Cellulose circular economy: Amino-functionalized graphene quantum dots as highly sensitive vaccine indicators

Cellulose is a highly content natural polymer that can be extracted from plants. Rice straw is a valuable resource because it is rich in cellulose. This study aims to develop a technology to extract and utilize cellulose from rice straw, which would otherwise be discarded. Cellulose derived from rice straw is used to synthesize low-biotoxicity, high-performance graphene quantum dots. Cellulose is hydrolyzed into glucose and processed into graphene quantum dots using the hydrothermal method, which is a green synthetic route. The 3-(4,5-dimethylthiazol-2-yl)− 2,5-diphenyltetrazolium bromide assay shows that the natural biomass (cellulose)-derived graphene quantum dots have low biological toxicity and cell viability that exceeds 100% (48 h, 400 micrograms per milliliter). Their luminescence properties, chemical stability, and biological toxicity are significantly improved by subsequent reduction and amination. Subsequently, amino-functionalized graphene quantum dots are used as a display agent for vaccine detection, which quantified secondary antibody concentration with a detection limit of 2 pg/mL, excellent linearity (r² = 0.9982), and a low coefficient of variation of < 0.04%, outperforming the existing 3,3′5,5′-tetramethylbenzidine. This study demonstrates that graphene quantum dots synthesized from natural polymers are suitable for low-toxicity applications, such as vaccine indicators.