Novel nanocomposite materials of silver-exchanged clinoptilolite with pre-concentration of Ag(NH₃)₂⁺ in water possess enhanced anticancer action

Abstract

The optimal conditions of sorption of Ag(NH₃)₂⁺ ions under the dynamic conditions by the Transcarpathian clinoptilolite (Western Ukraine) were: temperature of clinoptilolite thermal pre-treatment—150 °C; sorbent grain diameter—0.20 to 0.31 mm; flow rate of Ag(I) solution with the concentration of 1.0 µg mL⁻¹ through the sorbent—3 mL min⁻¹; concentration of NH₃—0.05 mol L⁻¹; pH 10.8. The sorptive capacity value of clinoptilolite under the optimal conditions is 4.1 mg of Ag per 1 g of zeolite. The best desorbent of Ag(I) from clinoptilolite is 3.5 M HNO₃. This desorbent removes 100% of sorbed Ag(I). The solid-phase extraction procedure with clinoptilolite was used to pre-concentrate trace amounts of silver ions in water-ammonia solutions to be finally determined by the atomic absorption method. The proposed method allows to pre-concentrate trace amounts of Ag(NH₃)₂⁺ from solutions with a high content of Cl⁻ ions and other macro-components of natural waters. The linearity of the proposed method was evaluated in the range of 1.2–400 ng mL⁻¹ with the detection limit 0.4 ng mL⁻¹. The intact clinoptilolite and its composites with silver were used for the treatment of human tumor cells (HepG2, HCT116, КB3-1 lines) and pseudonormal cells (human HEК293 cells and murine J774.2 cells). Silver doping increased cytotoxicity of the intact clinoptilolite, while thermal (500 °C, 2.5 h) pretreatment of silver-containing clinoptilolite decreased its cytotoxicity. These effects depended on tissue origin of the treated cells. Ag(NH₃)₂⁺-zeolite was more toxic comparing with zeolite treated with aqueous NH₃ for all studied mammalian cells.