Abstract
DNA sensors were assembled by consecutive deposition of thiacalix[4]arenes bearing oligolactic fragments, poly(ethylene imine), and DNA onto the glassy carbon electrode. The assembling of the layers was monitored with scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The configuration of the thiacalix[4]arene core determined self-assembling of the polymeric species to the nano/micro particles with a size of 70–350 nm. Depending on the granulation, the coatings show the accumulation of a variety of DNA quantities, charges, and internal pore volumes. These parameters were used to optimize the DNA sensors based on these coatings. Thus, doxorubicin was determined to have limits of detection of 0.01 nM (cone configuration), 0.05 nM (partial cone configuration), and 0.10 nM (1,3-alternate configuration of the macrocycle core). Substitution of native DNA with aptamer specific to aflatoxin M1 resulted in the detection of the toxin in the range of 20 to 200 ng/L (limit of detection 5 ng/L). The aptasensor was tested in spiked milk samples and showed a recovery of 80 and 85% for 20 and 50 ng/L of the aflatoxin M1, respectively.
Highlights
The determination of low-molecular compounds able to interact with native DNA has found increasing attention in the past decade due to the benefits of its possible application, e.g., monitoring of antitumor drugs, searching for new cytostatic drugs, and detection of toxins with specific DNA antibodies [1]
Lactic acid monomer was obtained from Fluka, DNA from salmon sperm, Methylene blue (MB) and Methylene green (MG), doxorubicin, poly(ethylene imine) from Sigma-Aldrich (Darmstadt, Germany)
Deposition of oligolactides 2–4 on the GCE has previously been investigated with SEM [34]
Summary
The determination of low-molecular compounds able to interact with native DNA has found increasing attention in the past decade due to the benefits of its possible application, e.g., monitoring of antitumor drugs, searching for new cytostatic drugs, and detection of toxins with specific DNA antibodies [1]. Intercalators induce deep DNA damage due to reactive oxygen species [2,3] and hydrolytic chain cleavage [4]. All of these processes disturb configuration of the DNA molecules and affect their flexibility and internal volume [5]. The formation of the complexes between DNA and low-molecular compounds is mainly monitored by specific changes in the optical characteristics of the reactants, e.g., red shift of the bands in the UV-spectrum of DNA [6], changes in circular dichroism of the complexes [7], or excitation/quenching of fluorescence [8]
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