Lignin and cellulose-based functional carbon dots synthesized from waste agricultural residues for sustainable food packaging applications: A review

Lignin and cellulose-derived carbon dots (Lig/CL-CDs) synthesized from agricultural residues have recently emerged as a promising class of sustainable nanomaterials for food packaging and sensing applications. These carbon-based nanodots are frequently reported in the literature as economically favorable alternatives because of the use of abundant biomass precursors and relatively mild synthesis conditions. Several studies have reported the relatively low cytotoxicity of biomass-derived carbon dots commonly used in vitro cell models under specific experimental conditions. However, their long-term biological safety and dose-dependent effects necessitate further investigation. When incorporated into polymer matrices, Lig/CL-CDs have demonstrated the ability to enhance packaging performance by improving mechanical strength, thermal stability, gas and moisture barrier properties, while enabling intelligent functions such as fluorescence-based freshness sensing and active antimicrobial preservation. Recent studies have reported the synthesis of Lig/CL-CDs from diverse biomass sources, including RH, coconut husk, banana peel, orange peel, sugarcane bagasse, wheat straw, and tea residues with additional performance tuning achieved through heteroatom doping and metal nanoparticle co-doping strategies. This review critically summarizes the precursor chemistry, synthesis route, surface functionalization and structure-property relationships of Lig/CL-CDs derived from agricultural wastes with a particular emphasis on their integration into food packaging systems. Importantly, food safety aspects, including migration behavior from polymer matrices, in vitro toxicological evidence and current regulatory considerations for food-contact materials are discussed in detail. This review further highlights key challenges, and research gaps related to long-term safety, scalability and regulatory approval providing future perspectives for the responsible development of Lig/CL-CD-based sustainable food packaging technologies.