The Experts below are selected from a list of 270 Experts worldwide ranked by ideXlab platform
Peter Setlow - One of the best experts on this subject based on the ideXlab platform.
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Sensitization of Bacillus subtilis spores to dry heat and desiccation by pretreatment with Oxidizing Agents.
Letters in applied microbiology, 2008Co-Authors: A. De Benito Armas, Barbara Setlow, N.l. Padula, Peter SetlowAbstract:Aims: To determine if pretreatment with Oxidizing Agents sensitizes Bacillus subtilis spores to dry heat or desiccation. Methods: Bacillus subtilis spores were killed approx. 90% by Oxidizing Agents, and the sensitivity of treated and untreated spores to dry heat and desiccation was determined. The effects of pyruvate on spore recovery after Oxidizing agent pretreatment and then dry heat or desiccation were also determined. Conclusions: Spores pretreated with Oxone™ or hypochlorite were not sensitized to dry heat or freeze-drying. However, hydrogen peroxide or t-butylhydroperoxide pretreatment sensitized spores to dry heat or desiccation, and the desiccation caused mutagenesis in the survivors. Pyruvate increased recovery of spores treated with hydrogen peroxide alone or plus dry heat or desiccation, and with t-butylhydroperoxide and desiccation, but not with t-butylhydroperoxide alone or plus dry heat. Significance and Impact of the Study: Pretreatment with peroxides sensitizes bacterial spores to subsequent stress. This finding may suggest improved regimens for spore inactivation.
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Treatment with Oxidizing Agents damages the inner membrane of spores of Bacillus subtilis and sensitizes spores to subsequent stress
Journal of applied microbiology, 2004Co-Authors: D.e. Cortezzo, Kasia Koziol-dube, Barbara Setlow, Peter SetlowAbstract:Aims: To determine if treatment of Bacillus subtilis spores with a variety of Oxidizing Agents causes damage to the spore's inner membrane. Methods and Results: Spores of B. subtilis were killed 80–99% with wet heat or a variety of Oxidizing Agents, including betadine, chlorine dioxide, cumene hydroperoxide, hydrogen peroxide, OxoneTM, ozone, sodium hypochlorite and t-butylhydroperoxide, and the Agents neutralized and/or removed. Survivors of spores pretreated with Oxidizing Agents exhibited increased sensitivity to killing by a normally minimal lethal heat treatment, while spores pretreated with wet heat did not. In addition, spores treated with wet heat or the Oxidizing Agents, except sodium hypochlorite, were more sensitive to high NaCl in plating media than were untreated spores. The core region of spores treated with at least two Oxidizing Agents was also penetrated much more readily by methylamine than was the core of untreated spores, and spores treated with Oxidizing Agents but not wet heat germinated faster with dodecylamine than did untreated spores. Spores of strains with very different levels of unsaturated fatty acids in their inner membrane exhibited essentially identical resistance to Oxidizing Agents. Conclusions: Treatment of spores with Oxidizing Agents has been suggested to cause damage to the spore's inner membrane, a membrane whose integrity is essential for spore viability. The sensitization of spores to killing by heat and to high salt after pretreatment with Oxidizing Agents is consistent with and supports this suggestion. Presumably mild pretreatment with Oxidizing Agents causes some damage to the spore's inner membrane. While this damage may not be lethal under normal conditions, the damaged inner membrane may be less able to maintain its integrity, when dormant spores are exposed to high temperature or when germinated spores are faced with osmotic stress. Triggering of spore germination by dodecylamine likely involves action by this agent on the spore's inner membrane allowing release of the spore core's depot of dipicolinic acid. Presumably dodecylamine more readily alters the permeability of a damaged inner membrane and thus more readily triggers germination of spores pretreated with Oxidizing Agents. Damage to the inner spore membrane by Oxidizing Agents is also consistent with the more rapid penetration of methylamine into the core of treated spores, as the inner membrane is likely the crucial permeability barrier to methylamine entry into the spore core. As spores of strains with very different levels of unsaturated fatty acids in their inner membrane exhibited essentially identical resistance to Oxidizing Agents, it is not through oxidation of unsaturated fatty acids that Oxidizing Agents kill and/or damage spores. Perhaps these Agents work by causing oxidative damage to key proteins in the spore's inner membrane. Significance and Impact of the Study: The more rapid heat killing and germination with dodecylamine, the greater permeability of the spore core and the osmotic stress sensitivity in outgrowth of spores pretreated with Oxidizing Agents is consistent with such Agents causing damage to the spore's inner membrane, even if this damage is not lethal under normal conditions. It may be possible to take advantage of this phenomenon to devise improved, less costly regimens for spore inactivation.
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alkyl hydroperoxide reductase catalase mrga and superoxide dismutase are not involved in resistance of bacillus subtilis spores to heat or Oxidizing Agents
Journal of Bacteriology, 1997Co-Authors: Lilliam Casillasmartinez, Peter SetlowAbstract:Only a single superoxide dismutase (SodA) was detected in Bacillus subtilis, and growing cells of a sodA mutant exhibited paraquat sensitivity as well as a growth defect and reduced survival at an elevated temperature. However, the sodA mutation had no effect on the heat or hydrogen peroxide resistance of wild-type spores or spores lacking the two major DNA protective alpha/beta-type small, acid-soluble, spore proteins (termed alpha(-)beta(-) spores). Spores also had only a single catalase (KatX), as the two catalases found in growing cells (KatA and KatB) were absent. While a katA mutation greatly decreased the hydrogen peroxide resistance of growing cells, as found previously, katA, katB, and katX mutations had no effect on the heat or hydrogen peroxide resistance of wild-type or alpha(-)beta(-) spores. Inactivation of the mrgA gene, which codes for a DNA-binding protein that can protect growing cells against hydrogen peroxide, also had no effect on spore hydrogen peroxide resistance. Inactivation of genes coding for alkyl hydroperoxide reductase, which has been shown to decrease growing cell resistance to alkyl hydroperoxides, had no effect on spore resistance to such compounds or on spore resistance to heat and hydrogen peroxide. However, Western blot analysis showed that at least one alkyl hydroperoxide reductase subunit was present in spores. Together these results indicate that proteins that play a role in the resistance of growing cells to Oxidizing Agents play no role in spore resistance. A likely reason for this lack of a protective role for spore enzymes is the inactivity of enzymes within the dormant spore.
Duangkamon Sakloetsakun - One of the best experts on this subject based on the ideXlab platform.
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in situ gelling properties of chitosan thioglycolic acid conjugate in the presence of Oxidizing Agents
Biomaterials, 2009Co-Authors: Duangkamon Sakloetsakun, Juliane Hombach, Andreas BernkopschnurchAbstract:The rheological behaviour of chitosan-thioglycolic acid conjugate (chitosan-TGA) in the presence of four Oxidizing Agents was investigated. Chitosan-TGA was synthesized via amide bond formation between the primary amino group of chitosan and the carboxylic acid group of thioglycolic acid. The sol–gel phase transition of the polymer was determined by rheological measurements. Moreover, cytotoxicity of the gel in combination with each Oxidizing agent was evaluated utilizing LDH and MTT assay. The modified chitosan displayed 1053 ± 44 μmol/g thiol groups. Results of rheological studies showed that 1% (m/v) chitosan-TGA without any Oxidizing Agents became gel within 40 min. In contrast, when the Oxidizing Agents hydrogen peroxide, sodium periodate, ammonium persulfate and sodium hypochlorite were added, respectively, gelation took place within a few minutes. Within 20 min, hydrogen peroxide having been added in a final concentration of 25.2 nmol/L increased dynamic viscosity of 1% (m/v) chitosan-TGA up to 16,500-fold. This can be explained by the formation of inter- and/or intramolecular disulfide bonds which were indirectly verified via the decrease in thiol groups. Additionally, evidence of an increase in cross-linking of thiolated chitosan as a function of time was provided by frequency sweep measurements. Furthermore, viability of Caco-2 cells having been incubated with chitosan-TGA/Oxidizing agent systems assessed by MTT assay was 70–85% and the percentage of LDH release was only in case of the chitosan-TGA/ammonium persulfate system significantly (p < 0.05) raising compared to the negative control. According to these results, chitosan-TGA/Oxidizing agent combinations might be a promising novel in situ gelling system for various pharmaceutical applications such as a controlled drug release carrier or for tissue engineering.
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In situ gelling properties of chitosan-thioglycolic acid conjugate in the presence of Oxidizing Agents.
Biomaterials, 2009Co-Authors: Duangkamon Sakloetsakun, Juliane Hombach, Andreas Bernkop-schnürchAbstract:The rheological behaviour of chitosan-thioglycolic acid conjugate (chitosan-TGA) in the presence of four Oxidizing Agents was investigated. Chitosan-TGA was synthesized via amide bond formation between the primary amino group of chitosan and the carboxylic acid group of thioglycolic acid. The sol–gel phase transition of the polymer was determined by rheological measurements. Moreover, cytotoxicity of the gel in combination with each Oxidizing agent was evaluated utilizing LDH and MTT assay. The modified chitosan displayed 1053 ± 44 μmol/g thiol groups. Results of rheological studies showed that 1% (m/v) chitosan-TGA without any Oxidizing Agents became gel within 40 min. In contrast, when the Oxidizing Agents hydrogen peroxide, sodium periodate, ammonium persulfate and sodium hypochlorite were added, respectively, gelation took place within a few minutes. Within 20 min, hydrogen peroxide having been added in a final concentration of 25.2 nmol/L increased dynamic viscosity of 1% (m/v) chitosan-TGA up to 16,500-fold. This can be explained by the formation of inter- and/or intramolecular disulfide bonds which were indirectly verified via the decrease in thiol groups. Additionally, evidence of an increase in cross-linking of thiolated chitosan as a function of time was provided by frequency sweep measurements. Furthermore, viability of Caco-2 cells having been incubated with chitosan-TGA/Oxidizing agent systems assessed by MTT assay was 70–85% and the percentage of LDH release was only in case of the chitosan-TGA/ammonium persulfate system significantly (p
Andreas Bernkopschnurch - One of the best experts on this subject based on the ideXlab platform.
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in situ gelling properties of chitosan thioglycolic acid conjugate in the presence of Oxidizing Agents
Biomaterials, 2009Co-Authors: Duangkamon Sakloetsakun, Juliane Hombach, Andreas BernkopschnurchAbstract:The rheological behaviour of chitosan-thioglycolic acid conjugate (chitosan-TGA) in the presence of four Oxidizing Agents was investigated. Chitosan-TGA was synthesized via amide bond formation between the primary amino group of chitosan and the carboxylic acid group of thioglycolic acid. The sol–gel phase transition of the polymer was determined by rheological measurements. Moreover, cytotoxicity of the gel in combination with each Oxidizing agent was evaluated utilizing LDH and MTT assay. The modified chitosan displayed 1053 ± 44 μmol/g thiol groups. Results of rheological studies showed that 1% (m/v) chitosan-TGA without any Oxidizing Agents became gel within 40 min. In contrast, when the Oxidizing Agents hydrogen peroxide, sodium periodate, ammonium persulfate and sodium hypochlorite were added, respectively, gelation took place within a few minutes. Within 20 min, hydrogen peroxide having been added in a final concentration of 25.2 nmol/L increased dynamic viscosity of 1% (m/v) chitosan-TGA up to 16,500-fold. This can be explained by the formation of inter- and/or intramolecular disulfide bonds which were indirectly verified via the decrease in thiol groups. Additionally, evidence of an increase in cross-linking of thiolated chitosan as a function of time was provided by frequency sweep measurements. Furthermore, viability of Caco-2 cells having been incubated with chitosan-TGA/Oxidizing agent systems assessed by MTT assay was 70–85% and the percentage of LDH release was only in case of the chitosan-TGA/ammonium persulfate system significantly (p < 0.05) raising compared to the negative control. According to these results, chitosan-TGA/Oxidizing agent combinations might be a promising novel in situ gelling system for various pharmaceutical applications such as a controlled drug release carrier or for tissue engineering.
Andreas Bernkop-schnürch - One of the best experts on this subject based on the ideXlab platform.
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In situ gelling properties of chitosan-thioglycolic acid conjugate in the presence of Oxidizing Agents.
Biomaterials, 2009Co-Authors: Duangkamon Sakloetsakun, Juliane Hombach, Andreas Bernkop-schnürchAbstract:The rheological behaviour of chitosan-thioglycolic acid conjugate (chitosan-TGA) in the presence of four Oxidizing Agents was investigated. Chitosan-TGA was synthesized via amide bond formation between the primary amino group of chitosan and the carboxylic acid group of thioglycolic acid. The sol–gel phase transition of the polymer was determined by rheological measurements. Moreover, cytotoxicity of the gel in combination with each Oxidizing agent was evaluated utilizing LDH and MTT assay. The modified chitosan displayed 1053 ± 44 μmol/g thiol groups. Results of rheological studies showed that 1% (m/v) chitosan-TGA without any Oxidizing Agents became gel within 40 min. In contrast, when the Oxidizing Agents hydrogen peroxide, sodium periodate, ammonium persulfate and sodium hypochlorite were added, respectively, gelation took place within a few minutes. Within 20 min, hydrogen peroxide having been added in a final concentration of 25.2 nmol/L increased dynamic viscosity of 1% (m/v) chitosan-TGA up to 16,500-fold. This can be explained by the formation of inter- and/or intramolecular disulfide bonds which were indirectly verified via the decrease in thiol groups. Additionally, evidence of an increase in cross-linking of thiolated chitosan as a function of time was provided by frequency sweep measurements. Furthermore, viability of Caco-2 cells having been incubated with chitosan-TGA/Oxidizing agent systems assessed by MTT assay was 70–85% and the percentage of LDH release was only in case of the chitosan-TGA/ammonium persulfate system significantly (p
Juliane Hombach - One of the best experts on this subject based on the ideXlab platform.
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in situ gelling properties of chitosan thioglycolic acid conjugate in the presence of Oxidizing Agents
Biomaterials, 2009Co-Authors: Duangkamon Sakloetsakun, Juliane Hombach, Andreas BernkopschnurchAbstract:The rheological behaviour of chitosan-thioglycolic acid conjugate (chitosan-TGA) in the presence of four Oxidizing Agents was investigated. Chitosan-TGA was synthesized via amide bond formation between the primary amino group of chitosan and the carboxylic acid group of thioglycolic acid. The sol–gel phase transition of the polymer was determined by rheological measurements. Moreover, cytotoxicity of the gel in combination with each Oxidizing agent was evaluated utilizing LDH and MTT assay. The modified chitosan displayed 1053 ± 44 μmol/g thiol groups. Results of rheological studies showed that 1% (m/v) chitosan-TGA without any Oxidizing Agents became gel within 40 min. In contrast, when the Oxidizing Agents hydrogen peroxide, sodium periodate, ammonium persulfate and sodium hypochlorite were added, respectively, gelation took place within a few minutes. Within 20 min, hydrogen peroxide having been added in a final concentration of 25.2 nmol/L increased dynamic viscosity of 1% (m/v) chitosan-TGA up to 16,500-fold. This can be explained by the formation of inter- and/or intramolecular disulfide bonds which were indirectly verified via the decrease in thiol groups. Additionally, evidence of an increase in cross-linking of thiolated chitosan as a function of time was provided by frequency sweep measurements. Furthermore, viability of Caco-2 cells having been incubated with chitosan-TGA/Oxidizing agent systems assessed by MTT assay was 70–85% and the percentage of LDH release was only in case of the chitosan-TGA/ammonium persulfate system significantly (p < 0.05) raising compared to the negative control. According to these results, chitosan-TGA/Oxidizing agent combinations might be a promising novel in situ gelling system for various pharmaceutical applications such as a controlled drug release carrier or for tissue engineering.
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In situ gelling properties of chitosan-thioglycolic acid conjugate in the presence of Oxidizing Agents.
Biomaterials, 2009Co-Authors: Duangkamon Sakloetsakun, Juliane Hombach, Andreas Bernkop-schnürchAbstract:The rheological behaviour of chitosan-thioglycolic acid conjugate (chitosan-TGA) in the presence of four Oxidizing Agents was investigated. Chitosan-TGA was synthesized via amide bond formation between the primary amino group of chitosan and the carboxylic acid group of thioglycolic acid. The sol–gel phase transition of the polymer was determined by rheological measurements. Moreover, cytotoxicity of the gel in combination with each Oxidizing agent was evaluated utilizing LDH and MTT assay. The modified chitosan displayed 1053 ± 44 μmol/g thiol groups. Results of rheological studies showed that 1% (m/v) chitosan-TGA without any Oxidizing Agents became gel within 40 min. In contrast, when the Oxidizing Agents hydrogen peroxide, sodium periodate, ammonium persulfate and sodium hypochlorite were added, respectively, gelation took place within a few minutes. Within 20 min, hydrogen peroxide having been added in a final concentration of 25.2 nmol/L increased dynamic viscosity of 1% (m/v) chitosan-TGA up to 16,500-fold. This can be explained by the formation of inter- and/or intramolecular disulfide bonds which were indirectly verified via the decrease in thiol groups. Additionally, evidence of an increase in cross-linking of thiolated chitosan as a function of time was provided by frequency sweep measurements. Furthermore, viability of Caco-2 cells having been incubated with chitosan-TGA/Oxidizing agent systems assessed by MTT assay was 70–85% and the percentage of LDH release was only in case of the chitosan-TGA/ammonium persulfate system significantly (p
