Compared with single-network hydrogels, double-network hydrogels offer higher mechanical strength... more Compared with single-network hydrogels, double-network hydrogels offer higher mechanical strength and toughness. Integrating useful functions into double-network hydrogels can expand the portfolios of the hydrogels. We report the preparation of double-network metallopolymer hydrogels with remarkable hydration, antifouling, and antimicrobial properties. These cationic hydrogels are composed of a first network of cationic cobaltocenium polyelectrolytes and a second network of polyacrylamide, all prepared via radical polymerization. Antibiotics were further installed into the hydrogels via ion-complexation with metal cations. These hydrogels exhibited significantly enhanced hydration, compared with polyacrylamide-based hydrogels, while featuring robust mechanical strength. Cationic metallopolymer hydrogels exhibited strong antifouling against oppositely charged proteins. These antibiotic-loaded hydrogels demonstrated a synergistic effect on the inhibition of bacterial growth and antifouling of bacteria, as a result of the unique ion complexation of cobaltocenium cations.
New antimicrobial agents are needed to address ever-increasing antimicrobial resistance and a gro... more New antimicrobial agents are needed to address ever-increasing antimicrobial resistance and a growing epidemic of infections caused by multidrug resistant pathogens. We design nanostructured antimicrobial copolymers containing multicyclic natural products that bear facial amphiphilicity. Bile acid based macromolecular architectures of these nanostructures can interact preferentially with bacterial membranes. Incorporation of polyethylene glycol into the copolymers not only improved the colloidal stability of nanostructures but also increased the biocompatibility. This study investigated the effects of facial amphiphilicity, polymer architectures, and self-assembled nanostructures on antimicrobial activity. Advanced nanostructures such as spheres, vesicles, and rod-shaped aggregates are formed in water from the facial amphiphilic cationic copolymers via supramolecular interactions. These aggregates were particularly interactive toward Gram-positive and Gram-negative bacterial cell membranes and showed low hemolysis against mammalian cells.
Journal of Experimental Marine Biology and Ecology, Jul 1, 2005
Abiotic hydrolysis of simazine, atrazine, diazinon, methylparathion, and chlorpyrifos was studied... more Abiotic hydrolysis of simazine, atrazine, diazinon, methylparathion, and chlorpyrifos was studied in three different natural waters and buffered Milli-Q water. The triazines showed no detectable decrease in concentration in any of the waters over 43 days at pH 8.0 and 40°C. The rates of hydrolysis for diazinon and methylparathion were statistically similar in all waters tested. Chlorpyrifos exhibited a ∼32% decrease in hydrolysis rate in the presence of a high concentration of dissolved organic matter (DOM) (34.5 mg/L dissolved organic carbon). The activation energies are larger, and thus the predicted hydrolysis rates are significantly slower than those previously reported. The effect of continuous vigorous mixing on hydrolysis rates was investigated and found to have only a minor effect. The results suggest that uncatalyzed abiotic hydrolysis is very slow for these compounds at the temperatures and pH's typical of most natural waters and affirm the need for a greater understanding of the relative influence of DOM, catalysis, and biodegradation on the fate of organophosphate and triazine pesticides.
A new nanomaterial composed of polyvinylpyrrolidone coated iron oxide was successfully used to re... more A new nanomaterial composed of polyvinylpyrrolidone coated iron oxide was successfully used to remediate toxicity of oil-contaminated seawater.
Bacterial extracellular polymeric substances (EPS) have been recently found to contribute most fo... more Bacterial extracellular polymeric substances (EPS) have been recently found to contribute most for metal removal in nanoenhanced bioremediation. However, the mechanism by which NPs affect EPS-metal interactions is not fully known. Here, Halomonas sp. was employed to explore the role of EPS after in vivo exposure to Cd/Pb and polyvinylpyrrolidone (PVP) coated iron oxide nanoparticles (IONPs, 20 mg L-1) for 72 h. Cd-IONPs produced the highest concentrations of EPS proteins (136.3 mg L-1), while Cd induced the most production of polysaccharides (241.0 mg L-1). IONPs increased protein/polysaccharides ratio from 0.2 (Cd) to 1.2 (Cd-IONPs). The increased protein favors the formation of protein coronas on IONPs surface, which would promote Cd adsorption during NP-metal-EPS interaction. FTIR analysis indicated that the coexistence of Cd and IONPs interacted with proteins more strongly than with polysaccharides. Glycosyl monomer analyses suggested mannose and glucose as target sugars for EPS complexation with metals, and IONPs reduced metal-induced changes in monosaccharide profiles. Protein secondary structures changed in all treatments, but we could not distinguish stresses induced by metals from those by IONPs. These findings provide greater understanding of the role of EPS in NP-metal-EPS interaction, providing a better underpinning knowledge for the application of NP-enhanced bioremediation.
Microbial cells (i.e., bacteria, archaea, microeukaryotes) in oceans secrete a diverse array of l... more Microbial cells (i.e., bacteria, archaea, microeukaryotes) in oceans secrete a diverse array of large molecules, collectively called extracellular polymeric substances (EPSs) or simply exopolymers. These secretions facilitate attachment to surfaces that lead to the formation of structured 'biofilm' communities. In open-water environments, they also lead to formation of organic colloids, and larger aggregations of cells, called 'marine snow.' Secretion of EPS is now recognized as a fundamental microbial adaptation, occurring under many environmental conditions, and one that influences many ocean processes. This relatively recent realization has revolutionized our understanding of microbial impacts on ocean systems. EPS occur in a range of molecular sizes, conformations and physical/chemical properties, and polysaccharides, proteins, lipids, and even nucleic acids are actively secreted components. Interestingly, however, the physical ultrastructure of how individual EPS interact with each other is poorly understood. Together, the EPS matrix molecules form a three-dimensional architecture from which cells may localize extracellular activities and conduct cooperative/antagonistic interactions that cannot be accomplished efficiently by free-living cells. EPS alter optical signatures of sediments and seawater, and are involved in biogeomineral precipitation and the construction of microbial macrostructures, and horizontal-transfers of genetic information. In the water-column, they contribute to the formation of marine snow, transparent exopolymer particles (TEPs), sea-surface microlayer biofilm, and marine oil snow. Excessive production of EPS occurs during later-stages of phytoplankton blooms as an excess metabolic by product and releases a carbon pool that transitions among dissolved-, colloidal-, and gel-states. Some EPS are highly labile carbon forms, while other forms appear quite refractory to degradation. Emerging studies suggest that EPS contribute to efficient trophic-transfer of environmental contaminants, and may provide a protective refugia for pathogenic cells within marine systems; one that enhances their survival/persistence. Finally, these secretions are prominent in 'extreme' environments ranging from sea-ice communities to hypersaline systems to the high-temperatures/pressures of hydrothermal-vent systems. This overview summarizes some of the roles of exopolymer in oceans.
Abstract—Ecotoxicology research is using many methods for engineered nanomaterials (ENMs), but th... more Abstract—Ecotoxicology research is using many methods for engineered nanomaterials (ENMs), but the collective experience from researchers has not been documented. This paper reports the practical issues for working with ENMs and suggests nano-specific modifications to protocols. The review considers generic practical issues, as well as specific issues for aquatic tests, marine grazers, soil organisms, and bioaccumulation studies. Current procedures for cleaning glassware are adequate, but electrodes are problematic. The maintenance of exposure concentration is challenging, but can be achieved with some ENMs. The need to characterize the media during experiments is identified, but rapid analytical methods are not available to do this. The use of sonication and natural/synthetic dispersants are discussed. Nano-specific biological endpoints may be developed for a tiered monitoring scheme to diagnose ENM exposure or effect. A case study of the algal growth test highlights many small deviations in current regulatory test protocols that are allowed (shaking,
... Accumulating evidence, however, suggests that they influence a wide range of marine processes... more ... Accumulating evidence, however, suggests that they influence a wide range of marine processes such as aggregate formation in the water column, benthic larval settlement, microscale biogeochemical processes, sediment stability, and metal sequestering by hydrothermal vent ...
Climate‐induced stressors, such as changes in temperature, salinity, and pH, contribute to the em... more Climate‐induced stressors, such as changes in temperature, salinity, and pH, contribute to the emergence of infectious diseases. These changes alter geographical constraint, resulting in increased Vibrio spread, exposure, and infection rates, thus facilitating greater Vibrio‐human interactions. Multiple efforts have been developed to predict Vibrio exposure and raise awareness of health risks, but most models only use temperature and salinity as prediction factors. This study aimed to better understand the potential effects of temperature and pH on V. vulnificus and V. parahaemolyticus planktonic and biofilm growth. Vibrio strains were grown in triplicate at 25°, 30°, and 37°C in 96 well plates containing Modified Seawater Yeast Extract modified with CaCl2 at pH's ranging from 5 to 9.6. AMiGA software was used to model growth curves using Gaussian process regression. The effects of temperature and pH were evaluated using randomized complete block analysis of variance, and the growth rates of V. parahaemolyticus and V. vulnificus were modeled using the interpolation fit on the MatLab Curve Fitting Toolbox. Different optimal conditions involving temperature and pH were observed for planktonic and biofilm Vibrio growth within‐ and between‐species. This study showed that temperature and pH factors significantly affect Vibrio planktonic growth rates and V. parahaemolyticus biofilm formation. Therefore, pH effects must be added to the Vibrio growth modeling efforts to better predict Vibrio risk in estuarine and coastal zones that can potentially experience the cooccurrence of Vibrio and harmful algal bloom outbreak events.
Benthic harpacticoid copepods represent a predonderate link in the estuarlne food web. In the upp... more Benthic harpacticoid copepods represent a predonderate link in the estuarlne food web. In the upper food web they seve as food for many inver tebrates and fish fry. In the lower portion of the web, it has been suggested that they feed to a large extent on the microbial flora and are therefore important in the recycling .of benthic energy. While their relationships with microbes have been the subject of much literature, information regarding the actual food resources of harpacticoids. is limited. Most of these studies are strictly laboratory investigations, using food material which is either easily culturable or easily accessible but not necessarily representative of the animals’ natural habitat. In small drainage channels of Great Sippewisset Marsh there occurs definite zonation of photosynthetic miCrobial flora. The relationships V certain harpacticoid copepod species with these photosynthetic microbes V
Chronic multisymptom illness (CMI) affects a subsection of elderly and war Veterans and is associ... more Chronic multisymptom illness (CMI) affects a subsection of elderly and war Veterans and is associated with systemic inflammation. Here, using a mouse model of CMI and a group of Gulf War (GW) Veterans’ with CMI we show the presence of an altered host resistome. Results show that antibiotic resistance genes (ARGs) are significantly altered in the CMI group in both mice and GW Veterans when compared to control. Fecal samples from GW Veterans with persistent CMI show a significant increase of resistance to a wide class of antibiotics and exhibited an array of mobile genetic elements (MGEs) distinct from normal healthy controls. The altered resistome and gene signature is correlated with mouse serum IL-6 levels. Altered resistome in mice also is correlated strongly with intestinal inflammation, decreased synaptic plasticity, reversible with fecal microbiota transplant (FMT). The results reported might help in understanding the risks to treating hospital acquired infections in this popul...
Bacterial extracellular polymeric substances (EPS) have been recently found to contribute most fo... more Bacterial extracellular polymeric substances (EPS) have been recently found to contribute most for metal removal in nanoenhanced bioremediation. However, the mechanism by which NPs affect EPS-metal interactions is not fully known. Here, Halomonas sp. was employed to explore the role of EPS after in vivo exposure to Cd/Pb and polyvinylpyrrolidone (PVP) coated iron oxide nanoparticles (IONPs, 20 mg L-1) for 72 h. Cd-IONPs produced the highest concentrations of EPS proteins (136.3 mg L-1), while Cd induced the most production of polysaccharides (241.0 mg L-1). IONPs increased protein/polysaccharides ratio from 0.2 (Cd) to 1.2 (Cd-IONPs). The increased protein favors the formation of protein coronas on IONPs surface, which would promote Cd adsorption during NP-metal-EPS interaction. FTIR analysis indicated that the coexistence of Cd and IONPs interacted with proteins more strongly than with polysaccharides. Glycosyl monomer analyses suggested mannose and glucose as target sugars for EPS complexation with metals, and IONPs reduced metal-induced changes in monosaccharide profiles. Protein secondary structures changed in all treatments, but we could not distinguish stresses induced by metals from those by IONPs. These findings provide greater understanding of the role of EPS in NP-metal-EPS interaction, providing a better underpinning knowledge for the application of NP-enhanced bioremediation.
Compared with single-network hydrogels, double-network hydrogels offer higher mechanical strength... more Compared with single-network hydrogels, double-network hydrogels offer higher mechanical strength and toughness. Integrating useful functions into double-network hydrogels can expand the portfolios of the hydrogels. We report the preparation of double-network metallopolymer hydrogels with remarkable hydration, antifouling, and antimicrobial properties. These cationic hydrogels are composed of a first network of cationic cobaltocenium polyelectrolytes and a second network of polyacrylamide, all prepared via radical polymerization. Antibiotics were further installed into the hydrogels via ion-complexation with metal cations. These hydrogels exhibited significantly enhanced hydration, compared with polyacrylamide-based hydrogels, while featuring robust mechanical strength. Cationic metallopolymer hydrogels exhibited strong antifouling against oppositely charged proteins. These antibiotic-loaded hydrogels demonstrated a synergistic effect on the inhibition of bacterial growth and antifouling of bacteria, as a result of the unique ion complexation of cobaltocenium cations.
New antimicrobial agents are needed to address ever-increasing antimicrobial resistance and a gro... more New antimicrobial agents are needed to address ever-increasing antimicrobial resistance and a growing epidemic of infections caused by multidrug resistant pathogens. We design nanostructured antimicrobial copolymers containing multicyclic natural products that bear facial amphiphilicity. Bile acid based macromolecular architectures of these nanostructures can interact preferentially with bacterial membranes. Incorporation of polyethylene glycol into the copolymers not only improved the colloidal stability of nanostructures but also increased the biocompatibility. This study investigated the effects of facial amphiphilicity, polymer architectures, and self-assembled nanostructures on antimicrobial activity. Advanced nanostructures such as spheres, vesicles, and rod-shaped aggregates are formed in water from the facial amphiphilic cationic copolymers via supramolecular interactions. These aggregates were particularly interactive toward Gram-positive and Gram-negative bacterial cell membranes and showed low hemolysis against mammalian cells.
Journal of Experimental Marine Biology and Ecology, Jul 1, 2005
Abiotic hydrolysis of simazine, atrazine, diazinon, methylparathion, and chlorpyrifos was studied... more Abiotic hydrolysis of simazine, atrazine, diazinon, methylparathion, and chlorpyrifos was studied in three different natural waters and buffered Milli-Q water. The triazines showed no detectable decrease in concentration in any of the waters over 43 days at pH 8.0 and 40°C. The rates of hydrolysis for diazinon and methylparathion were statistically similar in all waters tested. Chlorpyrifos exhibited a ∼32% decrease in hydrolysis rate in the presence of a high concentration of dissolved organic matter (DOM) (34.5 mg/L dissolved organic carbon). The activation energies are larger, and thus the predicted hydrolysis rates are significantly slower than those previously reported. The effect of continuous vigorous mixing on hydrolysis rates was investigated and found to have only a minor effect. The results suggest that uncatalyzed abiotic hydrolysis is very slow for these compounds at the temperatures and pH's typical of most natural waters and affirm the need for a greater understanding of the relative influence of DOM, catalysis, and biodegradation on the fate of organophosphate and triazine pesticides.
A new nanomaterial composed of polyvinylpyrrolidone coated iron oxide was successfully used to re... more A new nanomaterial composed of polyvinylpyrrolidone coated iron oxide was successfully used to remediate toxicity of oil-contaminated seawater.
Bacterial extracellular polymeric substances (EPS) have been recently found to contribute most fo... more Bacterial extracellular polymeric substances (EPS) have been recently found to contribute most for metal removal in nanoenhanced bioremediation. However, the mechanism by which NPs affect EPS-metal interactions is not fully known. Here, Halomonas sp. was employed to explore the role of EPS after in vivo exposure to Cd/Pb and polyvinylpyrrolidone (PVP) coated iron oxide nanoparticles (IONPs, 20 mg L-1) for 72 h. Cd-IONPs produced the highest concentrations of EPS proteins (136.3 mg L-1), while Cd induced the most production of polysaccharides (241.0 mg L-1). IONPs increased protein/polysaccharides ratio from 0.2 (Cd) to 1.2 (Cd-IONPs). The increased protein favors the formation of protein coronas on IONPs surface, which would promote Cd adsorption during NP-metal-EPS interaction. FTIR analysis indicated that the coexistence of Cd and IONPs interacted with proteins more strongly than with polysaccharides. Glycosyl monomer analyses suggested mannose and glucose as target sugars for EPS complexation with metals, and IONPs reduced metal-induced changes in monosaccharide profiles. Protein secondary structures changed in all treatments, but we could not distinguish stresses induced by metals from those by IONPs. These findings provide greater understanding of the role of EPS in NP-metal-EPS interaction, providing a better underpinning knowledge for the application of NP-enhanced bioremediation.
Microbial cells (i.e., bacteria, archaea, microeukaryotes) in oceans secrete a diverse array of l... more Microbial cells (i.e., bacteria, archaea, microeukaryotes) in oceans secrete a diverse array of large molecules, collectively called extracellular polymeric substances (EPSs) or simply exopolymers. These secretions facilitate attachment to surfaces that lead to the formation of structured 'biofilm' communities. In open-water environments, they also lead to formation of organic colloids, and larger aggregations of cells, called 'marine snow.' Secretion of EPS is now recognized as a fundamental microbial adaptation, occurring under many environmental conditions, and one that influences many ocean processes. This relatively recent realization has revolutionized our understanding of microbial impacts on ocean systems. EPS occur in a range of molecular sizes, conformations and physical/chemical properties, and polysaccharides, proteins, lipids, and even nucleic acids are actively secreted components. Interestingly, however, the physical ultrastructure of how individual EPS interact with each other is poorly understood. Together, the EPS matrix molecules form a three-dimensional architecture from which cells may localize extracellular activities and conduct cooperative/antagonistic interactions that cannot be accomplished efficiently by free-living cells. EPS alter optical signatures of sediments and seawater, and are involved in biogeomineral precipitation and the construction of microbial macrostructures, and horizontal-transfers of genetic information. In the water-column, they contribute to the formation of marine snow, transparent exopolymer particles (TEPs), sea-surface microlayer biofilm, and marine oil snow. Excessive production of EPS occurs during later-stages of phytoplankton blooms as an excess metabolic by product and releases a carbon pool that transitions among dissolved-, colloidal-, and gel-states. Some EPS are highly labile carbon forms, while other forms appear quite refractory to degradation. Emerging studies suggest that EPS contribute to efficient trophic-transfer of environmental contaminants, and may provide a protective refugia for pathogenic cells within marine systems; one that enhances their survival/persistence. Finally, these secretions are prominent in 'extreme' environments ranging from sea-ice communities to hypersaline systems to the high-temperatures/pressures of hydrothermal-vent systems. This overview summarizes some of the roles of exopolymer in oceans.
Abstract—Ecotoxicology research is using many methods for engineered nanomaterials (ENMs), but th... more Abstract—Ecotoxicology research is using many methods for engineered nanomaterials (ENMs), but the collective experience from researchers has not been documented. This paper reports the practical issues for working with ENMs and suggests nano-specific modifications to protocols. The review considers generic practical issues, as well as specific issues for aquatic tests, marine grazers, soil organisms, and bioaccumulation studies. Current procedures for cleaning glassware are adequate, but electrodes are problematic. The maintenance of exposure concentration is challenging, but can be achieved with some ENMs. The need to characterize the media during experiments is identified, but rapid analytical methods are not available to do this. The use of sonication and natural/synthetic dispersants are discussed. Nano-specific biological endpoints may be developed for a tiered monitoring scheme to diagnose ENM exposure or effect. A case study of the algal growth test highlights many small deviations in current regulatory test protocols that are allowed (shaking,
... Accumulating evidence, however, suggests that they influence a wide range of marine processes... more ... Accumulating evidence, however, suggests that they influence a wide range of marine processes such as aggregate formation in the water column, benthic larval settlement, microscale biogeochemical processes, sediment stability, and metal sequestering by hydrothermal vent ...
Climate‐induced stressors, such as changes in temperature, salinity, and pH, contribute to the em... more Climate‐induced stressors, such as changes in temperature, salinity, and pH, contribute to the emergence of infectious diseases. These changes alter geographical constraint, resulting in increased Vibrio spread, exposure, and infection rates, thus facilitating greater Vibrio‐human interactions. Multiple efforts have been developed to predict Vibrio exposure and raise awareness of health risks, but most models only use temperature and salinity as prediction factors. This study aimed to better understand the potential effects of temperature and pH on V. vulnificus and V. parahaemolyticus planktonic and biofilm growth. Vibrio strains were grown in triplicate at 25°, 30°, and 37°C in 96 well plates containing Modified Seawater Yeast Extract modified with CaCl2 at pH's ranging from 5 to 9.6. AMiGA software was used to model growth curves using Gaussian process regression. The effects of temperature and pH were evaluated using randomized complete block analysis of variance, and the growth rates of V. parahaemolyticus and V. vulnificus were modeled using the interpolation fit on the MatLab Curve Fitting Toolbox. Different optimal conditions involving temperature and pH were observed for planktonic and biofilm Vibrio growth within‐ and between‐species. This study showed that temperature and pH factors significantly affect Vibrio planktonic growth rates and V. parahaemolyticus biofilm formation. Therefore, pH effects must be added to the Vibrio growth modeling efforts to better predict Vibrio risk in estuarine and coastal zones that can potentially experience the cooccurrence of Vibrio and harmful algal bloom outbreak events.
Benthic harpacticoid copepods represent a predonderate link in the estuarlne food web. In the upp... more Benthic harpacticoid copepods represent a predonderate link in the estuarlne food web. In the upper food web they seve as food for many inver tebrates and fish fry. In the lower portion of the web, it has been suggested that they feed to a large extent on the microbial flora and are therefore important in the recycling .of benthic energy. While their relationships with microbes have been the subject of much literature, information regarding the actual food resources of harpacticoids. is limited. Most of these studies are strictly laboratory investigations, using food material which is either easily culturable or easily accessible but not necessarily representative of the animals’ natural habitat. In small drainage channels of Great Sippewisset Marsh there occurs definite zonation of photosynthetic miCrobial flora. The relationships V certain harpacticoid copepod species with these photosynthetic microbes V
Chronic multisymptom illness (CMI) affects a subsection of elderly and war Veterans and is associ... more Chronic multisymptom illness (CMI) affects a subsection of elderly and war Veterans and is associated with systemic inflammation. Here, using a mouse model of CMI and a group of Gulf War (GW) Veterans’ with CMI we show the presence of an altered host resistome. Results show that antibiotic resistance genes (ARGs) are significantly altered in the CMI group in both mice and GW Veterans when compared to control. Fecal samples from GW Veterans with persistent CMI show a significant increase of resistance to a wide class of antibiotics and exhibited an array of mobile genetic elements (MGEs) distinct from normal healthy controls. The altered resistome and gene signature is correlated with mouse serum IL-6 levels. Altered resistome in mice also is correlated strongly with intestinal inflammation, decreased synaptic plasticity, reversible with fecal microbiota transplant (FMT). The results reported might help in understanding the risks to treating hospital acquired infections in this popul...
Bacterial extracellular polymeric substances (EPS) have been recently found to contribute most fo... more Bacterial extracellular polymeric substances (EPS) have been recently found to contribute most for metal removal in nanoenhanced bioremediation. However, the mechanism by which NPs affect EPS-metal interactions is not fully known. Here, Halomonas sp. was employed to explore the role of EPS after in vivo exposure to Cd/Pb and polyvinylpyrrolidone (PVP) coated iron oxide nanoparticles (IONPs, 20 mg L-1) for 72 h. Cd-IONPs produced the highest concentrations of EPS proteins (136.3 mg L-1), while Cd induced the most production of polysaccharides (241.0 mg L-1). IONPs increased protein/polysaccharides ratio from 0.2 (Cd) to 1.2 (Cd-IONPs). The increased protein favors the formation of protein coronas on IONPs surface, which would promote Cd adsorption during NP-metal-EPS interaction. FTIR analysis indicated that the coexistence of Cd and IONPs interacted with proteins more strongly than with polysaccharides. Glycosyl monomer analyses suggested mannose and glucose as target sugars for EPS complexation with metals, and IONPs reduced metal-induced changes in monosaccharide profiles. Protein secondary structures changed in all treatments, but we could not distinguish stresses induced by metals from those by IONPs. These findings provide greater understanding of the role of EPS in NP-metal-EPS interaction, providing a better underpinning knowledge for the application of NP-enhanced bioremediation.
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Papers by Alan W Decho