Melanin nanoparticles as a promising tool for biomedical applications – a review

Caldas, Mariana; Santos, Ana Cláudia; Veiga, Francisco; Rebelo, Rita; Reis, Rui L.; Correlo, Vítor M.

doi:10.1016/j.actbio.2020.01.044

Cited by 116 publications

(71 citation statements)

References 69 publications

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“…Quite a few of these papers have reviewed melanin's chemical structure, physiochemical properties, and biomedical applications. [ 4–6 ] However, a critical review focusing on optical functions of melanin is still lacking, despite tremendous emerging work on melanin‐based photonic materials. The purpose of this review is to summarize current advances in bioinspired melanin‐based optically active materials.…”

Section: Introductionmentioning

confidence: 99%

Bioinspired Melanin‐Based Optically Active Materials

Xiao

Shawkey

Dhinojwala

2020

Advanced Optical Materials

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the properties and functions of melanin, the synthesis of melanin-like nanoparticles, and its versatile applications in catalysis, energy, and biomedical fields. Over the last 5 years, more than 1000 papers on melanin have been published annually, based on data from the Web of Science. Quite a few of these papers have reviewed melanin's chemical structure, physiochemical properties, and biomedical applications. [4-6] However, a critical review focusing on optical functions of melanin is still lacking, despite tremendous emerging work on melaninbased photonic materials. The purpose of this review is to summarize current advances in bioinspired melanin-based optically active materials. Specifically, we will cover inherent optical properties of melanin, and then summarize melanin's optical functions in nature and its optics-related applications. 2. Melanin Structure and Optical Properties Melanin has complex chemical structures that is not yet fully understood, however, it does not hinder the exploration of their optical properties. In this section, we will first discuss classifications of melanin and then summarize unique optical properties of melanin, which will be important for both understanding its biological function in nature and synthetic applications. 2.1. Classification and Structure Conventionally, all black pigments are called melanin. Recently, d'Ischia et al. suggested that any phenolic polymers that have broadband light absorption, antioxidant, and intrinsic free radical character should be characterized as melanin. [5] Exact chemical structures of melanin remain elusive, mainly due to their insolubility in solvents, close binding with other cellular tissues, and an amorphous structure. Here, we do not elaborate on the complexities of melanin's chemical structures, [7] but rather focus on its classification. Melanin can be categorized as either natural or synthetic depending on whether it was synthesized in vivo or in vitro. Both have similar macroscopic properties, but their structures are likely quite different. Natural melanin, including eumelanin, pheomelanin, and neuromelanin, is produced from a series of enzymatic reactions starting from L-tyrosine in biological systems (Figure 1). [1] In cells (commonly melanocytes), the tyrosinase oxidizes L-tyrosine to dopaquinone (DQ). If cysteine concentration in Melanin is a widespread multifunctional biological pigment that has emerged as a promising platform for applications in coating, catalysis, energy, drug delivery, and medical therapy. Melanin is also a compelling material for photonic applications because of its favorable material characteristics, including broadband absorption, high refractive index, tunable fluorescence, and UV blocking capabilities. However, there is not yet a critical review focusing on optical functions of melanin. This review summarizes current advances in bioinspired melanin-based optically active materials, covering melanin's inherent optical properties and functions both in nature and in optics-related applications. It is ...

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Section: Introductionmentioning

confidence: 99%

Bioinspired Melanin‐Based Optically Active Materials

Xiao

Shawkey

Dhinojwala

2020

Advanced Optical Materials

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“…They can be obtained and have been characterized by a variety of natural sources, including animals, plants, bacteria, and fungi [10,11,33,34]. Importantly, melanins are multifunctional and biologically-active, natural macromolecules and can be characterized as antioxidant, radioprotective, thermo-regulative, chemoprotective, antitumor, antiviral, antimicrobial, immunostimulating and/or anti-inflammatory [10,32,[34][35][36]. Potentially, melanins could be used to impart some of these important attributes to polymers.…”

Section: Introductionmentioning

confidence: 99%

Whey Protein Concentrate/Isolate Biofunctional Films Modified with Melanin from Watermelon (Citrullus lanatus) Seeds

et al. 2020

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Valorization of food industry waste and plant residues represents an attractive path towards obtaining biodegradable materials and achieving “zero waste” goals. Here, melanin was isolated from watermelon (Citrullus lanatus) seeds and used as a modifier for whey protein concentrate and isolate films (WPC and WPI) at two concentrations (0.1% and 0.5%). The modification with melanin enhanced the ultraviolet (UV) blocking, water vapor barrier, swelling, and mechanical properties of the WPC/WPI films, in addition to affecting the apparent color. The modified WPC/WPI films also exhibited high antioxidant activity, but no cytotoxicity. Overall, the effects were melanin concentration-dependent. Thus, melanin from watermelon seeds can be used as a functional modifier to develop bioactive biopolymer films with good potential to be exploited in food packaging and biomedical applications.

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“…DA has been exploited as a precursor for a biocompatible melanin-type polymer termed polydopamine (PDA) widely used for surface functionalization. Inspired by the adhesive properties of mussels, in 2007, the Messersmith group described the efficient adhesion properties of the species produced by autoxidation of DA at pH 8.5 [ 31 ] on a wide variety of materials, including organic and inorganic surfaces, providing a smart platform for secondary functionalization technologies [ 32 ]. Notably, PDA structural properties can be tailored on specific application requirements by varying the synthetic conditions (i.e., DA concentration or buffer composition) [ 33 ].…”

Section: Synthetic Melanin-like Materials: Opportunities and Issuementioning

confidence: 99%

“…In addition, they show tunable redox behavior, which confers them the role of free radical scavengers, being able to react with RONS, thus mitigating oxidative stress underlying many chronic degenerative pathologies. Their antioxidant function is particularly relevant in biomedical applications [ 32 , 48 , 49 ]. Melanin-like materials with improved antioxidant activity have been obtained by conjugating natural or synthetic melanins with other organic components, such as polymers or biopolymers.…”

Section: Synthetic Melanin-like Materials: Opportunities and Issuementioning

confidence: 99%

Melanin and Melanin-Like Hybrid Materials in Regenerative Medicine

et al. 2020

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Melanins are a group of dark insoluble pigments found widespread in nature. In mammals, the brown-black eumelanins and the reddish-yellow pheomelanins are the main determinants of skin, hair, and eye pigmentation and play a significant role in photoprotection as well as in many biological functions ensuring homeostasis. Due to their broad-spectrum light absorption, radical scavenging, electric conductivity, and paramagnetic behavior, eumelanins are widely studied in the biomedical field. The continuing advancements in the development of biomimetic design strategies offer novel opportunities toward specifically engineered multifunctional biomaterials for regenerative medicine. Melanin and melanin-like coatings have been shown to increase cell attachment and proliferation on different substrates and to promote and ameliorate skin, bone, and nerve defect healing in several in vivo models. Herein, the state of the art and future perspectives of melanins as promising bioinspired platforms for natural regeneration processes are highlighted and discussed.

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Melanin nanoparticles as a promising tool for biomedical applications – a review

Cited by 116 publications

References 69 publications

Bioinspired Melanin‐Based Optically Active Materials

Bioinspired Melanin‐Based Optically Active Materials

Whey Protein Concentrate/Isolate Biofunctional Films Modified with Melanin from Watermelon (Citrullus lanatus) Seeds

Melanin and Melanin-Like Hybrid Materials in Regenerative Medicine

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