Binding characteristics of aflatoxin B1 with free DNA in vitro

On-site sensing for aflatoxicosis poisoning via ultraviolet excitable aptasensor based on fluorinated ethylene propylene strip: a promising forensic tool

The environmental contamination by extremophile Aspergillus species, i.e., Aflatoxin B1, is hardly controllable in Southeast Asia and Sub-Saharan Africa, which lack handling resources and controlled storage facilities. Acute aflatoxicosis poisoning from aflatoxin-prone dietary staples could cause acute hepatic necrosis, acute liver failure, and death. Here, as the cheaper, more straightforward, and facile on-site diagnostic kit is needed, we report an ultraviolet-excitable optical aptasensor based on a fluorinated ethylene propylene film strip. Molecular dynamics on the aptamer.AFB1 complex revealed that the AFB1 to the aptamer increases the overall structural stability, suggesting that the aptamer design is suitable for the intended application. Under various influencing factors, the proposed label-free strategy offers a fast 20-min on-site fabrication simplicity and 19-day shelf-life. The one-pot incubation provides an alternative to catalytic detection and exhibited 4 times reusability. The recovery of crude brown sugar, processed peanuts, and long-grain rice were 102.74 ± 0.41 (n = 3), 86.90 ± 3.38 (n = 3), and 98.50 ± 0.42 (n = 3), comparable to High-Performance Liquid Chromatography-Photodiode Array Detector results. This study is novel owing to the peculiar UV-active spectrum fingerprint and the convenient use of hydrophobic film strips that could promote breakthrough innovations and new frontiers for on-site/forensic detection of environmental pollutants.

Efficient removal of ethidium bromide from aqueous solutions using chromatin-loaded chitosan polyvinyl alcohol composites

In this work, a novel chromatin-loaded chitosan polyvinyl alcohol composite was developed as a simple, efficient and environmentally friendly adsorbent for the efficient removal of ethidium bromide (EtBr). SEM images showed that the composites were characterized by dense porous and uniformly distributed morphology. The BET analysis showed the presence of mesopores and macropores in the composites. FTIR and XRD results showed that the chromatin was uniformly dispersed in the chitosan-polyvinyl alcohol carrier through hydrogen bonding. The fluorescence microscopy images showed the change of fluorescence effect before and after the adsorption of the material, which indicated that the chromatin was uniformly distributed in the composites and had a good adsorption effect. The optimal experimental conditions were T = 30℃, t = 120 min, pH = 7.4, m = 0.2 g when the composite with only 5% chromatin content had the ability to adsorb EtBr efficiently (minimum concentration 2 mg·L-1: adsorption rate 99%; maximum concentration 20 mg·L-1: adsorption rate 90%).The adsorption kinetics and thermodynamics showed that the EtBr adsorption kinetics of the composite conformed to the pseudo-second-order kinetic model (0.995 < R2 < 0.999) and the Freundlich isothermal model, and was a spontaneous process (ΔH < 0). This study on the immobilization of chromatin will provide a new way and reference for the application of chromatin in the treatment of EtBr pollutants.

Optimization of aflatoxin B1 removal efficiency of DNA by resonance light scattering spectroscopy

In this paper, firstly, the resonance light scattering spectra of aflatoxin B₁ (AFB₁) and DNA were measured by resonance light scattering spectroscopy (RLS), and the DNA binding saturation value (DBSV) of AFB₁ was calculated from their spectral results. Then the interaction intensity between DNA and AFB₁ and the effects of some external factors on the interaction between DNA and AFB₁ were evaluated by corresponding DBSVs, so as to establish and optimize a way for removing AFB₁ by DNA. DBSV of AFB₁ was 2.04 at 30℃ and pH 7.40. However, after adding sodium ion, calcium ion, vitamin E, vitamin C and D-glucose, DBSV of AFB₁ was changed to 2.72, 3.17, 2.67, 1.68 and 1.33 respectively. Correspondingly, the removal efficiency of AFB₁ by DNA was changed from 90.05% to 93.25%, 95.48%, 93.08%, 82.36% and 78.90% respectively. These results indicated that the external factors had a significant impact on the interaction between DNA and AFB₁. Among them, some factors enhanced the interaction between DNA and AFB₁, while some factors weakened the interaction between DNA and AFB1. The change of these external factors led to the corresponding changes in DBSV and the removal efficiency of AFB₁. DBSV of AFB₁ could really be used as an index to evaluate the intensity of the interaction between DNA and AFB₁, and to optimize the removal efficiency of AFB₁ by DNA. The experimental data also showed that the adsorption of AFB₁ to DNA was consistent with the pseudo-second-order kinetic model and the Freundlich isothermal model, was an exothermic and spontaneous process. All these results will give good references for establishing and optimizing a way of AFB₁ removal via DNA intercalation.

Establishing Linkages Among DNA Damage, Mutagenesis, and Genetic Diseases

DNA damage by chemicals, radiation, or oxidative stress leads to a mutational spectrum, which is complex because it is determined in part by lesion structure, the DNA sequence context of the lesion, lesion repair kinetics, and the type of cells in which the lesion is replicated. Accumulation of mutations may give rise to genetic diseases such as cancer and therefore understanding the process underlying mutagenesis is of immense importance to preserve human health. Chemical or physical agents that cause cancer often leave their mutational fingerprints, which can be used to back-calculate the molecular events that led to disease. To make a clear link between DNA lesion structure and the mutations a given lesion induces, the field of single-lesion mutagenesis was developed. In the last three decades this area of research has seen much growth in several directions, which we attempt to describe in this Perspective.

Gasdermin D-mediated microglial pyroptosis exacerbates neurotoxicity of aflatoxins B1 and M1 in mouse primary microglia and neuronal cultures

Aflatoxin B1 (AFB1) disrupts the blood-brain barrier by poisoning the vascular endothelial cells and astrocytes that maintain it. It is important to examine whether aflatoxin B1 or its metabolite, aflatoxin M1 (AFM1), affect microglia, which as the "immune cells" in the brain may amplify their damaging effects. Here we evaluated the toxicity of AFB1 and AFM1 against primary microglia and found that both aflatoxins decreased the viability of primary microglia and increased the leakage of lactate dehydrogenase, gamma-H2AX expression, nuclear lysis, necrosis and apoptosis in a dose-dependent manner. The potential contribution of microglia to the toxic effects of aflatoxins was assessed in transwell co-culture experiments involving microglia, neurons, astrocytes, oligodendrocytes or neural stem/precursor cells. And we found that the toxic effects of both aflatoxins on various types of nervous system cells were greater in the presence of microglia than in their absence. We also found that both aflatoxins induced gasdermin D-mediated microglial pyroptosis and inflammatory cytokine expression by activating the NLRP3 inflammasome. Blockade of gasdermin D activity in AFB1- or AFM1-treated primary microglia using dimethyl fumarate (DMF) reduced the release of IL-1β, IL-18 and nitric oxide, as well as the neurotoxicity of microglia-conditioned medium to neurons, astrocytes, oligodendrocytes and neural stem/precursor cells. These data suggested that the toxicity of AFB1 and AFM1 on various cells of the central nervous system is due, remarkably, the gasdermin D-mediated microglial pyroptosis exacerbates their neurotoxicity.

Interacting mechanism of benzo(a)pyrene with free DNA in vitro

Polycyclic aromatic hydrocarbons are environmental pollutants with strong carcinogenicity, indirect teratogenicity, and mutagenicity. This study explored the interaction mechanism of benzo(a)pyrene with free DNA in vitro by using various analytical methods. UV-vis spectra showed that benzo(a)pyrene and DNA formed a new benzo(a)pyrene-DNA complex. The thermal melting temperature of DNA increased by 12.7 °C, showing that the intercalation of benzo(a)pyrene into DNA could promote the stability of the DNA double helix structure. The intercalation of benzo(a)pyrene with DNA in vitro was further confirmed by fluorescence microscopy with magnetic beads. Fluorescence spectra showed that the interaction between DNA and benzo(a)pyrene decreased the fluorescence intensity of benzo(a)pyrene, and the maximum quenching rate was 27.89%. The quenching mode of benzo(a)pyrene was static quenching. Thermodynamic data showed that the main driving forces were van der Waals forces and hydrogen bonds, and the reaction was spontaneous. The results of this study provided a novel insight for the establishment of polycyclic aromatic hydrocarbon capture and elimination through polycyclic aromatic hydrocarbon-DNA intercalation.