Synthesis, characterization and biomedical investigation of gold nanoparticles with bay leaf (laurus nobilis L.) extract

In this study, gold nanoparticles (AuNPs) were synthesized using Laurus nobilis L. (bay leaf) extract via a green synthesis approach and comprehensively characterized. Three concentrations of HAuCl₄ (1 mM, 2,5 mM, 5 mM) and four extract ratios (10%, 30%, 50%, 80%) were employed, resulting in 12 different reaction combinations. UV-Vis spectroscopy revealed that the most intense and narrow surface plasmon resonance (SPR) band occurred in the 1 mM HAuCl₄ + 30% extract system. The synthesis was repeated at pH 3, 7, 11, and the natural pH of the extract, and both pH 7 and the extract's natural pH resulted in similarly small particle sizes (~70 nm) and high electrostatic stability (approximately −18 mV). However, the synthesis performed at the natural pH of the extract, without the need for any additional pH-adjusting chemicals, offers a more environmentally sustainable approach. TEM and SEM images indicated that most AuNPs exhibited spherical morphology in the range of 10-100 nm, with some irregular crystalline structures also observed. EDX analysis detected not only gold but also carbon, oxygen, nitrogen, chlorine, and potassium, suggesting the presence of an organic coating derived from the plant extract. FTIR spectra further supported this finding, identifying phenolic, aliphatic, and aromatic functional groups on the nanoparticle surface. In addition, the anticancer potentials of the bay leaf extract and the synthesized gold nanoparticles were evaluated through in vitro cytotoxicity and wound healing assays. Notably, in SH-SY5Y cells, a significant cytotoxic effect was observed with a cell viability rate of 22,99%. Furthermore, the bay leaf extract and the nanoparticle form promoted wound healing by 43,40% and 21,88%, respectively, indicating remarkable biological activity. All these findings clearly demonstrate that gold nanoparticles derived from Laurus nobilis possess multifunctional characteristics and represent advanced nanomaterials with therapeutic potential in biological systems, offering a strong and sustainable alternative for biomedical applications.