Are the conformational dynamics and the ligand binding properties of myoglobin affected by exposure to microwave radiation?

A Systematic Review of In Vitro and In Vivo Radio Frequency Exposure Methods

Recently, interest in the effects of radio frequency (RF) on biological systems has increased and is partially due to the advancements and increased implementations of RF into technology. As research in this area has progressed, the reliability and reproducibility of the experiments has not crossed multidisciplinary boundaries. Therefore, as researchers, it is imperative to understand the various exposure systems available as well as the aspects, both electromagnetic and biological, needed to produce a sound exposure experiment. This systematic review examines common RF exposure methods for both in vitro and in vivo studies. For in vitro studies, possible biological limitations are emphasized. The validity of the examined methods, for both in vitro and in vivo, are analyzed by considering the advantages and disadvantages of each. This review offers guidance for researchers to assist in the development of an RF exposure experiment that crosses current multidisciplinary boundaries.

Inaccurate official assessment of radiofrequency safety by the Advisory Group on Non-ionising Radiation

The Advisory Group on Non-ionising Radiation (AGNIR) 2012 report forms the basis of official advice on the safety of radiofrequency (RF) electromagnetic fields in the United Kingdom and has been relied upon by health protection agencies around the world. This review describes incorrect and misleading statements from within the report, omissions and conflict of interest, which make it unsuitable for health risk assessment. The executive summary and overall conclusions did not accurately reflect the scientific evidence available. Independence is needed from the International Commission on Non-Ionizing Radiation Protection (ICNIRP), the group that set the exposure guidelines being assessed. This conflict of interest critically needs to be addressed for the forthcoming World Health Organisation (WHO) Environmental Health Criteria Monograph on Radiofrequency Fields. Decision makers, organisations and individuals require accurate information about the safety of RF electromagnetic signals if they are to be able to fulfil their safeguarding responsibilities and protect those for whom they have legal responsibility.

Effects of 3G cell phone exposure on the structure and function of the human cytochrome P450 reductase

Cell phones increase exposure to radiofrequency (RF) electromagnetic fields (EMFs). Whether EMFs exert specific effects on biological systems remains debatable. This study investigated the effect of cell phone exposure on the structure and function of human NADPH-cytochrome P450 reductase (CPR). CPR plays a key role in the electron transfer to cytochrome P450, which takes part in a wide range of oxidative metabolic reactions in various organisms from microbes to humans. Human CPR was exposed for 60min to 1966-MHz RF inside a transverse electromagnetic cell (TEM-cell) placed in an incubator. The specific absorption rate (SAR) was 5W·kg(-1). Conformation changes have been detected through fluorescent spectroscopy of flavin and tryptophan residues, and investigated through circular dichroism, dynamic light scattering and microelectrophoresis. These showed that CPR was narrowed. By using cytochrome C reductase activity to assess the electron flux through the CPR, the Michaelis Menten constant (Km) and the maximum initial velocity (Vmax) decreased by 22% as compared with controls. This change was due to small changes in the tertiary and secondary structures of the protein at 37°C. The relevance of these findings to an actual RF exposure scenario demands further biochemical and in-vivo confirmation.

Real-time assessment of possible electromagnetic-field-induced changes in protein conformation and thermal stability

Previous studies on possible interactions of radiofrequency electromagnetic fields (RF EMFs) with proteins have suggested that RF EMFs might affect protein structure and folding kinetics. In this study, the isolated thermosensor protein GrpE of the Hsp70 chaperone system of Escherichia coli was exposed to EMFs of various frequencies and field strengths under strictly controlled conditions. Circular dichroism spectroscopy was used to monitor possible structural changes. Simultaneously, temperature was recorded at each point of observation. The coiled-coil part of GrpE has been reported to undergo a well-defined and fully reversible folding/unfolding transition, thus facilitating the differentiation between thermal and non-thermal effects of RF EMFs. Any direct effect of EMF on the conformation and/or stability would result in a shift of the conformational equilibrium of the protein at a given temperature. Possible immediate (t ≤ 0.1 s) and delayed (t ≥ 30 s) effects of RF EMFs were investigated with sinusoidal signals of 0.1, 1.0, and 1.9 GHz at various field strengths up to 5.0 kV/m and with GSM signals at 0.3 kV/m in the protein solution. Taking the overall uncertainty of the experimental system into account, possible RF EMF-induced shifts in the conformational equilibrium of less than 1% of its total range might have been detected. The results obtained with the different experimental protocols indicate, however, that the conformational equilibrium of GrpE is insensitive to electromagnetic fields in the tested range of frequency and field strength.

Evaluation of thermal and non-thermal effects of UHF RFID exposure on biological drugs

The Radio Frequency Identification (RFID) technology promises to improve several processes in the healthcare scenario, especially those related to traceability of people and things. Unfortunately, there are still some barriers limiting the large-scale deployment of these innovative technologies in the healthcare field. Among these, the evaluation of potential thermal and non-thermal effects due to the exposure of biopharmaceutical products to electromagnetic fields is very challenging, but still slightly investigated. This paper aims to setup a controlled RF exposure environment, in order to reproduce a worst-case exposure of pharmaceutical products to the electromagnetic fields generated by the UHF RFID devices placed along the supply chain. Radiated powers several times higher than recommended by current normative limits were applied (10 W and 20 W). The electric field strength at the exposed sample location, used in tests, was as high as 100 V/m. Non-thermal effects were evaluated by chromatography techniques and in vitro assays. The results obtained for a particular case study, the ActrapidTM human insulin preparation, showed temperature increases lower than 0.5 °C and no significant changes in the structure and performance of the considered drug.

Carbohydrate cluster microarrays fabricated on three-dimensional dendrimeric platforms for functional glycomics exploration

We reported here a novel, ready-to-use bioarray platform and methodology for construction of sensitive carbohydrate cluster microarrays. This technology utilizes a three-dimensional (3-D) poly(amidoamine) starburst dendrimer monolayer assembled on glass surface, which is functionalized with terminal aminooxy and hydrazide groups for site-specific coupling of carbohydrates. A wide range of saccharides, including monosaccharides, oligosaccharides and polysaccharides of diverse structures, are applicable for the 3-D bioarray platform without prior chemical derivatization. The process of carbohydrate coupling is effectively accelerated by microwave radiation energy. The carbohydrate concentration required for microarray fabrication is substantially reduced using this technology. Importantly, this bioarray platform presents sugar chains in defined orientation and cluster configurations. It is, thus, uniquely useful for exploration of the structural and conformational diversities of glyco-epitope and their functional properties.

A method to investigate non-thermal effects of radio frequency radiation on pharmaceuticals with relevance to RFID technology

A method is reported to accurately and precisely control temperature of a solution sample to investigate non-thermal effects of radio frequency radiation (RFR) on pharmaceuticals. This method utilizes a transverse electromagnetic (TEM) cell connected in series with a radiation source. The temperature of a sample under study, within the TEM cell, is regulated using a combination of a fiber-optic thermometer and thermo-electric cooler. It is shown that the sample temperature can be accurately controlled and maintained even under conditions where the RFR can increase the sample temperature via thermal mode. This methodology provides a well-controlled approach to investigate the non-thermal effects of RFR for a range of incident power intensities and frequencies and initial sample temperatures.

Spatial and temporal control of microwave triggered chemiluminescence: a protein detection platform

We have combined the principles of microwave circuitry and antenna design and our recent work in microwave-triggered metal-enhanced chemiluminescence to now "trigger" chemically and enzyme-catalyzed chemiluminescent reactions with spatial and temporal control. With this technology platform, we achieve spatial and temporal control of enzyme and chemically catalyzed chemiluminescence reactions to achieve more than 500-fold increases in "on-demand" photon flux from chemically catalyzed chemiluminescent reactions. We also report a 6-fold increase in photon flux from HRP-catalyzed assays on disposable coverslips functionalized with HRP and placed proximal to the substrates modified with thin-film aluminum triangle disjointed "bow-tie" structures. In addition, we demonstrate the applicability of this technology to develop multiplexed or high-throughput chemiluminescent assays. We also demonstrate the clinical and biological relevance of this technology platform by affixing aluminum structures in proximity to HRP protein immobilized on nitrocellulose to improve the sensitivity for this model Western blot scheme by 50-fold. We believe analytical applications that rely on enzyme-catalyzed chemiluminescence, such as immunoassays, may greatly benefit from this new platform technology.

Microwave-Triggered Chemiluminescence with Planar Geometrical Aluminum Substrates: Theory, Simulation and Experiment

Previously we combined common practices in protein detection with chemiluminescence, microwave technology, and metal-enhanced chemiluminescence to demonstrate that we can use low power microwaves to substantially increase enzymatic chemiluminescent reaction rates on particulate silvered substrates. We now describe the applicability of continuous aluminum metal substrates to potentially further enhance or "trigger" enzymatic chemiluminescence reactions. Furthermore, our results suggest that the extent of chemiluminescence enhancement for surface and solution based enzyme reactions critically depends on the surface geometry of the aluminum film. In addition, we also use FDTD simulations to model the interactions of the incident microwave radiation with the aluminum geometries used. We demonstrate that the extent of microwave field enhancement for solution and surface based chemiluminescent reactions can be ascribed to "lightning rod" effects that give rise to different electric field distributions for microwaves incident on planar aluminum geometries. With these results, we believe that we can spatially and temporally control the extent of triggered chemiluminescence with low power microwave (Mw) pulses and maximize localized microwave triggered metal-enhanced chemiluminescence (MT-MEC) with optimized planar aluminum geometries. Thus we can potentially further improve the sensitivity of immunoassays with significantly enhanced signal-to-noise ratios.

Microwave triggered metal enhanced chemiluminescence: Quantitative protein determination

We present a new technology that offers a faster alternative to the chemiluminescence-based detection that is used in protein assay platforms today. By combining the use of silver nanostructures with chemiluminescent species, a technique that our laboratories have recently shown can enhance the system photon flux over 50-fold, with the use of low-power microwave heating to additionally accelerate, in essence "trigger", chemiluminescence-based reactions, then both ultrafast and ultrabright chemiluminescence assays can be realized. In addition, the preferential heating of the nanostructures by microwaves affords for microwave triggered metal enhanced chemiluminescence (MT-MEC) to be localized in proximity to the silvered surfaces, alleviating unwanted emission from the distal solution. To demonstrate MT-MEC, we have constructed a model assay sensing platform on both silvered and glass surfaces, where comparison with the identical glass substrate-based assay serves to confirm the significant benefits of using silver nanostructures for metal-enhanced chemiluminescence. Our new model assay technology can detect femtomoles of biotinylated BSA in less than 2 min and can indeed be modified to both detect and quantify a great many other biomolecules as well. As compared to traditional western blot approaches, MT-MEC offers protein quantification, high-sensitivity detection combined with ultrafast assay times, i.e., <2 min.

Microwave-Triggered Metal-Enhanced Chemiluminescence (MT-MEC): Application to Ultra-fast and Ultra-sensitive Clinical Assays

In this rapid communication we describe a new approach to protein detection with chemiluminescence. By combining common practices in protein detection with chemiluminescence, microwave technology, and metal-enhanced chemiluminescence, we show that we can use low power microwaves to substantially increase enzymatic chemiluminescent reaction rates on metal substrates. As a result, we have found that we can in essence trigger chemiluminescence with low power microwave (Mw) pulses and ultimately, perform on-demand protein detection assays. Using microwave triggered metal-enhanced chemiluminescence (MT-MEC), we not only improve the sensitivity of immunoassays with enhanced signal-to-noise ratios, but we also show that we can accurately quantify protein concentrations by integrating the photon flux for discrete time intervals.

Microwave-Accelerated Metal-Enhanced Fluorescence (MAMEF) with silver colloids in 96-well plates: Application to ultra fast and sensitive immunoassays, High Throughput Screening and drug discovery

Fluorescence detection is the basis of most assays used in drug discovery and High Throughput Screening (HTS) today. In all of these assays, assay rapidity and sensitivity is a primary concern, the sensitivity determined by both the quantum yield of the fluorophores and efficiency of the detection system, while rapidity is determined by the physical and biophysical parameters of temperature, concentration, assay bioaffinity, etc. In this paper we describe a platform technology that promises to fundamentally address these two physical constraints of sensitivity and rapidity. By combining the use of Metal-Enhanced Fluorescence (MEF), a near-field effect that can significantly enhance fluorescence signatures, with low power microwave heating, we can significantly increase the sensitivity of surface assays as well as >95% kinetically complete the assay within a few seconds. In addition, the metallic nanostructures used to facilitate MEF appear to be preferentially heated as compared to the surface assay fluid, advantageously localizing the MEF and heating around the nanostructures. To demonstrate proof of principle, a 96-well plate has been functionalized with silver nanostructures, and a model protein avidin-biotin assay studied. In our findings, a greater than 5-fold fluorescence enhancement coupled with a approximately 90-fold increase in assay kinetics was observed, but with no assay washing steps needed due to the silver-enhanced evanescent field mode of excitation. These findings promise to strongly facilitate high throughput fluorescence-based processes, such as in biology, drug discovery and general compound screening.

Microwave-Accelerated Metal-Enhanced Fluorescence: Platform Technology for Ultrafast and Ultrabright Assays

We describe an exciting assay platform technology that promises to fundamentally address two underlying physical constraints of modern assays and immunoassays, namely, assay sensitivity and rapidity. By combining the use of metal-enhanced fluorescence with low-power microwave heating, we can indeed significantly increase the sensitivity of surface assays as well as >95 % kinetically complete the assay within a few seconds. Subsequently, this new technology promises to fundamentally change the way we currently employ immunoassays in clinical medicine. This new model platform system can be potentially applied to many other important assays, such as to the clinical assessment of myoglobin, where both assay speed and sensitivity is paramount for the assessment and treatment of acute myocardial infarction. To demonstrate the utility of microwave-accelerated metal-enhanced fluorescence (MAMEF), we show that a simple protein-based assay system can be optically amplified approximately 10-fold by using silver nanostructures, while being kinetically complete in less than 20 s. This new platform approach is subsequently over 10-fold more sensitive and approximately 90 times faster than a control assay that operates both at room temperature and without the use of metal-enhanced fluorescence. Finally, we show that low-power heating by microwaves in our model system does not denature proteins, as evidenced by no protein structural changes, probed by fluorescence resonance energy transfer.

Non-thermal effects of electromagnetic fields at mobile phone frequency on the refolding of an intracellular protein: Myoglobin

Non-thermal effects induced by exposure to microwave electromagnetic field (MW-EMF) at 1.95 MHz, a frequency used in mobile communication, have been observed on the refolding kinetics of the heme binding site in an intracellular protein: tuna myoglobin, starting from acidic conditions. We have selected myoglobin because it can be considered a good model to study protein interactions with MW-EMF for its well-known high-resolution crystallographic structure. Myoglobin solutions at pH 3.0 were subjected to 3 h exposure to microwave field (with a specific absorption rate of 51 +/- 1 mW/g); the heme site refolding has been followed by measuring the molecular absorption in the Soret spectral region and the data were fitted to a bi-exponential model. The kinetics of exposed samples appear to be slowered by MW-EMF action. Moreover, the tryptophanyl lifetime distribution of the exposed protein, as deduced by the analysis of the fluorescence emission decay from its single tryptophan, appears sharper if compared to non-exposed protein samples. This observation suggests that the presence of MW-EMF could affect the propensity of protein molecules to populate specific conformational substates among which myoglobin molecules fluctuate at acidic pH. Changes in the structural fluctuation caused by MW perturbation can affect differently the aggregation process that occurs competitively during the protein folding, so representing a potential risk for protein "misfolding." These data suggest that MW-EMF could have also biochemical and, consequently, biological effects on eukaryotic cells that are still under investigation.