April 17, 2024 PAO-04-24-NI-02
Microfluidic devices are designed to manipulate micro-, nano-, and/or picoliter volumes of liquids and gases within microscale channels and chambers with precise control.1 Microscale pumps, valves, mixers, and other systems mix, transport, separate, and heat these liquids and gases, while microsensors provide control. Microfluidic devices leverage laminar rather than turbulent flow, leading to more consistent fluid movement. They also make use of the surface-to-volume ratios and surface interactions that are unique to the microscale.2
The benefits of microfluidic technologies include more consistent and predictable liquid flows, reduced material and energy consumption, and greater control — all of which result in improved efficiency and accuracy at reduced costs.3 They also enable the simultaneous performance of multiple operations, facilitating both process automation and rapid implementation and analysis of physical experiments while ensuring high data quality.1,4
In the biopharmaceutical industry, potential applications for microfluidics include diagnostics; analytics; process development, including high-throughput screening; biomanufacturing; and drug delivery, as well as therapeutics. This technology is enabling personalized medicine and point-of-care diagnostics, automation of a wide variety of laboratory workflows for greater speed and efficiency, unique approaches to cell culture, and continuous manufacturing of lipid nanoparticles and microparticles for oral solid dosage formulations.1
Of particular interest in many biopharmaceutical applications is droplet microfluidics, which involves the generation of droplets of a specified diameter.5 This technology is used in high-throughput screening, bioprocessing, and analytical applications.
Within microfluidic devices, fluid flow can be pressure driven or based on electroosmotic flow.5 Construction materials include both rigid and flexible polymers. Several methods have been investigated for the manufacture of microfluidic devices. One of the most attractive options is 3D printing, as it allows for construction of complex devices without requiring highly skilled workers operating at difficult scales.
One of the common challenges in early drug development and diagnostic method development is access to only minute quantities of material. The inherent nature of microfluidics overcomes this issue; analyses not only require minute sample quantities but often can be completed extremely rapidly and in parallel within a very small footprint, saving both time and money.5 In addition, unlike miniature liquid-handling systems, microfluidics, owing to the unique behaviors of materials at the micro scale, can provide significantly more information about the physical properties and behaviors of molecules. Furthermore, the greater design freedom available in the microfluidics space enables implementation of a wider array of scale-down models and the use of many different analytical techniques, as they can be integrated with many spectroscopy instruments that do not work with microplates.
Any analytical methods incorporated into microfluidic devices must be extremely sensitive and accurate. One of the most common techniques, therefore, is fluorescence.5 Microfluidic devices have also been used for DNA and protein analysis, and, when linked to mass spectrometry instruments, have enabled accurate evaluation of picomole quantities of peptides.6
Microfluidic sensors leveraging cells, enzymes, antibodies, aptamers, and other biomolecules can also be used as sensors for the detection of small molecules, proteins, antigens, RNA/DNA, electrolytes, gases, and other substances of interest for many different types of applications, including clinical diagnostics.4 In fact, some microfluidic devices integrate cell isolation, cell lysis, DNA extraction, polymerase chain reaction (PCR), and detection processes.
Digital droplet PCR (ddPCR) is one of the best-known and most widely adopted methods leveraging microfluidic technologies in the biopharma industry today,4 particularly for analysis of viral vectors. With this technique, it is possible to evaluate samples much more rapidly, with the potential to increase throughput from hundreds to millions of analyses in the same timeframe.
Examples of microfluidic analytical devices include the 2100 BioAnalyzer (Agilent Technologies) for automated electrophoresis, the LabChip GXII (Perkin Elmer) for automated sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis, and the Biacore™ X100 (Cytiva) for surface plasmon resonance analysis.5
Meanwhile, researchers at Texas A&M University and the U.S. Army Combat Capabilities Development Command Army Research Laboratory (ARL) have developed a droplet microfluidic device (DNA ENhanced TRAnsfer Platform) that automatically transports DNA from one cell to another across a wide variety of cell types, including highly engineered cells and uncommon natural strains, enabling rapid analysis of genetic modifications, which is typically a time- and labor-intensive activity.7
One of the main foci of biopharmaceutical companies today is increasing the efficiency and productivity of process development to reduce time to the clinic and the market and to reduce the costs of new drugs. Unsurprisingly, microfluidics has attracted significant attention for its potential to facilitate achievement of these goals. Integrated devices can be used for rapid process characterization and optimization.8
Examples of microfluidic devices under investigation for use in bioprocess development include devices for DNA assembly and transformation, high-throughput screening of cell libraries, and bioreactors for process optimization.9 Many perform operations on single cells using the unique fluid-flow properties within microfluidic devices comprising picoliter-scale compartments, gel beads, and/or single-cell imaging capabilities. Underlying all these microfluidic technologies are solutions for increasing throughput, parallelization, and automation. A key application highly sought in the industry is acceleration of cell line development, a typical bottleneck in chemistry, manufacturing, and controls (CMC) for drug development.
Some technologies leverage combinatorial DNA synthesis in droplets.9 This may be coupled with electrowetting and digital droplet microfluidics techniques for transferring DNA into cells. Transfection of hard-to-transfect cells has also been shown to be facilitated within microfluidic devices. Even cell sorting can now be performed in microfluidic devices using technologies such as fluorescence-activated cell sorting (FACS), magnetic sorting, cell size–based sorting by deterministic lateral displacement or inertial microfluidics, acoustophoretic sorting, and droplet sorting. Label-free detection methods that can be used within microfluidic devices are also being developed, including some based on Raman spectroscopy. Cell growth–based selection assessing the quantity of cells or metabolic profiles is also being explored.
Efforts are also being directed to the development of microfluidic bioreactors.4,5,8–10 Theoretically, microfluidic systems can be used to mimic batch, fed-batch, and perfusion processes.9 Furthermore, the design of these devices and the choice of materials can provide not only temporal and spatial control but also specific surface conditions and nano-structured topographies to meet specific needs. Devices have been generally focused on adherent cell culture and designed to mimic both 2D and 3D systems.10 Standardization will be essential if such microfluidic devices are to see widespread adoption for bioprocess development.
Microfluidic devices serving as miniaturized bioreactors that mimic batch manufacturing are often based in microwells and use microfluidic droplets for cell culture.9 Some are designed to enable cell culture of single cells in a high-throughput manner to rapidly identify the highest-performing clones.4 These devices are at an early development stage, but various types of cells have been shown to grow within such devices. For instance, picoliter bioreactors assembled for single-cell fermentation set up within microscopes have been used to screen cell culture processes with real-time visualization.5
Microfluidics can also benefit process development of downstream operations.5 Researchers have demonstrated the potential for microfluidic solutions for chromatography, including the purification of monoclonal antibodies and parallel chromatography runs for nine different protein concentrations.
One important key to the success for microfluidic devices designed to facilitate bioprocess development is the incorporation of effective microsensors. Such devices could not only increase throughput and reduce cost but also provide more reliable and accurate data than what is obtainable using miniature bioreactor systems.10,11 Typical examples include optical, spectroscopic, and image-analysis techniques. The best solutions involve non-invasive methods that do not disturb the cell culture.
The use of microfluidic devices for actual biopharmaceutical manufacturing and not just high-throughput screening in process development remains largely conceptual at this point, although many academic and industrial research groups are actively investigation the deployment of various microfluidic technologies.
The intent is to miniaturize existing production systems and protocols in microfluidic cartridges to leverage the precise control, parallelization, and other benefits that microfluidics offers.8 Two leading potential applications are parallel production of cell lines and continuous drug substance encapsulation to generate drug products in novel delivery systems.
Researchers at the Massachusetts Institute of Technology have developed an industrial-scale spiral inertial microfluidic device for continuous clarification of proteins following perfusion-based mammalian cell culture that can achieve clog-free cell retention and high product recovery at a volume process rate of 1 L/min.12 The microfluidic cell retention device could therefore potentially be scaled to process harvest fluid from a 1,000-L bioreactor.
A microfluidic device capable of high-throughput size-based cell separation using inertial sorting was then developed to enable microfluidic perfusion cell cutlure.13 It was shown to successfully achieve high-throughput and high-concentration removal of dead cells from culture. The microfluidic perfusion and clarification systems were integrated with a novel nanofluidic filter array providing continuous online purity monitoring of the proteins in the cell culture supernatant. The researchers believe that the microfluidic clarification device and coupled process analytical technology (PAT) solution addresses key issues with conventional membrane filiation, including filter clogging, low product recovery, manual sample preparation, and offline analysis. They also suggest that the nanofluidic filter array could replace the existing offline analytical technologies for protein purity monitoring.
One of the most promising potential applications for microfluidics in drug manufacturing is the production of encapsulated drug substances as nanoparticles that can facilitate drug delivery.14 Mixing of two or more immiscible fluids in laminar flow in the presence of an appropriate surfactant results in the formation of nanoscale emulsion droplets with uniform properties. As a result, microfluidic technologies are attractive for the generation of nanoparticles in which a drug substance is encapsulated. They can also be used for encapsulation of cells into hydrogels to generate artificial organs. In a similar vein, microfibers generated using microfluidics can be constructed into implantable patches for drug delivery. It is also worth noting that this technology may be useful for enhancing the efficiency of transfection processes.
Another significant application of microfluidics involves organ-on-a-chip technologies, which are designed to mimic the functioning of human organs and are used in diagnostic and drug discovery and development applications, as well to increase understanding of organ physiology.4 They often comprise three-dimensional channels lined with living cells and appropriate mechanical and biochemical microenvironments to replicate the interactions and interfaces that take place in a specific type of tissue. Media flowing through the channels mimics the bloodstream and is injected with a compound of interest to see how it impact the behavior of the cells.
Microfluidics can be used not only in bioprocess research, development, and manufacturing but within diagnostic devices and drug products themselves.
One diagnostic technology of note enables “minimally disruptive fluid and cell manipulations within living cultures.”15 The device was shown to seed and culture multiple types of cells in specific special patterns and enable removal of undesired adherent cells using a focused trypsin flow. Fluids can also be sampled, and “biopsies” of cells anywhere with the culture chamber can be performed for external analysis. External electronics automate device operation, enabling computer-controlled tissue engineering. The researchers anticipate scaling the technology to three-dimensional microfluidic scaffolds to facilitate the development of tissue-engineering technologies with clinical applications.
Additionally, microfluidic cell-separation devices are being employed for diagnostic applications in which certain cells must be isolated from blood.4 In particular, microfluidic technologies are useful for detecting bacteria in blood, which is critical for the diagnosis of blood sepsis. Similar approaches can be used to separate white and red blood cells, an important step in many medical diagnostic applications.
Several companies are pursuing the commercialization of microfluidic technologies for various biopharmaceutical applications. Selected examples include:
Significant advances in micro- and nanoscale fabrication and sensor technologies are enabling the design and construction of highly complex microfluidics devices with a broad array of applications in the biopharmaceutical industry. New solutions are being explored in both academic and industrial settings, with much progress being driven by innovative small and emerging pharma and biotech companies targeting applications in precision medicine, point-of-care-diagnostics, drug discovery and development, lab automation, bioprocessing, drug delivery, and more.
Underlying the growing interest in microfluidics technologies is their potential to increase the efficiency and productivity of all aspects of drug discovery, development, and manufacturing, as well as some aspects within healthcare. With ever-growing pressures to reduce the time and cost of drug development and manufacturing and the move toward targeted and personalized medicine, microfluidic technologies will likely play an increasing role in future advances within the biopharmaceutical and overall healthcare industries.
References
Dr. Challener is an established industry editor and technical writing expert in the areas of chemistry and pharmaceuticals. She writes for various corporations and associations, as well as marketing agencies and research organizations, including That’s Nice and Nice Insight.
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