Preparation and characterization of spray-dried tobramycin powders containing nanoparticles for pulmonary delivery

Using high-pressure homogenization and spray-drying techniques, novel formulations were developed for manufacturing dry powder for inhalation, composed of a mixture of micro- and nanoparticles in order to enhance lung deposition. Particle size analysis was performed by laser diffraction. Spray-drying was applied in order to retrieve nanoparticles in dried-powder state from tobramycin nanosuspensions. The aerolization properties of the different formulations were evaluated by a multi-stage liquid impinger. Suspensions of nanoparticles of tobramycin containing Na glycocholate at 2% (w/w) relative to tobramycin content and presenting a mean particle size about 200 nm were produced. The results from the spray-dried powders showed that the presence of nanoparticles in the formulations improved particle dispersion properties during inhalation. The fine particle fraction (percentage of particles below 5 microm) increased from 36% for the raw micronized tobramycin material to about 61% for the most effective formulation. These new nanoparticle-containing tobramycin DPI formulations, based on the use of very low level of excipient and presenting high lung deposition properties, offer very important perspectives for improving the delivery of drugs to the pulmonary tract.     

Chitosan-Modified Dry Powder Formulations for Pulmonary Gene Delivery

Purpose Spray-drying is an effective process for preparing micron-dimensioned particles for pulmonary delivery. Previously, we have demonstrated enhanced dispersibility and fine particle fraction of spray-dried nonviral gene delivery formulations using amino acids or absorption enhancers as dispersibility-enhancing excipients. In this study, we investigate the use of the cationic polymer chitosan as a readily available and biocompatible dispersibility enhancer. Methods Lactose-lipid:polycation:pDNA (LPD) powders were prepared by spray-drying and post-mixed with chitosan or spray-dried chitosan. In addition, the water-soluble chitosan derivative, trimethyl chitosan, was added to the lactose-LPD formulation before spray-drying. Results Spray-dried chitosan particles, displaying an irregular surface morphology and diameter of less than 2 μm, readily adsorbed to lactose-LPD particles following mixing. In contrast with the smooth spherical surface of lactose-LPD particles, spray-dried trimethyl chitosan-lactose-LPD particles demonstrated increased surface roughness and a unimodal particle size distribution (mean diameter 3.4 μm), compared with the multimodal distribution for unmodified lactose-LPD powders (mean diameter 23.7 μm). The emitted dose and in vitro deposition of chitosan-modified powders was significantly greater than that of unmodified powders. Moreover, the inclusion of chitosan mediated an enhanced level of reporter gene expression. Conclusions In summary, chitosan enhances the dispersibility and in vitro pulmonary deposition performance of spray-dried powders.     

Enhanced Dispersibility and Deposition of Spray-dried Powders for Pulmonary Gene Therapy

Spray-drying represents a viable alternative to freeze-drying for preparing dry powder dispersions for delivering macromolecules to the lung. The dispersibility of spray-dried powders is limited however, and needs to be enhanced to improve lung deposition and subsequent biological activity. In this study, we investigate the utility of leucine as a dry powder dispersibility enhancer when added prior to spray-drying a model non-viral gene therapy formulation (lipid:polycation:pDNA, LPD). Freeze-dried lactose–LPD, spray-dried lactose–LPD and spray-dried leucine–lactose–LPD powders were prepared. Scanning electron microscopy showed that leucine increased the surface roughness of spray-dried lactose particles. Particle size analysis revealed that leucine-containing spray-dried powders were unimodally dispersed with a mean particle diameter of 3.12 μm. Both gel electrophoresis and in vitro cell (A549) transfection showed that leucine may compromise the integrity and biological functionality of the gene therapy vector. The deposition of the leucine containing powder was however significantly enhanced as evidenced by an increase in gene expression mediated by dry powder collected at lower stages of a multistage liquid impinger (MSLI). Further studies are required to determine the potential of leucine as a ubiquitous dispersibility enhancer for a variety of pulmonary formulations.     

Inhalable Spray-Freeze-Dried Powder with L-Leucine that Delivers Particles Independent of Inspiratory Flow Pattern and Inhalation Device

Purpose

The purpose of this study was to develop inhalable particles that can reach deep into the lungs efficiently independent of inhalation patterns of patients and inhalation devices. We prepared porous particles including L-leucine (Leu), a dispersive agent, by a spray-freeze-drying (SFD) method and examined the influence of inspiratory flow patterns and inhalation devices with various inhalation resistances.

Methods

Four types of SFD powder with different Leu contents (0–10%) were prepared. Scanning electron microscopy and laser diffraction were used to measure the morphology and size distribution of the powders. In-vitro inhalation characteristics were determined using a twin-stage liquid impinger equipped with an inspiratory flow pattern simulator. The effects of Leu on the adhesion force and electrostatic property of the particles were evaluated.

Results

The inhalation performance of the powders was improved by the addition of Leu. The powders with Leu showed a high inhalation performance regardless of inspiratory flow patterns and devices. The addition of Leu decreased the adhesion force and increased the surface potential of the powders.

Conclusions

The SFD particles with Leu showed high inhalation performance regardless of the inhalation patterns and devices, which was attributed to the decreased adhesion force between particles and increased dispersibility.

     

Colistin Powders with High Aerosolisation Efficiency for Respiratory Infection: Preparation and In Vitro Evaluation

In many respiratory infections caused by multi-drug-resistant Gram-negative bacteria, colistin is often the last-line drug for treatment despite its nephrotoxicity when administered parenterally. Inhalation therapy of colistin has great potential to improve the efficacy while reducing adverse effects. In this study, inhalable powder formulations of colistin (sulphate) were produced via spray drying. The colistin powders were found to have intact antimicrobial activity against Acinetobacter baumannii measured by broth micro-dilution. Both the raw material and spray-dried formulations were amorphous and absorbed significant amount of water up to 30% (w/w) at relative humidity (RH) of at least 70%. The spray-dried formulations were physically stable in the amorphous form at 60% RH and 25°C, having a high aerosol efficiency (emitted dose >86% and fine particle fraction total >83%) which remained unchanged after a 3-month storage. Storage at an elevated RH of 75% resulted in the aerosolisation performance significantly decreased, and at RH 90%, the formulation particles fused together (but without re-crystallisation). Although spray drying has been extensively used for generating inhalable drug particles, this is the first report that colistin powder can be physically stable in the amorphous form at ambient conditions, indicating that spray-drying approach is suitable for producing inhalable colistin powder formulation.     

Effect of Spray-Dried Particle Morphology on Mechanical and Flow Properties of Felodipine in PVP VA Amorphous Solid Dispersions

Amorphous solid dispersions (ASDs) are commonly used to enhance the oral absorption of drugs with solubility or dissolution rate limitations. Although the ASD formulation is typically constrained by physical stability and in vivo performance considerations, ASD particles can be engineered using the spray-drying process to influence mechanical and flow properties critical to tableting. Using the ASD formulation of 20% w/w felodipine dispersed in polyvinyl pyrrolidone vinyl acetate, spray-drying atomization and drying conditions were tuned to achieve 4 different powders with varying particle properties. The resulting particles ranged in volume moment mean diameter from 4 to 115 μm, bulk density from 0.05 to 0.38 g cm⁻³, and morphologies of intact, collapsed, and fractured hollow spheres. Powder flowability by shear cell ranged from poor to easy flowing, whereas mechanical property tests suggested all samples will produce strong tablets at reasonable solid fractions and compression pressures. In addition, Hiestand dynamic tableting indices showed excellent dynamic bonding for 3 powders, and low viscoelasticity with high brittleness for all powders. This work demonstrates the extent spray-dried ASD particle morphologies can be engineered to achieve desired powder flow and mechanical properties to mitigate downstream processing risks and increase process throughput.     

Biological characterization of rbSt oil suspensions

The low shear rheology of numerous rbSt sustained release oil suspensions was studied in order to assess the impact of formulation variables on product characteristics. A Haake CV 100 was used to obtain rheograms of rbSt suspensions in a Miglyol 812/Tween 80 vehicle as a function of drug concentration, drug particle shape and Tween 80 concentration. Rheograms of active formulations revealed a drug-Tween-Miglyol complex which increased in structure as a function of Tween 80 concentration. However, corresponding placebo formulations failed to show any significant change in Miglyol theology regardless of the Tween 80 concentration. The active formulations at 12.5% (w/v) rbSt showed increased deviation from Newtonian behavior as the Tween 80 concentration increased from 0 to 1.0% (w/v), but thixotropy was not apparent. Increasing the rbSt concentration to 24% (w/v) while keeping Tween 80 at 0.1% (w/v) caused slight thixotropy and a substantial deviation from Newtonian flow. The above tests were performed using a lot of spray-dried drug containing a high percentage of shattered particles. Further studies with a lot of spray-dried drug containing predominantly spherical particles showed similar theology. Oil suspensions made from lyophilized drug exhibited Newtonian behavior and minimal viscosity. Photomicrographs of the suspensions made with spray-dried drug revealed a dense population of small particles consistent with a high degree of structural rheology while those of the lyophilized drug suspensions showed an open network of overlapping platelet structures consistent with the minimal viscosity observed.     

A Spray-Dried Combination of Capreomycin and CPZEN-45 for Inhaled Tuberculosis Therapy

Tuberculosis (TB) remains the single most serious infectious disease attributable to a single-causative organism. A variety of drugs have been evaluated for pulmonary delivery as dry powders: capreomycin sulfate has shown efficacy and was safely delivered by inhalation at high doses to human volunteers, whereas CPZEN-45 is a new drug that has also been shown to kill resistant TB. The studies here combine these drugs—acting by different mechanisms—as components of single particles by spray-drying, yielding a new combination drug therapy. The spray-dried combination powder was prepared in an aerodynamic particle size range suitable for pulmonary delivery. Physicochemical storage stability was demonstrated for a period of 6 months. The spray-dried combination powders of capreomycin and CPZEN-45 have only moderate affinity for mucin, indicating that delivered drug will not be bound by these mucins in the lung and available for microbicidal effects. The pharmacokinetics of disposition in guinea pigs demonstrated high local concentrations of drug following direct administration to the lungs and subsequent systemic bioavailability. Further studies are required to demonstrate the in vivo efficacy of the combination to confirm the therapeutic potential of this novel combination.     

Optimization of the aerosolization properties of an inhalation dry powder based on selection of excipients

The aim of this study was to investigate the influence of formulation excipients on physical characteristics of inhalation dry powders prepared by spray-drying. The excipients used were a series of amino acids (glycine, alanine, leucine, isoleucine), trehalose and dipalmitoylphosphatidylcholine (DPPC). The particle diameter and the powder density were assessed by laser diffraction and tap density measurements, respectively. The aerosol behaviour of the powders was studied in a Multi-Stage Liquid Impinger. The nature and the relative proportion of the excipients affected the aerosol performance of the powders, mainly by altering powder tap density and degree of particle aggregation. The alanine/trehalose/DPPC (30/10/60 w/w/w) formulation showed optimal aerodynamic behaviour with a mass median aerodynamic diameter of 4.7 μm, an emitted dose of 94% and a fine particle fraction of 54% at an airflow rate of 100 L/min using a Spinhaler inhaler device. The powder had a tap density of 0.10 g/cm³. The particles were spherical with a granular surface and had a 4 μm volume median diameter. In conclusion, optimization of the aerosolization properties of inhalation dry powders could be achieved by appropriately selecting the composition of the particles.     

Optimization of the aerosolization properties of an inhalation dry powder based on selection of excipients

The aim of this study was to investigate the influence of formulation excipients on physical characteristics of inhalation dry powders prepared by spray-drying. The excipients used were a series of amino acids (glycine, alanine, leucine, isoleucine), trehalose and dipalmitoylphosphatidylcholine (DPPC). The particle diameter and the powder density were assessed by laser diffraction and tap density measurements, respectively. The aerosol behaviour of the powders was studied in a Multi-Stage Liquid Impinger. The nature and the relative proportion of the excipients affected the aerosol performance of the powders, mainly by altering powder tap density and degree of particle aggregation. The alanine/trehalose/DPPC (30/10/60 w/w/w) formulation showed optimal aerodynamic behaviour with a mass median aerodynamic diameter of 4.7 μm, an emitted dose of 94% and a fine particle fraction of 54% at an airflow rate of 100 L/min using a Spinhaler inhaler device. The powder had a tap density of 0.10 g/cm³. The particles were spherical with a granular surface and had a 4 μm volume median diameter. In conclusion, optimization of the aerosolization properties of inhalation dry powders could be achieved by appropriately selecting the composition of the particles.     

Aerosolization behavior of carrier-free L-leucine coated salbutamol sulphate powders

Aerosolization behavior of carrier-free l-leucine coated salbutamol sulphate inhalable powders has been studied. L-Leucine coatings were formed by physical vapour deposition (PVD) on the surface of the spherical particles in the gas phase. While depositing L-leucine formed pointy crystalline asperities whose size and density increased with the increased content of L-leucine in the gas phase. The asperity size changed from few nanometers to hundreds of nanometers. Due to the rough surface, all these coated fine powders were well-flowable and could be fed without the aid of coarser carriers. The aerosolization characteristics of the powders were studied with 'Inhalation Simulator' under ascending and fast inhalation profiles. When detected on-line by infrared light attenuation, the emission of the coated powders from an inhaler (Easyhaler) was distinctively dependent on the inhalation flow rate less than 30 l/min whereas that of micronized salbutamol sulphate powder solely depended on the studied inhalation flow rate range up to 100 l/min. Gravimetric measurements showed that emitted doses (ED) and fine particle fractions (FPF) of the coated powders were 5.1-7.1 mg/dose and 42-47%, respectively, which were 3-4 times higher than those of the micronized powder. The ED and FPF of the coated powders decreased as the surface roughness increased which is hypothesized as mechanical interlocking between the surface asperities.     

Enhanced dispersibility and deposition of spray-dried powders for pulmonary gene therapy

Spray-drying represents a viable alternative to freeze-drying for preparing dry powder dispersions for delivering macromolecules to the lung. The dispersibility of spray-dried powders is limited however, and needs to be enhanced to improve lung deposition and subsequent biological activity. In this study, we investigate the utility of leucine as a dry powder dispersibility enhancer when added prior to spray-drying a model non-viral gene therapy formulation (lipid:polycation:pDNA, LPD). Freeze-dried lactose-LPD, spray-dried lactose-LPD and spray-dried leucine-lactose-LPD powders were prepared. Scanning electron microscopy showed that leucine increased the surface roughness of spray-dried lactose particles. Particle size analysis revealed that leucine-containing spray-dried powders were unimodally dispersed with a mean particle diameter of 3.12 microm. Both gel electrophoresis and in vitro cell (A549) transfection showed that leucine may compromise the integrity and biological functionality of the gene therapy vector. The deposition of the leucine containing powder was however significantly enhanced as evidenced by an increase in gene expression mediated by dry powder collected at lower stages of a multistage liquid impinger (MSLI). Further studies are required to determine the potential of leucine as a ubiquitous dispersibility enhancer for a variety of pulmonary formulations.     

Protein Inhalation Powders: Spray Drying vs Spray Freeze Drying

Purpose. To develop a new technique, spray freeze drying, for preparing protein aerosol powders. Also, to compare the spray freeze-dried powders with spray-dried powders in terms of physical properties and aerosol performance. Methods. Protein powders were characterized using particle size analysis, thermogravimetric analysis, scanning electron microscopy, X-ray powder diffractometry, and specific surface area measurement. Aerosol performance of the powders was evaluated after blending with lactose carriers using a multi-stage liquid impinger or an Anderson cascade impactor. Two recombinant therapeutic proteins currently used for treating respiratory tract-related diseases, deoxyribonuclase (rhDNase) and anti-IgE monoclonal antibody (anti-IgE MAb), were employed and formulated with different carbohydrate excipients. Results. Through the same atomization but the different drying process, spray drying (SD) produced small (3 m), dense particles, but SFD resulted in large (8–10 m), porous particles. The fine particle fraction (FPF) of the spray freeze-dried powder was significantly better than that of the spray-dried powder, attributed to better aerodynamic properties. Powders collected from different stages of the cascade impactor were characterized, which confirmed the concept of aerodynamic particle size. Protein formulation played a major role in affecting the powder's aerosol performance, especially for the carbohydrate excipient of a high crystallization tendency. Conclusions. Spray freeze drying, as opposed to spray drying, produced protein particles with light and porous characteristics, which offered powders with superior aerosol performance due to favorable aerodynamic properties.     

Redispersible spray-dried lipid-core nanocapsules intended for oral delivery: the influence of the particle number on redispersibility

Abstract

This study proposes a new approach to produce easily redispersible spray-dried lipid-core nanocapsules (LNC) intended for oral administration, evaluating the influence of the particle number density of the fed sample. The proposed approach to develop redispersible spray-dried LNC formulations intended for oral route is innovative, evidencing the needing of an optimization of the initial particle number density in the liquid suspension of nanocapsules. A mixture of maltodextrin and L-leucine (90:10 w/w) was used as drying adjuvant. Dynamic light scattering, turbidimetry, determination of surface area and pore size distribution, electron microscopy and confocal Raman microscopy (CRM) were used to characterize the proposed system and to better understand the differences in the redispersion behavior. An easily aqueous redispersion of the spray-dried powder composed of maltodextrin and L-leucine (90:10 w/w) was obtained, depending on the particle number density. Their surface area decreased in the presence of LNC. CRM enabled the visualization of the spatial distribution of the different compounds in the powders affording to better understand the influence of the particle number density of the fed sample on their redispersion behavior. This study shows the need for optimizing initial particle number density in the liquid formulation to develop redispersible spray-dried LNC powders.     

New Co-Spray-Dried Tobramycin Nanoparticles-Clarithromycin Inhaled Powder Systems for Lung Infection Therapy in Cystic Fibrosis Patients

The aim of the study was to produce easily dispersible and porous agglomerates of tobramycin nanoparticles surrounded by a matrix composed of amorphous clarithromycin. Nanoparticles of tobramycin with a median particle size of about 400 nm were produced by high-pressure homogenisation. The results from the spray-dried powders showed that the presence of these nanoparticles enhanced powder dispersion during inhalation. Moreover, local drug deposition profiles were similar for the two antibiotics, allowing them to reach the target simultaneously. The dissolution-release profiles showed that tobramycin and clarithromycin might dissolve without any difficulties in the lung. The fine particle fraction increased from 35% and 31% for the physical blend for tobramycin and clarithromycin, respectively, to 63% and 62% for the spray-dried formulation containing nanoparticles. These new formulations, showing high lung deposition properties, even at sub-optimal inspiratory flow rates, represent a great possibility for advancing pulmonary drug administration and local therapy of lung infections.     

Leucine enhances aerosol performance of naringin dry powder and its activity on cystic fibrosis airway epithelial cells

The effect of different amino acids (AAs) on the aerosol performance of N spray-dried powders was studied. Morphology, size distribution, density, dissolution rate were evaluated and correlated to process parameters. The aerosol performance was analyzed by both Single Stage Glass Impinger and Andersen Cascade Impactor. Results indicated that powders containing 5% (w/w) of leucine, proline or histidine and dried from 3:7 ethanol/water feeds showed very satisfying aerodynamic properties with fine particle fraction>60%. Both neat N (raw and spray-dried) and N-leu1 dry-powder showing good aerodynamic properties were tested in cystic fibrosis (CF) and normal bronchial epithelial cells. Cell proliferation and expression levels of the key enzymes of the NF-κB and MAPK/ERK pathways, overactivated in CF cell lines, were evaluated. N-leu1 was able to significantly inhibit the expression levels of IKKα, IKKβ, as well as of the direct NF-κB inhibitor, IκBα. In addition N-Leu1 inhibited phosphorylation of ERK1/2 kinase and did not reduce cell proliferation as observed for the neat raw drug. Leucine co-spray-dried with the drug improved both aerodynamic properties and in vitro pharmacological activity of Naringin. The optimized N-Leu formulation as dry powder is potentially able to reduce hyperinflammatory status associated to CF.     

Spray-dried diclofenac-loaded poly(epsilon-caprolactone) nanocapsules and nanospheres. Preparation and physicochemical characterization

The aims of the present study were to prepare spray-dried polymeric nanocapsules (NC) and nanospheres (NS) from poly(epsilon-caprolactone) (P epsilon C) suspensions containing diclofenac (DIC) and to determine the physicochemical properties of the formulations. NC or NS suspensions were prepared by interfacial deposition of the polymer. DSC-thermograms of raw materials and NC or NS suspensions (evaporated or spray-dried) were obtained using a PL-DSC. Spray-dried powders were prepared by addition of 3% (w/v) Aerosil 200 into suspensions of NC or NS. These mixtures were fed into a spray-dryer. DIC was assayed by HPLC. NC and NS spray-dried powders were examined under SEM (Jeol Scanning Microscope, JSM-5800). NC and NS suspensions had acceptable diameter, 340 and 247 nm respectively. The yields of NC and NS spray-dried powders were 80% and 75% and the recovery of the DIC was 99% and 93%, respectively. The melting peak of P epsilon C in NC and NS was observed at a temperature about 10 degrees C lower than in the raw material. In the NC thermograms the maximum of the oil (Miglyol 810) melting peak (+1.6 degrees C) was lowered about 7 degrees C. For spray-dried NC formulations, the SEM analyses of powders showed spherical microparticles of silicon dioxide, covered by nanoparticles (300 nm), while for spray-dried NS formulations the microparticles presented a rugged surface at the same magnification.     

The Synergetic Effects of Nonpolar and Polar Protic Solvents on the Properties of Felodipine and Soluplus in Solutions,Casting Films,and Spray-Dried Solid Dispersions

The aim was to explore the effects of nonpolar and polar protic solvents composed of dichloromethane (DCM) and ethanol (EtOH) on the properties of felodipine (FLDP) and Soluplus in solutions, casting films, and spray-dried drug-rich or polymer-rich solid dispersions (SDs). Measurement of intrinsic viscosity and solubility indicated that FLDP and Soluplus were miscible. EtOH-DCM ranging from 20:80 to 50:50 induced the strongest molecular interactions for FLDP-Soluplus-solvents systems. Accordingly, the casting films and spray-dried powders of FLDP and Soluplus were prepared using pure EtOH or DCM and their mixtures as solvents. Polarized light microscopy, differential scanning calorimetry, Fourier transform infrared spectroscopy, in vitro dissolution tests, and stability have been conducted to characterize these films or spray-dried powders. EtOH-DCM (50:50) showed δ_H 2-3 MPa^1/2 higher than FLDP and Soluplus. It exhibited stronger inhibitory effects on phase separation and recrystallization of amorphous FLDP than pure DCM or EtOH in the drug-rich casting films, spray drying process, and spray-dried SDs exposure to 40°C/RH75% for 1 month. Higher ratio of Soluplus may offset the effects of solvents on the dissolution and stability of polymer-rich SDs. In conclusion, combination of nonpolar and polar protic solvents is of high potential for spray drying to optimize drug-rich SDs.     

Spray-dried amikacin sulphate powder for inhalation in cystic fibrosis patients: The role of ethanol in particle formation

A Central Composite Design (CCD) was applied in order to identify positive combinations of the production parameters of amikacin sulphate spray-dried powders for inhalation, with the intent to expand the experimental space defined in a previous half-fractional factorial design. Three factors, namely drying temperature, feed rate and ethanol proportion, have been selected out of the initial five. In addition, the levels of these factors were increased from two to three and their effect on amikacin respirability was evaluated. In particular, focus was given on the role of ethanol presence on the formation of the microparticles for inhalation.The overall outcome of the CCD was that amikacin respirability was not substantially improved, as the optimum region coincided with areas already explored with the fractional factorial design. However, expanding the design space towards smaller ethanol levels, including its complete absence, revealed the crucial role of this solvent on the morphology of the produced particles. Peclet number and drug solubility in the spraying solution helped to understand the formation mechanism of these amikacin sulphate spray-dried particles.