Antibacterial, antibiofilm and cytotoxic effects of Nigella sativa essential oil coated gold nanoparticles

• Essential oil of Nigella sativa based gold nanoparticles (NsEO-AuNPs) was synthesized.
• NsEO-AuNPs was characterized by UV–Vis spectrophotometer, XRD, FTIR, TEM and EDAX.
• Antibacterial and antibiofilm activity of NsEO-AuNPs was assessed against S. aureus and V. harveyi.
• Cytotoxicity of NsEO-AuNPs was tested on human lung cancer A549 cells.
• NsEO-AuNPs effectively inhibited the growth of A549 lung cancer cells.

This study reports the biological synthesis of gold nanoparticles using essential oil of Nigella sativa (NsEO-AuNPs). The synthesized NsEO-AuNPs were characterized by UV–visible spectra, X-ray diffraction (XRD), FTIR and Transmission electron microscopy (TEM). UV–vis spectra of NsEO-AuNPs showed strong absorption peak at 540 nm. The X-ray diffraction analysis revealed crystalline nature of nanoparticle with distinctive facets (111, 200, 220 and 311 planes) of NsEO-AuNPs. The FTIR spectra recorded peaks at 3388, 2842, 1685, 1607, 1391 and 1018 cm−1. TEM studies showed the spherical shape of nanoparticles and the particle size ranges between 15.6 and 28.4 nm. The antibacterial activity of NsEO-AuNPs was greater against Gram positive Staphylococcus aureus MTCC 9542 (16 mm) than Gram negative Vibrio harveyi MTCC 7771 (5 mm) at the concentration of 10 μg ml−1. NsEO-AuNPs effectively inhibited the biofilm formation of S. aureus and V. harveyi by decreasing the hydrophobicity index (78% and 46% respectively). The in-vitro anti-lung cancer activity confirmed by MTT assay on the cell line of A549 carcinoma cells showed IC50 values of bulk Au at 87.2 μg ml−1, N. sativa essential oil at 64.15 μg ml−1 and NsEO-AuNPs at 28.37 μg ml−1. The IC50 value showed that NsEO-AuNPs was highly effective in inhibiting the A549 lung cancer cells compared to bulk Au and N. sativa essential oil.

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