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T R Webb - One of the best experts on this subject based on the ideXlab platform.
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Mechanistic In Vivo and In Vitro Pulmonary Cellular Studies Demonstrating Biodegradability of Inhaled p-Aramid RFP
The Annals of Occupational Hygiene, 2002Co-Authors: D B Warheit, M A Hartsky, Kenneth L. Reed, T R WebbAbstract:These studies were designed to investigate mechanisms through which inhaled p-Aramid respirable-sized fiber-shaped particulates (RFP) are biodegraded in the lungs of exposed rats and hamsters. We have postulated that lung fluids coat/activate inhaled p-Aramid RFP which deposit in the lung and promote enzymatic attack and consequent shortening. Aliquots of p-Aramid or cellulose (biopersistent control) RFP were instilled into the lungs of rats and the lungs digested 24 h later using two different (KOH or enzymatic) digestion methods. For in vitro studies the two RFP types were incubated with lavage fluid and processed via simulated digestion; in addition, rat lung epithelial cells, macrophages or co-cultures were incubated with p-Aramid and digested 1, 24 or 168 h post-exposure. In vivo the enzyme but not the KOH digestion method resulted in shortening of p-Aramid but not cellulose RFP recovered from rat lungs. The results of in vitro studies showed that mean lengths of p-Aramid RFP incubated with saline and processed by either digestion method were not found to be altered. Indeed, only the preparation of p-Aramid RFP that had been incubated with BAL fluid and processed with the enzyme solution resulted in cleavage of p-Aramid RFP. In contrast to the in vitro acellular studies with p-Aramid RFP, the combination of BAL fluid incubation and enzyme digestion method had no measurable effect on shortening of cellulose RFP, indicating that the results with p-Aramid were specific. In vitro cellular studies demonstrated a shortening of p-Aramid RFP in exposed macrophages and co-cultures but not in lung epithelial cells 24 h and 1 week post-exposure. These findings demonstrate that lung fluids coat and activate the p-Aramid RFP as a prerequisite for cleavage and describe a likely mechanism for the biodegradability of inhaled p-Aramid RFP in the lungs of exposed animals.
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Biodegradability of inhaled p-Aramid respirable fibre-shaped particulates: representative of other synthetic organic fibre-types?
International Archives of Occupational and Environmental Health, 2000Co-Authors: D B Warheit, M A Hartsky, T R WebbAbstract:Objectives: Biopersistence, or alternatively, biodegradability (i.e., low biopersistence) represents an important concept in fibre toxicology. The studies described below were undertaken to investigate the mechanisms through which inhaled para-Aramid (p-Aramid) respirable, fibre-shaped particulates (RFP) are biodegraded in the lungs of exposed rats and hamsters; in contrast, cellulose fibres, another organic fibre-type, are known to be biopersistent. To investigate the mechanisms of RFP biodegradation, we have hypothesized that lung fluids activate p-Aramid RFP following deposition, and the RFP are then vulnerable to enzymatic attack in the lungs. Methods: To test the hypothesis, p-Aramid RFP or cellulose RFP were instilled into the lungs of rats and the lungs digested 24 h postexposure using two different digestion techniques: (1) a conventional ethanolic KOH method, and (2) an enzymatic method which simulates lung enzymes. Results: The enzymatic but not the KOH method artificially cleaved the p-Aramid RFP recovered from rat lungs. Next, p-Aramid RFP or cellulose RFP were incubated with saline or lung fluids and then processed by one of the two digestion techniques. Mean lengths of p-Aramid RFP processed with KOH and evaluated by SEM were 13.4 μm; in contrast, mean lengths of p-Aramid RFP samples, incubated in lung fluids and treated with the enzymatic method were 8.8 μm. The enzymatic digestion method had no discernible effect on shortening of cellulose RFP, indicating that the results with p-Aramid were specific. Conclusions: Our data indicate that components of lung fluids coat and catalyze the p-Aramid, thereby predisposing the RFP to enzymatic cleavage. This could play a significant mechanistic role in facilitating the transverse cleavage or shortening of inhaled p-Aramid RFP in the lungs of exposed rats and hamsters.
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Biodegradability of inhaled p-Aramid respirable fibre-shaped particulates: representative of other synthetic organic fibre-types?
International archives of occupational and environmental health, 2000Co-Authors: D B Warheit, M A Hartsky, T R WebbAbstract:Biopersistence, or alternatively, biodegradability (i.e., low biopersistence) represents an important concept in fibre toxicology. The studies described below were undertaken to investigate the mechanisms through which inhaled para-Aramid (p-Aramid) respirable, fibre-shaped particulates (RFP) are biodegraded in the lungs of exposed rats and hamsters; in contrast, cellulose fibres, another organic fibre-type, are known to be biopersistent. To investigate the mechanisms of RFP biodegradation, we have hypothesized that lung fluids activate p-Aramid RFP following deposition, and the RFP are then vulnerable to enzymatic attack in the lungs. To test the hypothesis, p-Aramid RFP or cellulose RFP were instilled into the lungs of rats and the lungs digested 24 h post-exposure using two different digestion techniques: (1) a conventional ethanolic KOH method, and (2) an enzymatic method which simulates lung enzymes. The enzymatic but not the KOH method artificially cleaved the p-Aramid RFP recovered from rat lungs. Next, p-Aramid RFP or cellulose RFP were incubated with saline or lung fluids and then processed by one of the two digestion techniques. Mean lengths of p-Aramid RFP processed with KOH and evaluated by SEM were 13.4 microm; in contrast, mean lengths of p-Aramid RFP samples, incubated in lung fluids and treated with the enzymatic method were 8.8 microm. The enzymatic digestion method had no discernible effect on shortening of cellulose RFP, indicating that the results with p-Aramid were specific. Our data indicate that components of lung fluids coat and catalyze the p-Aramid, thereby predisposing the RFP to enzymatic cleavage. This could play a significant mechanistic role in facilitating the transverse cleavage or shortening of inhaled p-Aramid RFP in the lungs of exposed rats and hamsters.
D B Warheit - One of the best experts on this subject based on the ideXlab platform.
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Mechanistic In Vivo and In Vitro Pulmonary Cellular Studies Demonstrating Biodegradability of Inhaled p-Aramid RFP
The Annals of Occupational Hygiene, 2002Co-Authors: D B Warheit, M A Hartsky, Kenneth L. Reed, T R WebbAbstract:These studies were designed to investigate mechanisms through which inhaled p-Aramid respirable-sized fiber-shaped particulates (RFP) are biodegraded in the lungs of exposed rats and hamsters. We have postulated that lung fluids coat/activate inhaled p-Aramid RFP which deposit in the lung and promote enzymatic attack and consequent shortening. Aliquots of p-Aramid or cellulose (biopersistent control) RFP were instilled into the lungs of rats and the lungs digested 24 h later using two different (KOH or enzymatic) digestion methods. For in vitro studies the two RFP types were incubated with lavage fluid and processed via simulated digestion; in addition, rat lung epithelial cells, macrophages or co-cultures were incubated with p-Aramid and digested 1, 24 or 168 h post-exposure. In vivo the enzyme but not the KOH digestion method resulted in shortening of p-Aramid but not cellulose RFP recovered from rat lungs. The results of in vitro studies showed that mean lengths of p-Aramid RFP incubated with saline and processed by either digestion method were not found to be altered. Indeed, only the preparation of p-Aramid RFP that had been incubated with BAL fluid and processed with the enzyme solution resulted in cleavage of p-Aramid RFP. In contrast to the in vitro acellular studies with p-Aramid RFP, the combination of BAL fluid incubation and enzyme digestion method had no measurable effect on shortening of cellulose RFP, indicating that the results with p-Aramid were specific. In vitro cellular studies demonstrated a shortening of p-Aramid RFP in exposed macrophages and co-cultures but not in lung epithelial cells 24 h and 1 week post-exposure. These findings demonstrate that lung fluids coat and activate the p-Aramid RFP as a prerequisite for cleavage and describe a likely mechanism for the biodegradability of inhaled p-Aramid RFP in the lungs of exposed animals.
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Biodegradability of inhaled p-Aramid respirable fibre-shaped particulates: representative of other synthetic organic fibre-types?
International Archives of Occupational and Environmental Health, 2000Co-Authors: D B Warheit, M A Hartsky, T R WebbAbstract:Objectives: Biopersistence, or alternatively, biodegradability (i.e., low biopersistence) represents an important concept in fibre toxicology. The studies described below were undertaken to investigate the mechanisms through which inhaled para-Aramid (p-Aramid) respirable, fibre-shaped particulates (RFP) are biodegraded in the lungs of exposed rats and hamsters; in contrast, cellulose fibres, another organic fibre-type, are known to be biopersistent. To investigate the mechanisms of RFP biodegradation, we have hypothesized that lung fluids activate p-Aramid RFP following deposition, and the RFP are then vulnerable to enzymatic attack in the lungs. Methods: To test the hypothesis, p-Aramid RFP or cellulose RFP were instilled into the lungs of rats and the lungs digested 24 h postexposure using two different digestion techniques: (1) a conventional ethanolic KOH method, and (2) an enzymatic method which simulates lung enzymes. Results: The enzymatic but not the KOH method artificially cleaved the p-Aramid RFP recovered from rat lungs. Next, p-Aramid RFP or cellulose RFP were incubated with saline or lung fluids and then processed by one of the two digestion techniques. Mean lengths of p-Aramid RFP processed with KOH and evaluated by SEM were 13.4 μm; in contrast, mean lengths of p-Aramid RFP samples, incubated in lung fluids and treated with the enzymatic method were 8.8 μm. The enzymatic digestion method had no discernible effect on shortening of cellulose RFP, indicating that the results with p-Aramid were specific. Conclusions: Our data indicate that components of lung fluids coat and catalyze the p-Aramid, thereby predisposing the RFP to enzymatic cleavage. This could play a significant mechanistic role in facilitating the transverse cleavage or shortening of inhaled p-Aramid RFP in the lungs of exposed rats and hamsters.
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Biodegradability of inhaled p-Aramid respirable fibre-shaped particulates: representative of other synthetic organic fibre-types?
International archives of occupational and environmental health, 2000Co-Authors: D B Warheit, M A Hartsky, T R WebbAbstract:Biopersistence, or alternatively, biodegradability (i.e., low biopersistence) represents an important concept in fibre toxicology. The studies described below were undertaken to investigate the mechanisms through which inhaled para-Aramid (p-Aramid) respirable, fibre-shaped particulates (RFP) are biodegraded in the lungs of exposed rats and hamsters; in contrast, cellulose fibres, another organic fibre-type, are known to be biopersistent. To investigate the mechanisms of RFP biodegradation, we have hypothesized that lung fluids activate p-Aramid RFP following deposition, and the RFP are then vulnerable to enzymatic attack in the lungs. To test the hypothesis, p-Aramid RFP or cellulose RFP were instilled into the lungs of rats and the lungs digested 24 h post-exposure using two different digestion techniques: (1) a conventional ethanolic KOH method, and (2) an enzymatic method which simulates lung enzymes. The enzymatic but not the KOH method artificially cleaved the p-Aramid RFP recovered from rat lungs. Next, p-Aramid RFP or cellulose RFP were incubated with saline or lung fluids and then processed by one of the two digestion techniques. Mean lengths of p-Aramid RFP processed with KOH and evaluated by SEM were 13.4 microm; in contrast, mean lengths of p-Aramid RFP samples, incubated in lung fluids and treated with the enzymatic method were 8.8 microm. The enzymatic digestion method had no discernible effect on shortening of cellulose RFP, indicating that the results with p-Aramid were specific. Our data indicate that components of lung fluids coat and catalyze the p-Aramid, thereby predisposing the RFP to enzymatic cleavage. This could play a significant mechanistic role in facilitating the transverse cleavage or shortening of inhaled p-Aramid RFP in the lungs of exposed rats and hamsters.
M A Hartsky - One of the best experts on this subject based on the ideXlab platform.
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Mechanistic In Vivo and In Vitro Pulmonary Cellular Studies Demonstrating Biodegradability of Inhaled p-Aramid RFP
The Annals of Occupational Hygiene, 2002Co-Authors: D B Warheit, M A Hartsky, Kenneth L. Reed, T R WebbAbstract:These studies were designed to investigate mechanisms through which inhaled p-Aramid respirable-sized fiber-shaped particulates (RFP) are biodegraded in the lungs of exposed rats and hamsters. We have postulated that lung fluids coat/activate inhaled p-Aramid RFP which deposit in the lung and promote enzymatic attack and consequent shortening. Aliquots of p-Aramid or cellulose (biopersistent control) RFP were instilled into the lungs of rats and the lungs digested 24 h later using two different (KOH or enzymatic) digestion methods. For in vitro studies the two RFP types were incubated with lavage fluid and processed via simulated digestion; in addition, rat lung epithelial cells, macrophages or co-cultures were incubated with p-Aramid and digested 1, 24 or 168 h post-exposure. In vivo the enzyme but not the KOH digestion method resulted in shortening of p-Aramid but not cellulose RFP recovered from rat lungs. The results of in vitro studies showed that mean lengths of p-Aramid RFP incubated with saline and processed by either digestion method were not found to be altered. Indeed, only the preparation of p-Aramid RFP that had been incubated with BAL fluid and processed with the enzyme solution resulted in cleavage of p-Aramid RFP. In contrast to the in vitro acellular studies with p-Aramid RFP, the combination of BAL fluid incubation and enzyme digestion method had no measurable effect on shortening of cellulose RFP, indicating that the results with p-Aramid were specific. In vitro cellular studies demonstrated a shortening of p-Aramid RFP in exposed macrophages and co-cultures but not in lung epithelial cells 24 h and 1 week post-exposure. These findings demonstrate that lung fluids coat and activate the p-Aramid RFP as a prerequisite for cleavage and describe a likely mechanism for the biodegradability of inhaled p-Aramid RFP in the lungs of exposed animals.
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Biodegradability of inhaled p-Aramid respirable fibre-shaped particulates: representative of other synthetic organic fibre-types?
International Archives of Occupational and Environmental Health, 2000Co-Authors: D B Warheit, M A Hartsky, T R WebbAbstract:Objectives: Biopersistence, or alternatively, biodegradability (i.e., low biopersistence) represents an important concept in fibre toxicology. The studies described below were undertaken to investigate the mechanisms through which inhaled para-Aramid (p-Aramid) respirable, fibre-shaped particulates (RFP) are biodegraded in the lungs of exposed rats and hamsters; in contrast, cellulose fibres, another organic fibre-type, are known to be biopersistent. To investigate the mechanisms of RFP biodegradation, we have hypothesized that lung fluids activate p-Aramid RFP following deposition, and the RFP are then vulnerable to enzymatic attack in the lungs. Methods: To test the hypothesis, p-Aramid RFP or cellulose RFP were instilled into the lungs of rats and the lungs digested 24 h postexposure using two different digestion techniques: (1) a conventional ethanolic KOH method, and (2) an enzymatic method which simulates lung enzymes. Results: The enzymatic but not the KOH method artificially cleaved the p-Aramid RFP recovered from rat lungs. Next, p-Aramid RFP or cellulose RFP were incubated with saline or lung fluids and then processed by one of the two digestion techniques. Mean lengths of p-Aramid RFP processed with KOH and evaluated by SEM were 13.4 μm; in contrast, mean lengths of p-Aramid RFP samples, incubated in lung fluids and treated with the enzymatic method were 8.8 μm. The enzymatic digestion method had no discernible effect on shortening of cellulose RFP, indicating that the results with p-Aramid were specific. Conclusions: Our data indicate that components of lung fluids coat and catalyze the p-Aramid, thereby predisposing the RFP to enzymatic cleavage. This could play a significant mechanistic role in facilitating the transverse cleavage or shortening of inhaled p-Aramid RFP in the lungs of exposed rats and hamsters.
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Biodegradability of inhaled p-Aramid respirable fibre-shaped particulates: representative of other synthetic organic fibre-types?
International archives of occupational and environmental health, 2000Co-Authors: D B Warheit, M A Hartsky, T R WebbAbstract:Biopersistence, or alternatively, biodegradability (i.e., low biopersistence) represents an important concept in fibre toxicology. The studies described below were undertaken to investigate the mechanisms through which inhaled para-Aramid (p-Aramid) respirable, fibre-shaped particulates (RFP) are biodegraded in the lungs of exposed rats and hamsters; in contrast, cellulose fibres, another organic fibre-type, are known to be biopersistent. To investigate the mechanisms of RFP biodegradation, we have hypothesized that lung fluids activate p-Aramid RFP following deposition, and the RFP are then vulnerable to enzymatic attack in the lungs. To test the hypothesis, p-Aramid RFP or cellulose RFP were instilled into the lungs of rats and the lungs digested 24 h post-exposure using two different digestion techniques: (1) a conventional ethanolic KOH method, and (2) an enzymatic method which simulates lung enzymes. The enzymatic but not the KOH method artificially cleaved the p-Aramid RFP recovered from rat lungs. Next, p-Aramid RFP or cellulose RFP were incubated with saline or lung fluids and then processed by one of the two digestion techniques. Mean lengths of p-Aramid RFP processed with KOH and evaluated by SEM were 13.4 microm; in contrast, mean lengths of p-Aramid RFP samples, incubated in lung fluids and treated with the enzymatic method were 8.8 microm. The enzymatic digestion method had no discernible effect on shortening of cellulose RFP, indicating that the results with p-Aramid were specific. Our data indicate that components of lung fluids coat and catalyze the p-Aramid, thereby predisposing the RFP to enzymatic cleavage. This could play a significant mechanistic role in facilitating the transverse cleavage or shortening of inhaled p-Aramid RFP in the lungs of exposed rats and hamsters.
Henry Angelo Sodano - One of the best experts on this subject based on the ideXlab platform.
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Aramid nanofibers for multiscale fiber reinforcement of polymer composites
Composites Science and Technology, 2018Co-Authors: Brendan A. Patterson, Jiajun Lin, Angelica Okorom, Mohammad H. Malakooti, Henry Angelo SodanoAbstract:While Aramid fibers have been innovative for ballistic protection because of their high energy absorption, minimal usage has been applied to continuous fiber reinforced polymer (CFRP) composites in structural applications. One of the challenges with Aramid fibers results from their processing, which yields smooth and chemically inert surfaces that limit the ability of the fibers to adhere to polymeric matrices. Here, it is shown that Aramid nanofibers can adhere to the surface of macroscale Aramid reinforcements to improve the strength of the composite interface and reinforce the matrix as well. Aramid nanofibers are formed through the dissolution of Aramid fibers followed by isolation and dispersion into an epoxy matrix. When employed in CFRP, Aramid nanofibers prove to be effective reinforcement agents through improvement in both matrix properties as well as modifying the interfacial shear strength, which leads to improved interlaminar shear strength and fracture toughness. The interface enhancements are attributed to hydrogen bonding and π-π coordination between the Aramid nanofibers and the macro fibers providing improved transfer load from the fiber to the matrix. This work demonstrates that Aramid nanofibers may provide the robust mechanical properties that are necessary for structural applications while utilizing a cost-effective and convenient nanoscale building block.
Q Q Zhou - One of the best experts on this subject based on the ideXlab platform.
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surface modification of Aramid fiber by plasma induced vapor phase graft polymerization of acrylic acid i influence of plasma conditions
Applied Surface Science, 2015Co-Authors: Chaonan Wang, M Du, J C Lv, Q Q ZhouAbstract:Plasma induced vapor phase graft polymerization (PIVPGP) method was applied to modify Aramid fiber surface. In this study, Aramid fibers were pretreated under various plasma conditions such as different treatment times, output powers and working gases to see how these plasma processing parameters influenced the PIVPGP of acrylic acid (AA) on Aramid fiber surface and its surface structure and properties. The analysis results of atomic force microscope (AFM) and X-ray photoelectron spectroscope (XPS) showed the increase of surface roughness and the introduction of O=C OH, which confirmed that the PIVPGP of AA on Aramid fiber surface was achieved. The contact angle and interfacial shear strength (IFSS) of the Aramid fibers modified by PIVPGP of AA prominently decreased and increased, respectively, indicating the obvious improvements of surface wettability and adhesion between Aramid fiber and matrix. The surface modification effects of Aramid fiber by PIVPGP of AA firstly increased and then after 15 min slightly decreased with the increasing plasma treatment time, and but firstly increased and then after 300W nearly remained unchanged with the increasing output power, respectively. Among different working gases, Ar plasma occupied first place, O-2 plasma and N-2 plasma came second and third in the aspect of PIVPGP of AA on Aramid fiber surface, respectively. It could be concluded that the PIVPGP of AA on Aramid fiber surface could effectively improve surface wettability and adhesion. Plasma conditions had signally influence on the efficiency of PIVPGP of AA on Aramid fiber surface and its surface structure and properties with the primary sequence of plasma treatment time, output power and working gas. Therefore adequate plasma processing parameters should be carefully selected for the optimum surface modification of Aramid fiber by PIVPGP of AA. (C) 2015 Elsevier B.V. All rights reserved.