Aerosol delivery into small anatomical airway model through spontaneous engineered breathing

Design of a multilayer lung chip with multigenerational alveolar ducts to investigate the inhaled particle deposition

We present the development and application of a multilayer microfluidic lung chip designed to accurately replicate the human respiratory bronchi, providing an innovative platform for controlled particle deposition in the lung. By employing a quantitative control method of fluid velocity through the deformation of an elastic PDMS membrane, this platform mimics the passive breathing process in humans and allows for precise simulation of the respiration cycle. We utilized time-lapse photography of fluorescent particles in a water/glycerol solution to qualitatively observe fluid morphology in the channel, while a chip-aerosol exposure device combined with microscopy imaging was employed to visualise aerosol deposition. Both experimental and numerical simulation results showed that particle concentration decreased towards the distal generations of the lung, and that changes in breathing pattern significantly affected particle deposition trends. Furthermore, we found that increasing the residence time of particles in the channel facilitated deeper particle deposition, achievable by adjusting parameters such as breath-hold time, exhalation time, respiration cycle length, and tidal volume. The proposed microfluidic lung chip device has significant potential for future research in respiratory health and inhaled drug delivery, providing an efficient, cost-effective, and ethical alternative to traditional in vivo studies.

An experimental study of respiratory aerosol transport in phantom lung bronchioles

The transport and deposition of micrometer-sized particles in the lung is the primary mechanism for the spread of aerosol borne diseases such as corona virus disease-19 (COVID-19). Considering the current situation, modeling the transport and deposition of drops in human lung bronchioles is of utmost importance to determine their consequences on human health. The current study reports experimental observations on deposition in micro-capillaries, representing distal lung bronchioles, over a wide range of Re that imitates the particle dynamics in the entire lung. The experiment investigated deposition in tubes of diameter ranging from 0.3 mm to 2 mm and over a wide range of Reynolds number (10-2 ⩽ Re ⩽ 103). The range of the tube diameter and Re used in this study is motivated by the dimensions of lung airways and typical breathing flow rates. The aerosol fluid was loaded with boron doped carbon quantum dots as fluorophores. An aerosol plume was generated from this mixture fluid using an ultrasonic nebulizer, producing droplets with 6.5 µm as a mean diameter and over a narrow distribution of sizes. The amount of aerosol deposited on the tube walls was measured using a spectrofluorometer. The experimental results show that dimensionless deposition (δ) varies inversely with the bronchiole aspect ratio (L ¯ ), with the effect of the Reynolds number (Re) being significant only at lowL ¯ . δ also increased with increasing dimensionless bronchiole diameter (D ¯ ), but it is invariant with the particle size based Reynolds number. We show that δ L ¯ ∼ R e - 2 for 10-2 ⩽ Re ⩽ 1, which is typical of a diffusion dominated regime. For Re ⩾ 1, in the impaction dominated regime, δ L ¯ is shown to be independent of Re. We also show a crossover regime where sedimentation becomes important. The experimental results conclude that lower breathing frequency and higher breath hold time could significantly increase the chances of getting infected with COVID-19 in crowded places.

Development of a Novel Hanging Drop Platform for Engineering Controllable 3D Microenvironments

Conventional biomedical research is mostly performed by utilizing a two-dimensional monolayer culture, which fails to recapitulate the three-dimensional (3D) organization and microenvironment of native tissues. To overcome this limitation, several methods are developed to fabricate microtissues with the desired 3D microenvironment. However, they tend to be time-consuming, labor-intensive, or costly, thus hindering the application of 3D microtissues as models in a wide variety of research fields. In the present study, we have developed a pressure-assisted network for droplet accumulation (PANDA) system, an easy-to-use chip that comprises a multichannel fluidic system and a hanging drop cell culture module for uniform 3D microtissue formation. This system can control the desired artificial niches for modulating the fate of the stem cells to form the different sizes of microtissue by adjusting the seeding density. Furthermore, a large number of highly consistent 3D glomerulus-like heterogeneous microtissues that are composed of kidney glomerular podocytes and mesenchymal stem cells have been formed successfully. These data suggest that the developed PANDA system can be employed as a rapid and economical platform to fabricate microtissues with tunable 3D microenvironment and cellular heterogeneity, thus can be employed as tissue-mimicking models in various biomedical research.

Triple Selection Strategy for In Situ Labeling of Circulating Tumor Cells with High Purity and Viability toward Preclinical Personalized Drug Sensitivity Analysis

Ex vivo culture of viable circulating tumor cells (CTCs) from individual patients has recently become an emerging liquid biopsy technology to investigate drug sensitivity and genomic analysis in cancer. However, it remains challenging to retrieve the CTCs with high viability and purity from cancer patients' blood using a rapid process. Here, a triple selection strategy that combines immunonegative enrichment, density gradient, and microfluidic-based size-exclusion methods is developed for in situ drug sensitivity testing. The CTC isolation chip consists of 4 independent microchannels that can evenly distribute the captured CTCs, allowing for independent in situ analysis event. The cancer cells are retrieved within 5 min with high viability (>95%), captured efficiency (78%), and high purity (99%) from 7.5 mL of blood cell mixed samples. Furthermore, the CTCs can be isolated from prostate cancer patients' blood samples and verified in situ using cancer-specific markers within 1.5 h, demonstrating the possibility to be applied to clinical practice. In situ drug sensitivity analysis demonstrates that the captured CTCs without and with cisplatin treatment for 1 day have survival rates of 87.5% and 0%, respectively. It is envisioned that this strategy may become a potential tool to identify suitable therapies prior to the treatment.

Continuous Cell Separation Using Microfluidic-Based Cell Retention Device with Alternative Boosted Flow

The development of a continuous process for cell separation is growing rapidly due to the current trend of cost-effective manufacturing in biological industries. The continuous cell separation process has a significant reduction in capital equipment costs and facility size compared to the conventional batch process. In the study, a multi-layered microfluidic-based device integrated with the porous membranes was fabricated for continuous size-based isolation of the cells based on the mechanism of restrictive cross-flow filtration, allowing the biological sample entered in a single inlet of the device and separated into two outlet streams. One stream which contained the cells returned back to the original sample fluid, while another stream with conditioned medium only was collected for later applications. The membrane fouling issue was overcome by introducing the alternative flow rate consisted of a set of higher and lower flows. The device integrated with the controllable flow restriction allows to increase the permeate flow rate, and alternative boosted flow demonstrates the high permeate flow rate (0.3 mL/min), high cell viability (> 98%), and increase of cell concentration (48%). As a result, we believe that the microfluidic-based continuous cell separation system is a promising tool for downstream bioprocess.