Formulating Inhalable Dry Powders Using Two-Fluid and Three-Fluid Nozzle Spray Drying

Purpose

The spray drying process is widely applied for pharmaceutical particle engineering. The purpose of this study was to investigate advantages and disadvantages of two-fluid nozzle and three-fluid nozzle spray drying processes to formulate inhalable dry powders.

Methods

Budesonide nanocomposite microparticles (BNMs) were prepared by co-spray drying of budesonide nanocrystals suspended in an aqueous mannitol solution by using a two-fluid nozzle spray drying process. Budesonide-mannitol microparticles (BMMs) were prepared by concomitant spray drying of a budesonide solution and an aqueous mannitol solution using a spray drier equipped with a three-fluid nozzle. The resulting dry powders were characterized by using X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and Raman microscopy. A Next Generation Impactor was used to evaluate the aerodynamic performance of the dry powders.

Results

XRPD and DMA results showed that budesonide remained crystalline in the BNMs, whereas budesonide was amorphous in the BMMs. Spray drying of mannitol into microparticles resulted in a crystalline transformation of mannitol, evident from XRPD, DSC and Raman spectroscopy analyses. Both BMMs and BNMs displayed a faster dissolution rate than bulk budesonide. The yield of BNMs was higher than that of BMMs. The mass ratio between budesonide and mannitol was preserved in the BNMs, whereas the mass ratio in the BMMs was higher than the theoretical ratio.

Conclusions

Spray drying is an enabling technique for preparation of budesonide amorphous solid dispersions and nanocrystal-embedded microparticles. Two-fluid nozzle spray drying is superior to three-fluid nozzle spray drying in terms of yield.

     

Freeze-Dried Mannitol for Superior Pulmonary Drug Delivery via Dry Powder Inhaler

Purpose

To show for the first time the superior dry powder inhaler (DPI) performance of freeze dried mannitol in comparison to spray dried mannitol and commercial mannitol.

Methods

Different mannitol powders were sieved to collect 63–90 μm particles and then analyzed in terms of size, shape, surface morphology, solid state, density, flowability. Salbutamol sulphate-mannitol aerosol formulations were evaluated in terms of homogeneity, SS-mannitol adhesion, and in vitro aerosolization performance.

Results

Freeze dried mannitol demonstrated superior DPI performance with a fine particle fraction believed to be highest so far reported in literature for salbutamol sulphate under similar protocols (FPF?=?46.9%). To lesser extent, spray dried mannitol produced better aerosolization performance than commercial mannitol. Freeze dried mannitol demonstrated elongated morphology, α-+β-+δ- polymorphic forms, and poor flowability whereas spray dried mannitol demonstrated spherical morphology, α-+β- polymorphic forms, and excellent flowability. Commercial mannitol demonstrated angular morphology, β- polymorphic form, and good flowability. Freeze dried mannitol demonstrated smoother surface than spray dried mannitol which in turn demonstrated smoother surface than commercial mannitol. FPF of SS increased as mannitol powder porosity increase.

Conclusions

Freeze drying under controlled conditions can be used as a potential technique to generate aerodynamically light mannitol particles for superior DPI performance.     

Production of Inhalation Phage Powders Using Spray Freeze Drying and Spray Drying Techniques for Treatment of Respiratory Infections

Purpose

The potential of aerosol phage therapy for treating lung infections has been demonstrated in animal models and clinical studies. This work compared the performance of two dry powder formation techniques, spray freeze drying (SFD) and spray drying (SD), in producing inhalable phage powders.

Method

A Pseudomonas podoviridae phage, PEV2, was incorporated into multi-component formulation systems consisting of trehalose, mannitol and L-leucine (F1?=?60:20:20 and F2?=?40:40:20). The phage titer loss after the SFD and SD processes and in vitro aerosol performance of the produced powders were assessed.

Results

A significant titer loss (~2 log) was noted for droplet generation using an ultrasonic nozzle employed in the SFD method, but the conventional two-fluid nozzle used in the SD method was less destructive for the phage (~0.75 log loss). The phage were more vulnerable during the evaporative drying process (~0.75 log further loss) compared with the freeze drying step, which caused negligible phage loss. In vitro aerosol performance showed that the SFD powders (~80% phage recovery) provided better phage protection than the SD powders (~20% phage recovery) during the aerosolization process. Despite this, higher total lung doses were obtained for the SD formulations (SD-F1?=?13.1?±?1.7?×?10⁴ pfu and SD-F2?=?11.0?±?1.4?×?10⁴ pfu) than from their counterpart SFD formulations (SFD-F1?=?8.3?±?1.8?×?10⁴ pfu and SFD-F2?=?2.1?±?0.3?×?10⁴ pfu).

Conclusion

Overall, the SD method caused less phage reduction during the powder formation process and the resulted powders achieved better aerosol performance for PEV2.

     

Rapid Lymph Accumulation of Polystyrene Nanoparticles Following Pulmonary Administration

Purpose

Pulmonary administration of polymeric nanoparticle drug delivery systems is of great interest for both systemic and local therapies. However, little is understood about the relationship of particle size and pulmonary absorption. We investigated uptake and biodistribution of polystyrene nanoparticles (PN) of 50 nm, 100 nm, 250 nm, and 900 nm diameters in mice following administration to lungs via pharyngeal aspiration.

Methods

The amount of PN in tissues was analyzed by gel permeation chromatography (GPC).

Results

At 1 h, larger diameter PN (250 nm and 900 nm) had the highest total uptake at around 15% of administered dose, whereas the smaller diameter PN (50 nm and 100 nm) had uptake of only 5–6%. However, at 3 h, the 50 nm PN had the highest total uptake at 24.4%. For each size tested, the highest nanoparticle deposition was observed in the lymph nodes (LN) as compared to other tissues accounting for a total of about 35–50% of absorbed nanoparticles.

Conclusion

PN size impacts the rate and extent of uptake from lungs and, further, the extent of LN deposition. The extent of uptake and lymph distribution of the model, non-degradable PN lends potential to pulmonary administered, biodegradable polymeric nanoparticles for delivery of therapeutics to regional lymph nodes.     

Towards a More Desirable Dry Powder Inhaler Formulation: Large Spray-Dried Mannitol Microspheres Outperform Small Microspheres

Purpose

To investigate, for the first time, the performance of a dry powder inhaler (DPI, Aerolizer^®) in the case of a model drug (i.e. albuterol sulphate) formulated with spray dried mannitol carrier particles with homogeneous shape and solid–state form but different sizes.

Methods

Spray dried mannitol (SDM) particles were characterized in terms of size, surface area, morphology, water content, solid–state, density and electrostatic charge by a novel approach. DPI formulations composed of SDM and albuterol sulphate (AS) were prepared and evaluated in terms of drug content homogeneity and in vitro aerosolization performance.

Results

All SDM particles generated similar fine particle fractions of AS. Formulations consisting of larger SDM particles demonstrated better drug content homogeneity, reduced amounts of drug loss and reduced oropharyngeal deposition. Comparing different SDM products demonstrated that SDM powders with relatively poorer flowability, wider size distributions and higher charge density generated DPI formulations with poorer drug content homogeneity and deposited higher amount of drug on the inhaler, mouthpiece adaptor and throat. DPI formulation total desirability increased linearly with the mean diameter of SDM.

Conclusion

Particle shape and solid–state form of mannitol could dominate over carrier size, bulk density, flowability and charge in terms of determining the aerosolization behaviour of AS formulated with mannitol carrier, at least within the experimental protocols applied in the present study.     

Stabilization of Live Attenuated Influenza Vaccines by Freeze Drying,Spray Drying,and Foam Drying

Purpose

The goal of this research is to develop stable formulations for live attenuated influenza vaccines (LAIV) by employing the drying methods freeze drying, spray drying, and foam drying.

Methods

Formulated live attenuated Type-A H1N1 and B-strain influenza vaccines with a variety of excipient combinations were dried using one of the three drying methods. Process and storage stability at 4, 25 and 37°C of the LAIV in these formulations was monitored using a TCID₅₀ potency assay. Their immunogenicity was also evaluated in a ferret model.

Results

The thermal stability of H1N1 vaccine was significantly enhanced through application of unique formulation combinations and drying processes. Foam dried formulations were as much as an order of magnitude more stable than either spray dried or freeze dried formulations, while exhibiting low process loss and full retention of immunogenicity. Based on long-term stability data, foam dried formulations exhibited a shelf life at 4, 25 and 37°C of >2, 1.5 years and 4.5 months, respectively. Foam dried LAIV Type-B manufactured using the same formulation and process parameters as H1N1 were imparted with a similar level of stability.

Conclusion

Foam drying processing methods with appropriate selection of formulation components can produce an order of magnitude improvement in LAIV stability over other drying methods.

     

New Respirable and Fast Dissolving Itraconazole Dry Powder Composition for the Treatment of Invasive Pulmonary Aspergillosis

Purpose

Novel itraconazole (ITZ)-based dry powders for inhalation (DPI) were optimized for aerodynamic and dissolution properties and contained excipients that are acceptable for inhalation.

Methods

The DPI were produced by spray drying solutions. The drug content, crystallinity state, and morphological evaluation of the dry powders were determined by high performance liquid chromatography, powder X-ray diffraction, differential scanning calorimetry, and scanning electron microscopy, respectively. A particle size analysis was conducted using laser light scattering. The aerodynamic behaviors of the powders were characterized by impaction tests. ITZ dissolution rates were evaluated using a dissolution method adapted to inhaled products.

Results

The DPI presented very high fine particle fractions that ranged from 46.9% to 67.0% of the nominal dose. The formulations showed very fast dissolution rates compared to unformulated crystalline ITZ with the possibility of modulating the dissolution rate by varying the quantity of phospholipids (PL) incorporated. ITZ remained amorphous while the mannitol was crystalline. The α, β and δ-mannitol polymorph ratios varied depending on the formulation compositions.

Conclusion

This formulation strategy could be an attractive alternative for treating invasive pulmonary aspergillosis. The ITZ and PL content are key characteristics because of their influence on the dissolution rate and aerosol performance.     

In Vitro Efficacy of Polysaccharide-Based Nanoparticles Containing Disease-Modifying Antirheumatic Drugs

Purpose

To evaluate the therapeutic efficacy of dexamethasone (DM) and methotrexate (MTX) entrapped within polysialic acid (PSA)-trimethyl chitosan (TMC) nanoparticles using an in vitro model of rheumatoid arthritis (RA).

Methods

The loading capacity of the PSA-TMC nanoparticles was determined. An RA in vitro model was developed by stimulating a synovial cell line with a proinflammatory mediator. Multiplex immunoassay was used to determine changes in the secretion of interleukin-6 (IL-6), interleukin-8 (IL-8), and granulocyte-macrophage colony-stimulating factor (GM-CSF) by the in vitro model following administration of the DM- and MTX-loaded nanoparticles.

Results

The loading capacity of the PSA-TMC nanoparticles was approximately 0.1 mg of drug/mg of nanoparticle. When applied to our in vitro model of RA, there were no significant differences in the concentrations of IL-6 and IL-8 when comparing the free drugs and drug-loaded nanoparticles, administered at concentration of 0.1 mg/ml and 1.0 mg/ml, respectively.

Conclusions

The present study verified that MTX and DM are able to retain bioactivity when loaded into PSA-TMC nanoparticles. Although in vitro efficacy was not increased, the in vivo efficacy will likely be enhanced by the site-specific targeting conferred by nanoparticle entrapment.     

Up-regulating Blood Brain Barrier Permeability of Nanoparticles via Multivalent Effect

Purpose

To investigate the multivalent effect for up-regulating the intracerebral delivery of nanoparticles via receptor-mediated transcytosis.

Methods

Nanoparticles labeled with near-infrared (NIR) fluorophore and different numbers of angiopep-2 peptides that specifically target low-density lipoprotein receptor-related protein (LRP) on the brain capillary endothelial cells were developed. Bio-distribution studies quantified the intracerebral uptakes of these nanoparticles at 2 and 24 h after intravenous injection. In vivo NIR fluorescence imaging, ex vivo autoradiographic imaging and 3D reconstructed NIR fluorescence imaging revealed the nanoparticle distribution pattern in brain. Fluorescence microscopic imaging identified the nanoparticle locations at the cellular level.

Results

The multimetirc association between the angiopep-2 peptides labeled on the nanoparticle and the LRP receptors on the brain capillary endothelial cells significantly increased the intracerebral uptake of the nanoparticles. Nanoparticle Den-Angio4 labeled four angiopep-2 peptides achieved the highest BBB traverse efficacy. After penetrating the BBB, Den-Angio4 distributed heterogeneously and mainly located at hippocampus, striatum and cerebellum in the brains.

Conclusions

The multivalent effect significantly enhances the BBB permeability of nanoparticles. Den-Angio4 as a nanoparticle prototype provides a two order targeted strategy for diagnosis or treatment of central nerver system diseases by first traversing the BBB via receptor-mediated endocytosis and secondly targeting the leisions with high receptor expression level.     

Novel Spray-Dried Genipin-Crosslinked Casein Nanoparticles for Prolonged Release of Alfuzosin Hydrochloride

Purpose

To propose a simple method for the development of genipin-crosslinked casein micelles as a new delivery platform for prolonged release of alfuzosin hydrochloride.

Methods

Crosslinked casein micelles entrapping alfuzosin were transformed into solid redispersible nanoparticles via spray-drying technique with no need for drying adjuvants based on the stabilizing effect of casein.

Results

The nanoparticles displayed high production yields (86.99–94.63% w/w) with a reasonable drug incorporation efficiency ranged from 92.86 to 97.75%. The nanoparticles were readily reconstituted in aqueous solution with a particle size range of 122.1–260.0 nm and a zeta potential range of ?21.6 to ?36.6 mV indicating a good colloidal stability. No drug crystals were detectable in the scanning electron micrographs revealing successful encapsulation of alfuzosin into casein nanoparticles which was confirmed by differential scanning calorimetry. The nanoparticles succeeded in prolonging the drug release that could be controlled by modulating the genipin crosslinking degree. The release data showed a good fit into Higuchi release kinetics with non-Fickian type of drug diffusion.

Conclusions

These results demonstrated that genipin-crosslinking combined with spray-drying technique could be used as a promising tool to develop solid redispersible casein nanoparticles with sustained drug release properties.     

Engineered Andrographolide Nanoparticles Mitigate Paracetamol Hepatotoxicity in Mice

Purpose

Paracetamol (acetaminophen, APAP) overdose is often fatal due to progressive and irreversible hepatic necrosis. The aim of this work was to design Andrographolide (AG) loaded nanoparticles to prevent similar hepatic necrosis.

Methods

Functionalized AG-loaded PLGA nanoparticles carrying different densities of heparin were prepared following a facile emulsion solvent evaporation technique. Nanoparticle morphology, loading and release kinetics were studied. Hepatic localization of the nanoparticles was investigated in both normal and APAP damaged conditions using FITC fluorescent probe. Different serum parameters and liver histopathology were further examined as indicators of hepatic condition before and after treatment.

Result

A collection of heparin functionalized AG-loaded PLGA nanoparticles were designed. Low amount of heparin on the particle surface could rapidly localize the nanoparticles up to the liver. The new functionalized AG nanoparticles affect efficient hepatoprotection in experimental mouse APAP overdose conditions. AG nanoparticle hepatoprotection was due to the rapid regeneration of antioxidant capacity and hepatic GSH store.

Conclusions

Engineered nanoparticles loaded with AG provided a fast protection in APAP induced acute liver failure.     

Respirable Low-Density Microparticles Formed In Situ from Aerosolized Brittle Matrices

Purpose

Inhalation of low-density porous particles enables deep lung delivery with less dependence on device design and patient inspiration. The purpose of this study was to implement Thin Film Freezing (TFF) to investigate a novel approach to dry powder inhalation.

Methods

Powders produced by TFF were evaluated for aerodynamic and geometric particle size by cascade impaction and laser light scattering, respectively. Density measurements were conducted according to USP methods and calculated using data from particle size measurements. Excipient inclusion and its effect on moisture sorption was measured by Dynamic Vapor Sorption (DVS).

Results

TFF-produced brittle matrix powders were sheared apart into respirable microparticles using a passive DPI device, producing fine particle fractions (FPF) up to 69% and mass median aerodynamic diameters (MMAD) as low as 2.6 μm. Particles had a mean geometric diameter ranging from 25 μm to 50 μm and mass densities of approximately 0.01 g/cm³. Powders were susceptible to moisture-induced matrix collapse, capillary forces and electrostatic charging; although formulations containing mannitol or no sugar excipient proved to be more robust.

Conclusions

Aerosolized brittle matrices produced by TFF may prove to be a useful platform for highly efficient pulmonary delivery of thermally labile, highly potent, and poorly soluble drugs.     

Pulmonary Gene Silencing in Transgenic EGFP Mice Using Aerosolised Chitosan/siRNA Nanoparticles

Purpose

This work describes the production and application of an aerosolised formulation of chitosan nanoparticles for improved pulmonary siRNA delivery and gene silencing in mice.

Methods

Aerosolised chitosan/siRNA nanoparticles were pneumatically formed using a nebulising catheter and sized by laser diffraction. In vitro silencing of aerosolised and non-aerosolised formulations was evaluated in an EGFP endogenous-expressing H1299 cell line by flow cytometry. Non-invasive intratracheal insertion of the catheter was used to study nanoparticle deposition by histological detection of Cy3-labeled siRNA and gene silencing in transgenic EGFP mouse lungs using a flow cytometric method.

Results

Flow cytometric analysis demonstrated minimal alteration in gene silencing efficiency before (68%) and after (62%) aerosolisation in EGFP-expressing H1299 cells. Intratracheal catheter administration in mice resulted in nanoparticle deposition throughout the entire lung in both alveoli and bronchiolar regions using low amounts of siRNA. Transgenic EGFP mice dosed with the aerosolised nanoparticle formulation showed significant EGFP gene silencing (68% reduction compared to mismatch group).

Conclusions

This work provides a technology platform for effective pulmonary delivery and gene silencing of RNAi therapeutics with potential use in preclinical studies of respiratory disease treatment.     

Spray-Dried Chitosan Microparticles for Cellular Delivery of an Antigenic Protein: Physico-chemical Properties and Cellular Uptake by Dendritic Cells and Macrophages

Purpose

Spray-dried chitosan microparticles for cellular delivery of antigen to dendritic cells (DC) and macrophages (M?) were investigated.

Methods

Chitosan microparticles were prepared by spray drying. For comparison, poly(lactic-co-glycolic acid) (PLGA) and poly(α-butyl cyanoacrylate) (BCA) micro-/nanoparticles were generated. Bovine serum albumin (BSA) was used as a model antigen. The particles were characterized in terms of size, morphology, surface charge, surface composition, protein content, entrapment efficiency, in vitro release, and protein integrity. Additionally, they were subject to cell viability and cellular uptake study with DC and M?.

Results

Size of chitosan, PLGA, and BCA micro-/nanoparticles ranged between 3.11–7.18, 0.94–6.26, and 0.30–6.34 μm, respectively. Particle morphology and in vitro protein release varied, depending on polymer type, particle composition and preparation process parameters. Chitosan microparticles were cationic, while PLGA microparticles were neutral. BCA micro-/nanoparticles were either anionic or cationic, according to polymerization pH. Protein content and entrapment efficiency of chitosan and PLGA microparticles were relatively consistent. Only integrity and conformational structure of protein encapsulated in chitosan microparticles were completely retained. Chitosan and PLGA microparticles were non-toxic to DC and M?, but the former were internalized more efficiently.

Conclusions

Spray-dried chitosan microparticles delivered the antigen efficiently to DC and M?.     

Synthesis and Characterization of Nanocomposite Microparticles (nCmP) for the Treatment of Cystic Fibrosis-Related Infections

Purpose

Pulmonary antibiotic delivery is recommended as maintenance therapy for cystic fibrosis (CF) patients who experience chronic infections. However, abnormally thick and sticky mucus present in the respiratory tract of CF patients impairs mucus penetration and limits the efficacy of inhaled antibiotics. To overcome the obstacles of pulmonary antibiotic delivery, we have developed nanocomposite microparticles (nCmP) for the inhalation application of antibiotics in the form of dry powder aerosols.

Methods

Azithromycin-loaded and rapamycin-loaded polymeric nanoparticles (NP) were prepared via nanoprecipitation and nCmP were prepared by spray drying and the physicochemical characteristics were evaluated.

Results

The nanoparticles were 200 nm in diameter both before loading into and after redispersion from nCmP. The NP exhibited smooth, spherical morphology and the nCmP were corrugated spheres about 1 μm in diameter. Both drugs were successfully encapsulated into the NP and were released in a sustained manner. The NP were successfully loaded into nCmP with favorable encapsulation efficacy. All materials were stable at manufacturing and storage conditions and nCmP were in an amorphous state after spray drying. nCmP demonstrated desirable aerosol dispersion characteristics, allowing them to deposit into the deep lung regions for effective drug delivery.

Conclusions

The described nCmP have the potential to overcome mucus-limited pulmonary delivery of antibiotics.

     

Effect of Nanoparticle Surface on the HPLC Elution Profile of Liposomal Nanoparticles

Purpose

Nanoparticles have been used in diverse areas, and even broader applications are expected in the future. Since surface modification can influence the configuration and toxicity of nanoparticles, a rapid screening method is important to ensure nanoparticle quality.

Methods

We examined the effect of the nanoparticle surface morphology on the HPLC elution profile using two types of 100-nm liposomal nanoparticles (AmBisome^? and DOXIL^?).

Results

These 100-nm-sized nanoparticles eluted before the holdup time (about 4 min), even when a column packed with particles with a relatively large pore size (30 nm) was used. The elution time of the nanoparticles increased with pegylation of the nanoparticles and protein adsorption to the nanoparticles; however, the nanoparticles still eluted before the holdup time.

Conclusions

The results of this study indicate that HPLC is a suitable tool for rapid evaluation of the surface of liposomal nanoparticles.

     

Surface Analysis of PEGylated Nano-Shields on Nanoparticles Installed by Hydrophobic Anchors

Purpose

This work describes a method for functionalisation of nanoparticle surfaces with hydrophilic “nano-shields” and the application of advanced surface characterisation to determine PEG amount and accumulation at the outmost 10 nm surface that is the predominant factor in determining protein and cellular interactions.

Methods

Poly(lactic-co-glycolic acid) (PLGA) nanoparticles were prepared with a hydrophilic PEGylated “nano-shield” inserted at different levels by hydrophobic anchoring using either a phospholipid-PEG conjugate or the copolymer PLGA-block-PEG by an emulsification/diffusion method. Surface and bulk analysis was performed including X-ray photoelectron spectroscopy (XPS), nuclear magnetic resonance spectroscopy (NMR) and zeta potential. Cellular uptake was investigated in RAW 264.7 macrophages by flow cytometry.

Results

Sub-micron nanoparticles were formed and the combination of (NMR) and XPS revealed increasing PEG levels at the particle surface at higher PLGA-b-PEG copolymer levels. Reduced cellular interaction with RAW 264.7 cells was demonstrated that correlated with greater surface presentation of PEG.

Conclusion

This work demonstrates a versatile procedure for decorating nanoparticle surfaces with hydrophilic “nano-shields”. XPS in combination with NMR enabled precise determination of PEG at the outmost surface to predict and optimize the biological performance of nanoparticle-based drug delivery.     

Carbon Dioxide-Mediated Generation of Hybrid Nanoparticles for Improved Bioavailability of Protein Kinase Inhibitors

Purpose

A versatile methodology is demonstrated for improving dissolution kinetics, gastrointestinal (GI) absorption, and bioavailability of protein kinase inhibitors (PKIs).

Methods

The approach is based on nanoparticle precipitation by sub- or supercritical CO₂ together with a matrix-forming polymer, incorporating surfactants either during or after nanoparticle formation. Notably, striking synergistic effects between hybrid PKI/polymer nanoparticles and surfactant added after particle formation is investigated.

Results

The hybrid nanoparticles, consisting of amorphous PKI embedded in a polymer matrix (also after 12 months), display dramatically increased release rate of nilotinib in both simulated gastric fluid and simulated intestinal fluid, particularly when surfactants are present on the hybrid nanoparticle surface. Similar results indicated flexibility of the approach regarding polymer identity, drug load, and choice of surfactant. The translation of the increased dissolution rate found in vitro into improved GI absorption and bioavalilability in vivo was demonstrated for male beagle dogs, where a 730% increase in the AUC_0–24h was observed compared to the benchmark formulation. Finally, the generality of the formulation approach taken was demonstrated for a range of PKIs.

Conclusions

Hybrid nanoparticles combined with surfactant represent a promising approach for improving PKI dissolution rate, providing increased GI absorption and bioavailability following oral administration.     

Engineering of an Inhalable DDA/TDB Liposomal Adjuvant: A Quality-by-Design Approach Towards Optimization of the Spray Drying Process

Purpose

The purpose of this study was to identify and optimize spray drying parameters of importance for the design of an inhalable powder formulation of a cationic liposomal adjuvant composed of dimethyldioctadecylammonium (DDA) bromide and trehalose-6,6′-dibehenate (TDB).

Methods

A quality by design (QbD) approach was applied to identify and link critical process parameters (CPPs) of the spray drying process to critical quality attributes (CQAs) using risk assessment and design of experiments (DoE), followed by identification of an optimal operating space (OOS). A central composite face-centered design was carried out followed by multiple linear regression analysis.

Results

Four CQAs were identified; the mass median aerodynamic diameter (MMAD), the liposome stability (size) during processing, the moisture content and the yield. Five CPPs (drying airflow, feed flow rate, feedstock concentration, atomizing airflow and outlet temperature) were identified and tested in a systematic way. The MMAD and the yield were successfully modeled. For the liposome size stability, the ratio between the size after and before spray drying was modeled successfully. The model for the residual moisture content was poor, although, the moisture content was below 3% in the entire design space. Finally, the OOS was drafted from the constructed models for the spray drying of trehalose stabilized DDA/TDB liposomes.

Conclusions

The QbD approach for the spray drying process should include a careful consideration of the quality target product profile. This approach implementing risk assessment and DoE was successfully applied to optimize the spray drying of an inhalable DDA/TDB liposomal adjuvant designed for pulmonary vaccination.

Characterization of a Nanoparticulate Drug Delivery System Using Scanning Ion Occlusion Sensing

Purpose

To explore the application of scanning ion occlusion sensing (SIOS) as a novel technology for characterization of nanoparticles.

Methods

Liposomes were employed as model nanoparticles. The size distribution of the liposomes was measured by both SIOS and dynamic light scattering (DLS). Particle number concentration was determined based on particle translocation rate. The ability of SIOS and DLS to resolve bimodal samples was evaluated by measuring a mixture of 217 and 355 nm standard nanoparticles. Opsonization of liposomes by plasma was also studied using SIOS.

Results

SIOS was shown to measure the size of different liposomes with higher sensitivity than DLS and it requires a smaller sample volume than DLS. With appropriate calibration, SIOS could be used to determine particle number concentrations. In comparison, SIOS analysis of the mixture showed accurate resolution of the population as a bimodal distribution over a wide range of number ratios of the particles. SIOS could detect plasma opsonization of liposomes by demonstrating a increase in particle size and also changes in the particle translocation rate.

Conclusion

SIOS is a useful technology for nanoparticle characterization. It shows some advantages over DLS and is clearly a useful tool for the study of nanoparticle drug delivery systems.