Melanin and Melanin-Functionalized Nanoparticles as Promising Tools in Cancer Research—A Review

SIMPLE SUMMARY: Although a notable evolution was recorded in the field of cancer, both in terms of therapeutic options and diagnostic tools, with nanotechnology contributing significantly to this direction, cancer remains one of the leading causes of death globally. In recent years, the research community has proposed novel therapeutic approaches showing promising results, such as adjoining natural compounds possessing anticancer activity and nanotechnology. A natural compound that proved to have great potential in targeted cancer therapy is melanin, a versatile biopolymer that, besides its biological properties (antioxidant, photoprotective, anti-inflammatory and antitumor), possesses intrinsic physicochemical features that make it a reliable nanotheranostic tool with pronounced impact in the oncology field. ABSTRACT: Cancer poses an ongoing global challenge, despite the substantial progress made in the prevention, diagnosis, and treatment of the disease. The existing therapeutic methods remain limited by undesirable outcomes such as systemic toxicity and lack of specificity or long-term efficacy, although innovative alternatives are being continuously investigated. By offering a means for the targeted delivery of therapeutics, nanotechnology (NT) has emerged as a state-of-the-art solution for augmenting the efficiency of currently available cancer therapies while combating their drawbacks. Melanin, a polymeric pigment of natural origin that is widely spread among many living organisms, became a promising candidate for NT-based cancer treatment owing to its unique physicochemical properties (e.g., high biocompatibility, redox behavior, light absorption, chelating ability) and innate antioxidant, photoprotective, anti-inflammatory, and antitumor effects. The latest research on melanin and melanin-like nanoparticles has extended considerably on many fronts, allowing not only efficient cancer treatments via both traditional and modern methods, but also early disease detection and diagnosis. The current paper provides an updated insight into the applicability of melanin in cancer therapy as antitumor agent, molecular target, and delivery nanoplatform.