Infant dietary exposure to dioxin-like polychlorinated biphenyls (dlPCBs), polybrominated and mixed halogenated dibenzo-p-dioxins and furans (PBDD/Fs and PXDD/Fs) in milk samples of lactating mothers in Accra, Ghana.

In this study, polybrominated and mixed halogenated dibenzo-p-dioxins and furans (PBDD/Fs and PXDD/Fs), and dioxin-like polychlorinated biphenyls (dlPCBs) were quantified in 24 human milk samples of first-time lactating mothers from Greater Accra region in Ghana. The aims of the study were to determine the concentrations and toxic equivalent concentrations of PBDD/F, PXDD/F and dlPCBs in human milk, and to estimate an infant's daily intake. The samples were analysed for 12 dioxin-like PCBs, 7 congeners of 2,3,7,8-polybrominated dibenzo-p-dioxins and furans (PBDD/Fs), and 7 congeners of 2,3,7,8-mixed halogenated dioxins and furans (PXDD/Fs, where X = Br/Cl).

ToF-SIMS and TIRF microscopy investigation on the effects of HEMA copolymer surface chemistry on spatial localization, surface intensity, and release of fluorescently labeled keratinocyte growth factor.

The need for direct biomaterial-based delivery of growth factors to wound surfaces to aid in wound healing emphasizes the importance of interfacial interactions between the biomaterial and the wound surface. These interactions include the spatial localization of growth factor, the surface intensity of growth factor in contact with the wound, and the release profile of growth factor to the wound surface. The authors report the use of time-of-flight secondary ion mass spectrometry to determine the relationship between biomaterial surface chemistry and the spatial localization of growth factor.

Background levels of dioxin-like polychlorinated biphenyls (dlPCBs), polychlorinated, polybrominated and mixed halogenated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs, PBDD/Fs & PXDD/Fs) in sera of pregnant women in Accra, Ghana.

Human exposure data on dioxins and dioxin-like compounds (DLCs) in Ghana are limited. Based on health risks associated with dioxins and DLCs, the impact of maternal body burdens on foetal exposure is significant. This is the first study that assesses polychlorinated, polybrominated and mixed halogenated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs, PBDD/Fs and PXDD/Fs), and dioxin-like polychlorinated biphenyls (dlPCBs) in sera of primiparous Ghanaians.

The state of POPs in Ghana- A review on persistent organic pollutants: Environmental and human exposure.

Ghana is one of the top pesticide users and highest persistent organic pollutant (POP) emitters in sub-saharan Africa. Despite recent increases in published data, there is limited information on how POP concentrations have changed, post ratification of the Stockholm Convention. As a result, this review aims to address these knowledge gaps by collating available data that reported POPs in Ghanaian environmental matrices, identify spatial and temporal trends, and establish potential health risks.

Differential orientation and conformation of surface-bound keratinocyte growth factor on (hydroxyethyl)methacrylate, (hydroxyethyl)methacrylate/methyl methacrylate, and (hydroxyethyl)methacrylate/methacrylic acid hydrogel copolymers.

The development of hydrogels for protein delivery requires protein-hydrogel interactions that cause minimal disruption of the protein's biological activity. Biological activity can be influenced by factors such as orientational accessibility for receptor binding and conformational changes, and these factors can be influenced by the hydrogel surface chemistry. (Hydroxyethyl)methacrylate (HEMA) hydrogels are of interest as drug delivery vehicles for keratinocyte growth factor (KGF) which is known to promote re-epithelialization in wound healing.

Uptake and transformations of engineered nanomaterials: Critical responses observed in terrestrial plants and the model plant Arabidopsis thaliana.

With the applications of engineered nanomaterials (ENMs) continually expanding and production quickly growing, residues of ENMs will end up in the environment at levels that may be harmful to non-target organisms. Many of the tunable properties that have made them desirable, such as type, size, charge, or coating, also contribute to the current difficulties in understanding the fate of ENMs in the environment. This review article focuses on studies that investigate plant-ENM interactions, including techniques used to study these interactions and documented plant responses due to the phytotoxic effects of ENMs.

Segment fusion of ToF-SIMS images.

The imaging capabilities of time-of-flight secondary ion mass spectrometry (ToF-SIMS) have not been used to their full potential in the analysis of polymer and biological samples. Imaging has been limited by the size of the dataset and the chemical complexity of the sample being imaged. Pixel and segment based image fusion algorithms commonly used in remote sensing, ecology, geography, and geology provide a way to improve spatial resolution and classification of biological images.

Time of flight secondary ion mass spectrometry surface and in-depth study of degradation of nanosheet poly(L-lactic acid) films.

With the advent of novel fabrication technologies, free-standing poly(l-lactic acid) (PLLA) nanosheets have been shown to have enhanced performance over their micro- or macroscale equivalents as tissue engineering and drug delivery constructs. In the present research, the authors investigated the surface degradation behavior of PLLA films as a function of confinement to a quasi-two-dimensional structure, and the degradation behavior of nanoscale PLLA films as a function of the initial molecular weight and depth, using time-of-flight secondary ion mass spectrometry. The authors found that nanofilms exhibit less segregation of shorter chains to the surface than microfilms, due to the constrained geometries of these morphologies.

Use of geostatistics for remediation planning to transcend urban political boundaries.

Soil remediation plans are often dictated by areas of jurisdiction or property lines instead of scientific information. This study exemplifies how geostatistically interpolated surfaces can substantially improve remediation planning. Ordinary kriging, ordinary co-kriging, and inverse distance weighting spatial interpolation methods were compared for analyzing surface and sub-surface soil sample data originally collected by the US EPA and researchers at the University at Buffalo in Hickory Woods, an industrial-residential neighborhood in Buffalo, NY, where both lead and arsenic contamination is present.

Characteristic fragmentation of polysiloxane monolayer films by bombardment with monatomic and polyatomic primary ions in TOF-SIMS.

This study reports the characteristic fragmentation patterns from two polysiloxane polymers that form ordered overlayer on silver substrates. Results are compared for the bombardment of various monatomic and polyatomic projectiles of Cs(+), C(60)(+) (10 keV), Bi(1)(+), and Bi(3)(+) (25 keV) in the high mass range time-of-flight secondary ion mass spectrometry (TOF-SIMS) spectra. Results are reported from sub-monolayer (solution cast) coverages of poly(dimethylsiloxane)s with the number average molecular weights (M(n)) of 2200 and 6140 Da, respectively, and Langmuir-Blodgett monolayers of poly(methylphenylsiloxane) with molecular weights (MW) from 600 and 1000 Da.

Determining the protein drug release characteristics and cell adhesion to a PLLA or PLGA biodegradable polymer membrane.

Biodegradable polymers are of interest for developing controlled protein drug delivery platforms. In this study, two poly (alpha-hydroxy) esters were formulated with Aerosol-OT, a surfactant stabilizer, to encapsulate the protein keratinocyte growth factor (KGF) for controlled release KGF is involved in a number of crucial biologic processes, most notably epithelial growth and repair. The concentration of KGF that caused a biological response in vitro was determined (optimally 10 ng/mL) and compared with the release of KGF from the two biodegradable polymer membrane formulations.

Quantitative ToF-SIMS Studies of Protein Drug Release from Biodegradable Polymer Drug Delivery Membranes.

Biodegradable polymers are of interest in developing strategies to control protein drug delivery. The protein that was used in this study is Keratinocyte Growth Factor (KGF) which is a protein involved in the re-epithelialization process. The protein is stabilized in the biodegradable polymer matrix during formulation and over the course of polymer degradation with the use of an ionic surfactant Aerosol-OT (AOT) which will encapsulate the protein in an aqueous environment.

Determination of critical micelle concentration of aerosol-OT using time-of-flight secondary ion mass spectrometry fragmentation ion patterns.

Aggregation patterns and fragmentation ion data from thin film preparations of the anionic surfactant sodium bis(2-ethylhexyl) sulfosuccinate (aka Aerosol-OT (AOT)) near the critical micelle concentration (CMC) in carbon tetrachloride were determined using time-of-flight secondary ion mass spectrometry (ToF-SIMS). Previous work using electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to determine the chemical structure of AOT aggregates was compared to data from ToF-SIMS results from both positive and negative ion spectra. Quasi-molecular ions were detected for AOT in the positive and negative spectra at m/z 467 and 421, respectively, corresponding to [AOT+Na]+ and [AOT-Na]-.

Phase separation at the surface of poly(ethylene oxide)-containing biodegradable poly(L-lactic acid) blends.

The surface chemistry and in-depth distribution of the composition of a poly(ethylene oxide) (PEO)-containing biodegradable poly(L-lactic acid) (PLLA) blend matrix system have been investigated using X-ray photoelectron spectroscopy (XPS). This study reports detailed quantitative compositional information using a novel numerical method for determining depth profiles. The PEO system studied is an amphiphilic Pluronic P104 surfactant, PEO-b-poly(propylene oxide) (PPO)-b-PEO.

Miscibility and hydrolytic behavior of poly(trimethylene carbonate) and poly(L-lactide) and their blends in monolayers at the air/water interface.

In this study, two biodegradable polymers, poly(trimethylene carbonate) (PTMC) and poly(L-lactide) (PLLA) along with a series of PTMC/PLLA blends, were used as spreading materials to form LB monolayers at the air/water interface to study hydrolytic reaction kinetics of the monolayers with the Langmuir film balance technique. The pi-A isotherms of each homopolymer and their blends showed that blends of PTMC and PLLA were miscible on the neutral subphase (pH 7.4), whereas there was evidence of phase separation on the basic subphase (pH 10.

Spatial analysis of time of flight-secondary ion mass spectrometric images by ordinary kriging and inverse distance weighted interpolation techniques.

Ordinary kriging and inverse distance weighted (IDW) are two interpolation methods for spatial analysis of data and are commonly used to analyze macroscopic spatial data in the fields of remote sensing, geography, and geology. In this study, these two interpolation techniques were compared and used to analyze microscopic chemical images created from time of flight-secondary ion mass spectrometry images from a patterned polymer sample of fluorocarbon (C(x)F(y)) and poly(aminopropyl siloxane) (APS, a.k.

Formation of high-mass cluster ions from compound semiconductors using time-of-flight secondary ion mass spectrometry with cluster primary ions.

The detection of high-mass, nonstoichiometric, GaxAsy and InxPy secondary ion clusters using time-of-flight secondary ion mass spectrometry is reported for the first time. The GaxAsy and InxPy clusters are detected in both positive and negative ion spectra and extend to masses of at least 6000 dalton (Da). Consecutive clusters differ by the addition of one gallium (indium) atom.

Guest aggregation within poly(L-lactic acid)/pluronic P104 thin films.

Rhodamine 6G (R6G) doped thin films composed of poly(L-lactic acid) (PLLA) and Pluronic P104 were spin cast onto glass microscope slides and characterized by ultraviolet-visible, steady-state, and time-resolved fluorescence spectroscopy. The results show that R6G aggregation within the film increases as the R6G concentration and P104 loading increases. These results suggest an approach for studying drug distributions (monomers, aggregates) within biodegradable polymer formulations.

Time-of-flight secondary ion mass spectrometric analysis of polymer tertiary structure in Langmuir monolayer films of poly(dimethylsiloxane).

A series of model systems of poly(dimethylsiloxane) (PDMS) of molecular mass 2400 Da and low polydispersity (1.09) were prepared using the Langmuir-Blodgett technique to investigate the effects of tertiary structure on the ion formation probability in time-of-flight secondary ion mass spectrometry (TOF-SIMS). Using data from the measured surface pressure-area isotherm for PDMS ordered monolayer, films were transferred to silver mirror substrates from the various regions in the isotherm where structural changes are observed.

Hydrolytic behavior of enantiomeric poly(lactide) mixed monolayer films at the air/water interface: stereocomplexation effects.

The Langmuir film balance technique was used to determine the hydrolytic kinetics of monolayers of the stereocomplex formed from mixtures of enantiomeric polylactides, poly(L-lactide) (L-PLA) and poly(D-lactide) (D-PLA), spread at the air-water interface. The present study investigated parameters such as degradation medium, mixture composition, and time on the relative degradation rate. The pi-A isotherms of monolayers of the mixtures provide clear evidence for the presence of a stereocomplex; the isotherms of monolayers of individual polyenantiomer show a transition at about 8.

Depth profiling of poly(L-lactic acid)/triblock copolymer blends with time-of-flight secondary ion mass spectrometry.

Time-of-flight secondary ion mass spectrometry employing an SF5+ polyatomic primary ion source was utilized to obtain a series of in-depth profiles from PLLA/Pluronic-P104 (poly(ethylene oxide-co-propylene oxide) triblock copolymer) blends in attempts to quantify the in-depth surface segregated Pluronic region. The resultant in-depth profiles were consistent with theoretical models describing the surface segregated region in polymeric blends and copolymer systems, with a surface enriched Pluronic-P104 region, followed by a P104 depletion layer, and finally a constant composition bulk region. These results were consistent over a range of concentrations (1-25%).

Simultaneous time-of-flight secondary ion MS quantitative analysis of drug surface concentration and polymer degradation kinetics in biodegradable poly(L-lactic acid) blends.

This paper reports a new quantitative method of analyzing both the earliest stage of degradation of a polymer and the surface concentration of an additive using time-of-flight secondary ion mass spectrometry (TOF-SIMS). The static SIMS spectra of triphenylamine (Ph3N)/poly(L-lactic acid) (PLLA) (20:80 wt %) blend matrixes hydrolyzed in buffered conditions within a short-term (<48 h) period are simultaneously analyzed in the low-mass range for the surface accumulation profile of Ph3N and in the high-mass range to determine the hydrolytic degradation kinetics of PLLA, respectively. The results provide new insight in evaluating the surface concentration of Ph3N (pKb approximately 0) from the blends to see how it relates to the reactions (hydrolytic PLLA degradation) occurring in the surface region in the initial induction period over which negligible loss of polymer weight is observed.

Tailored delivery of active keratinocyte growth factor from biodegradable polymer formulations.

We report the results of a high throughput screening campaign that is aimed to develop a biodegradable polymer-based formulation to deliver active keratinocyte growth factor (KGF) and provide a means to tune the KGF delivery rate. A statistical design strategy was used to prepare and screen a series of polymer blends that were composed of poly(lactic acid) (PLA), poly(glycolic acid) (PGA), and the surfactant sodium bis(ethylhexyl)sulfosuccinate (Aerosol-OT, AOT). Chloroform was the solvent.

Analysis of the initial burst of drug release coupled with polymer surface degradation.

Purpose: Local pH effect on the release of a model pH-inert hydrophobic drug coupled with polymer degradation is described at the induction phase of biodegradable polymer erosion for better understanding the nature of initial burst of a drug.

Methods: Using a novel approach with time-of-flight secondary ion mass spectrometry. both surface concentration of Ph3N and degradation kinetics of PLLA are simultaneously and independently determined from a model Ph3N/PLLA (20:80 wt%) blend matrix (t approximately 0.