BackgroundIn recent times there has been some controversy over the impact of electromagnetic radiation on human health. The significance of mobile phone radiation on male reproduction is a key element of this debate since several studies have suggested a relationship between mobile phone use and semen quality. The potential mechanisms involved have not been established, however, human spermatozoa are known to be particularly vulnerable to oxidative stress by virtue of the abundant availability of substrates for free radical attack and the lack of cytoplasmic space to accommodate antioxidant enzymes. Moreover, the induction of oxidative stress in these cells not only perturbs their capacity for fertilization but also contributes to sperm DNA damage. The latter has, in turn, been linked with poor fertility, an increased incidence of miscarriage and morbidity in the offspring, including childhood cancer. In light of these associations, we have analyzed the influence of RF-EMR on the cell biology of human spermatozoa in vitro.Principal FindingsPurified human spermatozoa were exposed to radio-frequency electromagnetic radiation (RF-EMR) tuned to 1.8 GHz and covering a range of specific absorption rates (SAR) from 0.4 W/kg to 27.5 W/kg. In step with increasing SAR, motility and vitality were significantly reduced after RF-EMR exposure, while the mitochondrial generation of reactive oxygen species and DNA fragmentation were significantly elevated (P<0.001). Furthermore, we also observed highly significant relationships between SAR, the oxidative DNA damage bio-marker, 8-OH-dG, and DNA fragmentation after RF-EMR exposure.ConclusionsRF-EMR in both the power density and frequency range of mobile phones enhances mitochondrial reactive oxygen species generation by human spermatozoa, decreasing the motility and vitality of these cells while stimulating DNA base adduct formation and, ultimately DNA fragmentation. These findings have clear implications for the safety of extensive mobile phone use by males of reproductive age, potentially affecting both their fertility and the health and wellbeing of their offspring.

Concern has arisen over human exposures to radio frequency electromagnetic radiation (RFEMR), including a recent report indicating that regular mobile phone use can negatively impact upon human semen quality. These effects would be particularly serious if the biological effects of RFEMR included the induction of DNA damage in male germ cells. In this study, mice were exposed to 900 MHz RFEMR at a specific absorption rate of approximately 90 mW/kg inside a waveguide for 7 days at 12 h per day. Following exposure, DNA damage to caudal epididymal spermatozoa was assessed by quantitative PCR (QPCR) as well as alkaline and pulsed-field gel electrophoresis. The treated mice were overtly normal and all assessment criteria, including sperm number, morphology and vitality were not significantly affected. Gel electrophoresis revealed no gross evidence of increased single- or double-DNA strand breakage in spermatozoa taken from treated animals. However, a detailed analysis of DNA integrity using QPCR revealed statistically significant damage to both the mitochondrial genome (p < 0.05) and the nuclear beta-globin locus (p < 0.01). This study suggests that while RFEMR does not have a dramatic impact on male germ cell development, a significant genotoxic effect on epididymal spermatozoa is evident and deserves further investigation.

A new method for fabrication of microelectrode arrays comprised of traditional implant materials is presented. The main construction principle is the use of spun-on medical grade silicone rubber as insulating substrate material and platinum foil as conductor (tracks, pads and electrodes). The silicone rubber and the platinum foil are patterned by laser cutting using an Nd:YAG laser and a microcontroller-driven, stepper-motor operated x-y table. The method does not require expensive clean room facilities and offers an extremely short design-to-prototype time of below 1 day. First prototypes demonstrate a minimal achievable feature size of about 30 microm.

Direct photocurrent mapping of organic solar cells (OSCs) using a novel implementation of a near-field scanning optical microscope (NSOM) is described. By rastering the light output from the NSOM through a semitransparent electrode across the OSC surface, it is possible to collect height and photocurrent images simultaneously with a lateral resolution that is governed by the NSOM aperture. The photocurrent images demonstrate that film inhomogeneities and segregation effects strongly influence OSC device performance.

The ability to covalently attach organic molecules to semiconductor surfaces in a controllable and selective manner is currently receiving much attention due to the potential for creating hybrid silicon-organic molecular-electronic devices. Here we use scanning tunneling microscopy (STM) and density functional theory calculations to study the adsorption of a simple ketone [acetone; (CH(3))(2)CO] to the silicon (001) surface. We show both bias and time-dependent STM images and their agreement with total energy DFT calculations, simulated STM images, and published spectroscopic data. We investigate the stability of the resulting adsorbate structures with respect to temperature and applied STM tip bias and current. We demonstrate the ability to convert from the kinetically favored single-dimer alpha-H cleavage adsorbate structure to thermodynamically favored bridge-bonded adsorbate structures. This can be performed for the entire surface using a thermal anneal or, for individual molecules, using the highly confined electron beam of the STM tip. We propose the use of the carbonyl functional group to tether organic molecules to silicon may lead to increased stability of the adsorbates with respect to current-voltage characterization. This has important implications for the creation of robust single-molecule devices.