Cross-linked Poly Acrylic Acid Research Articles

Inhalation Exposure to Cross-linked Polyacrylic Acid Induces Pulmonary Disorders.

Organic polymers, widely used in food, daily necessities, and medicines, include cross-linked polyacrylic acid (CL-PAA), which has been reported to induce severe lung disease. While previous studies mainly used intratracheal instillation, our research focused on inhalation exposure to corroborate these findings. We conducted 5-day (short-term) and 13-week (subchronic) inhalation exposure studies with CL-PAA. In the short-term study, male F344 rats inhaled CL-PAA at 0.2, 2.0, or 20mg/m³ for 6hours/day over 5 days. Rats were dissected 3 days and 1 month post-exposure. In the subchronic study, rats inhaled CL-PAA at 0.2 or 2.0mg/m³ for 6hours/day, 5 days/week for 13 weeks, with dissections from 3 days to 6 months post-exposure. To investigate the mechanism of pulmonary disorders, an additional short-term study with 20mg/m³ CL-PAA included intraperitoneal injections of the antioxidant N-acetylcysteine (NAC) (200mg/kg) with dissection the day after exposure. Short-term exposure led to concentration-dependent increases in neutrophil influx, cytokine-induced neutrophil chemoattractant (CINC), total protein, lactate dehydrogenase (LDH) in bronchoalveolar lavage fluid (BALF), and heme oxygenase-1 (HO-1) in lung tissue. Histopathology showed concentration-dependent neutrophil infiltration. Subchronic exposure caused persistent increases in BALF total protein and lung HO-1, with ongoing neutrophil infiltration and fibrosis. NAC administration reduced neutrophils, total protein, LDH, and CINC in BALF, and HO-1 in lung tissue, improving histopathological findings. Inhalation of CL-PAA caused concentration-dependent lung inflammation and persistent fibrosis. The no observed adverse effect level (NOAEL) for chronic pulmonary disorders was 0.2mg/m³. Oxidative stress linked to CL-PAA-induced inflammation was mitigated by NAC administration.

Thermal conductivity of Al2O3 nanofluid utilizing cross-linked polyacrylic acid (PAA) as the base fluid: An experimental study

Thermal conductivity of Al2O3 nanofluid utilizing cross-linked polyacrylic acid (PAA) as the base fluid: An experimental study

A Triple Crosslinked Binder with Hierarchical Stress Dissipation and High Ionic Conductivity for Advanced Silicon Anodes in Lithium-ion Batteries.

Silicon (Si) is a promising anode material for high-energy-density lithium-ion batteries, but the significant volume change of Si particles during alloying/dealloying with lithium (Li) undermines the mechanical integrity of Si anode, causing electrode fracture, delamination and rapid capacity decay. Herein, a robust triple crosslinked network (TCN) binder with high ionic conductivity and hierarchical stress dissipation is reported for Si anodes, which is prepared by in situ chemical crosslinking polyacrylic acid (PAA) and melamine (MA). The triple interactions of hydrogen bonds, electrostatic interactions, and covalent amide bonds enhance the adhesion of binder to Si and synergistically promote stress dissipation within Si anodes, thus strengthening the dynamic structural stability of Si anodes during cycling. Moreover, the rapid coupling/decoupling of Li+ with the TCN binder enables an impressive Li+ transference number of 0.63 and high ionic conductivity of 1.2 × 10-4 Scm-1. Consequently, the Si-TCN anode delivers specific capacity of 2268 mAhg-1 with a high mass loading of 2mgcm-2, high-rate performance of 1673 mAhg-1 at 5 Ag-1, and stable cycling for 250 cycles at 1 Ag-1, thus showing great prospects for high-energy-density Si-based batteries.

Structure, Property Optimization, and Adsorption Properties of N,N'-methylenebisacrylamide Cross-Linked Polyacrylic Acid Hydrogels under Different Curing Conditions.

In this study, polyacrylic acid hydrogels were prepared by modulating the cross-linking agent mass ratio using UV and heat curing methods. The structures and properties of the hydrogels were characterized and analyzed using Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis. The results showed that the mechanical properties of the hydrogels prepared through UV curing were better than those prepared through heat curing. The maximum mechanical tensile strength of 139 kPa was achieved at a cross-linking agent mass ratio of 3.85% with 20 min of UV curing, and the maximum mechanical compressive strength of 0.16 MPa was achieved at a cross-linking agent mass ratio of 2.91% with 20 min of UV curing. However, the hydrogels prepared by heat curing had a higher tensile strength than those prepared using the heat curing method. In addition, the thermally cured hydrogels had higher water absorption and adsorption properties. Moreover, the PAA hydrogels prepared at cross-linking agent mass ratios of 1.91 and 2.91% with 2 h of the heat curing method had the best swelling properties. Moreover, the increase in the cross-linker mass concentration led to a decrease in the pore size and porosity and to a more compact structure.

Iridium complexes supported on cross-linked polyacrylic acid as release-and-catch catalysts for continuous formic acid dehydrogenation

We developed an iridium complex on cross-linked polyacrylic acid as a release-and-catch catalyst. It shows FA dehydrogenation activity comparable to homogeneous catalysts, and was recycled 10 times completely, advancing FA-based H2 carriers.

Comprehensive analysis of cationic dye removal from synthetic and industrial wastewater using a semi-natural curcumin grafted biochar/poly acrylic acid composite hydrogel.

Polymer composites offer a tailored framework as an exceptional candidate for water treatment due to their tunable chemical structure, porous 3D architecture, physiochemical stability, accessibility, pH-sensitivity and ease of use. In this study, curcumin-engineered biochar is embedded into a cross-linked polyacrylic acid hydrogel matrix using in situ polymerization for developing a semi-natural adsorbent for the removal of cationic dye from an aqueous solution. The physicochemical features of the generated composite hydrogel are significantly influenced by the implementation of curcumin-grafted biochar into the polyacrylic acid substrate. Comprehensive characteristic approaches were employed to explore all aspects of the adsorbent's properties, especially its removal efficacy. The methodical adsorption study was accomplished by monitoring dynamic factors such as pH, adsorbent content, time frame, and initial dye concentration. The presence of the porous aromatized structure of biochar, active oxygen-enrich functional groups (carboxyl, hydroxyl, keto, enol, ether) coupled with the conjugated curcumin structure facilitate the effective establishment of hydrogen bonds, electrostatic interactions, π-π interactions, electron donor-acceptor and charge-assisted H-bonding with the malachite green (MG) and rhodamine B (Rho) molecules. The highest adsorption capacities of MG and Rho reached 521 mg g-1 and 741 mg g-1 respectively, in the range of neutral pH, considering their molecular nature, functionalities, and unique adsorption mechanisms. The isothermal modeling was carried out with Henry, Langmuir, Jovanovic, Freundlich, Temkin, and Koble-Corrigan models to determine the adsorption system. Additionally, the kinetic data were assessed with Bangham, pseudo-first-order, pseudo-second-order, intra-particle, and liquid film diffusion models to ascertain the rate-limiting phase. The Koble-Corrigan and Langmuir isotherm models (R2 > 0.997) as well as pseudo-second-order (R2 > 0.998) and Elovich (R2 = 0.983 and 0.995) kinetics models provide a substantial level of concordance with empirical findings. The analysis of non-linear diffusion models revealed that the Bangham (R2 > 0.995) pore and liquid film diffusion (R2 > 0.960) models has major influence on the rate of the adsorption procedure. The binary adsorption test demonstrated higher efficacy of the synthesized adsorbent in the removal of malachite as compared to rhodamine. This study sheds light on the design of a cost-effective semi-natural polymeric composite for treating dye-polluted wastewaters, a major milestone toward environmental and ecological sustainability.

Development of hierarchically constructed robust multifunctional hydrogels for sensitive strain sensors by using guar gum and polydopamine to encapsulate liquid metal droplets

Conductive hydrogels have aroused tremendous interest as strain sensing materials because of their good biocompatibility, high stretchability, and structural similarity to natural soft tissues. However, fabricating a multifunctional conductive hydrogel that simultaneously exhibits high toughness, high sensing performance and a low detection limit remains a challenge. Herein, we developed a new conductive hydrogel with a hierarchical cluster network structure by using soft Ga droplets encapsulated by guar gum (GG), in situ polymerized polydopamine (PDA) as conductive materials and in situ synthesized/Ga3+-crosslinked poly acrylic acid (PAA) as a ductile hydrogel matrix. GG and PDA around Ga droplets constituted physically crosslinked dense rigid networks. Because of its completely physically crosslinked hierarchical cluster network structure with Ga droplets, the hydrogel, which was named GG-PDA-Ga-PAA, exhibited high toughness (1.8 MJ/m3), good moldability, adhesiveness, antibacterial activity and excellent self-healing properties. Its conductivity recovered more than 90 % within 83 ms, while its tensile strength (213.2 kPa) and elongation at break (1364 %) recovered 92.8 % and 100 %, respectively, within 6 h. When applied as a strain sensing material, the GG-PDA-Ga-PAA hydrogel displayed high sensitivity (GF=10.83), short response/recovery time (167/167 ms), ultralow detection limit (0.2 %) and good fatigue resistance and cyclic stability (1000 cycles). Due to its excellent comprehensive properties, the hydrogel can be applied as a competent wearable stain sensor for monitoring various human activities from pulses in the radial artery to human joint bending. This work provides a new approach for producing multifunctional conductive hydrogels for strain sensors.

A Smart Stimulation-Deadhesion and Antimicrobial Hydrogel for Repairing Diabetic Wounds Infected with Methicillin-Resistant Staphylococcus aureus.

The healing of chronic diabetic wounds is a common and significant challenge in the medical field. Despite extensive efforts, the development of hydrogel dressings with satisfactory functionality remains an ongoing concern. In this study, a multifunctional hydrogel wound dressing (PAN/Ag-PLG) with adhesion, antibacterial, hemostatic, and other properties, which can effectively repair diabetic wounds infected with methicillin-resistant Staphylococcus aureus (MRSA), ispresented. The hydrogel dressing is composed of gallic acid (GA)-functionalized polylysine (PL)-reduced silver nanoparticles (Ag-PLG), oxidized hyaluronic acid (OHA), and cross-linked polyacrylic acid grafted with N-hydrosuccinimide ester. Notably, compared to most conventional wound dressing that lack adhesion or are difficult to remove, the prepared hydrogels exhibit excellent adhesion and mild stimulation-triggered detachment. In vitro and in vivo experiments reveal that the PAN/Ag-PLG hydrogel exhibits outstanding biocompatibility and antibacterial properties and promotes diabetic wound repair by reducing oxidative damage and promoting cell migration and angiogenesis. The smart PAN/Ag-PLG hydrogel reported in this study provides an approach for the potential clinical development of painless antibacterial dressings.

Polyaniline-MXene composite electrode with excellent electrochemical properties for all-solid flexible supercapacitors

In this paper, MXene based electrode active materials and MXene cross-linked polyacrylic acid hydrogel electrolytes with high cycling performance and high specific capacitance have been successfully prepared. Polyaniline with high capacitance values has been grown on the MXene surface by in situ polymerization, which can significantly improve electrochemical properties. As the MXene surface is rich in functional groups, it can be used as a nucleation site for in situ polymerization of aniline monomers deposited. The PANI filled with MXene forms a 3D porous conductive network reducing the self-stacking of MXene and providing a large number of channels for electrolyte ions to enter MXene. The supercapacitor has been tested and assembled with good flexibility and the specific capacitance has risen to 222 F g−1. The capacitance retention of 98.5 % after 10,000 charges and discharges is due to the improved performance of the composite material and the excellent stability of the gel electrolyte and electrodes. The above results show that the prepared electrodes and devices have promising applications in flexible wearable devices.

Crosslinked Structure of Polyacrylic Acid Affects Pulmonary Fibrogenicity in Rats.

We conducted intratracheal instillations of polyacrylic acid (PAA) with crosslinking and non-crosslinking into rats in order to examine what kinds of physicochemical characteristics of acrylic-acid-based polymers affect responses in the lung. F344 rats were intratracheally exposed to similar molecular weights of crosslinked PAA (CL-PAA) (degree of crosslinking: ~0.1%) and non-crosslinked PAA (Non-CL-PAA) at low and high doses. Rats were sacrificed at 3 days, 1 week, 1 month, 3 months, and 6 months post-exposure. Both PAAs caused increases in neutrophil influx, cytokine-induced neutrophil chemoattractants (CINC) in the bronchoalveolar lavage fluid (BALF), and heme oxygenase-1 (HO-1) in the lung tissue from 3 days to 6 months following instillation. The release of lactate dehydrogenase (LDH) activity in the BALF was higher in the CL-PAA-exposed groups. Histopathological findings of the lungs demonstrated that the extensive fibrotic changes caused by CL-PAA were also greater than those in exposure to the Non-CL- PAA during the observation period. CL-PAA has more fibrogenicity of the lung, suggesting that crosslinking may be one of the physicochemical characteristic factors of PAA-induced lung disorder.

A toughened, transparent, anti-freezing and solvent-resistant hydrogel towards environmentally tolerant strain sensor and soft connection

Low-temperature tolerant and solvent-resistant soft electronic devices have received increasing attention due to their excellent adaptability under multiple environments. Herein, the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and zwitterionic betaine (ZB) are introduced into the Al3+ cross-linked polyacrylic acid (PAA) networks to construct a multipurpose hydrogel (PAA-Al3+/PEDOT:PSS/ZB), which exhibits superior stretchability (1457 %), tensile strength (1.43 MPa), freeze-tolerance (−35 °C) and solvent-resistant capability. Furthermore, a strain sensor with multi-environmental stability is fabricated based on this hydrogel, which could not only accurately monitor the different human motions (finger bending, writing, swallowing, breathing, walking, head-up/down and wrist-up/down) at room temperature, but also reliably distinguish the various mechanical deformations in diverse solvent media (water, cyclohexane and methylbenzene) and harsh climatic condition (−35 °C). In addition, a flexible tube-shaped PAA-Al3+/PEDOT:PSS/ZB hydrogel is also successfully developed in the specific reaction mold, which can be utilized as a soft connection for the tap or two severed glass tubes to transport different liquids benefiting from the significant mechanical toughness and anti-swelling property. It is anticipated that the as-prepared hydrogel may be a promising flexible material with multi-environmental stability applying in biomedical devices, soft robotics, electronic skins and wearable sensors under complex environments.

Chitosan-based dual network composite hydrogel for efficient adsorption of methylene blue dye

With the rapid development of the textile industry, a large amount of dyeing wastewater discharge has caused great harm to the ecological environment. In this work, a dual-network, composite hydrogel adsorbent with excellent mechanical properties, good reusability, and large adsorption capacity was prepared by introducing chitosan cross-linked polyvinylamine into the N,N′-methylenebisacrylamide cross-linked polyacrylic acid network. The dual cross-linking network gave the hydrogel excellent mechanical properties with maximum tensile stress and strain up to 1.9 MPa and 920 %. The adsorption capacity of methylene blue on hydrogel was up to 596.14 mg/g. In addition, the prepared hydrogel exhibited good reusability, and their adsorption efficiency remained above 85 % in five consecutive cycles. The adsorption behavior was well fitted by Pseudo-second-order kinetics and the Langmuir equation, indicating that the hydrogel was chemisorbed to the dye as a monolayer. The adsorption mechanism analysis showed that the electrostatic interactions and hydrogen bonding between the functional groups of the hydrogels and methylene blue molecules contributed to the good adsorption capacity. Overall, the synthesized composite hydrogels could be used as an efficient adsorbent for the removal of methylene blue dye, particularly from textile industry wastewater.

Design of co-continuous structure of cellulose/PAA-based alkaline solid polyelectrolyte for flexible zinc-air battery

In order to prepare high ionic conductivity and robust mechanical properties of alkaline solid polyelectrolyte (ASPE) for applications in flexible wearable devices, a co-continuous structure membrane was designed using in-situ polymerization to introduce cross-linked polyacrylic acid (N-PAA) into the cellulose network constructed by regenerated degreasing cotton (RDC). The resultant ASPE membrane showed high ionic conductivity (430 mS·cm−1 at 25 °C), strong mechanical properties, and excellent alkaline stabilities, proving the viability of cellulose for use in energy storage systems. Surprisingly, the sandwich-shaped zinc-air battery assembled using RDC/N-PAA/KOH membranes as electrolytes exhibits superior values of cycling stability, discharge time, specific capacity (731.5 mAh·g−1), peak power density (40.25 mW·cm−2), and mechanical flexibility. Even under bending conditions, the zinc-air batteries still possess stable energy supply performance, suggesting this novel solid polyelectrolyte has promising application for wearable technology.

Cross-Linking Network of Soft–Rigid Dual Chains to Effectively Suppress Volume Change of Silicon Anode

Polyacrylic acid (PAA) is a promising binder for the high-capacity Si anode. However, the one-dimensional structure of PAA could cause the linear molecular chains to slide from the Si surface during the charge-discharge processes, leading to insufficient suppression of the massive volume expansion of the Si anode. Herein, a soft-rigid dual chains' network of PAA-sodium silicate (PAA-SS) was successfully constructed by cross-linking PAA and SS in situ at room temperature. The soft chains of PAA and the rigid chains of polysilicic acid synergistically ensure the enhanced adhesion property and mechanical strength. Therefore, the Si electrode with PAA-SS binder delivers a discharge capacity of 1559 mAh/g after 150 cycles at 4.2 A/g (1C) with an initial Coulombic efficiency of 93.2%. Moreover, the PAA-SS based SiC-500 electrode exhibits a discharge capacity of 441 mAh/g with the capacity retention of 88.2% after 500 cycles at 0.5 A/g, implying the PAA-SS binder's great industrial prospect in Si based electrodes.

Preparation, properties, self crosslinking mechanism, and characterization of UV initiated polyacrylic acid superabsorbent resins

AbstractThe self crosslinking polyacrylic acid (PAAsc) superabsorbent resins were prepared by UV irradiation without crosslinking agents and initiators. The effects of reaction factors on water absorbency and gel content of resins were investigated. The mechanism of self crosslinking polymerization was studied by means of 1H NMR and ESR, while the structure and morphology of the resins were characterized by IR, NMR, and SEM. The results show that the polymerization mechanism and structure of PAAsc superabsorbent resins polymerized through light radiation is significantly different from those polymerized by initiators. The main chain of PAAsc contains double bonds and polar functional groups such as ether groups and ester groups, which improves the hydrophilicity of the main chain and significantly improves the liquid absorption ability of the superabsorbent material. Moreover, the swelling kinetics, salt‐resistance, pH sensitivity, and water retention capacity of the PAAsc superabsorbents were studied. Owing to the remarkable water absorbency, salt resistance property and water retention capacity, this superabsorbent material has a broad application prospect in agriculture.

Assessment of the Influence of the Selected Range of Visible Light Radiation on the Durability of the Gel with Ascorbic Acid and Its Derivative

(1) Background: Depending on the type of hydrophilic polymer used, different types of hydrogels may be chemically stable or may degrade and eventually disintegrate, or dissolve upon exposure to sunlight. Many over-the-counter medications are now stored with a limited control of temperature, humidity and lighting. Therefore, in this study, the photostability of a gel made of cross-linked polyacrylic acid (PA), methylcellulose (MC) and aristoflex (AV) was assessed, and the interaction between the polymers used and ascorbic acid and its ethylated derivative was investigated. (2) Methods: The samples were continuously irradiated at constant temperature for six hours. The stability of the substance incorporated into the gels was assessed using a UV-Vis spectrophotometer. FTIR-ATR infrared spectroscopy was used to measure changes during the exposure. (3) Results: Ascorbic acid completely decomposed between the first and second hours of illumination in all samples. The exception is the preparation based on polyacrylic acid with glycerol, in which the decomposition of ascorbic acid slowed down significantly. After six hours of irradiation, the ethylated ascorbic acid derivative decomposed in about 5% for the polyacrylic acid-based gels and aristoflex, and in the methylcellulose gel it decomposed to about 2%. In the case of ascorbic acid, the most stable formulation was a gel based on polyacrylic acid and polyacrylic acid with glycerol, and in the case of the ethyl derivative, a gel based on methylcellulose. (4) Conclusions: The experiment showed significant differences in the decomposition rate of both compounds, resulting from their photostability and the polymer used in the hydrogel.

Activated carbon nanotube/polyacrylic acid/stearyl alcohol nanocomposites as thermal energy storage effective shape-stabilized phase change materials

Stearyl alcohol (SA) as one of organic phase change materials (PCMs) has promising thermal energy storage prospective. However, the leakage issue during solid-liquid phase change period and low heat harvesting and releasing rate significantly attenuates its TES potential. Towards to overcome these drawbacks, the SA was shape-stabilized using the cross-linked poly acrylic acid (PAA) and activated single walled carbon nanotubes (a-SWCNTs) at three different weigh ratio of 1:1:2, 1:3:4 and 1:5:6 (a-SWCNTs:PAA:SA). The chemical/crystalline and morphologic structures of the produced shape stabilized-nano composite PCMs (SS-NCPCMs) were investigated by FT-IR, XRD and SEM analyses. The latent heat storage (LHS) features and thermal stability of the SS-NCPCMs were measured by DSC and TGA techniques. The thermal cycling effect on the LHS properties and chemical structures of the SS-NCPCMs was also estimated. The DSC findings indicated that the SS-NCPCMs had melting temperature of around 55–56 °C and latent heat capacity of about 135 J/g. TGA measurements disclosed that the thermal degradation temperatures of the nano composite PCMs were prolonged somewhat compared to the SA. A 500 heating-cooling cycling test revealed that the SS-NCPCMs had great chemical and LHS stability. The heat harvesting and releasing performance of the NCPCMs were considerably shortened compared to those of pure SA. The obtained results exposed that the synthesized SWCNTs/PAA/SA composites can be evaluated as promising LHS materials for thermal management of electronic systems, automobile modules, food carriers, solar PV panels etc.

Mechanically toughened conductive hydrogels with shape memory behavior toward self-healable, multi-environmental tolerant and bidirectional sensors

• A toughened, self-healing, anti-freezing, anti-drying, and anti-swelling hydrogel is prepared. • Hydrogel sensors exhibit excellent self-healing capability and multi-environmental stability. • Hydrogel sensors display an attracting feature on distinguishing the direction of human motion. • Hydrogels possess significant shape memory and information storage functions even at −40 °C. Conductive hydrogels have considered as promising materials to revolutionize flexible electronics, biomedical devices and soft robotics. Despite significant progress has been made in the design of hydrogels, simultaneous realization of outstanding mechanical properties, self-healing capability, multi-environmental tolerance (e.g., freezing, drying, water, and oil), and multiple stimuli-responsiveness in a single hydrogel still remains a tremendous challenge. Herein, an extraordinary stretchable (1769%), toughened (0.46 MPa), self-healing, water-retaining (78% after 8 days), anti-freezing (below −40 °C), and anti-swelling (in water/organic solvents) conductive hydrogel is designed and prepared by simultaneously introducing zwitterionic proline, metal ions, and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) into vinyl hybrid silica nanoparticles cross-linked polyacrylic acid networks. Based on this hydrogel, the fabricated strain sensor exhibits excellent strain sensitivity (GF = 3.07), wide sensing range (from 5 to 700%), reliable stability (800 cycles at 200% strain), and accurate human motion detection along two opposite directions (bend down or bend up). In particular, it can not only withstand outstanding mechanical damages but also maintain stable sensing performances in water/organic solvent environments and freezing condition of −40 °C. More interestingly, under FeCl 3 -EG (ethylene glycol) and ascorbic acid-EG solution external stimuli, the resultant hydrogels also display the significant shape memory behaviors and repeated information recording/erasing capabilities even at an extremely cold temperature (−40 °C). These remarkable performances greatly expand the application fields of hydrogels in harsh environments.

Application of a Cross-linked Polyacrylic Acid- Polyethylene Oxide (PAA-PEO) Copolymer as a Binder for Si@C@PDA Composite Anode Materials in Li-ion Batteries

Application of a Cross-linked Polyacrylic Acid- Polyethylene Oxide (PAA-PEO) Copolymer as a Binder for Si@C@PDA Composite Anode Materials in Li-ion Batteries

Inflammogenic effect of polyacrylic acid in rat lung following intratracheal instillation

BackgroundSome organic chemicals are known to cause allergic disorders such as bronchial asthma and hypersensitivity pneumonitis, and it has been considered that they do not cause irreversible pulmonary fibrosis. It has recently been reported, however, that cross-linked acrylic acid-based polymer, an organic chemical, might cause serious interstitial lung diseases, including pulmonary fibrosis. We investigated whether or not intratracheal instillation exposure to cross-linked polyacrylic acid (CL-PAA) can cause lung disorder in rats.MethodsMale F344 rats were intratracheally instilled with dispersed CL-PAA at low (0.2 mg/rat) and high (1.0 mg/rat) doses, and were sacrificed at 3 days, 1 week, 1 month, 3 months and 6 months after exposure to examine inflammatory and fibrotic responses and related gene expressions in the lungs. Rat lungs exposed to crystalline silica, asbestos (chrysotile), and NiO and CeO2 nanoparticles were used as comparators.ResultsPersistent increases in total cell count, neutrophil count and neutrophil percentage, and in the concentration of the cytokine-induced neutrophil chemoattractant (CINC)-1, CINC-2 and C-X-C motif chemokine 5 (CXCL5), which correlated with lung tissue gene expression, were observed in bronchoalveolar lavage fluid (BALF) from 3 days until at least 1 month following CL-PAA intratracheal instillation. Persistent increases in heme oxygenase-1 (HO-1) in the lung tissue were also observed from 3 days to 6 months after exposure. Histopathological findings of the lungs demonstrated that extensive inflammation at 3 days was greater than that in exposure to silica, NiO nanoparticles and CeO2 nanoparticles, and equal to or greater than that in asbestos (chrysotile) exposure, and the inflammation continued until 1 month. Fibrotic changes also progressed after 1 month postexposure.ConclusionOur results suggested that CL-PAA potentially causes strong neutrophil inflammation in the rat and human lung.