In-vitro Study on the Synthesis of Seaweed Ulva fasciata Generated Nanoparticles and Its Cytotoxicity Effect on Selected Continuous Cell Lines

Aim: To examine the effect of gold nanoparticles on normal Vero cell lines as well as on three different cancer cell lines (HepG2, HeLa, and MCF7) to evaluate their safety and toxicity. The study aims to assess the biocompatibility and potential cytotoxicity of gold nanoparticles, considering the ongoing debate about their effects on human health. Study Design: Experimental in vitro study. Place and Duration of Study: This study was conducted at P.G. and Research Department of Biotechnology, Marudupandiyar college, Thanjavur Methodology: In this study, Ulva fasciata seaweed was collected from coastal regions of Kerala and Tamil Nadu, cleaned, shade-dried, and powdered for methanolic extraction using Soxhlet apparatus. The resulting extract was used for the phytosynthesis of gold nanoparticles (Au NPs) by reacting with 1 mMH AuCl₄ under dark, static conditions at room temperature. Phytochemical screening identified various bioactive compounds in the extract. Optimization of nanoparticle synthesis was carried out by varying pH, temperature, extract and metal salt concentrations, and incubation time, with stability assessed over 12 months. The Au NPs were characterized using techniques such as UV–vis spectroscopy, HRTEM, EDX, XRD, DLS, zeta potential, AFM, and ICP-OES. Cytotoxic effects of the Au NPs were evaluated via MTT assay against normal (Vero) and cancer (HepG2, HeLa, MCF7) cell lines to determine IC50 values, and apoptosis in HepG2 cells was confirmed using PI and AO/EB staining under fluorescence microscopy. Results: Phytosynthesized gold nanoparticles (Au NPs) using Ulva fasciata extract exhibited a characteristic UV-Vis absorbance peak at 545 nm, confirming their formation. Phytochemical analysis of the extract revealed the presence of various bioactive compounds such as alkaloids, phenolics, flavonoids, and terpenoids, which likely mediated the nanoparticle synthesis. Optimal synthesis conditions were determined as pH 7, 1.0 mM HAuCl₄, 1.0 mL extract, 37°C, and 24-hour incubation. Characterization revealed predominantly spherical, crystalline Au NPs with a size range of 25–35 nm by HR-TEM, a maximum hydrodynamic diameter of 50 nm (DLS), and a zeta potential of -16.0 mV, indicating good stability. XRD confirmed face-centered cubic structures, and EDX and SAED affirmed elemental purity and crystallinity. AFM showed smooth, spherical particles (~60–90 nm), and ICP-OES quantified Au NP concentration at 258.0 mg/L. In vitro cytotoxicity tests demonstrated higher biocompatibility of Au NPs (IC₅₀: 75µg/mL) compared to gold chloride (IC₅₀: 10µg/mL) in Vero cells. Au NPs showed dose-dependent anticancer activity, with IC₅₀ values of 30µg/mL (HepG2) and 50µg/mL (HeLa and MCF7). Fluorescent staining of HepG2 cells revealed apoptotic features, including chromatin condensation and nuclear fragmentation, confirming the pro-apoptotic effects of the Au NPs. Conclusion: Gold nanoparticles show promise as a non-toxic drug delivery vehicle in normal cells while exhibiting cytotoxic effects in cancer cell lines. These findings suggest potential for selective therapeutic applications, though further studies are needed to confirm long-term safety and efficacy.