Delivery of theophylline as dry powder for inhalation

Theophylline (TP) is a very well established orally or intravenously delivered antiasthma drug with many beneficial effects. This study aims to improve asthma treatment by creating a dry powder inhalable (DPI) formulation of TP to be delivered directly to the lung, avoiding the side effects associated with conventional oral delivery. The DPI TP formulation was investigated for its physico-chemical characteristics using scanning electron microscopy, laser diffraction, thermal analysis and dynamic vapour sorption. Furthermore, aerosol performance was assessed using the Multi Stage Liquid Impinger (MSLI). In addition, a Calu-3 cell transport assay was conducted in vitro using a modified ACI to study the impact of the DPI formulation on lung epithelial cells. Results showed DPI TP to be physico-chemically stable and of an aerodynamic size suitable for lung delivery. The aerosolisation performance analysis showed the TP DPI formulation to have a fine particle fraction of 29.70 ± 2.59% (P < 0.05) for the TP formulation containing 1.0% (w/w) sodium stearate, the most efficient for aerosolisation. Regarding the deposition of TP DPI on Calu-3 cells using the modified ACI, results demonstrated that 56.14 ± 7.62% of the total TP deposited (13.07 ± 1.69 µg) was transported across the Calu-3 monolayer over 180 min following deposition, while 37.05 ± 12.62% of the deposited TP was retained in the cells. This could be due to the presence of sodium stearate in the current formulation that increased its lipophilicity. A DPI formulation of TP was developed that was shown to be suitable for inhalation.     

Towards the bioequivalence of pressurised metered dose inhalers 2. Aerodynamically equivalent particles (with and without glycerol) exhibit different biopharmaceutical profiles in vitro

Two solution-based pressurised metered dose inhaler (pMDI) formulations were prepared such that they delivered aerosols with identical mass median aerodynamic diameters, but contained either beclomethasone dipropionate (BDP) alone (glycerol-free formulation) or BDP and glycerol in a 1:1 mass ratio (glycerol-containing formulation). The two formulations were deposited onto Calu-3 respiratory epithelial cell layers cultured at an air interface. Equivalent drug mass (∼1000 ng or ∼2000 ng of the formulation) or equivalent particle number (1000 ng of BDP in the glycerol-containing versus 2000 ng of BDP in the glycerol-free formulation) were deposited as aerosolised particles on the air interfaced surface of the cell layers. The transfer rate of BDP across the cell layer after deposition of the glycerol-free particles was proportional to the mass deposited. In comparison, the transfer of BDP from the glycerol-containing formulation was independent of the mass deposited, suggesting that the release of BDP is modified in the presence of glycerol. The rate of BDP transfer (and the extent of metabolism) over 2 h was faster when delivered in glycerol-free particles, 465.01 ng ± 95.12 ng of the total drug (20.99 ± 4.29%; BDP plus active metabolite) transported across the cell layer, compared to 116.17 ng ± 3.07 ng (6.07 ± 0.16%) when the equivalent mass of BDP was deposited in glycerol-containing particles. These observations suggest that the presence of glycerol in the maturated aerosol particles may influence the disposition of BDP in the lungs.     

A new Pharmaceutical Aerosol Deposition Device on Cell Cultures (PADDOCC) to evaluate pulmonary drug absorption for metered dose dry powder formulations

Absorption studies with aerosol formulation delivered by metered dose inhalers across cell- and tissue-based in vitro models of the pulmonary epithelia are not trivial due to the complexity of the processes involved: (i) aerosol generation and deposition, (ii) drug release from the carrier, and (iii) absorption across the epithelial air-blood barrier. In contrast to the intestinal mucosa, pulmonary epithelia are only covered by a thin film of lining fluid. Submersed cell culture systems would not allow to studying the deposition of aerosol particles and their effects on this delicate epithelial tissue.We developed a new Pharmaceutical Aerosol Deposition Device on Cell Cultures (PADDOCC) to mimic the inhalation of a single metered aerosol dose and its subsequent deposition on filter-grown pulmonary epithelial cell monolayers exposed to an air-liquid interface. The reproducibility of deposition of these dry powder aerosols and subsequent drug transport across Calu-3 monolayers with commercially available dry powder inhalers containing salbutamol sulphate or budesonide could be demonstrated.In the context of developing new dry powder aerosol formulations, PADDOCC appears as a useful tool, allowing reducing animal testing and faster translation into clinical trials.     

Liposomal Nanoparticles Control the Uptake of Ciprofloxacin Across Respiratory Epithelia

Purpose

Liposomal ciprofloxacin nanoparticles were developed to overcome the rapid clearance of antibiotics from the lungs. The formulation was evaluated for its release profile using an air interface Calu-3 cell model and further characterised for aerosol performance and antimicrobial activity.

Methods

Liposomal and free ciprofloxacin formulations were nebulised directly onto Calu-3 bronchial epithelial cells placed in an in vitro twin-stage impinger (TSI) to assess the kinetics of release. The aerosol performance of both the liposomal and free ciprofloxacin formulation was characterised using the next generation impactor. Minimum inhibitory and bactericidal concentrations (MICs and MBCs) were determined and compared between formulations to evaluate the antibacterial activity.

Results

The liposomal formulation successfully controlled the release of ciprofloxacin in the cell model and showed enhanced antibacterial activity against Pseudomonas aeruginosa. In addition, the formulation displayed a respirable aerosol fraction of 70.5?±?2.03% of the emitted dose.

Conclusion

Results indicate that the in vitro TSI air interface Calu-3 model is capable of evaluating the fate of nebulised liposomal nanoparticle formulations and support the potential for inhaled liposomal ciprofloxacin to provide a promising treatment for respiratory infections.     

Deposition, diffusion and transport mechanism of dry powder microparticulate salbutamol, at the respiratory epithelia

The deposition, dissolution and transport of salbutamol base (SB) and salbutamol sulfate (SS) inhalation powders were investigated using the Calu-3 air interface cell culture model and Franz diffusion cell. Drug uptake by cells was studied with respect to deposited dose, drug solubility and hydrophobicity. Furthermore, the role of active transport via organic cationic transporters (OCTs) was studied. SB and SS were processed to have similar diameters (3.09 ± 0.06 μm and 3.07 ± 0.03 μm, respectively) and were crystalline in nature. Analysis of drug wetting, dissolution and diffusion using a conventional in vitro Franz cell (incorporating a cell culture support Transwell polyester membrane) showed diffusion of SB to be slower than that of SS (98.57 ± 4.23 μg after 4 h for SB compared to 98.57 ± 4.01 μg after 15 min for SS). Such observations suggest dissolution to be the rate-limiting step. In comparison, the percentage transfer rate using the air interface Calu-3 cell model suggested SB transport to be significantly faster than SS transport (92.02 ± 4.47 μg of SB compared to 63.76 ± 8.84 μg of SS transported over 4 h), indicating that passive diffusion through the cell plays a role in transport. Furthermore, analysis of SB and SS transport, over a range of deposited doses, suggested the transport rate in the Franz diffusion cell to be limited by wetting of the particle and dissolution into the medium. However, for the cell monolayer, the cell membrane properties regulate the diffusion and transport rate. Analysis of the drug transport in the presence of triethylamine (TEA), a known inhibitor of OCTs, resulted in a significant decrease in drug transport, suggesting an active transport mechanism. The presence of OCTs in this cell line was further validated by Western blot analysis. Finally, the transport of SS from a commercial product (Ventolin Rotacaps) was studied and showed good agreement with the model SS system studied here.     

Human Stimulus Factor Is a Promising Peptide for Delivery of Therapeutics

Fluticasone propionate uptake in the presence of a proprietary cell-penetrating peptide (human stimulus factor, [HSF]) based on the N-terminal domain of lactoferrin was studied, alone and in combination with salmeterol, using an air interface Calu-3 epithelial model. The HSF enhanced uptake and transport of fluticasone propionate across the epithelial barrier when alone and in presence of salmeterol. This was attributed to transcellular-mediated uptake. This HSF is a promising peptide for delivery of therapeutics where enhanced epithelial penetrating is required.     

Poly(vinyl alcohol) nanoparticle stability in biological media and uptake in respiratory epithelial cell layers in vitro

The influence of the size and surface properties of nanoparticles (NP) upon respiratory epithelial cell uptake and translocation is difficult to study, because NP properties are often modified upon suspension in biological fluids. However, a recently developed novel fluorescently labelled poly(vinyl alcohol) (PVA) NP, which does not aggregate in simple biological fluids, is suitable for drug delivery and can be produced with a range of surface properties is a pertinent advance in this field. The aim of this study was to employ the PVA NP to investigate how surface properties influence particle uptake and translocation across Calu-3 epithelial cell layers. Several grades of PVA were synthesised, characterised and labelled covalently with carboxyfluorescein. The labelled PVA was used to fabricate trackable NP that displayed either neutral or positive charge when suspended in Hank’s Balanced Salt Solution. The NP were applied to the apical surface of Calu-3 cell layers which internalised up to 11% of the applied particle dose. The maximum fraction that translocated the Calu-3 barrier in 14 h was 1.3%.     

In vitro and ex vivo methods predict the enhanced lung residence time of liposomal ciprofloxacin formulations for nebulisation

Liposomal ciprofloxacin formulations have been developed with the aim of enhancing lung residence time, thereby reducing the burden of inhaled antimicrobial therapy which requires multiple daily administration due to rapid absorptive clearance of antibiotics from the lungs. However, there is a lack of a predictive methodology available to assess controlled release inhalation delivery systems and their effect on drug disposition. In this study, three ciprofloxacin formulations were evaluated: a liposomal formulation, a solution formulation and a 1:1 combination of the two (mixture formulation). Different methodologies were utilised to study the release profiles of ciprofloxacin from these formulations: (i) membrane diffusion, (ii) air interface Calu-3 cells and (iii) isolated perfused rat lungs. The data from these models were compared to the performance of the formulations in vivo. The solution formulation provided the highest rate of absorptive transport followed by the mixture formulation, with the liposomal formulation providing substantially slower drug release. The rank order of drug release/transport from the different formulations was consistent across the in vitro andex vivo methods, and this was predictive of the profiles in vivo. The use of complimentary in vitro and ex vivo methodologies provided a robust analysis of formulation behaviour, including mechanistic insights, and predicted in vivo pharmacokinetics.     

Preparation and characterisation of controlled release co-spray dried drug-polymer microparticles for inhalation 2: Evaluation of in vitro release profiling methodologies for controlled release respiratory aerosols.

Three in vitro methodologies were evaluated as models for the analysis of drug release from controlled release (CR) microparticulates for inhalation. USP Apparatus 2 (dissolution model), USP Apparatus 4 (flow through model) and a modified Franz cell (diffusion model), were investigated using identical sink volumes and temperatures (1000ml and 37 degrees C). Microparticulates containing DSCG and different percentages of PVA (0%, 30%, 50%, 70% and 90%) were used as model CR formulations. Evaluation of the release profiles of DSCG from the modified PVA formulations, suggested that all data fitted a Weibull distribution model with R(2)0.942. Statistical analysis of the t(d) (time for 63.2% drug release) indicated that all methodologies could distinguish between microparticles that did or did not contain PVA (Students t-test, p<0.05). However, only the diffusion model could differentiate between samples containing different PVA percentages. Similar results were observed when analysing the data using similarity and difference factors. Furthermore, analysis of the release kinetic profiles for all samples suggested the data fitted the Higuchi diffusion model (R(2)0.862 for the diffusion methodology data set). Due to the relatively low water content in the respiratory tract and the lack of differentiation between formulations for USP Apparatus 2 and 4, it is concluded that the diffusion model is more applicable for the evaluation of CR inhalation medicines.     

Is the cellular uptake of respiratory aerosols delivered from different devices equivalent?

The study focuses on the application of a cell integrated modified Andersen Cascade Impactor (ACI) as an in vitro lung model for the evaluation of aerosols’ behaviour of different formulation devices, containing the same active drug, specifically nebuliser, pressurised metered dose inhaler (pMDI) and dry powder inhaler (DPI). Deposition and transport profiles of the three different inhaled salbutamol sulphate (SS) formulations with clinically relevant doses were evaluated using a modified ACI coupled with the air interface Calu-3 bronchial cell model. Reproducible amounts of SS were deposited on Snapwells for the different formulations, with no significant difference in SS deposition found between the standard ACI plate and modified plate. The transport of SS aerosols produced from pMDI formulation had similar transport kinetics to nebulised SS but significantly higher compared to the DPI, which could have led to the differences in clinical outcomes. Furthermore, drug absorption of different inhaled formulation devices of the same aerodynamic fraction was found not to be equivalent due to their physical chemical properties upon aerosolisation. This study has established an in vitro platform for the evaluation of the different inhaled formulations in physiologically relevant pulmonary conditions.     

Functional and cytometric examination of different human lung epithelial cell types as drug transport barriers

To develop inhaled medications, various cell culture models have been used to examine the transcellular transport or cellular uptake properties of small molecules. For the reproducible high throughput screening of the inhaled drug candidates, a further verification of cell architectures as drug transport barriers can contribute to establishing appropriate in vitro cell models. In the present study, side-by-side experiments were performed to compare the structure and transport function of three lung epithelial cells (Calu-3, normal human bronchial primary cells (NHBE), and NL-20). The cells were cultured on the nucleopore membranes in the air–liquid interface (ALI) culture conditions, with cell culture medium in the basolateral side only, starting from day 1. In transport assays, paracellular transport across all three types of cells appeared to be markedly different with the NHBE or Calu-3 cells, showing low paracellular permeability and high TEER values, while the NL-20 cells showed high paracellular permeability and low TEER. Quantitative image analysis of the confocal microscope sections further confirmed that the Calu-3 cells formed intact cell monolayers in contrast to the NHBE and NL-20 cells with multilayers. Among three lung epithelial cell types, the Calu-3 cell cultures under the ALI condition showed optimal cytometric features for mimicking the biophysical characteristics of in vivo airway epithelium. Therefore, the Calu-3 cell monolayers could be used as functional cell barriers for the lung-targeted drug transport studies.     

Combined Inhaled Salbutamol and Mannitol Therapy for Mucus Hyper-secretion in Pulmonary Diseases

This study focuses on the co-engineering of salbutamol sulphate (SS), a common bronchodilator, and mannitol (MA), a mucolytic, as a potential combination therapy for mucus hypersecretion. This combination was chosen to have a synergic effect on the airways: the SS will act on the β₂-receptor for relaxation of smooth muscle and enhancement of ciliary beat frequency, whilst mannitol will improve the fluidity of mucus, consequently enhancing its clearance from the lung. A series of co-spray-dried samples, containing therapeutically relevant doses of SS and MA, were prepared. The physico-chemical characteristics of the formulations were evaluated in terms of size distribution, morphology, thermal and moisture response and aerosol performance. Additionally, the formulations were evaluated for their effects on cell viability and transport across air interface Calu-3 bronchial epithelial cells, contractibility effects on bronchial smooth muscle cells and cilia beat activity using ciliated nasal epithelial cells in vitro. The formulations demonstrated size distributions and aerosol performance suitable for inhalation therapy. Transport studies revealed that the MA component of the formulation enhanced penetration of SS across the complex mucus layer and the lung epithelia cells. Furthermore, the formulation in the ratios of SS 10⁻⁶ and MA 10⁻³ M gave a significant increase in cilia beat frequency whilst simultaneously preventing smooth muscle contraction associated with mannitol administration. These studies have established that co-spray dried combination formulations of MA and SS can be successfully prepared with limited toxicity, good aerosol performance and the ability to increase ciliary beat frequency for improving the mucociliary clearance in patients suffering from hyper-secretory diseases, whilst simultaneously acting on the underlying smooth muscle.

Electronic supplementary material

The online version of this article (doi:10.1208/s12248-014-9560-4) contains supplementary material, which is available to authorized users.KEY WORDS: cilia responce, epithelia transport, lung delivery, mannitol, salbutamol, smooth muscle responce     

Preparation and characterisation of controlled release co-spray dried drug–polymer microparticles for inhalation 1: Influence of polymer concentration on physical and in vitro characteristics

A series of co-spray dried microparticles containing di-sodium cromoglycate (DSCG) and polyvinyl alcohol (PVA - 0%, 30%, 50%, 70% and 90% w/w, respectively), were prepared as potential controlled release (CR) viscous/gelling vehicles for drug delivery to the respiratory tract. The microparticles were characterised in terms of particle size, crystal structure, density, surface morphology, moisture sorption, surface energy and in vitro aerosolisation efficiency. The co-spray dried particles were amorphous in nature and had spherical geometry. High-resolution atomic force microscopy analysis of the surfaces of the DSCG/PVA suggested no significant differences in roughness between microparticles containing 30-90% w/w PVA (ANOVA, p<0.05), while no specific trend in either size or density was observed with respect to PVA concentration. In comparison, a linear decrease in the relative moisture sorption (R2=0.997) and concurrent increase in total surface free energy (R2=0.870) were observed as PVA concentration was increased. Furthermore a linear increase in the aerosolisation efficiency, measured by inertial impaction, was observed as PVA concentration was increased (R2=0.993). In addition, the increase in aerosolisation efficiency showed good correlation with equilibrium moisture content (R2=0.974) and surface energy measurement (R2=0.905). These relationships can be attributed to the complex interplay of particle forces at the contiguous interfaces in this particulate system.     

Aerosol Dispersion of Respirable Particles in Narrow Size Distributions Using Drug-Alone and Lactose-Blend Formulations

PURPOSE: To examine the effect of formulation type on the aerosolization of respirable particles in narrow size distributions. METHODS: Aerosol dispersion of two formulation types (drug alone and 2% w/w drug-lactose blends) containing micronized or spray-dried fluticasone propionate (FP) particles (d50% = 1.3 to 9.6 microm, GSD = 1.8 to 2.2) were examined using cascade impaction at 60 l/min with low and high resistance inhaler devices: Rotahaler and Inhalator, respectively. RESULTS: The aerosol dispersion of FP particles was significantly affected by the particle size, particle type, inhaler device, and formulation type. Interactions were observed between all factors. Generally, greater powder entrainment was obtained with smaller d50%. Higher emitted doses were obtained from drug-alone formulations of spray-dried FP particles and lactose blends of micronized FP particles. Greater aerosol dispersion of spray-dried FP particles was obtained using lactose-blend formulations with d50% around 4 microm. Greater aerosol dispersion of micronized FP particles was obtained using formulations of drug alone. Larger d50% produced larger mass median aerodynamic diameters. CONCLUSIONS: Small changes in the particle size within the 1-10-microm range exerted a major influence on aerosol dispersion of jet-milled and spray-dried FP particles using drug-alone and lactose-blend formulations.     

Transport and local metabolism of budesonide and fluticasone propionate in a human bronchial epithelial cell line (Calu-3)

Calu-3 cells grown on microporous filters at an air interface for 16-18 days were incubated with the glucocorticosteroid (GCS) budesonide (BUD). Apparent permeability (P(app)) of BUD across Calu-3 cell monolayers was determined. Amount of BUD transported across Calu-3 cells was clearly concentration dependent, and no polarised transport was detected. When cells were loaded with BUD by incubation with drug solution (30 microM) for 2 h, 9.35 +/- 0.53% of the initial dose of BUD, corresponding to 5.5 microg BUD/mg cell protein was retained intracellularly, and released over a time period of 10 h. Apical release of BUD was significantly higher than release to the basolateral side of the monolayer. In comparison, when Calu-3 cells were loaded with fluticasone propionate (FP) solution (0.8 microM), about 20% of the initial dose of FP, corresponding to 0.3 microg FP/mg total cell protein content was detected intracellularly and released immediately (45 min). There was no difference in FP release between the apical and basolateral side of the cell layer. Mass spectrometry of cell extracts indicated the presence of fatty acid conjugates of BUD. We conclude that Calu-3 cells are able to store BUD by intracellular conjugation to fatty acids. We, therefore, suggest the use of the Calu-3 cell model as a tool for examination of local pharmacokinetics and metabolism of GCS at the bronchial epithelium.     

In Vitro Cell Integrated Impactor Deposition Methodology for the Study of Aerodynamically Relevant Size Fractions from Commercial Pressurised Metered Dose Inhalers

Purpose

The purpose of this study was to present a modified Andersen cascade impactor (ACI) as a platform to evaluate the deposition and subsequent transport of aerosol micropaticles across airway epithelial cells.

Methods

The impaction plate of an ACI was modified to accommodate up to eight Snapwells. Aerodynamic particle size distribution of the modified ACI was investigated with two commercially available formulations of Ventolin® (salbutamol sulphate) and QVAR® (beclomethasone dipropionate). Deposition and transport of these drug microparticles across sub-bronchial epithelial Calu-3 cells were also studied.

Results

The modified ACI demonstrated reproducible deposition patterns of the commercially available pressurised metered dose inhalers compared to the standard ACI. Furthermore, the Calu-3 cells could be placed in different stages of the modified ACI. No significant effect was observed among the transport rate of different particle sizes deposited on Calu-3 cells within the range of 3.3 to 0.4 μm.

Conclusions

The use of the cell compatible ACI to assess the fate of microparticles after deposition on the respiratory epithelia may allow for better understanding of deposited microparticles in vivo.     

The Extracellular Microenvironment Explains Variations in Passive Drug Transport Across Different Airway Epithelial Cell Types

Purpose

We sought to identify key variables in cellular architecture and physiology that might explain observed differences in the passive transport properties of small molecule drugs across different airway epithelial cell types.

Methods

Propranolol (PR) was selected as a weakly basic, model compound to compare the transport properties of primary (NHBE) vs. tumor-derived (Calu-3) cells. Differentiated on Transwell? inserts, the architecture of pure vs. mixed cell co-cultures was studied with confocal microscopy followed by quantitative morphometric analysis. Cellular pharmacokinetic modeling was used to identify parameters that differentially affect PR uptake and transport across these two cell types.

Results

Pure Calu-3 and NHBE cells possessed different structural and functional properties. Nevertheless, mixed Calu-3 and NHBE cell co-cultures differentiated as stable cell monolayers. After measuring the total mass of PR, the fractional areas covered by Calu-3 and NHBE cells allowed deconvoluting the transport properties of each cell type. Based on the apparent thickness of the unstirred, cell surface aqueous layer, local differences in the extracellular microenvironment explained the measured variations in passive PR uptake and permeation between Calu-3 and NHBE cells.

Conclusion

Mixed cell co-cultures can be used to compare the local effects of the extracellular microenvironment on drug uptake and transport across two epithelial cell types.     

Inhalable tranexamic acid for haemoptysis treatment

PurposeAn inhalable dry powder formulation of tranexamic acid (TA) was developed and tested in a novel high-dose Orbital® multi-breath inhaler. The formulation was specifically intended for the treatment of pulmonary haemorrhage and wound healing associated with haemoptysis.MethodsInhalable TA particles were prepared by spray drying and the powder characterised using laser diffraction, electron microscopy, thermal analysis, moisture sorption and X-ray powder diffraction. The aerosol performance was evaluated using cascade impaction and inline laser diffraction and interaction with epithelia cells and wound healing capacity investigated using Calu-3 air interface model.ResultsThe spray dried TA particles were crystalline and spherical with a D_0.5 of 3.35 μm. The powders were stable and had limited moisture sorption (0.307% w/w at 90% RH). The Orbital device delivered ca. 38 mg powder per ‘inhalation’ at 60 l · min⁻¹ across four sequential shots with an overall fine particle fraction (⩽6.4 μm) of 59.3 ± 3.5% based on the emitted mass of ca. 150 mg. The TA particles were well tolerated by Calu-3 bronchial epithelia cells across a wide range of doses (from 1 nM to 10 nM) and no increase in inflammatory mediators was observed after deposition of the particles (a decrease in IL-1β, IL-8 and INFγ was observed). Time lapse microscopy of a damaged confluent epithelia indicated that wound closure was significantly greater in TA treated cells compared to control.ConclusionA stable, high performance aerosol of TA has been developed in a multi-breath DPI device that can be used for the treatment of pulmonary lesions and haemoptysis.     

Core–shell Particles for the Dispersion of Small Polar Drugs and Biomolecules in Hydrofluoroalkane Propellants

Purpose Demonstrate the applicability of a novel particle-based technology for the development of suspensions of small polar drugs and biomolecules in hydrofluoroalkane (HFA) propellants for pressurized metered-dose inhalers (pMDIs). Materials and Methods Emulsification diffusion was used to prepare core–shell particles. The shell consisted of oligo(lactide) grafts attached onto a short chitosan backbone. The active drug was arrested within the particle core. Colloidal Probe Microscopy (CPM) was used to determine the cohesive forces between particles in a model HFA propellant. The aerosol characteristics of the formulations were determined using an Anderson Cascade Impactor (ACI). Cytotoxicity studies were performed on lung epithelial and alveolar type II cells. Results CPM results indicate that particle cohesive forces in liquid HFA are significantly screened in the presence of the polymeric shell and correlate well with the physical stability of suspensions in propellant HFA. The proposed formulation showed little or no cytotoxic effects on both Calu-3 and A549 cells. Conclusions Core–shell particles with a shell containing the lactide moiety as the HFA-phile showed excellent dispersion stability and aerosol characteristics in HFA-based pMDIs. This is a general strategy that can be used for developing novel suspension pMDIs of both small polar drugs and large therapeutic molecules.     

Evaluation of air-interfaced Calu-3 cell layers for investigation of inhaled drug interactions with organic cation transporters in vitro

A physiologically pertinent in vitro model is urgently needed for probing interactions between inhaled drugs and the organic cation transporters (OCT) in the bronchial epithelium. This study evaluated OCT expression, functionality, inhibition by common inhaled drugs and impact on formoterol transepithelial transport in layers of human bronchial epithelial Calu-3 cells grown at an air-liquid interface. 21 day old Calu-3 layers expressed OCT1, OCT3, OCTN1 and OCTN2 whereas OCT2 could not be detected. Quantification of the cellular uptake of the OCT substrate ASP(+) in presence of inhibitors suggested several OCT were functional at the apical side of the cell layers. ASP(+) uptake was reduced by the bronchodilators formoterol, salbutamol (albuterol), ipratropium and the glucocorticoid budesonide. However, the OCT inhibitory properties of the two β(2)-mimetics were suppressed at therapeutically relevant concentrations. The absorptive permeability of formoterol across the cell layers was enhanced at a high drug concentration shown to decrease ASP(+) uptake by ～50% as well as in presence of the OCT inhibitor tetraethylammonium (TEA). Secretory transport was unaffected by the drug concentration but was reduced by TEA. Our data indicate air-interfaced Calu-3 layers offer a low-cost in vitro model suitable for assessing inhaled drug-OCT interactions in the bronchial epithelium.