Battelle Centers for Public Health Research and Evaluation

ABSTRACT described creatinine excretion (P = .0089), with peaks at about 5:00 and 19:00. The use of creatinine adjustment for Hg con centration significantly reduced the intraindividualvariation around the diurnal curve. No diurnal patterns were found for any of the porphyrinsexamined.We recommendthat, for small clinical studies using urinary Hg concentration, 24-hr sampling wouldbe ideal, butthatformassscreenings andcross-sac tional studies, spot samples may be useful because they cor relate fairly well with 24-hr averages (creatinineadjusted, r = 0.61 ; unadjusted, r = 0.74). Because of the existence of diurnal variation, for all cases using serial sampling attention should be paid to time of day. Hgandporphyrin levels insingle voidurinespecimens (spot samples)were compared with calculated 24-hr urine levels in 35 (25 male and 15 female) practicing dentists who had been occupationally exposed to low levels of elemental Hg. The study aimed to: 1) determine the individual variability for Hg and porphyrin concentrations in spot samples over a 24-hr period; 2) test for the presence of diurnal variation in urinaryHg and porphyrin concentrations; and 3) determine the time of day at which a spot sample would give a Hg concentrationclosestto the 24-hr average concentration. Results confirmed previous reports of a first-order diurnal pattern with a mid-morning peak for Hg concentration(P < .0001). A second-order model best Single-void urine samples (â€oespot― samples) are used uni versally for the assessment of occupational exposure to Hg. The spot sample is widely used because it is often impractical to collect urine samples overlonger periods oftime, especially when testing of large numbers of individuals is required, such as in industrial settings. The implicit assumption is made that the concentration of Hg in the spot sample is proportional to the 24-hr urinary Hg concentration. Yet, little is known about the validity of spot samples for the determi nation of Hg exposure. Although it has been known for de cades that significant random variation exists within mdi viduals for Hg levels determined from temporally proximal spot urine samples, few attempts have been made to charac terize this variation. Those few studies which have examined the variability of Hg excretion in urine have shown that, in addition to random intraindividual variation, there appears to exist a circadian or diurnal variability as well (Araki et at. i983; Calder et al., Receivedfor publication September 5, 1995. 1984; Mason and Calder, i994; Piotrowski et at. , i975; Vokac et at., i980; Walls and Barber, i982). This cycle is charac terized by a peak during the morning period. Although this diurnal variation has been shown to exist in highly Hg exposed workers, it has been demonstrated in nonoccupation ally exposed individuals as well (Araki et at., i98

Effect of Ethyl Ester L-Lysine Triisocyanate addition to produce reactive PLA/PCL bio-polyester blends for biomedical applications

This paper was accepted for publication in the journal Journal of the Mechanical Behavior of Biomedical Materials and the definitive published version is available at http://dx.doi.org/10.1016/j.jmbbm.2017.02.018We report in this paper the effects of Ethyl Ester L-Lysine Triisocyanate (LTI) on the physical-mechanical properties of Poly(lactide)/Poly(ε-caprolactone) (PLA/PCL) polyesters blends. The PLA/PCL ratios considered were 20/80, 50/50 and 80/20 (wt/wt %) and LTI was added in amounts of 0.0-0.5-1.0 phr. PLA and PCL reacted with LTI during processing in a Brabender twin screw internal mixer to produce block copolymers in-situ. The resulting blends have been characterized by torque measurements, uniaxial tensile tests, Differential Scanning Calorimeter, contact angle measurements with a Phosphate Buffered Saline (PBS) solution, ATR analysis and morphological SEM observations. Experimental results highlighted how LTI enhanced interaction and dispersion of the two components, resulting into a synergic effect in mechanical properties. Mechanical and physical properties can be tailored by changing the blend composition. The most noticeable trend was an increase in ductility of the mixed polymers. Besides, LTI decreased blend’s wet ability in PBS and lowered the starting of crystalline phase formation for both polymers, confirming an interaction among them. These reactive blends could find use as biomedical materials, e.g. absorbable suture threads or scaffolds for cellular growth

Structural Design Elements in Biological Materials: Application to Bioinspiration.

Eight structural elements in biological materials are identified as the most common amongst a variety of animal taxa. These are proposed as a new paradigm in the field of biological materials science as they can serve as a toolbox for rationalizing the complex mechanical behavior of structural biological materials and for systematizing the development of bioinspired designs for structural applications. They are employed to improve the mechanical properties, namely strength, wear resistance, stiffness, flexibility, fracture toughness, and energy absorption of different biological materials for a variety of functions (e.g., body support, joint movement, impact protection, weight reduction). The structural elements identified are: fibrous, helical, gradient, layered, tubular, cellular, suture, and overlapping. For each of the structural design elements, critical design parameters are presented along with constitutive equations with a focus on mechanical properties. Additionally, example organisms from varying biological classes are presented for each case to display the wide variety of environments where each of these elements is present. Examples of current bioinspired materials are also introduced for each element

Structure and mechanical properties of selected protective systems in marine organisms.

Marine organisms have developed a wide variety of protective strategies to thrive in their native environments. These biological materials, although formed from simple biopolymer and biomineral constituents, take on many intricate and effective designs. The specific environmental conditions that shape all marine organisms have helped modify these materials into their current forms: complete hydration, and variation in hydrostatic pressure, temperature, salinity, as well as motion from currents and swells. These conditions vary throughout the ocean, being more consistent in the pelagic and deep benthic zones while experiencing more variability in the nearshore and shallows (e.g. intertidal zones, shallow bays and lagoons, salt marshes and mangrove forests). Of note, many marine organisms are capable of migrating between these zones. In this review, the basic building blocks of these structural biological materials and a variety of protective strategies in marine organisms are discussed with a focus on their structure and mechanical properties. Finally, the bioinspired potential of these biological materials is discussed

Structure and mechanical properties of selected protective systems in marine organisms.

Marine organisms have developed a wide variety of protective strategies to thrive in their native environments. These biological materials, although formed from simple biopolymer and biomineral constituents, take on many intricate and effective designs. The specific environmental conditions that shape all marine organisms have helped modify these materials into their current forms: complete hydration, and variation in hydrostatic pressure, temperature, salinity, as well as motion from currents and swells. These conditions vary throughout the ocean, being more consistent in the pelagic and deep benthic zones while experiencing more variability in the nearshore and shallows (e.g. intertidal zones, shallow bays and lagoons, salt marshes and mangrove forests). Of note, many marine organisms are capable of migrating between these zones. In this review, the basic building blocks of these structural biological materials and a variety of protective strategies in marine organisms are discussed with a focus on their structure and mechanical properties. Finally, the bioinspired potential of these biological materials is discussed

THE CHEMICAL PROPERTIES OF EUROPIUM AND AMERICIUM

Author Institution: Argonne National Laboratory, Chicago; Department of Chemistry, The Ohio State University; Department of Chemistry and Chemical Biology, Stevens Institute of TechnologyTo support on-going experimental research directed towards the separation of actinides and lanthanides from nuclear waste, theoretical studies on the molecular chemistry of representative elements from these families have been initiated. Ionization potentials, optical spectra (including $f \to f$ transitions), and chemical affinities for chloride are compared for isoelectronic cations of Eu and Am. Comparisons are made with experimental data. Multi-configuration SCF and configuration interaction (CI) methods were implemented utilizing ab-initio averaged relativistic effective core potentials (AREPs), spin orbit operators (Sos), and cc-pVDZ Gaussian basis sets to represent valence orbitals. The basis sets were optimized for a balanced representation of the $+2$ and $+3$ oxidation states. The importance of utilizing so-called small core AREPs, allowing the outermost occupied s, p and d valence electrons to be included explicitly in the ab-initio calculations, will be discussed. Calculations of each of the above chemical properties will be contrasted at various levels of computational sophistication, in particular, the effects of including SO within the valence electrons as well as the number and type of configurations included in the CI. Because of the size and computational complexities associated with such large-scale ab-initio SOCI calculations on systems with many open shells, parallel processing codes are critical to effective implementation

A Multifunctional Theranostic Platform Based on Phthalocyanine-Loaded Dendrimer for Image-Guided Drug Delivery and Photodynamic Therapy

Owing to the outstanding near-infrared (NIR) optical properties, phthalocyanines (Pc) have promising potential as theranostic agents for fluorescence image-guided drug delivery and noninvasive treatment of deep tumors by photodynamic therapy (PDT). Nevertheless, clinical application of phthalocyanines is substantially limited by poor water solubility, aggregation and insufficient selectivity for cancer cells. To address these issues, we have developed a novel dendrimer-based theranostic platform for tumor-targeted delivery of phthalocyanines. The preparation procedure involved the modification of the Pc molecule with a hydrophobic linker, which significantly enhances physical encapsulation of the hydrophobic drug into a generation 4 polypropylenimine (PPI G4) dendrimer. In order to improve biocompatibility and tumor-targeted delivery, the surface of the resulting Pc–PPIG4 complexes was additionally modified with poly­(ethylene glycol) (PEG) and luteinizing hormone-releasing hormone (LHRH) peptide, respectively. The developed nanocarriers have an average diameter of 62.3 nm and narrow size distribution with a polydispersity index of 0.100. The drug encapsulation efficiency was 20% w/w, and the synthesized phthalocyanine derivative entrapped in the dendrimer-based nanocarrier exhibits a distinct NIR absorption (700 nm) and fluorescence emission (710 and 815 nm), required for an efficient PDT and fluorescence imaging. It was demonstrated that subcellular localization in vitro and organ distribution in vivo of the developed nanocarrier can be determined based on the intrinsic fluorescence properties of encapsulated phthalocyanine, validating its role as an imaging agent. The imaging experiments revealed that the LHRH targeted nanocarrier is capable of an efficient internalization into cancer cells as well as tumor accumulation when intravenously administered into mice. Finally, the prepared formulation exhibited low dark cytotoxicity (IC₅₀ = 28 μg/mL) while light irradiation of the cancer cells transfected with the developed theranostic agents resulted in significant PDT effects (IC₅₀ = 0.9 μg/mL) through excessive generation of toxic reactive oxygen species. Thus, the obtained results demonstrated significant potential of the designed dendrimer-based nanocarrier as an efficient NIR theranostic agent