Dry powder inhalation of macromolecules using novel PEG-co-polyester microparticle carriers

Polysaccharides screening for pulmonary mucus penetration by molecular dynamics simulation and in vitro verification

Mucus penetration is one of the physiologic barriers of inhalation and nanocarriers can effectively facilitate the permeation of drugs. The interactions between the nanocarriers and mucin are crucial for penetration across the mucus layer on the respiratory tract. In this study, we proposed a molecular dynamics (MD) simulation method for the screening of polysaccharides that acted as the surface modification materials for inhalable nano-preparations to facilitate mucus penetration. MD revealed all-atom interactions between the monomers of polysaccharides, including dextran (DEX)/hyaluronic acid (HA)/carboxymethyl chitosan (CMCS) and the human mucin protein MUC5AC (hMUC5AC). The obtained data showed that DEX formed stronger non-covalent bonds with hMUC5AC compared to HA and CMCS, which suggested that HA and CMCS had better mucus permeability than DEX. For the in vitro verification, HA/CMCS-coated liposomes and DEX/PEG-inserted liposomes were prepared. The results of mucin interactions and mucus penetration studies confirmed that HA and CMCS possessed the weakest interactions with mucin and facilitated the mucus penetration, which was in consistent with the data from MD simulation. This work may shed light on the MD simulation-based screening of surface modification materials for inhalable nano-preparations to facilitate mucus penetration.

Impact of dispersion media and carrier type on spray-dried proliposome powder formulations loaded with beclomethasone dipropionate for their pulmonary drug delivery via a next generation impactor

Drug delivery via aerosolization for localized and systemic effect is a non-invasive approach to achieving pulmonary targeting. The aim of this study was to prepare spray-dried proliposome (SDP) powder formulations to produce carrier particles for superior aerosolization performance, assessed via a next generation impactor (NGI) in combination with a dry powder inhaler. SDP powder formulations (F1-F10) were prepared using a spray dryer, employing five different types of lactose carriers (Lactose monohydrate (LMH), lactose microfine (LMF), lactose 003, lactose 220 and lactose 300) and two different dispersion media. The first dispersion medium was comprised of water and ethanol (50:50% v/v ratio), and the second dispersion medium comprised wholly of ethanol (100%). In the first dispersion medium, the lipid phase (consisting of Soya phosphatidylcholine (SPC as phospholipid) and Beclomethasone dipropionate (BDP; model drug) were dissolved in ethanol and the lactose carrier in water, followed by spray drying. Whereas in second dispersion medium, the lipid phase and lactose carrier were dispersed in ethanol only, post spray drying. SDP powder formulations (F1-F5) possessed significantly smaller particles (2.89 ± 1.24-4.48 ± 1.20 μm), when compared to SDP F6-F10 formulations (10.63 ± 3.71-19.27 ± 4.98 μm), irrespective of lactose carrier type via SEM (scanning electron microscopy). Crystallinity of the F6-F10 and amorphicity of F1-F15 formulations were confirmed by XRD (X-ray diffraction). Differences in size and crystallinity were further reflected in production yield, where significantly higher production yield was obtained for F1-F5 (74.87 ± 4.28-87.32 ± 2.42%) then F6-F10 formulations (40.08 ± 5.714-54.98 ± 5.82%), irrespective of carrier type. Negligible differences were noted in terms of entrapment efficiency, when comparing F1-F5 SDP formulations (94.67 ± 8.41-96.35 ± 7.93) to F6-F10 formulations (78.16 ± 9.35-82.95 ± 9.62). Moreover, formulations F1-F5 demonstrated significantly higher fine particle fraction (FPF), fine particle dose (FPD) and respirable fraction (RF) (on average of 30.35%, 890.12 μg and 85.90%) when compared to counterpart SDP powder formulations (F6-F10). This study has demonstrated that when a combination of water and ethanol was employed as dispersion medium (formulations F1-F5), superior formulation properties for pulmonary drug delivery were observed, irrespective of carrier type employed.

Polyglycerol Adipate-Grafted Polycaprolactone Nanoparticles as Carriers for the Antimicrobial Compound Usnic Acid

Nanoparticle (NP) drug delivery systems are known to potentially enhance the efficacy of therapeutic agents. As for antimicrobial drugs, therapeutic solutions against drug-resistant microbes are urgently needed due to the worldwide antimicrobial resistance issue. Usnic acid is a widely investigated antimicrobial agent suffering from poor water solubility. In this study, polymer nanoparticles based on polyglycerol adipate (PGA) grafted with polycaprolactone (PCL) were developed as carriers for usnic acid. We demonstrated the potential of the developed systems in ensuring prolonged bactericidal activity against a model bacterial species, Staphylococcus epidermidis. The macromolecular architecture changes produced by PCL grafted from PGA significantly influenced the drug release profile and mechanism. Specifically, by varying the length of PCL arms linked to the PGA backbone, it was possible to tune the drug release from a burst anomalous drug release (high PCL chain length) to a slow diffusion-controlled release (low PCL chain length). The developed nanosystems showed a prolonged antimicrobial activity (up to at least 7 days) which could be used in preventing/treating infections occurring at different body sites, including medical device-related infection and mucosal/skin surface, where Gram-positive bacteria are commonly involved.

Polymers as Encapsulating Agents and Delivery Vehicles of Enzymes

Enzymes are versatile biomolecules with broad applications. Since they are biological molecules, they can be easily destabilized when placed in adverse environmental conditions, such as variations in temperature, pH, or ionic strength. In this sense, the use of protective structures, as polymeric capsules, has been an excellent approach to maintain the catalytic stability of enzymes during their application. Thus, in this review, we report the use of polymeric materials as enzyme encapsulation agents, recent technological developments related to this subject, and characterization methodologies and possible applications of the formed bioactive structures. Our search detected that the most explored methods for enzyme encapsulation are ionotropic gelation, spray drying, freeze-drying, nanoprecipitation, and electrospinning. α-chymotrypsin, lysozyme, and β-galactosidase were the most used enzymes in encapsulations, with chitosan and sodium alginate being the main polymers. Furthermore, most studies reported high encapsulation efficiency, enzyme activity maintenance, and stability improvement at pH, temperature, and storage. Therefore, the information presented here shows a direction for the development of encapsulation systems capable of stabilizing different enzymes and obtaining better performance during application.

Recent updates in COVID-19 with emphasis on inhalation therapeutics: Nanostructured and targeting systems

The current world health threat posed by the novel coronavirus disease of 2019 (COVID-19) calls for the urgent development of effective therapeutic options. COVID-19 needs daunting routes such as nano-antivirals. Hence, the role of nanotechnology is very critical in combating this nano-enemy "virus." Although substantial resources are under ongoing attention for prevention and care, we would like to start sharing with readers our vision of the role of inhaled nanomaterials and targeting systems that can play an important role in the fight against the COVID-19. In this review, we underline the genomic structure of COVID-19, recent modes of virus transmission with measures to control the infection, pathogenesis, clinical presentation of SARS-CoV-2, and how much the virus affects the lung. Additionally, the recent therapeutic approaches for managing COVID-19 with emphasis on the value of nanomaterial-based technical approaches are discussed in this review. This review also focuses on the safe and efficient delivery of useable targeted therapies using designed nanocarriers. Moreover, the effectiveness and availability of active targeting of certain specific receptors expressed on the coronavirus surfaces via tailored ligand nanoparticles are manipulated. It was also highlighted in this review the role of inhaled medicines including antivirals and repurposed drugs for fighting the associated lung disorders and efficiency of developed vaccines. Moreover, the inhalation delivery safety techniques were also highlighted.

Oral inhalation for delivery of proteins and peptides to the lungs

Oral inhalation is the preferred route for delivery of small molecules to the lungs, because high tissue levels can be achieved shortly after application. Biologics are mainly administered by intravenous injection but inhalation might be beneficial for the treatment of lung diseases (e.g. asthma). This review discusses biological and pharmaceutical challenges for delivery of biologics and describes promising candidates. Insufficient stability of the proteins during aerosolization and the biological environment of the lung are the main obstacles for pulmonary delivery of biologics. Novel nebulizers will improve delivery by inducing less shear stress and administration as dry powder appears suitable for delivery of biologics. Other promising strategies include pegylation and development of antibody fragments, while carrier-encapsulated systems currently play no major role in pulmonary delivery of biologics for lung disease. While development of various biologics has been halted or has shown little effects, AIR DNase, alpha1-proteinase inhibitor, recombinant neuraminidase, and heparin are currently being evaluated in phase III trials. Several biologics are being tested for the treatment of coronavirus disease (COVID)-19, and it is expected that these trials will lead to improvements in pulmonary delivery of biologics.

Developing inhaled protein therapeutics for lung diseases

Biologic therapeutics such as protein/polypeptide drugs are conventionally administered systemically via intravenous injection for the treatment of diseases including lung diseases, although this approach leads to low target site accumulation and the potential risk for systemic side effects. In comparison, topical delivery of protein drugs to the lung via inhalation is deemed to be a more effective approach for lung diseases, as proteins would directly reach the target in the lung while exhibiting poor diffusion into the systemic circulation, leading to higher lung drug retention and efficacy while minimising toxicity to other organs. This review examines the important considerations and challenges in designing an inhaled protein therapeutics for local lung delivery: the choice of inhalation device, structural changes affecting drug deposition in diseased lungs, clearance mechanisms affecting an inhaled protein drug’s lung accumulation, protein stability, and immunogenicity. Possible approaches to overcoming these issues will also be discussed.

The Effect of Particle Size and Surface Roughness of Spray-Dried Bosentan Microparticles on Aerodynamic Performance for Dry Powder Inhalation

The purpose of this study was to prepare spray dried bosentan microparticles for dry powder inhaler and to characterize its physicochemical and aerodynamic properties. The microparticles were prepared from ethanol/water solutions containing bosentan using spray dryer. Three types of formulations (SD60, SD80, and SD100) depending on the various ethanol concentrations (60%, 80%, and 100%, respectively) were used. Bosentan microparticle formulations were characterized by scanning electron microscopy, powder X-ray diffraction, laser diffraction particle sizing, differential scanning calorimetry, Fourier-transform infrared spectroscopy, dissolution test, and in vitro aerodynamic performance using Andersen cascade impactor^™ (ACI) system. In addition, particle image velocimetry (PIV) system was used for directly confirming the actual movement of the aerosolized particles. Bosentan microparticles resulted in formulations with various shapes, surface morphology, and particle size distributions. SD100 was a smooth surface with spherical morphology, SD80 was a rough surfaced with spherical morphology and SD60 was a rough surfaced with corrugated morphology. SD100, SD80, and SD60 showed significantly high drug release up to 1 h compared with raw bosentan. The aerodynamic size of SD80 and SD60 was 1.27 µm and SD100 was 6.95 µm. The microparticles with smaller particle size and a rough surface aerosolized better (%FPF: 63.07 ± 2.39 and 68.27 ± 8.99 for SD60 and SD80, respectively) than larger particle size and smooth surface microparticle (%FPF: 22.64 ± 11.50 for SD100).

Poly (glycerol adipate) (PGA), an Enzymatically Synthesized Functionalizable Polyester and Versatile Drug Delivery Carrier: A Literature Update

The enzymatically synthesized poly (glycerol adipate) (PGA) has demonstrated all the desirable key properties required from a performing biomaterial to be considered a versatile “polymeric-tool” in the broad field of drug delivery. The step-growth polymerization pathway catalyzed by lipase generates a highly functionalizable platform while avoiding tedious steps of protection and deprotection. Synthesis requires only minor purification steps and uses cheap and readily available reagents. The final polymeric material is biodegradable, biocompatible and intrinsically amphiphilic, with a good propensity to self-assemble into nanoparticles (NPs). The free hydroxyl group lends itself to a variety of chemical derivatizations via simple reaction pathways which alter its physico-chemical properties with a possibility to generate an endless number of possible active macromolecules. The present work aims to summarize the available literature about PGA synthesis, architecture alterations, chemical modifications and its application in drug and gene delivery as a versatile carrier. Following on from this, the evolution of the concept of enzymatically-degradable PGA-drug conjugation has been explored, reporting recent examples in the literature.

Toxicological assessment of nanoparticle interactions with the pulmonary system

Nanoparticle(NP)-based materials have breakthrough applications in many fields of life, such as in engineering, communications and textiles industries; food and bioenvironmental applications; medicines and cosmetics, etc. Biomedical applications of NPs are very active areas of research with successful translation to pharmaceutical and clinical uses overcoming both pharmaceutical and clinical challenges. Although the attractiveness and enhanced applications of these NPs stem from their exceptional properties at the nanoscale size, i.e. 1-1000 nm, they exhibit completely different physicochemical profiles and, subsequently, toxicological profiles from their parent bulk materials. Hence, the clinical evaluation and toxicological assessment of NPs interactions within biological systems are continuously evolving to ensure their safety at the nanoscale. The pulmonary system is one of the primary routes of exposure to airborne NPs either intentionally, via aerosolized nanomedicines targeting pulmonary pathologies such as cancer or asthma, or unintentionally, via natural NPs and anthropogenic (man-made) NPs. This review presents the state-of-the-art, contemporary challenges, and knowledge gaps in the toxicological assessment of NPs interactions with the pulmonary system. It highlights the main mechanisms of NP toxicity, factors influencing their toxicity, the different toxicological assessment methods and their drawbacks, and the recent NP regulatory guidelines based on literature collected from the research pool of NPs interactions with lung cell lines, in vivo inhalation studies, and clinical trials.

Pulmonary delivery of Nanocomposite Microparticles (NCMPs) incorporating miR-146a for treatment of COPD

The treatment and management of COPD by inhalation to the lungs has emerged as an attractive alternative route to oral dosing due to higher concentrations of the drug being administered to site of action. In this study, Nanocomposite Microparticles (NCMPs) of microRNA (miR-146a) containing PGA-co-PDL nanoparticles (NPs) for dry powder inhalation were formulated using l-leucine and mannitol. The spray-drying (Buchi B290) process was optimised and used to incorporate NPs into NCMPs using mix of l-leucine and mannitol excipients in different ratios (F1; 100:0% w/w, F2; 75:25% w/w, F3; 50:50% w/w, F4; 25:75% w/w, F5; 0:100% w/w) to investigate yield %, moisture content, aerosolisation performance and miR-146a biological activity. The optimum condition was performed at feed rate 0.5 ml/min, aspirator rate 28 m³/h, atomizing air flow rate 480 L/h, and inlet drying temperature 70 °C which produced highest yield percentage and closest recovered NPs size to original prior spray-drying. The optimum formulation (F4) had a high yield (86.0 ± 15.01%), recovered NPs size after spray-drying 409.7 ± 10.05 nm (initial NPs size 244.8 ± 4.40 nm) and low moisture content (2.02 ± 0.03%). The aerosolisation performance showed high Fine Particle Fraction (FPF) 51.33 ± 2.9%, Emitted Dose (ED) of 81.81 ± 3.0%, and the mass median aerodynamic diameter (MMAD) was ≤5 µm suggesting a deposition in the respirable region of the lungs. The biological activity of miR-146a was preserved after spray-drying process and miR-146a loaded NCMPs produced target genes IRAK1 and TRAF6 silencing. These results indicate the optimal process parameters for the preparation of NCMPs of miR-146a-containing PGA-co-PDL NPs suitable for inhalation in the treatment and management of COPD.

Carriers for the targeted delivery of aerosolized macromolecules for pulmonary pathologies

INTRODUCTION

Macromolecules with unique effects and potency are increasingly being considered for application in lung pathologies. Numerous delivery strategies for these macromolecules through the lung have been investigated to improve the targeting and overall efficacy.

AREAS COVERED

Targeting approaches from delivery devices, formulation strategies and specific targets are discussed.

EXPERT OPINION

Although macromolecules are a heterogeneous group of molecules, a number of strategies have been investigated at the macro, micro, and nanoscopic scale for the delivery of macromolecules to specific sites and cells of lung tissues. Targeted approaches are already in use at the macroscopic scale through inhalation devices and formulations, but targeting strategies at the micro and nanoscopic scale are still in the laboratory stage. The combination of controlling lung deposition and targeting after deposition, through a combination of targeting strategies could be the future direction for the treatment of lung pathologies through the pulmonary route.

Critical Parameters for Particle-Based Pulmonary Delivery of Chemotherapeutics

Targeted delivery of chemotherapeutics through the respiratory system is a potential approach to improve drug accumulation in the lung tumor, while decreasing their negative side effects. However, elimination by the pulmonary clearance mechanisms, including the mucociliary transport system, and ingestion by the alveolar macrophages, rapid absorption into the blood, enzymatic degradation, and low control over the deposition rate and location remain the main complications for achieving an effective pulmonary drug delivery. Therefore, particle-based delivery systems have emerged to minimize pulmonary clearance mechanisms, enhance drug therapeutic efficacy, and control the release behavior. A successful implementation of a particle-based delivery system requires understanding the influential parameters in terms of drug carrier, inhalation technology, and health status of the patient's respiratory system. This review aims at investigating the parameters that significantly drive the clinical outcomes of various particle-based pulmonary delivery systems. This should aid clinicians in appropriate selection of a delivery system according to their clinical setting. It will also guide researchers in addressing the remaining challenges that need to be overcome to enhance the efficiency of current pulmonary delivery systems for aerosols.

Colonic delivery of indometacin loaded PGA-co-PDL microparticles coated with Eudragit L100-55 from fast disintegrating tablets

The aim of this work was to investigate the efficient targeting and delivery of indometacin (IND), as a model anti-inflammatory drug to the colon for treatment of inflammatory bowel disease. We prepared fast disintegrating tablets (FDT) containing IND encapsulated within poly(glycerol-adipate-co-ɷ-pentadecalactone), PGA-co-PDL, microparticles and coated with Eudragit L100-55 at different ratios (1:1.5, 1:1, 1:0.5). Microparticles encapsulated with IND were prepared using an o/w single emulsion solvent evaporation technique and coated with Eudragit L-100-55 via spray drying. The produced coated microparticles (PGA-co-PDL-IND/Eudragit) were formulated into optimised FTD using a single station press. The loading, in vitro release, permeability and transport of IND from PGA-co-PDL-IND/Eudragit microparticles was studied in Caco-2 cell lines. IND was efficiently encapsulated (570.15±4.2μg/mg) within the PGA-co-PDL microparticles. In vitro release of PGA-co-PDL-IND/Eudragit microparticles (1:1.5) showed significantly (p<0.05, ANOVA/Tukey) lower release of IND 13.70±1.6 and 56.46±3.8% compared with 1:1 (89.61±2.5, 80.13±2.6%) and 1:0.5 (39.46±0.9 & 43.38±3.12) after 3 and 43h at pH 5.5 and 6.8, respectively. The permeability and transport studies indicated IND released from PGA-co-PDL-IND/Eudragit microparticles had a lower permeability coefficient of 13.95±0.68×10^-6cm/s compared to free IND 23.06±3.56×10^-6cm/s. These results indicate the possibility of targeting anti-inflammatory drugs to the colon using FDTs containing microparticles coated with Eudragit.

Preparation and physicochemical characterization of spray-dried and jet-milled microparticles containing bosentan hydrate for dry powder inhalation aerosols

The objectives of this study were to prepare bosentan hydrate (BST) microparticles as dry powder inhalations (DPIs) via spray drying and jet milling under various parameters, to comprehensively characterize the physicochemical properties of the BST hydrate microparticles, and to evaluate the aerosol dispersion performance and dissolution behavior as DPIs. The BST microparticles were successfully prepared for DPIs by spray drying from feeding solution concentrations of 1%, 3%, and 5% (w/v) and by jet milling at grinding pressures of 2, 3, and 4 MPa. The physicochemical properties of the spray-dried (SD) and jet-milled (JM) microparticles were determined via scanning electron microscopy, atomic force microscopy, dynamic light scattering particle size analysis, Karl Fischer titration, surface analysis, pycnometry, differential scanning calorimetry, powder X-ray diffraction, and Fourier transform infrared spectroscopy. The in vitro aerosol dispersion performance and drug dissolution behavior were evaluated using an Anderson cascade impactor and a Franz diffusion cell, respectively. The JM microparticles exhibited an irregular corrugated surface and a crystalline solid state, while the SD microparticles were spherical with a smooth surface and an amorphous solid state. Thus, the in vitro aerosol dispersion performance and dissolution behavior as DPIs were considerably different due to the differences in the physicochemical properties of the SD and JM microparticles. In particular, the highest grinding pressures under jet milling exhibited excellent aerosol dispersion performance with statistically higher values of 56.8%±2.0% of respirable fraction and 33.8%±2.3% of fine particle fraction and lower mass median aerodynamic diameter of 5.0±0.3 μm than the others (P<0.05, analysis of variance/Tukey). The drug dissolution mechanism was also affected by the physicochemical properties that determine the dissolution kinetics of the SD and JM microparticles, which were well fitted into the Higuchi and zero-order models, respectively.

Full factorial design optimization of anti-inflammatory drug release by PCL-PEG-PCL microspheres

A biodegradable triblock poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) copolymer was successfully synthesized by ring-opening polymerization of ε-caprolactone, and was characterized by intrinsic viscosimetry, (1)H nuclear magnetic resonance, infrared spectroscopy and X-ray diffraction. Copolymer microparticles loaded with ibuprofen were prepared by an oil-in-water (o/w) emulsion solvent evaporation process. They were carefully weighted and characterized through their zeta potential. In this work, 4 selected process parameters (shaking speed X1, time of contact X2, poly(vinyl alcohol) concentration X3, and ibuprofen concentration X4) were adjusted at 2 different values. For each of the 16 experimental conditions, repeated twice, the drug encapsulation efficiency of the microspheres was determined, according to the following definition: EE (X1, X2, X3, X4)=mass of encapsulated ibuprofen/total weight of ibuprofen. A "full factorial design method" was applied to analyze the results statistically according to a polynomial fit and to determine the optimal conditions for the microencapsulation of the ibuprofen through an accurate statistical protocol. The microparticles obtained exhibit a spherical shape as shown by electron microscopy.

Bovine serum albumin adsorbed PGA-co-PDL nanocarriers for vaccine delivery via dry powder inhalation

PURPOSE

Dry powder vaccine delivery via the pulmonary route has gained significant attention as an alternate route to parenteral delivery. In this study, we investigated bovine serum albumin (BSA) adsorbed poly(glycerol adipate-co-ω-pentadecalactone), PGA-co-PDL polymeric nanoparticles (NPs) within L-leucine (L-leu) microcarriers for dry powder inhalation.

METHODS

NPs were prepared by oil-in-water single emulsion-solvent evaporation and particle size optimised using Taguchi's design of experiment. BSA was adsorbed onto NPs at different ratios at room temperature. The NPs were spray-dried in aqueous suspension of L-leu (1:1.5) using a Büchi-290 mini-spray dryer. The resultant nanocomposite microparticles (NCMPs) were characterised for toxicity (MTT assay), aerosolization (Next Generation Impactor), in vitro release study and BSA was characterized using SDS-PAGE and CD respectively.

RESULTS

NPs of size 128.50 ± 6.57 nm, PDI 0.07 ± 0.03 suitable for targeting lung dendritic cells were produced. BSA adsorption for 1 h resulted in 10.23 ± 1.87 μg of protein per mg of NPs. Spray-drying with L-leu resulted in NCMPs with 42.35 ± 3.17% yield. In vitro release study at 37°C showed an initial burst release of 30.15 ± 2.33% with 95.15 ± 1.08% over 48 h. Aerosolization studies indicated fine particle fraction (FPF%) dae < 4.46 μm as 76.95 ± 5.61% and mass median aerodynamic diameter (MMAD) of 1.21 ± 0.67 μm. The cell viability was 87.01 ± 14.11% (A549 cell line) and 106.04 ± 21.14% (16HBE14o- cell line) with L-leu based NCMPs at 1.25 mg/ml concentration after 24 h treatment. The SDS-PAGE and CD confirmed the primary and secondary structure of the released BSA.

CONCLUSIONS

The results suggest that PGA-co-PDL/L-leu NCMPs may be a promising carrier for pulmonary vaccine delivery due to excellent BSA adsorption and aerosolization behaviour.

Engineering hydrophobically modified chitosan for enhancing the dispersion of respirable microparticles of levofloxacin

The potential of amphiphilic chitosan formed by grafting octanoyl chains on the chitosan backbone for pulmonary delivery of levofloxacin has been studied. The success of polymer synthesis was confirmed using FT-IR and NMR, whilst antimicrobial activity was assessed against Pseudomonas aeruginosa. Highly dispersible dry powders for delivery as aerosols were prepared with different amounts of chitosan and octanoyl chitosan to study the effect of hydrophobic modification and varying concentration of polymer on aerosolization of drug. Powders were prepared by spray-drying from an aqueous solution containing levofloxacin and chitosan/amphiphilic octanoyl chitosan. l-leucine was also used to assess its effect on aerosolization. Following spray-drying, the resultant powders were characterized using scanning electron microscopy, laser diffraction, dynamic light scattering, HPLC, differential scanning calorimetry, thermogravimetric analysis and X-ray powder diffraction. The in vitro aerosolization profile was determined using a Next Generation Impactor, whilst in vitro antimicrobial assessment was performed using MIC assay. Microparticles of chitosan have the property of mucoadhesion leading to potential increased residence time in the pulmonary mucus, making it important to test the toxicity of these formulations. In-vitro cytotoxicity evaluation using MTT assay was performed on A549 cell line to determine the toxicity of formulations and hence feasibility of use. The MTT assay confirmed that the polymers and the formulations were non-cytotoxic. Hydrophobically modifying chitosan showed significantly lower MIC (4-fold) than the commercial chitosan against P. aeruginosa. The powders generated were of suitable aerodynamic size for inhalation having a mass median aerodynamic diameter less than 4.5μm for formulations containing octanoyl chitosan. These highly dispersible powders have minimal moisture adsorption and hence an emitted dose of more than 90% and a fine particle fraction (FPF) of 52%. Powders with non-modified chitosan showed lower dispersibility, with an emitted dose of 72% and FPF of 20%, as a result of high moisture adsorption onto the chitosan matrix leading to cohesiveness and subsequently decreased dispersibility.

Manufacturing and device options for the delivery of biotherapeutics

Biotherapeutic aerosol formulations are an intense area of interest for systemic and local drug delivery. This article provides a short overview of typical factors required specifically for biotherapeutic aerosol formulation design, the processing options open for consideration, and the issue of inhalation device selection. Focusing on spray drying, four case studies are used to highlight the relevant issues, describing investigations into: (1) the mechanical stresses occurring in bacteriophage formulations during spray-dryer atomization; (2) modeling of the spray-dryer process and droplet drying kinetics, to assist process design and predictions of formulation stability; (3) a predictive approach to the design and processing of a five-component dry powder aerosol formulation; and (4) the survival of bacteriophages after pressurized metered dose inhaler atomization.