Periodic Reporting for period 1 - MuST (On-chip model of mucociliary clearance for the design of drug formulations aimed at chronic respiratory diseases)
Reporting period: 2024-07-01 to 2026-06-30
Chronic respiratory diseases (CRDs) caused 4 million deaths worldwide in 2019. CRD treatments are often administered by inhalation in particulate formulations. However, mucociliary clearance (MCC) acts as an effective physical barrier preventing drugs from reaching the target cells. This mechanism relies on the beating of cilia on the bronchi surface, which allows the displacement of the overlying mucus layer. Inhaled drugs are thus trapped by the mucus and quickly evacuated from the airways.
The objective of the MuST project was to model the mechanism of MCC using a microfluidic chip, to assess drug penetration through the moving mucus and thus provide a screening platform for new drug formulations. Our main objective could be subdivided into three research objectives: 1) Develop an adequate synthetic mucus model; 2) Reproduce the mucociliary clearance mechanism on a microfluidic chip; 3) Screen innovative drug formulations using our chip.
In this project, we combined biophysics, physical chemistry, soft condensed matter, and nanomedicine expertise. The originality of our approach lies in 3 key aspects: 1) We aimed to develop a synthetic mucus model that reproduces all the properties of native human mucus; 2) We chose to design a non-cellular MCC model, which will provide an easy, quick, cheap, and reproducible alternative to cell-based MCC models; 3) We aimed to apply an original technique called differential dynamic microscopy (DDM) to characterize the drug behaviour in the chip. DDM is perfectly adapted to measure particle diffusion in biological hydrogels under flowing conditions.
Our innovative screening platform should pave the way to design more efficient formulations to treat CRDs, with higher delivery rates, thereby improving the available treatments and lowering their costs. This project is in line with the United Nations’ aim “to reduce by 2030 by one-third premature mortality from non-communicable diseases [including CRDs] through prevention and treatment”.
The objective of the MuST project was to model the mechanism of MCC using a microfluidic chip, to assess drug penetration through the moving mucus and thus provide a screening platform for new drug formulations. Our main objective could be subdivided into three research objectives: 1) Develop an adequate synthetic mucus model; 2) Reproduce the mucociliary clearance mechanism on a microfluidic chip; 3) Screen innovative drug formulations using our chip.
In this project, we combined biophysics, physical chemistry, soft condensed matter, and nanomedicine expertise. The originality of our approach lies in 3 key aspects: 1) We aimed to develop a synthetic mucus model that reproduces all the properties of native human mucus; 2) We chose to design a non-cellular MCC model, which will provide an easy, quick, cheap, and reproducible alternative to cell-based MCC models; 3) We aimed to apply an original technique called differential dynamic microscopy (DDM) to characterize the drug behaviour in the chip. DDM is perfectly adapted to measure particle diffusion in biological hydrogels under flowing conditions.
Our innovative screening platform should pave the way to design more efficient formulations to treat CRDs, with higher delivery rates, thereby improving the available treatments and lowering their costs. This project is in line with the United Nations’ aim “to reduce by 2030 by one-third premature mortality from non-communicable diseases [including CRDs] through prevention and treatment”.
1st objective - Develop an adequate synthetic mucus model
The porous structure of patient-derived mucus was characterised by electron microscopy, thanks to a newly applied technique for sample preparation called high-pressure freezing. This technique demonstrated great results in maintaining the porous structure of mucus.
Various synthetic mucus were prepared and characterized, including crosslinked snail slime, following an already established protocol. This snail-derived mucus was found to accurately mimic the structure and rheology of human mucus, making it a promising synthetic mucus model.
2nd objective - Reproduce the mucociliary clearance mechanism on a microfluidic chip
Different microfluidic chips were designed and fabricated. They all displayed magnetic micropillar arrays on the bottom of the channels. These micropillars were first characterised in terms of morphology and magnetic response. They were then proven to generate flow in the channel when actuated via an underlying rotating magnet. The velocity profiles were determined for model viscoelastic fluids with rheological properties covering the typical ones of pulmonary mucus.
3rd objective - Screen innovative drug formulations using our chip
This research axis requires the two first objectives to be reached. Due to the early termination of the project, it could not be tackled.
The porous structure of patient-derived mucus was characterised by electron microscopy, thanks to a newly applied technique for sample preparation called high-pressure freezing. This technique demonstrated great results in maintaining the porous structure of mucus.
Various synthetic mucus were prepared and characterized, including crosslinked snail slime, following an already established protocol. This snail-derived mucus was found to accurately mimic the structure and rheology of human mucus, making it a promising synthetic mucus model.
2nd objective - Reproduce the mucociliary clearance mechanism on a microfluidic chip
Different microfluidic chips were designed and fabricated. They all displayed magnetic micropillar arrays on the bottom of the channels. These micropillars were first characterised in terms of morphology and magnetic response. They were then proven to generate flow in the channel when actuated via an underlying rotating magnet. The velocity profiles were determined for model viscoelastic fluids with rheological properties covering the typical ones of pulmonary mucus.
3rd objective - Screen innovative drug formulations using our chip
This research axis requires the two first objectives to be reached. Due to the early termination of the project, it could not be tackled.
Crosslinked snail slime was proven to be a promising synthetic mucus model, accurately mimicking mucus structure and rheology. The commercial availability of snail slime (for the cosmetic industry) makes it suitable for larger-scale needs. Further research is yet needed to compare its biochemical composition with the one of human mucus.
The technique of high-pressure freezing applied to prepare mucus samples for electron microscopy was shown to successfully preserve the porous structure. It will be valuable for future studies about the structure of mucus and other biological gels.
The flow patterns observed in the microfluidic chip highlight the potential of this magnetic micropillar-based system for mimicking MCC. Yet, the chip requires further optimisation and needs to be used with our synthetic mucus model. To validate the use of our chip as an MCC model, we will need to ensure that the behaviour of model particles is the same as in patient-derived bronchial tissue.
The technique of high-pressure freezing applied to prepare mucus samples for electron microscopy was shown to successfully preserve the porous structure. It will be valuable for future studies about the structure of mucus and other biological gels.
The flow patterns observed in the microfluidic chip highlight the potential of this magnetic micropillar-based system for mimicking MCC. Yet, the chip requires further optimisation and needs to be used with our synthetic mucus model. To validate the use of our chip as an MCC model, we will need to ensure that the behaviour of model particles is the same as in patient-derived bronchial tissue.