Development of a drug delivery system for efficient alveolar delivery of a neutralizing monoclonal antibody to treat pulmonary intoxication to ricin.

The high toxicity of ricin and its ease of production have made it a major bioterrorism threat worldwide. There is however no efficient and approved treatment for poisoning by ricin inhalation, although there have been major improvements in diagnosis and therapeutic strategies. We describe the development of an anti-ricin neutralizing monoclonal antibody (IgG 43RCA-G1) and a device for its rapid and effective delivery into the lungs for an application in humans. The antibody is a full-length IgG and binds to the ricin A-chain subunit with a high affinity (KD=53pM). Local administration of the antibody into the respiratory tract of mice 6h after pulmonary ricin intoxication allowed the rescue of 100% of intoxicated animals. Specific operational constraints and aerosolization stresses, resulting in protein aggregation and loss of activity, were overcome by formulating the drug as a dry-powder that is solubilized extemporaneously in a stabilizing solution to be nebulized. Inhalation studies in mice showed that this formulation of IgG 43RCA-G1 did not induce pulmonary inflammation. A mesh nebulizer was customized to improve IgG 43RCA-G1 deposition into the alveolar region of human lungs, where ricin aerosol particles mostly accumulate. The drug delivery system also comprises a semi-automatic reconstitution system to facilitate its use and a specific holding chamber to maximize aerosol delivery deep into the lung. In vivo studies in monkeys showed that drug delivery with the device resulted in a high concentration of IgG 43RCA-G1 in the airways for at least 6h after local deposition, which is consistent with the therapeutic window and limited passage into the bloodstream.

Comparison of laser diffraction measurements by Mastersizer X and Spraytec to characterize droplet size distribution of medical liquid aerosols.

BACKGROUND: The Mastersizer X (Malvern Instruments) used to be the reference device for assessing droplet size distribution of aerosols by laser diffraction, but it has not been updated and has gradually been replaced by the Spraytec (Malvern Instruments), which is considered to provide greater accuracy and higher acquisition speed. METHODS: The aim of this study was to compare the use of the two diffractometers to characterize medical liquid aerosols in a wide range of droplet sizes, using four nasal sprays to produce large droplets (10-180 µm) and 10 nebulizers to produce smaller droplets (0.5-20 µm). The influence of the inhalation cell provided with the Spraytec on the measurements was also determined. RESULTS: Correlation between the devices was low for large droplets (R(2)=0.37) and high for smaller droplets (R(2)=0.97). The Spraytec overestimated the median diameter of small droplets by 14%, and Bland-Altman tests showed no equivalence (limits of agreement over 20%). An artifact peak in the large size range was observed with the Spraytec, which could be due to difficulty for the multiple scattering algorithm to process high-density aerosol clouds. The difference was reduced to 5% by using the inhalation cell provided by the Spraytec with a 15 L/min aspiration. CONCLUSION: The Mastersizer X and the Spraytec cannot be considered as equivalent laser diffraction devices, but the difference can be reduced with the Spraytec inhalation cell.

Comparison of numerical simulations to experiments for atomization in a jet nebulizer.

The development of jet nebulizers for medical purposes is an important challenge of aerosol therapy. The performance of a nebulizer is characterized by its output rate of droplets with a diameter under 5 µm. However the optimization of this parameter through experiments has reached a plateau. The purpose of this study is to design a numerical model simulating the nebulization process and to compare it with experimental data. Such a model could provide a better understanding of the atomization process and the parameters influencing the nebulizer output. A model based on the Updraft nebulizer (Hudson) was designed with ANSYS Workbench. Boundary conditions were set with experimental data then transient 3D calculations were run on a 4 µm mesh with ANSYS Fluent. Two air flow rate (2 L/min and 8 L/min, limits of the operating range) were considered to account for different turbulence regimes. Numerical and experimental results were compared according to phenomenology and droplet size. The behavior of the liquid was compared to images acquired through shadowgraphy with a CCD Camera. Three experimental methods, laser diffractometry, phase Doppler anemometry (PDA) and shadowgraphy were used to characterize the droplet size distributions. Camera images showed similar patterns as numerical results. Droplet sizes obtained numerically are overestimated in relation to PDA and diffractometry, which only consider spherical droplets. However, at both flow rates, size distributions extracted from numerical image processing were similar to distributions obtained from shadowgraphy image processing. The simulation then provides a good understanding and prediction of the phenomena involved in the fragmentation of droplets over 10 µm. The laws of dynamics apply to droplets down to 1 µm, so we can assume the continuity of the distribution and extrapolate the results for droplets between 1 and 10 µm. So, this model could help predicting nebulizer output with defined geometrical and physical parameters.