Introduction to exploring the progress in fundamental, functional material and health aspects of melanins and related materials

A. Bernardus Mostert

Bernard Mostert is a materials scientist working on conductive biomaterials and bioelectronic devices. He received his PhD in physics at the University of Queensland. He has held postdoctoral research positions at Lancaster University, the University of Queensland and Swansea University. He has also been a recipient of the prestigious Marie Skłodowska-Curie fellowship. His specialty is understanding the charge transport mechanisms of biomaterials and devices as they are affected by the environment. He has over a decade of experience in pioneering hydration control experiments in diverse areas including both material and device electrical characterization, neutron and muon scattering and magnetic resonance measurements.

Pooi See Lee

Pooi See Lee is the President Chair's Professor in Materials Science & Engineering at Nanyang Technological University (NTU), Singapore. She received her PhD in materials science from the National University of Singapore in 2002 and she joined Nanyang Technological University, Singapore, in 2004. Her current research focuses on developing stretchable elastomeric composites for electronics and energy devices, the human–machine interface, sensors and actuators, hybrid materials for soft robotics. She was elected as the MRS Fellow 2022, Fellow of the Royal Society of Chemistry 2022, and the National Academy of Inventors Fellow in 2020.

Carlos F. O. Graeff

Carlos F. O. Graeff received his PhD in physics from the State University of Campinas (UNICAMP) in 1994. After a post-doctorate at TU München with an Alexander von Humboldt Foundation Fellowship, he joined the University of São Paulo (USP), Campus Ribeirão Preto, as assistant (1996–1999) and then associate professor (1999–2006). In 2006 he joined the State University of São Paulo (UNESP) as a full professor. He is Coordinator of Strategic Programs and Research Infrastructure in FAPESP; Fellow of the Royal Society of Chemistry; a member of the advisory board of Journal of Materials Chemistry C, Materials Advances and RSC Applied Interfaces (Royal Society of Chemistry); and member of Academia de Ciências do Estado de São Paulo (ACIESP). His field of interest is materials science, more specifically electronic devices (solar cells, thin-film transistors, etc.), biomaterials/bioelectronics and electronic magnetic resonance.

There is a growing interest in a broad class of biomaterials known as the melanins, due to their intriguing physico–chemical properties as well as their implications for biological health and medical applications and devices.

This themed collection highlights a diverse set of research work on both fundamental and applied perspectives on melanin and related poly indolequinone materials, within the context of innovative developments across multiple fields.

First, Paulin et al. highlight the effectiveness of a multifrequency electron paramagnetic resonance approach in elucidating the origin of eumelanin's paramagnetism (https://doi.org/10.1039/D3MA01029E). This review offers a comprehensive understanding of the paramagnetic nature of eumelanin from a multi-species perspective.

Ferraiuolo et al. investigated the Seebeck coefficient of the eumelanin with PEDOT:PSS blends by means of electron paramagnetic resonance measurements and elucidated the role of eumelanin pigments as radical dopants for thermoelectric applications (http://doi.org/10.1039/D4MA00339J).

Kim et al. follow by providing important insights into the redox activities of melanin (https://doi.org/10.1039/D3MA01161E). They highlight its complexity in context-dependent behavior and underscore melanin's potential in bioelectronics and medical fields.

Heppner et al. present a theoretical study on the electronic and optical properties of poly indolequinone eumelanin (https://doi.org/10.1039/D4MA00192C). Their study emphasizes the fine-tune tailoring of eumelanin derivatives with halogen and electron-donating groups, towards new possibilities for their use as sustainable and high-performance materials.

Soltani et al. showed an in silico approach to evaluate the allosteric binding between eumelanin and drug molecules (https://doi.org/10.1039/D4MA00246F). The study underscores the complex nature of drug-eumelanin interactions and highlights the importance of multiple factors in developing drug-delivery systems to improve the efficacy of health treatments.

The final article explore the chemical composition of the black soldier fly eumelanin (https://doi.org/10.1039/D4MA00825A). The authors demonstrate the presence of the dihydroxyindole carboxylic acid moiety within the polymer. For most eumelanins this is de jure, but a completely unexpected development for an insect-based eumelanin. This observation suggests a different chemical mechanism of formation within the black soldier fly, and also that black soldier fly eumelanin is a potential material for radical scavenging and conductivity applications.

Conclusion

We believe that exploring these insightful papers from various research domains will help readers recognize the vast scope of research being conducted on eumelanin and related materials, as well as be an inspiration for new applications and innovations in both industrial and healthcare contexts. We extend our gratitude to our colleagues worldwide for their contributions to this versatile and eco-friendly class of materials and trust that you, the reader, will find this themed collection enjoyable and enlightening.

---