Introduction:
Among the simplest nanostructures that are widely used in industry today are metallic nanoparticles. Metallic nanoparticles can bind non-destructively to single-stranded DNA, which is important in medical diagnostics.

Material and methods:
In a recent study, the structural and morphological characterization of bio-synthesized FeNPs@Calendula arvensis was performed by FT-IR and UV-vis spectroscopy and scanning electron microscopy (SEM) in which SEM images exhibited an equal and uniform spherical morphology in size of 30.13 nm.

Results:
In the antioxidant test, the IC50 values of FeNPs@Calendula arvensis and BHT against DPPH free radicals were 117 and 88 µg/ml, respectively. In the anticancer test, the cells treated with FeNPs@Calendula arvensis were assessed by MTT assay for 48 h as regards the anti-human cholangiocarcinoma and cytotoxic properties towards normal (HUVEC) and cholangiocarcinoma carcinoma cell lines, i.e. HCM-CSHL-0174-C22, CCLP-1, and QBC939. The IC50 values of FeNPs@Calendula arvensis were 196, 237, and 278 µg/ml against HCM-CSHL-0174-C22, CCLP-1, and QBC939 cell lines, respectively. The viability of the cholangiocarcinoma cell line decreased dose-dependently in the presence of FeNPs@Calendula arvensis.

Conclusions:
It appears that the anti-human cholangiocarcinoma effect of FeNPs@Calendula arvensis is due to its antioxidant effects.