Marion Hoyer

Subcellular optochemical nanobiosensors: probes encapsulated by biologically localised embedding (PEBBLEs)

Abstract Described here are arguably the worlds smallest stand-alone devices/sensors, consisting of multicomponent nano-spheres with radii as small as 10 nm, occupying ≈1 ppb of a typical mammalian cell’s volume. The probe is prepared from up to seven ingredients and is optimised for selective and reversible analyte detection, as well as sensor stability and reproducibility. Such a sensor probe encapsulated by biologically localised embedding (PEBBLE), is delivered into a cell by a variety of minimally-invasive techniques, including a pico-injector, a gene gun, liposomal incorporation and natural ingestion. These remote nano-optodes (PEBBLEs) have been prepared for pH, calcium, magnesium, potassium and oxygen. The sensor PEBBLEs can be inserted into a cell individually, in clusters (single analyte), in sets (multi-analyte) or in ensembles (single analyte, multiple locations).

Atmospheric Sources, Transport and Deposition of Mercury in Michigan: Two Years of Event Precipitation

To assess the sources, transport and deposition of atmospheric mercury (Hg) in Michigan, a multi-site network was implemented in which Hg concentrations in event precipitation and ambient samples (vapor and participate phases) were determined. Results from the analysis of 2 years of event precipitation samples for Hg are reported here. The volume-weighted average Hg concentration in precipitation was 7.9, 10.8 and 10.2 ng/L for the Pellston, South Haven and Dexter sites, respectively. Yearly wet deposition of Hg for 1992–93 and 1993–94 was 5.8 and 5.5 μg/m2 at Pellston, 9.5 and 12.7 μg/m2 at South Haven and 8.7 and 9.1 μg/m at Dexter. A spatial gradient in both the Hg concentration and wet deposition was observed. Northern Michigan received almost half the deposition of Hg recorded at the southern Michigan sites. The concentration of Hg in precipitation exhibited a strong seasonal behavior with low values of 1.0 to 2.0 ng/L in winter and maximum values greater than 40 ng/L in summer. The spring, summer and autumn precipitation accounted for 89 to 91% of the total yearly Hg deposition. Mixed-layer back trajectories were calculated for each precipitation event to investigate the meteorological history and transport from potential Hg source regions. Elevated Hg concentrations were observed with air mass transport from the west, southwest, south, and southeast. At each of the sites precipitation events for which the Hg concentration was in the 90th and 10th percentile were-analyzed for trace elements by ICP-MS to investigate source impacts.

Wet Deposition of Mercury and Ambient Mercury Concentrations at a Site in the Lake Champlain Basin

The “Great Waters” program, established in the 1990 Clean Air Act Amendments, mandated that atmospheric deposition of hazardous air pollutants to Lake Champlain (including Hg) be assessed. An assessment of the magnitude and seasonal variation of atmospheric Hg deposition in the Lake Champlain basin was initiated in December 1992 with one year of event precipitation collection, as well as collection of vapor and particle phase Hg in ambient air. Samples were collected at the Vermont Monitoring Cooperative air monitoring site at the Proctor Maple Research Center in Underhill Center, VT. The average volume-weighted concentration for Hg in precipitation was 8.3 ng/L for the sampling year and the average amount of Hg deposited with each precipitation event was 0.069 μg/m2. The total amount of Hg deposited through precipitation during 1993 was 9.26 μg/m2/yr. A seasonal pattern for Hg in precipitation was evident, with increased concentrations and deposition during spring and summer months. Meteorological analysis indicated the highest levels of Hg in precipitation were associated with regional transport from the south regardless of season, and with transport from the west, southwest and northwest during spring and summer months. Concentrations of ambient vapor phase Hg were typical of rural locations and consistent across seasons. Ambient particulate Hg concentrations averaged 11 pg/m3 with highest concentrations during the winter months.

Optochemical nanosensors and subcellular applications in living cells

Abstract. The depth distribution and the lateral distribution of nitrogen after implantation by means of plasma immersion ion implantation (PIII) in ferritic alloys with 0.3 wt.-% Al and 3.6 wt.-% Cr has been studied by scanning Auger electron spectrometry (AES). To get information about the chemical state of nitrogen and to improve the detection limit methods of data analysis (factor analysis, LLS) have been applied to depth and line profiles, respectively. Thereby the detection limit for nitrogen was reduced from 6% to 1%.The nitrogen distribution is laterally homogeneous in the near surface region only. Depth profiles obtained at several points within the sputter crater showed that the in-depth distribution of nitrogen varies markedly between different points on the sample and from sample to sample. The nitrogen concentration in the implantation maximum corresponds to Fe2N1−x (x ≈ 0.04 ⃛ 0.18).A remarkable feature are grains having a 10 μm wide seam rich in N and a nearly nitrogen-free grain’s interior. The N/Fe ratio determined from line profiles show that the outer layer of the grains has almost the exact composition Fe4N and the transition to the nearly nitrogen-free grains interior (cN ≤ 1%) occurs within 1 ⃛ 4 μm. The same shape of the N(KLL) peak was found in depth profiles and line scans, respectively, and it corresponds to gasnitrided samples γ ′–Fe4N and ɛ–Fe2N1−x.What may be the smallest anthropogenic devices to date, spherical sensors (wireless and ®berless) with radii as small as 10 nm have been produced. This class of optochemical PEBBLE (Probe Encapsulated By Biologically Localized Embedding) sensors covers a wide range of analytes (pH, calcium, oxygen and potassium included here) with excellent spatial, temporal and chemical resolution. Examples of such sensors for the monitoring of intracellular analytes are given. Methods, such as pico-injection, liposomal delivery and gene gun bombardment, are used to inject PEBBLE sensors into single cells. These PEBBLEs have caused minimal perturbation when delivered and operated inside single mammalian cells, such as human neuroblastoma, mouse oocytes or rat alveolar macrophage.

Intrinsic Variability in Airborne Fungi: Implications for Allergen Standardization

Fungus spores are among the most abundant and least well-known of airborne allergens. While ragweed pollen reaches a peak of 5000/m3 of air, fungus spores often exceed 100,000/m3. A majority of pollen types can be identified from air samples and many common and important pollen allergens have been characterized. On the other hand, only a small fraction of different kinds of fungus spores are recognizable and allergen characterization is only beginning. In addition, it has become apparent that fungus allergen preparations from commercial sources vary widely.1,2,3 Among the possible causes for this variability are: 1)intrinsic variation between spores and mycelium with respect to antigen content; 2) somatic mutations causing allergen content changes within single cultures; 3) aging and culture variable changes; 4) strain to strain variability; 5) interspecific variability.

Detection of oxidative mutagens in an urban air-particulate extract: a preliminary study

The Ames assays strains TA98 and TA100 have been useful in characterizing complex mixtures from organic solvent extracts of particles from diesel-powered vehicles, ambient air, and other sources. In this paper we report preliminary experiments using TA102, a bacterial strain that detects compounds that can oxidize DNA, to characterize the mutagenicity of an ambient air sample collected in Ann Arbor, MI. Four sets of ambient air filters were collected in duplicate over a period of several days. The mutagenicities of methylene chloride extracts of these filters were compared using strains TA98, TA100 and TA102. The concentration-mutagenicity data for TA98 and TA100 were linear over the concentration range 0-200 micrograms extract/plate. The mutagenicity of the extracts using TA102 was much lower than the other two strains and was non-linear over the concentration range tested. These results suggest that it would be difficult to use TA102 to identify the oxidative mutagens present in an ambient air particulate extract.

Pebble Nanosensors for Real Time Intracellular Chemical Imaging

Publisher Summary This chapter discusses the probes encapsulated by biologically localized embedding (PEBBLE) nanosensors and their application in real-time intracellular imaging. PEBBLE nanosensors are submicron-sized optical sensors designed specifically for minimally invasive analyte monitoring in viable single cells with applications for real-time analysis of drug, toxin, and environmental effects on cell function. PEBBLE nanosensor is a general term that describes a family of matrices and nano-fabrication techniques used to miniaturize many existing optical sensing technologies. The main classes of PEBBLE nano-sensors are based on matrices of cross-linked polyacrylamide, cross-linked decyl methacrylate, and sol-gel silica. These matrices have been used to fabricate sensors for H + Ca 2+ , K + , Na + , Mg 2+ , Zn 2+ , Cl - , NO 2 , O 2 , NO, and glucose that range from 20 nm to 600 nm in size. A host of delivery techniques have been used successfully to deliver PEBBLE nanosensors into mouse oocytes, rat alveolar macrophages, rat C6-glioma, and human neuroblastoma cells.