Enhancement of Penetration of Millimeter Waves by Field Focusing Applied to Breast Cancer Detection.

OBJECTIVE: The potentialities of improving the penetration of millimeter waves for breast cancer imaging are here explored. METHODS: A field focusing technique based on a convex optimization method is proposed, capable of increasing the field level inside a breast-emulating stratification. RESULTS: The theoretical results are numerically validated via the design and simulation of two circularly polarized antennas. The experimental validation of the designed antennas, using tissue-mimicking phantoms, is provided, being in good agreement with the theoretical predictions. CONCLUSION: The possibility of focusing, within a lossy medium, the electromagnetic power at millimeter-wave frequencies is demonstrated. SIGNIFICANCE: Field focusing can be a key for using millimeter waves for breast cancer detection.

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

Millimeter wave (MMW)-induced heating represents a promising alternative for non-invasive hyperthermia of superficial skin cancer, such as melanoma. Pulsed MMW-induced heating of tumors allows for reaching high peak temperatures without overheating surrounding tissues. Herein, for the first time, we evaluate apoptotic and heat shock responses of melanoma cells exposed in vitro to continuous (CW) or pulsed-wave (PW) amplitude-modulated MMW at 58.4 GHz with the same average temperature rise. Using an ad hoc exposure system, we generated 90 min pulse train with 1.5 s pulse duration, period of 20 s, amplitude of 10 °C, and steady-state temperature at the level of cells of 49.2 °C. The activation of Caspase-3 and phosphorylation of HSP27 were investigated using fluorescence microscopy to monitor the spatial variation of cellular response. Our results demonstrate that, under the considered exposure conditions, Caspase-3 activation was almost 5 times greater following PW exposure compared to CW. The relationship between the PW-induced cellular response and SAR-dependent temperature rise was non-linear. Phosphorylation of HSP27 was 58% stronger for PW compared to CW. It exhibits a plateau for the peak temperature ranging from 47.7 to 49.2 °C. Our results provide an insight into understanding of the cellular response to MMW-induced pulsed heating.

Optimal Radiation of Body-Implanted Capsules.

Autonomous implantable bioelectronics requires efficient radiating structures for data transfer and wireless powering. The radiation of body-implanted capsules is investigated to obtain the explicit radiation optima for E- and B-coupled sources of arbitrary dimensions and properties. The analysis uses the conservation-of-energy formulation within dispersive homogeneous and stratified canonical body models. The results reveal that the fundamental bounds exceed by far the efficiencies currently obtained by conventional designs. Finally, a practical realization of the optimal source based on a dielectric-loaded cylindrical-patch structure is presented. The radiation efficiency of the structure closely approaches the theoretical bounds and shows a fivefold improvement over existing systems.

Untargeted Metabolomics Reveal Lipid Alterations upon 2-Deoxyglucose Treatment in Human HaCaT Keratinocytes.

The glucose analogue 2-deoxyglucose (2-DG) impedes cancer progression in animal models and is currently being assessed as an anticancer therapy, yet the mode of action of this drug of high clinical significance has not been fully delineated. In an attempt to better characterize its pharmacodynamics, an integrative UPLC-Q-Exactive-based joint metabolomic and lipidomic approach was undertaken to evaluate the metabolic perturbations induced by this drug in human HaCaT keratinocyte cells. R-XCMS data processing and subsequent multivariate pattern recognition, metabolites identification, and pathway analyses identified eight metabolites that were most significantly changed upon a 3 h 2-DG exposure. Most of these dysregulated features were emphasized in the course of lipidomic profiling and could be identified as ceramide and glucosylceramide derivatives, consistently with their involvement in cell death programming. Even though metabolomic analyses did not generally afford such clear-cut dysregulations, some alterations in phosphatidylcholine and phosphatidylethanolamine derivatives could be highlighted as well. Overall, these results support the adequacy of the proposed analytical workflow and might contribute to a better understanding of the mechanisms underlying the promising effects of 2-DG.

Effect of acute millimeter wave exposure on dopamine metabolism of NGF-treated PC12 cells.

Several forthcoming wireless telecommunication systems will use electromagnetic frequencies at millimeter waves (MMWs), and technologies developed around the 60-GHz band will soon know a widespread distribution. Free nerve endings within the skin have been suggested to be the targets of MMW therapy which has been used in the former Soviet Union. So far, no studies have assessed the impact of MMW exposure on neuronal metabolism. Here, we investigated the effects of a 24-h MMW exposure at 60.4 GHz, with an incident power density (IPD) of 5 mW/cm², on the dopaminergic turnover of NGF-treated PC12 cells. After MMW exposure, both intracellular and extracellular contents of dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) were studied using high performance liquid chromatography. Impact of exposure on the dopamine transporter (DAT) expression was also assessed by immunocytochemistry. We analyzed the dopamine turnover by assessing the ratio of DOPAC to DA, and measuring DOPAC accumulation in the medium. Neither dopamine turnover nor DAT protein expression level were impacted by MMW exposure. However, extracellular accumulation of DOPAC was found to be slightly increased, but not significantly. This result was related to the thermal effect, and overall, no evidence of non-thermal effects of MMW exposure were observed on dopamine metabolism.

Impact of 60-GHz millimeter waves on stress and pain-related protein expression in differentiating neuron-like cells.

Millimeter waves (MMW) will be increasingly used for future wireless telecommunications. Previous studies on skin keratinocytes showed that MMW could impact the mRNA expression of Transient Receptor Potential cation channel subfamily Vanilloid, member 2 (TRPV2). Here, we investigated the effect of MMW exposure on this marker, as well as on other membrane receptors such as Transient Receptor Potential cation channel subfamily Vanilloid, member 1 (TRPV1) and purinergic receptor P2X, ligand-gated ion channel, 3 (P2 × 3). We exposed the Neuroscreen-1 cell line (a PC12 subclone), in order to evaluate if acute MMW exposures could impact expression of these membrane receptors at the protein level. Proteotoxic stress-related chaperone protein Heat Shock Protein 70 (HSP70) expression level was also assessed. We used an original high-content screening approach, based on fluorescence microscopy, to allow cell-by-cell analysis and to detect any cell sub-population responding to exposure. Immunocytochemistry was done after 24 h MMW exposure of cells at 60.4 GHz, with an incident power density of 10 mW/cm(2) . Our results showed no impact of MMW exposure on protein expressions of HSP70, TRPV1, TRPV2, and P2 × 3. Moreover, no specific cell sub-populations were found to express one of the studied markers at a different level, compared to the rest of the cell populations. However, a slight insignificant increase in HSP70 expression and an increase in protein expression variability within cell population were observed in exposed cells, but controls showed that this was related to thermal effect. Bioelectromagnetics. 37:444-454, 2016. © 2016 Wiley Periodicals, Inc.

Additive Effects of Millimeter Waves and 2-Deoxyglucose Co-Exposure on the Human Keratinocyte Transcriptome.

Millimeter Waves (MMW) will be used in the next-generation of high-speed wireless technologies, especially in future Ultra-Broadband small cells in 5G cellular networks. Therefore, their biocompatibilities must be evaluated prior to their massive deployment. Using a microarray-based approach, we analyzed modifications to the whole genome of a human keratinocyte model that was exposed at 60.4 GHz-MMW at an incident power density (IPD) of 20 mW/cm2 for 3 hours in athermic conditions. No keratinocyte transcriptome modifications were observed. We tested the effects of MMWs on cell metabolism by co-treating MMW-exposed cells with a glycolysis inhibitor, 2-deoxyglucose (2dG, 20 mM for 3 hours), and whole genome expression was evaluated along with the ATP content. We found that the 2dG treatment decreased the cellular ATP content and induced a high modification in the transcriptome (632 coding genes). The affected genes were associated with transcriptional repression, cellular communication and endoplasmic reticulum homeostasis. The MMW/2dG co-treatment did not alter the keratinocyte ATP content, but it did slightly alter the transcriptome, which reflected the capacity of MMW to interfere with the bioenergetic stress response. The RT-PCR-based validation confirmed 6 MMW-sensitive genes (SOCS3, SPRY2, TRIB1, FAM46A, CSRNP1 and PPP1R15A) during the 2dG treatment. These 6 genes encoded transcription factors or inhibitors of cytokine pathways, which raised questions regarding the potential impact of long-term or chronic MMW exposure on metabolically stressed cells.

Effects of 60-GHz millimeter waves on neurite outgrowth in PC12 cells using high-content screening.

Technologies for wireless telecommunication systems using millimeter waves (MMW) will be widely deployed in the near future. Forthcoming applications in this band, especially around 60GHz, are mainly developed for high data-rate local and body-centric telecommunications. At those frequencies, electromagnetic radiations have a very shallow penetration into biological tissues, making skin keratinocytes, and free nerve endings of the upper dermis the main targets of MMW. Only a few studies assessed the impact of MMW on neuronal cells, and none of them investigated a possible effect on neuronal differentiation. We used a neuron-like cell line (PC12), which undergoes neuronal differentiation when treated with the neuronal growth factor (NGF). PC12 cells were exposed at 60.4GHz for 24h, at an incident power density averaged over the cell monolayer of 10mW/cm(2). Using a large scale cell-by-cell analysis based on high-content screening microscopy approach, we assessed potential effects of MMW on PC12 neurite outgrowth and cytoskeleton protein expression. No differences were found in protein expression of the neuronal marker ß3-tubulin nor in internal expression control ß-tubulin. On the other hand, our data showed a slight increase, although insignificant, in neurite outgrowth, induced by MMW exposure. However, experimental controls demonstrated that this increase was related to heating.

Millimeter waves as a source of selective heating of skin.

This study demonstrates that 20-100 GHz range can be used for spatially-accurate focusing of heating inside the skin achieved by varying frequency and exposure beam size, as well as by enforcing air convection. The latter is also used to reduce overheating of skin surface. Heating at different skin depths depending on these parameters is investigated in detail using the hybrid bio-heat equation. In particular, it is shown that decreasing frequency and/or increasing exposure beam size at forced airflow result in elevation of heating of deeper layers of tissue and decrease of skin surface temperature. Changes of water content within 15%, which exceed those due to aging and presence of tumors, only slightly affect heating. Exposure intensity necessary to reach a target temperature significantly increases in different areas of body with elevated blood flow. Dependence on exposure intensity and hyperthermia treatment duration is also investigated and discussed. Results of this study suggest that the lower part of the millimeter-wave range is an attractive alternative for non-invasive thermal treatment of skin cancer with a high spatial resolution.

Exposure system and dosimetry for in vitro studies of biocompatibility of pulse-modulated RF signals of ultrahigh field MRI.

A new setup for exposure of human cells in vitro at 37 °C to pulse-modulated 300 and 500 MHz signals of future magnetic resonance imaging (MRI) systems is designed, built up, and characterized. Two dipole antennas, specifically designed for ultrahigh field MRI, are used as radiating structures. The electromagnetic (EM) field distribution inside the incubator containing the cells is computed, and it is shown to be in a good agreement with measurements. The electric field at the cell level is quantified numerically. Local, 1-g average, and averaged over the culture medium volume SAR are provided along with the standard deviation values for each well. Temperature increments are measured inside the culture medium during the exposure using an optical fiber thermometer. Then, we identify the pulse parameters corresponding to the thermal threshold of 1 °C, usually considered as a threshold for thermally induced biological effects. For these parameters, the induction of heat shock proteins is assessed to biologically verify a potential thermal response of cells. The data demonstrate that, under the considered experimental conditions, exposure to pulse-modulated radiations emulating typical ultrahigh field MRI signals, corresponding to temperature increments below 1 °C, does not trigger any heat shock response in human brain cells.

Whole-genome expression analysis in primary human keratinocyte cell cultures exposed to 60 GHz radiation.

The main purpose of this study is to investigate potential responses of skin cells to millimeter wave (MMW) radiation increasingly used in the wireless technologies. Primary human skin cells were exposed for 1, 6, or 24 h to 60.4 GHz with an average incident power density of 1.8 mW/cm(2) and an average specific absorption rate of 42.4 W/kg. A large-scale analysis was performed to determine whether these exposures could affect the gene expression. Gene expression microarrays containing over 41,000 unique human transcript probe sets were used, and data obtained for sham and exposed cells were compared. No significant difference in gene expression was observed when gene expression values were subjected to a stringent statistical analysis such as the Benjamini-Hochberg procedure. However, when a t-test was employed to analyze microarray data, 130 transcripts were found to be potentially modulated after exposure. To further quantitatively analyze these preselected transcripts, real-time PCR was performed on 24 genes with the best combination of high fold change and low P-value. Five of them, namely CRIP2, PLXND1, PTX3, SERPINF1, and TRPV2, were confirmed as differentially expressed after 6 h of exposure. To the best of our knowledge, this is the first large-scale study reporting on potential gene expression modification associated with MMW radiation used in wireless communication applications.

Study of narrow band millimeter-wave potential interactions with endoplasmic reticulum stress sensor genes.

The main purpose of this article is to study potential biological effects of low-power millimeter waves (MMWs) on endoplasmic reticulum (ER), an organelle sensitive to a wide variety of environmental insults and involved in a number of pathologies. We considered exposure frequencies around 60 GHz in the context of their near-future applications in wireless communication systems. Radiations within this frequency range are strongly absorbed by oxygen molecules, and biological species have never been exposed to such radiations in natural environmental conditions. A set of five discrete frequencies has been selected; three of them coincide with oxygen spectral lines (59.16, 60.43, and 61.15 GHz) and two frequencies correspond to the spectral line overlap regions (59.87 and 60.83 GHz). Moreover, we used a microwave spectroscopy approach to select eight frequencies corresponding to the spectral lines of various molecular groups within 59-61 GHz frequency range. The human glial cell line, U-251 MG, was exposed or sham-exposed for 24 h with a peak incident power density of 0.14 mW/cm(2). The average specific absorption rate (SAR) within the cell monolayer ranges from 2.64 +/- 0.08 to 3.3 +/- 0.1 W/kg depending on the location of the exposed well. We analyzed by quantitative reverse transcription-polymerase chain reaction (RT-PCR) the level of expression of two endogenous ER-stress biomarkers, namely, the chaperones BiP/GRP78 and ORP150/GRP170. It was found that exposure to low-power MMW does not significantly modify the mRNA levels of these stress-sensitive genes suggesting that ER homeostasis is not altered by low-power MMW at the considered frequencies.

Absence of direct effect of low-power millimeter-wave radiation at 60.4 GHz on endoplasmic reticulum stress.

Millimeter waves (MMW) at frequencies around 60 GHz will be used in the very near future in the emerging local wireless communication systems and the potential health hazards of artificially induced environmental exposures represent a major public concern. The main aim of this study was to investigate the potential effects of low-power MMW radiations on cellular physiology. To this end, the human glial cell line, U-251 MG, was exposed to 60.4 GHz radiation at a power density of 0.14 mW/cm(2) and potential effect of MMW radiations on endoplasmic reticulum (ER) stress was investigated. ER is very sensitive to environmental insults and its homeostasis is altered in various pathologies. Through several assay systems, we found that exposure to 60.4 GHz does not modify ER protein folding and secretion, nor induces XBP1 or ATF6 transcription factors maturation. Moreover, expression of ER-stress sensor, BiP/GRP78 was examined by real-time PCR, in exposed or non-exposed cells to MMW radiations. Our data demonstrated the absence of significant changes in mRNA levels for BiP/GRP78. Our results showed that ER homeostasis does not undergo any modification at molecular level after exposure to low-power MMW radiation at 60.4 GHz. This report is the first study of ER-stress induction by MMW radiations.