Seaweed extract as a sustainable resource for Au nanoparticle synthesis and its biological and environmental applications

In this study, gold nanoparticles (AuNPs) were bio-fabricated using the water extract of marine brown seaweed Hizikia fusiformis (Hfs), commonly eaten as food in Southeast Asia, Korea, China, and Japan, and in other parts of the world. This process offers massive potential for the manufacture of new-generation nanomaterials utilizing sustainable seaweed components and explores its biological (tyrosinase, antidiabetic, antioxidant) and environmental (photocatalytic degradation of toxic industrial dyes) applications. Different spectroscopic approaches were employed to characterize and confirm the fabrication of Hfs-AuNPs. UV-Vis spectroscopy displayed the Hfs-AuNP’s surface plasmon resonance at 534 nm. The XRD result revealed the crystalline nature of the nanoparticle. According to FT-IR analysis, various phytoconstituents like polyphenols and polysaccharides from the Hfs extract contributed to the reduction and stabilization of Hfs-AuNPs. Hfs-AuNPs displayed a spherical form with a zeta potential of −18.6 mV. Notably, Hfs-AuNPs exhibited encouraging tyrosinase inhibition (31.74 % inhibition while kojic acid showed 52.40 % inhibition at 100 µg/ml), antidiabetic effect (56.38 % α-amylase activity while acarbose exhibited 61.19 % activity at 100 µg/ml), and antioxidant properties (82.89 % of DPPH scavenging while 60.04 % scavenging by BHT and 63.73 SOD effect while 61.77 % scavenging by BHT at 100 µg/ml). Besides, Hfs-AuNPs also displayed positive photocatalytic degradation of toxic industrial dyes like methylene blue (29.20 % degradation at 5 h) and methyl orange (21.26 % degradation at 3 h). The above eco-friendly, cost-effective, and sustainable synthesis method can be explored further for large-scale production and future substantial applications in therapeutic and industrial needs.