3D printed transwell-integrated nose-on-chip model to evaluate effects of air flow-induced mechanical stresses on mucous secretion

A comprehensive review on organ-on-chips as powerful preclinical models to study tissue barriers

In the preclinical stage of drug development, 2D and 3D cell cultures under static conditions followed by animal models are utilized. However, these models are insufficient to recapitulate the complexity of human physiology. With the developing organ-on-chip (OoC) technology in recent years, human physiology and pathophysiology can be modeled better than traditional models. In this review, the need for OoC platforms is discussed and evaluated from both biological and engineering perspectives. The cellular and extracellular matrix components are discussed from a biological perspective, whereas the technical aspects such as the intricate working principles of these systems, the pivotal role played by flow dynamics and sensor integration within OoCs are elucidated from an engineering perspective. Combining these two perspectives, bioengineering applications are critically discussed with a focus on tissue barriers such as blood-brain barrier, ocular barrier, nasal barrier, pulmonary barrier and gastrointestinal barrier, featuring recent examples from the literature. Furthermore, this review offers insights into the practical utility of OoC platforms for modeling tissue barriers, showcasing their potential and drawbacks while providing future projections for innovative technologies.

A Cell-Based Nasal Model for Screening the Deposition, Biocompatibility, and Transport of Aerosolized PLGA Nanoparticles

The olfactory region of the nasal cavity directly links the brain to the external environment, presenting a potential direct route to the central nervous system (CNS). However, targeting drugs to the olfactory region is challenging and relies on a combination of drug formulation, delivery device, and administration technique to navigate human nasal anatomy. In addition, in vitro and in vivo models utilized to evaluate the performance of nasal formulations do not accurately reflect deposition and uptake in the human nasal cavity. The current study describes the development of a respirable poly(lactic-co-glycolic acid) nanoparticle (PLGA NP) formulation, delivered via a pressurized metered dose inhaler (pMDI), and a cell-containing three-dimensional (3D) human nasal cast model for deposition assessment of nasal formulations in the olfactory region. Fluorescent PLGA NPs (193 ± 3 nm by dynamic light scattering) were successfully formulated in an HFA134a-based pMDI and were collected intact following aerosolization. RPMI 2650 cells, widely employed as a nasal epithelial model, were grown at the air-liquid interface (ALI) for 14 days to develop a suitable barrier function prior to exposure to the aerosolized PLGA NPs in a glass deposition apparatus. Direct aerosol exposure was shown to have little effect on cell viability. Compared to an aqueous NP suspension, the transport rate of the aerosolized NPs across the RPMI 2650 barrier was higher at all time points indicating the potential advantages of delivery via aerosolization and the importance of employing ALI cellular models for testing respirable formulations. The PLGA NPs were then aerosolized into a 3D-printed human nasal cavity model with an insert of ALI RPMI 2650 cells positioned in the olfactory region. Cells remained highly viable, and there was significant deposition of the fluorescent NPs on the ALI cultures. This study is a proof of concept that pMDI delivery of NPs is a viable means of targeting the olfactory region for nose-to-brain drug delivery (NTBDD). The cell-based model allows not only maintenance under ALI culture conditions but also sampling from the basal chamber compartment; hence, this model could be adapted to assess drug deposition, uptake, and transport kinetics in parallel under real-life settings.

The Path from Nasal Tissue to Nasal Mucosa on Chip: Part 2-Advanced Microfluidic Nasal In Vitro Model for Drug Absorption Testing

The nasal mucosa, being accessible and highly vascularized, opens up new opportunities for the systemic administration of drugs. However, there are several protective functions like the mucociliary clearance, a physiological barrier which represents is a difficult obstacle for drug candidates to overcome. For this reason, effective testing procedures are required in the preclinical phase of pharmaceutical development. Based on a recently reported immortalized porcine nasal epithelial cell line, we developed a test platform based on a tissue-compatible microfluidic chip. In this study, a biomimetic glass chip, which was equipped with a controlled bidirectional airflow to induce a physiologically relevant wall shear stress on the epithelial cell layer, was microfabricated. By developing a membrane transfer technique, the epithelial cell layer could be pre-cultivated in a static holder prior to cultivation in a microfluidic environment. The dynamic cultivation within the chip showed a homogenous distribution of the mucus film on top of the cell layer and a significant increase in cilia formation compared to the static cultivation condition. In addition, the recording of the ciliary transport mechanism by microparticle image velocimetry was successful. Using FITC-dextran 4000 as an example, it was shown that this nasal mucosa on a chip is suitable for permeation studies. The obtained permeation coefficient was in the range of values determined by means of other established in vitro and in vivo models. This novel nasal mucosa on chip could, in future, be automated and used as a substitute for animal testing.

The Path from Nasal Tissue to Nasal Mucosa on Chip: Part 1-Establishing a Nasal In Vitro Model for Drug Delivery Testing Based on a Novel Cell Line

In recent years, there has been a significant increase in the registration of drugs for nasal application with systemic effects. Previous preclinical in vitro test systems for transmucosal drug absorption studies have mostly been based on primary cells or on tumor cell lines such as RPMI 2650, but both approaches have disadvantages. Therefore, the aim of this study was to establish and characterize a novel immortalized nasal epithelial cell line as the basis for an improved 3D cell culture model of the nasal mucosa. First, porcine primary cells were isolated and transfected. The P1 cell line obtained from this process was characterized in terms of its expression of tissue-specific properties, namely, mucus expression, cilia formation, and epithelial barrier formation. Using air-liquid interface cultivation, it was possible to achieve both high mucus formation and the development of functional cilia. Epithelial integrity was expressed as both transepithelial electrical resistance and mucosal permeability, which was determined for sodium fluorescein, rhodamine B, and FITC-dextran 4000. We noted a high comparability of the novel cell culture model with native excised nasal mucosa in terms of these measures. Thus, this novel cell line seems to offer a promising approach for developing 3D nasal mucosa tissues that exhibit favorable characteristics to be used as an in vitro system for testing drug delivery systems.

Effect of poly (ethylene glycol) on 3D printed PLA/PEG blend: A study of physical, mechanical characterization and printability assessment

The growing popularity of additive manufacturing in the science, industry is associated with high-quality products for futuristic applications. This study presents an in-depth characterization and analysis of the effect of poly (ethylene glycol) (PEG) having molecular weight 6000 g/mol used with various concentrations (1%,3%,5%) to modify the 3D printed Polylactide (PLA) part. The influence of PEG on the morphology, structure, thermal, wettability and mechanical properties of the 3D-printed PLA/PEG part was investigated. Herein, the mechanical property of injection moulding, 3D printed specimens, and finite element analysis (FEA) simulation results were also compared. The structure and properties of PLA/PEG blends were different from those of virgin PLA. By DSC analysis, it was found that the glass transition temperature (T_g) and cold crystallization temperature decreased in the case of the PLA/PEG blend. From TGA it was observed that PLA/PEG blend was thermally stable. It was shown that with the addition of PEG into PLA the tensile strength and young's modulus decrease, whereas elongation percentage and impact strength increase predominantly. The contact angle results indicate that the addition of PEG lowers the contact angle value of the PLA/PEG blend (from 69.32 ± 1.4° to 45.67 ± 1.2°) and increases surface wettability. With 5% PEG loading, PLA/PEG blend showed optimum structural and mechanical properties together with simple processibility.

Droplet Detection and Sorting System in Microfluidics: A Review

Since being invented, droplet microfluidic technologies have been proven to be perfect tools for high-throughput chemical and biological functional screening applications, and they have been heavily studied and improved through the past two decades. Each droplet can be used as one single bioreactor to compartmentalize a big material or biological population, so millions of droplets can be individually screened based on demand, while the sorting function could extract the droplets of interest to a separate pool from the main droplet library. In this paper, we reviewed droplet detection and active sorting methods that are currently still being widely used for high-through screening applications in microfluidic systems, including the latest updates regarding each technology. We analyze and summarize the merits and drawbacks of each presented technology and conclude, with our perspectives, on future direction of development.