Molecular Toxicity and Mechanisms Involved in Recycled Carbon Nanomaterial Synthesis and Bioapplications: In Vitro and In Vivo

Recycled carbon materials (RCMs) represent a sustainable and high-value approach to transforming carbon-rich waste streams into functional nanostructured materials for advanced technological applications. This chapter examines the major classes of RCMs derived from biomass, plastic waste, tire waste, and industrial by-products, highlighting synthesis strategies such as pyrolysis, hydrothermal carbonization, activation processes, catalytic graphitization, and template-assisted methods. Particular emphasis is placed on the structure-property relationships governing porosity, surface chemistry, conductivity, and defect density. Beyond materials engineering, the chapter critically evaluates the molecular toxicity implications of recycled carbon nanomaterials (CNMs), including their interactions with cellular systems, oxidative stress induction, genotoxic potential, inflammatory signaling, and biodistribution patterns. Mechanistic pathways involving reactive oxygen species (ROS) generation, mitochondrial dysfunction, DNA damage, and regulated cell death are discussed in the context of both hazard identification and safe-by-design optimization. Advanced in vitro, in vivo, and high-content screening approaches for toxicological assessment are integrated to provide a comprehensive safety framework. By combining circular economy principles with mechanistic toxicology insights, recycled carbon materials are positioned as both technologically valuable and responsibly engineered materials for energy, environmental, and biomedical applications.