Cyclic Voltammetry for Accurate Icing Detection on Simulated Aircraft Surfaces.

Icing and ice accretion on aerodynamically critical surfaces of an aircraft increase drag, reduce lift, and raise stalling speed, which pose significant safety hazards to aircraft while in flight. Icephobic coatings have been intensively investigated by the Canadian and global aerospace industries for passive ice protection. Nevertheless, effective icephobic coatings suitable for aerospace applications are far from ideal. Ice protection of an aircraft still relies on active ice protection systems based on heating, mechanical expulsion, and deicing fluids, which are heavy-weight, power-intensive, and unfriendly to the environment. To address these challenges, rapid and accurate detection of icing is highly desirable to activate these ice protection systems only when needed. To this end, cyclic voltammetry was used for the first time to detect the initiation of icing on aircraft surfaces with or without icephobic coatings. In this study, a water droplet was sandwiched between a screen-printed electrode and a simulated aircraft surface. Cyclic voltammograms were then collected as the temperature was slowly decreased until the droplet froze to form ice. A sharp spike in faradaic current was recorded in the voltammograms during the phase transition, suggesting a switch in the mass transfer mechanism from diffusion to a surface-confined pathway. This electrochemical signal could then be used to precisely indicate the onset of icing. The developed sensing method shows potential in icing detection to manage active ice protections and ameliorate icing risks in the aerospace and aviation industries.

Actinide Decorporation: A Review on Chelation Chemistry and Nanocarriers for Pulmonary Administration.

Chelation is considered the best method for detoxification by promoting excretion of actinides (Am, Np, Pu, Th, U) from the human body after internal contamination. Chemical agents that possess carboxylic acid or hydroxypyridinonate groups play a vital role in actinide decorporation. In this review article, we provide considerable background details on the chelation chemistry of actinides with an aim to formulate better decorporation agents. Nanocarriers for pulmonary delivery represent an exciting prospect in the development of novel therapies for actinide decorporation that both reduce toxic side effects of the agent and improve its retention in the body. Recent studies have demonstrated the benefits of using a nebulizer or an inhaler to administer chelating agents for the decorporation of actinides. Effective chelation therapy with large groups of internally contaminated people can be a challenge unless both the agent and the nanocarrier are readily available from strategic national stockpiles for radiological or nuclear emergencies. Sunflower lecithin is particularly adept at alleviating the burden of administration when used to form liposomes as a nanocarrier for pulmonary delivery of diethylenetriamine-pentaacetic acid (DTPA) or hydroxypyridinone (HOPO). Better physiologically-based pharmacokinetic models must be developed for each agent in order to minimize the frequency of multiple doses that can overload the emergency response operations.

Electrochemical Impedance Spectroscopy of Zinc Oxide Nanoparticles After Deposition on Screen Printed Electrode.

A small aliquot (10-14 µL) of ZnO nanoparticles dispersed in deionized water was deposited by evaporation to produce a dry residue on the working area of a screen-printed electrode. An electrochemical test solution containing K3Fe(CN)6 and KCl was added to the electrode surface for analysis by electrochemical impendence spectroscopy (EIS). Using this deposition analysis technique, a new relationship between the charge transfer resistance (Rct) and the amount of ZnO nanoparticles has been explored. Based on the trend of increasing Rct value with an increase of ZnO nanoparticles, a quantitative analysis method can be established to determine the mass of nanoparticles (0.01-1.00 µg) deposited from an unknown dispersion. To study the matrix effect, addition of Nafion solution to the aqueous dispersion resulted in a change of the linear range to 0.3-0.5 µg nanoparticles. Addition of methanol (10% by volume) to the aqueous dispersion changes the analysis range to 0.2-0.6 µg nanoparticles, while additional methanol (50% by volume) changes the analysis range to 0.06-1.00 µg nanoparticles. The analytical sensitivity, as indicated by the slope of each standard calibration curve, ranked as: aqueous dispersion > Nafion/aqueous dispersion > 10% methanol/aqueous dispersion > 50% methanol/aqueous dispersion. Altogether these results verify that deionized water is the best dispersion medium for EIS analysis of ZnO nanoparticles.

Ion-Trap Mass Spectrometric Analysis of Bisphenol A Interactions With Titanium Dioxide Nanoparticles and Milk Proteins.

Quantitative analysis of endocrine-disrupting molecules such as bisphenol A (BPA) in freshwater to determine their widespread occurrence in environmental resources has been challenged by various adsorption and desorption processes. In this work, ion trap mass spectrometry (ITMS) analysis of BPA was aimed at studying its molecular interactions with titanium dioxide (TiO2) nanoparticles and milk whey proteins. Addition of sodium formate prevented TiO2 nanoparticles from sedimentation while enhancing the electrospray ionization (ESI) efficiency to produce an abundance of [BPA + Na]+ ions at m/z 251.0. More importantly, the ESI-ITMS instrument could operate properly during a direct infusion of nanoparticles up to 500 µg/mL without clogging the intake capillary. Milk protein adsorption of BPA could decrease the [BPA + Na]+ peak intensity significantly unless the proteins were partially removed by curdling to produce whey, which allowed BPA desorption during ESI for quantitative analysis by ITMS.

A method for the separation of TiO2 nanoparticles from Water through encapsulation with lecithin liposomes followed by adsorption onto poly(L-lysine) coated glass surfaces.

Increasing use of nanomaterials in the consumer and pharmaceutical industries has led to emerging contamination by released nanoparticles in wastewater and drinking water, causing major concerns for public health. Titanium dioxide (TiO2) nanoparticles are one of the major nanoparticles of growing concern with a strong need for efficient removal. In this work, removal of TiO2 nanoparticles from water was investigated by first coating with polydopamine (PDA) and then encapsulating within lecithin liposomes for adsorption onto poly-l-lysine (PLL) coated glass surfaces. The PLL coating was confirmed using atomic force microscopy, with a thickness of 30 nm. An average percent removal of 58% with a standard deviation of 18% was obtained for concentrations ranging from 5 mg/L to 125 mg/L following capture experiments. This method provides a promising solution to alleviate the potential health hazard caused by TiO2 nanoparticles. It is minimally affected by such water quality variables as alkalinity, ionic strength and humic acid. No coagulation, flocculation and sedimentation stages are necessary.

ENCAPSULATED 3,4,3-LI(1,2-HOPO) IN CHITOSAN NANOPARTICLES FOR DECORPORATION VIA INHALATION.

3,4,3-LI(1,2-HOPO) has been identified as an excellent alternative for DTPA for decorporating actinides, such as Pu and Am, after internal contamination. Efforts have been focused on its application through oral administration. When 3,4,3-LI(1,2-HOPO) was encapsulated with biocompatible, biodegradable nanoparticles made of chitosan, its release from the nanoparticles to lung fluid, observed in in vitro experiments, exhibited an extended release profile. These observations were very encouraging, as this nanomedicine could lead to a reduction in the dosing frequency required to achieve the decorporation efficacy of unformulated 3,4,3-LI(1,2-HOPO) itself. In vivo release tests as well as actinide decorporation experiments, using an inhalation exposure animal model, will follow.

Aerosolization of Zn-DTPA Decorporation Agent Using Jet and Ultrasonic Nebulizers.

BACKGROUND: Chelating agents such as diethylenetriamine pentaacetic acid (DTPA) can be used as a decorporation drug in the zinc (Zn) form to treat internal radioactive contamination after exposure to plutonium or americium in a nuclear accident. Although Zn-DTPA is normally administered intravenously, inhalation of Zn-DTPA in aerosol form is a better route for direct delivery to the lungs. This work investigates the feasibility of synthesizing Zn-DTPA from three common chemicals and aerosolizing it using a jet or ultrasonic nebulizer. METHODS: The particle size distribution (PSD) of this decorporation agent at different concentrations were tested in vitro using two different methods: inertial impaction and aerodynamic time of flight. The particles were generated using either a jet nebulizer or an ultrasonic nebulizer. Two parameters, namely the mass median aerodynamic diameter and the geometric standard deviation, were assessed to determine the PSD of the generated aerosols. These parameters were obtained for different concentrations of Zn-DTPA using both nebulizers. RESULTS AND CONCLUSIONS: Zn-DTPA was successfully synthesized for decorporation purposes. Aerosol particles within the inhalable range were successfully generated by both nebulizers from four different concentrations of Zn-DTPA. It was found that the medication concentration did not affect the PSD of Zn-DTPA. The ultrasonic nebulizer was observed to produce a slightly larger aerosol particle size and required slightly longer treatment periods to deliver an effective dose to the lungs when compared with the jet nebulizer. Both nebulizers can be sustainably run to administer the agent for effective decorporation treatment of a large population after any major nuclear accident.

Mass Spectrometric Analysis of Bisphenol A Desorption from Titania Nanoparticles: Ammonium Acetate, Fluoride, Formate, and Hydroxide as Chemical Desorption Agents.

Bisphenol A (BPA) is a widely used chemical in several consumer products and a well-studied environmental toxicant, and therefore, its accurate measurement is highly demanded. However, the co-presence of nanoparticles as an emerging class of contaminants could result in inaccurate determination of BPA due to binding of BPA onto nanoparticle surface. In this study, mass spectrometry (MS) was used to investigate desorption of BPA bound on the surface of titania (TiO2) nanoparticles in water. Ammonium acetate, fluoride, formate, and hydroxide were evaluated as chemical agents for their desorption capabilities. The percentages of recovery, adsorption, and desorption were determined by this new method without requiring any prior separation of nanoparticles from BPA. MS analysis demonstrated the desorption of BPA by 10-20 mM of ammonium hydroxide for a mixture of 5 µg/mL BPA and 10 µg/mL TiO2 nanoparticles, with a desorption efficiency of 72 ± 1%. Due to adsorption of BPA onto the nanoparticle surface that was inefficient for electrospray ionization, the resulting abundance of target ions could be reduced in the detection of BPA by mass spectrometry. As such, these findings collectively promise an accurate determination of the total BPA concentration in water whether it exists in the free or bound form. Efficient desorption of contaminants from the surface of nanoparticles would improve the accuracy of the contaminant analysis by mass spectrometry.

Selective detection of ZnO nanoparticles in aqueous suspension by capillary electrophoresis analysis using dithiothreitol and L-cysteine adsorbates.

The UV detection sensitivity of ZnO nanoparticles in capillary electrophoresis (CE) analysis was selectively enhanced, by 27 or 19 folds, after adsorption of dithiothreitol (DTT) or cysteine (Cys) in 10mM sodium phosphate buffer. Adsorption equilibrium was reached within 90min for DTT but only 10min for Cys. The adsorption process was best modeled by the Langmuir isotherm, indicating the formation of a monolayer of DTT or Cys on the surface of ZnO nanoparticles. The selectivity of DTT and Cys towards ZnO nanoparticles was tested using alumina (Al2O3), ceria (CeO2), silica (SiO2) and titania (TiO2) nanoparticles. No changes in the CE-UV peak area of either adsorbates or nanoparticles were observed, indicating a lack of adsorption. Dynamic light scattering (DLS) provided similar evidence of the selectivity of both adsorbates towards ZnO. Cys also improved the colloidal stability of ZnO nanoparticles by breaking down the aggregates, as evidenced by a reduction of their average hydrodynamic diameter. This new analytical approach provides a simple and rapid methodology to detect ZnO nanoparticles selectively by CE-UV analysis with enhanced sensitivity.

Use of sub-micron sized resin particles for removal of endocrine disrupting compounds and pharmaceuticals from water and wastewater.

Endocrine disrupting compounds (EDCs) and pharmaceuticals pose a challenge for water and wastewater treatment because they exist at very low concentrations in the presence of substances at much higher concentrations competing for adsorption sites. Sub-micron sized resin particles (approximately 300nm in diameter) (SMR) were tested to evaluate their potential as a treatment for EDCs including: 17-ß estradiol (E2), 17-α ethinylestradiol (EE2), estrone (E1), bisphenol A (BPA), and diethylstilbestrol (DES) as well as 12 pharmaceuticals. SMR were able to remove 98% of spiked E2, 80% of EE2, 87% of BPA, and up to 97% of DES from water. For a 0.5ppm mixture of E2, EE2, E1, BPA and DES, the minimum removal was 24% (E2) and the maximum was 49% (DES). They were also able to remove the pharmaceuticals from deionized water and wastewater. Overall, SMR are a promising advanced treatment for removal of both EDCs and pharmaceuticals.

Electrosteric stabilization of colloidal TiO2 nanoparticles with DNA and polyethylene glycol for selective enhancement of UV detection sensitivity in capillary electrophoresis analysis.

A new approach to selectively enhance the ultraviolet (UV) detection sensitivity of titania (TiO2), albeit in the presence of silica (SiO2), alumina (Al2O3), and zinc oxide (ZnO), nanoparticles in capillary electrophoresis (CE) analysis was developed. Interactions of Triton X-100 (TX-100), polyethylene glycol (PEG), and deoxyribonucleic acid (DNA) with TiO2 nanoparticles produced larger CE-UV peaks at various enhancement factors. Single-stranded DNA (ssDNA) was a more effective adsorbate than double-stranded DNA (dsDNA) due to its flexible molecular structure that participated in a stronger interaction with TiO2 nanoparticles via its sugar-phosphate backbone. Disaggregation of TiO2 nanoparticles upon DNA binding due to electrosteric stabilization was validated using dynamic light scattering. PEG coating of TiO2-DNA nanoparticles further enhanced the UV detection sensitivity in CE analysis by providing extra electrosteric stabilization. This analytical technique, which involves binding of TiO2 nanoparticles with DNA followed by coating with PEG, has allowed us to achieve progressively an enhancement factor up to 13.0 ± 3.0 - fold in analytical sensitivity for the accurate determination of disaggregated TiO2 nanoparticles. Graphical Abstract Selective enhancement of UV detection sensitivity for TiO2 nanoparticles via electrosteric stabilization using ssDNA and PEG.

Selectivity Enhancement in Molecularly Imprinted Polymers for Binding of Bisphenol A.

Bisphenol A (BPA) is an estrogen-mimicking chemical that can be selectively detected in water using a chemical sensor based on molecularly imprinted polymers (MIPs). However, the utility of BPA-MIPs in sensor applications is limited by the presence of non-specific binding sites. This study explored a dual approach to eliminating these sites: optimizing the molar ratio of the template (bisphenol A) to functional monomer (methacrylic acid) to cross-linker (ethylene glycol dimethacrylate), and esterifying the carboxylic acid residues outside of specific binding sites by treatment with diazomethane. The binding selectivity of treated MIPs and non-treated MIPs for BPA and several potential interferents was compared by capillary electrophoresis with ultraviolet detection. Baclofen, diclofenac and metformin were demonstrated to be good model interferents to test all MIPs for selective binding of BPA. Treated MIPs demonstrated a significant decrease in binding of the interferents while offering high selectivity toward BPA. These results demonstrate that conventional optimization of the molar ratio, together with advanced esterification of non-specific binding sites, effectively minimizes the residual binding of interferents with MIPs to facilitate BPA sensing.

Combating Antimicrobial Resistance in Foodborne Microorganisms.

This review addresses an important public health hazard affecting food safety. Antimicrobial agents are used in foods to reduce or eliminate microorganisms that cause disease. Many traditional organic compounds, novel synthetic organic agents, natural products, peptides, and proteins have been extensively studied for their effectiveness as antimicrobial agents against foodborne Campylobacter spp., Escherichia coli, Listeria spp. and Salmonella. However, antimicrobial resistance can develop in microorganisms, enhancing their ability to withstand the inhibiting or killing action of antimicrobial agents. Knowledge gaps still exist with regard to the actual chemical and microbiological mechanisms that must be identified to facilitate the search for new antimicrobial agents. Technical implementation of antimicrobial active packing films and coatings against target microorganisms must also be improved for extended product shelf life. Recent advances in antimicrobial susceptibility testing can provide researchers with new momentum to pursue their quest for a resistance panacea.

Removal of endocrine disrupting compounds from wastewater using polymer particles.

This study evaluated the use of particles of molecularly imprinted and non-imprinted polymers (MIP and NIP) as a wastewater treatment method for endocrine disrupting compounds (EDCs). MIP and NIP remove EDCs through adsorption and therefore do not result in the formation of partially degraded products. The results show that both MIP and NIP particles are effective for removal of EDCs, and NIP have the advantage of not being as compound-specific as the MIP and hence can remove a diverse range of compounds including 17-ß-estradiol (E2), atrazine, bisphenol A, and diethylstilbestrol. Removal of E2 from wastewater was also tested to determine the effectiveness of NIP in the presence of interfering substances and natural organic matter. Removal of E2 from wastewater samples was high and increased with increasing NIP. NIP represent an effective way of removing a wide variety of EDCs from wastewater.

Enhanced selectivity of a molecularly imprinted polymer toward the target molecule via esterification of non-specific binding sites with diazomethane.

Diazomethane (CH(2)N(2)) was used to methylate the non-specific binding sites after molecularly imprinted polymer particles were prepared using methacrylic acid as the functional monomer, ethylene glycol dimethacrylate as the cross-linker and bisphenol A (BPA) as the template. After diazomethane treatment and subsequent removal of BPA by triethylamine, the treated molecularly imprinted polymer (TMIP) particles were tested for binding selectivity toward BPA and other organic compounds by capillary electrophoresis with ultraviolet detection. Even in the presence of compounds that were positively charged, neutral or negatively charged in the background electrolyte, BPA was selectively bound with the highest efficiency. A significant decrease in the affinity for metformin (MF, a positively charged compound), along with (13) C nuclear magnetic resonance spectra and electrophoretic mobility data, provided strong evidence for the elimination of non-specific -COOH binding sites in the TMIP particles. Only 8% of MF and 16% of diclofenac sodium salt (a negatively charged compound) remained as non-specific bindings because of hydrophobic interactions. Further comparison with poly(methyl methacrylate) revealed the true merits of the TMIP, which exhibited minimal non-specific bindings while preserving a high level of specific binding owing to molecular recognition.

Duo-molecularly imprinted polymer-coated magnetic particles for class-selective removal of endocrine-disrupting compounds from aqueous environment.

The removal of steroid and phenolic endocrine-disrupting compounds (EDCs) from an aqueous environment was investigated using magnetic particles encapsulated by a duo-molecularly imprinted polymer (duo-MIP). The effect of environmental variables on the binding efficiency was studied. Experimental results showed that the amount of EDCs adsorbed was neither affected by up to 10.0 mM NaCl nor significantly interfered by up to 10.0 mg/L humic acid. Negligible influence was observed from pH 3.3 to pH 6.8, but a decrease started at pH 9. Freundlich isotherm parameters indicated binding capacities in the order of DES > E2 ∼ E1 > BPA. The applicability of class-selective removal was verified using river water samples spiked with these EDCs at 10 µg/L; the binding efficiencies were 90, 90, 88, and 98 % for estrone (E1), 17ß-estradiol (E2), bisphenol A (BPA), and diethylstilbestrol (DES), respectively. A reuse investigation verified constant binding capacities exhibiting <2 % reduction after seven cycles of regeneration.

Competitive CE-UV binding tests for selective recognition of bisphenol A by molecularly imprinted polymer particles.

Capillary electrophoresis with ultraviolet detection (CE-UV) was used to perform competitive binding tests to demonstrate the selective recognition of bisphenol A (BPA) by molecularly imprinted polymer (MIP) particles. Cross-linking polymerization of methacrylic acid (MAA) and ethylene glycol dimethacrylate (EGDMA) in the presence of BPA yielded MIP particles with an average diameter of 164 ± 15 nm. Their ability to recognize BPA in the presence of nonionic, anionic, and cationic water contaminants was investigated. Binding efficiency was rapidly determined, after sequential injection of particles first and compounds next into the fused-silica capillary provided a short overlapping time during their electrophoretic migrations. The MIP particles exhibited high-binding efficiency (99 ± 1%) for BPA. Neither diclofenac nor metformin affected BPA binding, and 2-hydroxy-4-methoxybenzophenone was even displaced from the particles by BPA. These results verified the high selectivity of MIP toward its target compound.

Optimization of molecularly imprinted polymer method for rapid screening of 17ß-estradiol in water by fluorescence quenching.

A new method was optimized for rapid screening of 17ß-estradiol (E2) in water under 10 min. Molecularly imprinted polymer (MIP) particles (325 ± 25 nm) were added in a water sample at pH 5.5 and 20°C to form a suspension. Fluorescence emission from E2 nonspecifically bound onto the MIP particles was first quenched by large gold nanoparticles (43 ± 5 nm). The Stern-Volmer plot was linear, with dynamic quenching constants (K(sv)) of 2.9 ×10(4) M(-1). Fluorescence emission from E2 specifically bound inside the MIP particles was next quenched by small nitrite anions that easily penetrated the imprinted cavities. The Stern-Volmer plot became nonlinear, with K(sv) = 2.1 × 10(2) M(-1) and static quenching constant (V) below 1.0 M(-1). The difference between these two emission intensities varied as the initial E2 concentration in water, generating a Scatchard calibration curve with R(2) > 0.97 from 0.1 to 10 ppb.

Rapid CE-UV binding tests of environmentally hazardous compounds with polymer-modified magnetic nanoparticles.

Hazardous compounds and bacteria in water have an adverse impact on human health and environmental ecology. Polydopamine (or polypyrrole)-coated magnetic nanoparticles and polymethacrylic acid-co-ethylene glycol dimethacrylate submicron particles were investigated for their fast binding kinetics with bisphenol A, proflavine, naphthalene acetic acid, and Escherichia coli. A new method was developed for the rapid determination of % binding by sequential injection of particles first and compounds (or E. coli) next into a fused-silica capillary for overlap binding during electrophoretic migration. Only nanolitre volumes of compounds and particles were sufficient to complete a rapid binding test. After heterogeneous binding, separation of the compounds from the particles was afforded by capillary electrophoresis. % binding was influenced by applied voltage but not current flow. In-capillary coating of particles affected the % binding of compounds.

Molecularly imprinted polymers for (90)Sr urine bioassay.

A molecularly imprinted polymer (MIP) comprising dicyclohexano-18-crown-6 (DCH18C6) was synthesized as a Sr-selective sorbent for urine bioassay purposes. MIP particles (326 ± 2 nm diameter) were formed using acetone and acetonitrile (1:3 v/v) as the porogen, methacrylic acid (MAA) as the functional monomer and ethylene glycol dimethacrylate (EGDMA) as the cross-linker. The DCH18C6-MIP particles were impregnated with additional DCH18C6 and treated further with NaOH to attain better binding affinity for Sr(2+). The effects of pH, ionic strength and amount of particles were evaluated for optimal extraction of (90)Sr(2+) from urine samples, as measured by liquid scintillation analysis (LSA). After up to 94% of (90)Y was removed by precipitation with TiO(2), DCH18C6-MIP particles were applied for selective SPE of (90)Sr remaining in the urine matrix for final LSA.