health consequences. Synthetic antimicrobial agents are characterized by high costs that burden their high-scale production while the vast majority are not environmentally friendly. Melanin has been proposed as an effective antimicrobial agent. Melanin produced from the mushroom Schizophyllum commune has been shown to have a significant contribution to reducing infection by drug-resistant pathogenic bacteria and antifungal activity against fungi of the genus Trichophyton [31][2]. Further studies have demonstrated that melanin isolated from Lachnum YM30 [70][10] and the saprophytic fungus Exidia nigricans displays enhanced antibacterial activity against pathogens such as Listeria monocytogenes, Bacillus mecillus, Staphylococcus aureus, Salmonella typhi, Vibrio parahaemolyticus and Escherichia coli. Recently, many other studies have demonstrated the antibacterial activity of microbial melanin against various pathogens, and thus it can be useful in various applications such as in biomedicine and pathology fields to prevent infections [31][2].

3. Antioxidant Activity

The molecule of melanin is still being investigated for its suitability to be used in food packaging formulations. However, studies have shown that melanin could be used to enrich fatty products such as pork lard, to further delay or prevent lipid oxidation. This effect is likely to be due to the antioxidant activity of melanin and its ability to neutralize free radicals [66][11]. The demand for natural antioxidants is constantly increasing especially after numerous scientific indications that synthetic compounds, i.e., butylated hydroxytoluene or butylated hydroxyanisole, could possess toxicity [71][12]. Melanin has attracted scientific interest due to its remarkable antioxidant activity, which is attributed to the chemical arrangement of the melanin molecule. Melanin contains both reducing and oxidizing moieties, through which it can bind free oxygen through electron exchange. The most suitable structures of melanin that can offer enhanced antioxidant capacity are eumelanins and pheomelanins [4][13]. Melanin reacts more similarly to a one-dimensional semiconductor in which free radicals are trapped by its protons [61][1]. In fact, it has been shown that microbial melanin can neutralize up to 80.9% of free radicals, which makes it much more effective than the action of synthetic melanin [31][2]. The oxidation state of melanin and other melanin-like pigments resembles the oxidation state of basic and characteristic natural antioxidants during their biosynthesis, i.e., the polyphenols and quinones [72][14]. Eumelanin produced from a recombinant E. coli strain was applied to produce hydrogels for soft contact lens dyeing presenting exceptional dyeing capacity simultaneously providing antibacterial and antioxidant activity, as well as a higher water-content rate compared to synthetic melanin-based contact lens [45][15].

4. The Case of Food Packaging Formulation

The production of biobased films for food packaging applications could effectively address several end-of-life management issues that are related to the conventional (non-degradable and fossil-based) plastics. In recent years, there has been a great interest in the production of biofilms from biopolymers. Approximately 400 million tons of plastics is produced annually, while almost 40% is used for food packaging. The preference for fossil-based packaging material arises due to their low cost compared to their biobased counterparts. However, the footprint they leave on the environment has led to a search for greener solutions [73,74,75][16][17][18]. Biofilms present enhanced physical and functional properties as a result of the enclosed bioactive compounds [76][19]. The antioxidant activity of melanin may find appealing applications in the field of health. It has been shown that the melanin pigment can counteract the pathogenic effect of hydrazane in the liver. Hydrazane is carcinogenic, so preventing its action is associated with better liver health [4][13].

4.1. Biopolymers for Food Packaging Materials

Normally, biopolymers present high gas barrier capacities, are recyclable, biodegradable, biocompatible and non-toxic, and thus they have been reported as ideal materials for food packaging applications. Cellulose is the most abundant natural polymer, with a wide range of applications due to its biocompatibility and its great film-forming capacity. Cellulose is also a great support carrier for antioxidant and antimicrobial compounds [77][20]. Chitosan is the second most plentiful polymer in nature, and it derives from crustacean chitin [78][21]. Chitosan has been reported to be suitable for edible film preparation with antibacterial activity mainly against Gram-negative bacteria. Neat chitosan-based films present a low mechanical response with poor barrier potential. The involvement of plasticizing agents and/or nanoparticles that act as crosslinking agents, i.e., ZnO and AgNPs, can improve mechanical profile of final formulations [79][22]. Sodium alginate is a polysaccharide that can be used in food packaging due to its colloidal properties, low cost, easy handling and functionalization, and biodegradability. However, it presents a poor physicochemical profile that makes it difficult to be involved in effective food packaging formulation. Supplementation of alginate films with polymers and nano-fillers can produce packaging with enhanced mechanical and barrier properties [76][19]. The study of Motelica et al. [80][23] showed that ZnO–essential oil–alginate films could extend the shelf life of cheese, offering antimicrobial properties and protection from UV light. The same scientific group demonstrated that Ag(nanoparticles)–essential oil–alginate films could offer satisfying antimicrobial protection, color, surface texture, and softness of cheese for up 14 days [81][24]. Poly(lactic acid) (PLA) is a bioplastic polyester that derives from the lactide ring polymerization. PLA presents low price and high bioavailability. It is characterized as a thermoplastic material with high rigidity and clarity that could be compared to polystyrene or poly(ethylene terephthalate) (PET). PLA can increase the tensile strength potential of biofilms simultaneously offering high composability [75,82][18][25].

4.2. Melanin Enhanced Biofilms

Melanin is a nanostructured polymer that could effectively be used in food packaging formulations. Melanin exhibit high stability to various food components such as glucose, sucrose, potassium ascorbate and ascorbic acid [4][13]. The antioxidant effect of melanin in active packaging films has been evaluated, while results showed the capacity of melanin to prevent food oxidation [76][19]. Additionally, pork lard was packaged using melanin-enriched membranes, resulting in the prevention of rotting due to fat rancidity. After enriching the packaging with melanin, free radicals were neutralized and the degree of oxidative rancidity of the product was reduced [66][11]. Studies have shown that increasing the amount of melanin nanoparticles in food packaging membranes is positively and linearly related to their antioxidant activity [74][17]. The UV-protective property of melanin is also a feature that makes it ideal for use in food packaging. In the study conducted by Bang et al. [83][26], it was demonstrated that the production of melanin-based composite films, applied in potatoes, gave the product a high degree of protection against UV radiation, especially UV-B radiation. Melanin also improved the mechanical properties of the packaging as well as the vapor and oxygen permeability and its color. Thus, to avoid spoilage of potatoes, which is a problem during storage and distribution, melanin-enriched films are a very good eco-alternative [83][26].
Roy et al. [74][17] studied carrageenan-based films, and they demonstrated that the incorporation of melanin into the films led to effective UV blocking and increased their water vapor permeability (WVP). This phenomenon was attributed to the formation of a discontinuous phase between the matrix of the carrageenan molecule and the melanin nanoparticles. Decreased values of WVP have been reported for films derived from blends of melanin and gelatin while increasing melanin concentration into the films led to decreasing WVP [84][27]. The effect of melanin on film vapor permeability values was extensively studied by Shankar et al. [84][27]. Specifically, they enriched gelatin with melanin nanoparticles (~100 nm) at concentrations within 0–1.0%. The resulting films were uniform, due to compatibility between the melanin–gelatin complex. This research showed that the melanin-enriched films had significantly improved vapor permeability and mechanical properties as well as thermal stability. The results varied depending on the melanin concentration, but their properties were better compared to control samples (without melanin) [84][27]. Carrageenan-based films fortified with melanin nanoparticles (40–160 nm) presented improved thermostability and UV absorption. The mechanical strength of the membranes increased significantly until the addition of 0.1% melanin. Finally, it was shown that the addition of melanin developed hydrophobicity and high water barrier ability of the film [74][17].
The performance of CMC membranes supplemented with melanin from the mushroom Agaricus bisporus and carvacrol, was evaluated. The developed biofilms exhibited resistance to bacterial strains including Candida albicans, Escherichia coli and Staphylococcus aureus. Also, melanin seemed to improve the antioxidant capacity, WVP, mechanical properties of the biofilms as well as their ability to protect food products against radiation. In this case, melanin did not affect the transparency of the films, even though it affected their color [73][16].
Various concentrations of fungal melanin (0.025%, 0.05% and 0.2%) were added to PLA membranes and mechanical, antioxidant, antimicrobial and UV vapor barrier properties were determined. The lowest concentration of melanin improved the barrier and mechanical properties of the films. The presence of melanin appeared to enhance the antimicrobial activity of films against Pseudomonas putida, Enterococcus faecalis and Pseudomonas aeruginosa as well as their antioxidant activity, while the UV protective properties were slightly increased. The opacity of the films was decreased with increasing melanin concentrations [75][18].
Melanin nanoparticles extracted from Pseudomonas sp. was incorporated in polyhydroxybutyric acid-based films. The produced films were homogeneous, flexible and smooth while they presented good antimicrobial activity against gram positive and negative bacteria as well as high thermostability at temperatures up to 282 °C. The addition of Pseudomonas sp. melanin to food packaging will protect products from bacterial contamination. Finally, the absorption of free radicals increased with increasing melanin concentration from 20 and 120 mg/L [85][28].

References

  1. Vahidzadeh, E.; Kalra, A.P.; Shankar, K. Melanin-Based Electronics: From Proton Conductors to Photovoltaics and Beyond. Biosens. Bioelectron. 2018, 122, 127–139.
  2. Singh, S.; Nimse, S.B.; Mathew, D.E.; Dhimmar, A.; Sahastrabudhe, H.; Gajjar, A.; Ghadge, V.A.; Kumar, P.; Shinde, P.B. Microbial Melanin: Recent Advances in Biosynthesis, Extraction, Characterization, and Applications. Biotechnol. Adv. 2021, 53, 107773.
  3. Pralea, I.-E.; Moldovan, R.-C.; Petrache, A.-M.; Ilieș, M.; Hegheș, S.-C.; Ielciu, I.; Nicoară, R.; Moldovan, M.; Ene, M.; Radu, M.; et al. From Extraction to Advanced Analytical Methods: The Challenges of Melanin Analysis. Int. J. Mol. Sci. 2019, 20, 3943.
  4. Romsdahl, J.; Schultzhaus, Z.; Cuomo, C.A.; Dong, H.; Abeyratne-Perera, H.; Hervey, W.J.; Wang, Z. Phenotypic Characterization and Comparative Genomics of the Melanin-Producing Yeast Exophiala Lecanii-Corni Reveals a Distinct Stress Tolerance Profile and Reduced Ribosomal Genetic Content. J. Fungi 2021, 7, 1078.
  5. Tran-Ly, A.N.; Reyes, C.; Schwarze, F.W.M.R.; Ribera, J. Microbial Production of Melanin and Its Various Applications. World J. Microbiol. Biotechnol. 2020, 36, 170.
  6. Coelho, E.; Reis, T.A.; Cotrim, M.; Mullan, T.K.; Corrêa, B. Resistant Fungi Isolated from Contaminated Uranium Mine in Brazil Shows a High Capacity to Uptake Uranium from Water. Chemosphere 2020, 248, 126068.
  7. Saini, A.S.; Melo, J.S. Biosorption of Uranium by Melanin: Kinetic, Equilibrium and Thermodynamic Studies. Bioresour. Technol. 2013, 149, 155–162.
  8. Blasi, B.; Poyntner, C.; Rudavsky, T.; Prenafeta-Boldú, F.X.; de Hoog, S.; Tafer, H.; Sterflinger, K. Pathogenic Yet Environmentally Friendly? Black Fungal Candidates for Bioremediation of Pollutants. Geomicrobiol. J. 2016, 33, 308–317.
  9. Cordero, R.J.B.; Vij, R.; Casadevall, A. Microbial Melanins for Radioprotection and Bioremediation. Microb. Biotechnol. 2017, 10, 1186–1190.
  10. Xu, C.; Li, J.; Yang, L.; Shi, F.; Yang, L.; Ye, M. Antibacterial Activity and a Membrane Damage Mechanism of Lachnum YM30 Melanin against Vibrio Parahaemolyticus and Staphylococcus Aureus. Food Control. 2017, 73, 1445–1451.
  11. Mattoon, E.R.; Cordero, R.J.B.; Casadevall, A. Fungal Melanins and Applications in Healthcare, Bioremediation and Industry. J. Fungi 2021, 7, 488.
  12. Carocho, M.; Morales, P.; Ferreira, I.C.F.R. Antioxidants: Reviewing the Chemistry, Food Applications, Legislation and Role as Preservatives. Trends Food Sci. Technol. 2018, 71, 107–120.
  13. Roy, S.; Rhim, J.-W. New Insight into Melanin for Food Packaging and Biotechnology Applications. Crit. Rev. Food Sci. Nutr. 2022, 62, 4629–4655.
  14. Solano, F. Photoprotection versus Photodamage: Updating an Old but Still Unsolved Controversy about Melanin: Photoprotection versus Photodamage. Polym. Int. 2016, 65, 1276–1287.
  15. Ahn, S.-Y.; Choi, M.; Jeong, D.; Park, S.; Park, H.; Jang, K.-S.; Choi, K.-Y. Synthesis and Chemical Composition Analysis of Protocatechualdehyde-Based Novel Melanin Dye by 15T FT-ICR: High Dyeing Performance on Soft Contact Lens. Dye. Pigment. 2019, 160, 546–554.
  16. Łopusiewicz, Ł.; Kwiatkowski, P.; Drozłowska, E.; Trocer, P.; Kostek, M.; Śliwiński, M.; Polak-Śliwińska, M.; Kowalczyk, E.; Sienkiewicz, M. Preparation and Characterization of Carboxymethyl Cellulose-Based Bioactive Composite Films Modified with Fungal Melanin and Carvacrol. Polymers 2021, 13, 499.
  17. Roy, S.; Rhim, J.-W. Preparation of Carrageenan-Based Functional Nanocomposite Films Incorporated with Melanin Nanoparticles. Colloids Surf. B Biointerfaces 2019, 176, 317–324.
  18. Łopusiewicz, Ł.; Jędra, F.; Mizielińska, M. New Poly(Lactic Acid) Active Packaging Composite Films Incorporated with Fungal Melanin. Polymers 2018, 10, 386.
  19. Yang, M.; Li, L.; Yu, S.; Liu, J.; Shi, J. High Performance of Alginate/Polyvinyl Alcohol Composite Film Based on Natural Original Melanin Nanoparticles Used as Food Thermal Insulating and UV–Vis Block. Carbohydr. Polym. 2020, 233, 115884.
  20. Ezati, P.; Rhim, J.-W.; Moradi, M.; Tajik, H.; Molaei, R. CMC and CNF-Based Alizarin Incorporated Reversible PH-Responsive Color Indicator Films. Carbohydr. Polym. 2020, 246, 116614.
  21. Wang, H.; Qian, J.; Ding, F. Emerging Chitosan-Based Films for Food Packaging Applications. J. Agric. Food Chem. 2018, 66, 395–413.
  22. Motelica, L.; Ficai, D.; Ficai, A.; Truşcă, R.-D.; Ilie, C.-I.; Oprea, O.-C.; Andronescu, E. Innovative Antimicrobial Chitosan/ZnO/Ag NPs/Citronella Essential Oil Nanocomposite—Potential Coating for Grapes. Foods 2020, 9, 1801.
  23. Motelica, L.; Ficai, D.; Oprea, O.; Ficai, A.; Trusca, R.-D.; Andronescu, E.; Holban, A.M. Biodegradable Alginate Films with ZnO Nanoparticles and Citronella Essential Oil—A Novel Antimicrobial Structure. Pharmaceutics 2021, 13, 1020.
  24. Motelica, L.; Ficai, D.; Oprea, O.-C.; Ficai, A.; Ene, V.-L.; Vasile, B.-S.; Andronescu, E.; Holban, A.-M. Antibacterial Biodegradable Films Based on Alginate with Silver Nanoparticles and Lemongrass Essential Oil–Innovative Packaging for Cheese. Nanomaterials 2021, 11, 2377.
  25. Garrison, T.F.; Murawski, A.; Quirino, R.L. Bio-Based Polymers with Potential for Biodegradability. Polymers 2016, 8, 262.
  26. Bang, Y.; Shankar, S.; Rhim, J. Preparation of Polypropylene/Poly (Butylene Adipate-co-terephthalate) Composite Films Incorporated with Melanin for Prevention of Greening of Potatoes. Packag. Technol. Sci. 2020, 33, pts.2525.
  27. Shankar, S.; Wang, L.-F.; Rhim, J.-W. Effect of Melanin Nanoparticles on the Mechanical, Water Vapor Barrier, and Antioxidant Properties of Gelatin-Based Films for Food Packaging Application. Food Packag. Shelf Life 2019, 21, 100363.
  28. Kiran, G.S.; Jackson, S.A.; Priyadharsini, S.; Dobson, A.D.W.; Selvin, J. Synthesis of Nm-PHB (Nanomelanin-Polyhydroxy Butyrate) Nanocomposite Film and Its Protective Effect against Biofilm-Forming Multi Drug Resistant Staphylococcus Aureus. Sci. Rep. 2017, 7, 9167.
More
© Text is available under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/)
ScholarVision Creations
Feedback