Biosynthesis of Copper Nanoparticles From Seaweed Ulva lactuca and Their In Vitro Antioxidative Potential

Marine macroalgae is consumed by individuals in several regions, including Scandinavia, Great Britain, Ireland, China, and Japan; in Japan, it is commonly referred to as aosa. Copper nanoparticles are primarily composed of copper and exhibit a size distribution ranging from 1 to 100 nm. Copper nanoparticles can be synthesized using chemical or natural means, similar to other nanoparticle variants. The nanoparticles in question have garnered significant attention owing to their historical utilization as coloring agents, as well as their contemporary applicability in medicine and antibacterial treatments.

The objective of this study was to investigate the biosynthesis of copper nanoparticles derived from Ulva lactuca seaweed and explore their in vitro antioxidative potential.

Seaweed samples (10 g) were mixed with 50 ml of distilled water and placed in a shaker for two days. Copper sulfate (10 mM) was mixed with 100 ml of distilled water to obtain a copper (Cu) solution. Cu nanoparticles were then synthesized by adding the aqueous extract to 100 ml of the Cu solution and mixing it in an orbital shaker at 180 rpm for 24 hours. They were observed both visually and via ultraviolet (UV) spectrophotometry to confirm their nanoparticle synthesis. The initial reading was performed using a UV-visible spectrometer at 300-800 nm. The sample was centrifuged at approximately 8000 rpm for 15 minutes, the pellet was removed, and the pellet was dried in a hot-air oven. The synthesized Cu nanoparticles were then investigated using in vitro antioxidant assays.

The seaweed-derived copper nanoparticles exhibited a 1.2 peak absorbance at 580 nm. Various concentrations of copper nanoparticles (25, 50, 75, and 100 µg/ml) were tested for free radical scavenging. As the copper nanoparticle concentration increased, the scavenging ability on 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radicals assay showed that the free radical scavenging activity increased in a dose-dependent manner. Similar to the DPPH assay, the total antioxidant and hydrogen peroxide (H₂O₂)assays showed increased free radical scavenging with increasing concentration.

The application of Cu nanoparticles in the synthesis process has the potential to enhance the antioxidant activity of Ulva lactuca as evidenced by the observed increase in antioxidant capacity and defense against reactive oxygen species.