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Engineering Bimetallic Nanostructures as Peroxidase Mimics for Disease Diagnosis

Published September 16, 2015

Dr. Xiaohu Xia
Assistant Professor
Department of Chemistry, Michigan Tech
September 18, 2015
Chem-Sci Room 101 3:00pm

Abstract
Peroxidase mimics (or artificial peroxidase) with dimensions at the nanoscale have received great interest as emerging artificial enzymes for biomedicine and environmental protection. While a variety of peroxidase mimics have been actively developed since 2007, limited progress has been made toward improving their catalytic efficiency. In our recent work (ACS Nano, 2015, in press, DOI: 10.1021/acsnano.5b03525), we reported a novel type of peroxidase mimic with record high efficiency. Our peroxidase mimic was engineered by depositing Ir atoms as ultrathin skins (a few atomic layers) on Pd nanocubes (i.e., Pd-Ir cubes). The Pd-Ir cubes exhibited significantly enhanced efficiency that is over 400-fold higher than that of natural peroxidase. In this talk, I will introduce the rational design, experimental synthesis, and mechanistic understanding of such a new peroxidase mimic. At the end, using human prostate specific antigen as a model example, I will highlight the application of our peroxidase mimic in ultrasensitive detection of disease biomarkers.

ON THE PROTECTIVE PROPERTIES OF GLYCINE BASED OSMOLYTES IN A THIOL REDUCING ENVIRONMENT

Published August 6, 2015

By

Michigan Technological University
Department of Chemistry
John Hausman
Advisor: Dr. Ashutosh Tiwari
Master’s Defense
Monday August 10, 2015
9:30 am, Chem-Sci 101

ON THE PROTECTIVE PROPERTIES OF GLYCINE BASED OSMOLYTES IN A THIOL REDUCING ENVIRONMENT

The protective properties of osmolytes have been studied intently for decades. Originally used to aid in the crystallization of proteins in x-ray diffraction studies, these cosolvents have been shown to reverse protein denaturation and aggregation. Osmolytes aid extremophiles in surviving harsh environments by preferentially excluding themselves from the surface of the protein, thus directing water molecules to the protein’s surface. Their use is increasing and affects the everyday consumer as these osmolytes are naturally found in many health foods and also in many daily use products such as shampoo. Consumers also supplement their diets with thiol-based antioxidants such as glutathione as part of healthier life style. However, thiol-based antioxidants in high concentration have been known to cause un-intended health issues that relate to its disulfide reducing property. The disulfide-reducing agent can cleave the proteins’ disulfide-bonds and promote misfolding and aggregation. In this thesis, we investigated the influence of commonly consumed glycine-based osmolytes on providing stability to proteins against a disulfide-reducing agent. We chose glycine, sarcosine (N-methyl glycine), di-methyl glycine (DMG), and betaine (N,N,N-trimethylglycine) with increasing number of methyl groups. An added benefit to studying this class of osmolytes is to also investigate the impact N-methyl substitution has on the osmolytes’ protective properties. We studied the effect of these osmolytes on protein aggregation using spectroscopic techniques such as UV-visible absorbance, intrinsic fluorescence and extrinsic fluorescence measurements. In addition, we carried out non-reducing SDS-PAGE to check for higher order aggregates and characterized morphology of these aggregates using scanning electron microscopy. Overall, our results show that of all the osmolytes used, glycine was the best stabilizer followed by sarcosine. Betaine and dimethylglycine did not provide effective protection against disulfide-reducing influence.

Gold Nanorod-based Theranostics for Specific Cancer Imaging and Therapy

Published August 3, 2015

By

Jianheng Bi
Original Research Proposal
Michigan Technological University
Department of Chemistry
Advisor- Dr. Haiying Liu
Tuesday August 4, 2015
9:00 am
Chem-Sci 101

ABSTRACT
This proposal describes the preparation, characterization and application of gold nanorod-based theranostics for specific cancer imaging and therapy. Cancer theranostics will be constructed by modifying the gold nanorods with near-infrared dyes and cancer-imaging peptides via silica layers and poly(ethylene glycol) tethered spacers. The thickness of the silica layers will be carefully controlled to significantly enhance the fluorescence intensity of near-infrared dyes via a surface plasma of gold nanrods while specific targeting and imaging will be achieved through strong specific multivalent interactions of cancer-homing peptide residues with cancer cells and tissues. Once specific targeting to cancer cells or tissues are achieved, thermotherapy and photodynamic therapy will be conducted to kill cancer cells and tissues via thermal heat from gold nanorods and singlet oxygen generated by photodynamic agent under near-infrared pulse laser.

Title: Soil Organic Matter Matters: Why is there so much carbon underground?

Published July 21, 2015

By

Seminars

Chemistry Seminar
Dr. Katherine Heckman, Research Biologist
USDA Forest Service, Northern Research Station
Friday July 24, 2015
Chem Sci Room 101
3:00 pm

Title: Soil Organic Matter Matters: Why is there so much carbon underground?
Abstract:
Soils contain roughly twice as much carbon as the atmosphere, and 1.5 times as much as the atmosphere and aboveground vegetation combined. Yet the mechanisms regulating the stability of this massive carbon pool remain the largest uncertainty in terrestrial carbon models. To provide context, a brief review of the soil carbon cycle and mechanisms of soil carbon stabilization will be given, followed by the results of a recent investigation into how mineral crystallinity influences soil carbon stability.

Bio:
Kate Heckman earned her PhD in Soil Science at the University of Arizona in 2010, and since then has been working for the USDA Forest Service. In addition to doing basic research involving soil, Kate also runs the Radiocarbon Collaborative, a research initiative focused on making radiocarbon analyses more accessible to earth systems researchers. Kate will be moving up to Houghton this fall where she will continue her research in the Forestry Sciences Laboratory at Michigan Tech.

Published July 20, 2015

By

Xu Xiang
PhD Defense
Doctoral Candidate, Department of Chemistry
Advisor: Dr. Patrica Heiden

Friday July 24, 2015
Memorial Union Ballroom A-1
9:00 a.m.

Novel Drug Delivery Systems: Thermo-responsive drug delivery designs and Multi-drug delivery scaffold designs

Abstract:
This research has three parts: two deal with novel medical devices for drug delivery, and one looks at properties of fish scales as an abundant waste resource that can be modified to have value in medical and other areas. This presentation discusses two novel drug delivery designs, including their synthesis and characterization. These nanoparticle devices address two current challenges in drug delivery. The first is designing a drug-carrier to more efficiently deliver toxic (e.g. chemotherapy) drugs, which harm all cells. So non-specific delivery of the drug is wasteful and harmful to the patient. Knowledge gained from a fundamental study of the effects of polymer architecture (linear amphiphilic diblock and triblock copolymers and star copolymers) and end group polarity, on thermally triggered drug delivery led to selecting two diblock copolymers to assemble into novel gold-core hybrid nanoparticles. These nanoparticles were tested for their ability to reduce low temperature release and efficiently release the drug at a triggered temperature. The second drug delivery system extended the capabilities of a new type of tissue support device (a scaffold) by showing that the system can independently control the simultaneous release of different drugs, and that the spatial distribution of these drugs within the device, called a “nanoparticle fiber”, can be controlled. Three different model drugs were assembled and their release proven, within the nanoparticle fiber. This work succeeded in yielding a novel, flexible, and robust system of assembled fibers of nanoparticles that could independently control the release of multiple drugs.

Total Synthesis of Belizentrin

Published July 1, 2015

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Total Synthesis of Belizentrin

Shahien Shahsavari
Original Research Proposal
Michigan Technological University
Department of Chemistry
Advisor- Dr. Shiyue Fang
Monday July 6, 2015
10:00 am
Chem-Sci 101

Abstract

Marine organisms are known to produce some of the most bioactive secondary metabolites found in nature. Currently, many of these marine-derived molecules are used as “first-in-class” drugs in the market. This proposal describes the total synthesis of belizentrin, a novel polyketide-derived macrocycle isolated from the marine dinoflagellate Prorocentrum belizeanum. Belizentrin has already demonstrated effective changes in neuronal survival assays in vitro at nanomolar concentrations. Additionally, its highly bioactive properties and structural similarities with other known immunosuppressant compounds make it a valuable target for medical research. However, since the extraction yield is minimal, it is essential to produce this compound in larger quantities from readily available starting materials for a complete investigation of its biological activities. The overall synthetic strategy involves a convergent late-stage coupling of three major fragments. The key features of the synthesis include iterative asymmetric allylic substitutions, titanium-catalyzed asymmetric epoxidation of terminal olefins, and the Yamaguchi macrolactonization to form the macrocyclic core of the molecule.

Valenzano on Research Funding Tour

Published June 8, 2015

By

News

Group Faculty Visit to Washington, DC

For the past five years, Michigan Tech deans and the vice president for research have sponsored a group visit to Washington, D.C. for early-career research faculty. To date, 70 Michigan Tech faculty and administrators have participated.

Trip participant, Loredana Valenzano shared these comments about the trip:

“What I enjoyed most was having the feeling that, indeed, PDs [program directors] and POs [program officers] are there to help, and to provide valuable guidance especially to those of us who are trying to build a career in the STEM in times where funding is decreasing and the competition is high. The availability to talk and somehow the capability to alleviate frustrations and anxieties which the people we had the chance to interact with provided, was a pleasant and encouraging revelation. I believe that having the occasion to see with our own eyes how the big machine on the East Coast works is absolutely a key aspect to shoot for success.”

Sarah Green Quoted by ThinkProgress

Published May 4, 2015

By

News

Professor of Chemistry Sarah Green was quoted by ThinkProgress about her contributions to the edX on-line course “Making Sense of Climate Science Denial.”

The edX course, offered by the University of Queensland, Australia, concerns theories of climate science denial, including myths, psychological and social drivers, and the influence of climate denial on public perceptions of climate change.

Green was quoted in the ThinkProgress Climate Progress article “The Massive New Online Course That Every Climate Science Denier Should Be Very Afraid Of,” stating that “educating people about facts is not sufficient.” Green, who contributed four lectures to the course, said this is especially the case when political or industry groups can “bamboozle them” with easily digestible “pseudo-facts.”

edX courses are MOOCs, or massive open online courses. “Making Sense of Climate Science Denial” is a free 7-week course taught by 13 instructors.

T Synthesis of Isobractatin and Neobractatin

Published April 20, 2015

By

Shanshan Hou
Original Research Proposal
Michigan Technological University
Department of Chemistry
Advisor- Dr. Lanrong Bi
Tuesday April 21, 2015
9:00 am
Chem-Sci 106

T Synthesis of Isobractatin and Neobractatin

Abstract
The new Garcinia derivatives, neobractatin and isobractatin, will be synthesized. These compounds are caged-prenylxanthones which are isolated from Chinese native Garcinia bracteata. They displayed strong inhibition of cancer cells, which could significantly induce cell apoptosis and inhibit autophagy. However, the compounds which are extracted from the Chinese native Garcinia species have very low yield. Total synthesis of these derivatives will provide adequate quantities for biological studies. In addition, the new synthetic methodologies could not only produce the target compounds but also give rise to their isomers which could be potential anti-tumor candidates and used for future research.

Interfaced Heterogeneous Nanodimers

Published April 9, 2015

By

Chemistry Seminar
Dr. Yugang Sun
Center for Nanoscale Materials, Argonne National Laboratory
Friday, April 17, 2015 3:00pm Chem-Sci 101

Interfaced Heterogeneous Nanodimers
Abstract:
Synthesis of interfaced nanoparticle dimers made of asymmetric compositions (i.e., interfaced heterodimers) is challenging because it is difficult to manipulate the nanoparticles’ surface properties to control the assembly and/or growth of different nanoparticles. In this presentation, the general principle will be first introduced for the formation of interfaced heterogeneous dimers made of different inorganic nanodomains that exhibit either crystalline or amorphous structures. Although many different combinations are possible, the heterodimers containing plasmonic components (e.g., gold and silver nanodomains) will be focused in this presentation to highlight a number of synthetic methods and unique properties observed in heterodimers. For example, a seed-mediated, surface-confined epitaxial overgrowth strategy is capable of synthesizing high-quality interfaced Au-Ag heterodimers with varying sizes. Au and Ag share a common face-centered cubic lattice and have nearly identical lattice constants, which facilitates epitaxial overgrowth and allows direct contact between the Au and Ag domains. The interfaced Ag nanodomains can be chemical transformed to hollow nanoshells of other materials through a galvanic replacement reaction, resulting in the formation of interfaced dimers made of solid Au nanoparticles and hollow nanoshells. Due to the direct contact between the two components in each interfaced dimer, strong coupling between them are expected to induce new properties that cannot be observed from any individual components.

Biography:

Dr. Yugang Sun is a Scientist at the Center for Nanoscale Materials, Argonne National laboratory. He received his B.S. and PhD degrees from University of Science and Technology of China in 1996 and 2011, respectively. He worked as a Postdoc at University of Washington at Seattle (with Prof. Younan Xia) from 2001 to 2003. During 2004-2004, he had been working with Prof. John Rogers at University of Illinois at Urbana-Champaign as a postdoctoral fellow. In August 2008, he was appointed as an Assistant Scientist at Argonne National laboratory. He was promoted to Scientist in January 2010.

Dr. Sun’s research interests focus on developing novel approaches for the synthesis of a wide range of nanostructures including metal nanoparticles with well-controlled morphologies, single-crystal semiconductor nanostructures with mechanical flexibility, and metal/semiconductor nanocomposites with multiple functionalities. As of now, he has published more than 130 research papers, with an h-index = 47 and citation times > 23,400. He was honored as one of the “Top 100 Materials Scientists with highest impact score (2000-2010), Rank #5” by Thomson Reuters.

Category: News