Midstream on a chip: ensuring safe carbon dioxide transportation for carbon capture and storage.

Emerging technologies like enhanced oil recovery and carbon sequestration rely on carbon dioxide water content data to ensure that pipelines remain sub-saturated to avoid corrosion and hydrate flow assurance issues. To improve throughput and confidence in the hydrate phase equilibria data to avoid pipeline blockages, further research into the carbon dioxide water content must be conducted. However, the liquid carbon dioxide regime is experimentally difficult to study and the available data disagree between studies. This work aims to provide the critical and accurate data for liquid carbon dioxide for a high pressure range (13.8 to 103.4 bar) and temperature range (20 and -30 °C) utilizing a small volume microfluidic reactor (<20 microliter) coupled with Raman spectroscopy, which can reveal any phase metastability in the system. The small volume of the microfluidic system (<20 microliter) allowed experiments to be run in a few hours, compared to a whole week for prior larger scale measurements. The carbon dioxide water content results from this work agree well with both model predictions and available literature data in the gas region; however, once carbon dioxide was converted to liquid, the data showed a weak function of pressure, similar to model predictions and some previous data sets. The discrepancies between literature data are attributed to metastable phases present in the equilibrium cells, as the data is usually taken in the carbon dioxide near critical region, close to carbon dioxide's dew point, and near the hydrate phase transition. For these reasons, it is important to observe and qualify all phases in the cell, as was done in this novel study with in situ Raman spectroscopy coupled to Midstream on a chip, to ensure accurate water content of the carbon dioxide fluid phase is being measured.

Carbon dioxide hydrate in a microfluidic device: Phase boundary and crystallization kinetics measurements with micro-Raman spectroscopy.

Various emerging carbon capture technologies depend on being able to reliably and consistently grow carbon dioxide hydrate, particularly in packed media. However, there are limited kinetic data for carbon dioxide hydrates at this length scale. In this work, carbon dioxide hydrate propagation rates and conversion were evaluated in a high pressure silicon microfluidic device. The carbon dioxide phase boundary was first measured in the microfluidic device, which showed little deviation from bulk predictions. Additionally, measuring the phase boundary takes on the order of hours compared to weeks or longer for larger scale experimental setups. Next, propagation rates of carbon dioxide hydrate were measured in the channels at low subcoolings (<2 K from phase boundary) and moderate pressures (200-500 psi). Growth was dominated by mass transfer limitations until a critical pressure was reached, and reaction kinetics limited growth upon further increases in pressure. Additionally, hydrate conversion was estimated from Raman spectroscopy in the microfluidics channels. A maximum value of 47% conversion was reached within 1 h of a constant flow experiment, nearly 4% of the time required for similar results in a large scale system. The rapid reaction times and high throughput allowed by high pressure microfluidics provide a new way for carbon dioxide gas hydrate to be characterized.

Antioxidant treatment after injury suppresses second hit immune priming.

BACKGROUND: Pulmonary contusion (PC) is a common injury that often results in priming for exaggerated inflammatory responses to a second hit. Previous studies used a mouse model of pulmonary contusion and showed an early and sustained reduction of SIRT1 protein and activity in the lung and bronchoalveolar lavage (BAL) cells of injured mice. Sustained decrease in SIRT1 was associated with a primed phenotype in injured mice challenged with an inflammatory stimulus. This study tests the hypothesis that pulmonary contusion induces oxidant production that modifies and decreases SIRT1 and primes the lung for the second-hit response. METHODS: A mouse model of pulmonary contusion was used to investigate injury-induced oxidant changes in SIRT1. Second-hit responses were evaluated by infection (Streptococcus pneumoniae) and inflammatory challenge using bacterial lipopolysaccharide. BAL, lung tissue, and blood were collected and used to evaluate inflammatory responses and SIRT1 levels, oxidant modification, and activity. Levels of NO in the BAL from mice and patients with PC were also assessed. RESULTS: We found that oxidants produced as a result of pulmonary contusion resulted in modification of SIRT1. S-Nitrosylation was observed and correlated with increased inducible nitric oxide synthase expression after injury. Anti-oxidant treatment of injured mice preserved SIRT1 activity, decreased second hit responses and improved lung function. Elevated NO levels in the BAL of PC patients was associated with acute respiratory distress syndrome or diagnosis of pneumonia. CONCLUSIONS: We conclude that oxidative stress in the lung after injury induces redox modification of SIRT1 and contributes to priming of the lung for a second-hit response. Antioxidant treatment suggests that SIRT1 activity after injury may be beneficial in suppressing second-hit responses.

SIRT1 mediates a primed response to immune challenge after traumatic lung injury.

BACKGROUND: Pulmonary contusion (PC) is a common, potentially lethal injury that results in priming for exaggerated inflammatory responses to subsequent immune challenge like infection (second hit). The molecular mechanism of priming and the second hit phenomenon after PC remain obscure. With the use of a mouse model of PC, this study explores the role of sirtuin 1 (SIRT1), an NAD+-dependent deacetylase, in priming for a second hit after injury. METHODS: With the use of a mouse model of PC, injury-primed second-hit host responses were tested at 24 hours after PC by (1) in vivo infectious challenge of injured mice or (2) ex vivo inflammatory challenge of isolated immune cells from injured mice. SIRT activators or repressors were used to test for SIRT1 participation in these second-hit responses. RESULTS: PC-injured mice given an in vivo infectious challenge by cecal ligation and puncture (CLP) had significantly increased mortality compared with injury or infectious challenge alone. Isolated bronchoalveolar lavage (BAL) cells from injured mice given an ex vivo inflammatory challenge with bacterial lipopolysaccharide (LPS) had increased levels of tumor necrosis factor α messenger RNA compared with uninjured mice. We found that PC reduced SIRT1 protein, messenger RNA, and SIRT1 enzymatic activity in injured lung tissue. We also found decreased SIRT1 protein levels in BAL cells from injured mice. We further found that injured mice treated with a SIRT1 activator, resveratrol, showed significantly decreased polymorphonuclear leukocytes (PMN) in the BAL in response to intratracheal LPS and increased survival from CLP. CONCLUSION: These results showed that PC decreased SIRT1 levels in the lung correlated with enhanced responses to infectious or inflammatory stimuli in injured mice. Treatment of injured mice with a SIRT1 activator, resveratrol, decreased LPS inflammatory response and increased survival after CLP. Our results suggest that SIRT1 participates in the second-hit response after injury.

Complement mediates a primed inflammatory response after traumatic lung injury.

BACKGROUND: Pulmonary contusion (PC) is a common, potentially lethal injury that results in the priming for exaggerated responses to subsequent immune challenge such as an infection (second hit). We hypothesize a PC-induced complement (C) activation participates in the priming effect for a second hit. METHODS: Male, 8 weeks to 9 weeks, C57BL/6 mice (wild-type, C5) underwent blunt chest trauma resulting in PC. At 3 hours/24 hours after injury, the inflammatory response was measured in tissue, serum, and bronchoalveolar lavage (BAL). The thrombin inhibitor, hirudin, was used to determine if injury-induced thrombin participated in the activation of C. Injury-primed responses were tested by challenging injured mice with bacterial endotoxin (lipopolysaccharide, LPS) as a second hit. Inflammatory responses were assessed at 4 hours after LPS challenge. Data were analyzed using one-way analysis of variance with Bonferroni multiple comparison posttest (significance, p ≤ 0.05). Protocols were approved by the Institutional Animal Care and Use Committee. RESULTS: We found significantly increased levels of C5a in the BAL of injured animals as early as 24 hours, persisting for up to 72 hours after injury. Hirudin-treated injured mice had significantly decreased levels of thrombin in the BAL that correlated with reduced C5a levels. Injured mice challenged with intratracheal (IT) LPS had increased C5a and inflammatory response. Conversely, inhibition of C5a or its receptor, C5aR, before LPS challenge correlated with decreased inflammatory responses; C5a-deficient mice showed a similar loss of primed response to LPS challenge. CONCLUSION: Complement C5a levels in the BAL are increased over several days after PC. Premorbid inhibition of thrombin markedly decreases C5a levels after PC, suggesting that thrombin-induced C activation is the major pathway of activation after PC. Similarly, inhibition of C5a after PC will decrease injury-primed responses to LPS stimulation. Our findings suggest cross-talk between the coagulation and complement systems that induce immune priming after PC.

Innate immune response to pulmonary contusion: identification of cell type-specific inflammatory responses.

Lung injury from pulmonary contusion is a common traumatic injury, predominantly seen after blunt chest trauma, such as in vehicular accidents. The local and systemic inflammatory response to injury includes activation of innate immune receptors, elaboration of a variety of inflammatory mediators, and recruitment of inflammatory cells to the injured lung. Using a mouse model of pulmonary contusion, we had previously shown that innate immune Toll-like receptors 2 and 4 (TLR2 and TLR4) mediate the inflammatory response to lung injury. In this study, we used chimeric mice generated by adoptive bone marrow transfer between TLR2 or TLR4 and wild-type mice. We found that, in the lung, both bone marrow-derived and nonmyeloid cells contribute to TLR-dependent inflammatory responses after injury in a cell type-specific manner. We also show a novel TLR2-dependent injury mechanism that is associated with enhanced airway epithelial cell apoptosis and increased pulmonary FasL and Fas expression in the lungs from injured mice. Thus, in addition to cardiopulmonary physiological dysfunction, cell type-specific TLR and their differential response to injury may provide novel specific targets for management of patients with pulmonary contusion.

Mechanism of neutrophil recruitment to the lung after pulmonary contusion.

Blunt chest trauma resulting in pulmonary contusion is a common but poorly understood injury. We previously demonstrated that lung contusion activates localized and systemic innate immune mechanisms and recruits neutrophils to the injured lung. We hypothesized that the innate immune and inflammatory activation of neutrophils may figure prominently in the response to lung injury. To investigate this, we used a model of pulmonary contusion in the mouse that is similar to that observed clinically in humans and evaluated postinjury lung function and pulmonary neutrophil recruitment. Comparisons were made between injured mice with and without neutrophil depletion. We further examined the role of chemokines and adhesion receptors in neutrophil recruitment to the injured lung. We found that lung injury and resultant physiological dysfunction after contusion were dependent on the presence of neutrophils in the alveolar space. We show that CXCL1, CXCL2/3, and CXCR2 are involved in neutrophil recruitment to the lung after injury and that intercellular adhesion molecule 1 is locally expressed and actively participates in this process. Injured gp91-deficient mice showed improved lung function, indicating that oxidant production by neutrophil NADPH oxidase mediates lung dysfunction after contusion. These data suggest that both neutrophil presence and function are required for lung injury after lung contusion.

Pulmonary contusion primes systemic innate immunity responses.

INTRODUCTION: Traumatic injury may result in an exaggerated response to subsequent immune stimuli such as nosocomial infection. This "second hit" phenomenon and molecular mechanism(s) of immune priming by traumatic lung injury, specifically, pulmonary contusion, remain unknown. We used an animal model of pulmonary contusion to determine whether the injury resulted in priming of the innate immune response and to test the hypothesis that resuscitation fluids could attenuate the primed response to a second hit. METHODS: Male, 8 to 9 weeks, C57/BL6 mice with a pulmonary contusion were challenged by a second hit of intratracheal administration of the Toll-like receptor 4 agonist, lipopolysaccharide (LPS, 50 microg) 24 hours after injury (injury + LPS). Other experimental groups were injury + vehicle or LPS alone. A separate group was injured and resuscitated by 4 cc/kg of hypertonic saline (HTS) or Lactated Ringer's (LR) resuscitation before LPS challenge. Mice were killed 4 hours after LPS challenge and blood, bronchoalveolar lavage, and tissue were isolated and analyzed. Data were analyzed using one-way analysis of variance with Bonferroni multiple comparison posttest for significant differences (*p < or = 0.05). RESULTS: Injury + LPS showed immune priming observed by lung injury histology and increased bronchoalveolar lavage neutrophilia, lung myeloperoxidase and serum IL-6, CXCL1, and MIP-2 levels when compared with injury + vehicle or LPS alone. After injury, resuscitation with HTS, but not Lactated Ringer's was more effective in attenuating the primed response to a second hit. CONCLUSION: Pulmonary contusion primes innate immunity for an exaggerated response to a second hit with the Toll-like receptor 4 agonist, LPS. We observed synergistic increases in inflammatory mediator expression in the blood and a more severe lung injury in injured animals challenged with LPS. This priming effect was reduced when HTS was used to resuscitate the animal after lung contusion.

Toll-like receptor 4-dependent responses to lung injury in a murine model of pulmonary contusion.

Blunt chest trauma resulting in pulmonary contusion with an accompanying acute inflammatory response is a common but poorly understood injury. We previously demonstrated that toll-like receptor 2 (TLR-2) participates in the inflammatory response to lung injury. We hypothesized that the TLR-4, in an MyD88-dependent manner, may also participate in the response to lung injury. To investigate this, we used a model of pulmonary contusion in the mouse that is similar to that observed clinically in humans and evaluated postinjury lung function, pulmonary neutrophil recruitment, and the systemic innate immune response. Comparisons were made between wild-type mice and mice deficient in TLR-4 or MyD88. We found TLR-4-dependent responses to pulmonary contusion that include hypoxemia, edema, and neutrophil infiltration. Increased expression of IL-6 and chemokine (C-X-C motif) ligand 1 in the bronchoalveolar lavage and serum was also dependent on TLR-4 activation. We further demonstrated that these responses to pulmonary contusion were dependent on MyD88, an adapter protein in the signal transduction pathway mediated by TLRs. These results show that TLRs have a primary role in the response to acute lung injury. Lung inflammation and systemic innate immune responses are dependent on TLR activation by pulmonary contusion.