Synthesis of diosgenin conjugated gold nanoparticles using algal extract of Dictyosphaerium sp. and in-vitro application of their antiproliferative activities

In this study, gold nanoparticles (AuNPs) and novel gold nanoformulations loaded with diosgenin (Dio-AuNPs) were synthesized through green approach using algal extract from Dictyosphaerium sp. strain DHM2 (LC159306) as a reducing agent. AuNPs and Dio-AuNPs synthesized were characterized through UV–vis spectroscopy, zeta potential analysis, FT-IR spectroscopy, X-ray diffraction (XRD) analysis and scanning transmission electron miroscopy. An average zeta potential value of -32.4 mV indicated that AuNPs were highly stable. Fourier transmission infrared spectroscopy (FT-IR) of AuNPs showed the presence of hydroxyl groups and carbonyl groups alongwith various other capping and stabilizing functional groups. Also, in FT-IR spectrum of Dio-AuNPs characteristic peaks of both AuNPs and diosgenin were observed. XRD analysis of AuNPs and Dio-AuNPs showed that both nanostuctures exist in the crystalline form. Scanning transmission electron microscopy (STEM) studies revealed that AuNPs and Dio-AuNPs had spherical morphology with average size range of 7.9 ± 2.4 nm and 10.3 ± 2.4 nm, respectively. Moreover, in-vitro antiproliferative activities of AuNPs and Dio-AuNPs were determined on colorectal cancer cell line HCT116 and breast cancer cell line HCC1954 using sulforhodamine B (SRB) proliferation assay. Dio-AuNPs were extremely potent with GI₅₀ values of 1.03 ± 0.27 μg/mL and 1.69 ± 0.18 μg/mL in HCT116 and HCC1954 cell lines, respectively. AuNPs however, were almost 18 fold less potent as compared to Dio-AuNPs in both the cell lines. The current study has demonstrated biological synthesis, characterization and antiproliferative activities of gold nanoparticles and novel diosgenin loaded gold nanoformulations in colorectal and breast cancer cell lines and provided evidence that anticancer activities of both diosgenin and AuNPs can be enhanced many folds when used in conjugation.