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News Article | November 18, 2016
Site: www.eurekalert.org

University of Delaware student Jonathon Cottone knows the tell-tale signs that rice plants are getting sick: the yellowing leaves, the faint football-shaped lesions. Cottone, a junior from Wilmington, Delaware, is working with Harsh Bais, associate professor of plant and soil sciences at UD, on research to help this globally important grain cope with increasing stress. Recently, the UD team found that when rice plants are subjected to multiple threats -- including increasing concentrations of poisonous arsenic in water and soil, an urgent concern in Southeast Asia, plus a fungal disease called rice blast -- the plants aren't necessarily goners. Rather, the UD researchers have shown for the first time that a combination of beneficial soil microbes can be applied to the infected plants to boost their natural defenses, combating both problems. The findings, published in Frontiers in Plant Science, provide new evidence about the potential benefit of "biostacking" -- putting multiple microbes together to protect plants from stress. The research also lends further support for a natural, chemical-free approach to protecting a crop that over half the world's population depends on for food. "We wanted to see if we could use a combinatorial approach -- a 'cocktail' of organisms -- that would help rice plants with two simultaneous stresses attacking them," Bais said, from his laboratory at the Delaware Biotechnology Institute. In addition to Bais and Cottone, the team included Venkatachalam Lakshmanan, a former postdoctoral researcher at UD who is now working at the Oklahoma-based Samuel Roberts Noble Foundation. Previously, the UD team identified two species of bacteria that come to the rescue of rice plants when the plants are under attack. The two microbes naturally inhabit the rhizosphere, the soil around the plant roots. Pseudomonas chlororaphis EA105 can trigger a system-wide defense against the rice blast fungus, which destroys enough rice to feed an estimated 60 million people each year. EA105 inhibits formation of the fungus's attack machinery, the appressoria, which acts like a battering ram, putting pressure on a plant leaf until it is punctured. A second microbe, EA106, mobilizes an iron plaque, or shield, to begin accumulating on the roots of rice plants when arsenic is present, effectively blocking uptake of the poison. "What's happening in Southeast Asia from high levels of arsenic in water and soil has been called the largest mass poisoning in history," Bais said. "The EA106 microbe has multiple benefits. The iron shield it deploys blocks the arsenic. This iron, absorbed into the rice grain, could help address another big health problem in many developing countries -- iron deficiency." In their laboratory studies with hydroponically grown rice plants, the UD team treated plants with arsenic, then treated them with EA105 and EA106. Seven days later, they infected the same plants with blast disease. Along the way, they examined the overall genetic responses when arsenic, beneficial bacteria, and fungal disease were incorporated. The resulting data clearly showed that the microbial cocktail could bolster plant defenses against both arsenic and rice blast disease. But there were some surprises. For example, the researchers thought if arsenic was taken up by rice plants, that poison might be detrimental to the blast fungus. But that was not the case. The ability of the blast fungus to tolerate arsenic is a direct story of evolution, according to Bais. The fungus has become more and more resistant to arsenic over time. "To prevent arsenic toxicity, we think the fungus put the arsenic in 'a safehouse' -- storing it in its vacuole -- before the toxin gets loaded to the grain," explained Bais. So how could beneficial microbes such as EA105 and EA106 be applied to protect rice plants? A seed treatment, or microbial coating, would be the most practical route in formulating an economical, effective product, Bais said. Next semester, Bais will travel home to India while on sabbatical leave to give talks at universities, collaborate on research and meet with people who do work in the field. "A real opportunity for India's next generation of sustainable agriculture will be this area of plant probiotics, using microbes that naturally occur in the soil to help plants," Bais said. Meanwhile, Cottone, who recently was named a DENIN Environmental Scholar at UD, will continue his research in the Bais lab, skyping with Bais while he is away. Ironically, Cottone didn't know a lot about plants until he took Bais's introductory botany course last year. Then a whole new world opened up to him, and he's now decided to pursue a double major in plant science and animal science. "This work has a huge humanitarian bent in that the majority of countries affected by arsenic poisoning are developing countries," Cottone said. "So this work could really help a lot of people who really are not in a position to help themselves." "Jonathon is doing a fantastic job," Bais said. "He puts in long hours. He's mastered how to grow rice and manages the entire greenhouse now. He's already co-authored a scientific paper as an undergrad." And he's got lots of room to flex his research muscles. The complex relationships between plants and the microorganisms living with them, their "microbiome," provide countless avenues to explore in the quest to improve plant health. "Plants are exposed to multiple stresses these days, many driven by changing climate. Plants are just confused. They don't know what to do," Bais said. "We're trying to help them cope."


Cottone, a junior from Wilmington, Delaware, is working with Harsh Bais, associate professor of plant and soil sciences at UD, on research to help this globally important grain cope with increasing stress. Recently, the UD team found that when rice plants are subjected to multiple threats—including increasing concentrations of poisonous arsenic in water and soil, an urgent concern in Southeast Asia, plus a fungal disease called rice blast—the plants aren't necessarily goners. Rather, the UD researchers have shown for the first time that a combination of beneficial soil microbes can be applied to the infected plants to boost their natural defenses, combating both problems. The findings, published in Frontiers in Plant Science, provide new evidence about the potential benefit of "biostacking"—putting multiple microbes together to protect plants from stress. The research also lends further support for a natural, chemical-free approach to protecting a crop that over half the world's population depends on for food. "We wanted to see if we could use a combinatorial approach—a 'cocktail' of organisms—that would help rice plants with two simultaneous stresses attacking them," Bais said, from his laboratory at the Delaware Biotechnology Institute. In addition to Bais and Cottone, the team included Venkatachalam Lakshmanan, a former postdoctoral researcher at UD who is now working at the Oklahoma-based Samuel Roberts Noble Foundation. Previously, the UD team identified two species of bacteria that come to the rescue of rice plants when the plants are under attack. The two microbes naturally inhabit the rhizosphere, the soil around the plant roots. Pseudomonas chlororaphis EA105 can trigger a system-wide defense against the rice blast fungus, which destroys enough rice to feed an estimated 60 million people each year. EA105 inhibits formation of the fungus's attack machinery, the appressoria, which acts like a battering ram, putting pressure on a plant leaf until it is punctured. A second microbe, EA106, mobilizes an iron plaque, or shield, to begin accumulating on the roots of rice plants when arsenic is present, effectively blocking uptake of the poison. "What's happening in Southeast Asia from high levels of arsenic in water and soil has been called the largest mass poisoning in history," Bais said. "The EA106 microbe has multiple benefits. The iron shield it deploys blocks the arsenic. This iron, absorbed into the rice grain, could help address another big health problem in many developing countries—iron deficiency." In their laboratory studies with hydroponically grown rice plants, the UD team treated plants with arsenic, then treated them with EA105 and EA106. Seven days later, they infected the same plants with blast disease. Along the way, they examined the overall genetic responses when arsenic, beneficial bacteria, and fungal disease were incorporated. The resulting data clearly showed that the microbial cocktail could bolster plant defenses against both arsenic and rice blast disease. But there were some surprises. For example, the researchers thought if arsenic was taken up by rice plants, that poison might be detrimental to the blast fungus. But that was not the case. The ability of the blast fungus to tolerate arsenic is a direct story of evolution, according to Bais. The fungus has become more and more resistant to arsenic over time. "To prevent arsenic toxicity, we think the fungus put the arsenic in 'a safehouse'—storing it in its vacuole—before the toxin gets loaded to the grain," explained Bais. So how could beneficial microbes such as EA105 and EA106 be applied to protect rice plants? A seed treatment, or microbial coating, would be the most practical route in formulating an economical, effective product, Bais said. Next semester, Bais will travel home to India while on sabbatical leave to give talks at universities, collaborate on research and meet with people who do work in the field. "A real opportunity for India's next generation of sustainable agriculture will be this area of plant probiotics, using microbes that naturally occur in the soil to help plants," Bais said. Meanwhile, Cottone, who recently was named a DENIN Environmental Scholar at UD, will continue his research in the Bais lab, skyping with Bais while he is away. Ironically, Cottone didn't know a lot about plants until he took Bais's introductory botany course last year. Then a whole new world opened up to him, and he's now decided to pursue a double major in plant science and animal science. "This work has a huge humanitarian bent in that the majority of countries affected by arsenic poisoning are developing countries," Cottone said. "So this work could really help a lot of people who really are not in a position to help themselves." "Jonathon is doing a fantastic job," Bais said. "He puts in long hours. He's mastered how to grow rice and manages the entire greenhouse now. He's already co-authored a scientific paper as an undergrad." And he's got lots of room to flex his research muscles. The complex relationships between plants and the microorganisms living with them, their "microbiome," provide countless avenues to explore in the quest to improve plant health. "Plants are exposed to multiple stresses these days, many driven by changing climate. Plants are just confused. They don't know what to do," Bais said. "We're trying to help them cope." Explore further: Microbe mobilizes 'iron shield' to block arsenic uptake in rice More information: Venkatachalam Lakshmanan et al, Killing Two Birds with One Stone: Natural Rice Rhizospheric Microbes Reduce Arsenic Uptake and Blast Infections in Rice, Frontiers in Plant Science (2016). DOI: 10.3389/fpls.2016.01514


News Article | November 18, 2016
Site: www.sciencedaily.com

University of Delaware student Jonathon Cottone knows the tell-tale signs that rice plants are getting sick: the yellowing leaves, the faint football-shaped lesions. Cottone, a junior from Wilmington, Delaware, is working with Harsh Bais, associate professor of plant and soil sciences at UD, on research to help this globally important grain cope with increasing stress. Recently, the UD team found that when rice plants are subjected to multiple threats -- including increasing concentrations of poisonous arsenic in water and soil, an urgent concern in Southeast Asia, plus a fungal disease called rice blast -- the plants aren't necessarily goners. Rather, the UD researchers have shown for the first time that a combination of beneficial soil microbes can be applied to the infected plants to boost their natural defenses, combating both problems. The findings, published in Frontiers in Plant Science, provide new evidence about the potential benefit of "biostacking" -- putting multiple microbes together to protect plants from stress. The research also lends further support for a natural, chemical-free approach to protecting a crop that over half the world's population depends on for food. "We wanted to see if we could use a combinatorial approach -- a 'cocktail' of organisms -- that would help rice plants with two simultaneous stresses attacking them," Bais said, from his laboratory at the Delaware Biotechnology Institute. In addition to Bais and Cottone, the team included Venkatachalam Lakshmanan, a former postdoctoral researcher at UD who is now working at the Oklahoma-based Samuel Roberts Noble Foundation. Previously, the UD team identified two species of bacteria that come to the rescue of rice plants when the plants are under attack. The two microbes naturally inhabit the rhizosphere, the soil around the plant roots. Pseudomonas chlororaphis EA105 can trigger a system-wide defense against the rice blast fungus, which destroys enough rice to feed an estimated 60 million people each year. EA105 inhibits formation of the fungus's attack machinery, the appressoria, which acts like a battering ram, putting pressure on a plant leaf until it is punctured. A second microbe, EA106, mobilizes an iron plaque, or shield, to begin accumulating on the roots of rice plants when arsenic is present, effectively blocking uptake of the poison. "What's happening in Southeast Asia from high levels of arsenic in water and soil has been called the largest mass poisoning in history," Bais said. "The EA106 microbe has multiple benefits. The iron shield it deploys blocks the arsenic. This iron, absorbed into the rice grain, could help address another big health problem in many developing countries -- iron deficiency." In their laboratory studies with hydroponically grown rice plants, the UD team treated plants with arsenic, then treated them with EA105 and EA106. Seven days later, they infected the same plants with blast disease. Along the way, they examined the overall genetic responses when arsenic, beneficial bacteria, and fungal disease were incorporated. The resulting data clearly showed that the microbial cocktail could bolster plant defenses against both arsenic and rice blast disease. But there were some surprises. For example, the researchers thought if arsenic was taken up by rice plants, that poison might be detrimental to the blast fungus. But that was not the case. The ability of the blast fungus to tolerate arsenic is a direct story of evolution, according to Bais. The fungus has become more and more resistant to arsenic over time. "To prevent arsenic toxicity, we think the fungus put the arsenic in 'a safehouse' -- storing it in its vacuole -- before the toxin gets loaded to the grain," explained Bais. So how could beneficial microbes such as EA105 and EA106 be applied to protect rice plants? A seed treatment, or microbial coating, would be the most practical route in formulating an economical, effective product, Bais said. Next semester, Bais will travel home to India while on sabbatical leave to give talks at universities, collaborate on research and meet with people who do work in the field. "A real opportunity for India's next generation of sustainable agriculture will be this area of plant probiotics, using microbes that naturally occur in the soil to help plants," Bais said. Meanwhile, Cottone, who recently was named a DENIN Environmental Scholar at UD, will continue his research in the Bais lab, skyping with Bais while he is away. Ironically, Cottone didn't know a lot about plants until he took Bais's introductory botany course last year. Then a whole new world opened up to him, and he's now decided to pursue a double major in plant science and animal science. "This work has a huge humanitarian bent in that the majority of countries affected by arsenic poisoning are developing countries," Cottone said. "So this work could really help a lot of people who really are not in a position to help themselves." "Jonathon is doing a fantastic job," Bais said. "He puts in long hours. He's mastered how to grow rice and manages the entire greenhouse now. He's already co-authored a scientific paper as an undergrad." And he's got lots of room to flex his research muscles. The complex relationships between plants and the microorganisms living with them, their "microbiome," provide countless avenues to explore in the quest to improve plant health. "Plants are exposed to multiple stresses these days, many driven by changing climate. Plants are just confused. They don't know what to do," Bais said. "We're trying to help them cope."


(Philadelphia, PA) - Mitochondria - the energy-generating powerhouses of cells - are also a site for oxidative stress and cellular calcium regulation. The latter two functions have long been suspected of being linked mechanistically, and now new research at the Lewis Katz School of Medicine at Temple University (LKSOM) shows precisely how, with the common connection centering on a protein complex known as the mitochondrial Ca2+ uniporter (MCU). "MCU had been known for its part in driving mitochondrial calcium uptake for cellular energy production, which protects cells from bioenergetic crisis, and for its role in eliciting calcium overload-induced cell death," explained senior investigator on the study, Muniswamy Madesh, PhD, Professor in the Department of Medical Genetics and Molecular Biochemistry and Center for Translational Medicine at LKSOM. "Now, we show that MCU has a functional role in both calcium regulation and the sensing of levels of reactive oxygen species (ROS) within mitochondria." The study, published online March 2 in the journal Molecular Cell, is the first to identify a direct role for MCU in mitochondrial ROS-sensing. In previous work, Dr. Madesh and colleagues were the first to show how the MCU protein complex comes together to effect mitochondrial calcium uptake. "We know from that work, and from existing work in the field, that as calcium accumulates in mitochondria, the organelles generate increasing amounts of ROS," Dr. Madesh said. "Mitochondria have a way of dealing with that ROS surge, and because of the relationship between mitochondrial calcium uptake and ROS production, we suspected ROS-targeting of MCU was involved in that process." In the new study, Dr. Madesh and colleagues employed advanced biochemical, cell biological, and superresolution imaging to examine MCU oxidation in the mitochondrion. Critically, they discovered that MCU contains several cysteine molecules in its amino acid structure, only one of which, Cys-97, is capable of undergoing an oxidation-induced reaction known as S-glutathionylation. Structural analyses showed that oxidation-induced S-glutathionylation of Cys-97 triggers conformational changes within MCU. Those changes in turn regulate MCU activity during inflammation, hypoxia, and cardiac stimulation. They also appear to be relevant to cell survival - elimination of ROS-sensing via Cys-97 mutation resulted in persistent MCU channel activity and an increased rate of calcium-uptake, with cells eventually dying from calcium overload. Importantly, Dr. Madesh and colleagues found that S-glutathionylation of Cys-97 is reversible. "Reversible oxidation is essential to the regulation of protein function," Dr. Madesh explained. When switched on by oxidation, Cys-97 augments MCU channel activity that perpetuates cell death. Oxidation reverses when the threat has subsided. The findings could have implications for the understanding of metabolic disorders and neurological and cardiovascular diseases. "Abnormalities in ion homeostasis are a central feature of metabolic disease," Dr. Madesh said. "We plan next to explore the functional significance of ROS and MCU activity in a mouse model using genome editing technology, which should help us answer fundamental questions about MCU's biological functions in mitochondrial ROS-sensing." Other researchers involved in the study include Zhiwei Dong, Santhanam Shanmughapriya, Dhanendra Tomar, Neeharika Nemani, Sarah L. Breves, Aparna Tripathi, Palaniappan Palaniappan, Massimo F. Riitano, Alison Worth, Ajay Seelam, Edmund Carvalho, Ramasamy Subbiah, Fabia?n Jan?a, and Sudarsan Rajan, Department of Medical Genetics and Molecular Biochemistry and the Center for Translational Medicine at LKSOM; Jonathan Soboloff, Department of Medical Genetics and Molecular Biochemistry at LKSOM; Xueqian Zhang and Joseph Y. Cheung, Center for Translational Medicine at LKSOM; Naveed Siddiqui and Peter B. Stathopulos, Department of Physiology and Pharmacology, Western University, London, Ontario, Canada; Solomon Lynch and Jeffrey Caplan, Department of Biological Sciences, Delaware Biotechnology Institute, University of Delaware; Suresh K. Joseph, MitoCare Center, Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia; Yizhi Peng and Zhiwei Dong, Institute of Burn Research, Southwest Hospital, Third Military Medical University, Chongqing, People's Republic of China. The research was supported in part by National Institutes of Health grants R01GM109882, R01HL086699, R01HL119306, 1S10RR027327, P01 DA037830, and RO1DK103558. Temple University Health System (TUHS) is a $1.6 billion academic health system dedicated to providing access to quality patient care and supporting excellence in medical education and research. The Health System consists of Temple University Hospital (TUH), ranked among the "Best Hospitals" in the region by U.S. News & World Report; TUH-Episcopal Campus; TUH-Northeastern Campus; Fox Chase Cancer Center, an NCI-designated comprehensive cancer center; Jeanes Hospital, a community-based hospital offering medical, surgical and emergency services; Temple Transport Team, a ground and air-ambulance company; and Temple Physicians, Inc., a network of community-based specialty and primary-care physician practices. TUHS is affiliated with the Lewis Katz School of Medicine at Temple University. The Lewis Katz School of Medicine (LKSOM), established in 1901, is one of the nation's leading medical schools. Each year, the School of Medicine educates approximately 840 medical students and 140 graduate students. Based on its level of funding from the National Institutes of Health, the Katz School of Medicine is the second-highest ranked medical school in Philadelphia and the third-highest in the Commonwealth of Pennsylvania. According to U.S. News & World Report, LKSOM is among the top 10 most applied-to medical schools in the nation. Temple Health refers to the health, education and research activities carried out by the affiliates of Temple University Health System (TUHS) and by the Katz School of Medicine. TUHS neither provides nor controls the provision of health care. All health care is provided by its member organizations or independent health care providers affiliated with TUHS member organizations. Each TUHS member organization is owned and operated pursuant to its governing documents.


News Article | December 22, 2015
Site: phys.org

The findings, published in December in Frontiers in Plant Science and in Current Opinion in Plant Biology, may lead to a more effective control for Magnaporthe oryzae, the fungus that causes rice blast disease. The studies were led by the laboratory of Harsh Bais, associate professor of plant and soil sciences in UD's College of Agriculture and Natural Resources. The first author of both research articles was graduate student Carla Spence. The co-authors included postdoctoral researcher Venkatachalam Laksmanan and Nicole Donofrio, associate professor of plant and soil sciences, in addition to Bais. "Rice is a food the world relies on—it accounts for about one-fifth of all the calories humans consume," says Bais. "So it's critical to find ways to reduce the impact of rice blast disease, especially as global population is expected to exceed 9 billion by 2050, and the need for more food increases." Previously, Bais and his research team isolated Pseudomonas chlororaphis EA105, a bacterium that lives in the soil around the roots of rice plants and found that this beneficial microbe can trigger a system-wide defense against the rice blast fungus. Now, they have identified a stress hormone that appears to play a crucial role in increasing the virulence of the fungus. When little water is available, rice plants make more abscisic acid in their roots. This stress hormone travels up to the plant leaves to close off tiny pores, halting the evaporation of water from the plant to the atmosphere. Bais and his team have shown that when the rice blast fungus invades a rice plant, an increase in abscisic acid occurs. But rather than boosting the plant's defense mechanisms, the abscisic acid actually suppresses them, making the pathogen even more potent. "It's like a double-edged sword," Bais says. "Abscisic acid can save the plant during drought. But when a pathogen is present, this same molecule blocks the plant's innate defense response." In studies at the Delaware Biotechnology Institute at UD, Bais and his team treated spores of the rice blast fungus with abscisic acid. In 10 hours, 84 percent of these spores had germinated and formed a specialized infection structure called the appressorium, which acts like a battering ram, exerting pressure on a rice leaf until the fungus punches through the surface. However, when spores of the fungus were treated with both the beneficial bacterium EA105 and abscisic acid, only about 23 percent of the spores formed this attack machinery. "The rice blast fungus uses abscisic acid to its own advantage, which is absolutely wild," Bais says. "People have been struggling to find targets for controlling rice blast, and now we have one, with abscisic acid. It's one of those classic holy grails because this fungus affects not only rice, but also barley and wheat." Although abscisic acid may be responsible for virulence in the rice blast fungus, the molecule itself is not a feasible target for fungicides because of its crucial roles in plants, from seed development to its modulating effect during temperature extremes and high salinity, to its well-studied role in drought tolerance. However, targeting specific genes in the fungus that biosynthesize abscisic acid could deliver the real knockout punch. "Plants and their microbial neighbors have this beautifully complex and intricate system of communicating through chemical signals, with each trying to manipulate the situation to maximize their own fitness," Bais says. "We want to be able to manage some of these interactions, too, to enhance food security."


Naik M.U.,University of Delaware | Caplan J.L.,University of Delaware | Caplan J.L.,Delaware Biotechnology Institute | Naik U.P.,University of Delaware | Naik U.P.,Delaware Biotechnology Institute
Blood | Year: 2014

Fibrinogen binding to activated integrin induces outside-in signaling that results in stable platelet aggregates and clot retraction. How integrin αIIbβ3 is discouraged from spontaneous activation is not known. We have recently shown that junctional adhesion molecule-A (JAM-A) renders protection from thrombosis by suppressing integrin outside-in signaling. In this study, we show that JAM-A associates with integrin αIIbβ3 in resting platelets and dissociates upon platelet activation by agonists. We also show that integrin-associated JAM-A is tyrosine phosphorylated and is rapidly dephosphorylated upon platelet activation. C-terminal Src kinase (Csk) binds to tyrosine phosphorylated JAM-A through its Src homology 2 domain. Thus, JAM-A recruits Csk to the integrin-c-Src complex in resting platelets. Csk, in turn, keeps integrin-associated c-Src in an inactive state by phosphorylating Y529 in its regulatory domain. Absence of JAM-A results in impaired c-SrcY529 phosphorylation and augmentation of outside-in signalingdependent c-Src activation. Our results strongly suggest that tyrosine-phosphorylated JAM-A is a Csk-binding protein and functions as an endogenous inhibitor of integrin signaling. JAM-A recruits Csk to the integrin-c-Src complex, where Csk negatively regulates c-Src activation, thereby suppressing the initiation of outside-in signaling. Upon agonist stimulation, JAM-A is dephosphorylated on the tyrosine, allowing the dissociation of Csk fromthe integrin complex, and thus facilitating outside-in signaling. © 2014 by The American Society of Hematology.


Baldwin A.D.,University of Delaware | Kiick K.L.,University of Delaware | Kiick K.L.,Delaware Biotechnology Institute
Bioconjugate Chemistry | Year: 2011

Addition chemistries are widely used in preparing biological conjugates, and in particular, maleimide-thiol adducts have been widely employed. Here, we show that the resulting succinimide thioether formed by the Michael-type addition of thiols to N-ethylmaleimide (NEM), generally accepted as stable, undergoes retro and exchange reactions in the presence of other thiol compounds at physiological pH and temperature, offering a novel strategy for controlled release. Model studies ( 1H NMR, HPLC) of NEM conjugated to 4-mercaptophenylacetic acid (MPA), N-acetylcysteine, or 3-mercaptopropionic acid (MP) incubated with glutathione showed half-lives of conversion from 20 to 80 h, with extents of conversion from 20% to 90% for MPA and N-acetylcysteine conjugates. After ring-opening, the resultant succinimide thioether did not show retro and exchange reactions. The kinetics of the retro reactions and extent of exchange can be modulated by the Michael donor's reactivity; therefore, the degradation of maleimide-thiol adducts could be tuned for controlled release of drugs or degradation of materials at time scales different than those currently possible via disulfide-mediated release. Such approaches may find a new niche for controlled release in reducing environments relevant in chemotherapy and subcellular trafficking. © 2011 American Chemical Society.


Li M.,University of Delaware | Czymmek K.J.,Delaware Biotechnology Institute | Huang C.P.,University of Delaware
Journal of Hazardous Materials | Year: 2011

The in vivo responses of C. dubia to nanoparticles exemplified by a photoactive titanium oxide (TiO2) and a non-photocatalytic aluminum oxide (Al2O3) were studied. Both nanomaterials inhibited the growth of C. dubia at concentrations ca >100mg/L. The EC50 value was 42 and 45mg/L in the presence of TiO2 and Al2O3, respectively, based on 3-brood reproduction assay. Results implied that reactive oxygen species (ROS) may not be totally responsible for the adverse effects exerted on the invertebrate. Aggregation and interaction among nanoparticles, C. dubia, and algal cells, major food source of Daphnia, played a significant role on the responses of C. dubia to nanoparticles. Dynamic energy budget (DEB) analysis was used to assess the impact of nanoparticles on the energy allocation of C. dubia. Results indicated that nanoparticles could disrupt the assimilation and consumption of energy in C. dubia dramatically. The assimilation energy was negatively correlated to the concentration of nanomaterials, a reduction from 11 to near 0μg-C/animal/day in the presence of TiO2 or Al2O3 nanoparticles at a nanoparticle concentration of 200mg/L. The energy consumed for life-maintenance increased also with increase in the concentration of nanomaterials. Results clearly demonstrated the importance of energy disruption in determining the toxicity of nanoparticles toward C. dubia. © 2011 Elsevier B.V.


Baldwin A.D.,University of Delaware | Kiick K.L.,University of Delaware | Kiick K.L.,Delaware Biotechnology Institute
Polymer Chemistry | Year: 2013

We have recently reported that retro Michael-type addition reactions can be employed for producing labile chemical linkages with tunable sensitivity to physiologically relevant reducing potentials. We reasoned that such strategies would also be useful in the design of glutathione-sensitive hydrogels for a variety of targeted delivery and tissue engineering applications. In this report, we describe hydrogels in which maleimide-functionalized low molecular weight heparin (LMWH) is crosslinked with various thiol-functionalized poly(ethylene glycol) (PEG) multi-arm star polymers. Judicious selection of the chemical identity of the thiol permits tuning of degradation via previously unstudied, but versatile chemical methods. Thiol pKa and hydrophobicity affected both the gelation and degradation of these hydrogels. Maleimide-thiol crosslinking reactions and retro Michael-type addition reactions were verified with 1H NMR during the crosslinking and degradation of hydrogels. PEGs esterified with phenylthiol derivatives, specifically 4-mercaptophenylpropionic acid or 2,2-dimethyl-3-(4-mercaptophenyl)propionic acid, induced sensitivity to glutathione as shown by a decrease in hydrogel degradation time of 4-fold and 5-fold respectively, measured via spectrophotometric quantification of LMWH. The degradation proceeded through the retro Michael-type addition of the succinimide thioether linkage, with apparent pseudo-first order reaction constants derived from oscillatory rheology experiments of 0.039 ± 0.006 h-1 and 0.031 ± 0.003 h-1. The pseudo-first order retro reaction constants were approximately an order of magnitude slower than the degradation rate constants for hydrogels crosslinked via disulfide linkages, indicating the potential use of these Michael-type addition products for reduction-mediated release and/or degradation, with increased blood stability and prolonged drug delivery timescales compared to disulfide moieties. © 2013 The Royal Society of Chemistry.


Li L.,University of Delaware | Kiick K.L.,University of Delaware | Kiick K.L.,Delaware Biotechnology Institute
ACS Macro Letters | Year: 2013

Resilin, an insect structural protein, exhibits rubber-like elasticity characterized by low stiffness, high extensibility, efficient energy storage, and exceptional resilience and fatigue lifetime. The outstanding mechanical properties of natural resilin have motivated recent research in the engineering of resilin-like polypeptide-based biomaterials, with a wide range of applications including use as biorubbers, nanosprings, elements in biosensors, and tissue engineering scaffolds. © 2013 American Chemical Society.

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