Intratracheal administration of perfluorochemical-gentamicin suspension: a comparison to intravenous administration in normal and injured lungs

Perfluorocarbons in Research and Clinical Practice: A Narrative Review

Perfluorocarbons (PFCs) are organic liquids derived from hydrocarbons in which some of the hydrogen atoms have been replaced by fluorine atoms. They are chemically and biologically inert substances with a good safety profile. They are stable at room temperature, easy to store, and immiscible in water. Perfluorocarbons have been studied in biomedical research since 1960 for their unique properties as oxygen carriers. In particular, PFCs have been used for liquid ventilation in unusual environments such as deep-sea diving and simulations of zero gravity, and more recently for drug delivery and diagnostic imaging. Additionally, when delivered as emulsions, PFCs have been used as red blood cell substitutes. This narrative review will discuss the multifaceted utilization of PFCs in therapeutics, diagnostics, and research. We will specifically emphasize the potential role of PFCs as red blood cell substitutes, as airway mechanotransducers during artificial placenta procedures, as a means to improve donor organ perfusion during the ex vivo assessment, and as an adjunct in cancer therapies because of their ability to reduce local tissue hypoxia.

Targeted delivery of inhalable drug particles in a patient-specific tracheobronchial tree with moderate COVID-19: A numerical study

The coronavirus disease 2019 (COVID-19) pandemic has led to severe social and economic disruption worldwide. Although currently no consent has been reached on a specific therapy that can treat COVID-19 effectively, several inhalation therapy strategies have been proposed to inhibit SARS-CoV-2 infection. These strategies include inhalations of antiviral drugs, anti-inflammatory drugs, and vaccines. To investigate how to enhance the therapeutic effect by increasing the delivery efficiency (DE) of the inhaled aerosolized drug particles, a patient-specific tracheobronchial (TB) tree from the trachea up to generation 6 (G6) with moderate COVID-19 symptoms was selected as a testbed for the in silico trials of targeted drug delivery to the lung regions with pneumonia alba, i.e., the severely affected lung segments (SALS). The 3D TB tree geometry was reconstructed from spiral computed tomography (CT) scanned images. The airflow field and particle trajectories were solved using a computational fluid dynamics (CFD) based Euler-Lagrange model at an inhalation flow rate of 15 L/min. Particle release maps, which record the deposition locations of the released particles, were obtained at the inlet according to the particle trajectories. Simulation results show that particles with different diameters have similar release maps for targeted delivery to SALS. Point-source aerosol release (PSAR) method can significantly enhance the DE into the SALS. A C++ program has been developed to optimize the location of the PSAR tube. The optimized simulations indicate that the PSAR approach can at least increase the DE of the SALS by a factor of 3.2× higher than conventional random-release drug-aerosol inhalation. The presence of the PSAR tube only leads to a 7.12% change in DE of the SALS. This enables the fast design of a patient-specific treatment for reginal lung diseases.

Administration of Drugs/Gene Products to the Respiratory System: A Historical Perspective of the Use of Inert Liquids

The present review is a historical perspective of methodology and applications using inert liquids for respiratory support and as a vehicle to deliver biological agents to the respiratory system. As such, the background of using oxygenated inert liquids (considered a drug when used in the lungs) opposed to an oxygen-nitrogen gas mixture for respiratory support is presented. The properties of these inert liquids and the mechanisms of gas exchange and lung function alterations using this technology are described. In addition, published preclinical and clinical trial results are discussed with respect to treatment modalities for respiratory diseases. Finally, this forward-looking review provides a comprehensive overview of potential methods for administration of drugs/gene products to the respiratory system and potential biomedical applications.

Perfluorochemical-facilitated plasminogen activator delivery to the airways: A novel treatment for inhalational smoke-induced acute lung injury

BACKGROUND

Effective clinical management of airway clot and fibrinous cast formation of severe inhalational smoke-induced acute lung injury (ISALI) is lacking. Aerosolized delivery of tissue plasminogen activator (tPA) is confounded by airway bleeding; single-chain urokinase plasminogen activator (scuPA) moderated this adverse effect and supported transient improvement in gas exchange and lung mechanics. However, neither aerosolized plasminogen activator (PA) yielded durable improvements in physiologic responses or reduction in cast burden. Here, we hypothesized that perfluorochemical (PFC) liquids would facilitate PA distribution and sustain improvements in physiologic outcomes in ISALI.

METHODS

Spontaneously breathing adult sheep (n = 36) received anesthesia and analgesia and were instrumented, exposed to cotton smoke inhalation, and supported by mechanical ventilation for 48 h. Groups (n = 6/group) were studied without supplemental treatment, or, starting 4 h post injury, they received intratracheal low volume (8 mL) PFC liquid alone or a dose range of tPA/PFC or scuPA/PFC suspensions (4 or 8 mg in 8 mL PFC) every 8 h. Outcomes were evaluated by sequential measurements of cardiopulmonary parameters, lung histomorphology, and biochemical analyses of bronchoalveolar lavage fluid.

RESULTS

Dose-response and PA-type comparisons of outcomes demonstrated sustained superiority with low-volume PFC suspensions of scuPA over tPA or PFC alone, favoring the highest dose of scuPA/PFC suspension over lower doses, without airway bleeding.

CONCLUSIONS

We propose that this improved profile over previously reported aerosolized delivery is likely related to improved dose distribution. Sustained salutary responses to scuPA/PFC suspension delivery in this translational model are encouraging and support the possibility that the observed outcomes could be of clinical importance.

Targeted delivery of liquid microvolumes into the lung

The ability to deliver drugs to specific sites in the lung could radically improve therapeutic outcomes of a variety of lung diseases, including cystic fibrosis, severe bronchopneumonia, chronic obstructive pulmonary disease, and lung cancer. Using conventional methods for pulmonary drug administration, precise, localized delivery of exact doses of drugs to target regions remains challenging. Here we describe a more controlled delivery of soluble reagents (e.g., drugs, enzymes, and radionuclides) in microvolume liquid plugs to targeted branches of the pulmonary airway tree: upper airways, small airways (bronchioles), or the most distal alveoli. In this approach, a soluble liquid plug of very small volume (<1 mL) is instilled into the upper airways, and with programmed air ventilation of the lungs, the plug is pushed into a specific desired (more distal) airway to achieve deposition of liquid film onto the lung epithelium. The plug volume and ventilation conditions were determined by mathematical modeling of plug transport in a tubular geometry, and targeted liquid film deposition was demonstrated in rat lungs by three different in vivo imaging modalities. The experimental and modeling data suggest that instillation of microvolumes of liquid into a ventilated pulmonary airway could be an effective strategy to deliver exact doses of drugs to targeted pathologic regions of the lung, especially those inaccessible by bronchoscopy, to increase in situ efficacy of the drug and minimize systemic side effects.

Characterization of a reverse-phase perfluorocarbon emulsion for the pulmonary delivery of tobramycin

BACKGROUND

Aerosolized delivery of antibiotics is hindered by poor penetration within distal and plugged airways. Antibacterial perfluorocarbon ventilation (APV) is a proposed solution in which the lungs are partially or totally filled with perfluorocarbon (PFC) containing emulsified antibiotics. The purpose of this study was to evaluate emulsion stability and rheological, antibacterial, and pharmacokinetic characteristics.

METHODS

This study examined emulsion aqueous droplet diameter and number density over 24 hr and emulsion and neat PFC viscosity and surface tension. Additionally, Pseudomonas aeruginosa biofilm growth was measured after 2-hr exposure to emulsion with variable aqueous volume percentages (0.25, 1, and 2.5%) and aqueous tobramycin concentrations (Ca=0.4, 4, and 40 mg/mL). Lastly, the time course of serum and pulmonary tobramycin concentrations was evaluated following APV and conventional aerosolized delivery of tobramycin in rats.

RESULTS

The initial aqueous droplet diameter averaged 1.9±0.2 μm with little change over time. Initial aqueous droplet number density averaged 3.5±1.7×10(9) droplets/mL with a significant (p<0.01) decrease over time. Emulsion and PFC viscosity were not significantly different, averaging 1.22±0.03×10(-3) Pa·sec. The surface tensions of PFC and emulsion were 15.0±0.1×10(-3) and 14.6±0.6×10(-3) N/m, respectively, and the aqueous interfacial tensions were 46.7±0.3×10(-3) and 26.9±11.0×10(-3) N/m (p<0.01), respectively. Biofilm growth decreased markedly with increasing Ca and, to a lesser extent, aqueous volume percentage. Tobramycin delivered via APV yielded 2.5 and 10 times larger pulmonary concentrations at 1 and 4 hr post delivery, respectively, and significantly (p<0.05) lower serum concentrations compared with aerosolized delivery.

CONCLUSIONS

The emulsion is bactericidal, retains the rheology necessary for pulmonary delivery, is sufficiently stable for this application, and results in increased pulmonary retention of the antibiotic.

Efficacy of intratracheal instillation of a meropenem/perfluorochemical suspension in acute lung injury

Perfluorochemical (PFC) is theoretically a good vehicle for delivering biological agents to the lungs. This study was designed to investigate the efficacy of intratracheal (IT) instillation of meropenem using PFC liquid as a vehicle in a piglet model of acute lung injury (ALI). Eighteen piglets were injured with lung lavages to induce ALI, and randomly assigned to intravenous (IV) infusion or IT instillation groups, the latter using either PFC or normal saline (NS) as a delivery vehicle for meropenem. Blood samples were obtained at 0, 15, 30, and 60 min, and then hourly for 6 hr. Sera and extracts of lung tissues were assayed for meropenem content using high-performance liquid chromatography. We found that the IV group had significantly higher serum concentrations of meropenem during the first hour after dosing (P < 0.05). There was no significant difference between IT-PFC and IT-NS groups regarding changes in serum meropenem concentrations during the experimental period. Meropenem content in lung tissue was highest in the IT-PFC group, lower in the IT-NS group, and undetectable in the IV group (P < 0.05). The IT-NS group had the highest peak inspiratory pressure (P < 0.05), but there were no significant differences in other cardiopulmonary parameters among the three groups studied. In conclusion, meropenem can be safely administered to injured lungs by IT instillation in a meropenem/PFC suspension. Using PFC liquid as an IT vehicle to carry meropenem provides better pulmonary drug depositions than IV injection or IT instillation with NS in ALI.

Perfluorochemical liquid-adenovirus suspensions enhance gene delivery to the distal lung

WE COMPARED LUNG DELIVERY METHODS OF RECOMBINANT ADENOVIRUS (RAD): (1) rAd suspended in saline, (2) rAd suspended in saline followed by a pulse-chase of a perfluorochemical (PFC) liquid mixture, and (3) a PFC-rAd suspension. Cell uptake, distribution, and temporal expression of rAd were examined using A549 cells, a murine model using luciferase bioluminescence, and histological analyses. Relative to saline, a 4X increase in transduction efficiency was observed in A549 cells exposed to PFC-rAd for 2-4 h. rAd transgene expression was improved in alveolar epithelial cells, and the level and distribution of luciferase expression when delivered in PFC-rAd suspensions consistently peaked at 24 h. These results demonstrate that PFC-rAd suspensions improve distribution and enhance rAd-mediated gene expression which has important implications in improving lung function by gene therapy.

Semi-fluorinated alkanes as carriers for drug targeting in acute respiratory failure

Partial liquid ventilation (PLV) with perfluorocarbons may cause pulmonary recruitment in acute lung injury (ALI). Semi-fluorinated alkanes (SFAs) provide biochemical properties similar to perfluorocarbons. Additionally, SFAs are characterized by increased lipophilicity. Therefore, SFA-PLV may be considered for deposition of certain therapeutic drugs into atelectatic lung areas. In this experimental study SFA-PLV was evaluated to demonstrate feasibility, pulmonary recruitment, and efficacy of drug deposition. Feasibility of SFA-PLV was determined in pigs with and without experimental ALI. Animals were randomized to PLV with SFAs up to a cumulative amount of 30 mL x kg⁻¹ or to conventional mechanical ventilation. Pulmonary recruitment effects were determined by analyzing ventilation-perfusion distributions. Efficacy of intrapulmonary drug deposition was evaluated in further experiments by measuring drug serum concentrations in the course of PLV with SFA-dissolved α-tocopherol and ibuprofen. Increasing SFA doses caused progressive reduction of intrapulmonary shunt in animals with ALI, indicating pulmonary recruitment. PLV with SFA-dissolved α-tocopherol had no effect on serum levels of α-tocopherol, whereas PLV with SFA-dissolved ibuprofen caused a rapid increase of serum levels of ibuprofen. The authors conclude that SFA-PLV is feasible and causes pulmonary recruitment in ALI. Effectiveness of drug deposition in the lung obviously depends on the partitioning drugs out of the SFA phase into blood.

Perflubron reduces lung inflammation in respiratory syncytial virus infection by inhibiting chemokine expression and nuclear factor-kappa B activation

Airway mucosa inflammation plays a critical role in the pathogenesis of lower respiratory tract infections caused by respiratory syncytial virus (RSV), the major etiologic agent of bronchiolitis in infancy. Type and intensity of cellular infiltration are dictated by inflammatory chemokines, which are rapidly and abundantly induced in lung tissue by RSV. This process is, to a large extent, transcriptionally regulated by RSV-mediated activation of the nuclear factor-kappa B. The administration of a perfluorocarbon (PFC) liquid, such as perflubron, during partial liquid ventilation improves lung function and also reduces inflammation. In this study we demonstrate that treatment of BALB/c mice with perflubron intranasally 6 hours after RSV infection significantly inhibited lung cellular inflammation as well as the expression of the chemokines RANTES, MIP-1 alpha, MIP-1 beta, and MIP-2, compared with phosphate-buffered saline-treated control mice. However, perflubron treatment did not affect RSV replication. Strikingly, treatment with perflubron abrogated nuclear factor-kappa B activation in lung of RSV-infected mice. These results demonstrate a novel mechanism by which PFC may exert antiinflammatory activity and suggest that partial liquid ventilation with PFC may be considered in future clinical trials for infants with severe RSV infections requiring mechanical ventilation.