Eumelanin from the Black Soldier Fly as Sustainable Biomaterial: Characterisation and Functional Benefits in Tissue-Engineered Composite Scaffolds

Abstract

An optimized extraction protocol for eumelanins from black soldier flies (BSF-Eumel) allows an in-depth study of natural eumelanin pigments, which are a valuable tool for the design and fabrication of sustainable scaffolds. Here, water-soluble BSF-Eumel sub-micrometer colloidal particles were used as bioactive signals for developing a composite biomaterial ink for scaffold preparation. For this purpose, BSF-Eumel was characterized both chemically and morphologically; moreover, biological studies were carried out to investigate the dose-dependent cell viability and its influence on human mesenchymal stem cells (hMSCs), with the aim of validating suitable protocols and to find an optimal working concentration for eumelanin-based scaffold preparation. As proof of concept, 3D printed scaffolds based on methacrylated hyaluronic acid (MEHA) and BSF-Eumel were successfully produced. The scaffolds with and without BSF-Eumel were characterized in terms of their physico-chemical, mechanical and biological behaviours. The results showed that MEHA/BSF-Eumel scaffolds had similar storage modulus values to MEHA scaffolds. In terms of swelling ratio and stability, these scaffolds were able to retain their structure without significant changes over 21 days. Biological investigations demonstrated the ability of the bioactivated scaffolds to support the adhesion, proliferation and osteogenic differentiation of human mesenchymal stem cells.

Bioactive Composite Methacrylated Gellan Gum for 3D-Printed Bone Tissue-Engineered Scaffolds

“…To this aim, GGMA (2 and 4% ( w / v )) was dissolved in di H 2 O in a lower volume, containing Irgacure, and the complementary volume of BSF-Eumel, diluted in di H 2 O, was directly added to the polymer solution, to reach the final concentration of 0.3125 mg/mL. The solution was mixed at room temperature, until a uniform yellowish hydrogel was formed [ 41 ].…”

“…Thanks to a unique set of physico-chemical properties, eumelanins have found many applications as a functional biomaterial in different sectors, from organic (bio)electronics [ 33 , 34 , 35 , 36 ] to energy storage [ 37 ], photo- and radio-protection and regenerative medicine [ 38 , 39 ]. Novel insights indicate that eumelanin can specifically support bone tissue engineering [ 40 , 41 ]. Specifically, eumelanin has been highlighted to enhance the physico-chemical features of bone substitutes by stimulating stem cell and osteoblast functions and promoting the biomineralization process [ 40 ].…”

“…In a recent paper, D’Amora et al showed the great potential of the eumelanin extracted from the black soldier fly (BSF-Eumel) in the design of 3D-printed bone tissue-engineered scaffolds based on methacrylated hyaluronic acid. These scaffolds showed the ability to promote the osteogenic differentiation of human mesenchymal stem cells (hMSCs) [ 41 ]. Prompted by these positive results, the study was extended to another type of 3D-printed scaffold based on GGMA.…”

Operando Spectroelectrochemical Characterization Shows that the Dynamic Flow of Electrons through Melanin Involves Its Redox-State Switching

“…This bottom-up approach has been less successful for understanding the complex electronic properties of melanin. In fact, a “chemical disorder model” was proposed that explains the melanin’s broad and featureless absorption spectrum in terms of a heterogeneous mix of structural subunits. , Even bottom-up synthetic studies starting from well-defined precursors have yielded diverse chemically complex melanins, − leading to the suggestion illustrated in Scheme b that chemical disorder can include the monomer type; the oligomer size and structure; the electronic (i.e., redox) states; and the supramolecular organization. An alternative, top-down, experimental approach focuses on functional properties (e.g., metal binding, ,− optoelectronic , and energy storage ,, ).…”

“…Here, we used an operando approach illustrated in Scheme c to simultaneously monitor the molecular-level changes that occur when electrons are “flowing” through melanin. For these studies, we used a soluble natural melanin extracted from the cuticle of the black soldier fly (Hermetia illucens; BSF). , This BSF melanin is synthesized during insect sclerotization (i.e., hardening), and thus, its biological source and function are different from melanosome-generated melanins. Further, this BSF melanin is obtained from invertebrate biomass followed by the demineralization using acid treatment and the deproteination using a strong base treatment, which may alter its native structure .…”