Anticancer prospects of silver nanoparticles green-synthesized by plant extracts

Silver nanoparticles (AgNPs) were synthesized via a green strategy using fifty-eight plant extracts that originated from Vietnam and Indonesia. Among the fifty-eight AgNP samples, we selected six AgNP samples synthesized by the extracts of Areca catechu, Hypotrachyna laevigata, Ardisia incarnata, Maesa calophylla, Maesa laxiflora and Adinandra poilanei. Remarkably, these six extracts exhibited higher 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity and reducing power than the other extracts. Furthermore, the contents of total phenolic compounds and reducing sugars in the six selected extracts were also higher than those in the other extracts. The six selected AgNP samples showed strong surface plasmon resonance in the range of 416-438 nm. They were all spherical shaped with an average size from 12.5 ± 1.0 nm to 21.3 ± 4.9 nm as measured by field-emission transmission electron microscopy images. The hydrodynamic sizes were measured to be 49.5-122.6 nm with negative zeta potential values. Colloidal stability was excellent on the shelf for 28 days and in cell culture medium. The cytotoxicity assessment and generation of reactive oxygen species (ROS) in A549 and HeLa cells demonstrated that the AgNP samples prepared by Ardisia incarnata, Maesa calophylla, and Maesa laxiflora showed relatively high cytotoxicity and excess ROS generation among the six selected AgNP samples. Exposure of the AgNP samples to A549 and HeLa cells resulted in cell death, which was mostly due to necrosis but slightly due to late apoptosis. Cell cycle analysis demonstrated a significant increase in the cell population in the S phase. The green-synthesized AgNPs induced cell death, suggesting anticancer prospects that may offer new insight into the development of an anticancer nanomedicine.

Keywords: Apoptosis; Cell cycle; Cytotoxicity; Green synthesis; Necrosis; Reactive oxygen species; Silver nanoparticles.