Cadmium Telluride Quantum Dots (CdTe-QDs) and Enhanced Ultraviolet-B (UV-B) Radiation Trigger Antioxidant Enzyme Metabolism and Programmed Cell Death in Wheat Seedlings

Abstract

Nanoparticles (NPs) are becoming increasingly widespread in the environment. Free cadmium ions released from commonly used NPs under ultraviolet-B (UV-B) radiation are potentially toxic to living organisms. With increasing levels of UV-B radiation at the Earth’s surface due to the depletion of the ozone layer, the potential additive effect of NPs and UV-B radiation on plants is of concern. In this study, we investigated the synergistic effect of CdTe quantum dots (CdTe-QDs), a common form of NP, and UV-B radiation on wheat seedlings. Graded doses of CdTe-QDs and UV-B radiation were tested, either alone or in combination, based on physical characteristics of 5-day-old seedlings. Treatments of wheat seedlings with either CdTe-QDs (200 mg/L) or UV-B radiation (10 KJ/m2/d) induced the activation of wheat antioxidant enzymes. CdTe-QDs accumulation in plant root cells resulted in programmed cell death as detected by DNA laddering. CdTe-QDs and UV-B radiation inhibited root and shoot growth, respectively. Additive inhibitory effects were observed in the combined treatment group. This research described the effects of UV-B and CdTe-QDs on plant growth. Furthermore, the finding that CdTe-QDs accumulate during the life cycle of plants highlights the need for sustained assessments of these interactions.

Study of Physico-Chemical Changes of CdTe QDs after Their Exposure to Environmental Conditions

“…Derfus et al [33] reported the release of free Cd 2+ ions from cadmium selenide (CdSe) QDs in the presence of UV radiation as a consequence of QDs surface oxidation. It was found that CdTe QDs also respond to UV radiation [6,32,52,53]. UV exposure causes the release of Cd 2+ ions from the CdTe QD surface.…”

“…UV-B radiation has a wavelength range of 280-320 nm which is largely absorbed by the ozone layer, causing direct damage to DNA and cells. UV-B radiation has been found to cause the release of Cd 2+ ions from quantum dots (QDs) as a result of cadmium telluride (CdTe) QDs surface oxidation [6]. This mechanism can be used to construct a new, very simple, and completely non-demanding qualitative UV-B radiation sensor, even in places where technical equipment is not available.…”

“…In the case of ultraviolet light, photoinduced reduction of CdTe QDs size was confirmed. Typical CdTe QDs stabilised with mercaptosuccinic acid (MSA) after exposure to specific UV-B radiation at a given wavelength and energy resulted in the excitation of a system capable of generating a whole group of molecularly reactive oxidation intermediates (ROI) and reactive oxygen species (ROS) [6,33]. Due to this photodynamic effect of CdTe QDs, free cadmium ions are released.…”

Effects of He-Ne laser on nuclear F-actin under UV-B radiation

“…The day after seed germination, an irradia tion treatment was applied according to the light/dark period, as shown in the table. The enhanced UV B radiation intensity was 10.08 kJ/(m 2 day), which was obtained from UV B 313 UV fluorescent tubes (Q Panel) covered with cellulose acetate to fil ter out UV C and short wave UV B [21], which were screened in our previous work [22]. The He Ne group was treated with the He Ne laser for 2 min per day (wavelength 632.8 nm and flux irradiation den sity 5.43 mW/mm 2 ) and maintained in the dark at night to prevent the influence of stray light [23].…”

The distribution of profilin in root-tip cells of wheat seedlings exposed to enhanced UV-B radiation

“…The fluorescent images were acquired using a FV-1000 Confocal system (Olympus, Co.) with a 1.4 numerical aperture, 60× oil immersion objective lens as described by Chen et al (2014). Cell observations were performed on at least three replicate samples.…”