Driving electrochemical corrosion of implanted CoCrMo metal via oscillatory electric fields without mechanical wear.

Decades of research have been dedicated to understanding the corrosion mechanisms of metal based implanted prosthetics utilized in modern surgical procedures. Focused primarily on mechanically driven wear, current fretting and crevice corrosion investigations have yet to precisely replicate the complex chemical composition of corrosion products recovered from patients' periprosthetic tissue. This work specifically targets the creation of corrosion products at the metal on metal junction utilized in modular hip prosthetics. Moreover, this manuscript serves as an initial investigation into the potential interaction between implanted CoCrMo metal alloy and low amplitude electrical oscillation, similar in magnitude to those which may develop from ambient electromagnetic radiation. It is believed that introduction of such an electrical oscillation may be able to initiate electrochemical reactions between the metal and surrounding fluid, forming the precursor to secondary wear particles, without mechanically eroding the metal's natural passivation layer. Here, we show that a low magnitude electrical oscillation (≤ 200 mV) in the megahertz frequency (106 Hz) range is capable of initiating corrosion on implanted CoCrMo without the addition of mechanical wear. Specifically, a 50 MHz, 200 mVpp sine wave generates corrosion products comprising of Cr, P, Ca, O, and C, which is consistent with previous literature on the analysis of failed hip prosthetics. These findings demonstrate that mechanical wear may not be required to initiate the production of chemically complex corrosion products.

Investigation of the effects of electrochemical reactions on complex metal tribocorrosion within the human body.

Although total hip arthroplasty (THA) is considered to be the most successful orthopedic operation in restoring mobility and relieving pain, common Metal-on-Metal (MoM) implants developed in the past decade suffer from severe inflammatory reactions of the surrounding tissue caused by the premature corrosion and degradation of the implant. A substantial amount of research has been dedicated to the investigation of mechanically driven fretting and crevice corrosion as the primary mechanism of implant failure. However, the exact mechanism by which hip implant breakdown occurs remains unknown, as current in vitro fretting and crevice corrosion studies have failed to completely replicate the corrosion characteristics of recovered implants. Here, we show that minor electric potential oscillations on a model hip implant replicate the corrosion of failed implants without the introduction of mechanical wear. We found in a controlled lab setting that small electrical oscillations, of similar frequency and magnitude as those resulting from ambient electromagnetic waves interacting with the metal of the implant, can force electrochemical reactions within a simulated synovial fluid environment that have not been previously predicted. In lab testing we have shown the replication of titanium, phosphorous, and oxygen deposition onto the surface of ASTM astm:F75 CoCrMo metal alloy test specimens, matching the chemical composition of previously retrieved wear particles from failed patient prosthetics. Our results demonstrate that the electrical activity and ensuing electrochemical activity excites two corrosion failure modes: direct dissolution of the medically implantable alloy, leaching metal ions into the body, and surface deposition growth, forming the precursor of secondary wear particles. We anticipate our findings to be the foundation for the future development and testing of electrochemically resistant implantable material.

Novel investigation of perovskite membrane based electrochemical nitric oxide control phenomenon.

The combustion of hydrocarbon fuels within the automotive industry results in harmful and reactive incomplete combustion byproducts. Specifically, nitric oxide emissions (NO) lead to increased smog, acid rain, climate change, and respiratory inflammation within the population [Nitrogen Dioxide | American Lung Association]. Current methods for treating combustion exhaust include the catalytic converter in conjunction with nitrogen oxide traps. However, there is no active, continuous reduction method that does not require restrictions on the combustion environment (Hirata in Catal Surv Asia 18:128-133, 2014). Here, a small voltage potential oscillation across a newly designed electro-chemical catalytic membrane significantly reduces NO emissions. A ceramic membrane consisting of two dissimilar metal electrodes, sandwiching a dielectric layer, is able to achieve an NO reduction in excess of 2X that of a platinum group metal (PGM) three way catalytic converter. An analysis of the exhaust effluent from the membranes indicates N2O as a precursor to N2 and O2 formation, without the introduction of ammonia (NH3), during the reaction of NO indicating a divergence from current literature. Our results demonstrate how an oscillatory electric potential on a catalytic surface may alter anticipated reaction chemistry and interaction between the catalytic surface and fluid flow.

Combustion Characterization and Model Fuel Development for Micro-tubular Flame-assisted Fuel Cells.

Combustion based power generation has been accomplished for many years through a number of heat engine systems. Recently, a move towards small scale power generation and micro combustion as well as development in fuel cell research has created new means of power generation that combine solid oxide fuel cells with open flames and combustion exhaust. Instead of relying upon the heat of combustion, these solid oxide fuel cell systems rely on reforming of the fuel via combustion to generate syngas for electrochemical power generation. Procedures were developed to assess the combustion by-products under a wide range of conditions. While theoretical and computational procedures have been developed for assessing fuel-rich combustion exhaust in these applications, experimental techniques have also emerged. The experimental procedures often rely upon a gas chromatograph or mass spectrometer analysis of the flame and exhaust to assess the combustion process as a fuel reformer and means of heat generation. The experimental techniques developed in these areas have been applied anew for the development of the micro-tubular flame-assisted fuel cell. The protocol discussed in this work builds on past techniques to specify a procedure for characterizing fuel-rich combustion exhaust and developing a model fuel-rich combustion exhaust for use in flame-assisted fuel cell testing. The development of the procedure and its applications and limitations are discussed.

Comparative toxicity of silver nanoparticles on oxidative stress and DNA damage in the nematode, Caenorhabditis elegans.

This study examined the effects of polyvinylpyrrolidone (PVP) surface coating and size on the organismal and molecular toxicity of silver nanoparticles (AgNPs) on the nematode, Caenorhabditis elegans. The toxicity of bare AgNPs and 8 and 38 nm PVP-coated AgNPs (PVP8-AgNPs, PVP38-AgNPs) were compared. The toxicity of AgNO3 was also tested because ion dissolution and particle-specific effects are often important characteristics determining Ag nanotoxicity. Comparative toxicity across AgNO3 and the three different types of AgNPs was first evaluated using a C. elegans mortality test by a direct comparison of the LC50 values. Subsequently, mutant screening followed by oxidative stress, mitochondrial toxicity and DNA damage assays were carried out at equitoxic (LC10 and LC50) concentrations to further assess the toxicity mechanism of AgNO3 and AgNPs. AgNO3 and bare AgNPs had similar toxicities, whereas PVP coating reduced the toxicity of the AgNPs significantly. Of the PVP-AgNPs, the smaller NPs were more toxic. Different groups of mutants responded differently to AgNO3 and AgNPs, which indicates that their toxicity mechanism might be different. AgNO3 and bare AgNPs induced mitochondrial membrane damage. None of the silver materials tested caused detectable polymerase-inhibiting DNA lesions in either the nucleus or mitochondria as measured by a quantitative PCR assay, but AgNO3, bare AgNPs and PVP8-AgNPs induced oxidative DNA damage. These results show that coatings on the AgNPs surface and the particle size make a clear contribution to the toxicity of the AgNPs, and oxidative stress-related mitochondrial and DNA damage appear to be potential mechanisms of toxicity.

Hypoxia inducible factor-1 (HIF-1)-flavin containing monooxygenase-2 (FMO-2) signaling acts in silver nanoparticles and silver ion toxicity in the nematode, Caenorhabditis elegans.

In the present study, nanotoxicity mechanism associated with silver nanoparticles (AgNPs) exposure was investigated on the nematode, Caenorhabditis elegans focusing on the hypoxia response pathway. In order to test whether AgNPs-induced hypoxia inducible factor-1 (HIF-1) activation was due to hypoxia or to oxidative stress, depletion of dissolved oxygen (DO) in the test media and a rescue effect using an antioxidant were investigated, respectively. The results suggested that oxidative stress was involved in activation of the HIF-1 pathway. We then investigated the toxicological implications of HIF-1 activation by examining the HIF-1 mediated transcriptional response. Of the genes tested, increased expression of the flavin containing monooxygenase-2 (FMO-2) gene was found to be the most significant as induced by AgNPs exposure. We found that AgNPs exposure induced FMO-2 activation in a HIF-1 and p38 MAPK PMK-1 dependent manner, and oxidative stress was involved in it. We conducted all experiments to include comparison of AgNPs and AgNO3 in order to evaluate whether any observed toxicity was due to dissolution or particle specific. The AgNPs and AgNO3 did not produce any qualitative differences in terms of exerting toxicity in the pathways observed in this study, however, considering equal amount of silver mass, in every endpoint tested the AgNPs were found to be more toxic than AgNO3. These results suggest that Ag nanotoxicity is dependent not only on dissolution of Ag ion but also on particle specific effects and HIF-1-FMO-2 pathway seems to be involved in it.

Comparison of real-time reverse transcriptase-polymerase chain reaction and nested or commercial reverse transcriptase-polymerase chain reaction for the detection of hepatitis E virus particle in human serum.

Hepatitis E virus (HEV) was originally identified as the causative agent of enterically transmitted non-A, non-B hepatitis. The virus is the 7.5-kb single-stranded positive RNA virus and has been classified in the genus Herpevirus [corrected] of the [corrected] Herpeviridae [corrected] Recently, HEVs were identified from several countries worldwide from human and animals including swine. Studies on the genomic analysis of HEV isolates and seroprevalence of anti-HEV antibodies suggested that HEV has been considered as a potent zoonotic agent. The HEV infection has been diagnosed by detection of anti-HEV antibodies or virus by using reverse transcriptase-polymerase chain reaction (RT-PCR) methods in the blood or feces. However, these diagnostic methods were not quantitative and not enough to diagnose small amounts of target molecules. Moreover, these methods were not adequate during the incubation period or early acute phase. To overcome these problems, real-time RT-PCR method was developed with a cloned viral DNA and in vitro transcribed cRNA in this study. The sensitivity of the reaction was 1.68 x 10(1) copies per reaction. Correlation coefficient values of the reactions in the repeated experiments were over 0.99. Ranges of slopes and coefficient variation values were from 3.341 to 3.435 and from 1.20 to 5.98, respectively. In comparison of the real-time PCR with nested or commercial RT-PCR, HEV particles could be detected in the negative samples, which were determined by conventional nested RT-PCR.

In vivo induction of mucosal immune responses by intranasal administration of chitosan microspheres containing Bordetella bronchiseptica DNT.

In vitro immune-stimulating activities of Bordetella bronchiseptica dermonecrotoxin (BBD)-loaded in chitosan microspheres (CMs) were reported with a mouse alveolar macrophage cell line (RAW264.7). Based on the report, in vivo activity of immune-induction was investigated by intranasal administration of the BBD-loaded CMs into mice. BBD was loaded into the CMs prepared by an ionic gelation process with tripolyphosphate. Mice were immunized by direct administration of the BBD-loaded CMs into the nasal cavity. After immunization of the mice, BBD-specific immune responses (IgG and IgA titers) were measured in sera, nasal wash, and saliva by ELISA. BBD-specific IgA titers in the nasal cavity were time- and dose-dependently increased by the administration. Similar phenomena were observed in the analysis of systemic IgA and IgG in sera. However, the antibody in saliva was undetectable by ELISA. These results suggested that direct vaccination via the nasal cavity was effective for targeting nasal-associated lymphoid tissues, and that CMs were an efficient adjuvant in nasal mucosal immunity for atrophic rhinitis vaccine.

Identification of novel human hepatitis E virus (HEV) isolates and determination of the seroprevalence of HEV in Korea.

Hepatitis E virus (HEV) was originally identified as the causative agent of enterically transmitted non-A, non-B hepatitis. Recently, HEV isolates were subsequently identified in humans and swine in many countries, including Korea. Also, public concerns regarding HEV as a potential zoonotic agent have been increasing. Therefore, we attempted to identify HEV from Korean sera and compare the nucleotide sequences with those of previously identified HEV isolates from other countries. In our study, viral RNA was purified from 568 human sera collected from different regions of Korea. Nested PCR and reverse transcriptase PCR were developed based on the nucleotide sequences of open reading frame 2 (ORF 2) of U.S. and Japanese HEV isolates from humans and Korean HEV isolates from swine. After amplification of the HEV ORF 2 gene from 14 serum samples that were collected mainly from rural areas (2.64% prevalence of HEV viremia), the gene was cloned and sequenced. The isolates were classified into seven different strains, all of which belonged to genotype III. The human isolates we identified were closely related to three Korean swine isolates, with 99.2 to 92.9% nucleotide sequence homology. Our isolates were also related to the Japanese and U.S. HEV isolates, with 99.6 to 97.9% amino acid sequence homology. Human sera were collected from 361 individuals from community health centers and medical colleges. With respect to seroprevalence, 11.9% of the Korean population had anti-HEV immunoglobulin G (IgG). In individuals ranging in age from 40 to over 60 years, the prevalence of anti-HEV IgG was demonstrated by a seroprevalence of almost 15%, especially among populations in rural areas. This is the first report on the identification of human HEV in Korea. Overall, this study demonstrates that subclinical HEV infections may prevail in human populations in Korea and that there is a strong possibility that HEV is a zoonotic agent.

A thermally self-sustained micro solid-oxide fuel-cell stack with high power density.

High energy efficiency and energy density, together with rapid refuelling capability, render fuel cells highly attractive for portable power generation. Accordingly, polymer-electrolyte direct-methanol fuel cells are of increasing interest as possible alternatives to Li ion batteries. However, such fuel cells face several design challenges and cannot operate with hydrocarbon fuels of higher energy density. Solid-oxide fuel cells (SOFCs) enable direct use of higher hydrocarbons, but have not been seriously considered for portable applications because of thermal management difficulties at small scales, slow start-up and poor thermal cyclability. Here we demonstrate a thermally self-sustaining micro-SOFC stack with high power output and rapid start-up by using single chamber operation on propane fuel. The catalytic oxidation reactions supply sufficient thermal energy to maintain the fuel cells at 500-600 degrees C. A power output of approximately 350 mW (at 1.0 V) was obtained from a device with a total cathode area of only 1.42 cm2.