Pressure-sensitive multivesicular liposomes as a smart drug-delivery system for high-altitude pulmonary edema.

Changes in bodily fluid pressures, such as pulmonary artery pressure, play key roles in high-altitude pulmonary edema (HAPE) and other disorders. Smart delivery systems releasing a drug in response to these pressures might facilitate early medical interventions. However, pressure-responsive delivery systems are unavailable. We here constructed hydrostatic pressure-sensitive multivesicular liposomes (PSMVLs) based on the incomplete filling of the internal vesicle space with neutral lipids. These liposomes were loaded with amlodipine besylate (AB), a next-generation calcium channel inhibitor, to treat HAPE on time. AB-loaded PSMVLs (AB-PSMVLs) were destroyed, and AB was released through treatment under hydrostatic pressure of at least 25 mmHg. At 25 mmHg, which is the minimum pulmonary artery pressure value in HAPE, 38.8% of AB was released within 1 h. In a mouse HAPE model, AB-PSMVLs concentrated in the lung and released AB to diffuse into the vascular wall. Intravenously injected AB-PSMVLs before HAPE modeling resulted in a stronger protection of lung tissues and respiratory function and lower occurrence of pulmonary edema than treatment with free drug or non-pressure-sensitive AB-loaded liposomes. This study offers a new strategy for developing smart drug delivery systems that respond to changes in bodily fluid pressures.

Dry Powder Formulations for Inhalation Require a Smaller Aerodynamic Diameter for Usage at High Altitude.

BACKGROUND: High Altitude Pulmonary Edema (HAPE) seriously threatens the health of people at high altitudes. There are drug treatments for HAPE, and dry powder formulations (DPFs) represent a rapid and accessible delivery vehicle for these drugs. However, there are presently no reports on the inhalability of DPFs in low-pressure environments. Given the reduced atmospheric pressure typical at high altitudes, conventional DPFs might not be suitable for inhalation. Therefore, it is necessary to elucidate the deposition behaviors of dry powder in the respiratory tract at low pressure, as well as to improve their pulmonary deposition efficiency via adjustments to their formulation and design. METHODS: The effect of air pressure, inspiratory velocity, and particle properties (such as size, density, and aerodynamic diameter) on pulmonary deposition of DPFs was calculated by a computational fluid dynamics (CFD)-coupled discrete phase model. DPFs of various aerodynamic diameters were prepared by spray drying, and the inhalability of these DPFs in a low-pressure environment was evaluated in mice. Finally, a mouse model of HAPE was established, and the treatment of HAPE by nifedipine-loaded DPFs with small aerodynamic diameter was validated. RESULTS: CFD results showed that low pressure decreased the deposition of DPFs in the lungs. At 0.5 standard atmosphere, DPFs with aerodynamic diameter of ∼2.0 µm could not enter the lower respiratory tract; however, a decrease in the physical diameter, density, and, consequently, the aerodynamic diameter of the DPFs was able to enhance pulmonary deposition of these powders. To validate the CFD results, three kinds of dry powder with aerodynamic diameters of 0.66, 0.98, and 2.00 µm were prepared by spray drying. Powders with smaller aerodynamic diameter could be inhaled into the lungs of mice more effectively, and, consequently could ameliorate the progression of HAPE more effectively than conventional powders. These results were consistent with the CFD results. CONCLUSIONS: Low atmospheric pressure can prevent the pulmonary deposition of DPFs at high altitudes. Compared with conventional DPFs, powders with smaller aerodynamic diameter can be effectively inhaled at these pressures and thus might be more suitable for the treatment the HAPE.

Re-exposure of chitosan by an inhalable microsphere providing the re-education of TAMs for lung cancer treatment with assistant from sustained H2S generation.

The re-education of tumor-associated macrophages (TAMs) is an effective strategy to inhibit the growth and metastasis of lung cancer. We have reported that chitosan could re-educate the TAMs and then inhibit cancer metastasis; however, the re-exposure of chitosan from the chemical corona on their surface is critical for this effect. In this study, a strategy was proposed to re-expose the chitosan from chemical corona, and a sustained H2S generation was applied to enhance the immunotherapy of chitosan. To achieve this objective, an inhalable microsphere (namely F/Fm) was designed, which could be degraded by the matrix metalloproteinase in lung cancer, releasing two kinds of nanoparticles; in an external magnetic field, these nanoparticles can aggregate with each other, and ß-cyclodextrin on the surface of one nanoparticle can be hydrolyzed by amylase on the surface of another nanoparticle, leading to the re-exposure of chitosan in the inner layer of ß-cyclodextrin and the release of diallyl trisulfide for H2S generation. In vitro, the expression of CD86 and secretion of TNF-α by TAMs was increased by F/Fm, proving the re-education of TAMs, and the apoptosis of A549 cells was promoted with the migration and invasion being inhibited. In the Lewis lung carcinoma-bearing mouse, the F/Fm re-educated the TAMs and provided a sustained generation of H2S in the region of lung cancer, effectively inhibiting the growth and metastasis of lung cancer cells. This work provides a new strategy for the treatment of lung cancer in combination of re-education of TAMs by chitosan and the adjuvant chemotherapy by H2S.

O-carboxymethyl chitosan based pH/hypoxia-responsive micelles relieve hypoxia and induce ROS in tumor microenvironment.

The hypoxia in tumor microenvironment (TME) can upregulate the HIF-1α and PD-L1 expression and cause immunosuppression of tumor. In this study, a carboxymethyl chitosan-based pH/hypoxia-responsive and γ-Fe2O3/isosorbide dinitrate carrying micelle was designed, and it could catalyze endogenous H2O2 to generate oxygen and relieve hypoxia in TME, so as to relieve the overexpression of HIF-1α and PD-L1 in tumor; meanwhile, it could react with H2O2 to release ROS via Fenton reaction and induce cytotoxicity in tumor. Along with these multiple effects, this carboxymethyl chitosan-based micelles could provide a comprehensive strategy for tumor treatment.