Core–Shell AuNPs–Chitosan Nanocomposites for Eco‐Friendly Detection of Fucoidan in Supplement Capsules

Brown algal fucoidan (FUC) has attracted significant interest as an active ingredient in various medical applications. Advancing analytical methods for FUC is essential to support the broader utilization of brown algal resources. In this research we developed an environmentally friendly sensitive fluorescent probe for FUC determination by AuNPs-chitosan core-shell nanocomposites. The prepared core-shells were visualized as uniform monodispersed spherical particles with a dense core, transparent shell and a particle distribution of 8.33 ± 2.48 nm. The colloidal solution of the nanocomposites exhibited a localized surface plasmon resonance band at around 530 nm and a blue emission peak at 394 nm after excitation at 310 nm. Owing to FUC's abundant sulfate moiety, it could interact with the positive surface charge of the prepared core-shells leading to fluorescence quenching that correlated to FUC concentration (R² = 0.991) over the range of 60-140 μg/mL with a detection limit of 11.81 μg/mL. The accuracy and precision of the prepared nanocomposites were evaluated by % recovery (98%-102%) and %RSD (< 2), respectively. Additionally, the developed method was successfully applied for FUC determination in lab-prepared capsule formulation. The environmental impact of the proposed technique was assessed using complex MoGAPI and Eco-scale showing excellent method greenness.