Green synthesis of silver nanoparticles using Justicia adhatoda leaves extract and its anticancer effect on human lung carcinoma via induced apoptosis mechanism

In this study, Justicia adhatoda leaves extract was used to synthesize silver nanoparticles (AgNPs) and assess its anticancer attributes against human lung carcinoma (A549) cell line via induction of apoptosis mechanism. Initially, the biosynthesis of AgNPs was evident by observing the appearance of dark brown colour solution. UV–Vis spectrum showed characteristic surface plasmon resonance peak at 420 nm. FT-IR spectroscopy demonstrated the presence of distinct functional groups in both the extract and AgNPs. The peaks in XRD pattern corresponded to 101, 111, 200, and 220 crystal planes, thereby representing face-centred cubic silver. The EDX analysis confirmed the reduction of silver ions. The HR-SEM revealed spherical-shaped nanoparticles with an average size of 8–13 nm. In vitro cytotoxicity of extract and AgNPs was determined against A549 cell lines using MTT assay. The AgNPs revealed higher cytotoxity (59.25 ± 1.3–5.55 ± 1.3 %) than the extract (81.48 ± 1.3–16.66 ± 1.6 %) with reduced viabilities of cells at different concentrations. The IC50 values of the extract and AgNPs were calculated as 95.36 and 15.1 µg/mL, respectively. Apoptosis of AgNPs was analyzed using varied techniques as per the standard protocols. Acridine orange staining showed reduced green fluorescence of A549 cells due to the action of AgNPs. DNA fragmentation assay revealed the breakage of DNA double strands of cells and yielded laddered pattern. Flow cytometry analysis depicted increment in the cells count in S phase and concomitant decrement in Go/G1 phase. Quantitative real-time PCR demonstrated the upregulation and downregulation of Bax and Bcl-2 genes, respectively. Additionally, the exposure of A549 cells with AgNPs induced cytochrome C production from depolarized mitochondrial membrane into cytosol, which further upregulated caspase-9 and caspase-3 genes. In conclusion, J. adhatoda leaves-mediated AgNPs induced the apoptosis mechanism in A549 lung adenocarcinoma cells and indicated its paramount role as an effectual anticancer agent in future nanomedicine.