The combined toxicity of ultra-small SiO2 nanoparticles and bisphenol A (BPA) in the development of zebrafish

Sensitivity and reusability of a simple microbial fuel cell-based sensor for detecting bisphenol A in wastewater

Polycarbonate plastic processing wastewater contains high concentrations of bisphenol A (BPA), requiring a real-time technology to monitor wastewater containing BPA. Since the activity of electrogenic microorganisms on the anode surface of the microbial fuel cell (MFC) sensor is inhibited by exposure to contaminants, the toxicity of contaminants in wastewater can be determined by observing the variation in voltage output from the MFC sensor. The simple MFC sensor that is developed in this work exhibited a significant decrease in voltage output in BPA-containing wastewater concentration of 5-100 mg/L. Sensitivity analysis revealed that the voltage change (ΔV) was strongly correlated with the BPA concentration, with R² as high as 0.97. This study was the first to investigate the number of repeated uses of the MFC sensor, using sodium acetate as the regeneration solution for the MFC sensor, leading to a successful recovery of detection performance. However, as the number of uses increased (up to the third or fourth use), the ΔV of the MFC sensor for BPA gradually decreased and the sensitivity decreased significantly from 0.238 mV/mg/L to 0.027 mV/mg/L. In the low BPA concentration range (≦20 mg/L), the MFC sensor can be reused up to 5 times, demonstrating that the proposed MFC sensor can be reused. Microorganisms contribute to the power generation of the MFC sensor, which can be exploited in the detection of pollutants, enabling the determination of wastewater toxicity and providing early warnings of thereof. Conventional MFC sensors are complex and lack the ability to explore repeated use, so they are not easily applied to actual wastewater detection. The proposed MFC sensor has many advantages such as simplicity, rapid detection, and reusability, solving the problem of the high cost of using disposable MFC sensors and making them feasible for practical use.

Characterization and preliminary safety evaluation of nano-SiO2 isolated from instant coffee

The physiological and toxicological evaluation of nano-silicon dioxide (nano-SiO2) particles in food is important for ensuring food safety. In this study, nano-SiO2 particles isolated from five brands of instant coffee, were structurally characterized using transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, dynamic light scattering, and zeta potential analyses. Their toxicity was assessed by measuring cell viability, membrane integrity, and reactive oxygen species (ROS) levels in model gastrointestinal cells (GES-1 and Caco-2). Additionally, mortality, deformity rate, heart rate and death of whole zebra fish embryos were measured. The five types of nano-SiO2 samples comprised amorphous particles with a purity of approximately 99%, which met the food additive standard. Considering that the original particle size ranged from 10 to 50 nm, the samples were classified as nano-SiO2 food additives. Nano-SiO2 did not significantly impact the activity of GES-1 or Caco-2 cells, and no significant cell membrane damage was observed (Caco-2 cells exhibited mild micro damage); however, a slight increase in intracellular RPS levels was detected. Moreover, nano-SiO2 was found to cause head deformity, pericardial edema, yolk sac edema and tail bending. Collectively, the results show that nano-SiO2 time- and dose-dependently affects GES-1 and Caco-2 cell viability, as well as the mortality, heart rate, and abnormality rate of zebra fish embryos. Specifically, a high concentration (≥ 200 μg/mL) and long exposure time (≥ 48 h) of food additive nano-SiO2 affected GES-1, Caco-2 cells, and the gastrointestinal tract in zebra fish embryos.