Unraveling Particle Formation: From Single Droplet Drying to Spray Drying and Electrospraying

The value of spray drying as stabilization process for proteins

Protein stability in solution state is often poor due to the intrinsic instability of proteins. A solution is to solidify them by using techniques like freeze or spray drying (SD). To shield therapeutic proteins from stress (e.g., heat or shear stress) related to the solidification process, suitable buffers and excipients are added during formulation development. In this work, buffers and excipients were identified for the stabilization of three protein model compounds (BSA, IgG and lysozyme) in solution state using a design of experiments (DoE) approach based on screening results from differential scanning fluorimetry (DSF) combined with static light scattering (SLS). The aim was to investigate whether it is possible to predict protein stability in solid state using data from protein stabilization in solution state according to DSF/SLS. Therefore, three concepts per protein were analyzed after SD, two of which were expected to stabilize the protein, and one less stabilizing and compared these results to screening results obtained in solution state. Analytical techniques prior to and post SD were reversed-phase and size-exclusion chromatography (RPC and SEC, respectively), dynamic light scattering (DLS), UV and circular dichroism (CD). Furthermore, yield and residual moisture were analyzed. BSA and lysozyme showed high stability during SD and therefore only minor changes were observed. IgG was more affected by solidification which partly resulted in a loss of more than 15 % of the initial protein concentration in comparison to before SD. In future studies, the use of analytical techniques that do not require reconstitution would give additional value.

Uniform Spray Dried Loxapine Microparticles Potentially for Nasal Delivery: Exploring Discriminatory In Vitro Release Evaluation Methods

This study aimed to develop suitable in vitro evaluation methods for the release behavior of nasal powders (NPs). We synthesized a range of standardized microparticles with adjustable size and morphology by co-spray-drying loxapine succinate (LOX) and gelatin (GEL) using an ethanol/water solvent mixture in a self-designed micro-fluidic jet spray dryer (MFJSD). The influence of the LOX/GEL mass ratio and solvent composition on particle characteristics, including size, morphology, and crystalline properties, was systematically investigated. In vitro release profiles of NPs were thoroughly assessed across different release medium, apparatus, and membranes. The modified Transwell® system, utilizing simulated nasal electrolyte solution (SNES) as the release medium, was identified as the most effective in distinguishing the performance of microparticles with diverse attributes. Furthermore, the impact of particle size, morphology, and crystalline properties on in vitro release profiles was discussed. This research presents a robust methodology for the in vitro evaluation of NPs release profiles and provides a practical approach for the rational fabrication of high-quality NPs products.

Complete Breakup of Liquids into Ultrafine Droplets by Grid Turbulence

Ultrafine droplets are crucial in materials processing and nanotechnology, with applications in nanoparticle preparation, water evaporation, nanodrug delivery, nanocoating, among numerous others. While the potential of turbulent gas flow to enhance liquid breakup is acknowledged, constructing turbulence-driven atomizers for ultrafine droplets remains challenging. Herein, we report the innovation of grid-turbulence atomization (GTA), which employs a rotating mesh to deliver liquid and an air knife to spray ultrafine droplets. The airflow across the mesh transitions from laminar flow to grid turbulence, resulting in complete liquid breakup through three stages: bag formation, stretching, and turbulence-induced breakup. Ultrafine water droplets with a 4.8 μm Sauter mean diameter were achieved through GTA. The GTA system demonstrates versatility in atomizing various liquids and proves effective for ultrafine spray-drying. Our strategic methodology establishes a pivotal link between turbulence characteristics and materials processing, influencing a wide range of applications and sparking further innovation in the field.

CFD modelling and simulations of atomization-based processes for production of drug particles: A review

Atomization-based techniques are widely used in pharmaceutical industry for production of fine drug particles due to their versatility and adaptability. Key performance measure of such techniques is their ability to provide control over critical quality attributes (CQAs) of produced drug particles. CQAs of drug particles produced via atomization critically depend on fluid dynamics of sprays; resulting mixing, heat and mass transfer; distribution of supersaturation and subsequent nucleation and growth of particles. It is essential to develop and use computational fluid dynamics (CFD) models for adequate understanding of multi-scale transport processes ranging from molecular scale mixing and particle scale processes, and from atomizer nozzle to overall spray chamber scale establishing relationships between CQAs and design and operating parameters of spray nozzle and chamber. In this work, we critically review past and current research efforts on CFD modelling of pharmaceutical atomization-based processes with an objective to provide clear assessment of the state of the art and to provide recommendations. An overview of the key atomization-based methods for producing drug particles with desired CQAs is presented. Key underlying physical processes and relevant concepts are then outlined. This discussion is related to the demands on CFD models; and state of the art is then discussed with respect to the process needs. Recommendations are provided towards higher fidelity and more efficient models of atomized multiphase flow dynamics and turbulence, drying modelling for the produced particles, and validation approaches. We conclude by highlighting a perceived need for numerical atomization studies with a pharmaceutical context; then, we deliver an outlook on current promising active control and machine learning strategies to augment the shift towards quality-by-design approaches in pharmaceutical manufacturing.

Investigation of co-flow step emulsification (CFSE) microfluidic device and its applications in digital polymerase chain reaction (ddPCR)

HYPOTHESIS

The co-flow step emulsification (CFSE) is very sensitive to the two-phase fluid interfaces, we conjecture that the CFSE hydrodynamic model depends on several key factors and the droplet generation process can be precisely controlled, thus to obtain droplet emulsions with the "ultra-high volume fraction of inner-phase" and "flexible droplet size" characteristics. The resulting droplets are expected to be applied to droplet digital PCR (ddPCR) with "high information density" and "wide dynamic range" advances.

EXPERIMENTS

By combining numerical simulation and fluid dynamics experiments, we have investigated the crucial parameters affecting the CFSE two-phase interface and finally achieved the prediction and guidance for CFSE droplet production.

FINDINGS

With the help of the CFSE device, multivolume droplet populations were produced on demand. Then, ddPCR tests were performed with DNA concentrations from 10 copies/μL to 20,000 copies/μL. The CFSE device owns an ultra-wide dynamic range (up to 5 orders of magnitude), showing excellent quantification ability of nucleic acid targets.

High-Speed Imaging-Based Particle Attribute Analysis of Spray-Dried Amorphous Solid Dispersions Using a Convolution Neural Network

Spray drying is a well-established method for preparing amorphous solid dispersion (ASD) formulations to improve the oral bioavailability of poorly soluble drugs. In addition to the characterization of the amorphous phase, particle attributes of spray-dried intermediates (SDIs), including particle size, morphology, and microstructure, need to be carefully studied and controlled for optimizing drug product performance. Although recent developments in microscopy technology have enabled the analysis of morphological attributes for individual SDI particles, a high-throughput method is highly desirable. In this work, a fingerprinting method exploiting high-speed dynamic imaging, laser diffraction (LD), and a convolutional neural network (CNN) was developed to characterize and quantify size and morphological distributions of particles in batches of spray-dried ASDs. This imaging technology enables the generation of hundreds of thousands of single-particle images in a few minutes that are analyzed by both unsupervised and supervised CNN models. The unsupervised data mining analysis demonstrated that a batch of SDI is a mixture of diverse particle subpopulations with varying sizes and morphological attributes. Motivated by this observation, we developed a CNN model that enabled rapid computation of the volumetric composition of the distinct particle subpopulations in a SDI batch, thus generating a morphological fingerprint. We implemented this high-speed imaging-based particle attribute analysis method to investigate SDIs containing hypromellose acetate succinate as a model system. The CNN fingerprint results enabled quantification of the changes in the morphological distribution of SDI batches prepared with variations in the spray drying process parameters, and the results were in line with the LD and electron microscopy data. Our experiments and analysis demonstrate the robustness and throughput of this fingerprinting approach for quantifying particle size and morphological distributions of individual SDI batches, which can help guide spray drying process development and thereby enable the development of a drug product with more robust process and optimized performance.

Synchrotron computed tomography combined with AI-based image analysis for the advanced characterization of spray dried amorphous solid dispersion particles

Particle engineering aims to design particles with specific properties. A deeper understanding of how particle formation relates to material attributes and process conditions are critical to strengthen knowledge on powder properties and enhance modeling capabilities. New, alternative powder characterization techniques can offer novel and more accurate measures for particle properties, giving more advanced characterization information. In this context, a case study is presented in which spray dried amorphous solid dispersion powders produced by modifying process conditions were characterized by both well-established compendial methods (i.e., laser light diffraction, SEM image analysis, bulk and tapped density, and gas adsorption), as well as a new method combining synchrotron computed tomography (SyncCT) with AI-based image analysis. SyncCT was used to classify and quantify the spray dried particles as hollow spheres and solid particles, giving a more detailed quality measure of the particle shape, as they impact downstream processing differently. Moreover, hollow particle wall thicknesses, as well as internal and external particle surface areas were measured by SyncCT. Altogether, powder characterization data from SyncCT show similar trends to that obtained from compendial techniques and giving additional quality measure regarding particle shape, showing promise of this new and advanced characterization method.

New Insights on the Burst Release Kinetics of Spray-Dried PLGA Microspheres

Spray drying is one of the leading manufacturing methods for active pharmaceutical ingredients (APIs) owing to its rapid, single-step, and cost-effective nature. It also has the capacity to generate microspheres capable of controlled release of APIs including biomolecules and vaccines. However, one of the key challenges of spray-dried formulations especially with poly(lactic-co-glycolic acid) (PLGA)-based controlled-release injectables is burst release, where a significant fraction of the API is released prematurely within a short period of time following administration, leading to detrimental impact on the performance and quality of end products. This study uses a model API, bovine serum albumin (BSA) protein, to identify the sources of burst release that may affect the kinetics and performance of long-acting injectable microsphere formulations. Spray-dried microspheres with various formulations (i.e., variable BSA/PLGA ratios) were characterized in terms of their morphology, particle size, surface area, thermal properties, moisture content, as well as chemical compositions and their distributions to investigate the impact of spray drying on the burst release phenomenon. The results suggest that a relatively high initial release (85%) observed is mainly attributed to the protein distribution close to the particle surface. Morphology analysis provided evidence that the microspheres retained their spherical structure during the burst release phase. X-ray photoelectron spectroscopy, hard X-ray photoelectron spectroscopy, and argon cluster sputtering-assisted time-of-flight secondary ion mass spectrometry analysis suggest an enrichment of PLGA on particle surfaces with buried BSA protein. The statistically significant difference in particle size and surface area between three different formulations may be responsible for an initial variation in release but did not seem to alter the overall burst release profile. Considering the suggested source of burst release, the two-fluid spray-drying method, characterized by a single liquid feed delivering a preprepared emulsion, generated matrix-type microspheres with a surface layer of PLGA, as evidenced by surface analysis. The PLGA surface layer proved to be prone to degradation and pore formation, allowing for faster diffusion of BSA out of the microspheres, resulting in a burst release. Increasing the polymer concentration did not seem to halt this process.

A Novel System for Fabricating Microspheres with Microelectromechanical System-Based Bioprinting Technology

Objective and Impact Statement: The microspheres were widely utilized in the field of life sciences, and we have developed an innovative microelectromechanical system (MEMS)-based bioprinting technology (MBT) system for the preparation of the microspheres. The microspheres can be automatically and high-throughput produced with this cutting-edge system. Introduction and Methods: This paper mainly introduced a novel, efficient, and cost-effective approach for the microsphere fabrication with the MBT system. In this work, the whole microsphere production equipment was built and the optimal conditions (like concentration, drying temperature, frequency, and voltage) for generating uniform hydroxypropyl cellulose-cyclosporine A (HPC-CsA) and poly-l-lactic acid (PLLA) microspheres were explored. Results: Results demonstrated that the optimal uniformity of HPC-CsA microspheres was achieved at 2% (w/v) HPC-CsA mixture, 45 °C (drying temperature), 1,000 Hz (frequency), and 25 V (voltage amplitude). CsA microspheres [coefficient of variation (CV): ~9%] are successfully synthesized, and the drug encapsulation rate was 84.8%. The methodology was further used to produce PLLA microspheres with a diameter of ~2.55 μm, and the best CV value achieved 6.84%. Conclusion: This investigation fully highlighted the integration of MEMS and bioprinting as a promising tool for the microsphere fabrication, and this MBT system had huge potential applications in pharmaceutical formulations and medical aesthetics.

Fabrication of Engineered Drug-Polymer Composite Particles via Piezoelectric Inkjet Technique for Floating Drug Delivery Systems

This study presents a simple approach for fabricating low-density drug-polymer amorphous solid dispersions (ASDs) using a piezoelectric inkjet method, demonstrating potential applications for floating drug delivery systems (FDDS). By adjusting the ratio of two polymers, polylactic acid, and Eudragit RLPO, the floatability and drug release rate of the drug-polymer ASD particles can be easily manipulated. Kinetic model analyses have been conducted to interpret the drug release mechanism. This work offers a robust platform for exploring diverse polymer-drug combinations that are applicable to FDDS.

Formulation strategies, preparation methods, and devices for pulmonary delivery of biologics

Biological products, including vaccines, blood components, and recombinant therapeutic proteins, are derived from natural sources such as humans, animals, or microorganisms and are typically produced using advanced biotechnological methods. The success of biologics, particularly monoclonal antibodies, can be attributed to their favorable safety profiles and target specificity. However, their large molecular size presents significant challenges in drug delivery, particularly in overcoming biological barriers. Pulmonary delivery has emerged as a promising route for administering biologics, offering non-invasive delivery with rapid absorption, high systemic bioavailability, and avoidance of first-pass metabolism. This review first details the anatomy and physiological barriers of the respiratory tract and the associated challenges of pulmonary drug delivery (PDD). It further discusses innovations in PDD, the impact of particle size on drug deposition, and the use of secondary particles, such as nanoparticles, to enhance bioavailability and targeting. The review also explains various devices used for PDD, including dry powder inhalers (DPIs) and nebulizers, highlighting their advantages and limitations in delivering biologics. The role of excipients in improving the stability and performance of inhalation products is also addressed. Since dry powders are considered the suitable format for delivering biomolecules, particular emphasis is placed on the excipients used in DPI development. The final section of the article reviews and compares various dry powder manufacturing methods, clarifying their clinical relevance and potential for future applications in the field of inhalable drug formulation.

Electrostatic spraying for fine-tuning particle dimensions to enhance oral bioavailability of poorly water-soluble drugs

While spray-drying has been widely utilized to improve the bioavailability of poorly water-soluble drugs, the outcomes often exhibit suboptimal particle size distribution and large particle sizes, limiting their effectiveness. In this study, we introduce electrostatic spraying as an advanced technology tailored for poorly water-soluble drugs, enabling the fabrication of nanoparticles with fine and uniform particle size distribution. Regorafenib (1 g), as a model drug, copovidone (5 g), and sodium dodecyl sulfate (0.1 g) were dissolved in 200 ml ethanol and subjected to conventional-spray-dryer and electrostatic spray dryer. The electrostatic spray-dried nanoparticles (ESDN) showed smaller particle sizes with better uniformity compared to conventional spray-dried nanoparticles (CSDN). ESDN demonstrated significantly enhanced solubility and rapid release in water. In vitro studies revealed that ESDN induced apoptosis in HCT-116 cells to a greater extent, exhibiting superior cytotoxicity compared to CSDN. Furthermore, ESDN substantially improved oral bioavailability and antitumor efficacy compared to CSDN. These findings suggest that ESD shows potential in developing enhanced drug delivery systems for poorly water-soluble drugs, effectively addressing the limitations associated with CSD methods.

Characteristics of a Spray-Dried Porcine Blood Meal for Aedes aegypti Mosquitoes

Research into mosquito-borne illnesses faces hurdles because feeding fresh animal blood to rear female mosquitoes presents logistical, economic, and safety challenges. In this study, a shelf-stable additive (spray-dried porcine blood; SDPB) hypothesized to supply accessible hemoglobin was evaluated within an alternative meal (AM) containing whey powder and PBS for rearing the yellow fever mosquito Aedes aegypti. LC-MS/MS proteomics, microbial assays, and particle reduction techniques confirmed and characterized the functionality of hemoglobin in SDPB, while engorgement, fecundity, egg viability, and meal stability bioassays assessed AM performance. Chemical assays supported hemoglobin as the phagostimulant in SDPB with aggregates partially solubilized in the AM that can be more accessible via particle reduction. Unpaired two-tailed t-tests indicate that the AM stimulates oogenesis (t11 = 13.6, p = 0.003) and is stable under ambient (1+ y; t12 = 0.576, p = 0.575) and aqueous (14 d; t12 = 0.515, p = 0.639) conditions without decreasing fecundity. Egg hatch rates for the ninth generation of AM-reared Ae. aegypti were 50-70+%. With further development, this meal may serve as a platform for mass rearing or studying effects of nutritional additives on mosquito fitness due to its low cost and stability. Future work may examine tuning spray drying parameters and resulting impacts on hemoglobin agglomeration and feeding.

Stabilization of an Infectious Enveloped Virus by Spray-Drying and Lyophilization

Enveloped viruses are attractive candidates for use as gene- and immunotherapeutic agents due to their efficacy at infecting host cells and delivering genetic information. They have also been used in vaccines as potent antigens to generate strong immune responses, often requiring fewer doses than other vaccine platforms as well as eliminating the need for adjuvants. However, virus instability in liquid formulations may limit their shelf life and require that these products be transported and stored under stringently controlled temperature conditions, contributing to high cost and limiting patient access. In this work, spray-drying and lyophilization were used to embed an infectious enveloped virus within dry, glassy polysaccharide matrices. No loss of viral titer was observed following either spray-drying (at multiple drying gas temperatures) or lyophilization. Furthermore, viruses embedded in the glassy formulations showed enhanced thermal stability, retaining infectivity after exposure to elevated temperatures as high as 85 °C for up to one hour, and for up to 10 weeks at temperatures as high as 30 °C. In comparison, viruses in liquid formulations lost infectivity within an hour at temperatures above 40 °C, or after incubation at 25 °C for longer periods of time.

Spray-dried ternary bioactive glass microspheres: Direct and indirect structural effects of copper-doping on acellular degradation behavior

Silicate-based bioactive glass nano/microspheres hold significant promise for bone substitution by facilitating osteointegration through the release of biologically active ions and the formation of a biomimetic apatite layer. Cu-doping enhances properties such as pro-angiogenic and antibacterial behavior. While sol-gel methods usually yield homogeneous spherical particles for pure silica or binary glasses, synthesizing poorly aggregated Cu-doped ternary glass nano/microparticles without a secondary CuO crystalline phase remains challenging. This article introduces an alternative method for fabricating Cu-doped ternary microparticles using sol-gel chemistry combined with spray-drying. The resulting microspheres exhibit well-defined, poorly aggregated particles with spherical shapes and diameters of a few microns. Copper primarily integrates into the microspheres as Cu0 nanoparticles and as Cu2+ within the amorphous network. This doping affects silica network connectivity, as calcium and phosphorus are preferentially distributed in the glass network (respectively as network modifiers and formers) or involved in amorphous calcium phosphate nano-domains depending on the doping rate. These differences affect the interaction with simulated body fluid. Network depolymerization, ion release (SiO44-, Ca2+, PO43-, Cu2+), and apatite nanocrystal layer formation are impacted, as well as copper release. The latter is mainly provided by the copper involved in the silica network and not from metal nanoparticles, most of which remain in the microspheres after interaction. This understanding holds promising implications for potential therapeutic applications, offering possibilities for both short-term and long-term delivery of a tunable copper dose. STATEMENT OF SIGNIFICANCE: A novel methodology, scalable to industrial levels, enables the synthesis of copper-doped ternary bioactive glass microparticles by combining spray-drying and sol-gel chemistry. It provides precise control over the copper percentage in microspheres. This study explores the influence of synthesis conditions on the copper environment, notably Cu0 and Cu2+ ratios, characterized by EPR spectroscopy, an aspect poorly described for copper-doped bioactive glass. Additionally, copper indirectly affects silica network connectivity and calcium/phosphorus distribution, as revealed by SSNMR. Multiscale characterization illustrates how these features impact acellular degradation in simulated body fluid, highlighting the therapeutic potential for customizable copper dosing to address short- and long-term needs.

Single droplet drying with stepwise changing temperature-time trajectories: Influence on heat sensitive constituents

Optimization procedures for industrial spray drying processes mainly rely on empirical understanding. Mechanistic understanding of the process is limited, but can be enhanced by studying the drying of single droplets. We here report on a new sessile single droplet drying platform, using two air streams to represent the inlet and outlet air of a spray dryer to simulate changing conditions in a spray dryer. Accurate temperature measurements confirmed the temperature profiles and their imposition onto a drying droplet. Single droplets of solutions containing β-galactosidase and maltodextrin were dried with different temperature-time trajectories, with the inactivation of the enzyme as indicator for the thermal load on the droplet. The locking point is found to be an important parameter: the air temperature before this point does not influence the enzyme inactivation much, but a high air temperature after the locking point results in significant inactivation. The β-galactosidase inactivation was also successfully predicted with a coupled drying and inactivation model.

Use of Electrospinning for Sustainable Production of Nanofibers: A Comparative Assessment of Smart Textiles-Related Applications

Textile production is a major component of the global industry, with sales of over USD 450 billion and estimations of an 84% increase in their demand in the next 20 years. In recent decades, protective and smart textiles have played important roles in the social economy and attracted widespread popularity thanks to their wide spectrum of applications with properties, such as antimicrobial, water-repellent, UV, chemical, and thermal protection. Towards the sustainable manufacturing of smart textiles, biodegradable, recycled, and bio-based plastics are used as alternative raw materials for fabric and yarn production using a wide variety of techniques. While conventional techniques present several drawbacks, nanofibers produced through electrospinning have superior structural properties. Electrospinning is an innovative method for fiber production based on the use of electrostatic force to create charged threads of polymer solutions. Electrospinning shows great potential since it provides control of the size, porosity, and mechanical resistance of the fibers. This review summarizes the advances in the rapidly evolving field of the production of nanofibers for application in smart and protective textiles using electrospinning and environmentally friendly polymers as raw materials, and provides research directions for optimized smart fibers in the future.

Solid-state analysis for pharmaceuticals: Pathways to feasible and meaningful analysis

The solid state of matter is the preferred starting point for designing a pharmaceutical product. This is driven by both patient preferences and the relative ease of supplying a solid pharmaceutical product with desired quality and performance. Solid form diversity is increasingly prevalent as a crucial element in designing these products, which underpins the importance of solid-state analytical methods. This paper provides a critical analysis of challenges related to solid-state analytics, as well as considerations and suggestions for feasible and meaningful pharmaceutical analysis.

Airborne virus transmission: Increased spreading due to formation of hollow particles

The globally supported social distancing rules to prevent airborne transmission of COVID-19 assume small saliva droplets evaporate fast and large ones, which contain most viral copies, fall fast to the ground. However, during evaporation, solutes distribute non-uniformly within the droplets. We developed a numerical model to predict saliva droplet drying in different environments. We represent saliva droplets as a solution of NaCl mixed with water. In a hot and dry ambiance, the solutes form a shell on the droplets' surface, producing light, hollow particles. These hollow particles have a larger cross-sectional area compared to their solid counterparts and can float longer and travel farther in the air. We introduced the "hollowness factor," which serves as a measure of the ratio of the volume of a hollow particle and the volume of a solid residue formed during droplet drying. Through our investigations, we determined that under specific conditions, namely an ambient humidity level of 10% and a temperature of 40°C, the highest hollowness factor observed was 1.610. This finding indicates that in the case of hollow particle formation, the droplet nucleus expands by a factor of 1.610 compared to its original size.

Investigation of the Impact of Saccharides on the Relative Activity of Trypsin and Catalase after Droplet and Spray Drying

While using saccharides as stabilizers for therapeutic protein drying is common, the mechanisms underlying the stabilization during drying remain largely unexplored. Herein, we investigated the effect of different saccharides, trehalose dihydrate (TD), dextran (DEX), and hydroxypropyl β-cyclodextrins (low substitution-HP and high substitution-HPB), on the relative activities of the enzymes trypsin and catalase during miniaturized drying (MD) or spray drying (SD). For trypsin, the presence of saccharides, especially HP, was beneficial, as it significantly improved the enzyme activity following MD. The HPB preserved trypsin's activity during MD and SD. Adding saccharides during MD did not show a notable improvement in catalase activities. Increasing TD was beneficial during the SD of catalase, as indicated by significantly increased activity. Molecular docking and molecular dynamics simulations oftrypsin with HP or HPB revealed the influence of their substitution on the binding affinity for the enzyme. A higher affinity of HP to bind trypsin and itself was observed during simulations. Experimentally, activity reduction was mainly observed during MD, attributable to the higher droplet temperature during MD than during SD. The activities from the experiments and aggregation propensity from molecular modeling helped elucidate the impact of the size of protein and saccharides on preserving the activity during drying.

Dragon's Blood Sap Microencapsulation within Whey Protein Concentrate and Zein Using Electrospraying Assisted by Pressurized Gas Technology

Dragon's blood sap (DBS) obtained from the bark of Croton lechleri (Müll, Arg.) is a complex herbal remedy of pharmacological interest due to its high content in polyphenols, specifically proanthocyanidins. In this paper, electrospraying assisted by pressurized gas (EAPG) was first compared with freeze-drying to dry natural DBS. Secondly, EAPG was used for the first time to entrap natural DBS at room temperature into two different encapsulation matrices, i.e., whey protein concentrate (WPC) and zein (ZN), using different ratios of encapsulant material: bioactive compound, for instance 2:1 w/w and 1:1 w/w. The obtained particles were characterized in terms of morphology, total soluble polyphenolic content (TSP), antioxidant activity, and photo-oxidation stability during the 40 days of the experiment. Regarding the drying process, EAPG produced spherical particles with sizes of 11.38 ± 4.34 µm, whereas freeze-drying produced irregular particles with a broad particle size distribution. However, no significant differences were detected between DBS dried by EAPG or freeze-drying in TSP, antioxidant activity, and photo-oxidation stability, confirming that EAPG is a mild drying process suitable to dry sensitive bioactive compounds. Regarding the encapsulation process, the DBS encapsulated within the WPC produced smooth spherical microparticles, with average sizes of 11.28 ± 4.28 µm and 12.77 ± 4.54 µm for ratios 1:1 w/w and 2:1 w/w, respectively. The DBS was also encapsulated into ZN producing rough spherical microparticles, with average sizes of 6.37 ± 1.67 µm and 7.58 ± 2.54 µm for ratios 1:1 w/w and 2:1 w/w, respectively. The TSP was not affected during the encapsulation process. However, a slight reduction in antioxidant activity measured by DPPH was observed during encapsulation. An accelerated photo-oxidation test under ultraviolet light confirmed that the encapsulated DBS showed an increased oxidative stability in comparison with the non-encapsulated DBS, with the stability being enhanced for the ratio of 2:1 w/w. Among the encapsulating materials and according to the ATR-FTIR results, ZN showed increased protection against UV light. The obtained results demonstrate the potential of EAPG technology in the drying or encapsulation of sensitive natural bioactive compounds in a continuous process available at an industrial scale, which could be an alternative to freeze-drying.

Internal microstructure of spray dried particles affects viral vector activity in dry vaccines

To maintain the activity of sensitive biologics during encapsulation by spray drying, a better understanding of deactivation pathways in dried particles is necessary. The effect of solid-air interfaces within dried particles on viral deactivation was examined with three binary excipient blends, mannitol/dextran (MD), xylitol/dextran (XD), and lactose/trehalose (LT). Particles encapsulating human serotype 5 adenovirus viral vector (AdHu5) were produced via both spray drying and acoustic levitation. The particles' internal microstructure was directly visualized, and the location of a viral vector analogue was spatially mapped within the particles by volume imaging using focused ion beam sectioning and scanning electron microscopy. The majority of the viral vector analogue was found at, or near, the solid-air interfaces. Peclet number and crystallization kinetics governed the internal microstructure of the particles: XD particles with minimal internal voids retained the highest viral activity, followed by MD particles with a few large voids, and finally LT particles with numerous internal voids exhibited the lowest viral activity. Overall, AdHu5 activity decreased as the total solid-air interfacial area increased (as quantified by nitrogen sorption). Along with processing losses, this work highlights the importance of surface area within particles as an indicator of activity losses for dried biologics.

Impact of Different Saccharides on the In-Process Stability of a Protein Drug During Evaporative Drying: From Sessile Droplet Drying to Lab-Scale Spray Drying

OBJECTIVES

Solid biopharmaceutical products can circumvent lower temperature storage and transport and increase remote access with lower carbon emissions and energy consumption. Saccharides are known stabilizers in a solid protein produced via lyophilization and spray drying (SD). Thus, it is essential to understand the interactions between saccharides and proteins and the stabilization mechanism.

METHODS

A miniaturized single droplet drying (MD) method was developed to understand how different saccharides stabilize proteins during drying. We applied our MD to different aqueous saccharide-protein systems and transferred our findings to SD.

RESULTS

The poly- and oligosaccharides tend to destabilize the protein during drying. The oligosaccharide, Hydroxypropyl β-cyclodextrin (HPβCD) shows high aggregation at a high saccharide-to-protein molar ratio (S/P ratio) during MD, and the finding is supported by nanoDSF results. The polysaccharide, Dextran (DEX) leads to larger particles, whereas HPBCD leads to smaller particles. Furthermore, DEX is not able to stabilize the protein at higher S/P ratios either. In contrast, the disaccharide Trehalose Dihydrate (TD) does not increase or induce protein aggregation during the drying of the formulation. It can preserve the protein's secondary structure during drying, already at low concentrations.

CONCLUSION

During the drying of S/P formulations containing the saccharides TD and DEX, the MD approach could anticipate the in-process (in) stability of protein X at laboratory-scale SD. In contrast, for the systems with HPβCD, the results obtained by SD were contradictory to MD. This underlines that depending on the drying operation, careful consideration needs to be applied to the selection of saccharides and their ratios.

Improved drug transfer into brain tissue via the "nose-to-brain" approach using suspension or powder formulations based on the amorphous solid dispersion technique

Intranasal administration has attracted increasing attention as a drug delivery approach based on nose-to-brain drug delivery from the nasal cavity to brain tissue directly, bypassing the blood-brain barrier. However, application of the method to poorly water-soluble drugs is potentially limited due to low aqueous solubility and dissolution, which can hinder drug transfer to brain tissue. In the present study, we focused on an amorphous solid dispersion (ASD) technique to improve drug dissolution. A carbamazepine-loaded ASD model drug was prepared using the solvent evaporation method (ASD-1). After screening six water-soluble polymer carriers, polyvinyl alcohol (PVA)-based ASD-1 formulation exhibited the most rapid and highest drug dissolution under experimental conditions in the nasal cavity (pH 6.0). A carbamazepine suspension dispersed with a PVA-ASD-1 formulation exhibited enhanced drug delivery into plasma and brain tissue of rats in vivo. A spray-dried powder formulation of PVA-ASD (PVA-ASD-2) exhibited improved drug dissolution and in vivo drug transfer. Our key finding is that the spray-dried PVA-ASD-2 formulation exhibited higher brain/plasma ratios than the PVA-ASD-1 suspension formulation. Our physical characterization data and demonstration of improved drug transfer suggest that ASD-based intranasal formulations hold promise for drug delivery to the brain.

Encapsulation of enzymes in food industry using spray drying: recent advances and process scale-ups

Enzymes are widely used in the food industry due to their ability in improving the functional, sensory, and nutritional properties of food products. However, their poor stability under harsh industrial conditions and their compromised shelf-lives during long-term storage limit their applications. This review introduces typical enzymes and their functionality in the food industry and demonstrates spray drying as a promising approach for enzyme encapsulation. Recent studies on encapsulation of enzymes in the food industry using spray drying and the key achievements are summarized. The latest developments including the novel design of spray drying chambers, nozzle atomizers and advanced spray drying techniques are also analyzed and discussed in depth. In addition, the scale-up pathways connecting laboratory scale trials and industrial scale productions are illustrated, as most of the current studies have been limited to lab-scales. Enzyme encapsulation using spray drying is a versatile strategy to improve enzyme stability in an economical and industrial viable way. Various nozzle atomizers and drying chambers have recently been developed to increase process efficiency and product quality. A comprehensive understanding of the complex droplet-to-particle transformations during the drying process would be beneficial for both process optimization and scale-up design.

Electrosprayed Particles Loaded with Kartogenin as a Potential Osteochondral Repair Implant

The restoration of cartilage damage is a slow and not always successful process. Kartogenin (KGN) has significant potential in this space-it is able to induce the chondrogenic differentiation of stem cells and protect articular chondrocytes. In this work, a series of poly(lactic-co-glycolic acid) (PLGA)-based particles loaded with KGN were successfully electrosprayed. In this family of materials, PLGA was blended with a hydrophilic polymer (either polyethyleneglycol (PEG) or polyvinylpyrrolidone (PVP)) to control the release rate. Spherical particles with sizes in the range of 2.4-4.1 µm were fabricated. They were found to comprise amorphous solid dispersions, with high entrapment efficiencies of >93%. The various blends of polymers had a range of release profiles. The PLGA-KGN particles displayed the slowest release rate, and blending with PVP or PEG led to faster release profiles, with most systems giving a high burst release in the first 24 h. The range of release profiles observed offers the potential to provide a precisely tailored profile via preparing physical mixtures of the materials. The formulations are highly cytocompatible with primary human osteoblasts.

A Comparison of Spray-Drying and Co-Precipitation for the Generation of Amorphous Solid Dispersions (ASDs) of Hydrochlorothiazide and Simvastatin

Co-processing of APIs, the practice of creating multi-component APIs directly in chemical processing facilities used to make drug substance, is gaining increased attention with a view to streamlining manufacturing, improving supply chain robustness and accessing enhanced product attributes in terms of stability and bioavailability. Direct co-precipitation of amorphous solid dispersions (ASDs) at the final step of chemical processing is one such example of co-processing. The purpose of this work was to investigate the application of different advanced solvent-based processing techniques - direct co-precipitation (CP) and the benchmark well-established spray-drying (SD) process - to the production of ASDs comprised of a drug with a high T_g (hydrochlorothiazide, HCTZ) or a low T_g (simvastatin, SIM) molecularly dispersed in a PVP/VA 64 or Soluplus® matrix. ASDs of the same composition were manufactured by the two different methods and were characterised using powder X-ray diffraction (PXRD), modulated differential scanning calorimetry (mDSC), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy (SEM). Both methods produced ASDs that were PXRD amorphous, with some differences, depending on the process used, in glass transition temperature and particle size distribution. Irrespective of manufacturing method used, all ASDs remained PXRD amorphous when subjected to high relative humidity conditions (75% RH, 25°C) for four weeks, although changes in the colour and physical characteristics were observed on storage for spray-dried systems with SIM and PVP/VA 64 copolymer. The particle morphology differed for co-precipitated compared to spray dried systems, with powder generated by the former process being comprised of more irregularly shaped particles of larger particle size when compared to the equivalent spray-dried systems which may enable more streamlined drug product processes to be used for CP materials. These differences may have implications in downstream drug product processing. A limitation identified when applying the solvent/anti-solvent co-precipitation method to SIM was the high antisolvent to solvent ratios required to effect the precipitation process. Thus, while similar outcomes may arise for both co-precipitation and spray drying processes in terms of ASD critical quality attributes, practical implications of applying the co-precipitation method and downstream processability of the resulting ASDs should be considered when choosing one solvent-based ASD production process over another.

Engineering the right formulation for enhanced drug delivery

Dry powder inhalers (DPIs) can be used with a wide range of drugs such as small molecules and biologics and offer several advantages for inhaled therapy. Early DPI products were intended to treat asthma and lung chronic inflammatory disease by administering low-dose, high-potency drugs blended with lactose carrier particles. The use of lactose blends is still the most common approach to aid powder flowability and dose metering in DPI products. However, this conventional approach may not meet the high demand for formulation physical stability, aerosolisation performance, and bioavailability. To overcome these issues, innovative techniques coupled with modification of the traditional methods have been explored to engineer particles for enhanced drug delivery. Different particle engineering techniques have been utilised depending on the types of the active pharmaceutical ingredient (e.g., small molecules, peptides, proteins, cells) and the inhaled dose. This review discusses the challenges of formulating DPI formulations of low-dose and high-dose small molecule drugs, and biologics, followed by recent and emerging particle engineering strategies utilised in developing the right inhalable powder formulations for enhanced drug delivery.

Microencapsulation of steroidal saponins from agave sap concentrate using different carriers in spray drying

Concentrated agave sap is a product with in vivo proven hypocholesterolemic and hypoglycemic activities, as well as in vitro anticancer potential. In the present work, a factorial design was used to determine the suitable drying conditions of concentrated agave by studying the effect of inlet temperature (150 °C, 180 °C and 210 °C) and the type of carrier agent (maltodextrin, hydroxypropyl methylcellulose, guar gum and xanthan gum). The response variables for each treatment were the product recovery and microencapsulated saponins. Further characterization of concentrated agave powders was performed: solubility in water, hygroscopicity, moisture content, tap density, bulk density, Carr's index followability and morphology by scanning electron microscopy analysis. The hydroxypropyl methylcellulose proved to improve physicochemical properties and enhance product yield, using 210 °C inlet temperature and a mix of carrier agents of maltodextrin/hydroxypropyl methylcellulose/xanthan gum at 50/48.5/1.5 (w/w/w) proportion exhibited the highest saponin recovery of 53.81%. Moreover, different carrier agents in powders revealed two shapes, regular spherical shape with smooth surface and collapsed shapes. The use of polymers excipients helped to decrease the stickiness of the desired product and enhanced the powder stability and microencapsulation of the steroidal saponins.

Supercritical CO2 Assisted Electrospray to Produce Poly(lactic-co-glycolic Acid) Nanoparticles

This work proposes an improvement of the traditional electrospraying process, in which supercritical carbon dioxide (SC-CO2) is used to produce poly(lactic-co-glycolic acid) (PLGA) nanoparticles. The experiments were performed at different PLGA concentrations (1, 3 and 5% w/w), applied voltages (10 and 30 kV) and operating pressures (80, 120 and 140 bar). It was found that working at 140 bar and 30 kV, spherical nanoparticles, with mean diameters of 101 ± 13 nm and 151 ± 45 nm, were obtained, when solutions at 1% w/w and 3% w/w PLGA were electrosprayed, respectively. Increasing PLGA concentration up to 5% w/w, a mixture of fibers and particles was observed, indicating the transition to the electrospinning regime.

Alginate Particles for Enzyme Immobilization Using Spray Drying

Enzymes are important catalysts for biological processes due to their high catalytic activity and selectivity. However, their low thermal stability limited their industrial applications. The present work demonstrates a simple and effective method for enzyme immobilization via spray drying. Alginate was used as a support material. Phytase, an important enzyme in the animal feed industry, was selected to study the effect of enzyme immobilization using alginate particles on its thermal stability. The physicochemical properties of alginate particles such as size, surface morphology, and heat resistance were studied. Successful immobilization of phytase was confirmed by confocal microscopy, and the immobilized phytase retained 58% of its original activity upon heating at 95 °C, compared to 4% when the alginate support material was absent. Phytase was released promptly in a simulated gastrointestinal tract with >95% of its original activity recovered. The spray drying method for phytase immobilization is scalable and applicable to other enzymes for various applications.

Spray dried hydroxyapatite-based supraparticles with uniform and controllable size and morphology

This work aims to prepare uniform spray dried hydroxyapatite-based (SD HAP-based) supraparticles with controllable morphology via micro-fluidic spray drying. Sodium polyacrylate (PAAS) and sodium chloride (NaCl) were used to prepare the precursor suspensions by regulating the inter-particle repulsive forces and electrostatic shielding effect, respectively. The particle size (D50) and zeta potential of the suspension were highly associated with the mass ratio of HAP to PAAS (m_H/m_P) and the NaCl concentration (C_NaCl), which further had significant effect on the permeability (k) of the droplet shell formed during spray drying and ultimately the supraparticle morphology. D50 ˂ 2 µm and absolute zeta potential ˃ 20 mV, obtained when m_H/m_P ˂ 100 under low C_NaCl, rendered ultralow k and consequently deformed supraparticles; Whereas D50 ˃ 2 µm and absolute zeta potential ˂ 20 mV, achieved by decreasing PAAS amount, i.e. m_H/m_P ≥ 100 or improving C_NaCl to efficiently screen surface net charge of HAP, high k and spherical supraparticles were thus preferentially formed.

Gaining Insight into the Role of the Solvent during Spray Drying of Amorphous Solid Dispersions by Studying Evaporation Kinetics

Spray drying is one of the most commonly used manufacturing techniques for amorphous solid dispersions (ASDs). During spray drying, very fast solvent evaporation is enabled by the generation of small droplets and exposure of these droplets to a heated drying gas. This fast solvent evaporation leads to an increased viscosity that enables kinetic trapping of an active pharmaceutical ingredient (API) in a polymer matrix, which is favorable for the formulation of supersaturated, kinetically stabilized ASDs. In this work, the relation between the solvent evaporation rate and the kinetic stabilization of highly drug-loaded ASDs was investigated. Accordingly, thermal gravimetric analysis (TGA) was employed to study the evaporation kinetics of seven organic solvents and the influence of solutes, i.e., poly(vinylpyrrolidone-co-vinyl acetate) (PVPVA), fenofibrate (FNB), and naproxen (NAP), on the evaporation behavior. At 10 °C below the boiling point of the respective solvent, methanol (MeOH) had the lowest evaporation rate and dichloromethane (DCM) had the highest. PVPVA decreased the evaporation rate for all solvents, yet this effect was more pronounced for the relatively faster evaporating solvents. The APIs had opposite effects on the evaporation process: FNB increased the evaporation rate, while NAP decreased it. The latter might indicate the presence of interactions between NAP and the solvent or NAP and PVPVA, which was further investigated using Fourier transform-InfraRed (FT-IR) spectroscopy. Based on these findings, spray drying process parameters were adapted to alter the evaporation rate. Increasing the evaporation rate of MeOH and DCM enabled the kinetic stabilization of higher drug loadings of FNB, while the opposite trend was observed for ASDs of NAP. Even when higher drug loadings could be kinetically stabilized by adapting the process parameters, the improvement was limited, demonstrating that the phase behavior of these ASDs of FNB and NAP immediately after preparation was predominantly determined by the API-polymer-solvent combination rather than the process parameters applied.

Polysaccharide-based formulations as potential carriers for pulmonary delivery - A review of their properties and fates

Polysaccharides can be elite carriers for therapeutic molecules due to their versatility and low probability to trigger toxicity and immunogenic responses. Local and systemic therapies can be achieved through particle pulmonary delivery, a promising non-invasive alternative. Successful pulmonary delivery requires particles with appropriate flowability to reach alveoli and avoid premature clearance mechanisms. Polysaccharides can form micro-, nano-in-micro-, and large porous particles, aerogels, and hydrogels. Herein, the characteristics of polysaccharides used in drug formulations for pulmonary delivery are reviewed, providing insights into structure-function relationships. Charged polysaccharides can confer mucoadhesion, whereas the ability for specific sugar recognition may confer targeting capacity for alveolar macrophages. The method of particle preparation must be chosen considering the properties of the components and the delivery device to be utilized. The fate of polysaccharide-based carriers is dependent on enzyme-triggered hydrolytic and/or oxidative mechanisms, allowing their complete degradation and elimination through urine or reutilization of released monosaccharides.

Thermodynamic Balance vs. Computational Fluid Dynamics Approach for the Outlet Temperature Estimation of a Benchtop Spray Dryer

The use of design space (DS) is a key milestone in the quality by design (QbD) of pharmaceutical processes. It should be considered from early laboratory development to industrial production, in order to support scientists with making decisions at each step of the product’s development life. Presently, there are no available data or methodologies for developing models for the implementation of design space (DS) on laboratory-scale spray dryers. Therefore, in this work, a comparison between two different modeling approaches, thermodynamics and computational fluid dynamics (CFD), to a laboratory spray dryer model have been evaluated. The models computed the outlet temperature (Tout) of the process with a new modeling strategy that includes machine learning to improve the model prediction. The model metrics calculated indicate how the thermodynamic model fits Tout data better than CFD; indeed, the error of the CFD model increases towards higher values of Tout and feed rate (FR), with a final mean absolute error of 10.43 K, compared to the 1.74 K error of the thermodynamic model. Successively, a DS of the studied spray dryer equipment has been implemented, showing how Tout is strongly affected by FR variation, which accounts for about 40 times more than the gas flow rate (Gin) in the DS. The thermodynamic model, combined with the machine learning approach here proposed, could be used as a valid tool in the QbD development of spray-dried pharmaceutical products, starting from their early laboratory stages, replacing traditional trial-and-error methodologies, preventing process errors, and helping scientists with the following scale-up.

Inhalable Microparticles Embedding Calcium Phosphate Nanoparticles for Heart Targeting: The Formulation Experimental Design

Inhalation of Calcium Phosphate nanoparticles (CaPs) has recently unmasked the potential of this nanomedicine for a respiratory lung-to-heart drug delivery targeting the myocardial cells. In this work, we investigated the development of a novel highly respirable dry powder embedding crystalline CaPs. Mannitol was selected as water soluble matrix excipient for constructing respirable dry microparticles by spray drying technique. A Quality by Design approach was applied for understanding the effect of the feed composition and spraying feed rate on typical quality attributes of inhalation powders. The in vitro aerodynamic behaviour of powders was evaluated using a medium resistance device. The inner structure and morphology of generated microparticles were also studied. The 1:4 ratio of CaPs/mannitol led to the generation of hollow microparticles, with the best aerodynamic performance. After microparticle dissolution, the released nanoparticles kept their original size.

Electrospun PVP-Core/PHBV-Shell Fibers to Eliminate Tailing Off for an Improved Sustained Release of Curcumin

Tailing off release in the sustained release of water-insoluble curcumin (Cur) is a significant challenge in the drug delivery system. As a novel solution, core-shell nanodrug containers have aroused many interests due to their potential improvement in drug-sustained release. In this work, a biodegradable polymer, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), and hydrophilic polyvinylpyrrolidone (PVP) were exploited as drug delivery carriers by coaxial electrospinning, and the core-shell drug-loaded fibers exhibited improved sustained release of Cur. A cylindrical morphology and a clear core-shell structure were observed by scanning and transmission electron microscopies. The X-ray diffraction pattern and infrared spectroscopy revealed that Cur existed in amorphous form due to its good compatibility with PHBV and PVP. The in vitro drug release curves confirmed that the core-shell container manipulated Cur in a faster drug release process than that in the traditional PHBV monolithic container. The combination of the material and structure forms a novel nanodrug container with a better sustained release of water-insoluble Cur. This strategy is beneficial for exploiting more functional biomedical materials to improve the drug release behavior.

Water evaporation from solute-containing aerosol droplets: Effects of internal concentration and diffusivity profiles and onset of crust formation

The evaporation of droplets is an important process not only in industrial and scientific applications, but also in the airborne transmission of viruses and other infectious agents. We derive analytical and semi-analytical solutions of the coupled heat and mass diffusion equations within a spherical droplet and in the ambient vapor phase that describe the evaporation process of aqueous free droplets containing nonvolatile solutes. Our results demonstrate that the solute-induced water vapor-pressure reduction considerably slows down the evaporation process and dominates the solute-concentration dependence of the droplet evaporation time. The evaporation-induced enhanced solute concentration near the droplet surface, which is accounted for using a two-stage evaporation description, is found to further slow-down the drying process. On the other hand, the presence of solutes is found to produce a lower limit for the droplet size that can be reached by evaporation and, also, to reduce evaporation cooling of the droplet, which tend to decrease the evaporation time. Overall, the first two effects are dominant, meaning that the droplet evaporation time increases in the presence of solutes. Local variation of the water diffusivity inside the droplet near its surface, which is a consequence of the solute-concentration dependence of the diffusion coefficient, does not significantly change the evaporation time. Crust formation on the droplet surface increases the final equilibrium size of the droplet by producing a hollow spherical particle, the outer radius of which is determined as well.

Deep and Machine Learning Using SEM, FTIR, and Texture Analysis to Detect Polysaccharide in Raspberry Powders

In the paper, an attempt was made to use methods of artificial neural networks (ANN) and Fourier transform infrared spectroscopy (FTIR) to identify raspberry powders that are different from each other in terms of the amount and the type of polysaccharide. Spectra in the absorbance function (FTIR) were prepared as well as training sets, taking into account the structure of microparticles acquired from microscopic images with Scanning Electron Microscopy (SEM). In addition to the above, Multi-Layer Perceptron Networks (MLPNs) with a set of texture descriptors (machine learning) and Convolution Neural Network (CNN) with bitmap (deep learning) were devised, which is an innovative attitude to solving this issue. The aim of the paper was to create MLPN and CNN neural models, which are characterized by a high efficiency of classification. It translates into recognizing microparticles (obtaining their homogeneity) of raspberry powders on the basis of the texture of the image pixel.

Pharmaceutical amorphous solid dispersion: A review of manufacturing strategies

Amorphous solid dispersions (ASDs) are popular for enhancing the solubility and bioavailability of poorly water-soluble drugs. Various approaches have been employed to produce ASDs and novel techniques are emerging. This review provides an updated overview of manufacturing techniques for preparing ASDs. As physical stability is a critical quality attribute for ASD, the impact of formulation, equipment, and process variables, together with the downstream processing on physical stability of ASDs have been discussed. Selection strategies are proposed to identify suitable manufacturing methods, which may aid in the development of ASDs with satisfactory physical stability.

Engineering Advances in Spray Drying for Pharmaceuticals

Spray drying is a versatile technology that has been applied widely in the chemical, food, and, most recently, pharmaceutical industries. This review focuses on engineering advances and the most significant applications of spray drying for pharmaceuticals. An in-depth view of the process and its use is provided for amorphous solid dispersions, a major, growing drug-delivery approach. Enhanced understanding of the relationship of spray-drying process parameters to final product quality attributes has made robust product development possible to address a wide range of pharmaceutical problem statements. Formulation and process optimization have leveraged the knowledge gained as the technology has matured, enabling improved process development from early feasibility screening through commercial applications. Spray drying's use for approved small-molecule oral products is highlighted, as are emerging applications specific to delivery of biologics and non-oral delivery of dry powders. Based on the changing landscape of the industry, significant future opportunities exist for pharmaceutical spray drying.

Co-spray dried hydrophobic drug formulations with crystalline lactose for inhalation aerosol delivery

Spray drying is a rapid method for converting a liquid feed into dried particles for inhalation aerosols. Lactose is a major inhalation excipient used in spray-dried (SD) formulations. However, SD powders produced from solutions are usually amorphous hence unstable to moisture. This problem can potentially be minimized by spray drying a suspension (instead of solution) containing crystalline lactose particles and dissolved drugs. In the present study, the suspension formulation containing dissolved budesonide (BUD) or rifampicin (RIF) and suspended lactose crystals in isopropanol alcohol (IPA) were produced. For comparison, powders were also produced from solution formulations containing the same proportions of drug and lactose dissolved in 50:50 IPA/water as controls. These SD powders were stored at 25 °C/60% RH and 40 °C/75% RH for six months. The particulate properties and in vitro dispersion performance were examined at various storage time points. All powders obtained from spray drying of solutions recrystallized after one week of storage at 25 °C/60% RH. In contrast, SD BUD-lactose obtained from suspension did not change until after three-months of storage when the particle size increased gradually with morphology change and yet the crystallinity remained the same as determined by X-ray powder diffraction. For the SD RIF-lactose obtained from suspension, both particulate properties and in vitro powder dispersion performance showed no significant difference before and after storage at both storage conditions. To conclude, this is the first study to show that SD powder formulations obtained from suspensions containing lactose crystals demonstrated superior storage stability performance, which is desirable for inhaled powders.

Airborne virus transmission via respiratory droplets: Effects of droplet evaporation and sedimentation

Airborne transmission is considered as an important route for the spread of infectious diseases, such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and is primarily determined by the droplet sedimentation time, that is, the time droplets spend in air before reaching the ground. Evaporation increases the sedimentation time by reducing the droplet mass. In fact, small droplets can, depending on their solute content, almost completely evaporate during their descent to the ground and remain airborne as so-called droplet nuclei for a long time. Considering that viruses possibly remain infectious in aerosols for hours, droplet nuclei formation can substantially increase the infectious viral air load. Accordingly, the physical-chemical factors that control droplet evaporation and sedimentation times and play important roles in determining the infection risk from airborne respiratory droplets are reviewed in this article.