Sensors and Actuators B 243 (2017) 435–444 Contents lists available at ScienceDirect Sensors and Actuators B: Chemical journal homepage: www.elsevier.com/locate/snb Assessment of CdS quantum dots effect on UV damage to DNA using a DNA/quantum dots structured electrochemical biosensor and DNA biosensing in solution Veronika Svitkova a , Jana Blaskovicova a , Monika Tekelova a , Brigitta Margit Kallai a , Teodora Ignat a , Veronika Horackova b , Petr Skladal b , Pavel Kopel c,d , Vojtech Adam c,d , Dana Farkasova e , Jan Labuda a,∗ a Slovak University of Technology in Bratislava, Faculty of Chemical and Food Technology, Institute of Analytical Chemistry, Bratislava, Slovakia b Masaryk University, Central European Institute of Technology, Brno, Czechia c Mendel University in Brno, Brno University of Technology, Brno, Czechia d Central European Institute of Technology, Brno University of Technology, Brno, Czechia e Slovak Medical University in Bratislava, Bratislava, Slovakia a r t i c l e i n f o Article history: Received 12 October 2016 Received in revised form 24 November 2016 Accepted 30 November 2016 Available online 2 December 2016 Keywords: Nanoparticles toxicity Quantum dots UV-C radiation DNA damage Biosensor Biosensing a b s t r a c t Oxidation stress induced by nanoparticles is considered to be the main mechanism of their toxicity. An evaluation of oxidative damage to DNA, one of the mostly endangered molecules, belongs to general approaches used in nanomaterials cytotoxicology. However, for spherical, biochemical and other rea- sons, they should be differences in nanoparticles behaviour using tests based on cells and pure nucleic acid substances. The goal of the work is to detect structural damage to isolated salmon sperm double stranded DNA at its exposure to UV-C radiation (254 nm) in the presence of thiol-capped CdS quantum dots of various size and fluorescence intensity. An electrochemical DNA-based biosensor composed of a glassy carbon electrode with a layered structure of chemical modifiers dsDNA and CdS QDs was pre- pared and used for the voltammetric and impedimetric evaluation of a DNA portion survived after the irradiation. The cyclic voltammetric response of the redox indicator system hexacyanoferrate(III/II) and square wave voltammetric response of the guanine and adenine moieties were measured as analytical signals. The results were verified by experiments with irradiation of DNA in the solution phase followed by voltammetric measurement of immobilized survived portion of DNA (biosensing) and by conventional agarose gel electrophoresis. Experiments showed significant effect of the fluorescent active quantum dots on the degree of DNA degradation. © 2016 Published by Elsevier B.V. 1. Introduction Quantum dots (QDs) are semiconductor nanocrystals with the size ranging from 2 to 100 nm with advantageous physical and chemical properties of different kind such as unique optical and electrical properties, bright and stable fluorescence, and size dependent photoluminescence due to the extent of their energy band gap [1,2]. Therefore, QDs are used as imaging and diagnos- tic biomedical agents [3]. Bioconjugated QDs are explored as a tool for site specific gene and drug delivery. On the other hand, under certain conditions QDs may pose environmental and human health ∗ Corresponding author. E-mail address: jan.labuda@stuba.sk (J. Labuda). risks as determined by rodent animal models and in vitro cell cul- tures [4]. In particular, an effect of size of the nanoparticles on their biological activity is of permanent interest in toxicological investi- gations [5–8]. As general toxicity criteria for QDs do not exist, their toxicity parameters must be determined for each QDs-cell system according to the concentration, time, material, size, shape, coating, environment and experimental conditions [9]. In aerobic conditions the photoactivated QDs can non- radiatively transfer their energy to proximal molecular oxygen under the formation of singlet oxygen, which will then produce reactive oxygen species (ROS) like superoxide anion, hydroxyl rad- ical, and hydrogen peroxide [10–12]. The oxidation of chemisorbed water can also generate hydroxyl radicals. QDs surface determines the number of trap states affecting electron-gap recombination and thus the charge transfer [13]. CdS [11], CdSe/ZnSe [14], CdSe/ZnS http://dx.doi.org/10.1016/j.snb.2016.11.160 0925-4005/© 2016 Published by Elsevier B.V.