Characterization of fire investigators' polyaromatic hydrocarbon exposures using silicone wristbands.

BACKGROUND: Exposures to polyaromatic hydrocarbons (PAHs) contribute to cancer in the fire service. Fire investigators are involved in evaluations of post-fire scenes. In the US, it is estimated that there are up to 9000 fire investigators, compared to approximately 1.1 million total firefighting personnel. This exploratory study contributes initial evidence of PAH exposures sustained by this understudied group using worn silicone passive samplers. OBJECTIVES: Evaluate PAH exposures sustained by fire investigators at post-fire scenes using worn silicone passive samplers. Assess explanatory factors and health risks of PAH exposure at post-fire scenes. METHODS: As part of a cross-sectional study design, silicone wristbands were distributed to 16 North Carolina fire investigators, including eight public, seven private, and one public and private. Wristbands were worn during 46 post-fire scene investigations. Fire investigators completed pre- and post-surveys providing sociodemographic, occupational, and post-fire scene characteristics. Solvent extracts from wristbands were analyzed via gas chromatography-mass spectrometry (GC-MS). Results were used to estimate vapor-phase PAH concentration in the air at post-fire scenes. RESULTS: Fire investigations lasted an average of 148 minutes, standard deviation ± 93 minutes. A significant positive correlation (r=0.455, p<.001) was found between investigation duration and PAH concentrations on wristbands. Significantly greater time-normalized PAH exposures (p=0.039) were observed for investigations of newer post-fire scenes compared to older post-fire scenes. Regulatory airborne PAH exposure limits were exceeded in six investigations, based on exposure to estimated vapor-phase PAH concentrations in the air at post-fire scenes. DISCUSSION: Higher levels of off-gassing and suspended particulates at younger post-fire scenes may explain greater PAH exposure. Weaker correlations are found between wristband PAH concentration and investigation duration at older post-fire scenes, suggesting reduction of off-gassing PAHs over time. Exceedances of regulatory PAH limits indicate a need for protection against vapor-phase contaminants, especially at more recent post-fire scenes.

A Portable, Encapsulated Microbial Whole-Cell Biosensing System for the Detection of Bioavailable Copper (II) in Soil.

A portable, field deployable whole-cell biosensor was developed that can withstand the complex matrices of soil and requires minimal to no sample preparation to monitor bioavailable concentrations of the essential micronutrient copper (II). Conventional measurement of micronutrients is often complex, laboratory-based, and not suitable for monitoring their bioavailable concentration. To address this need, we developed a fluorescence based microbial whole-cell biosensing (MWCB) system encoding for a Cu2+-responsive protein capable of generating a signal upon binding to Cu2+. The sensing-reporting protein was designed by performing circular permutation on the green fluorescent protein (GFP) followed by insertion of a Cu2+ binding motif into the structure of GFP. The design included insertion of several binding motifs and creating plasmids that encoded the corresponding sensing proteins. The signal generated by the sensing-reporting protein is directly proportional to the concentration of Cu2+ in the sample. Evaluation of the resulting biosensing systems carrying these plasmids was performed prior to selection of the optimal fluorescence emitting Cu2+-binding protein. The resulting optimized biosensing system was encapsulated in polyacrylate-alginate beads and embedded in soil for detection of the analyte. Once exposed to the soil, the beads were interrogated to measure the fluorescence signal emitted by the sensing-reporting protein using a portable imaging device. The biosensor was optimized for detection of Cu2+ in terms of selectivity, sensitivity, matrix effects, detection limits, and reproducibility in both liquid and soil matrices. The limit of detection (LoD) of the optimized encapsulated biosensor was calculated as 0.27 mg/L and 1.26 mg/kg of Cu2+ for Cu2+ in solution and soil, respectively. Validation of the portable imaging tools as a potential biosensing device in the field was performed.

Reagentless electrochemical biosensors through incorporation of unnatural amino acids on the protein structure.

Typical protein biosensors employ chemical or genetic labeling of the protein, thus introducing an extraneous molecule to the wild-type parent protein, often changing the overall structure and properties of the protein. While these labeling methods have proven successful in many cases, they also have a series of disadvantages associated with their preparation and function. An alternative route for labeling proteins is the incorporation of unnatural amino acid (UAA) analogues, capable of acting as a label, into the structure of a protein. Such an approach, while changing the local microenvironment, poses less of a burden on the overall structure of the protein. L-DOPA is an analog of phenylalanine and contains a catechol moiety that participates in a quasi-reversible, two-electron redox process, thus making it suitable as an electrochemical label/reporter. The periplasmic glucose/galactose binding protein (GBP) was chosen to demonstrate this detection principle. Upon glucose binding, GBP undergoes a significant conformational change that is manifested as a change in the electrochemistry of L-DOPA. The electroactive GBP was immobilized onto gold nanoparticle-modified, polymerized caffeic acid, screen-printed carbon electrodes (GBP-LDOPA/AuNP/PCA/SPCE) for the purpose of direct measurement of glucose levels and serves as a proof-of-concept of the use of electrochemically-active unnatural amino acids as the label. The resulting reagentless GBP biosensors exhibited a highly selective and sensitive binding affinity for glucose in the micromolar range, laying the foundation for a new biosensing methodology based on global incorporation of an electroactive amino acid into the protein's primary sequence for highly selective electrochemical detection of compounds of interest.

Delivery of therapeutic agents and cells to pancreatic islets: Towards a new era in the treatment of diabetes.

Pancreatic islet cells, and in particular insulin-producing beta cells, are centrally involved in the pathogenesis of diabetes mellitus. These cells are of paramount importance for the endocrine control of glycemia and glucose metabolism. In Type 1 Diabetes, islet beta cells are lost due to an autoimmune attack. In Type 2 Diabetes, beta cells become dysfunctional and insufficient to counterbalance insulin resistance in peripheral tissues. Therapeutic agents have been developed to support the function of islet cells, as well as to inhibit deleterious immune responses and inflammation. Most of these agents have undesired effects due to systemic administration and off-target effects. Typically, only a small fraction of therapeutic agent reaches the desired niche in the pancreas. Because islets and their beta cells are scattered throughout the pancreas, access to the niche is limited. Targeted delivery to pancreatic islets could dramatically improve the therapeutic effect, lower the dose requirements, and lower the side effects of agents administered systemically. Targeted delivery is especially relevant for those therapeutics for which the manufacturing is difficult and costly, such as cells, exosomes, and microvesicles. Along with therapeutic agents, imaging reagents intended to quantify the beta cell mass could benefit from targeted delivery. Several methods have been developed to improve the delivery of agents to pancreatic islets. Intra-arterial administration in the pancreatic artery is a promising surgical approach, but it has inherent risks. Targeted delivery strategies have been developed based on ligands for cell surface molecules specific to islet cells or inflamed vascular endothelial cells. Delivery methods range from nanocarriers and vectors to deliver pharmacological agents to viral and non-viral vectors for the delivery of genetic constructs. Several strategies demonstrated enhanced therapeutic effects in diabetes with lower amounts of therapeutic agents and lower off-target side effects. Microvesicles, exosomes, polymer-based vectors, and nanocarriers are gaining popularity for targeted delivery. Notably, liposomes, lipid-assisted nanocarriers, and cationic polymers can be bioengineered to be immune-evasive, and their advantages to transport cargos into target cells make them appealing for pancreatic islet-targeted delivery. Viral vectors have become prominent tools for targeted gene delivery. In this review, we discuss the latest strategies for targeted delivery of therapeutic agents and imaging reagents to pancreatic islet cells.

Mapping carcinogen exposure across urban fire incident response arenas using passive silicone-based samplers.

Carcinogens are emitted in significant quantities at fire scenes and are a major contributor in the increased cancer risk observed in firefighters when compared to the general population. A knowledge gap exists in the current understanding of the distribution of these toxic compounds within a localized fire incident response arena. Here, we employ stationary silicone-based passive samplers at controlled live fire trainings to evaluate the deposition behavior of polyaromatic hydrocarbons (PAHs) emitted by fires. Our findings indicate significantly greater total PAH exposure in fires fueled by biomass and wood compared to fires burning cleaner fuels, such as propane. A 22% increase in total PAH deposition and a 68% increase in high molecular weight PAH deposition was recorded for biomass fueled fires compared to propane fueled fires. Furthermore, we observe that heavier molecular weight PAHs exhibit a pronounced deposition front within a certain radius of the hot zone, whereas low molecular weight PAHs are more uniformly distributed throughout the area. These findings highlight that the warm zones and cold zones of fire situations yield elevated levels of carcinogen exposure to first responders within them. We anticipate that these findings will help inform decisions made by emergency personnel when evaluating risk for the hot zone, warm zone, and cold zone of urban fires helping ease the carcinogenic risk experienced.

Design of Pd-Decorated SrTiO3/BiOBr Heterojunction Materials for Enhanced Visible-Light-Based Photocatalytic Reactivity.

The development of photocatalytic materials that exploit visible light is imperative for their sustainable application in environmental remediation. While a variety of approaches have been attempted, facile routes to achieve such structures remain limited. In this contribution, a direct route for the production of a SrTiO3/BiOBr/Pd heterojunction is presented that employs a low temperature, sustainable production method. The materials were produced in a two-step process wherein BiOBr nanoplates are fabricated in the presence of the SrTiO3 nanospheres, generating a highly integrated composite material. Pd nanoparticle surface decoration was subsequently employed to facilitate and enhance charge separation lifetimes to optimize reactivity. The structures were fully characterized via a suite of approaches to confirm the final material composition and arrangement. Their reactivity was explored for the degradation of both colored and colorless model environmental pollutants, where the SrTiO3/BiOBr/Pd demonstrated significant reactivity using visible light, leading to substrate degradation in <10 min in some cases. The enhanced reactivity was attributed to the significant integration between materials, facilitating electron transfer. Such studies provide key information for the development of new materials with optimized visible-light-driven photocatalytic reactivity for sustainable environmental remediation.

Anion-Selective Electrodes Based On a CH-Hydrogen Bonding Bis-macrocyclic Ionophore with a Clamshell Architecture.

CH-hydrogen bonding provides access to new building blocks for making macrocyclic ionophores with high degrees of preorganization and selective anion recognition. In this study, an anion-binding ionophore in the shape of a clamshell (ClS) was employed that is composed of two cyanostar (CNstar) macrocycles with preorganized cavities linked with a 12-carbon chain. This ionophore allows for anion complexation by CH-hydrogen bonding. The potentiometric performance of membrane-based ion-selective electrodes incorporating this ionophore was evaluated. Different membrane compositions were prepared to determine the optimum concentrations of the ionophore and lipophilic additive in the membrane. The optimized electrode had a slope of -58.2 mV/decade and demonstrated an anti-Hofmeister selectivity pattern toward iodide with a nanomolar detection limit. Electrospray ionization mass spectrometry was employed to study the relative association strengths of ClS with various anions. The observed mass peaks of the ion-ionophore complexes were found to be consistent with the potentiometric selectivity pattern of the corresponding electrodes. Overall, the selectivity of the electrode could be altered by using an ionophore in which the two CNstar macrocycles are linked together with a flexible 12-carbon chain to control the molecularity of the binding event.

Design of a mediator-free, non-enzymatic electrochemical biosensor for glutamate detection.

A mediator-free, non-enzymatic electrochemical biosensor was constructed by covalent immobilization of a genetically engineered periplasmic glutamate binding protein onto gold nanoparticle-modified, screen-printed carbon electrodes (GluBP/AuNP/SPCE) for the purpose of direct measurement of glutamate levels. Glutamate serves as the predominant excitatory neurotransmitter in the central nervous system. As high levels of glutamate are an indicator of many neurologic disorders, there is a need for advancements in glutamate detection technologies. The biosensor was evaluated for glutamate detection by cyclic voltammetry. Binding of glutamate to the immobilized glutamate binding protein results in a conformational change of the latter that alters the microenvironment on the surface of the sensor, which is manifested as a change in signal. Dose-response plots correlating the electrochemical signal to glutamate concentration revealed a detection limit of 0.15 µM with a linear range of 0.1-0.8 µM. Selectivity studies confirmed a strong preferential response of the biosensor for glutamate against common interfering compounds.

Evaluation of silicone-based wristbands as passive sampling systems using PAHs as an exposure proxy for carcinogen monitoring in firefighters: Evidence from the firefighter cancer initiative.

Compared to the general population, firefighters are known to sustain greater levels of exposure to hazardous compounds, despite their personal protective equipment, also known as turnout gear. Among the most significant toxins that firefighters are chronically exposed to are polycyclic aromatic hydrocarbons (PAHs). Additionally, firefighters have also been noted to exhibit an increased incidence of certain types of cancer. Considering a probable link between exposure to PAHs and increased rates of cancer in the fire service, we aim to document ambient chemical concentrations in the firefighter work environment. Our strategy involves the use of silicone-based wristbands that have the capacity to passively sorb PAHs. To determine if wristbands can serve as an effective chemical monitoring device for the fire service, silicone wristbands were pilot-tested as personal sampling devices for work environment risk monitoring in active-duty firefighters. Recovered wristbands underwent multiple extraction steps, followed by GC-MS analysis to demonstrate their efficacy in monitoring PAHs in the firefighter environment. Initial findings from all wristband samples taken from firefighters showed multiple exposures to various PAHs of concern for the health of the firefighters when in a fire environment. In addition to PAH monitoring, we examined known and potential sources of PAH contamination in their work environment. To that end, profiles of elevated PAH concentrations were documented at various fire stations throughout South Florida, for individual firefighters both during station duties and active fire response.

Cyanostar: C-H Hydrogen Bonding Neutral Carrier Scaffold for Anion-Selective Sensors.

Cyanostar, a pentagonal macrocyclic compound with an electropositive cavity, binds anions with CH-based hydrogen bonding. The large size of the cyanostar's cavity along with its planarity favor formation of 2:1 sandwich complexes with larger anions, like perchlorate, ClO4-, relative to the smaller chloride. We also show that cyanostar is selective for ClO4- over the bulky salicylate anions by using NMR titration studies to measure affinity. The performance of this novel macrocycle as an anion ionophore in membrane ion sensors was evaluated. The cyanostar-based electrodes demonstrated a Nernstian response toward perchlorate with selectivity patterns distinctly different from the normal Hofmeister series. Different membrane compositions were explored to identify the optimum concentrations of the ionophore, plasticizer, and lipophilic additive that give rise to the best perchlorate selectivity. Changing the concentration of the lipophilic additive tridodecylmethylammonium chloride was found to impact the selectivity pattern and the analytical dynamic range of the electrodes. The high selectivity of the cyanostar sensors and their detection limit could enable the determination of ClO4- in contaminated environmental samples. This novel class of macrocycle provides a suitable scaffold for designing various anion-selective ionophores by altering the size of the central cavity and its functionalization.

Correlating the potentiometric selectivity of cyclosporin-based electrodes with binding patterns obtained from electrospray ionization-mass spectrometry.

Electrospray ionization mass spectrometry ESI-MS is a powerful technique for the characterization of macromolecules and their noncovalent binding with guest ions. We herein evaluate the feasibility of using ESI-MS as a screening tool for predicting potentiometric selectivities of ionophores. Ion-selective electrodes based on the cyclic peptide, cyclosporin A, were developed, and their potentiometric selectivity pattern was evaluated. Optimized electrodes demonstrated near-Nernstian slopes with micromolar detection limits toward calcium. ESI-MS and ESI-MS/MS were employed to determine the relative association strengths of cyclosporin A with various cations. The observed MS intensities of ion-ionophore complexes correlate favorably with the potentiometric selectivity pattern that was demonstrated by cyclosporin-based electrodes. This correlation was found to hold true for other established ionophores, such as valinomycin and benzo-18-crown-6. Taken together, these experiments demonstrate that mass spectrometry could be used to predict the selectivity patterns of new ionophores for potentiometric and optical ion sensors. Further, this approach could be useful in screening mixtures or libraries of newly-synthesized compounds to identify selective ionophores.

Converting Light Energy to Chemical Energy: A New Catalytic Approach for Sustainable Environmental Remediation.

We report a synthetic approach to form cubic Cu2O/Pd composite structures and demonstrate their use as photocatalytic materials for tandem catalysis. Pd nanoparticles were deposited onto Cu2O cubes, and their tandem catalytic reactivity was studied via the reductive dehalogenation of polychlorinated biphenyls. The Pd content of the materials was gradually increased to examine its influence on particle morphology and catalytic performance. Materials were prepared at different Pd amounts and demonstrated a range of tandem catalytic reactivity. H2 was generated via photocatalytic proton reduction initiated by Cu2O, followed by Pd-catalyzed dehalogenation using in situ generated H2. The results indicate that material morphology and composition and substrate steric effects play important roles in controlling the overall reaction rate. Additionally, analysis of the postreacted materials revealed that a small number of the cubes had become hollow during the photodechlorination reaction. Such findings offer important insights regarding photocatalytic active sites and mechanisms, providing a pathway toward converting light-based energy to chemical energy for sustainable catalytic reactions not typically driven via light.

Environmental PCBs in Guánica Bay, Puerto Rico: implications for community health.

Guánica Bay, located in southwestern Puerto Rico, has suffered oil spills and other pollution discharges since the 1960s. Previous research showed elevated concentrations of polychlorinated biphenyls (PCBs) in coral reef and sediment. This research examined PCB concentrations in sediment and fish. Sediment and fish sampling in the bay was facilitated by community members. This study identified the second highest reported PCB level (129,300 ng/g) in sediment in the USA. Fish samples also showed elevated concentrations (1623 to 3768 ng/g), which were higher than the thresholds of safe levels of PCBs in fish for human consumption. The alarmingly high concentration of PCBs calls for proactive community engagement to bring awareness about contamination of the bay and more extensive sampling to test for the concentration of PCBs in seafood and the people of Guánica. This study also underscores the value of the involvement of local communities during sampling design aimed at identifying hot spots of contaminants.

Direct Synthetic Control over the Size, Composition, and Photocatalytic Activity of Octahedral Copper Oxide Materials: Correlation Between Surface Structure and Catalytic Functionality.

We report a synthetic approach to form octahedral Cu2O microcrystals with a tunable edge length and demonstrate their use as catalysts for the photodegradation of aromatic organic compounds. In this particular study, the effects of the Cu(2+) and reductant concentrations and stoichiometric ratios were carefully examined to identify their roles in controlling the final material composition and size under sustainable reaction conditions. Varying the ratio and concentrations of Cu(2+) and reductant added during the synthesis determined the final morphology and composition of the structures. Octahedral particles were prepared at selected Cu(2+):glucose ratios that demonstrated a range of photocatalytic reactivity. The results indicate that material composition, surface area, and substrate charge effects play important roles in controlling the overall reaction rate. In addition, analysis of the post-reacted materials revealed photocorrosion was inhibited and that surface etching had preferentially occurred at the particle edges during the reaction, suggesting that the reaction predominately occurred at these interfaces. Such results advance the understanding of how size and composition affect the surface interface and catalytic functionality of materials.

Light-activated tandem catalysis driven by multicomponent nanomaterials.

Transitioning energy-intensive and environmentally intensive processes toward sustainable conditions is necessary in light of the current global condition. To this end, photocatalytic processes represent new approaches for H2 generation; however, their application toward tandem catalytic reactivity remains challenging. Here, we demonstrate that metal oxide materials decorated with noble metal nanoparticles advance visible light photocatalytic activity toward new reactions not typically driven by light. For this, Pd nanoparticles were deposited onto Cu2O cubes to generate a composite structure. Once characterized, their hydrodehalogenation activity was studied via the reductive dechlorination of polychlorinated biphenyls. To this end, tandem catalytic reactivity was observed with H2 generation via H2O reduction at the Cu2O surface, followed by dehalogenation at the Pd using the in situ generated H2. Such results present methods to achieve sustainable catalytic technologies by advancing photocatalytic approaches toward new reaction systems.

Polymeric plasticizer extends the lifetime of PVC-membrane ion-selective electrodes.

The nature of the plasticizer plays a pivotal role in the analytical performance of polymer membrane ion sensors. Conventional plasticizers suffer leaching or migration from the membrane and exudation, both of which could limit the lifetime of sensors based on plasticized membranes. Herein, we describe the use of polyester sebacate (PES), a model polymeric plasticizer, in the preparation of poly (vinyl chloride) (PVC) membrane ion-selective electrodes (ISEs) using valinomycin as ionophore. PVC membrane electrodes plasticized with polyester sebacate demonstrated potentiometric response characteristics that compared favorably to ones plasticized with the conventional and similarly structured plasticizer bis(2-ethylhexyl) sebacate (DOS). Increasing the content of polyester sebacate in the membrane enhanced the response and improved the selectivity of valinomycin-based ISEs toward potassium over sodium. Various methods, including electrochemical impedance spectroscopy, UV-vis spectroscopy, dark field optical microscopy, and potentiometry were employed to study the effect of plasticizer on the leaching of the membrane components and the lifetime of both DOS- and PES-plasticized membranes. PES-plasticized electrodes maintained Nernstian response and high selectivity for more than four months, an improvement over DOS-plasticized membrane electrodes. This was attributed to enhanced retention of the membrane components because of the high polymeric nature of the polyester sebacate. These characteristics suggest that polyester sebacate is a good candidate to replace the conventional plasticizers in preparing PVC membrane electrodes with longer lifetime.

Bifunctional bisphosphonates for delivering PTH (1-34) to bone mineral with enhanced bioactivity.

The objective of this work was to demonstrate the bioactivity of parathyroid hormone (1-34) (PTH) delivered through a single molecule of bisphosphonate to improve tissue/cell interactions. Bifunctional hydrazine-bisphosphonates (HBPs) with varying length and lipophilicity were used as a drug delivery vehicle. PTH was oxidized with periodate treatment to obtain an N-terminal aldehyde that was then conjugated to HBPs. The toxicity and apoptotic properties of HBPs and HBP-PTH conjugates were studied with macrophages (RAW 264.7). It was found that one of the HBPs had significant apoptotic characteristics similar to alendronate, which is a widely prescribed drug in the treatment of osteoporosis. The improved binding affinity of PTH following conjugation to HBP was determined using a hydroxyapatite binding assay. The amount of PTH delivered to bone through HBPs was not affected by the length or lipophilicity of the HBPs. Furthermore, the improved bioactivity of PTH delivered to bone through HBPs, in comparison to adsorbed PTH, was demonstrated by quantifying the cAMP produced by pre-osteoblastic (MC3T3-E1) cells in response to PTH. The delivery of bioactive PTH to bone tissue by HBP conjugation demonstrates the potential use of HBPs in delivering therapeutic macromolecules to bone for the treatment of several skeletal diseases.

Reactivity of Pd/Fe bimetallic nanotubes in dechlorination of coplanar polychlorinated biphenyls.

A new class of bimetallic materials based on palladium-decorated iron nanotubes is described that demonstrates high reactivity in dechlorination reactions. This high dechlorination efficiency was attributed to the high surface area to volume ratio of the hollow nanotubes structure. Herein, we evaluated the effect of different conditions, such as the nanotube size, and the palladium loading on the efficiency of the dechlorination of PCB 77, a model coplanar polychlorinated biphenyl (PCB), by the Pd/Fe bimetallic nanotubes system. The efficiency of the dechlorination was lowered by decreasing the tube diameter from 200 to 100 nm. In addition, the interior surface as well as the exterior surface of the as-synthesized Pd/Fe bimetallic nanotubes was found to contribute to the high efficiency of the dechlorination of PCB 77. The dechlorination of PCB 77 by Pd/Fe bimetallic nanotubes demonstrated small activation energy indicating diffusion controlled reaction. The as-prepared Pd/Fe bimetallic nanotubes showed extended lifetime activity when used in multiple dechlorination cycles.

Palladium nanoparticle-decorated iron nanotubes hosted in a polycarbonate porous membrane: development, characterization, and performance as electrocatalysts of ascorbic acid.

One-dimensional iron metallic nanotubes were prepared by electroless deposition within the pores of polycarbonate (PC) membranes. The longitudinal nucleation of the nanotubes along the pore walls was achieved by mounting the PC membrane between two halves of a U-shaped reaction tube. Palladium nanoparticles were post-deposited on the inner wall of the nanotubes. The composition, morphology, and structure of the Pd/Fe nanotubes were characterized by transmission electron microscopy, scanning electron microscopy, and inductively coupled plasma-atomic emission spectroscopy. A glassy carbon (GC) electrode modified with the free Pd/Fe bimetallic nanotubes (isolated after the dissolution of the host membranes) showed small improvement on the overpotential oxidation of ascorbic acid in comparison to the bare GC electrode. Alternatively, the Pd/Fe-polycarbonate membrane was covered with a sputtered gold thin layer of 10 nm from one side and mounted in a homemade electrochemical cell acting as the working electrode. The potential use of these functional membranes as catalytic surfaces for the electrochemical monitoring of ascorbic acid was investigated by cyclic voltammetry and amperometry. In the presence of a phosphate buffer solution, pH 7, Pd/Fe-polycarbonate membranes showed excellent electrocatalytic properties toward the oxidation of ascorbic acid even at potentials as low as 0 mV versus a Ag/AgCl reference electrode. In addition to the substantial lower overpotential, these electrodes offered selectivity over acetaminophen and uric acid, and a prolonged working stability without the need for maintenance. The electrodes were kept dry between different working days and retained their original activity for more than 1 week. Pd-polycarbonate and Fe-polycarbonate membranes were also developed for comparison purposes.

Bioluminescence inhibition assay for the detection of hydroxylated polychlorinated biphenyls.

Hydroxylated polychlorinated biphenyls (OH-PCBs) are an important class of contaminants that mainly originate from polychlorinated biphenyl metabolism. They may conceivably be as dangerous and persistent as the parent compounds; most prominently, OH-PCBs are endocrine disruptors. Due to increasing evidence of the presence of OH-PCBs in the environment and in living organisms, including humans, and of their toxicity, methods of detection for OH-PCBs are needed in the environmental and medical fields. Herein, we describe the development and optimization of a protein-based inhibition assay for the quantification of OH-PCBs. Specifically, the photoprotein aequorin was utilized for the detection of OH-PCBs. We hypothesized that OH-PCBs interact with aequorin, and we established that OH-PCBs actually inhibit the bioluminescence of aequorin in a dose-dependent manner. We took advantage of this phenomenon to develop an assay that is capable of detecting a wide variety of OH-PCBs with a range of detection limits, the best detection limit being 11 nM for the compound 2-hydroxy-2',3,4',5',6-pentachorobiphenyl. The viability of this system for the screening of OH-PCBs in spiked biological and environmental samples was also established. We envision the implementation of this novel bioluminescence inhibition assay as a rapid, sensitive, and cost-effective method for monitoring OH-PCBs. Furthermore, to the best of our knowledge, this is the first time aequorin has been employed to detect an analyte by the inhibition of its bioluminescence reaction. Hence, this strategy may prove to be a general approach for the development of a new generation of protein-based inhibition assays.