The zebrafish is a powerful model organism to study the mechanisms governing transition metal ions within whole brain tissue. Zinc is one of the most abundant metal ions in the brain, playing a critical pathophysiological role in neurodegenerative diseases. The homeostasis of free, ionic zinc (Zn2+) is a key intersection point in many of these diseases, including Alzheimer’s disease and Parkinson’s disease. A Zn2+ imbalance can eventuate several disturbances that may lead to the development of neurodegenerative changes. Therefore, compact, reliable approaches that allow the optical detection of Zn2+ across the whole brain would contribute to our current understanding of the mechanisms that underlie neurological disease pathology. We developed an engineered fluorescence protein-based nanoprobe that can spatially and temporally resolve Zn2+ in living zebrafish brain tissue. The self-assembled engineered fluorescence protein on gold nanoparticles was shown to be confined to defined locations within the brain tissue, enabling site specific studies, compared to fluorescent protein-based molecular tools, which diffuse throughout the brain tissue. Two-photon excitation microscopy confirmed the physical and photometrical stability of these nanoprobes in living zebrafish (Danio rerio) brain tissue, while the addition of Zn2+ quenched the nanoprobe fluorescence. Combining orthogonal sensing methods with our engineered nanoprobes will enable the study of imbalances in homeostatic Zn2+ regulation. The proposed bionanoprobe system offers a versatile platform to couple metal ion specific linkers and contribute to the understanding of neurological diseases.
more »
« less
Bromide ion-functionalized nanoprobes for sensitive and reliable pH measurement by surface-enhanced Raman spectroscopy
4-Mercaptopyridine (4-Mpy) is a pH reporter molecule commonly used to functionalize nanoprobes for surface-enhanced Raman spectroscopy (SERS) based pH measurements. However, nanoprobes functionalized by 4-Mpy alone have low pH sensitivity and are subject to interference by halide ions in sample media. To improve nanoprobe pH sensitivity and reliability, we functionalized gold nanoparticles (AuNPs) with both 4-Mpy and bromide ion (Br − ). Br − electrostatically stabilizes protonated 4-Mpy, thus enabling sensitive SERS detection of the protonation state of 4-Mpy as a function of pH while also reducing variability caused by external halide ions. Through optimization of the functionalization parameters, including suspension pH, [4-Mpy], and [Br − ], the developed nanoprobes enable monitoring of pH from 2.1 to 10 with high SERS activity and minimal interference from halide ions within the sample matrix. As a proof of concept, we were able to track nanoprobe location and image the pH distribution inside individual cancer cells. This study provides a novel way to engineer reliable 4-Mpy-functionalized SERS nanoprobes for the sensitive analysis of spatially localized pH features in halide ion-containing microenvironments.
more »
« less
- Award ID(s):
- 1705653
- NSF-PAR ID:
- 10180018
- Date Published:
- Journal Name:
- The Analyst
- Volume:
- 144
- Issue:
- 24
- ISSN:
- 0003-2654
- Page Range / eLocation ID:
- 7326 to 7335
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
null (Ed.)A rapid and sensitive method is described for measuring perchlorate (ClO 4 − ), chlorate (ClO 3 − ), chlorite (ClO 2 − ), bromate (BrO 3 − ), and iodate (IO 3 − ) ions in natural and treated waters using non-suppressed ion chromatography with electrospray ionization and tandem mass spectrometry (NS-IC-MS/MS). Major benefits of the NS-IC-MS/MS method include a short analysis time (12 minutes), low limits of quantification for BrO 3 − (0.10 μg L −1 ), ClO 4 − (0.06 μg L −1 ), ClO 3 − (0.80 μg L −1 ), and ClO 2 − (0.40 μg L −1 ), and compatibility with conventional LC-MS/MS instrumentation. Chromatographic separations were generally performed under isocratic conditions with a Thermo Scientific Dionex AS16 column, using a mobile phase of 20% 1 M aqueous methylamine and 80% acetonitrile. The isocratic method can also be optimized for IO 3 − analysis by including a gradient from the isocratic mobile phase to 100% 1 M aqueous methylamine. Four common anions (Cl − , Br − , SO 4 2− , and HCO 3 − /CO 3 2− ), a natural organic matter isolate (Suwannee River NOM), and several real water samples were tested to examine influences of natural water constituents on oxyhalide detection. Only ClO 2 − quantification was significantly affected – by elevated chloride concentrations (>2 mM) and NOM. The method was successfully applied to quantify oxyhalides in natural waters, chlorinated tap water, and waters subjected to advanced oxidation by sunlight-driven photolysis of free available chlorine (sunlight/FAC). Sunlight/FAC treatment of NOM-free waters containing 200 μg L −1 Br − resulted in formation of up to 263 ± 35 μg L −1 and 764 ± 54 μg L −1 ClO 3 − , and up to 20.1 ± 1.0 μg L −1 and 33.8 ± 1.0 μg L −1 BrO 3 − (at pH 6 and 8, respectively). NOM strongly inhibited ClO 3 − and BrO 3 − formation, likely by scavenging reactive oxygen or halogen species. As prior work shows that the greatest benefits in applying the sunlight/FAC process for purposes of improving disinfection of chlorine-resistant microorganisms are realized in waters with lower DOC levels and higher pH, it may therefore be desirable to limit potential applications to waters containing moderate DOC concentrations ( e.g. , ∼1–2 mg C L −1 ), low Br − concentrations ( e.g. , <50 μg L −1 ), and circumneutral to moderately alkaline pH ( e.g. , pH 7–8) to strike a balance between maximizing microbial inactivation while minimizing formation of oxyhalides and other disinfection byproducts.more » « less
-
In meeting rapidly growing demands for energy and clean water, engineered systems such as unconventional oil and gas recovery and desalination processes produce large amounts of briny water. In the environment, these highly concentrated halides can be oxidized and transformed to reactive halogen radicals, whose roles in the degradation and transformation of organic pollutants have been studied. However, redox reactions between halogen radicals and heavy metal ions are still poorly understood. In this work, we found that aqueous manganese ions (Mn2+) could be oxidized to Mn oxide solids by reactive halogen radicals generated from reactions between halide ions and hydroxyl radicals or between halide ions and triplet state dissolved organic matter. In particular, more Mn2+ was oxidized by Br radicals generated from bromide ion (Br−) than by Cl radicals generated from chloride ion (Cl−), even though the concentrations of Br− in surface waters are much lower than Cl− concentrations. In addition, the highly concentrated halides greatly increased the ionic strength of the solution, affecting Mn2+ oxidation kinetics and the crystallinity and oxidation state of the newly formed Mn oxides. These newly discovered pathways involving Mn2+(aq) and reactive halogen radicals aid in understanding the generation of abiotic Mn oxide solids and forecasting their redox activities. Moreover, this work emphasizes the critical need for a better knowledge of the roles of reactive halogen radicals in inorganic redox reactions.more » « less
-
null (Ed.)Manganese (Mn) oxides are strongly oxidative and adsorptive, thus affecting natural geochemical cycling and the fate and transport of pollutants. Because abiotic Mn oxidation kinetics are known to be slow, MnIV oxides have been assumed to be formed by fast oxidation of Mn2+(aq), mediated by fungi or bacteria. Recently, our group discovered that superoxide radicals generated from nitrate photolysis, a simple reaction of nitrate ions and sunlight, can facilitate the oxidation of Mn2+(aq) to δ-MnIVO2 at a rate comparable to that of biotic processes. This finding motivated us to explore underappreciated oxidants in the environment. Considering the historically unprecedented large quantity of highly saline brine generated from energy and water production, we examined the effects of halide ions (such as Cl- and Br-) and their reactive radical species on photochemically-driven Mn2+(aq) oxidation and MnIV oxide formation. Halide ions are abundant in highly saline brine such as seawater and brackish water, as well as in effluent water from desalination and unconventional oil and gas recovery. Under circumneutral pH and ambient temperature, we found that the presence of halide ions increases the oxidation rates of Mn2+ and the quantities of formed MnIV oxides within a few hours. Moreover, because high concentrations of halide ions greatly change the ionic strengths of the systems, they affect the crystallinity of the resulting MnIV oxide phases. Our findings highlight the unexpected impacts of halogen ions on solid formations in highly saline brine and emphasize the importance of brine photochemistry.more » « less
-
more » « less
Abstract Electrochemical CO2reduction (CO2RR) on copper (Cu) shows promise for higher‐value products beyond CO. However, challenges such as the limited CO2solubility, high overpotentials, and the competing hydrogen evolution reaction (HER) in aqueous electrolytes hinder the practical realization. We propose a functionalized ionic liquid (IL) which generates ion‐CO2adducts and a hydrogen bond donor (HBD) upon CO2absorption to modulate CO2RR on Cu in a non‐aqueous electrolyte. As revealed by transient voltammetry, electrochemical impedance spectroscopy (EIS), and in situ surface‐enhanced Raman spectroscopy (SERS) complemented with image charge augmented quantum‐mechanical/molecular mechanics (IC‐QM/MM) computations, a unique microenvironment is constructed. In this microenvironment, the catalytic activity is primarily governed by the IL and HBD concentrations; former controlling the double layer thickness and the latter modulating the local proton availability. This translates to ample CO2availability, reduced overpotential, and suppressed HER where C4products are obtained. This study deepens the understanding of electrolyte effects in CO2RR and the role of IL ions towards electrocatalytic microenvironment design.
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/c9an01699f
