Millimeter-wave pulsed heating in vitro: cell mortality and heat shock response

Exploring and validating heating dynamics in a radio-frequency electromagnetic field-based resonant chamber for mouse hyperthermia research

Mild whole-body hyperthermia has been shown to have anti-tumor effects through an immune-modulating mechanism. Before it is widely applied in the clinic, tremendous mechanistic research in animals is necessary to adhere to evidence-based principles. The radio frequency electromagnetic field (RF-EMF) based heating facility could be a good choice for hyperthermia treatment, but the heating characteristics of a facility, including structure design, electromagnetic and thermal dosimetry, and the biologic effects of hyperthermia, need to be well elucidated. Here, we reported the heating characteristic study on a resonant chamber (RC) excited by a 1800 MHz solid source. The EMF in the RC was stirred by 24 static reflectors, which resulted in the standard deviation of electric field intensity being below 3 dB in the EM homogeneity evaluation. For the exposure scenario, six free-moving mice were loaded into separate cases and exposed simultaneously in the RC. The EMF energy absorption and distribution in exposed mice were calculated with the 12-plane-waves method of numerical simulation. Different levels of core body temperature increment in exposed mice were achieved through regulation of the source output power. Overexpression of heat shock proteins (HSPs) was detected in the liver, lung and muscle, but not in the brain of the exposed mice. The levels of representative inflammatory cytokines in the serum, TNF-α and IL-10 increased post RC exposure. Based on the heating characteristic study and validation, the applied RC would be a qualified heating system for mild whole-body hyperthermia effect research in mice.

Transcriptional landscape of human keratinocyte models exposed to 60-GHz millimeter-waves

The use of millimeter waves (MMW) will exponentially grow in the coming years due to their future utilization in 5G/6G networks. The question of possible biological effects at these frequencies has been raised. In this present study, we aimed to investigate gene expression changes under exposure to MMW using the Bulk RNA Barcoding and sequencing (BRB-seq) technology. To address this issue, three exposure scenarios were performed aiming at: i) comparing the cellular response of two primary culture of keratinocytes (HEK and NHEK) and one keratinocyte derivate cell line (HaCaT) exposed to MMW; ii) exploring the incident power density dose-effect on gene expression in HaCaT cell line; and, iii) studying the exposure duration at the new ICNIRP exposure limit for the general population. With the exception of heat effect induced by high power MMW (over 10 mW/cm2), those exposure scenarios have not enabled us to demonstrate important gene expression changes in the different cell populations studied. Very few differentially genes were observed between MMW exposed samples and heat shock control, and most of them were significantly associated with heat shock response that may reflect small differences in the heat generation. Together these results show that acute exposure to MMW has no effects on the transcriptional landscape of human keratinocyte models under athermal conditions.

Recent progress in the manipulation of biochemical and biophysical cues for engineering functional tissues

Tissue engineering (TE) is currently considered a cutting-edge discipline that offers the potential for developing treatments for health conditions that negatively affect the quality of life. This interdisciplinary field typically involves the combination of cells, scaffolds, and appropriate induction factors for the regeneration and repair of damaged tissue. Cell fate decisions, such as survival, proliferation, or differentiation, critically depend on various biochemical and biophysical factors provided by the extracellular environment during developmental, physiological, and pathological processes. Therefore, understanding the mechanisms of action of these factors is critical to accurately mimic the complex architecture of the extracellular environment of living tissues and improve the efficiency of TE approaches. In this review, we recapitulate the effects that biochemical and biophysical induction factors have on various aspects of cell fate. While the role of biochemical factors, such as growth factors, small molecules, extracellular matrix (ECM) components, and cytokines, has been extensively studied in the context of TE applications, it is only recently that we have begun to understand the effects of biophysical signals such as surface topography, mechanical, and electrical signals. These biophysical cues could provide a more robust set of stimuli to manipulate cell signaling pathways during the formation of the engineered tissue. Furthermore, the simultaneous application of different types of signals appears to elicit synergistic responses that are likely to improve functional outcomes, which could help translate results into successful clinical therapies in the future.

Morphophysiological and Proteomic Responses on Plants of Irradiation with Electromagnetic Waves

Electromagnetic energy is the backbone of wireless communication systems, and its progressive use has resulted in impacts on a wide range of biological systems. The consequences of electromagnetic energy absorption on plants are insufficiently addressed. In the agricultural area, electromagnetic-wave irradiation has been used to develop crop varieties, manage insect pests, monitor fertilizer efficiency, and preserve agricultural produce. According to different frequencies and wavelengths, electromagnetic waves are typically divided into eight spectral bands, including audio waves, radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. In this review, among these electromagnetic waves, effects of millimeter waves, ultraviolet, and gamma rays on plants are outlined, and their response mechanisms in plants through proteomic approaches are summarized. Furthermore, remarkable advancements of irradiating plants with electromagnetic waves, especially ultraviolet, are addressed, which shed light on future research in the electromagnetic field.

Millimeter-wave Heating in vitro: Local Microscale Temperature Measurements Correlated to Heat Shock Cellular Response

OBJECTIVE

Cellular sensitivity to heat is highly variable depending on the cell line. The aim of this paper is to assess the cellular sensitivity of the A375 melanoma cell line to continuous (CW) millimeter-waves (MMW) induced heating at 58.4 GHz, between 37 C and 47 C C to get a deeper insight into optimization of thermal treatment of superficial skin cancer.

METHODS

Phosphorylation of heat shock protein 27 (HSP27) was mapped within an area of about 30 mm2 to visualize the variation of heat-induced cellular stress as a function of the distance from the waveguide aperture (MMW radiation source). A multiphysics computational approach was then adopted to yield both electromagnetic and thermal field distributions as well as corresponding specific absorption rate (SAR) and temperature elevation. Induced temperature rise was experimentally measured using a micro-thermocouple (TC).

RESULTS

Coupling of the incident electromagnetic (EM) field with TC leads was first characterized, and optimal TC placing was identified. HSP27 phosphorylation was induced at temperatures 41 C, and its level increases as a function of the thermal dose delivered, remaining mostly focused within 3 mm2.

CONCLUSION

Phosphorylation of HSP27 represents a valuable marker of cellular stress of A375 melanoma cells under MMW exposure, providing both quantitative and spatial information about the distribution of the thermal stress.

SIGNIFICANCE

These results may contribute to the design of thermal treatments of superficial melanoma through MMW-induced heating in the hyperthermic temperature range.

Exposure Assessment in Millimeter-Wave Reverberation Chamber Using Murine Phantoms

This study deals with the design and calibration of the first mode-stirred reverberation chamber (RC) in the 60-GHz-band adapted for in vivo bioelectromagnetic studies. In addition to the interface for electromagnetic and thermal dosimetry, the interfaces for lighting and ventilation were integrated into the RC walls while preserving acceptable shielding. The RC with mechanical and electronic steering capabilities is characterized in the 55-65 GHz range. To this end, murine skin-equivalent phantoms of realistic shape were designed and fabricated. Their complex permittivity is within ±12% of the target value of murine skin (6.19-j5.81 at 60 GHz). The quality factor of the RC loaded with an animal cage, bedding litter, and five murine phantoms was found to be 1.2 × 10⁴ . The losses inside the RC were analyzed, and it was demonstrated that the main sources of the power dissipation were the phantoms and mice cage. The input power required to reach the average incident power density of 1 and 5 mW/cm² was found to be 0.23 and 1.14 W, respectively. Surface heating of the mice models was measured in the infrared (IR) range using a specifically designed interface, transparent at IR and opaque at millimeter waves (mmW). Experimental results were compared with an analytical solution of the heat transfer equation and to full-wave computations. Analytical and numerical results were in very good agreement with measurements (the relative deviation after 90 min of exposure was within 4.2%). Finally, a parametric study was performed to assess the impact of the thermophysical parameters on the resulting heating. Bioelectromagnetics. 2020;41:121-135. © 2020 Bioelectromagnetics Society.