Eco-friendly extraction of Mastocarpus stellatus carrageenan for the synthesis of gold nanoparticles with improved biological activity

Carrageenan was extracted from Mastocarpus stellatus using hot water extraction under atmospheric and pres-surized conditions. The influence of heating temperature during a non-isothermal heating profile up to temper-atures in the range 70-190 degrees C was studied to evaluate the extraction yields and properties of the carrageenan fraction. Under the selected conditions (130 degrees C), extracted carrageenan (CMs) was used for the green synthesis of gold nanoparticles (AuNPs). After the optimization of the reaction conditions, the synthesized gold nanoparti-cles (Au@CMs) were characterized by UV-Vis spectroscopy, Z potential measurements, electron microscopy, and X-ray diffraction analysis, which confirmed the formation of spherical, polycrystalline, and negatively charged nanoparticles with a mean diameter of 14.3 +/- 2.1 nm. The study conducted by scanning transmission electron microscopy, energy dispersive X-ray analysis and mapping confirmed the presence of carrageenan stabilizing AuNPs. Finally, Fourier transformed infrared spectroscopy was performed to analyze the functional groups of CMs involved in the reduction and stabilization of AuNPs. The selective cytotoxicity and the antioxidant activity of the Au@CMs were evaluated in different cell lines and compared to the CMs. Au@CMs showed an improved antioxidant capacity in cells under oxidative stress and the induction of apoptosis in a monocytic cell line, while no antitumor effect was observed in a lung endothelial cell line. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study investigated the extraction of carrageenan from Mastocarpus stellatus and its application in the green synthesis of gold nanoparticles. The synthesized gold nanoparticles exhibited good stability, negative charge, and higher antioxidant activity in cells.