Authors

Fortune JA, Wu BI, Klibanov, AM. Radio frequency radiation causes no nonthermal damage in enzymes and living cells. Biotech. Progress. Ahead of print. Jun 22, 2010.

 

Background
The ability of radiofrequency radiation (RFR) to exert irreversible nonthermal effects on biologics has been widely debated. This is because corresponding studies are often not reproducible and report effects only slightly above the noise, critical testing parameters are frequently missing, accurate sample temperature maintenance is often lacking, reported studies lack sufficient breadth to make generalizations, no plausible mechanism is evident for said effects, and the published literature presents conflicting conclusions.

Objective
The objective of this study was to more definitively investigate the existence of nonthermal continuous wave RFR effects on commercially important enzymes and live bacterial and human cells.

Methods
Escherichia coli, staphylococcus aureus and human TK6 cells were exposed to 2.45 GHz, 915 MHz, and 13.56 MHz using a signal generator and amplifier to generate the desired signal. The signal was passed into a transverse electromagnetic (TEM) cell housing the sample. Horseradish peroxidase and β-galactosidase enzymatic activity was assessed using a Sigma-Aldrich protocol. Following the RFR exposure, bacterial cell aliquots were analyzed for viability (as measured by membrane integrity) using a Molecular Probes Live/Dead BacLight Bacterial Viability Kit and human cell aliquots were analyzed for cell vitality (as assessed by metabolic activity) using a Cell Vitality Assay Kit.

Results
Enzymatic activities of horseradish peroxidase and β-galactosidase in aqueous solution did not appreciably deviate from control values over the course of the exposure and exhibited no statistically discernable consequences of even very intense RFR. The viabilities of bacteria (both gram-positive and gram-negative) and of human cells were not compromised by RFR exposure. No detectable change in the number of viable cells over time was observed relative to the control (i.e., without RFR) for both microorganisms. Statistical analysis confirmed that the changes were indistinguishable at a 95% confidence interval for irradiated and control samples. When putative nonthermal effects of RFR on human TK6 cells were examined cellular vitalities (relative to the control) with and without irradiation were similar for all the frequencies studied.

Interpretation and Limitations
Enzymatic activity is among the most sensitive measures of the intactness of protein structure. The authors suggest that a further study of the effect of RFR on the enzymes appears unwarranted because no effect on catalytic activity has been observed. Since growth is one of the pivotal cellular processes altered when a living cell is stressed, they chose this variable as their endpoint measurement and observed no radiation-induced changes. One limitation of this study is that the authors exposed samples for far longer, to greater power, and under more destabilizing conditions than employed in previous studies. Additional studies using different cell types exposed to similar but also more stable conditions are warranted to more closely resemble real-life exposures.

Conclusions
This study suggests that continuous-wave radiation at 13.56 MHz, 915 MHz, or 2.45 GHz frequencies induce no detectable nonthermal effect on biologics even under conditions far harsher than those to be encountered in real-life.


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