Moisture-Resistant Co-Spray-Dried Netilmicin with l-Leucine as Dry Powder Inhalation for the Treatment of Respiratory Infections

Particulate platform for pulmonary drug delivery: Recent advances of formulation and fabricating strategies

Pulmonary drug delivery for managing respiratory diseases has attained a significant maturity level and holds substantial potential for applications in treating systemic diseases. Advancements in pulmonary delivery techniques have driven the innovative development of dry powder inhalers (DPIs), specifically engineered to optimize the efficacy of pulmonary drug delivery. This review examines recent progress in formulation and manufacturing strategies of inhalable dry powder, focusing on prescription design and fabrication approaches for advanced particulate systems. These include the integration of cutting-edge excipients into conventional formulations, nano-based delivery system, composite particles, and a blend of traditional and next-generation processing techniques, all contributing to enhanced drug delivery efficiency and bioavailability. Additionally, this review discusses the latest advancements in DPI devices. This review aims to provide a clear perspective on emerging inhalable dry powder formulation and processing trends for pulmonary delivery, highlighting the critical role of novel particulate platform in advancing pulmonary drug delivery systems.

Particle surface coating for dry powder inhaler formulations

INTRODUCTION

The development of dry powder inhalers (DPIs) is challenging due to the need for micronized particles to achieve lung delivery. The high specific surface area of micronized particles renders them cohesive and adhesive. Addition of certain excipients like magnesium stearate has been reported to coat the particles and improve the aerosolization in the carrier-based DPI. Therefore, application of particle coating in DPI developments has been investigated and expanded over the years, along with the growing need of high-dose carrier-free DPIs.

AREA COVERED

In addition to modifying inter-particulate forces, particle coating has also been demonstrated to effectively provide moisture resistance, modify particle morphology, improve the stability of biologics, alter dissolution behaviors for DPI developments. These different coating functions have been discussed in the current work. Moreover, various coating techniques including solvent-based coating, dry coating, and vapor coating, as well as coating characterization have been summarized in the present review.

EXPERT OPINION

The extent of particle coating is critical to DPI performance; however, there is a demand for advanced characterization techniques to quantify and understand the coating quality. Further advancements in coating materials, methods, characterization techniques are needed to better relate coating properties to performance, especially for complex drug modalities.

Impact of Co-Spray Drying with Leucine or Trileucine on Aerosol Performance, In Vitro Dissolution, and Cellular Uptake of Colistin Powder Formulations for Inhalation

Background/Objective: Surface enrichment of hydrophobic excipients via spray drying has been demonstrated as an efficient way to protect the dry powder inhaler formulations against moisture-induced deterioration in aerosol performance. However, the impact of such surface enrichment on dissolution and cellular uptake is less investigated, which can affect the safety and efficacy of dry powder inhalers (DPIs). Methods: In the present work, hygroscopic colistin was coated with leucine or trileucine, at different weight ratios during spray drying. All the powders were exposed to 75% relative humidity for one week. The aerosol performance was compared before and after the moisture exposure. Various solid-state characterizations, including particle size, particle morphology, crystallinity, water sorption/desorption, and surface composition, were conducted to evaluate the properties of spray-dried colistin with/without leucine or trileucine. Results: The results indicated that leucine or trileucine could protect the aerosol performance of spray-dried colistin against moisture deterioration. Leucine crystallized after spray drying with colistin, and such crystal leucine could further hinder water uptake when leucine was at a 20% or higher weight ratio. Trileucine did not crystallize after spray drying with colistin nor reduce the water uptake. Interestingly, trileucine showed a superior moisture protective effect to that of leucine, which could be attributed to its better surface enrichment efficiency than that of leucine due to its lower water solubility. Conclusions: Importantly, our results showed that the surface enrichment with leucine and trileucine did not significantly affect in vitro dissolution of colistin in the Franz cell test and cellular uptake of colistin in the H441 lung epithelium cell model, which could be attributed to small particle size and incomplete surface coverage by leucine or trileucine.

Cannabidiol and Hydroxypropyl-β-Cyclodextrin for the Development of Deflated Spherical-Shaped Inhalable Powder

In addition to the known therapeutic indications for cannabidiol, its administration by inhalation appears to be of great interest. Indeed, there is evidence of cannabidiol's efficacy in several physiological pathways, suggesting its potential for a wide range of applications for both local and systemic pulmonary administration like cancers. Significant advances in pulmonary drug delivery have led to innovative strategies to address the challenges of increasing the respirable fraction of drugs and standardizing inhalable products. Among different devices, dry powder inhalers offer significant advantages including high stability and ease of use. Particle engineering using techniques such as spray drying is now the focus of research and is expected to improve upon, rather than completely replace, traditional carrier-based formulations. The development of carrier-free powders (without lactose-carrier) is mainly used for medicines with low active ingredient doses, which limits the technology. Previously, we demonstrated the benefits of using a cyclodextrin to obtain deflated spherical-shaped powders by spray drying. In this study the potential of this excipient with a very poorly water-soluble active molecule was investigated. Inhalable cannabidiol powders were developed by spray drying, using the solubility enhancers hydroxypropyl-beta-cyclodextrin and ethanol to optimize cannabidiol water-solubility. Electron microscopy images revealed consistent deflated spherical shapes, while particle size analysis showed low polydispersity and suitable sizes for deep lung deposition (2 µm). The selected engineered powders (without ethanol) had very high fine particle fractions (> 60%) due to their deflated surface. Finally, the powder was instantly solubilized leading to drug dissolution, which is important for therapeutic efficacy. In conclusion, this study successfully develops a cannabidiol inhalation powder by particle engineering having suitable aerosolization behavior. Due to the speed of the process and the performance of the finished product, this work opens the door for future studies. It has been shown that active molecules that are only slightly soluble in water can be formulated effectively as a powder for inhalation. Other molecules could be tested and subsequent in vivo studies conducted to demonstrate correlation with these in vitro results.

Posaconazole nanocrystals dry powder inhalers for the local treatment of invasive pulmonary aspergillosis

Invasive pulmonary aspergillosis poses a significant threat to immunocompromised patients, characterized by high mortality rates. Posaconazole (PSZ), a second-generation triazole antifungal, exhibits broad-spectrum activity but suffers from limited pulmonary concentrations and notable systemic side effects when administered orally or intravenously. This study focuses on optimizing PSZ nanocrystals-agglomerated particles for dry powder inhalers (DPIs) to enhance solubility, dissolution rates, and pulmonary deposition, ultimately improving therapeutic efficacy while minimizing systemic adverse effects. We employed wet medium milling and spray-drying techniques to formulate PSZ nanocrystals-agglomerated DPIs. Various stabilizers including HPMC, HPC, Soluplus, and PVPK30, were systematically evaluated to optimize physicochemical properties. Aerosolization performance was assessed using the Next Generation Impactor, while antifungal efficacy was evaluated through in vitro and in vivo studies. The optimized PSZ DPIs demonstrated significant enhancements in solubility and dissolution rates, with a fine particle fraction (FPF) of 78.58 ± 3.21%, ensuring optimal lung delivery. In vitro experiments revealed potent effects with minimal cytotoxicity to lung cells. In vivo studies indicated that the optimized formulation achieved a Cmax/AUC0→∞ ratio in lung tissues that was 27.32 and 6.76-fold higher than that of the oral suspension, highlighting increased local drug concentrations. This approach presents a scalable, cost-effective strategy for the pulmonary delivery of PSZ, ensuring high drug loading and promising clinical outcomes in treating pulmonary fungal infections.

Leucine as a Moisture-Protective Excipient in Spray-Dried Protein/Trehalose Formulation

The incorporation of leucine (Leu), a hydrophobic amino acid, into pharmaceutically relevant particles via spray-drying can improve the physicochemical and particulate properties, stability, and ultimately bioavailability of the final product. More specifically, Leu has been proposed to form a shell on the surface of spray-dried (SD) particles. The aim of this study was to explore the potential of Leu in the SD protein/trehalose (Tre) formulation to control the water uptake and moisture-induced recrystallization of amorphous Tre, using lysozyme (LZM) as a model protein. LZM/Tre (1:1, w/w) was dissolved in water with varied amounts of Leu (0 - 40%, w/w) and processed by spray-drying. The solid form, residual moisture content (RMC), hygroscopicity, and morphology of SD LZM/Tre/Leu powders were evaluated, before and after storage under 22°C/55% RH conditions for 90 and 180 days. The X-ray powder diffraction results showed that Leu was in crystalline form when the amount of Leu in the formulation was at least 20% (w/w). Thermo-gravimetric analysis and scanning electron microscopy results showed that 0%, 5%, and 10% (w/w) Leu formulations led to comparable RMC and raisin-like round particles. In contrast, higher Leu contents resulted in a lower RMC and increased surface corrugation of the SD particles. Dynamic vapor sorption analysis showed that partial recrystallization of amorphous Tre to crystalline Tre·dihydrate occurred in the 0% Leu formulation. However, adding as little as 5% (w/w) Leu inhibited this recrystallization during the water sorption/desorption cycle. In addition, after storage, the formulations with higher Leu contents showed reduced water uptake. Instead of observing recrystallization of amorphous Tre in 0%, 5%, and 10% (w/w) Leu formulations, recrystallization of amorphous Leu was noted in the 5% and 10% (w/w) Leu formulations after storage. In summary, our study demonstrated that the addition of Leu has the potential to reduce water uptake and inhibit moisture-induced recrystallization of amorphous Tre in the SD protein/Tre powder system.

Spray-Dried Mucoadhesive Re-dispersible Gargle of Chlorhexidine for Improved Response Against Throat Infection: Formulation Development, In Vitro and In Vivo Evaluation

Drug delivery to the buccal mucosa is one of the most convenient ways to treat common mouth problems. Here, we propose a spray-dried re-dispersible mucoadhesive controlled release gargle formulation to improve the efficacy of chlorhexidine. The present investigation portrays an approach to get stable and free-flowing spray-dried porous aggregates of chlorhexidine-loaded sodium alginate nanoparticles. The ionic gelation technique aided with the chlorhexidine's positive surface charge-based crosslinking, followed by spray drying of the nanoparticle's dispersion in the presence of lactose- and leucine-yielded nano-aggregates with good flow properties and with a size range of about 120-350 nm. Provided with the high entrapment efficiency (87%), the particles showed sustained drug release behaviors over a duration of 10 h, where 87% of the released drug got permeated within 12 h. The antimicrobial activity of the prepared formulation was tested on S. aureus, provided with a higher zone of growth inhibition than the marketed formulation. Aided with an appropriate mucoadhesive strength, this product exhibited extended retention of nanoparticles in the throat region, as shown by in vivo imaging results. In conclusion, the technology, provided with high drug retention and extended effect, could be a potential candidate for treating several types of throat infections.

Polymyxin B sulfate inhalable microparticles with high-lectin-affinity sugar carriers for efficient treatment of biofilm-associated pulmonary infections

Pulmonary infections caused by multidrug-resistant bacteria have become a significant threat to human health. Bacterial biofilms exacerbate the persistence and recurrence of pulmonary infections, hindering the accessibility and effectiveness of antibiotics. In this study, a dry powder inhalation (DPI) consisting of polymyxin B sulfate (PMBS) inhalable microparticles and high-lectin-affinity (HLA) sugar (i.e., raffinose) carriers was developed for treating pulmonary infections and targeting bacterial lectins essential for biofilm growth. The formulated PMBS-HLA DPIs exhibited particle sizes of approximately 3 μm, and surface roughness varied according to the drug-to-carrier ratio. Formulation F5 (PMBS: raffinose = 10:90) demonstrated the highest fine particle fraction (FPF) value (64.86%), signifying its substantially enhanced aerosol performance, potentially attributable to moderate roughness and smallest mass median aerodynamic particle size. The efficacy of PMBS-HLA DPIs in inhibiting biofilm formation and eradicating mature biofilms was significantly improved with the addition of raffinose, suggesting the effectiveness of lectin-binding strategy for combating bacterial biofilm-associated infections. In rat models with acute and chronic pulmonary infections, F5 demonstrated superior bacterial killing and amelioration of inflammatory responses compared to spray-dried PMBS (F0). In conclusion, our HLA carrier-based formulation presents considerable potential for the efficient treatment of multidrug-resistant bacterial biofilm-associated pulmonary infections.

Hierarchy of the Components in Spray-Dried, Protein-Excipient Particles Using DNP-Enhanced NMR Spectroscopy

Protein-based drugs are becoming increasingly important, but there are challenges associated with their formulation (for example, formulating stable inhalable aerosols while maintaining the proper long-term stability of the protein). Determining the morphology of multicomponent, protein-based drug formulations is particularly challenging. Here, we use dynamic nuclear polarization (DNP) solid-state NMR spectroscopy to determine the hierarchy of components within spray-dried particles containing protein, trehalose, leucine, and trileucine. DNP NMR was applied to these formulations to assess the localization of the components within the particles. We found a consistent scheme, where trehalose and the protein are co-located within the same phase in the core of the particles and leucine and trileucine are distributed in separate phases at the surface of the particles. The description of the hierarchy of the organic components determined by DNP NMR enables the rationalization of the performance of the formulation.

Inhalation powder development without carrier: How to engineer ultra-flying microparticles?

Particle engineering technologies have led to the commercialization of new inhaled powders like PulmoSolTM or PulmoSphereTM. Such platforms are produced by spray drying, a well-known process popular for its versatility, thanks to wide-ranging working parameters. Whereas these powders contain a high drug-loading, we have studied a low-dose case, in optimizing the production of powders with two anti-asthmatic drugs, budesonide and formoterol. Using a Design of Experiments approach, 27 powders were produced, with varying excipient mixes (cyclodextrins, raffinose and maltodextrins), solution concentrations, and spray drying parameters in order to maximize deep lung deposition, measured through fine particle fraction (next generation impactor). Based on statistical analysis, two powders made of hydropropyl-β-cyclodextrin alone or mixed with raffinose and L-leucine were selected. Indeed, the two powders demonstrated very high fine particle fraction (>55%), considerably better than commercially available products. Deep lung deposition has been correlated to very fine particle size and lower microparticles interactions shown by laser diffraction assays at different working pressures, and particle morphometry. Moreover, the two drugs would be predicted to deposit homogeneously into the lung according to impaction studies. Uniform delivery is fundamental to control symptoms of asthma. In this study, we develop carrier-free inhalation powders promoting very efficient lung deposition and demonstrate the high impact of inter-particular interactions intensity on their aerosolization behaviour.

Enhanced powder dispersion of dual-excipient spray-dried powder formulations of a monoclonal antibody and its fragment for local treatment of severe asthma

The advent of biologics has brought renewed hope for patients with severe asthma, a condition notorious for being hampered by poor response to conventional therapies and adverse drug reactions owing to corticosteroid dependence. However, biologics are administered as injections, thereby precluding the benefits inhalation therapy could offer such as increased bioavailability at the site of action, minimal systemic side effects, non-invasiveness, and self-administration. Here, 2-hydroxypropyl-beta-cyclodextrin and ʟ-leucine were co-spray-dried, as protein stabiliser and dispersion enhancer, respectively, at various weight ratios to produce a series of formulation platforms. Powder aerosolisation characteristics and particle morphology were assessed for suitability for pulmonary delivery. The selected platform with the best aerosol performance, a 1:1 ratio of the excipients, was then incorporated with a monoclonal antibody directed against IL-4 receptor alpha or its antigen-binding fragment. The dual-excipient antibody formulations exhibited emitted fraction of at least 80% and fine particle fraction exceeding 60% in cascade impactor study, while the residual moisture content was within a desirable range between 1% and 3%. The in vitro antigen-binding ability and inhibitory potency of the spray-dried antibody were satisfactorily preserved. The results from this study corroborate the viability of inhaled solid-state biomacromolecules as a promising treatment approach for asthma.

Dual functional pullulan-based spray-dried microparticles for controlled pulmonary drug delivery

Two main challenges are associated with current spray-dried microparticles for inhalation, including the enhancement of aerosolization performance of microparticles and the creation of sustained drug release for continuous treatment on-site. For achieving these purposes, pullulan was explored as a novel excipient to prepare spray-dried inhalable microparticles (with salbutamol sulphate, SS, as a model drug), which were further modified by additives of leucine (Leu), ammonium bicarbonate (AB), ethanol and acetone. It was demonstrated that all pullulan-based spray-dried microparticles had improved flowability and enhanced aerosolization behavior, with the fine particle (<4.46µm) fraction of 42.0-68.7% w/w, much higher than 11.4% w/w of lactose-SS. Moreover, all modified microparticles showed augmented emitted fractions of 88.0-96.9% w/w, over 86.5% w/w of pullulan-SS. The pullulan-Leu-SS and pullulan-(AB)-SS microparticles demonstrated further increased fine particle (<1.66µm) doses of 54.7µg and 53.3µg respectively, surpassing that (49.6µg) of pullulan-SS, suggesting an additionally increased drug deposition in the deep lungs. Furthermore, pullulan-based microparticles revealed sustained drug release profiles with elongated time (60mins) over the control (2mins). Clearly, pullulan has a great potential to construct dual functional microparticles for inhalation with improved pulmonary delivery efficiency and sustained drug release on-site.

Targeting lung macrophages for fungal and parasitic pulmonary infections with innovative amphotericin B dry powder inhalers

The incidence of fungal pulmonary infections is known to be on the increase, and yet there is an alarming gap in terms of marketed antifungal therapies that are available for pulmonary administration. Amphotericin B (AmB) is a highly efficient broad-spectrum antifungal only marketed as an intravenous formulation. Based on the lack of effective antifungal and antiparasitic pulmonary treatments, the aim of this study was to develop a carbohydrate-based AmB dry powder inhaler (DPI) formulation, prepared by spray drying. Amorphous AmB microparticles were developed by combining 39.7 % AmB with 39.7 % γ-cyclodextrin, 8.1 % mannose and 12.5 % leucine. An increase in the mannose concentration from 8.1 to 29.8 %, led to partial drug crystallisation. Both formulations showed good in vitro lung deposition characteristics (80 % FPF < 5 µm and MMAD < 3 µm) at different air flow rates (60 and 30 L/min) when used with a DPI, but also during nebulisation upon reconstitution in water.

Development of a new indole derivative dry powder for inhalation for the treatment of biofilm-associated lung infections

The aim of this work was to produce an inhalable dry powder formulation of a new anti-biofilm compound (SC38). For this purpose, chitosan was used as a polymeric carrier and l-leucine as a dispersibility enhancer. SC38 was entrapped by spray-drying into previously optimized chitosan microparticles. The final formulation was fully characterized in vitro in terms of particle morphology, particle size and distribution, flowability, aerodynamic properties, anti-biofilm activity and effects on lung cell viability. The SC38-loaded chitosan microparticles exhibited favorable aerodynamic properties with emitted and respirable fractions higher than 80 % and 45 % respectively. The optimized formulation successfully inhibited biofilm formation at microparticle concentrations starting from 20 μg/mL for methicillin-sensitive and 100 μg/mL for methicillin-resistant Staphylococcus aureus and showed a relatively safe profile in lung cells after 72 h exposure. Future in vivo tolerability and efficacy studies are needed to unravel the potential of this novel formulation for the treatment of difficult-to-treat biofilm-mediated lung infections.

Nanoparticle-containing lyophilized dry powder inhaler formulations optimized using central composite design with improved aerodynamic parameters and redispersibility

Objectives: The aim of this study was to improve the aerodynamic behavior and redispersibility of a lyophilized dry powder inhaler (DPI) formulation containing nanoparticles.Methods: Paclitaxel (PTX)-human serum albumin (HSA) nanoparticles were used as a model, and DPIs containing the nanoparticles were produced by lyophilization using different carriers and carrier ratios. A central composite design was employed to optimize the formulation. L-leucine and mannitol were chosen as independent variables, and mass median aerodynamic diameter (MMAD), emitted fraction, fine particle fraction (FPF), nanoparticle size, polydispersity index (PDI), zeta potential were selected as dependent variables.Results: The water content of DPIs was less than 5% for all DPIs. The cytotoxicity of the DPIs, determined using A549 cells, was due to PTX alone. Particle sizes of 204.3 ± 1.65 nm and 94.3-1353.0 nm were obtained before and after lyophilization, respectively. The developed method resulted in a reduction in the MMAD from 8.148 µm to 5.274 µm, an increase in the FPF from 17.63% to 33.60%, and an increase in the emitted fraction from 77.68% to 97.03%. The physico-chemical characteristics of the optimized formulation were also assessed.Conclusions: In conclusion, this study demonstrates that lyophilization can be used to produce nanoparticle-containing DPI formulations with improved redispersibility and aerodynamic properties.

In vitro Evaluation of Paliperidone Palmitate Loaded Cubosomes Effective for Nasal-to-Brain Delivery

Introduction

This work aimed to develop chitosan-coated cubosomal nanoparticles intended for nose-to-brain delivery of paliperidone palmitate. They were compared with standard and cationic cubosomal nanoparticles. This comparison relies on numerous classical in vitro tests and powder deposition within a 3D-printed nasal cast.

Methods

Cubosomal nanoparticles were prepared by a Bottom-up method followed by a spray drying process. We evaluated their particle size, polydispersity index, zeta-potential, encapsulation efficiency, drug loading, mucoaffinity properties and morphology. The RPMI 2650 cell line was used to assess the cytotoxicity and cellular permeation. An in vitro deposition test within a nasal cast completed these measurements.

Results

The selected chitosan-coated cubosomal nanoparticles loaded with paliperidone palmitate had a size of 305.7 ± 22.54 nm, their polydispersity index was 0.166 ± 0.022 and their zeta potential was +42.4 ± 0.2 mV. This formulation had a drug loading of 70% and an encapsulation efficiency of 99.7 ± 0.1%. Its affinity with mucins was characterized by a ΔZP of 20.93 ± 0.31. Its apparent permeability coefficient thought the RPMI 2650 cell line was 3.00E-05 ± 0.24E-05 cm/s. After instillation in a 3D-printed nasal cast, the fraction of the injected powder deposited in the olfactory region reached 51.47 ± 9.30% in the right nostril and 41.20 ± 4.59% in the left nostril, respectively.

Conclusion

The chitosan coated cubosomal formulation seems to be the most promising formulation for nose-to-brain delivery. Indeed, it has a high mucoaffinity and a significantly higher apparent permeability coefficient than the two other formulations. Finally, it reaches well the olfactory region.

Co-spray-dried poly-L-lysine with L-leucine as dry powder inhalations for the treatment of pulmonary infection: Moisture-resistance and desirable aerosolization performance

Poly-L-lysine (PLL) is a promising candidate for the treatment of pulmonary infection with lower occurrence of drug-resistance due to its unique antibacterial mechanisms. Dry powder inhalations (DPIs) are considered as the first choice for formulating PLL to treat pulmonary infection on account of direct delivery and satisfactory stability. However, hygroscopicity of PLL limited its therapeutic effect on pulmonary infection when PLL developed into DPIs. The hygroscopicity caused two obstacles including the low drug deposition in the lower respiratory tract and undesirable aerosolization performance deterioration. In this study, PLL was co-spray-dried with L-leucine (LL) to achieve moisture-resistance and desirable aerosolization performance. The ratio of PLL and LL was optimized to obtain particles with different morphology, hygroscopicity and aerodynamic properties. The obtained PLL DPIs were suitable for inhalation with a corrugated surface formed by hydrophobic LL. The anti-hygroscopicity, aerosolization performance and rheological properties of P2 DPIs were optimal when PLL:LL = 85:15. The DPIs particles were stable after being stored at high relative humidity (60 ± 5%), and their superiority in treating pulmonary infections was also proved by in vitro and in vivo experiments. The established PLL DPIs were proved to be a feasible and desirable approach to treat pulmonary infections.

Selection and identification of a DNA aptamer for fluorescent detection of netilmicin

Netilmicin (NET) is an antibiotic widely used in healthcare and agriculture, but it can accumulate in the environment to threat human health. Netilmicin (NET) is an antibiotic used for veterinary purposes, for human therapy and for agricultural purposes. Therefore, there is a need to develop high-sensitive measuring methods to detect NET. Aptamer-based detecting methods are highly sensitive, inexpensive, and portable. In this study, we developed an aptamer-based fluorescence method to detect and quantify NET. NET was first conjugated to magnetic beads by amidation reaction and then NET-coated beads were used as the stationary phase to isolate aptamers by systematic evolution of ligands by exponential enrichment (SELEX) screening method. After ten rounds of SELEX screening, 32 aptamers with NET-binding affinity were obtained and the candidate aptamer APT-21 was finally chosen by comprehensively comparing their secondary structure characters and NET-binding affinity. APT-21 bound to NET with high affinity (Kd = 194.1 nmol/L) and high specificity that it displayed low cross-binding activities on 7 different structural analogs. We also developed a fluorometric assay using SYBR Green I (SG-I) and the APT-21. Key experimental parameters were optimized, including buffer system, SG-I and APT-21 reaction time, SG-I concentration, and aptamer concentration, to improve the detecting sensitivity. Our results suggest that the low limit of detection (LOD) of this method reached a low level of 1.95 nM and it also exhibited a good linear range up to 200 nM. Moreover, we successfully applied our method to detect the NET spiked in tap water and river water with good recoveries in the range from 97% to 111%. In conclusion, our current study isolated a NET-specific aptamer and developed an aptamer-based quantification method, which is promising to apply to detect NET in environmental samples.

Inhalable cryptotanshinone spray-dried swellable microparticles for pulmonary fibrosis therapy by regulating TGF-β1/Smad3, STAT3 and SIRT3 pathways

Cryptotanshinone (CTS) is a promising therapeutic option for pulmonary fibrosis (PF). However, clinical applications of CTS are limited owing to high photosensitivity and poor oral bioavailability. Pulmonary drug delivery, especially sustained pulmonary drug delivery, is promising for local treatment of chronic lung diseases. In this study, CTS was encapsulated in an optimized chitosan/L-leucine-based swellable microparticles (SMs) system, which exhibited an appropriate aerosolization performance, sustained release and storage stability. SMs enhanced the in vitro anti-fibrosis efficacy of CTS as shown by the improved cellular uptake. The effect of PF status on in vivo fate of the pulmonary delivered drug was also assessed. Pharmacokinetics and tissue distribution of oral and pulmonary delivery CTS in bleomycin-induced PF rats were compared. Pulmonary delivery exhibited high drug concentrations in pulmonary lesion areas, with reduced exposure to blood and non-targeted tissues after administration at a significantly lower dose compared with oral delivery. Moreover, PF pathological status enhanced activity of SMs, implying that pulmonary delivery was highly effective for PF treatment. Compared to oral delivery, Inhaled SMs showed comparable or even better efficacies at approximately 60-fold low dose compared with oral delivery. A sustained efficacy was observed under a prolonged administration interval (corresponding to half the total dose). Inhalation safety of SMs was established, and important mechanism-related signaling pathways against PF were investigated in vitro and in vivo. In summary, the findings showed that the developed CTS-loaded sustained pulmonary delivery system is a safe and effective strategy for chronic PF treatment.

Advancements in Particle Engineering for Inhalation Delivery of Small Molecules and Biotherapeutics

Dry powder inhalation formulations have become increasingly popular for local and systemic delivery of small molecules and biotherapeutics. Powder formulations provide distinct advantages over liquid formulations such as elimination of cold chain due to room temperature stability, improved portability, and the potential for increasing patient adherence. To become a viable product, it is essential to develop formulations that are stable (physically, chemically and/or biologically) and inhalable over the shelf-life. Physical particulate properties such as particle size, morphology and density, as well as chemical properties can significantly impact aerosol performance of the powder. This review will cover these critical attributes that can be engineered to enhance the dispersibility of inhalation powder formulations. Challenges in particle engineering for biotherapeutics will be assessed, followed by formulation strategies for overcoming the hurdles. Finally, the review will discuss recent examples of successful dry powder biotherapeutic formulations for inhalation delivery that have been clinically assessed.

Effects of L-leucine on the properties of spray-dried swellable microparticles with wrinkled surfaces for inhalation therapy of pulmonary fibrosis

Swellable microparticles (SMs) provide a potential strategy for achieving sustained inhalation therapy. However, spray dried SMs are highly hygroscopic, exhibiting poor flowability and dispersibility properties. This study aimed at determining whether L-leucine (LL) can improve aerosolization performance of SMs with wrinkled surface and its potential mechanisms. Cryptotanshinone was co-spray dried with chitosan and LL (0-40%, mass fraction in carrier materials), after which the production yield, particle size, density, encapsulation efficiency, morphology, cohesion, crystallinity, surface LL distribution, hygroscopicity, water content and in vitro aerosolization performance of the developed formulations were characterized. In addition, we determined whether LL, as a hydrophobic amino acid, would impair swellability and macrophage phagocytosis of SMs. The possible impact of LL on in vitro drug release, cytotoxicity and anti-fibrosis effects on MRC-5 cells was also investigated. As the LL content increased, LL began to crystallize. At 7.5% LL, water content and hygroscopicity of the SMs were at their lowest. Moreover, at 7.5% LL, surface enrichment increased rapidly after which it achieved a comparatively complete coverage at 20-40% LL. However, LL ≥ 20% caused the formation of over-wrinkled, even dimpled or hollow particles, which significantly deteriorated powder properties. Optimum aerosolization performance was obtained at 10% LL, irrespective of its crystallization behavior, accompanied by the lowest cohesion, optimal flowability and production yield, and without impaired swellability, macrophage uptake and anti-fibrosis efficacy. The optimal formulation did not exhibit optimum surface LL coverage, implying that improvement of aerosolization performance of wrinkled SMs by LL not simply depended on its surface enrichment, but its significant influence on morphology and on related powder properties as well.

Engineered-inhaled particles: Influence of carbohydrates excipients nature on powder properties and behavior

Pulmonary drug administration has long been used for local or systemic treatment due to several advantages. Dry powder inhalers emerge as the most promising due to efficiency, ecologic, and drug stability concerns. Coarse lactose-carrier is still the gold standard when inhalation powders are developed. Despite some efforts to produce new types of powders, the lung drug deposition is still poorly controlled, which will ultimately impact therapeutic effectiveness. In this study, we developed "engineered-inhalation powders" using the spray-drying technique. Multiple carbohydrates excipients were binary mixed and combined with two active pharmaceutical ingredients for asthma therapy (budesonide and formoterol). Particle morphology, from spherical to deflated shapes, was characterized by the number and the depth of dimples measured from SEM images. We define a new characteristic deflation ratio ξ as the product between the number of dimples and their depth. Six different powders having opposite morphologies have been selected and we have demonstrated a linear correlation between the fine particle fraction and the deflation ratio of produced powders. Overall, we showed first that the morphology of inhalable powder can be finely tuned by spray-drying technique when excipients varied. Secondly, we developed stable inhalation powders that simultaneously induced high fine particle fractions (>40%) for two drugs due to their deflated surface. The stability has been evaluated for up to 2 months at room temperature.

Targeting of Inhaled Therapeutics to the Small Airways: Nanoleucine Carrier Formulations

Current dry powder formulations for inhalation deposit a large fraction of their emitted dose in the upper respiratory tract where they contribute to off-target adverse effects and variability in lung delivery. The purpose of the current study is to design a new formulation concept that more effectively targets inhaled dry powders to the large and small airways. The formulations are based on adhesive mixtures of drug nanoparticles and nanoleucine carrier particles prepared by spray drying of a co-suspension of leucine and drug particles from a nonsolvent. The physicochemical and aerosol properties of the resulting formulations are presented. The formulations achieve 93% lung delivery in the Alberta Idealized Throat model that is independent of inspiratory flow rate and relative humidity. Largely eliminating URT deposition with a particle size larger than solution pMDIs is expected to improve delivery to the large and small airways, while minimizing alveolar deposition and particle exhalation.

Pulmonary Drug Delivery of Antimicrobials and Anticancer Drugs Using Solid Dispersions

It is well established that currently available inhaled drug formulations are associated with extremely low lung deposition. Currently available technologies alleviate this low deposition problem via mixing the drug with inert larger particles, such as lactose monohydrate. Those inert particles are retained in the inhalation device or impacted in the throat and swallowed, allowing the smaller drug particles to continue their journey towards the lungs. While this seems like a practical approach, in some formulations, the ratio between the carrier to drug particles can be as much as 30 to 1. This limitation becomes more critical when treating lung conditions that inherently require large doses of the drug, such as antibiotics and antivirals that treat lung infections and anticancer drugs. The focus of this review article is to review the recent advancements in carrier free technologies that are based on coamorphous solid dispersions and cocrystals that can improve flow properties, and help with delivering larger doses of the drug to the lungs.

Leucine enhances the dispersibility of trehalose-containing spray-dried powders on exposure to a high-humidity environment

This study investigates the ability of various shell-forming excipients to preserve the dispersibility of dry powder dosage forms, e.g., nasally administered vaccines, upon exposure to a high-humidity environment. Trehalose combinations using leucine, pullulan, or trileucine were selected as the candidate excipient systems, and the powder dispersibility of these systems was compared with that of pure trehalose particles. Scaled-up monodisperse spray drying was used to produce sufficient quantities of uniform-sized particles for powder dispersibility analysis. Particle size, crystallinity, and morphology of the powders before and after exposure to moisture were characterized by an aerodynamic particle sizer, Raman spectroscopy, and scanning electron microscopy, respectively. Three two-component particle systems composed of trehalose/trileucine (97/3 w/w), trehalose/pullulan (70/30 w/w), and trehalose/leucine (70/30 w/w) were first formulated and their dispersibility, characterized as the emitted dose from dry powder inhalers, was then compared with that of trehalose particles. The formulation containing 30% leucine maintained the highest emitted dose (90.3 ± 10%) at a 60 L/min flow rate after 60 min exposure to 90% RH and 25 °C, showing its superior protection against exposure to humidity compared with the other systems. Further investigations under more challenging conditions at a 15 L/min flow rate on the trehalose/leucine system with various compositions (70/30, 80/20, 90/10 w/w) showed that a higher leucine concentration generally provided better protection against moisture and maintained higher powder dispersibility, probably due to higher surface coverage of crystalline leucine and a thicker leucine shell around the particle. The study concludes that leucine may be considered an appropriate shell-forming excipient in the development of dry powder formulations in order to protect the dosage forms against humidity during administration.

Leucine as an excipient in spray dried powder for inhalation

Leucine is a promising excipient with several applications in the development of inhalable spray-dried powder of high- and low-dose drugs. The addition of leucine has exhibited significant enhancing effects on the aerosolization and physical stability of the produced particles. Here, we focus not only on the applications of leucine in inhalable spray-drying powders, but also on the underlying mechanisms by which the formulation and processing parameters dictate the behavior of leucine during the drying process and, therefore, its functionalities within the dried powder. Additionally, we highlight the current regulatory status of leucine. Such insights are important for more efficient utilization of leucine in the future, both for dry powder inhaler formulations and other pharmaceutical applications.

Characterization of excipient enhanced growth (EEG) tobramycin dry powder aerosol formulations

Spray drying can be utilized to produce highly dispersible powder aerosol formulations. However, these formulations are known to be hygroscopic, leading to potential solid-state stability and aerosol performance issues. This study aims to investigate if control of the spray drying particle formation conditions could be employed to improve the solid-state stability and alter the aerosol performance of tobramycin EEG formulations. Eight formulations were prepared, each had the same drug:excipient ratio of 60%^w/_w tobramycin, 20% ^w/_w l-leucine, 18% ^w/_w mannitol, and 2% ^w/_w poloxamer 188. An experimental design matrix was performed with drying air water content of 1 or 10 g/m³ and spray drying solution l-leucine concentrations of 4.6, 7.6, 15.2 or 23.0 mmol/L. The particle size, morphology and crystallinity of spray dried formulations were characterized together with their dynamic moisture vapor sorption and aerosol performance. Higher crystallization and glass transition %RH were observed for the formulations spray dried using drying air with higher water content indicating more stable characteristics. Initial screening using a handheld dry powder inhaler of the realistic aerosol performance revealed that neither changing l-leucine concentration nor the drying gas water content affect the in-vitro expected lung dose. However, using a novel positive pressure inhaler, formulations produced using spray drying solutions with lower l-leucine concentrations showed better aerosol performance with MMAD around 2 µm and FPF < 5 µm around 80%.

Application of void forming index (VFI): Detection of the effect of physical properties of dry powder inhaler formulations on powder cohesion

Dry powder inhaler (DPI) is an attractive alternative for non-invasive drug administration and can make the use of critical biopharmaceutical formulations more convenient for patients. Inhalation of biopharmaceutical formulations can provide targeted delivery to the lungs as well as systemic delivery. Generally, biopharmaceutical DPI formulations consist of highly cohesive powders that tend to agglomerate. For successful delivery to the lungs, the detection of powder cohesiveness and its effect on the performance of the formulations is mandatory. Herein, the effects of the physical properties of mannitol on the cohesiveness of DPI formulations were investigated. The powder cohesion was detected using the void forming index (VFI) measured by inverse gas chromatography (iGC) at 4 h (VFI_4h), which was defined as the pressure drop ratio of 4 h purged sample to that of the initial sample. VFI_4h was found to correlate well with the cohesiveness of DPI formulations. The amount of investigated samples required for VFI measurement was less than that required for conventional measurements. VFI showed a good relationship between the cohesiveness of DPI formulations and the physical properties of mannitol. Thus, VFI can be a reliable standard index to evaluate the cohesiveness of DPI formulations.

Effect of particle surface corrugation on colloidal interactions

HYPOTHESIS

Production of corrugated particles generally introduces several morphological heterogeneities, such as surface roughness and local variations in the corrugation pattern, which are known from model system studies to significantly alter the colloidal interaction energy. Thus, realistic particle morphologies need to be investigated and compared to simple model shapes to yield insights into how interactions are influenced by such morphological heterogeneities.

EXPERIMENTS

We applied the surface element integration method to study the colloidal interactions of electron tomography-based, realistic, corrugated colloidal particles and their symmetric, concave polyhedral analogs by differentiating local surface features to vertices, ridges and ridge networks. We applied molecular modelling to assess the surface access of these features.

FINDINGS

Significant mixing of the interaction energy was found between the different surface features. Larger and smaller energy barrier heights and secondary minimum depths were observed compared to the concave polyhedral models with similar volume or surface area depending on the contacting surface feature. Analysis of surface area distributions suggests that the deviations originate from the altered effective contact distance as a result of surface roughness and other morphological heterogeneities. We also found that the surface access of nanoparticles is greatly impaired at the crevices between the surface corrugations.

The Stabilizing Excipients in Dry State Therapeutic Phage Formulations

Phage therapy has gained prominence due to the increasing pathogenicity of "super bugs" and the rise of their multidrug resistance to conventional antibiotics. Dry state formulation of therapeutic phage is attractive to improve their "druggability" by increasing their shelf life, improving their ease of handling, and ultimately retaining their long-term potency. The use and selection of excipients are critical to stabilize phage in solid formulations and protect their viability from stresses encountered during the solidification process and long-term storage prior to use. Here, this review focuses on the current classes of excipients used to manufacture dry state phage formulations and their ability to stabilize and protect phage throughout the process, as discussed in the literature. We provide perspective of outstanding challenges involved in the formulation of dry state phage. We suggest strategies to improve excipient identification and selection, optimize the potential excipient combinations to improve phage viability during formulation, and evaluate new methodologies that can provide greater insight into phage-excipient interactions to improve design criteria to improve formulation of dry state phage therapeutics. Addressing these challenges opens up new opportunities to re-design and re-imagine phage formulations for improved efficacy as a pharmaceutical product.

Design and Development of Spray-Dried Microsystems to Improve Technological and Functional Properties of Bioactive Compounds from Hazelnut Shells

An extract obtained from hazelnut shells by-products (HSE) has antioxidant and chemopreventive effects on human melanoma and cervical cancer cell lines, inducing apoptosis by caspase-3 activation. A clinical translation is limited by poor water solubility and low bioavailability. Dried plant extracts often show critical characteristics such as sticky/gummy appearance, unpleasant smell, and instability involving practical difficulties in processing for industrial use. A spray drying method has been applied to transform raw HSE in a microparticulate powder. The biopolymeric matrix was based on l-proline as loading carrier, hydroxyethylcellulose in combination with pectin as coating polymers; lecithin and ethanol were used as solubility enhancers. A Hot-Cold-Hot method was selected to prepare the liquid feed. The thus prepared powder showed good technological properties (solid-state, particle dimensions, morphology, and water dissolution rate), stability, and unchanged chemopreventive effects with respect to the unprocessed HSE.

Influence of Composition and Spray-Drying Process Parameters on Carrier-Free DPI Properties and Behaviors in the Lung: A review

Although dry powder inhalers (DPIs) have attracted great interest compared to nebulizers and metered-dose inhalers (MDIs), drug deposition in the deep lung is still insufficient to enhance therapeutic activity. Indeed, it is estimated that only 10–15% of the drug reaches the deep lung while 20% of the drug is lost in the oropharyngeal sphere and 65% is not released from the carrier. The potentiality of the powders to disperse in the air during the patient’s inhalation, the aerosolization, should be optimized. To do so, new strategies, in addition to classical lactose-carrier, have emerged. The lung deposition of carrier-free particles, mainly produced by spray drying, is higher due to non-interparticulate forces between the carrier and drug, as well as better powder uniformity and aerosolization. Moreover, the association of two or three active ingredients within the same powder seems easier. This review is focused on a new type of carrier-free particles which are characterized by a sugar-based core encompassed by a corrugated shell layer produced by spray drying. All excipients used to produce such particles are dissected and their physico-chemical properties (Péclet number, glass transition temperature) are put in relation with the lung deposition ability of powders. The importance of spray-drying parameters on powders’ properties and behaviors is also evaluated. Special attention is given to the relation between the morphology (characterized by a corrugated surface) and lung deposition performance. The understanding of the closed relation between particle material composition and spray-drying process parameters, impacting the final powder properties, could help in the development of promising DPI systems suitable for local or systemic drug delivery.

Physical stability of dry powder inhaler formulations

Introduction: Dry powder inhalers (DPIs) are popular for pulmonary drug delivery. Various techniques have been employed to produce inhalation drug particles and improve the delivery efficiency of DPI formulations. Physical stability of these DPI formulations is critical to ensure the delivery of a reproducible dose to the airways over the shelf-life.Areas covered: This review focuses on the impact of solid-state stability on aerosolization performance of DPI drug particles manufactured by powder production approaches and particle-engineering techniques. It also highlights the different analytical tools that can be used to characterize the physical instability originating from production and storage.Expert opinion: A majority of the DPI literature focuses on the effects of physico-chemical properties such as size, morphology, and density on aerosolization. While little has been reported on the physical stability, particularly the stability of engineered drug particles for use in DPIs. Literature data have shown that different particle-engineering methods and storage conditions may cause physical instability of dry powders for inhalation and can significantly change the aerosol performance. A systematic examination of physical instability mechanisms in DPI formulations is necessary during formulation development in order to select the optimum formulation with satisfactory stability. In addition, the use of appropriate characterization tools is critical to detect and understand physical instability during the development of DPI formulations.