Diandra L. Leslie-Pelecky

Biodistribution, Clearance, and Biocompatibility of Iron Oxide Magnetic Nanoparticles in Rats

It is essential to determine the biodistribution, clearance, and biocompatibility of magnetic nanoparticles (MNPs) for in vivo biomedical applications to ensure their safe clinical use. We have studied these aspects with our novel iron oxide MNP formulation, which can be used as a magnetic resonance imaging (MRI) agent and a drug carrier system. Changes in serum and tissue iron levels were analyzed over 3 weeks after intravenous administration of MNPs to rats. Serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (AKP) levels, and total iron-binding capacity (TIBC) were also measured with time to assess the effect of MNPs on liver function. Selected tissues were also analyzed for oxidative stress and studied histologically to determine biocompatibility of MNPs. Serum iron levels gradually increased for up to 1 week but levels slowly declined thereafter. Biodistribution of iron in various body tissues changed with time but greater fraction of the injected iron localized in the liver and spleen than in the brain, heart, kidney, and lung. Magnetization measurements of the liver and spleen samples showed a steady decrease over 3 weeks, suggesting particle degradation. Serum showed a transient increase in ALT, AST, AKP levels, and TIBC over a period of 6-24 h following MNP injection. The increase in oxidative stress was tissue dependent, reaching a peak at approximately 3 days and then slowly declining thereafter. Histological analyses of liver, spleen, and kidney samples collected at 1 and 7 days showed no apparent abnormal changes. In conclusion, our MNPs did not cause long-term changes in the liver enzyme levels or induce oxidative stress and thus can be safely used for drug delivery and imaging applications.

Magnetic nanoparticles with dual functional properties : Drug delivery and magnetic resonance imaging

There is significant interest in recent years in developing magnetic nanoparticles (MNPs) having multifunctional characteristics with complimentary roles. In this study, we investigated the drug delivery and magnetic resonance imaging (MRI) properties of our novel oleic acid-coated iron-oxide and pluronic-stabilized MNPs. The drug incorporation efficiency of doxorubicin and paclitaxel (alone or in combination) in MNPs was 74-95%; the drug release was sustained and the incorporated drugs had marginal effects on physical (size and zeta potential) and magnetization properties of the MNPs. The drugs in combination incorporated in MNPs demonstrated highly synergistic antiproliferative activity in MCF-7 breast cancer cells. The T2 relaxivity (r(2)) was higher for our MNPs than Feridex IV, whereas the T1 relaxivity (r(1)) was better for Feridex IV than for our MNPs, suggesting greater sensitivity of our MNPs than Feridex IV in T2 weighted imaging. The circulation half-life (t(1/2)), determined from the changes in the MRI signal intensity in carotid arteries in mice, was longer for our MNPs than Feridex IV (t(1/2)=31.2 vs. 6.4 min). MNPs with combined characteristics of MRI and drug delivery could be of high clinical significance in the treatment of various disease conditions.

Biomedical applications of nanotechnology

Preface. Contributors. 1. Biological Applications of Multifunctional Magnetic Nanowires. 2. Nucleic Acid Delivery and Localizing Delivery with Magnetic Nanoparticles. 3. Magnetic Nanoparticles in Cancer Diagnosis and Hyperthermic Treatment. 4. Brownian Motion In Biological Sensing. 5. Dendrimers And Hyperbranched Polymers For Drug Delivery. 6. Nanogels: Chemistry to Drug Delivery. 7. Targeted Gold Nanoparticles for Imaging and Therapy. 8. Building Blocks of Nucleic Acid Nanostructures: Unfolding Thermodynamics of Intramolecular DNA Complexes. 9. Nanotoxicology. Index. About the Editors.

Magnetic studies of iron oxide nanoparticles coated with oleic acid and Pluronic® block copolymer

We have prepared and studied iron-oxide nanoparticles coated with oleic acid (OA) and Pluronic® polymer. The mean diameter of the iron-oxide nanoparticles was 9.3(±)0.8nm. Saturation magnetization values measured at 10K varied from 66.1(±0.7)emu∕gto98.7(±0.5)emu∕g. At 300K the loops showed negligible coercive field. The peaks in zero-field-cooled susceptibility decreased from 280to168K with increasing OA concentration up to 10.6wt%, and remained nearly constant for higher concentrations. This suggests that incomplete coverage of the OA allows small, interacting agglomerates to form.

Bringing female scientists into the elementary classroom: Confronting the strength of elementary students' stereotypical images of scientists

This study explored the effectiveness of bringing female scientists into the elementary classrooms on promoting changes in the stereotypical images of scientists. Qualitative and quantitative data were collected and analyzed to illuminate changes in stereotypical images of scientists. Results indicate that despite the efforts of the scientists to encourage the students to question their image of a scientist, the students held on to stereotypical images. Instead, the students questioned the true identity of the scientists, categorizing them as teachers. The results led to questions of the strength of the image and the extent of efforts needed for students to question that image.

Self‐stabilized magnetic colloids: Ultrafine Co particles in polymers

Self‐stabilized magnetic colloids consist of magnetic particles dispersed in an appropriate matrix. Fixing the particles in a stabilizing matrix has the advantage of preventing particle agglomeration, increasing resistance to oxidation, and allowing control over the interparticle spacing and particle size. We describe the chemical synthesis of cobaltnanoparticles in a polystyrene/triphenylphosphine polymer matrix. Depending on the synthesis parameters, magnetic properties of the as‐synthesized nanocomposites range from superparamagnetic to ferromagnetic with coercivities on the order of 130 Oe. Solvent choice and polymer crosslinking significantly affect the magnetic properties. Annealing in vacuum produces coercivities of up to 600 Oe and remanence ratios of up to 0.4. Measurement of the isothermal remanence magnetization and dc demagnetization indicate the presence of both magnetizing and demagnetizing interactions, in contrast to particles synthesized without the polymer, which show no evidence for magnetizing interactions. The zero‐field‐cooled temperature‐dependent magnetization displays a cusp, while the field‐cooled magnetization increases monotonically below the cusp temperature. Glassy behavior is observed for temperatures below the cusp, although the mechanism producing this behavior is not yet understood.

High-temperature magnetic properties of mechanically alloyed SmCo/sub 5/ and YCo/sub 5/ magnets

The high-temperature coercivity of mechanically alloyed and subsequently annealed RCo/sub 5/ (R=Sm and Y) is studied. The annealed materials have the hexagonal CaCu/sub 5/ structure with 2:17 (or 1:7) regions as a minor phase. High-temperature magnetic measurements show that the coercivities of materials decrease with increasing temperature from room-temperature to 873 K, but that the temperature coefficient of the coercivity of YCo/sub 5/ is much smaller than that of SmCo/sub 6/. This behavior is explained in terms of the intrinsic temperature variation of the magnetocrystalline anisotropy.

Terms of inquiry

Teaching and learning continues to be driven by a version of professionalism that construes practice to be a form of applied science. This paper challenges that paradigm. In particular, subjecting and assimilating practical activity to a technical mode of rationality is challenged as not being the most appropriate way to approach teaching, learning, and the process that drives both of these phenomena, inquiry. Middle school science classrooms provide the contexts to explore the situated consequences of embracing the terms of inquiry. Placing inquiry at the core of the thinking and experiences of middle school science educators as a philosophical/theoretical/practical educative process to be worked with, and concomitantly, working as dynamic practice, yields working notions to be necessarily embedded, cultivating, sustaining, and nurturing inquiry in teachers’ practices. As teachers experimented directly with the working notions of seeing, relational knowing, mindful embodiment, and assessment as interrelated and interdependent with inquiry, the teaching/learning outcomes authorized more and more inquiry in teachers’—and then students’—practices. An operative and active professional model emerges out of these working notions with the lived terms of inquiry identified as participatory in nature, vigilant to the question(s) in which the inquiry originates, organic in form, and always turning back on self, as catalysts in support of inquiry.

Learning How to Make Inquiry into Electricity and Magnetism Discernible to Middle Level Teachers

As university professors we sought to disrupt the practice of giving our students the actions we felt they should imitate in their teaching practice. Instead, we sought to actively engage teachers in the creation of workable solutions to real-life problems. We accomplished this by conducting a participatory action research project. This paper illustrates our action research project focused on preparing middle level science teachers to foster inquiry-based learning in their classrooms. The findings of this study not only lead to a revised professional development opportunity for science teachers, but also provided an example of university faculty engaging in pragmatic research focused on addressing contemporary issues in K-12 science education.

On styrene-butadiene-styrene-barium ferrite nanocomposites

Abstract Magnetic investigations on a nanocomposite material obtained by spinning solutions of styrene–butadiene–styrene block copolymer containing barium ferrite nanoparticles onto Si wafers are reported. The effect of the spinning frequency on the magnetic features is discussed. It is observed that the magnetization at saturation is decreased as the spinning frequency is increased as the centrifuge force removes the magnetic nanoparticles from the solution. This is supported by the derivative of the hysteresis loops, which show two components, one with a high coercive field and another with a small coercive field. Increasing the spinning frequency increases the weight of the low coercive field component. The anisotropy in the distribution of magnetic nanoparticles, triggered eventually by the self-assembly capabilities of the matrix, is revealed by the difference between the coercive field in parallel and perpendicular configuration. It is noticed that increasing the spinning frequency enhances this difference. The effect of annealing the nanocomposite films is discussed.