In Vitro Evaluation of Aerosol Delivery by Hand-Held Mesh Nebulizers in an Adult Spontaneous Breathing Lung Model

Impact of mucus modulation by N-acetylcysteine on nanoparticle toxicity

Human respiratory mucus is a biological hydrogel that forms a protective barrier for the underlying epithelium. Modulation of the mucus layer has been employed as a strategy to enhance transmucosal drug carrier transport. However, a drawback of this strategy is a potential reduction of the mucus barrier properties, in particular in situations with an increased exposure to particles. In this study, we investigated the impact of mucus modulation on its protective role. In vitro mucus was produced by Calu-3 cells, cultivated at the air-liquid interface for 21 days and used for further testing as formed on top of the cells. Analysis of confocal 3D imaging data revealed that after 21 days Calu-3 cells secrete a mucus layer with a thickness of 24 ± 6 μm. Mucus appeared to restrict penetration of 500 nm carboxyl-modified polystyrene particles to the upper 5-10 μm of the layer. Furthermore, a mucus modulation protocol using aerosolized N-acetylcysteine (NAC) was developed. This treatment enhanced the penetration of particles through the mucus down to deeper layers by means of the mucolytic action of NAC. These findings were supported by cytotoxicity data, indicating that intact mucus protects the underlying epithelium from particle-induced effects on membrane integrity. The impact of NAC treatment on the protective properties of mucus was probed by using 50 and 100 nm amine-modified and 50 nm carboxyl-modified polystyrene nanoparticles, respectively. Cytotoxicity was only induced by the amine-modified particles in combination with NAC treatment, implying a reduced protective function of modulated mucus. Overall, our data emphasize the importance of integrating an assessment of the protective function of mucus into the development of therapy approaches involving mucus modulation.

Predicting Inhaled Drug Dose Generated by Mesh Nebulizers

Background: The lung dose of nebulized drugs for spontaneous breathing is influenced by breathing patterns and nebulizer performance. This study aimed to develop a system for measuring breath patterns and a formula for estimating inhaled drugs, and then to validate the hypothesized prediction formula. Methods: An in vitro model was first used to determine correlations among the delivered dose, breath patterns, and doses deposited on the accessories and reservoirs testing with a breathing simulator to generate 12 adult breathing patterns (n = 5). A pressure sensor was developed to measure breathing parameters and used along with a prediction formula that accounted for the initial charge dose, respiratory pattern, and dose on the accessory and reservoir of a nebulizer. Three brands of nebulizers were tested by placing salbutamol (5.0 mg/2.5 mL) in the drug holding chamber. Ten healthy individuals participated in the ex vivo study to validate the prediction formula. The agreement between the predicted and inhaled doses was analyzed using the Bland-Altman plot. Results: The in vitro model showed that the inspiratory time to total respiratory cycle time (Ti/Ttotal; %) was significantly directly correlated with the delivered dose among the respiratory factors, followed by inspiratory flow, respiratory rate, and tidal volume. The ex vivo model showed that Ti/Ttotal was significantly directly correlated with the delivered dose among the respiratory factors, in addition to the nebulization time and accessory dose. The Bland-Altman plots for the ex vivo model showed similar results between the two methods. Large differences in inhaled dose measured at the mouth were observed among the subjects, ranging from 12.68% to 21.68%; however, the difference between the predicted dose and inhaled dose was lower, at 3.98%-5.02%. Conclusions: The inhaled drug dose could be predicted with the hypothesized estimation formula, which was validated by the agreement between the inhaled and predicted doses of breathing patterns of healthy individuals.

Good Practices for the Laboratory Performance Testing of Aqueous Oral Inhaled Products (OIPs): an Assessment from the International Pharmaceutical Aerosol Consortium on Regulation and Science (IPAC-RS)

Multiple sources must be consulted to determine the most appropriate procedures for the laboratory-based performance evaluation of aqueous oral inhaled products (OIPs) for the primary measures, dose uniformity/delivery, and aerodynamic particle (droplet) size distribution (APSD). These sources have been developed at different times, mainly in Europe and North America, during the past 25 years by diverse organizations, including pharmacopeial chapter/monograph development committees, regulatory agencies, and national and international standards bodies. As a result, there is a lack of consistency across all the recommendations, with the potential to cause confusion to those developing performance test methods. We have reviewed key methodological aspects of source guidance documents identified by a survey of the pertinent literature and evaluated the underlying evidence supporting their recommendations for the evaluation of these performance measures. We have also subsequently developed a consistent series of solutions to guide those faced with the various associated challenges when developing OIP performance testing methods for oral aqueous inhaled products.

Piezoelectric atomization of liquids with dynamic viscosities up to 175 cP at room temperature

Piezoelectric atomization has been applied in the field of respiratory medicine delivery and chemistry. However, the wider application of this technique is limited by the viscosity of the liquid. High-viscosity liquid atomization has great potential for applications in aerospace, medicine, solid-state batteries and engines, but the actual development of atomization is behind expectations. In this study, instead of the traditional model of single-dimensional vibration as a power supply, we propose a novel atomization mechanism that uses two coupled vibrations to induce micro-amplitude elliptical motion of the particles on the surface of the liquid carrier, which produces a similar effect as localized traveling waves to push the liquid forward and induce cavitation to achieve atomization. To achieve this, a flow tube internal cavitation atomizer (FTICA) consisting of a vibration source, a connecting block and a liquid carrier is designed. The prototype can atomize liquids with dynamic viscosities up to 175 cP at room temperature with a driving frequency of 507 kHz and a voltage of 85 V. The maximum atomization rate in the experiment is 56.35 mg/min, and the average atomized particle diameter is 10 µm. Vibration models for the three parts of the proposed FTICA are established, and the vibration characteristics and atomization mechanism of the prototype were verified using the vibration displacement measurement experiment and the spectroscopic experiment. This study offers new possibilities for transpulmonary inhalation therapy, engine fuel supply, solid-state battery processing and other areas where high-viscosity microparticle atomization is needed.