Novel Temperature Controlled Surface Dissolution of Excipient Particles for Carrier Based Dry Powder Inhaler Formulations

Spray-dried Pneumococcal Membrane Vesicles are Promising Candidates for Pulmonary Immunization

Pneumococcal infections represent a global health threat, which requires novel vaccine developments. Extracellular vesicles are secreted from most cells, including prokaryotes, and harbor virulence factors and antigens. Hence, bacterial membrane vesicles (MVs) may induce a protective immune response. For the first time, we formulate spray-dried gram-positive pneumococcal MVs-loaded vaccine microparticles using lactose/leucine as inert carriers to enhance their stability and delivery for pulmonary immunization. The optimized vaccine microparticles showed a mean particle size of 1-2µm, corrugated surface, and nanocrystalline nature. Their aerodynamic diameter of 2.34µm, average percentage emitted dose of 88.8%, and fine powder fraction 79.7%, demonstrated optimal flow properties for deep alveolar delivery using a next-generation impactor. Furthermore, confocal microscopy confirmed the successful encapsulation of pneumococcal MVs within the prepared microparticles. Human macrophage-like THP-1 cells displayed excellent viability, negligible cytotoxicity, and a rapid uptake around 60% of fluorescently labeled MVs after incubation with vaccine microparticles. Moreover, vaccine microparticles increased the release of pro-inflammatory cytokines tumor necrosis factor and interleukin-6 from primary human peripheral blood mononuclear cells. Vaccine microparticles exhibited excellent properties as promising vaccine candidates for pulmonary immunization and are optimal for further animal testing, scale-up and clinical translation.

Spherical agglomerates of lactose as potential carriers for inhalation

We report here on spherical lactose agglomerates as potential carriers for inhalation applications. Micromeritic properties of three spherical lactose agglomerates (SA-A, SA-B, SA-C) and a standard lactose inhalation grade carrier (Lactohale 100; LH100) were evaluated and compared. Ordered mixtures with micronized salbutamol sulfate as the model active pharmaceutical ingredient (API) and lactose carriers at two drug loadings (2 wt%, 5 wt%) were prepared, and in-vitro aerosolization performance was assessed. The spherical crystallization process led to particles with tailored micromeritic properties. These had larger specific surface area and greater fine fraction < 10 µm, compared to LH100, due to their coarse morphology. Their properties were reflected in the flowability parameters, where two types of spherical agglomerates of lactose showed more cohesive behavior compared to the other lactose grades. Blend uniformity showed improved homogeneous distribution of the API at higher drug load. In-vitro aerosolization tests showed that the spherical agglomerates of lactose enhanced the dose of API, compared to LH100. SA-B and SA-C showed significantly higher fine particle fractions at low drug load compared to the others, whereas overall, the largest fine particle fraction was for SA-B at high drug load. The carrier material attributes related to particle size, specific surface area, compressibility, flowability (cohesion, flow function), and air permeability were critical for aerosolization performance.

Liquid crystalline phase as a probe for crystal engineering of lactose: carrier for pulmonary drug delivery

The current work was undertaken to assess suitability of liquid crystalline phase for engineering of lactose crystals and their utility as a carrier in dry powder inhalation formulations. Saturated lactose solution was poured in molten glyceryl monooleate which subsequently transformed into gel. The gel microstructure was analyzed by PPL microscopy and SAXS. Lactose particles recovered from gels after 48 h were analyzed for polymorphism using techniques such as FTIR, XRD, DSC and TGA. Particle size, morphology and aerosolisation properties of prepared lactose were analyzed using Anderson cascade impactor. In situ seeding followed by growth of lactose crystals took place in gels with cubic microstructure as revealed by PPL microscopy and SAXS. Elongated (size ∼ 71 μm) lactose particles with smooth surface containing mixture of α and β-lactose was recovered from gel, however percentage of α-lactose was more as compared to β-lactose. The aerosolisation parameters such as RD, ED, %FPF and % recovery of lactose recovered from gel (LPL) were found to be comparable to Respitose® ML001. Thus LC phase (cubic) can be used for engineering of lactose crystals so as to obtain particles with smooth surface, high elongation ratio and further they can be used as carrier in DPI formulations.

Effect of processing history on the surface interfacial properties of budesonide in carrier-based dry-powder inhalers

Influence of air-jet micronization, post-micronization conditioning and storage on the surface properties of budesonide in dry-powder inhaler formulations was investigated. Crystalline budesonide was air jet-micronized and conditioned using organic vapor. Particle engineering was also used to fabricate respirable particles of budesonide. Surface imaging by atomic force microscopy suggested that micronized material possessed process-induced surface disorder, which relaxed upon conditioning with organic vapor. Particle engineered material was devoid of such surface disorder. Surface interfacial properties of all batches were different and correlated to in vitro fine particle delivery. The surface properties and in vitro performance of the conditioned material changed upon storage of the budesonide at 44% relative humidity and 25°C, while the micronized and particle-engineered material remained stable. These data suggest that processing conditions of budesonide affected the surface properties of the material, which was demonstrated to have direct affect on dry-powder inhaler formulation performance.

Spray dried mannitol carrier particles with tailored surface properties--the influence of carrier surface roughness and shape

The aim of this work was to study the performance of mannitol carrier particles of tailored surface roughness in dry powder inhaler formulations. Carrier particles of different surface roughness were prepared by spray drying of aqueous mannitol solutions at different outlet temperatures at a pilot-scale spray dryer. However, the carrier particles did not only change in surface roughness but also in shape. This is why the impact of carrier shape on the performance of carrier based dry powder inhalates was evaluated also. The highest fine particle fraction (FPF), that is the amount of active pharmaceutical substance, delivered to the deep lung, is achieved when using rough, spherical carrier particles (FPF=29.23 ± 4.73%, mean arithmetic average surface roughness (mean R(a))=140.33 ± 27.75 nm, aspect ratio=0.925). A decrease of surface roughness (mean R(a)=88.73 ± 22.25 nm) leads to lower FPFs (FPF=14.62 ± 1.18%, aspect ratio=0.918). The FPF further decreases when irregular shaped particles are used. For those particles, the micronized active accumulates within the cavities of the carrier surface during the preparation of the powder mixtures. Upon inhalation, the cavities may protect the active from being detached from the carrier.

Physico-chemical aspects of lactose for inhalation

A dry powder inhaler (DPI) is a dosage form that consists of a powder formulation in a device which is designed to deliver an active ingredient to the respiratory tract. It has been extensively investigated over the past years and several aspects relating to device and particulate delivery mechanisms have been the focal points for debate. DPI formulations may or may not contain carrier particles but whenever a carrier is included in a commercial formulation, it is almost invariably lactose monohydrate. Many physicochemical properties of the lactose carrier particles have been reported to affect the efficiency of a DPI. A number of preparation methods have been developed which have been claimed to produce lactose carriers with characteristics which lead to improved deposition. Alongside these developments, a number of characterization methods have been developed which have been reported to be useful in the measurement of key properties of the particulate ingredients. This review describes the various physicochemical characteristics of lactose, methods of manufacturing lactose particulates and their characterization.

Lactose characteristics and the generation of the aerosol

The delivery efficiency of dry-powder products for inhalation is dependent upon the drug formulation, the inhaler device, and the inhalation technique. Dry powder formulations are generally produced by mixing the micronised drug particles with larger carrier particles. These carrier particles are commonly lactose. The aerosol performance of a powder is highly dependent on the lactose characteristics, such as particle size distribution and shape and surface properties. Because lactose is the main component in these formulations, its selection is a crucial determinant of drug deposition into the lung, as interparticle forces may be affected by the carrier-particle properties. Therefore, the purpose of this article is to review the various grades of lactose, their production, and the methods of their characterisation. The origin of their adhesive and cohesive forces and their influence on aerosol generation are described, and the impact of the physicochemical properties of lactose on carrier-drug dispersion is discussed in detail.

Improved aerosolization performance of salbutamol sulfate formulated with lactose crystallized from binary mixtures of ethanol-acetone

It has been shown that dry powder inhaler (DPI) formulations typically achieve low fine particle fractions (poor performance). A commonly held theory is that this is due, at least in part, to low levels of detachment of drug from lactose during aerosolization as a result of strong adhesion of drug particles to the carrier surfaces. Therefore, the purpose of the present study is to overcome poor aerosolization performance of DPI formulation by modification of lactose particles. Lactose particles were crystallized by adding solution in water to different ratios of binary mixtures of ethanol-acetone. The results showed that modified lactose particles had exceptional aerosolization performance that makes them superior to commercial lactose particles. Morphology assessment showed that crystallized lactose particles were less elongated, more irregular in shape, and composed of smaller primary lactose particles compared with commercial lactose. Solid-state characterization showed that commercial lactose particles were α-lactose monohydrate, whereas crystallized lactose particles were a mixture of α-lactose monohydrate and β-lactose according to the ratio of ethanol-acetone used during crystallization process. The enhanced performance could be mainly due to rougher surface and/or higher amounts of fines compared with the lactose crystallized from pure ethanol or commercial lactose.

Engineering of crystalline combination inhalation particles of a long-acting beta2-agonist and a corticosteroid

PURPOSE

Engineering of inhalation particles incorporating, in each individual particle, a combination of a long-acting beta-agonist and a glucocorticosteroid in a pre-determined and constant ratio for delivery via a dry powder inhaler (DPI).

METHODS

Individual crystalline particles containing both the glucocorticosteroid fluticasone propionate (FP) and long-acting beta-agonist salmeterol (SX) were prepared, in a ratio of 10:1, using the solution atomization and crystallization by sonication (SAX) process. Combination drug particles were characterized by particle size, morphology, crystallinity and aerosolisation efficiency using inertial impaction.

RESULTS

Combination drug particles were spherical and crystalline, with a median diameter of 4.68 +/- 0.01 microm. Aerosolisation of formulations containing combination drug particles resulted in greater uniformity in delivery ratios of both actives across all stages of the impactor before and after storage.

CONCLUSIONS

Actives in a pre-determined dose ratio can be crystallised in a single particle using the SAX process.

Effective modification of particle surface properties using ultrasonic water mist

The goal of the present study was to design a new technique to modify particle surface properties and, through that, to improve flowability of poorly flowing drug thiamine hydrochloride and pharmaceutical sugar lactose monohydrate of two different grades. The powdered particles were supplied by a vibratory feeder and exposed to an instantaneous effect of water mist generated from an ultrasound nebulizer. The processed and original powders were evaluated with respect to morphology (scanning electron microscopy, atomic force microscopy, and spatial filtering technique), flow, and solid state properties. It was found that rapid exposition of pharmaceutical materials by water mist resulted in the improvement of powder technical properties. The evident changes in flowability of coarser lactose were obviously due to smoothing of particle surface and decreasing in the level of fines with very slight increment in particle size. The changes in thiamine powder flow were mainly due to narrowing in particle size distribution where the tendency for better flow of finer lactose was related to surface and size modifications. The aqueous mist application did not cause any alteration of the crystal structures of the studied materials. The proposed water mist treatment technique appears to be a robust, rapid, and promising tool for the improvement of the technological properties of pharmaceutical powders.

Lactose composite carriers for respiratory delivery

PURPOSE

Lactose dry powder inhaler (DPI) carriers, constructed of smaller sub units (composite carriers), were evaluated to assess their potential for minimising drug-carrier adhesion, variability in drug-carrier forces and influence on drug aerosol performance from carrier-drug blends.

METHODS

Lactose carrier particles were prepared by fusing sub units of lactose (either 2, 6 or 10 microm) in saturated lactose slurry. The resultant composite particles, as well as supplied lactose, were sieve fractioned to obtain a 63-90 microm carriers. The carriers were evaluated in terms of size (laser diffraction) morphology (electron microscopy and atomic force microscopy), crystallinity and drug adhesion (colloid probe microscopy). In addition, blends containing drug and carrier were prepared and evaluated in terms of drug aerosol performance.

RESULTS

The surface morphology and physico-chemical properties of the composite carriers were significantly different. Depending on the initial primary lactose size, the composite particles could be prepared with different surface roughness. Variation in composite roughness could be related to the change in drug adhesion (via modification in contact geometry) and thus drug aerosol performance from drug-lactose blends.

CONCLUSION

Composite based carriers are a potential route to control drug-carrier adhesion forces and variability thus allowing more precise control of formulation performance.

Scanning white-light interferometry as a novel technique to quantify the surface roughness of micron-sized particles for inhalation

A novel approach of measuring the surface roughness of spherical and flat micron-sized drug particles using scanning white-light interferometry was applied to investigate the surface morphology of micron-sized active pharmaceutical ingredients (APIs) and excipient particles used for inhalation aerosols. Bovine serum albumin (BSA) and alpha-lactose monohydrate particles were chosen as model API and excipient particles, respectively. Both BSA and lactose particles were prepared with different degrees of surface corrugation using either controlled spray drying (four samples of BSA) or decantation (two samples of lactose). Particle size distributions were characterized by laser diffraction, and particles were imaged by scanning electron microscopy (SEM). Surface roughness of the BSA and lactose particles was quantified by white-light optical profilometry using vertical scanning interferometry (VSI) at full resolution using a 50x objective lens with 2.0x and 0.5x fields of view for BSA and lactose, respectively. Data were analyzed using Vision software (version 32, WYKO), and surface roughness values are expressed as root-mean-square roughness ( Rrms). Furthermore, data were compared to topographical measurements made using conventional atomic force microscopy. Analysis of the optical profilometry data showed significant variation in BSA roughness ranging from 18.58 +/- 3.80 nm to 110.90 +/- 13.16 nm for the smoothest and roughest BSA particles, respectively, and from 81.20 +/- 15.90 nm to 229.20 +/- 68.20 nm for decanted and normal lactose, respectively. The Rrms values were in good agreement with the AFM-derived values. The particle morphology was similar to SEM and AFM images. In conclusion, scanning white-light interferometry provides a useful complementary tool for rapid evaluation of surface morphology and roughness in particles used for dry powder inhalation formulation.

Continued Investigation Into the Influence of Loaded Dose on the Performance of Dry Powder Inhalers: Surface Smoothing Effects

The aerosolization of salbutamol sulfate, measured as fine particle dose (FPD LD) and fine particle fraction (FPF LD) (<6.4 microm mass median aerodynamic diameter), from two sieved (63-90 microm) lactose monohydrate carriers, one as supplied, one smoothed by controlled surface dissolution, was studied. In general, no significant variation in FPD LD was observed at drug loadings between 10 and 63.5 microg and 10 and 135 microg for the surface dissolved and as supplied lactose monohydrates, respectively. Increasing the drug load above these levels resulted in linear increases in FPD LD with increasing drug load with the surface dissolved lactose monohydrate exhibiting higher FPD LD and FPF LD. This suggests that, at lower drug loadings, areas of the carrier exhibiting higher adhesion, so-called active sites, were being preferentially occupied and filled. Since there was no evidence of drug agglomeration using scanning electron microscopy, the observations suggest that the number and range of such higher energy "active sites" can be reduced by modifying the surface roughness, that is, energies, of the carrier.

Physical characterization of component particles included in dry powder inhalers. II. Dynamic characteristics

Characteristics of particles included in dry powder inhalers is extended from our previous report (in this journal) to include properties related to their dynamic performance. The performance of dry powder aerosols for pulmonary delivery is known to depend on fluidization and dispersion which reflects particle interactions in static powder beds. Since the solid state, surface/interfacial chemistry and static bulk properties were assessed previously, it remains to describe dynamic performance with a view to interpreting the integrated database. These studies result in complex data matrices from which correlations between specific properties and performance may be deduced. Lactose particles were characterized in terms of their dynamic flow, powder and aerosol electrostatics, and aerodynamic performance with respect to albuterol aerosol dispersion. There were clear correlations between flow properties and aerosol dispersion that would allow selection of lactose particles for formulation. Moreover, these properties can be related to data reported earlier on the morphological and surface properties of the carrier lactose particles. The proposed series of analytical approaches to the evaluation of powders for inclusion in aerosol products has merit and may be the basis for screening and ultimately predicting particle performance with a view to formulation optimization.