The effects of magnetic fields exposure on relative permittivity of saline solutions measured by a high resolution SPR system

Improving microbial production of value-added products through the intervention of magnetic fields

The magnetic field application is emerging as an auxiliary physical strategy to facilitate rapid biomass accumulation and intracellular production of compounds. However, the underlying mechanisms and principles governing the application of magnetic fields for microbial growth and biotransformation are not yet fully understood. Therefore, a better understanding of interdisciplinary technologies integration, expanded magnetic field application, and scaled-up industrial implementation is crucial. In this review, the magnetic field characteristics, magnetic field-assisted fermentation devices, and the working mechanism of magnetic field have been reviewed comprehensively from both physical and microbiological perspectives. The review suggests that magnetic fields affect the biochemical processes in microorganisms by mediating nutrient transport across membranes, electron transfer during photosynthesis and respiration, enzyme activity and gene expression. Moreover, the recent advances in magnetic field application for microbial fermentation and conversion in biochemical, food and agricultural fields have been summarized.

Probing Biosensing Interfaces With Single Molecule Localization Microscopy (SMLM)

Far field single molecule localization microscopy (SMLM) has been established as a powerful tool to study biological structures with resolution far below the diffraction limit of conventional light microscopy. In recent years, the applications of SMLM have reached beyond traditional cellular imaging. Nanostructured interfaces are enriched with information that determines their function, playing key roles in applications such as chemical catalysis and biological sensing. SMLM enables detailed study of interfaces at an individual molecular level, allowing measurements of reaction kinetics, and detection of rare events not accessible to ensemble measurements. This paper provides an update to the progress made to the use of SMLM in characterizing nanostructured biointerfaces, focusing on practical aspects, recent advances, and emerging opportunities from an analytical chemistry perspective.

Characterization and Sensing of Inert Gases with a High-Resolution SPR Sensor

It is generally difficult to characterize inert gases through chemical reactions due to their inert chemical properties. The phase interference-sensing system based on high-resolution surface plasmon resonance (SPR) has an excellent refractive index detection limit. Based on this, this paper presents a simple and workable method for the characterization and detection of inert gases. The phase of light for the present SPR sensor is more sensitive to the change in the external dielectric environment than an amplitude SPR sensor. The limit of detection (LOD) is usually in the order of 10⁻⁶ to 10⁻⁷ RIU, which is superior to LSPR (Localized Surface Plasmon Resonance) sensors and traditional SPR sensors. The sensor parameters are simulated and optimized. Our simulation shows that a 36 nm-thick gold film is more suitable for the SPR sensing of inert gases. By periodically switching between the two inert gases, helium and argon, the resolution of the system is tested. The SPR sensing system can achieve distinguishable difference signals, enabling a clear distinction and characterization of helium and argon. The doping of argon in helium has a detection limit of 1098 ppm.

The decreased permittivity of zebrafish embryos culture medium by magnetic fields did not affect early development of zebrafish embryos

Epidemiological studies have shown associations between exposure to environmental extremely low frequency magnetic fields (ELF-MF) and health effects, but the mechanisms of ELF-MF induced biological effects remain unclear. We hypothesized that ELF-MF may regulate functions of tissues or cells via its effects on surrounding environment, e.g., culture medium. To test this hypothesis, we investigated the effects of 50 Hz MF on the relative permittivity of zebrafish embryos culture medium as well as of MF-exposed medium on zebrafish embryos development. The responses of medium to 50 Hz MF exposure were evaluated by a phase-sensitive surface plasmon resonance (SPR) system. The results demonstrated that MF treatment decreased relative permittivity of zebrafish embryos medium in a dose and time-dependent way. Interestingly, the decreased permittivity induced by MF exposure gradually recovered and approached to the base level when the exposure was removed off. However, MF-exposed medium did not trigger adverse consequences of embryos during zebrafish embryonic development, including mortality, malformation, hatching and heart rate when the MF pre-exposed medium was subjected to one cell-stage embryos. Moreover, the MF-exposed medium did not induce apoptosis of zebrafish embryos at 48 and 72 h post fertilization. Our data demonstrated that the relative permittivity of zebrafish embryos medium was decreased by MF exposure, whereas this decrease failed to result in abnormal development of zebrafish embryos.

The Relative Permittivity Changes of EGF by 50 Hz MF Exposure Neither Affect the Interaction of EGF With EGFR Nor Its Biological Effects

The biophysical mechanism of magnetic fields (MFs) acting on living systems is not clear. Previous research showed that, similar to epidermal growth factor (EGF), MF exposure induced EGF receptor (EGFR) clustering and activated EGFR signaling. In this study, we investigated whether MF exposure induced the changes in physical characteristics of EGF and downstream effects of EGF and EGFR interaction. The phase-interrogation surface plasmon resonance (SPR) sensing analyses showed that 50 Hz MF exposure at 4.0 mT for 1 h induced reversible relative permittivity changes of EGF solution. However, compared with sham-exposed EGF solution, the MF-exposed EGF solution did not affect the binding of EGF to EGFR, nor the cell viability and EGFR clustering in human amniotic epithelial cells (FL cells). Our data suggest that cellular EGFR clustering response to MF exposure might not be a result of changes in relative permittivity of EGF in cell culture solution. Bioelectromagnetics. © 2020 Bioelectromagnetics Society.

The effects of 50 Hz magnetic field-exposed cell culture medium on cellular functions in FL cells

Although extremely low frequency magnetic fields (ELF-MFs) have been classified as a possible carcinogen for humans by the International Agency for Research on Cancer (IARC), their biological effects and underlying mechanisms are still unclear. Our previous study indicated that ELF-MF exposure influenced the relative permittivity of the saline solution, suggesting that the MF exposure altered physical properties of the solution. To explore the biophysical mechanism of ELF-MF-induced biological effects, this study examined the effects of 50 Hz sinusoidal MF at 0-4.0 mT on the permittivity of culture medium with phase-interrogation surface plasmon resonance (SPR) sensing. Then, the biological effects of MF pre-exposed culture medium on cell viability, the mitogen-activated protein kinase (MAPK) signaling pathways, oxidative stress, and genetic stabilities were analyzed using Cell Counting Kit-8, western blot, flow cytometry, γH2AX foci formation, and comet assay. The results showed that SPR signals were decreased under MF exposure in a time- and dose-dependent manner, and the decreased SPR signals were reversible when the exposure was drawn off. However, MF pre-exposed culture medium did not significantly change cell viability, intracellular reactive oxygen species level, activation of the MARK signaling pathways, or genetic stabilities in human amniotic epithelial cells (FL cells). In conclusion, our data suggest that the relative permittivity of culture medium was influenced by 50 Hz MF exposure, but this change did not affect the biological processes in FL cells.

Recent Progress in Optical Biosensors Based on Smartphone Platforms

With a rapid improvement of smartphone hardware and software, especially complementary metal oxide semiconductor (CMOS) cameras, many optical biosensors based on smartphone platforms have been presented, which have pushed the development of the point-of-care testing (POCT). Imaging-based and spectrometry-based detection techniques have been widely explored via different approaches. Combined with the smartphone, imaging-based and spectrometry-based methods are currently used to investigate a wide range of molecular properties in chemical and biological science for biosensing and diagnostics. Imaging techniques based on smartphone-based microscopes are utilized to capture microscale analysts, while spectrometry-based techniques are used to probe reactions or changes of molecules. Here, we critically review the most recent progress in imaging-based and spectrometry-based smartphone-integrated platforms that have been developed for chemical experiments and biological diagnosis. We focus on the analytical performance and the complexity for implementation of the platforms.