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Newark, Delaware, United States

Bais H.P.,University of Delaware | Bais H.P.,Delaware Biotechnology Institute
Plant and Soil | Year: 2012

Microbes use quorum sensing (QS) as a mechanism to regulate host colonization and virulence in the rhizosphere. Various Gram-positive and Gram-negative bacteria engage in quorum sensing as a mode of communication to inflict pathogenicity on hosts. Of late, the use of various microbial biocontrol agents to restrict pathogenic fungi and bacteria has gained some pace. Although, not much is known about direct antagonistic mechanisms adapted by various biocontrol agents on pathogens, it still represents a sustainable technique to control pathogenesis. Crépin et al. (2012) in this issue of Plant Soil address, for the first time, the question of regulating quorum sensing (QS) by quorum-quenching (QQ) techniques. Crépin et al. show that a rhizosphere bacteria Rhodococcus erythropolis catabolizes the N-acylhomoserine lactones (N-AHLs) produced by Pectobacterium atrosepticum, thus attenuating its virulence. Their experimental results strongly support the involvement of inter-bacterial communication in the rhizosphere. This knowledge is of crucial importance for putting into practice sustainable disease-protection strategies for biocontrol technologies. © 2012 Springer Science+Business Media B.V.

Luo T.,University of Delaware | Kiick K.L.,University of Delaware | Kiick K.L.,Delaware Biotechnology Institute
European Polymer Journal | Year: 2013

Collagen is the most abundant protein in mammals, and there has been long-standing interest in understanding and controlling collagen assembly in the design of new materials. Collagen-like peptides (CLPs), also known as collagen-mimetic peptides (CMPs) or collagen-related peptides (CRPs), have thus been widely used to elucidate collagen triple helix structure as well as to produce higher-order structures that mimic natural collagen fibers. This mini-review provides an overview of recent progress on these topics, in three broad topical areas. The first focuses on reported developments in deciphering the chemical basis for collagen triple helix stabilization, which we review not with the intent of describing the basic structure and biological function of collagen, but to summarize different pathways for designing collagen-like peptides with high thermostability. Various approaches for producing higher-order structures via CLP self-assembly, via various types of intermolecular interaction, are then discussed. Finally, recent developments in a new area, the production of polymer-CLP bioconjugates, are summarized. Biological applications of collagen contained hydrogels are also included in this section. The topics may serve as a guide for the design of collagen-like peptides and their bioconjugates for targeted application in the biomedical arena. © 2013 Elsevier Ltd. All rights reserved.

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
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.

Liang Y.,University of Delaware | Kiick K.L.,University of Delaware | Kiick K.L.,Delaware Biotechnology Institute
Polymer Chemistry | Year: 2014

Novel, multifunctional lipid-coated polymer nanogels crosslinked by photo-triggered Michael-type addition were prepared via the use of liposome templates. The photo-sensitive gelation and temporal control of the crosslinking reaction were confirmed by oscillatory rheology experiments of bulk hydrogels, and the production of nanogels was confirmed via dynamic light scattering and transmission electron microscopy. The surface functionality of the lipid-coated nanogels was demonstrated by surface modification with a reactive fluorescent dye. These multifunctional lipid-coated nanogels, given the mild preparation conditions, ease of size control, and versatility of the chemical linkages used as cross-links, have significant potential for use in polymeric nanoparticulate drug delivery systems. © 2014 The Royal Society of Chemistry.

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