METHODS: AgNP-K 1:1 was synthesized with 1 mM kaempferol, whereas AgNP-K 1:2 with 2 mM kaempferol. The characterization of AgNP-K 1:1 and AgNP-K 1:2 was performed using UV-visible spectroscopy (UV-Vis), Zetasizer, transmission electron microscopy (TEM), scanning electron microscopy-dispersive X-ray spectrometer (SEM-EDX), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy. The antibacterial activities of five samples (AgNP-K 1:1, AgNP-K 1:2, commercial AgNPs, kaempferol, and vancomycin) at different concentrations (1.25, 2.5, 5, and 10 mg/mL) against MRSA were determined via disc diffusion assay (DDA), minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) assay, and time-kill assay.
RESULTS: The presence of a dark brown colour in the solution indicated the formation of AgNP-K. The UV-visible absorption spectrum of the synthesized AgNP-K exhibited a broad peak at 447 nm. TEM, Zetasizer, and SEM-EDX results showed that the morphology and size of AgNP-K were nearly spherical in shape with 16.963 ± 6.0465 nm in size. XRD analysis confirmed that AgNP-K had a crystalline phase structure, while FTIR showed the absence of (-OH) group, indicating that kaempferol was successfully incorporated with silver. In DDA analysis, AgNP-K showed the largest inhibition zone (16.67 ± 1.19 mm) against MRSA as compared to kaempferol and commercial AgNPs. The MIC and MBC values for AgNP-K against MRSA were 1.25 and 2.50 mg/mL, respectively. The time-kill assay results showed that AgNP-K displayed bacteriostatic activity against MRSA. AgNP-K exhibited better antibacterial activity against MRSA when compared to commercial AgNPs or kaempferol alone.
METHODS: AgNP-SC was synthesised by reducing silver nitrate with an aqueous extract of S. crispus, with nanoparticle formation indicated by the appearance of a dark brown colour. Cytotoxicity was assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Apoptotic changes were examined through acridine orange/propidium iodide (AO/PI) staining, while cell cycle distribution was analysed using flow cytometry. Gene expression of apoptotic markers was analysed using reverse transcription polymerase chain reaction (RT-PCR).
RESULTS: MTT analysis demonstrated a significant, concentration-dependent decrease in CT26 cell viability following AgNP-SC treatment, with cell viability reduced to below 50% at concentrations ≥ 25 μg/mL (P < 0.05). AO/PI staining revealed classical apoptotic features, including chromatin condensation, membrane blebbing, and nuclear fragmentation. Flow cytometric analysis showed a significant accumulation of cells in the G1 phase accompanied by a marked reduction in the S-phase population in treated groups compared to untreated controls (P < 0.05), indicating G1 cell cycle arrest and inhibition of DNA synthesis. RT-PCR analysis further demonstrated significant upregulation of pro-apoptotic genes (CED-3 and CED-4) and downregulation of the anti-apoptotic gene CED-9 (P < 0.05), confirming activation of the intrinsic mitochondrial apoptotic pathway.
CONCLUSION: Green-synthesised AgNP-SC exhibits potent anticancer properties, suggesting its potential as a natural-based nanotherapeutic agent for colon cancer. Further in vivo and mechanistic studies are warranted to validate its therapeutic efficacy.