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Automated microfluidics for nanoparticle fabrication

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Dr. Julia Rashba-Step, VP of R&D and Alliance Management at Phosphorex, a CDMO specialising in the formulation and manufacture of particles, explains how its using microfluidics to help its clients accelerate their nanoparticle fabrication and forward the development of new nanomedicines.

Key insights:

Effective drug delivery ensures that therapeutic agents reach their intended destination, releasing the active pharmaceutical ingredient at the target site while avoiding off-target effects. Nanoparticles can be used to encapsulate drug molecules, preventing premature metabolism as they pass through the body, as well as increasing penetration of the cell membrane. Some nanoparticle formulations also have the ability to target specific tissues where the treatment is needed. However, it has so far proven difficult to create optimised nanoparticle constructions with consistent particle monodispersity using conventional batch methods.

Interest in lipid nanoparticles (LNP), has grown significantly in the last decade, and the tremendous success of LNP-based mRNA vaccines during the COVID-19 pandemic has led to further explosive growth and new opportunities in this area. Nucleic acids – including plasmid DNA, oligonucleotides, small interfering RNA (siRNA), messenger RNA (mRNA) and microRNA (miRNA) – have shown a lot of promise for treating complex diseases. However, the effectiveness of these therapeutic agents strongly depends on them being able to reach the target tissue without deteriorating on route.

Traditional barriers to LNP production

LNPs are excellent delivery vehicles for the controlled release of these molecules, as they are capable of supplying the active pharmaceutical ingredient (API) to a specific action site while protecting it from premature degradation. Unfortunately, the fabrication of these important nanoparticles brings with it several challenges, and finding the correct composition can be both complex and extremely resource intensive. Properties such as the monodispersity and size of the particles are extremely important, but current production methods are either batch based or use large-scale continuous flow equipment, such as membranes, which produce inconsistent particle sizes.

These techniques also have poor encapsulation efficiency – the amount of drug or other cargo that ends up contained inside the particle – and require constant revalidation, resulting in the wastage of expensive materials and valuable time. The minimum sample size for existing fabrication methods is also typically large, further exacerbating the problem with the high costs and limited availability of both specialised lipids and the API. In addition, most drug development projects have very tight timelines, so it is necessary to rapidly establish a cost-efficient method for large-scale particle-encapsulated drug production once a good candidate had been discovered.

A novel method for particle formulation

Microfluidics is emerging as an excellent alternative for nanoparticle fabrication, as it allows experiments to be carried out with small quantities of materials and offers exceptional particle size monodispersity and encapsulation efficiency. The technique can also be scaled up to high throughput without requiring any changes in the fundamental particle formation method. Phosphorex is taking advantage of a dedicated nanoparticle production platform – the Automated Nanoparticle System (ANP System, Particle Works) – which uses microfluidics to offer automated set-up and processing of multiple samples.

The ANP System optimises the fabrication process through the rapid, automatic adjustment of different microfluidic parameters – such as flow rate or temperature – in order to find the ideal particle size, shape and structure, and has the potential to improve tissue targeting and drug encapsulation. The workflow begins with lipid and cargo being loaded into software-controlled reagent injection loops – the sole manual step in the protocol – then the system executes a series of experiments automatically, controlling pump operation, loop switching and washing without operator input.

The system reliably and repeatably generates particles ranging from 40 to 800 nm, and automation streamlines the screening of nanoparticles against a wide range of biological targets to allow the selection of candidates with the most promising performance. Other parameters – such as stability, charge, solubility and viscosity – can also be easily adjusted by using different lipids, reagents and microfluidic chips.

Phosphorex has successfully used this system to fabricate mRNA LNPs with a controlled particle size of between 80 and 150 nm, at rates between100 µl/min and 16 ml/min per channel, with encapsulation efficiencies of up to 98 per cent. This has allowed the team to work with small amounts of material during the development stage, reducing wastage of expensive APIs early on. The process can then be scaled up to a higher throughput without the need to revalidate the protocol at every stage, providing both fast and economical product development.

Conclusion

Automated lipid nanoparticle production offers a complete and convenient nanoparticle fabrication pathway, stretching from initial protocol development all the way to final manufacture, cutting out the need to continually change and revalidate methods between stages. Thanks to the ANP System, the team at Phosphorex now has a flexible and cost-effective tool for generating new LNP libraries and optimising the whole production process.

The platform allows better control of particle size distribution and, crucially, improves API encapsulation efficiency. The system is also highly scalable, as it operates in continuous flow and is able to incorporate multiple microfluidic chips working in parallel, ensuring that the same method can be used from start to finish. This innovative automated microfluidics set-up has significant potential for removing the common roadblocks to progress in nanoparticle-based therapies, such as time delays and financial limitations, contributing to advances in the clinical development of nanomedicines.

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