Biogenic nanoparticles: overview of challenges in production, characterization and use.

The biological synthesis of metal-based nanoparticles (NPs) is considered a sustainable and eco-friendly alternative to conventional chemical and physical approaches, offering improved biocompatibility and a reduced environmental footprint. The synthesis and advantages have been highlighted in many studies and reviews; however, the significant challenges continue to limit their broader adoption. This review focuses on these issues within the synthesis, characterization, applications and environment concerns. Limitations such as yield, lengthy and nonuniform synthesis, purification inefficiencies, and high variability between biological sources are discussed. Characterization remains problematic, as biomolecules as capping agents or biocoronas obscure accurate size, morphology, and surface chemistry assessments. Application-specific issues also persist, including instability, inconsistent reproducibility, and uncertainties in long-term safety and toxicity. Environmental risks represent a concern that has been mostly overlooked. These include the potential for bioaccumulation in living organisms, ecological toxicity that can disrupt entire ecosystems, and the current lack of adequate disposal frameworks for nanomaterials. Together, these issues underscore the urgent need for standardized and globally consistent regulatory oversight to ensure the safe development and application of nanotechnology. By critically evaluating challenges, this review aims to guide future research toward the development of robust, reproducible, and safe protocols that will enable the reliable integration of biogenic NPs into medicine, biotechnology, and environmental applications.