Nano-silymarin provides protection against γ-radiation-induced oxidative stress in cultured human embryonic kidney cells

•Nano-silymarin size estimated from Transmittance electron microscopy was 3–8 nm.•Maximum plasmid DNA protection revealed at 10 μg/mL of nano-silymarin by retention of supercoiled form.•Toxicity reduction of nano-silymarin was seen by MTT, micronuclei reduction and DIC microscopy.•Nano-silymarin also helps in reduction of free radicals and normal progression of cell cycle.

Radiation can produce biological damage, mainly oxidative stress, via production of free radicals, including reactive oxygen species (ROS). Nanoparticles are of interest as radioprotective agents, particularly due to their high solubility and bioavailability. Silymarin is a hepatoprotective agent but has poor oral bioavailability. Silymarin was formulated as a nanoemulsion with the aim of improving its bioavailability and therapeutic efficacy. In the present study, we evaluated self-nanoemulsifying drug delivery systems (SNEDDS) formulated with surfactants and co-surfactants. Nano-silymarin was characterized by estimating % transmittance, globule size, and polydispersity index, and by transmission electron microscopy (TEM). The nano-silymarin obtained was in the range of 3–8 nm diameter. With regard to DNA damage, measured by a plasmid relaxation assay, maximum protection was obtained at 10 μg/mL. Cytotoxicity of nano-silymarin to human embryonic kidney (HEK) cells was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay. Protective efficacy against γ-radiation was assessed by reduction in micronucleus frequency and ROS generation, using the 2′,7′-dichlorodihydrofluorescein diacetate (H2DCFDA) assay. Radiation-induced apoptosis was estimated by microscopic analysis and cell-cycle estimation. Nano-silymarin was radioprotective, supporting the possibility of developing new approaches to radiation protection via nanotechnology.