# Eco-friendly synthesis of gold nanoparticles using Gracilaria gracilis with antioxidant potential and biocompatibility

## TL;DR

This paper introduces a green method to make gold nanoparticles using red algae, which are non-toxic and have antioxidant properties.

## Contribution

The first use of Gracilaria gracilis for synthesizing gold nanoparticles with proven biocompatibility and antioxidant activity.

## Key findings

- Gold nanoparticles were successfully synthesized using Gracilaria gracilis with an average size of 10.49 nm.
- The nanoparticles showed high antioxidant activity and were non-toxic to human fibroblast cells.
- FTIR analysis confirmed the presence of bioactive compounds on the nanoparticle surface.

## Abstract

Gold nanoparticles have emerged as promising materials for drug delivery systems due to their unique biological and physicochemical properties. This study presents the synthesis and biological application of gold nanoparticles using red algae (Gracilaria gracilis) for the first time, offering a cost-effective and eco-friendly method. The biosynthesized nanoparticles (NPs) were characterized using various analytical techniques, including Transmission electron microscopy (TEM), Field emission scanning electron microscopy (FESEM), Energy dispersive X-ray analysis (EDX), UV-Vis-spectroscopy, Powder X-ray diffraction (PXRD), Fourier-transform infrared spectroscopy (FTIR), and Zeta-potential analysis. The UV-Vis spectrum confirmed the successful green synthesis of gold NPs. FESEM and TEM images revealed the spherical morphology of these NPs with an average size of 10.49 nm, and they were uniformly dispersed. The high gold content was further confirmed by EDX analysis. The crystalline size of the nanoparticles, as calculated from XRD data, was about 39.5 nm. The presence of bioactive compounds on the nanoparticles’ surface was verified by FTIR analysis, which also correlated with a decrease in Zeta-potential values. The antioxidant activity was evaluated using the DPPH assay, which revealed dose-dependent radical scavenging effects. Cytotoxicity analysis demonstrated that the biosynthesized gold nanoparticles exhibited no significant toxicity toward human fibroblast cells. Furthermore, these nanoparticles showed excellent biocompatibility, indicating their potential applicability as effective alternatives in biomedical, pharmaceutical, and food industries.