Tobias Gessler

Nebulization of biodegradable nanoparticles: impact of nebulizer technology and nanoparticle characteristics on aerosol features

Nanoparticles may be effective drug delivery systems for use in various pulmonary therapeutic schemes. This study investigated the effect of nebulization technology and nanoparticle characteristics on the features of aerosol generation. Suspensions of biodegradable nanoparticles consisting of commercially available poly(lactide-co-glycolide) and novel comb polymers were nebulized with a jet, ultrasonic, and piezo-electric crystal nebulizer. The effects of the nanoparticle suspensions on the aerosol droplet size, as well as the nanoparticle size before and after nebulization, were characterized via laser diffraction. While the individual nanoparticle suspensions showed no clinically relevant influence on aerosol droplet size, as compared to control experiments, an enhanced nanoparticle aggregation within the droplets was observed. This aggregation was further characterized by fluorescence and scanning electron microscopy. Dependency of aggregation on nebulizer technology and nanoparticle characteristics was noted. Nanoparticles exhibiting the highest surface hydrophobicity were particularly susceptible to aggregation when nebulized with a jet nebulizer. Aggregation was reduced with nanoparticles exhibiting a more hydrophilic surface or when using ultrasonic nebulizers. We conclude that the biodegradable nanoparticles contained in the suspensions did not affect the aerosol droplet size in a clinically relevant manner; however, both the nanoparticle characteristics and the technique of aerosol generation influence nanoparticle aggregation occurring during aerosolization.

Ultrasonic versus jet nebulization of iloprost in severe pulmonary hypertension

Inhalation of iloprost, a stable prostacyclin analogue, is a promising perspective in the treatment of pulmonary hypertension. In initial clinical studies, a conventional jet nebulizer system was successfully used to decrease pulmonary vascular resistance and pressure, requiring however, up to twelve inhalations of 12-15 min per day. The aim of this study was to investigate if the application of an equal dose of iloprost at a drastically reduced duration of inhalation with the use of a more efficient ultrasonic nebulizer, leads to comparable haemodynamic effects, without escalation of side effects. The physical features of the jet nebulizer system (Ilo-Neb) and the ultrasonic nebulizer (Multisonic Compact) were characterized by laser diffractometry and a Tc99m-tracer technique. Mass median aerodynamic diameters were 3.2 microm for the jet and 3.9 microm for the ultrasonic nebulizer. Total output (mean+/-SD) was 60+/-7 microL.min(-1) (jet) and 163+/-15 microL.min(-1)(ultrasonic), and efficiency of the devices was 39+/-3% (jet) and 86+/-5% (ultrasonic). Based on these data, a total inhalative dose of 2.8 microg iloprost was delivered by jet nebulization within 12 min and by ultrasonic nebulization within 4 min, in 18 patients with severe primary and secondary pulmonary hypertension (New York Heart Association class III and IV), in a randomized crossover design. Haemodynamics were assessed by right heart catheterization. Inhalation with the ultrasonic device and jet nebulizer, reduced mean+/-SEM pulmonary artery pressure from 54.3+/-2.1 to 47.1+/-2.0 and from 53.5+/-2.2 to 47.0+/-2.2 mmHg, respectively, and mean+/-SEM pulmonary vascular resistance from 1,073+/-109 to 804+/-87 and from 1,069+/-125 to 810+/-83 dyn.s.cm(-5), respectively. Both modes of aerosolization were well tolerated. In conclusion, due to the markedly higher efficiency and output of the ultrasonic device, wastage of drug is largely avoided and the duration of inhalation can be shortened to one-third, with comparable haemodynamic effects and without enforcing side effects.

Characterization of novel spray-dried polymeric particles for controlled pulmonary drug delivery.

Numerous studies have addressed the controlled pulmonary drug delivery properties of colloidal particles. However, only scant information on the potential of spray-drying for submicron particle preparation is available. By exploiting the advantages of spray-drying, the characteristics of submicron particles can be optimized to meet the requirements necessary for lung application. Submicron particles were prepared from organic poly(d,l-lactide-co-glycolide) (PLGA) solutions, and composite particles were spray-dried from aqueous PLGA nanosuspensions. The feed concentration, as well as the spray-mesh diameter influenced the resulting particle sizes. Nanoparticles were virtually unaffected after spray-drying. The aerodynamic characteristics of both particle species revealed aerosol particle sizes suitable for deposition in the deep lungs (≤4μm). While the entrapped drug was released within ~90min from the composite particles, extensive drug retardation (~480min) was observed for PLGA particles spray-dried from organic solution. These results suggest that nanospray-drying is a convenient method to prepare submicron, controlled drug delivery vehicles useful for pulmonary application potentially allowing access to alveolar tissue.

Pulmonary drug delivery with aerosolizable nanoparticles in an ex vivo lung model

The use of colloidal carrier systems for pulmonary drug delivery is an emerging field of interest in nanomedicine. The objective of this study was to compare the pulmonary absorption and distribution characteristics of the hydrophilic model drug 5(6)-carboxyfluorescein (CF) after aerosolization as solution or entrapped into nanoparticles in an isolated rabbit lung model (IPL). CF-nanoparticles were prepared from a new class of biocompatible, fast degrading, branched polyesters by a modified solvent displacement method. Physicochemical properties, morphology, encapsulation efficiency, in vitro drug release, stability of nanoparticles to nebulization, aerosol characteristics as well as pulmonary dye absorption and distribution profiles after nebulization in an IPL were investigated. CF-nanoparticles were spherical in shape with a mean particle size of 195.3+/-7.1nm, a polydispersity index of 0.225+/-0.017 and a zeta-potential of -28.3+/-0.3mV. Encapsulation efficiencies of CF were as high as about 60% (drug loading of 3% (w/w)); 90% of the entrapped CF were released during the first 50min in vitro. Nanoparticle characteristics were not significantly affected by the aerosolization process utilizing a vibrating mesh nebulizer. After deposition of equal amounts of CF in the IPL, less CF was detected in the perfusate for CF-nanoparticles (plateau concentration 9.2+/-2.4ng/ml) when compared to CF aerosolized from solution (17.7+/-0.8ng/ml). In conclusion, the data suggest that inhalative delivery of biodegradable nanoparticles may be a viable approach for pulmonary drug delivery. Moreover, a targeting effect to the lung tissue is claimed.

Surfactant-Free, Biodegradable Nanoparticles for Aerosol Therapy Based on the Branched Polyesters, DEAPA-PVAL-g-PLGA

AbstractPurpose. This study describes the development of surfactant-free, biodegradable nanoparticle systems with varying physicochemical properties and their suitability for pulmonary application via nebulization. Methods. Nanoparticle suspensions were formulated from the branched polyester, diethylaminopropyl amine-poly(vinyl alcohol)-grafted-poly(lactide-co-glycolide) (DEAPA-PVAL-g-PLGA) alone, as well as with increasing amounts of carboxymethyl cellulose (CMC). Particle size, ζ potential, turbidity, and morphology (atomic force microscopy) were characterized. Three formulations were chosen for further study: Cationic nanoparticles without CMC, cationic nanoparticles with CMC, and anionic nanoparticles with an excess of CMC. Nanoparticle degradation was characterized, as well as stability during nebulization. Nanoparticle-cell interactions were investigated and quantified using confocal laser scanning microscopy and fluorescence spectrometry. Results. Nanoparticles ranged in size from 70-250 nm and displayed ζ potentials of +58.9 to −46.6 mV. Anionic nanoparticles showed the highest stability during nebulization. The degradation rate of each nanoparticle formulation decreased with increasing amounts of CMC. Cell association was highest among cationic nanoparticles (57% and 30%, respectively), although these were not internalized. Despite a lower rate of cell association (3%), anionic nanoparticles were internalized by A549 cells. Conclusions. Surfactant-free nanoparticles from DEAPA-PVAL-g-PLGA are versatile drug delivery systems; however, only the anionic formulations investigated were proven suitable for aerosol therapy.

Inhaled prostanoids in the therapy of pulmonary hypertension.

Prostacyclin and prostacyclin analogues are potent vasodilators and possess antithrombotic, anti-inflammatory and antiproliferative properties. These properties qualify them as efficient drugs for the treatment of pulmonary hypertension, a life-threatening illness characterized by an increase in artery pressure and vascular resistance in the pulmonary circulation. Diseased pulmonary vessels show specific remodeling with intimal fibrosis, medial hypertrophy, and adventitial thickening, as well as functional changes characterized by vasoconstriction and in situ thrombosis. The intravenous administration of prostacyclin is a well-established therapy option in severe pulmonary hypertension. However, lack of pulmonary and intrapulmonary selectivity can lead to life-threatening pulmonary and systemic side effects. Therefore, the application of prostanoids by inhalation had been proposed. Several studies with inhaled iloprost, a stable prostacyclin analogue, demonstrated preferential and potent vasorelaxation in the pulmonary circulation. In a randomized, double-blind, placebo controlled, multicenter study in 203 patients with pulmonary hypertension inhaled iloprost showed significant improvement of exercise capacity and pulmonary hemodynamics with excellent tolerability and safety. Consequently, inhaled iloprost has been approved in many countries for treatment of severe pulmonary hypertension. A major drawback of inhaled iloprost, however, is the short half-life and hemodynamic effect (30 to 60 min) demanding multiple daily inhalation manoeuvres (up to nine times). Strategies for further improvement of inhaled prostanoid therapy include use of prostacyclin analogues with longer half-life (e.g., treprostinil), combinations with oral drugs (e.g., phosphodiesterase inhibitors or endothelin receptor antagonists) and development of aerosolized controlled release formulations such as liposomes and nanoparticles. The therapy with prostacyclin and its analogues is a main pillar in the treatment of pulmonary hypertension, giving new hope to many patients suffering from this terrible disease. With inhaled iloprost, a new drug has enlarged the scope of aerosol therapies for treatment of pulmonary and systemic diseases.

Effects of cell-penetrating peptides and pegylation on transfection efficiency of polyethylenimine in mouse lungs

Cell‐penetrating peptides (CPPs) could potentially be used as vectors for intracellular delivery of proteins, peptides and nucleic acids. The present study examined different CPPs, such as TAT‐derived and arginine rich sequences, as well as model amphiphilic peptide, with respect to transfection efficiency of pegylated polyethylenimine (PEI) in A549, Calu‐3 cells and in mice after intra‐tracheal administration.

Biophysical investigation of pulmonary surfactant surface properties upon contact with polymeric nanoparticles in vitro

UNLABELLED Nanoparticulate drug carriers have been proposed for the targeted and controlled release of pharmaceuticals to the lung. However, inhaled particles may adversely affect the biophysical properties of pulmonary surfactant. This study examines the influence of polymeric nanoparticles with distinct physicochemical properties on the adsorption and dynamic surface tension lowering properties of pulmonary surfactant. Nanoparticles had a mean size of 100 nm with narrow size distributions. Although poly(styrene) and poly(D,L-lactide-co-glycolide) nanoparticles revealed a dose-dependent influence on biophysics of pulmonary surfactant, positively-charged nanoparticles made from poly(butyl methacrylate-co-(2-dimethylaminoethyl) methacrylate-co-methyl methacrylate) showed no effect. This behavior is attributed to the differences in ζ-potential and surface hydrophobicity, which in turn involves an altered adsorption pattern of the positively charged surfactant proteins to the nanoparticles. This study suggests that polymeric nanoparticles do not substantially affect the biophysical properties of pulmonary surfactant and may be a viable drug-delivery vehicle for the inhalative treatment of respiratory diseases. FROM THE CLINICAL EDITOR Inhaled nanoparticulate drug carriers may adversely affect the biophysical properties of pulmonary surfactant. In this study the influence of polymeric nanoparticles was characterized from this standpoint, with the conclusion that polymeric nanoparticles do not substantially affect the biophysical properties of pulmonary surfactant and may be viable drug-delivery vehicles for inhalational treatment.

Pulmonary targeting with biodegradable salbutamol-loaded nanoparticles.

BACKGROUND Aerosol therapy using particulate drug carriers has become an increasingly attractive method to deliver therapeutic or diagnostic compounds to the lung. Polymeric nanoparticles are widely investigated carriers in nanomedicine. The targeted and controlled release of drugs from nanoparticles for pulmonary delivery, however, is a research field that has been so far rather unexploited. Therefore, the objective of this study was to compare the pulmonary absorption and distribution characteristics of salbutamol after aerosolization as solution or entrapped into novel polymeric nanoparticles in an isolated rabbit lung model (IPL). METHODS Physicochemical properties, morphology, encapsulation efficiency, in vitro drug release, stability of nanoparticles to nebulization, as well as pulmonary drug absorption and distribution after nebulization in the IPL were investigated. RESULTS Salbutamol-loaded poly(D,L-lactide-co-glycolide) (PLGA) and poly(vinyl sulfonate-co-vinyl alcohol)-graft-poly(D,L-lactide-co-glycolide) (VS(72)-10) nanoparticles were prepared by a modified solvent displacement technique with a mean particle size of approximately 120 nm and a polydispersity index below 0.150. VS(72)-10 nanoparticles showed a more negative zeta-potential of -54.2 +/- 3.3 mV compared to PLGA nanoparticles (-36.5 +/- 2.6 mV). Salbutamol encapsulation efficiency was 25.2 +/- 4.9% and 63.4 +/- 3.5% for PLGA and VS(72)-10 nanoparticles, respectively. After nebulization utilizing the MicroSprayer physicochemical properties of salbutamol-loaded VS(72)-10 nanoparticles were virtually unchanged, whereas nebulized salbutamol-loaded PLGA nanoparticles showed a significant increase in mean particle size and polydispersity. In vitro release studies demonstrated a sustained release of the encapsulated salbutamol from VS(72)-10 nanoparticles. In parallel, a sustained salbutamol release profile was observed after aerosol delivery of these particles to the IPL as reflected by a lower salbutamol recovery in the perfusate (40.2 +/- 5.8%) when compared to PLGA nanoparticles (55.2 +/- 9.1%) and salbutamol solution (62.8 +/- 7.1%). CONCLUSIONS The current study suggests that inhalative delivery of biodegradable nanoparticles may be a viable approach for the treatment of respiratory diseases.

Nebulization performance of biodegradable sildenafil-loaded nanoparticles using the Aeroneb® Pro: Formulation aspects and nanoparticle stability to nebulization

Polymeric nanoparticles meet the increasing interest for drug delivery applications and hold great promise to improve controlled drug delivery to the lung. Here, we present a series of investigations that were carried out to understand the impact of formulation variables on the nebulization performance of novel biodegradable sildenafil-loaded nanoparticles designed for targeted aerosol therapy of life-threatening pulmonary arterial hypertension. Narrowly distributed poly(D,L-lactide-co-glycolide) nanoparticles (size: ∼200 nm) were prepared by a solvent evaporation technique using poly(vinyl alcohol) (PVA) as stabilizer. The aerodynamic and output characteristics using the Aeroneb Pro nebulizer correlated well with the dynamic viscosity of the employed fluids for nebulization. The nebulization performance was mainly affected by the amount of employed stabilizer, rather than by the applied nanoparticle concentration. Nanoparticles revealed physical stability against forces generated during aerosolization, what is attributed to the adsorbed PVA layer around the nanoparticles. Sildenafil was successfully encapsulated into nanoparticles (encapsulation efficiency: ∼80%). Size, size distribution and sildenafil content of nanoparticles were not affected by nebulization and the in vitro drug release profile demonstrated a sustained sildenafil release over ∼120 min. The current study suggests that the prepared sildenafil-loaded nanoparticles are a promising pharmaceutical for the therapy of pulmonary arterial hypertension.