open-tracheostomy-gastric-acid-aspiration-murine-model-acute-lung

Open Tracheostomy Gastric Acid Aspiration Murine Model of Acute Lung Injury Results in Maximal Acute Nonlethal Lung Injury

Acid pneumonitis is a major cause of sterile acute lung injury (ALI) in humans. Acid pneumonitis spans the clinical spectrum from asymptomatic to acute ...

University at Buffalo, State University of New York

Large (>6 microm) rigid microparticles (MPs) become passively entrapped within the lungs after intravenous (i.v.) injection making them an attractive and highly efficient alternative to inhalation for pulmonary delivery. In this study, PEGylated 6 microm polystyrene MPs with multiple copies of the norvaline (Nva) alpha-amino acid prodrug of camptothecin (CPT) were prepared. Surface morphology was characterized using a scanning electron microscope. CPT was released from the CPT-Nva-MPs over 24 h in rat plasma at 37 degrees C. In-vivo CPT plasma concentrations were low (approximately 1 ng/ml or less) and constant over a period of 4 days after a single i.v. injection of CPT-Nva-MPs as compared with high but short-lived systemic exposures after an i.v. injection of free CPT. This suggests that sustained local CPT concentrations were achieved in the lung after administration of the MP delivery system. Anticancer efficacy was evaluated in an orthotopic lung cancer animal model and compared with a bolus injection of CPT. Animals receiving free CPT (2 mg/kg) and CPT-Nva-MPs (0.22 mg/kg CPT and 100 mg/kg MPs) were found to have statistically significant smaller areas of lung cancer (P<0.05 and 0.01, respectively) than untreated animals. In addition, 40% of the animals receiving CPT-Nva-MPs were found to be free of cancer. The CPT dose using targeted MPs was 10 times lower than after i.v. injection of free CPT, but was more effective in reducing the amount of cancerous areas. In conclusion, CPT-Nva-MPs were able to achieve effective local lung and low systemic CPT concentrations at a dose that was 10 times lower than systemically administered CPT resulting in a significant improvement in anticancer efficacy in an orthotopic rat model of lung cancer.

Pulmonary targeting microparticulate camptothecin delivery system: anticancer evaluation in a rat orthotopic lung cancer model.

The relationship between microparticle (MP) size and lung targeting efficiency, intra-lung distribution and retention time was systematically studied after intravenous administration of rigid fluorescent polystyrene MPs of various sizes (2, 3, 6 and 10 microm) to Sprague Dawley rats. Total fluorescence was assessed and it was found that 2 microm and 3 microm MPs readily passed through the lung to the liver and spleen while 10 microm MPs were completely entrapped in the lung for the one-week duration of the study. Approximately 84% of 6 microm MPs that were initially entrapped in the lung were cleared over the next 2 days and 15% were cleared over the remaining 5 days. A Caliper IVIS 100 small animal imaging system confirmed that 3 microm MPs were not retained in the lung but that 6 microm and 10 microm MPs were widely distributed throughout the lung. Moreover, histologic examination showed MP entrapment in capillaries but not arterioles. These studies suggest that for rigid MPs the optimal size range required to achieve transient but highly efficiently targeting to pulmonary capillaries after IV injection is >6 microm but <10 microm in rats and that systemic administration of optimally sized MPs may be an efficient alternative to currently used inhalation-based delivery to the lung.

Threshold size for optimal passive pulmonary targeting and retention of rigid microparticles in rats.

The objective of the present study was to identify a camptothecin (CPT) prodrug with optimal release and cytotoxicity properties for immobilization on a passively targeted microparticle delivery system. A series of alpha-amino acid ester prodrugs of CPT were synthesized, characterized, and evaluated. Four CPT prodrugs were synthesized with increasing aliphatic chain length (glycine (Gly) (2a), alanine (Ala) (2b), aminobutyric acid (Abu) (2c), and norvaline (Nva) (2d)). Prodrug reconversion was studied at pH 6.6, 7.0, and 7.4 corresponding to tumor, lung, and extracellular/physiological pH, respectively. Cytotoxicity was evaluated in A549 human lung carcinoma cells using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The hydrolytic reconversion rate to parent CPT increased with decreasing side chain length as well as increasing pH. The Hill slope of 2d was significantly less than CPT and the other prodrugs tested, indicating a higher cell death rate at lower concentrations. These results suggest that 2d is the best candidate for a passively targeted sustained release lung delivery system.

A series of alpha-amino acid ester prodrugs of camptothecin: in vitro hydrolysis and A549 human lung carcinoma cell cytotoxicity.

The current study examines the passive pulmonary targeting efficacy and retention of 6μm polystyrene (PS) microparticles (MPs) covalently modified with different surface groups [amine (A-), carboxyl (C-) and sulfate (S-)] or single (PEG(1)-) and double (PEG(2)-) layers of α,ω-diamino poly(ethylene glycol) attached to C-MPs. The ζ-potential of A-MPs (-44.0mV), C-MPs (-54.3mV) and S-MPs (-49.6mV) in deionized water were similar; however PEGylation increased the ζ-potential for both PEG(1)-MPs (-18.3mV) and PEG(2)-MPs (11.5mV). The biodistribution and retention of intravenously administered MPs to male Sprague-Dawley rats was determined in homogenized tissue by fluorescence spectrophotometry. PEG(1)-MPs and PEG(2)-MPs demonstrated enhanced pulmonary retention in rats at 48h after injection when compared to unmodified A-MPs (59.6%, 35.9% and 17.0% of the administered dose, respectively). While unmodified MPs did not significantly differ in lung retention, PEGylation of MPs unexpectedly improved passive lung targeting and retention by modifying surface properties including charge and hydrophobicity but not size.

Enhanced passive pulmonary targeting and retention of PEGylated rigid microparticles in rats.

A novel stabilized aggregated nanogel particle (SANP) drug delivery system was prepared for injectable passive lung targeting. Gel nanoparticles (GNPs) were synthesized by irreversibly cross-linking 8 Arm PEG thiol with 1,6-hexane-bis-vinylsulfone (HBVS) in phosphate buffer (PB, pH 7.4) containing 0.1% v/v Tween™ 80. Aggregated nanogel particles (ANPs) were generated by aggregating GNPs to micron-size, which were then stabilized (i.e., SANPs) using a PEG thiol polymer to prevent further growth-aggregation. The size of SANPs, ANPs and GNPs was analyzed using a Coulter counter and transmission electron microscopy (TEM). Stability studies of SANPs were performed at 37°C in rat plasma, phosphate buffered saline (PBS, pH 7.4) and PB (pH 7.4). SANPs were stable in rat plasma, PBS and PB over 7 days. SANPs were covalently labeled with HiLyte Fluor™ 750 (DYE-SANPs) to facilitate ex vivo imaging. Biodistribution of intravenous DYE-SANPs (30 μm, 4 mg in 500 μL PBS) in male Sprague-Dawley rats was compared to free HiLyte Fluor™ 750 DYE alone (1mg in 500 μL PBS) and determined using a Xenogen IVIS® 100 Imaging System. Biodistribution studies demonstrated that free DYE was rapidly eliminated from the body by renal filtration, whereas DYE-SANPs accumulated in the lung within 30 min and persisted for 48 h. DYE-SANPs were enzymatically degraded to their original principle components (i.e., DYE-PEG-thiol and PEG-VS polymer) and were then eliminated from the body by renal filtration. Histological evaluation using H & E staining and broncho alveolar lavage (BAL) confirmed that these flexible SANPs were not toxic. This suggests that because of their flexible and non-toxic nature, SANPs may be a useful alternative for treating pulmonary diseases such as asthma, pneumonia, tuberculosis and disseminated lung cancer.

Biodistribution and renal clearance of biocompatible lung targeted poly(ethylene glycol) (PEG) nanogel aggregates.

Poly(lactic-co-glycolic acid) (PLGA) chitosan (CS) coated nanoparticles (NPs) were loaded with two antiretrovirals (ARVs) either lamivudine (LMV) which is hydrophilic or nevirapine (NVP) which is hydrophobic or both LMV and NVP. These ARVs are of importance in resource-limited settings, where they are commonly used in human immunodeficiency virus (HIV-1) treatment due to affordability and accessibility. NPs prepared by a water-oil-water emulsion and reduced pressure solvent evaporation technique were determined to have a positive zeta potential, a capsule-like morphology, and an average hydrodynamic diameter of 240 nm. Entrapment of NVP as a single ARV had a notable increase in NP size compared to LMV alone or in combination with LMV. NPs stored at room temperature in distilled water maintained size, polydispersity (PDI), and zeta potential for one year. No changes in size, PDI, and zeta potential were observed for NPs in 10% sucrose in lyophilized or nonlyophilized states stored at 4°C and -20°C, respectively. Freezing NPs in the absence of sucrose increased NP size. Drug loading, encapsulation efficiency, and kinetic release profiles were quantified by high performance liquid chromatography (HPLC). Our novel nanoformulations have the potential to improve patient outcomes and expand drug access in resource-limited countries for the treatment of HIV-1.

Poly(lactic-co-glycolic) Acid-Chitosan Dual Loaded Nanoparticles for Antiretroviral Nanoformulations.

We introduce a hybrid organic-inorganic system consisting of epitaxial NaYF4:Yb(3+)/X(3+)@NaYbF4@NaYF4:Nd(3+) (X = null, Er, Ho, Tm, or Pr) core/shell/shell (CSS) nanocrystal with organic dye, indocyanine green (ICG) on the nanocrystal surface. This system is able to produce a set of narrow band emissions with a large Stokes-shift (>200 nm) in the second biological window of optical transparency (NIR-II, 1000-1700 nm), by directional energy transfer from light-harvesting surface ICG, via lanthanide ions in the shells, to the emitter X(3+) in the core. Surface ICG not only increases the NIR-II emission intensity of inorganic CSS nanocrystals by ∼4-fold but also provides a broadly excitable spectral range (700-860 nm) that facilitates their use in bioapplications. We show that the NIR-II emission from ICG-sensitized Er(3+)-doped CSS nanocrystals allows clear observation of a sharp image through 9 mm thick chicken breast tissue, and emission signal detection through 22 mm thick tissue yielding a better imaging profile than from typically used Yb/Tm-codoped upconverting nanocrystals imaged in the NIR-I region (700-950 nm). Our result on in vivo imaging suggests that these ICG-sensitized CSS nanocrystals are suitable for deep optical imaging in the NIR-II region.

Hilliard L. Kutscher

Institute of Lasers,
Photonics and Biophotonics,
Institute of Lasers, Photonics and Biophotonics

University at Buffalo, State University of New York

Open Tracheostomy Gastric Acid Aspiration Murine Model of Acute Lung Injury Results in Maximal Acute Nonlethal Lung Injury

Hilliard L. Kutscher

Institute of Lasers,Photonics and Biophotonics,Institute of Lasers, Photonics and Biophotonics

University at Buffalo, State University of New York

Open Tracheostomy Gastric Acid Aspiration Murine Model of Acute Lung Injury Results in Maximal Acute Nonlethal Lung Injury

Institute of Lasers,
Photonics and Biophotonics,
Institute of Lasers, Photonics and Biophotonics