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Natural melanin is a ubiquitous material that plays critical biofunctional roles in different living organisms. Scientists have dedicated significant efforts to elucidate the biofunctional roles of melanin since its discovery. It has been confirmed that natural melanin possesses a number of intriguing properties such as broadband light absorption, free-radical scavenging ability, redox activity, metal ion chelating, and electronic−ionic conductivity, enabling it to be a versatile functional material in various applications. Natural eumelanin has been the most investigated type of melanin in the past few decades and is discussed in this Review. Here we have comprehensively discussed the latest advances and associated mechanisms in emerging applications of natural eumelanin in different fields such as functional polymers, energy storage, energy conversion, photocatalysis, photothermal therapy, and wastewater treatment considering its bioinspired properties. Important applications developed based on polydopamine, which is a "eumelanin-like" material, will also be presented to give guidelines to further develop natural-melanin-based applications. Authors' perspectives on the challenges and potentials of developing natural-eumelanin-based applications will also be included. This Review provides a clear picture of the natural-eumelanin-based applications and, in turn, accelerates the expansion of the relevant emerging fields.

Post-transition liquid metals (LMs) offer new opportunities for accessing exciting dynamics for nanomaterials. As entities with free electrons and ions as well as fluidity, LM-based nanomaterials are fundamentally different from...

Gallium (Ga) compounds, as the source of Ga ions (Ga3+), have been historically used as anti-inflammatories. Currently, the widely accepted mechanisms of the anti-inflammatory effects for Ga3+ are rationalized on the basis of their similarities to ferric ions (Fe3+), which permits Ga3+ to bind with Fe-binding proteins and subsequently disturbs the Fe homeostasis in the immune cells. Here in contrast to the classic views, our study presents the mechanisms of Ga as anti-inflammatory by delivering Ga nanodroplets (GNDs) into lipopolysaccharide-induced macrophages and exploring the processes. The GNDs show a selective inhibition of nitric oxide (NO) production without affecting the accumulation of pro-inflammatory mediators. This is explained by GNDs disrupting the synthesis of inducible NO synthase in the activated macrophages by upregulating the levels of eIF2α phosphorylation, without interfering with the Fe homeostasis. The Fe3+ transferrin receptor-independent endocytosis of GNDs by the cells prompts a fundamentally different mechanism as anti-inflammatories in comparison to that imparted by Ga3+. This study reveals the fundamental molecular basis of GND–macrophage interactions, which may provide additional avenues for the use of Ga for anti-inflammatory and future biomedical and pharmaceutical applications.