Non-Cellular Layers of the Respiratory Tract: Protection against Pathogens and Target for Drug Delivery

A comprehensive analytical model for predicting drug absorption in the olfactory region: Application to nose-to-brain delivery

Nose-to-brain drug delivery offers a promising route for administering pharmaceutical substances directly to the brain. However, this pathway faces significant challenges, such as mucociliary clearance and enzymatic activity in the nasal cavity, which limit drug absorption. Although several formulation strategies exist to enhance drug solubility, diffusion across the airway surface liquid, and protection from enzymatic degradation, there is a lack of tools to systematically evaluate which strategy is best suited for specific molecules. To address this, we developed an analytical model of the olfactory region that integrates drug dissolution, diffusion through the mucus and periciliary layers, advection by mucociliary clearance, and enzymatic degradation. This analytical model allows to estimate the fraction of a drug, formulated as a powder and deposited in the olfactory region, that is indeed dissolved in the mucus and absorbed by the cells, and to identify the most influential physicochemical properties in the absorption process. To demonstrate the model's utility, we 3D-printed custom-made diffusion cells to measure experimentally the diffusion coefficients of caffeine, levodopa, and paliperidone palmitate, incorporating these values into our simulations. Based on these data, we predicted drug absorption levels and proposed strategies to optimise them. By applying the model to an existing formulation, we demonstrated that careful adjustments to a drug's properties can significantly enhance the fraction absorbed in the olfactory region. Additionally, we explored how the site of drug deposition, influenced by the delivery device, impacts absorption by affecting residence time in the olfactory region. Overall, our analytical model serves as a valuable tool for the development of effective nose-to-brain formulations and the selection of optimal administration devices, streamlining the process and reducing the need for extensive in vitro and in vivo testing.

Advances of dual-organ and multi-organ systems for gut, lung, skin and liver models in absorption and metabolism studies

Drug development is a costly and timely process with high risks of failure during clinical trials. Although in vitro tissue models have significantly advanced over the years, thus fostering a transition from animal-derived models towards human-derived models, failure rates still remain high. Current cell-based assays are still not able to provide an accurate prediction of the clinical success or failure of a drug candidate. To overcome the limitations of current methods, a variety of microfluidic systems have been developed as powerful tools that are capable of mimicking (micro)physiological conditions more closely by integrating physiological fluid flow conditions, mechanobiological cues and concentration gradients, to name only a few. One major advantage of these biochip-based tissue cultures, however, is their ability to seamlessly connect different organ models, thereby allowing the study of organ-crosstalk and metabolic byproduct effects. This is especially important when assessing absorption, distribution, metabolism, and excretion (ADME) processes of drug candidates, where an interplay between various organs is a prerequisite. In the current review, a number of in vitro models as well as microfluidic dual- and multi-organ systems are summarized with a focus on absorption (skin, lung, gut) and metabolism (liver). Additionally, the advantage of multi-organ chips in identifying a drug's on and off-target toxicity is discussed. Finally, the potential high-throughput implementation and modular chip design of multi-organ-on-a-chip systems within the pharmaceutical industry is highlighted, outlining the necessity of reducing handling complexity.

Preventive effect of quinoa polysaccharides on lipopolysaccharide-induced inflammation in mice through gut microbiota regulation

Inflammation significantly influences the development of gastrointestinal (GI) diseases such as inflammatory bowel diseases (IBD)and ulcerative colitis, which disrupts normal digestive functions, leading to tissue damage and various symptoms. This research explores the preventive effects of quinoa polysaccharides (QPS) on lipopolysaccharide (LPS)-induced systemic acute inflammation in mice and their mechanism of action. The findings revealed that QPS alleviated LPS-induced inflammation symptoms, enhanced the mice behavior score and their immune organ index, reduced pro-inflammatory cytokines (IL-6, TNF-α and IL-1β) levels, elevated the expression level of tight junction proteins (ZO-1, MUC2). Additionally, the levels of superoxide dismutase (SOD), malondialdehyde (MDA) and total antioxidant capacity (T-AOC) were improved via QPS administration. Further, our research suggested that QPS enhanced the diversity and abundance of gut microbiota compared to that of LPS mice, leading to an increase in the short-chain fatty acids in mice feces. Linear discriminant analysis (LDA) effect size (LEfSe) showed that QPS administration could lead to a range of gut biomarkers, promoting the enhancement of polysaccharide-metabolizing bacteria. The results of 16S rRNA sequencing indicated that QPS alleviates LPS-induced inflammation by enhancing the richness of beneficial bacteria such as Bacteroides and Lactobacillus. Linear discriminant analysis (LDA) effect size (LEfSe) showed that QPS administration could lead to a range of gut biomarkers, promoting the enhancement of polysaccharide-metabolizing bacteria. UPLC Q-TOF-MS was performed to analyze metabolites in the fecal samples. LPS administration significantly altered metabolite levels detected in mice feces in which some metabolites have decreased such as xanthosine and hypoxanthine while an increase in some metabolites in mice that received QPS, metabolomics analysis showed the beneficial effects of QPS primarily mediated via amino and bile acid-related metabolism pathways. Our research could offer the basis for further studies and applications of quinoa polysaccharides.

Improved Olfactory Deposition of Theophylline Using a Nanotech Soft Mist Nozzle Chip

Currently, nasal administration of active pharmaceutical ingredients is most commonly performed using swirl-nozzle-based pump devices or pressurized syringes. However, they lead to limited deposition in the more active regions of the nasal cavity, especially the olfactory region, which is crucial for nose-to-brain drug delivery. This research proposes to improve deposition in the olfactory region by replacing the swirl nozzle with a nanoengineered nozzle chip containing micrometer-sized holes, which generates smaller droplets of 10-50 μm travelling at a lower plume velocity. Two nanotech nozzle chips with different hole sizes were tested at different inhalation flow rates to examine the deposition patterns of theophylline, a hyposmia treatment formulation, using a nasal cavity model. A user study was also conducted and showed that the patient instructions influenced the inhalation flow rate characteristics. Targeted flow rates of between 0 and 25 L/min were used for the in vitro deposition study, yielding 21.5-31.5% olfactory coverage. In contrast, the traditional swirl nozzle provided only 10.8% coverage at a similar flow rate. This work highlights the potential of the nanotech soft mist nozzle for improved intranasal drug delivery, particularly to the olfactory region.

Mucus Hypersecretion in Chronic Obstructive Pulmonary Disease and Its Treatment

Most patients diagnosed with chronic obstructive pulmonary disease (COPD) present with hallmark features of airway mucus hypersecretion, including cough and expectoration. Airway mucus function as a native immune system of the lung that severs to trap particulate matter and pathogens and allows them to clear from the lung via cough and ciliary transport. Chronic mucus hypersecretion (CMH) is the main factor contributing to the increased risk of morbidity and mortality in specific subsets of COPD patients. It is, therefore, primarily important to develop medications that suppress mucus hypersecretions in these patients. Although there have been some advances in COPD treatment, more work remains to be done to better understand the mechanism underlying airway mucus hypersecretion and seek more effective treatments. This review article discusses the structure and significance of mucus in the lungs focusing on gel-forming mucins and the impacts of CMH in the lungs. Furthermore, we summarize the article with pharmacological and nonpharmacological treatments as well as novel and interventional procedures to control CMH in COPD patients.

A Novel Preparation Technique for Human Nasal Respiratory Mucosa to Disclose Its Glycosylation Pattern for Bioadhesive Drug Delivery

To shed some light on glycotargeting as a potential strategy for nasal drug delivery, a reliable preparation method for human nasal mucosa samples and a tool to investigate the carbohydrate building blocks of the glycocalyx of the respiratory epithelium are required. Applying a simple experimental setup in a 96-well plate format together with a panel of six fluorescein-labeled lectins with different carbohydrate specificities allowed for the detection and quantification of accessible carbohydrates in the mucosa. As confirmed by binding experiments at 4 °C, both quantitatively by fluorimetry and qualitatively by microscopy, the binding of wheat germ agglutinin exceeded that of the others by 150% on average, indicating a high content of N-acetyl-D-glucosamine and sialic acid. Providing energy by raising the temperature to 37 °C revealed uptake of the carbohydrate-bound lectin into the cell. Moreover, repeated washing steps during the assay gave a slight hint as to the influence of mucus renewal on bioadhesive drug delivery. All in all, the experimental setup reported here for the first time is not only a suitable approach to estimating the basics and potential of nasal lectin-mediated drug delivery but also meets the needs for answering a broad variety of scientific questions involving the use of ex vivo tissue samples.