The History of Therapeutic Aerosols: A Chronological Review

Scale-Up and Postapproval Changes in Orally Inhaled Drug Products: Scientific and Regulatory Considerations

Approved drug products may be subject to change(s) for a variety of reasons. The changes may include, but are not limited to, increase in batch size, alteration of the drug product constituent(s), improvement in the manufacturing process, and shift in manufacturing sites. The extent of pharmaceutical testing and the regulatory pathway for timely implementation of any change in the approved product and/or process depends upon the nature and extent of change. The U.S. Food and Drug Administration (FDA) has published guidelines that outline its expectations for the Scale-Up and Postapproval Changes (SUPAC) in the solid oral immediate and modified release (MR) products, and semisolid formulations. However, to date, no such guidelines have been issued to address SUPAC in the orally inhaled drug products (OIDPs), and this article represents a seminal contribution in this direction. It is hoped that it will inspire contributions from the relevant multidisciplinary experts from the pharmaceutical industry and the agency in accomplishing formal regulatory guidelines relevant to the OIDP SUPAC. The OIDPs are complex drug-device combination products. Therefore, a conceptualization of SUPAC guidelines for these products warrants consideration of contributions of effect of change(s) in individual components (drug substance, formulation, device) as well as a compound effect that a single or multiple changes may have on product performance, and its safety and efficacy. This article provides a discussion of scientific aspects and regulatory bases relevant to the development of SUPAC for OIDPs, and it attempts to outline considerations that may be applicable in addressing issues related to the OIDP SUPAC in the context of human drugs. The authors' statements should not be viewed as recommendations from any regulatory agency, as the applicable guidelines would be determined on case-by-case evaluation by the relevant authorities.

Different Carriers for Use in Dry Powder Inhalers: Characteristics of Their Particles

In contemporary times, there has been a rise in the utilization of dry powder inhalers (DPIs) in the management of pulmonary and systemic diseases. These devices underwent a swift advancement in terms of both the equipment utilized and the formulation process. In this review, the carrier physicochemical characteristics that influence DPI performance are discussed, focusing its shape, morphology, size distribution, texture, aerodynamic diameter, density, moisture, adhesive and detachment forces between particles, fine carrier particles, and dry powder aerosolization. To promote the deposition of the active principal ingredient deep within the pulmonary system, advancements have been made in enhancing these factors and surface properties through the application of novel technologies that encompass particle engineering. So far, the most used carrier is lactose showing some advantages and disadvantages, but other substances and systems are being studied with the intention of replacing it. The final objective of this review is to analyze the physicochemical and mechanical characteristics of the different carriers or new delivery systems used in DPI formulations, whether already on the market or still under investigation.

An approach to reduce inhaler errors using Donabedian's triad

Inhaler errors inversely affect the outcome of respiratory diseases. Inhaler devices, such as the metered-dose inhalers (MDI) and dry powder inhalers (DPI), are commonly used in treating respiratory diseases like asthma and chronic obstructive pulmonary disease (COPD), and incorrect use of these devices can result in suboptimal treatment outcomes, increased probabilities of hospitalizations or admissions, and poorer quality of life. Patient related factors to inhaler errors include age, cognitive and physical abilities, education, language barriers, and preferences. Device-related factors such as inhaler design and operational complexity can also lead to errors. Finally, factors related to healthcare professionals (HCP) such as competency, level of knowledge in disease and inhaler device and availability to educate patients, can play a role in inhaler error. Quality management is a potential solution to this problem. Quality improvement strategies towards addressing inhaler misuse can increase patient satisfaction and improve patient outcomes. Donabedian's triad, which includes structure, process, and outcome can be utilized in developing a framework for reducing inhaler errors. Institutional solutions are more towards the structural and process changes in the triad, such as HCP training, checklists on training efficacy, provision of action plans, and availability of staff to educate and train patients. Patient-centered solutions focus more on process and outcome domains, such as improvement in lung functions, patient education, re-assessment and re-education of inhaler techniques, and adherence to treatment regimen. By focusing on structural and process domains, the quality of care can be enhanced, resulting in improved outcomes.

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.

Administration of airborne pathogens in non-human primates

PURPOSE

Airborne pathogen scan penetrate in human respiratory tract and can cause illness. The use of animal models to predict aerosol deposition and study respiratory disease pathophysiology is therefore important for research and a prerequisite to test and study the mechanism of action of treatment. NHPs are relevant animal species for inhalation studies because of their similarities with humans in terms of anatomical structure, respiratory parameters and immune system.

MATERIALS AND METHODS

The aim of this review is to provide an overview of the state of the art of pathogen aerosol studies performed in non-human primates (NHPs). Herein, we present and discuss the deposition of aerosolized bacteria and viruses. In this review, we present important advantages of using NHPs as model for inhalation studies.

RESULTS

We demonstrate that deposition in the respiratory tract is not only a function of aerosol size but also the technique of administration influences the biological activity and site of aerosol deposition. Finally, we observe an influence of a region of pathogen deposition in the respiratory tract on the development of the pathophysiological effect in NHPs.

CONCLUSION

The wide range of methods used for the delivery of pathogento NHP respiratory airways is associated with varying doses and deposition profiles in the airways.

Gas Delivery Relevant to Human Health using Porous Materials

Gases are essential for various applications relevant to human health, including in medicine, biomedical imaging, and pharmaceutical synthesis. However, gases are significantly more challenging to safely handle than liquids and solids. Herein, we review the use of porous materials, such as metal-organic frameworks (MOFs), zeolites, and silicas, to adsorb medicinally relevant gases and facilitate their handling as solids. Specific topics include the use of MOFs and zeolites to deliver H2S for therapeutic applications, 129Xe for magnetic resonance imaging, O2 for the treatment of cancer and hypoxia, and various gases for use in organic synthesis. This Perspective aims to bring together the organic, inorganic, medicinal, and materials chemistry communities to inspire the design of next-generation porous materials for the storage and delivery of medicinally relevant gases.

Understanding the role of swirling flow in dry powder inhalers: Implications for design considerations and pulmonary delivery

Dry powder inhalers (DPIs) are widely employed to treat respiratory diseases, offering numerous advantages such as high dose capacity and stable formulations. However, they usually face challenges in achieving sufficient pulmonary drug delivery and minimizing excessive oropharyngeal deposition. This review provides a new viewpoint to address these challenges by focusing on the role of swirling flow, a crucial yet under-researched aspect that induces strong turbulence. In the review, we comprehensively discuss both key classic designs (tangential inlet, swirling chamber, grid mesh, and mouthpiece) and innovative designs in inhalers, exploring how the induced swirling flow initiates powder dispersion and promotes delivery efficiency. Valuable design considerations to effectively coordinate inhalers with formulations and patients are also provided. It is highlighted that the delicate manipulation of swirling flow is essential to maximize benefits. By emphasizing the role of swirling flow and its potential application, this review offers promising insights for advancing DPI technology and optimizing therapeutic outcomes in inhaled therapy.

Inhalational Drug Devices: Revisiting the Linchpin of Asthma Management

Asthma remains a prevalent condition among all age groups globally. First-line treatment requires the delivery of medications into the distal respiratory tract via inhalers. Using appropriate inhaler techniques is a significant challenge in achieving disease control. A variety of inhalers are available for treating asthma, and selecting the appropriate inhaler type for any given patient is crucial to achieving and maintaining symptomatic control. This review will discuss the anatomy and physiology behind drug delivery via inhalers, the types of inhalers currently available for use, nebulizers, and future directions in the delivery of inhaled medications for asthma.

Quality by Design in Pulmonary Drug Delivery: A Review on Dry Powder Inhaler Development, Nanotherapy Approaches, and Regulatory Considerations

Dry powder inhalers (DPIs) are state-of-the-art pulmonary drug delivery systems. This article explores the transformative impact of nanotechnology on DPIs, emphasizing the Quality Target Product Profile (QTPP) with a focus on aerodynamic performance and particle characteristics. It navigates global regulatory frameworks, underscoring the need for safety and efficacy standards. Additionally, it highlights the emerging field of nanoparticulate dry powder inhalers, showcasing their potential to enhance targeted drug delivery in respiratory medicine. This concise overview is a valuable resource for researchers, physicians, and pharmaceutical developers, providing insights into the development and commercialization of advanced inhalation systems.

Nanomedicines via the pulmonary route: a promising strategy to reach the target?

Over the past decades, research on nanomedicines as innovative tools in combating complex pathologies has increased tenfold, spanning fields from infectiology and ophthalmology to oncology. This process has further accelerated since the introduction of SARS-CoV-2 vaccines. When it comes to human health, nano-objects are designed to protect, transport, and improve the solubility of compounds to allow the delivery of active ingredients on their targets. Nanomedicines can be administered by different routes, such as intravenous, oral, intramuscular, or pulmonary routes. In the latter route, nanomedicines can be aerosolized or nebulized to reach the deep lung. This review summarizes existing nanomedicines proposed for inhalation administration, from their synthesis to their potential clinical use. It also outlines the respiratory organs, their structure, and particularities, with a specific emphasis on how these factors impact the administration of nanomedicines. Furthermore, the review addresses the organs accessible through pulmonary administration, along with various pathologies such as infections, genetic diseases, or cancer that can be addressed through inhaled nanotherapeutics. Finally, it examines the existing devices suitable for the aerosolization of nanomedicines and the range of nanomedicines in clinical development.

Real-World Use of Inhaled COPD Medications: the Good, the Bad, the Ugly

Patients with chronic obstructive pulmonary disease (COPD) rely primarily on inhaled medications to control and treat symptoms. Although the medications delivered by inhaler devices are often quite efficacious when delivered to the lung, the real-world effectiveness of these inhaler devices often falls short. Barriers to effective inhaler use include inhaler misuse and cost-related nonadherence. Inhaler misuse can be reduced with appropriate education which leads to improved outcomes. Education can be provided in multiple settings by a wide array of clinicians and clinical team members including pharmacists, respiratory therapists, nurses, physicians, advanced practice nurses, physician assistants, and community health workers, among others. However, despite decades of research and existing effective strategies across settings and types of educators, overall not much progress has been made with respect to effective inhaler technique among populations of patients with COPD in nearly half a century. Similarly, cost-related nonadherence is a long-standing and critical barrier to effective control of COPD, with limited improvements, especially until very recently. This perspective reviews the current promising directions for inhaler-based therapies, ongoing challenges, and critical issues requiring urgent attention.

Recent Developments in Aerosol Pulmonary Drug Delivery: New Technologies, New Cargos, and New Targets

There is nothing like a global pandemic to motivate the need for improved respiratory treatments and mucosal vaccines. Stimulated by the COVID-19 pandemic, pulmonary aerosol drug delivery has seen a flourish of activity, building on the prior decades of innovation in particle engineering, inhaler device technologies, and clinical understanding. As such, the field has expanded into new directions and is working toward the efficient delivery of increasingly complex cargos to address a wider range of respiratory diseases. This review seeks to highlight recent innovations in approaches to personalize inhalation drug delivery, deliver complex cargos, and diversify the targets treated and prevented through pulmonary drug delivery. We aim to inform readers of the emerging efforts within the field and predict where future breakthroughs are expected to impact the treatment of respiratory diseases.

A Review on Micro and Nanoengineering in Powder-Based Pulmonary Drug Delivery

Pulmonary delivery of drugs has emerged as a promising approach for the treatment of both lung and systemic diseases. Compared to other drug delivery routes, inhalation offers numerous advantages including high targeting, fewer side effects, and a huge surface area for drug absorption. However, the deposition of drugs in the lungs can be limited by lung defence mechanisms such as mucociliary and macrophages' clearance. Among the delivery devices, dry powder inhalers represent the optimal choice due to their stability, ease of use, and absence of propellants. In the last decades, several bottom-up techniques have emerged over traditional milling to produce inhalable powders. Among these techniques, the most employed ones are spray drying, supercritical fluid technology, spray freeze-drying, and thin film freezing. Inhalable dry powders can be constituted by micronized drugs attached to a coarse carrier (e.g., lactose) or drugs embedded into a micro- or nanoparticle. Particulate-based formulations are commonly composed of polymeric micro- and nanoparticles, liposomes, solid lipid nanoparticles, dendrimers, nanocrystals, extracellular vesicles, and inorganic nanoparticles. Moreover, engineered formulations including large porous particles, swellable microparticles, nano-in-microparticles, and effervescent nanoparticles have been developed. Particle engineering has also a crucial role in tuning the physical-chemical properties of both carrier-based and carrier-free inhalable powders. This approach can increase powder flowability, deposition, and targeting by customising particle surface features.

Preventing aspiration incidents: redesigning inhalers for enhanced safety: A case study of coin aspiration

The conventional metered dose inhaler (MDI) has long served as a cornerstone in the management of asthma and chronic obstructive pulmonary disease (COPD), affecting millions annually. Despite its advantages, a persistent challenge is seen in the form of patient education and the unchanged design of these inhalers since their inception in 1956. This lack of progress in MDI design has inadvertently contributed to incidences of foreign body inhalation. In this case presentation we report a 50-year-old male with a past medical history of asthma, who faced an incident of foreign body inhalation with use of his inhaler. The patient aspirated a dime when he administered his inhaler, as it had become lodged in the device's mouthpiece, which was uncapped. This case, like many others, demonstrates the need for innovative changes in MDI inhaler design. While numerous articles or cases concentrate on foreign body removal, the primary objective of this case report is to investigate preventative measures and solutions aimed at averting incidents of inhalation.

Humidification during Invasive and Non-Invasive Ventilation: A Starting Tool Kit for Correct Setting

The humidification process of medical gases plays a crucial role in both invasive and non-invasive ventilation, aiming to mitigate the complications arising from bronchial dryness. While passive humidification systems (HME) and active humidification systems are prevalent in routine clinical practice, there is a pressing need for further evaluation of their significance. Additionally, there is often an incomplete understanding of the operational mechanisms of these devices. The current review explores the historical evolution of gas conditioning in clinical practice, from early prototypes to contemporary active and passive humidification systems. It also discusses the physiological principles underlying humidity regulation and provides practical guidance for optimizing humidification parameters in both invasive and non-invasive ventilation modalities. The aim of this review is to elucidate the intricate interplay between temperature, humidity, and patient comfort, emphasizing the importance of individualized approaches to gas conditioning.

On the Feasibility of Rugose Lipid Microparticles in Pressurized Metered Dose Inhalers with Established and New Propellants

Pressurized metered dose inhalers (pMDIs) require optimized formulations to provide stable, consistent lung delivery. This study investigates the feasibility of novel rugose lipid particles (RLPs) as potential drug carriers in pMDI formulations. The physical stability of RLPs was assessed in three different propellants: the established HFA-134a and HFA-227ea and the new low global-warming-potential (GWP) propellant HFO-1234ze. A feedstock containing DSPC and calcium chloride was prepared without pore forming agent to spray dry two RLP batches at inlet temperatures of 55 °C (RLP55) and 75 °C (RLP75). RLPs performance in pMDI formulations was compared to two reference samples that exhibit significantly different performance when suspended in propellants: well-established engineered porous particles and particles containing 80% trehalose and 20% leucine (80T20L). An accelerated stability study at 40 °C and relative humidity of 7% ± 5% was conducted over 3 months. At different time points, a shadowgraphic imaging technique was used to evaluate the colloidal stability of particles in pMDIs. Field emission electron microscopy with energy dispersive X-ray spectroscopy was used to evaluate the morphology and elemental composition of particles extracted from the pMDIs. After 2 weeks, all 80T20L formulations rapidly aggregated upon agitation and exhibited significantly inferior colloidal stability compared to the other samples. In comparison, both the RLP55 and RLP75 formulations, regardless of the propellant used, retained their rugose structure and demonstrated excellent suspension stability comparable with the engineered porous particles. The studied RLPs demonstrate great potential for use in pMDI formulations with HFA propellants and the next-generation low-GWP propellant HFO-1234ze.

Designing inhaled small molecule drugs for severe respiratory diseases: an overview of the challenges and opportunities

INTRODUCTION

Inhaled drugs offer advantages for the treatment of respiratory diseases over oral drugs by delivering the drug directly to the lung, thus improving the therapeutic index. There is an unmet medical need for novel therapies for lung diseases, exacerbated by a multitude of challenges for the design of inhaled small molecule drugs.

AREAS COVERED

The authors review the challenges and opportunities for the design of inhaled drugs for respiratory diseases with a focus on new target discovery, medicinal chemistry, and pharmacokinetic, pharmacodynamic, and toxicological evaluation of drug candidates.

EXPERT OPINION

Inhaled drug discovery is facing multiple unique challenges. Novel biological targets are scarce, as is the guidance for medicinal chemistry teams to design compounds with inhalation-compatible features. It is exceedingly difficult to establish a PK/PD relationship given the complexity of pulmonary PK and the impact of physical properties of the drug substance on PK. PK, PD and toxicology studies are technically challenging and require large amounts of drug substance. Despite the current challenges, the authors foresee that the design of inhaled drugs will be facilitated in the future by our increasing understanding of pathobiology, emerging medicinal chemistry guidelines, advances in drug formulation, PBPK models, and in vitro toxicology assays.

Nebuliser therapy in critical care: The past, present and future

Nebulisers are devices that reduce a body of liquid into a fine aerosol suitable for inhalation. Utilising the efficiency of pulmonary drug absorption, they offer a safe and powerful modality for local and systemic drug delivery in the treatment of critical illness. In comparison to conventional jet (JN) and ultrasonic nebulisers (USN), the advent of vibrating mesh nebulisers (VMN) has significantly improved the therapeutic potential of modern devices. This review article aims to summarise the history and evolution of nebulisers from first inception through to the modern vibrating mesh technology. It provides an overview on the basic science of nebulisation and pulmonary drug delivery, and the current use of nebulised therapies in critical care.

Mapping the evolution of inhaled drug delivery research: Trends, collaborations, and emerging frontiers

Inhaled drug delivery is a unique administration route known for its ability to directly target pulmonary or brain regions, facilitating rapid onset and circumventing the hepatic first-pass effect. To characterize current global trends and provide a visual overview of the latest trends in inhaled drug delivery research, bibliometric analysis of data acquired from the Web of Science Core Collection database was performed via VOSviewer and CiteSpace. Inhaled drug delivery can not only be utilized in respiratory diseases but also has potential in other types of diseases for both fundamental and clinical applications. Overall, we provide an overview of present trends, collaborations, and newly discovered frontiers of inhaled drug delivery.

A perspective current and past modes of inhalation therapy

Inhalation is the preferred route of delivery for anti-asthma and chronic obstructive pulmonary disease (COPD) drugs. The use of this route has demonstrated efficacy in these and other conditions, it offers rapid onset of action, and is associated with minimal systemic exposure, thereby reducing the risk of adverse effects. Therefore, the current brief covers an interesting collection of inhaler action modes, shedding light on their molecular mechanisms and clinical applications for anti-asthma, COPD and antibacterial inhalation therapy. Hence, not only enriches our understanding of inhalation therapy molecular intricacies but also provides a comprehensive overview of the evolving landscape in clinical and antibacterial inhalation therapy. In doing so, it underscores the pivotal role of microbiology and biotechnology in advancing therapeutic approaches that harness the power of inhalation.

Towards More Precise Targeting of Inhaled Aerosols to Different Areas of the Respiratory System

Pharmaceutical aerosols play a key role in the treatment of lung disorders, but also systemic diseases, due to their ability to target specific areas of the respiratory system (RS). This article focuses on identifying and clarifying the influence of various factors involved in the generation of aerosol micro- and nanoparticles on their regional distribution and deposition in the RS. Attention is given to the importance of process parameters during the aerosolization of liquids or powders and the role of aerosol flow dynamics in the RS. The interaction of deposited particles with the fluid environment of the lung is also pointed out as an important step in the mass transfer of the drug to the RS surface. The analysis presented highlights the technical aspects of preparing the precursors to ensure that the properties of the aerosol are suitable for a given therapeutic target. Through an analysis of existing technical limitations, selected strategies aimed at enhancing the effectiveness of targeted aerosol delivery to the RS have been identified and presented. These strategies also include the use of smart inhaling devices and systems with built-in AI algorithms.

Long-acting inhaled medicines: Present and future

Inhaled medicines continue to be an essential part of treatment for respiratory diseases such as asthma, chronic obstructive pulmonary disease, and cystic fibrosis. In addition, inhalation technology, which is an active area of research and innovation to deliver medications via the lung to the bloodstream, offers potential advantages such as rapid onset of action, enhanced bioavailability, and reduced side effects for local treatments. Certain inhaled macromolecules and particles can also end up in different organs via lymphatic transport from the respiratory epithelium. While the majority of research on inhaled medicines is focused on the delivery technology, particle engineering, combination therapies, innovations in inhaler devices, and digital health technologies, researchers are also exploring new pharmaceutical technologies and strategies to prolong the duration of action of inhaled drugs. This is because, in contrast to most inhaled medicines that exert a rapid onset and short duration of action, long-acting inhaled medicines (LAIM) improve not only the patient compliance by reducing the dosing frequency, but also the effectiveness and convenience of inhaled therapies to better manage patients' conditions. This paper reviews the advances in LAIM, the pharmaceutical technologies and strategies for developing LAIM, and emerging new inhaled modalities that possess a long-acting nature and potential in the treatment and prevention of various diseases. The challenges in the development of the future LAIM are also discussed where active research and innovations are taking place.

Asthma and COPD: A Focus on β-Agonists - Past, Present and Future

Asthma has been recognised as a respiratory disorder for millennia and the focus of targeted drug development for the last 120 years. Asthma is one of the most common chronic non-communicable diseases worldwide. Chronic obstructive pulmonary disease (COPD), a leading cause of morbidity and mortality worldwide, is caused by exposure to tobacco smoke and other noxious particles and exerts a substantial economic and social burden. This chapter reviews the development of the treatments of asthma and COPD particularly focussing on the β-agonists, from the isolation of adrenaline, through the development of generations of short- and long-acting β-agonists. It reviews asthma death epidemics, considers the intrinsic efficacy of clinical compounds, and charts the improvement in selectivity and duration of action that has led to our current medications. Important β2-agonist compounds no longer used are considered, including some with additional properties, and how the different pharmacological properties of current β2-agonists underpin their different places in treatment guidelines. Finally, it concludes with a look forward to future developments that could improve the β-agonists still further, including extending their availability to areas of the world with less readily accessible healthcare.

Inhalation Dosage Forms: A Focus on Dry Powder Inhalers and Their Advancements

In this review, an extensive analysis of dry powder inhalers (DPIs) is offered, focusing on their characteristics, formulation, stability, and manufacturing. The advantages of pulmonary delivery were investigated, as well as the significance of the particle size in drug deposition. The preparation of DPI formulations was also comprehensively explored, including physico-chemical characterization of powders, powder processing techniques, and formulation considerations. In addition to manufacturing procedures, testing methods were also discussed, providing insights into the development and evaluation of DPI formulations. This review also explores the design basics and critical attributes specific to DPIs, highlighting the significance of their optimization to achieve an effective inhalation therapy. Additionally, the morphology and stability of 3 DPI capsules (Spiriva, Braltus, and Onbrez) were investigated, offering valuable insights into the properties of these formulations. Altogether, these findings contribute to a deeper understanding of DPIs and their development, performance, and optimization of inhalation dosage forms.

Acute, repeated inhalation toxicity, respiratory system irritation, and mutagenicity studies of 1,1,2,2-tetrafluoroethane (HFC-134) as the impurity in the pharmaceutical propellant 1,1,1,2-tetrafluoroethane (HFA-134a)

HFC-134 is the main impurity of HFA-134a. In order to verify the rationality of HFC-134 limits in HFA-134a and ensure the safety of HFA-134a as propellant in pharmaceutical metered-dose inhalers, acute inhalation toxicity, seven-day repeat dose inhalation irritation study, 21-day repeat dose inhalation toxicity study and reverse mutation assay of HFC-134 were tested to evaluate its inhalation safety. In acute inhalation studies, Sprague-Dawley rats were exposed nose-only to HFC-134 at levels of 100 000, 200 000, 400 000, 600 000, and 800 000 ppm for 4 h. Based on the mortality incidence, the calculated four-hour LC50 value for HFC-134 is 532 069 ppm for males and 502 058 ppm for females and acute inhalation toxicity is manifested as the lung lobes turn dark red. Exposures to 836 ± 67 ppm for 4 hours/day 7 days/week continuously did not induce local irritation of the respiratory system in Sprague-Dawley rats. Sprague-Dawley rats were exposed nose-only to HFC-134 at levels of 0 (control), 203 929 ppm and 394 871 ppm 2 h/day for 21 consecutive days, no significant treatment-related adverse effects was noted. Results from Ames studies demonstrated that HFC-134 was not mutagenic. Although HFC-134 has a very low acute inhalation toxicity, considering that its acute inhalation toxicity is higher than that of HFA-134a, and due to the high frequency of use of MDI by asthma patients, acceptance criteria of HFC-134 as the impurity in aerosol propellant HFA-134a should be lower than 8-h TWA WEEL value of 1000 ppm to ensure the safety of the MDI.

A narrative review on the Synchrobreathe™: A novel breath-actuated pressurised metered-dose inhaler for the treatment of obstructive airway diseases

Pressurised metered-dose inhalers (pMDIs) and dry powder inhalers (DPIs), are widely used to deliver drugs for the treatment of asthma and chronic obstructive pulmonary disease (COPD). Incorrect use of inhalers is one of the main obstacles to achieving better clinical control. Indeed, with pMDIs, patients fail to synchronise actuation with inhalation due to a lack of coordination and with DPIs insufficient inspiratory effort compromises drug deposition in lungs. More than 50% of patients desire to switch their pMDIs and DPIs for a better device. This led to the development of pressurised breath-actuated inhalers (BAIs) with the aim of combining the beneficial features of pMDIs and DPIs and mitigating their problems. BAIs, e.g., Synchrobreathe™, are designed such that they are activated by a low inhalation effort and mechanically actuate the dose in synchrony to inspiration, thereby resolving the need to coordinate actuation with inspiration. BAIs have advantages, including ease of use, high lung deposition of medication, and greater patient preference. We discussed the design features, operating procedure, and clinical evidence of the Synchrobreathe™ device (Cipla Ltd, India), a BAI available with a wide range of drug combinations. Studies have shown that a higher number of patients (68.19%) used the Synchrobreathe™ without any error than the pMDI (56.21%), and that the vast majority of them (92%) found it easy to understand and use. The Synchrobreathe™ is an innovative, easy-to-use inhaler that may overcome many limitations associated with pMDIs and DPIs, thus potentially improving management of obstructive airway diseases and patients' quality of life.

Treatable traits, combination inhaler therapy and the future of asthma management

The landscape of asthma has considerably changed in the last decade. Effective medications and inhaler devices have been developed and integrated into the asthma pharmacopoeia, but unfortunately, the proportion of uncontrolled patients remains unacceptably high. This is now recognized to be mainly due to the inappropriate use of medications or inhaler devices, heterogeneity of the disease or other factors contributing to the disease. Currently, inhaled corticosteroids (ICS), with or without long-acting beta agonists (LABA), are the cornerstone of asthma management, and recently international guidelines recognized the importance of combination inhaler therapy (ICS/LABA) even in mild asthma. In future, ultra-long-acting personalized medications and smart inhalers will complement combination inhaler therapy in order to effectively addresses issues such as adherence, inhaler technique and polypharmacy (both of drugs and devices). Asthma is now acknowledged as a multifaceted cluster of disorders and the treatment model has evolved from one-size-fits-all to precision medicine approaches such as treatable traits (TTs, defined as measurable and treatable clinically important factors) which encourages the quality use of medications and identification and management of all underlying behavioural and biological treatable risk factors. TT requires research and validation in a clinical context and the implementation strategies and efficacy in various settings (primary/secondary/tertiary care, low-middle income countries) and populations (mild/moderate/severe asthma) are currently evolving. Combination inhaler therapy and the TTs approach are complementary treatment approaches. This review examines the current status of personalized medicine and combination inhaler therapy, and describes futuristic views for these two strategies.

Drug combinations for inhalation: Current products and future development addressing disease control and patient compliance

Pulmonary delivery is an alternative route of administration with numerous advantages over conventional routes of administration. It provides low enzymatic exposure, fewer systemic side effects, no first-pass metabolism, and concentrated drug amounts at the site of the disease, making it an ideal route for the treatment of pulmonary diseases. Owing to the thin alveolar-capillary barrier, and large surface area that facilitates rapid absorption to the bloodstream in the lung, systemic delivery can be achieved as well. Administration of multiple drugs at one time became urgent to control chronic pulmonary diseases such as asthma and COPD, thus, development of drug combinations was proposed. Administration of medications with variable dosages from different inhalers leads to overburdening the patient and may cause low therapeutic intervention. Therefore, products that contain combined drugs to be delivered via a single inhaler have been developed to improve patient compliance, reduce different dose regimens, achieve higher disease control, and boost therapeutic effectiveness in some cases. This comprehensive review aimed to highlight the growth of drug combinations by inhalation over time, obstacles and challenges, and the possible progress to broaden the current options or to cover new indications in the future. Moreover, various pharmaceutical technologies in terms of formulation and device in correlation with inhaled combinations were discussed in this review. Hence, inhaled combination therapy is driven by the need to maintain and improve the quality of life for patients with chronic respiratory diseases; promoting drug combinations by inhalation to a higher level is a necessity.

Aerosol pulmonary immune engineering

Aerosolization of immunotherapies poses incredible potential for manipulating the local mucosal-specific microenvironment, engaging specialized pulmonary cellular defenders, and accessing mucosal associated lymphoid tissue to redirect systemic adaptive and memory responses. In this review, we breakdown key inhalable immunoengineering strategies for chronic, genetic, and infection-based inflammatory pulmonary disorders, encompassing the historic use of immunomodulatory agents, the transition to biological inspired or derived treatments, and novel approaches of complexing these materials into drug delivery vehicles for enhanced release outcomes. Alongside a brief description of key immune targets, fundamentals of aerosol drug delivery, and preclinical pulmonary models for immune response, we survey recent advances of inhaled immunotherapy platforms, ranging from small molecules and biologics to particulates and cell therapies, as well as prophylactic vaccines. In each section, we address the formulation design constraints for aerosol delivery as well as advantages for each platform in driving desirable immune modifications. Finally, prospects of clinical translation and outlook for inhaled immune engineering are discussed.

Systemic Protein Delivery via Inhalable Liposomes: Formulation and Pharmacokinetics

The enormous and thin alveolar epithelium is an attractive site for systemic protein delivery. Considering the excellent biocompatibility of phospholipids with endogenous pulmonary surfactant, we engineered dimyristoylphosphatidylcholine (DMPC)-based liposomes for pulmonary administration, using Cy5.5-labeled bovine serum albumin (BSA-Cy5.5) as a model protein payload. The level of cholesterol (Chol) and surface modification with PEG in inhalable liposomes were optimized iteratively based on the encapsulation efficiency, the release kinetics in the simulated lung fluid, and the uptake in murine RAW 264.7 macrophages. The plasma pharmacokinetics of BSA-Cy5.5-encapsulated liposomes with the composition of DMPC/Chol/PEG at 85:10:5 (molar ratio) was studied in mice following intratracheal aerosolization, in comparison with that of free BSA-Cy5.5 solution. The biodisposition of BSA-Cy5.5 was continuously monitored using whole-body near-infrared (NIR) fluorescence imaging for 10 days. We found that the systemic bioavailability of BSA-Cy5.5 from inhaled liposomes was 22%, which was notably higher than that of inhaled free BSA-Cy5.5. The mean residence time of BSA-Cy5.5 was markedly prolonged in mice administered intratracheally with liposomal BSA-Cy5.5, which is in agreement with the NIR imaging results. Our work demonstrates the great promise of inhalable DMPC-based liposomes to achieve non-invasive systemic protein delivery.

Metered dose inhalers in the transition to low GWP propellants: what we know and what is missing to make it happen

INTRODUCTION

The urgency to replace the propellants currently in use with the new sustainable ones has given rise to the need for investigation and reformulation of pMDIs.

AREAS COVERED

The reformulation requires in-depth knowledge of the physico-chemical characteristics of the new propellants, which impact the atomization capacity and the plume geometry. Among the investigated propellants, HFA 152a, due to its lower vapor pressure and higher surface tension compared to HFA 134a, deliver larger particles and has a higher solvent capacity toward lipophilic drugs. On the other hand, HFO 1234ze has properties more similar to HFA 134a, but showed lower reproducibility of the generated spray, indicating a possible high susceptibility to variation in the consistency of the dose delivered. In addition, the device components currently in use are compatible with the new propellants. This allowed promising preliminary results in the re-formulation of pMDIs by academia and pharma companies. However, there is little information about the clinical studies required to allow the marketing of these new products.

EXPERT OPINION

Overall, studies conducted so far show that the transition is technically possible, and the main obstacle will be represented by the investment required to put the product on the market.

Inhalation delivery of nucleic acid gene therapies in preclinical drug development

INTRODUCTION

Inhaled gene therapy programs targeting diseases of the lung have seen increasing interest in recent years, though as of yet no product has successfully entered the market. Preclinical research to support such programs is critically important in maximizing the chances of developing successful candidates.

AREAS COVERED

Aspects of inhalation delivery of gene therapies are reviewed, with a focus on preclinical research in animal models. Various barriers to inhalation delivery of gene therapies are discussed, including aerosolization stresses, aerosol behavior in the respiratory tract, and disposition processes post-deposition. Important aspects of animal models are considered, including determinations of biologically relevant determinations of dose and issues related to translatability.

EXPERT OPINION

Development of clinically-efficacious inhaled gene therapies has proven difficult owing to numerous challenges. Fit-for-purpose experimental and analytical methods are necessary for determinations of biologically relevant doses in preclinical animal models. Further developments in disease-specific animal models may aid in improving the translatability of results in future work, and we expect to see accelerated interests in inhalation gene therapies for various diseases. Sponsors, researchers, and regulators are encouraged to engage in early and frequent discussion regarding candidate therapies, and additional dissemination of preclinical methodologies would be of immense value in avoiding common pitfalls.

Inhaled drug delivery for the targeted treatment of asthma

Asthma is a chronic lung disease affecting millions worldwide. While classically acknowledged to result from allergen-driven type 2 inflammatory responses leading to IgE and cytokine production and the influx of immune cells such as mast cells and eosinophils, the wide range in asthmatic pathobiological subtypes lead to highly variable responses to anti-inflammatory therapies. Thus, there is a need to develop patient-specific therapies capable of addressing the full spectrum of asthmatic lung disease. Moreover, delivery of targeted treatments for asthma directly to the lung may help to maximize therapeutic benefit, but challenges remain in design of effective formulations for the inhaled route. In this review, we discuss the current understanding of asthmatic disease progression as well as genetic and epigenetic disease modifiers associated with asthma severity and exacerbation of disease. We also overview the limitations of clinically available treatments for asthma and discuss pre-clinical models of asthma used to evaluate new therapies. Based on the shortcomings of existing treatments, we highlight recent advances and new approaches to treat asthma via inhalation for monoclonal antibody delivery, mucolytic therapy to target airway mucus hypersecretion and gene therapies to address underlying drivers of disease. Finally, we conclude with discussion on the prospects for an inhaled vaccine to prevent asthma.

Lessons from the history of inorganic nanoparticles for inhalable diagnostics and therapeutics

The respiratory tract is one of the most accessible ones to exogenous nanoparticles, yet drug delivery by their means to it is made extraordinarily challenging because of the plexus of aerodynamic, hemodynamic and biomolecular factors at cellular and extracellular levels that synergistically define the safety and efficacy of this process. Here, the use of inorganic nanoparticles (INPs) for inhalable diagnostics and therapies of the lung is viewed through the prism of the history of studies on the interaction of INPs with the lower respiratory tract. The most conceptually and methodologically innovative and illuminative studies are referred to in the chronological order, as they were reported in the literature, and the trends in the progress of understanding this interaction of immense therapeutic and toxicological significance are being deduced from it. The most outstanding actual trends delineated include the diminishment of toxicity via surface functionalization, cell targeting, tagging and tracking via controlled binding and uptake, hybrid INP treatments, magnetic guidance, combined drug and gene delivery, use as adjuvants in inhalable vaccines, and other. Many of the understudied research directions, which have been accomplished by the nanostructured organic polymers in the pulmonary niche, are discussed. The progress in the use of INPs as inhalable diagnostics or therapeutics has been hampered by their well-recognized inflammatory potential and toxicity in the respiratory tract. However, the annual numbers of methodologically innovative studies have been on the rise throughout the past two decades, suggesting that this is a prolific direction of research, its comparatively poor commercial takings notwithstanding. Still, the lack of consensus on the effects of many INP compositions at low but therapeutically effective doses, the plethora of contradictory reports on ostensibly identical chemical compositions and NP properties, and the many cases of antagonism in combinatorial NP treatments imply that the rational design of inhalable medical devices based on INPs must rely on qualitative principles for the most part and embrace a partially stochastic approach as well. At the same time, the fact that the most studied INPs for pulmonary applications have been those with some of the thickest records of pulmonary toxicity, e.g., carbon, silver, gold, silica and iron oxide, is a silent call for the expansion of the search for new inorganic compositions for use in inhalable therapies to new territories.

The Changing Asthma Management Landscape and Need for Appropriate SABA Prescription

Short-acting β2 agonists (SABAs) have been a mainstay of asthma treatment since the 1950s, and have been mainly recommended as-needed for symptom relief alongside daily inhaled corticosteroid (ICS)-based maintenance treatment for the past 30 years. However, patient adherence to regular ICS-based anti-inflammatory maintenance therapy is frequently poor, leading to SABA overuse for symptom relief and associated poor outcomes. At present, there is a lack of consensus between treatment guidelines on how SABA should be used, and as-needed ICS-formoterol is suggested by some as an alternative reliever therapy. Here, we examine the pharmacology and current use of inhaled SABAs, identify that regular dosing of ICS can encourage appropriate SABA use, and appraise the evidence used to support the changing reliever treatment recommendations. We conclude that SABA continues to play an important role in the asthma management landscape, and give our views on how it should be used in patients with mild-moderate asthma, to complement regular ICS-based maintenance treatment.

A four-part guide to lung immunology: Invasion, inflammation, immunity, and intervention

Lungs are important respiratory organs primarily involved in gas exchange. Lungs interact directly with the environment and their primary function is affected by several inflammatory responses caused by allergens, inflammatory mediators, and pathogens, eventually leading to disease. The immune architecture of the lung consists of an extensive network of innate immune cells, which induce adaptive immune responses based on the nature of the pathogen(s). The balance of immune responses is critical for maintaining immune homeostasis in the lung. Infection by pathogens and physical or genetic dysregulation of immune homeostasis result in inflammatory diseases. These responses culminate in the production of a plethora of cytokines such as TSLP, IL-9, IL-25, and IL-33, which have been implicated in the pathogenesis of several inflammatory and autoimmune diseases. Shifting the balance of Th1, Th2, Th9, and Th17 responses have been the targets of therapeutic interventions in the treatment of these diseases. Here, we have briefly reviewed the innate and adaptive i3mmune responses in the lung. Genetic and environmental factors, and infection are the major causes of dysregulation of various functions of the lung. We have elaborated on the impact of inflammatory and infectious diseases, advances in therapies, and drug delivery devices on this critical organ. Finally, we have provided a comprehensive compilation of different inflammatory and infectious diseases of the lungs and commented on the pros and cons of different inhalation devices for the management of lung diseases. The review is intended to provide a summary of the immunology of the lung, with an emphasis on drug and device development.

Good Practices for the Laboratory Performance Testing of Aqueous Oral Inhaled Products (OIPs): an Assessment from the International Pharmaceutical Aerosol Consortium on Regulation and Science (IPAC-RS)

Multiple sources must be consulted to determine the most appropriate procedures for the laboratory-based performance evaluation of aqueous oral inhaled products (OIPs) for the primary measures, dose uniformity/delivery, and aerodynamic particle (droplet) size distribution (APSD). These sources have been developed at different times, mainly in Europe and North America, during the past 25 years by diverse organizations, including pharmacopeial chapter/monograph development committees, regulatory agencies, and national and international standards bodies. As a result, there is a lack of consistency across all the recommendations, with the potential to cause confusion to those developing performance test methods. We have reviewed key methodological aspects of source guidance documents identified by a survey of the pertinent literature and evaluated the underlying evidence supporting their recommendations for the evaluation of these performance measures. We have also subsequently developed a consistent series of solutions to guide those faced with the various associated challenges when developing OIP performance testing methods for oral aqueous inhaled products.

Liposomes or Extracellular Vesicles: A Comprehensive Comparison of Both Lipid Bilayer Vesicles for Pulmonary Drug Delivery

The rapid and non-invasive pulmonary drug delivery (PDD) has attracted great attention compared to the other routes. However, nanoparticle platforms, like liposomes (LPs) and extracellular vesicles (EVs), require extensive reformulation to suit the requirements of PDD. LPs are artificial vesicles composed of lipid bilayers capable of encapsulating hydrophilic and hydrophobic substances, whereas EVs are natural vesicles secreted by cells. Additionally, novel LPs-EVs hybrid vesicles may confer the best of both. The preparation methods of EVs are distinguished from LPs since they rely mainly on extraction and purification, whereas the LPs are synthesized from their basic ingredients. Similarly, drug loading methods into/onto EVs are distinguished whereby they are cell- or non-cell-based, whereas LPs are loaded via passive or active approaches. This review discusses the progress in LPs and EVs as well as hybrid vesicles with a special focus on PDD. It also provides a perspective comparison between LPs and EVs from various aspects (composition, preparation/extraction, drug loading, and large-scale manufacturing) as well as the future prospects for inhaled therapeutics. In addition, it discusses the challenges that may be encountered in scaling up the production and presents our view regarding the clinical translation of the laboratory findings into commercial products.

How Do Herbal Cigarettes Compare To Tobacco? A Comprehensive Review of Their Sensory Characters, Phytochemicals, and Functional Properties

Herbal cigarettes, known as tobacco-free or nicotine-free cigarettes, are those recognized as being-tobacco free, being composed of a mixture of various herbs claimed to lessen the smoking habit hazards. However, controversial data regarding its properties occur in the literature with no comprehensive overview or analysis of its effects. Like herbal smokeless tobacco, they are often used to substitute for tobacco products (primarily cigarettes) regarded as a "nonsmoking" aid. This review capitalizes on herbal cigarettes with regard to their quality characteristics, sensory attributes, chemical composition, and health properties to rationalize their choice as a nonsmoking aid. Furthermore, the impacts of heat and/or pyrolysis that occur during smoking on its chemical composition are presented for the first time. Some herbal smokes may produce notable metabolic problems that increase the risk of several chronic metabolic diseases. In general, burning substances from plants can have a variety of negative effects on the body attributed to toxic chemicals such as carbon monoxide, polyaromatics, nicotine, and N-nitrosamines. This review compiles and discusses the phytochemical compositions detected in various herbal cigarettes alongside sensory and quality attributes and health effects.

Advancements in the Design and Development of Dry Powder Inhalers and Potential Implications for Generic Development

Dry powder inhalers (DPIs) are drug-device combination products where the complexity of the formulation, its interaction with the device, and input from users play important roles in the drug delivery. As the landscape of DPI products advances with new powder formulations and novel device designs, understanding how these advancements impact performance can aid in developing generics that are therapeutically equivalent to the reference listed drug (RLD) products. This review details the current understanding of the formulation and device related principles driving DPI performance, past and present research efforts to characterize these performance factors, and the implications that advances in formulation and device design may present for evaluating bioequivalence (BE) for generic development.

Asthma History, Current Situation, an Overview of Its Control History, Challenges, and Ongoing Management Programs: An Updated Review

Asthma is a disease of the airways that is characterized by chronic inflammation and disordered airway function. The purpose of writing the current review paper is to review the history, current situation, control history, challenges, and ongoing management programs of asthma. Some official websites of known respiratory professional bodies were consulted for asthma guidelines, and information from Google Scholar® and PubMed® was also consulted. We reviewed around two hundred eight papers, and then, inclusion and exclusion criteria were applied to prepare this manuscript. Out of these papers, thirty papers, factsheets, and some official websites were used to prepare this manuscript. Physicians should follow already existing asthma guidelines in order to manage asthma. All prescribed medications should be continued. The government should make and adopt more strategies to promote the rational use of anti-asthmatic drugs and healthcare facilities and also make plans to disseminate more awareness among people about the schemes and programs made for safeguarding people against this life-threatening disease. We have done so much advancement to fight against this deadly disease, and we still need time to make the globe asthma-free. The number of people suffering from asthma is more than the number of people suffering from HIV infection and tuberculosis. Understanding the recommendations of professional bodies will assist in medical decision-making in asthma management. The individual needs of patients should be considered by healthcare professionals.

Graphical Abstract

Characterization of dry powder inhaler performance through experimental methods

Experimental methods provide means for the quality control of existing DPIs and for exploring the influence of formulation and device parameters well in advance of clinical trials for novel devices and formulations. In this review, we examine the state of the art of in vitro testing of DPIs, with a focus primarily on the development of accurate in vitro-in vivo correlations. Aspects of compendial testing are discussed, followed by the influence of flow profiles on DPI performance, the characterization of extrathoracic deposition using mouth-throat geometries, and the characterization of regional thoracic deposition. Additional experimental methods that can inform the timing of bolus delivery, the influence of environmental conditions, and the development of electrostatic charge on aerosolized DPI powders are reviewed. We conclude with perspectives on current in vitro methods and identify potential areas for future investigation, including the estimation of variability in deposition, better characterization of existing compendial methods, optimization of formulation and device design to bypass extrathoracic deposition, and the use of novel tracheobronchial filters that aim to provide more clinically relevant measures of performance directly from in vitro testing.

Andrographis paniculata Dosage Forms and Advances in Nanoparticulate Delivery Systems: An Overview

Andrographis paniculata is a well-known Asian medicinal plant with a major phytoconstituent of diterpene lactones, such as andrographolide, 14-deoxyandrographolide, and neoandrographolide. A World Health Organization (WHO) monograph on selected medicinal plants showed that A. paniculata extracts and its major diterpene lactones have promising anti-inflammatory, antidiabetic, antimalarial, anticancer, antifungal, antibacterial, antioxidant, and hypoglycemic activities. However, these active phytochemicals have poor water solubility and bioavailability when delivered in a conventional dosage form. These biological barriers can be mitigated if the extract or isolated compound are delivered as nanoparticles. This review discusses existing studies and marketed products of A. paniculata in solid, liquid, semi-solid, and gaseous dosage forms, either as an extract or isolated pure compounds, as well as their deficits in reaching maximum bioavailability. The pharmaceutics and pharmacological activity of A. paniculata as a nano-delivery system are also discussed.

Dry powder inhalation, part 1: ancient history and precursors to modern dry powder inhalers

INTRODUCTION

Inhalation of herbs and other compounds has a long history but habits for medical treatment are intertwined with rituals to obtain hallucinatory effects and pleasurable sensations. Several examples of inhaled herbs, and the diseases they were used for, based on early translations of ancient manuscripts related to inhalation were found to be speculative and inconsistent with each other in literature. They needed to be reconsidered and verified with the original sources of information.

AREAS COVERED

Examples of ancient inhalation and the development of early dry powder inhalers up to and including the first half of the twentieth century. Databases used for literature about historic events, ancient habits, and ancient science, included SmartCat, JSTOR, and ANDAT; various facts were verified via personal communication with historians and custodians of historic manuscripts and artifacts.

EXPERT OPINION

Inhalation does not necessarily require active creation of inhalable aerosols, smokes or fumes. Inhaling 'healthy air' with volatile and gaseous components, or fine aerosols in pine forests, on volcano slopes and at the seaside must be considered as inhalation therapy too. From this viewpoint, inhalation therapy may have been much more common and widespread and have a longer history than is currently known from written evidence.

Self-sealing MEMS spray-nozzles to prevent bacterial contamination of portable inhalers for aqueous drug delivery

Pulmonary drug delivery by portable inhalers is the gold standard in lung disease therapy. An increasing focus on environmentally friendly inhalation currently spurs the development of propellant-free devices. However, the absence of propellants in the drug creates a need for suitable sealing systems that can ensure the pathogenic safety of devices. Traditionally, liquid drug inhalers incorporate a spray nozzle and a separate check valve. Here we show a fully integrated MEMS-based spray system for aqueous drug solutions and demonstrate its bacterial safety. The device comprises a thin silicon membrane with spray orifices, which self-seal against a compliant parylene valve seat underneath. This sealing system prevents bacterial ingrowth in its default closed state, while actuation lifts the membrane from the valve seat upon pressurization and sprays an inhalable aerosol from the nozzles. To seal against bacterial contamination effectively, we found that a contact force between the valve seat and the membrane (featuring the spray nozzles) is needed. In our testing, both self-sealing and an otherwise identical unvalved version of the spray chip can be bacterially safe in continued use when thoroughly cleaned of excess fluids and subjected to low bacterial loads for brief periods. However, when directly exposed to \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$10^{7}$$\end{document}107 CFU/ml of our test organism Citrobacter rodentium for 24 h, unvalved systems become contaminated in nearly 90% of cases. In contrast, self-sealing spray chips reduced contamination probability by 70%. This development may enable preservative-free drug formulations in portable inhalers that use propellant-free aqueous drug solutions.

Shape-specific microfabricated particles for biomedical applications: a review

The storied history of controlled the release systems has evolved over time; from degradable drug-loaded sutures to monolithic zero-ordered release devices and nano-sized drug delivery formulations. Scientists have tuned the physico-chemical properties of these drug carriers to optimize their performance in biomedical/pharmaceutical applications. In particular, particle drug delivery systems at the micron size regime have been used since the 1980s. Recent advances in micro and nanofabrication techniques have enabled precise control of particle size and geometry-here we review the utility of microplates and discoidal polymeric particles for a range of pharmaceutical applications. Microplates are defined as micrometer scale polymeric local depot devices in cuboid form, while discoidal polymeric nanoconstructs are disk-shaped polymeric particles having a cross-sectional diameter in the micrometer range and a thickness in the hundreds of nanometer range. These versatile particles can be used to treat several pathologies such as cancer, inflammatory diseases and vascular diseases, by leveraging their size, shape, physical properties (e.g., stiffness), and component materials, to tune their functionality. This review highlights design and fabrication strategies for these particles, discusses their applications, and elaborates on emerging trends for their use in formulations.