Leveraging advances in the microfluidic production of hydrogels, it is now possible to produce biopolymer-based hydrogel scaffolds that can mimic the extracellular matrix for tissue engineering. To learn more about the novel solution, we spoke with ClexBio’s CEO, Dr. Armend G. Håti, and CSO, Dr. Manuel Schweikle. This article explores their innovative research focusing on cell encapsulation in alginate hydrogels for tissue engineering and discusses the prevailing challenges and future directions in the field.
Overcoming challenges in the fabrication of microfluidic hydrogels
At its core, ClexBio is a regenerative medicine company. Our primary mission is to bring functioning tissues to the clinic. But even in the early stages of our research, we knew that we needed to start with a single cell to achieve this vision. This realization quickly led us into the field of microfluidics, with a focus on the high-throughput, high-precision single-cell analysis capabilities of droplet-based microfluidics for tissue engineering applications.
Droplet-based microfluidics, based on the compartmentalization of cells into picoliter-sized droplets, enables the manipulation and analysis of single cells and their secreted products within controlled microenvironments. Conventionally, the droplets are composed of a water-in-oil emulsion. However, to support long-term culture, and more closely replicate the 3D extracellular matrix (ECM) required for tissue engineering purposes, a biocompatible hydrogel, such as alginate, can be used for encapsulation.
Accordingly, we focused on converting droplets into hydrogels by ionically cross-linking particles but, in doing so, encountered further challenges. Forming hydrogel within a microfluidic platform is a delicate process. Two major problems that currently persist are irregular droplet production and clogging of the microchannels. Additionally, the use of existing gelling techniques such as a pH change and UV light irradiation is detrimental to cells resulting in poor cell viability.
To address these common challenges, we invented CLEX. CLEX, which stands for competitive ligand exchange crosslinking, is a new microchannel compatible and cell-friendly method to control the gelation kinetics of the crosslinking reaction. The resulting cell-laden alginate hydrogel microbeads are homogenous and monodisperse while also offering excellent cytocompatibility. When tested across a variety of cell types, including mammalian cells, bacteria, and other microorganisms, CLEX provides long-term cell viabilities constantly in the range of 95% and above (Håti et al 2016), which is far better than other methods.
A new plug-and-play hydrogel cell encapsulation system
Our partnership with Sphere Fluidics now enables us to combine our hydrogel technology with premium microfluidic systems and consumables to provide a plug-and-play system for working with 3D hydrogel matrices, culminating in the CYTRIX Microfluidic Hydrogel Kit. Alongside its superior cell encapsulation capabilities, the CYTRIX Microfluidic Hydrogel Kit is quick and easy to use compared to other setups and doesn't require any heating elements, pH changes, or additional steps that disrupt the workflow.
When using the kit, researchers simply add their cell suspension to the pre-gel solution and run their experiment with the Pico-Gen™ double aqueous chip and oil-based Pico-Surf™ surfactant to generate cell-laden hydrogel microbeads. After rinsing to remove the surfactant, users end up with a suspension of encapsulated cells in gel beads for further analysis. Additionally, the non-covalent nature of the CLEX hydrogels renders the gelation process reversible, allowing the release of the entrapped cells if desired.
The CYTRIX Microfluidic Hydrogel Kit solves some of the critical challenges in tissue engineering, including working at a single cell level and making microstructures that can be used as the building blocks to create tissues layer-by-layer. The collaboration with Sphere Fluidics also brings our technology to new application areas exploring the potential of 3D hydrogel matrices. It is designed as a versatile, ready-to-use solution, which can be optimized for any type of 3D cell encapsulation. The ability of the polymer to be functionalised allows adaptation to application-specific needs. Beyond tissue engineering, applications for this technology include cell line development, antibody discovery, immuno-oncology, and single-cell omics.
Ongoing and future developments in the field
We also have additional kits in the pipeline, such as a specific kit for stem cells, that will potentially further extend the scope of our technology. Beyond kits, we envision offering various integrated solutions that researchers can use with Cyto-Mine®, including multi-nozzle devices that encapsulate cells at even faster rates in the not too distant future. Circling back to our regenerative medicine focus, these capabilities would enable researchers building tissues and organs to significantly increase production throughput.
In the long run, our vision for the microfluidic field is that it will become more commonplace and mainstream in a variety of applications. The extensive advancements over the past decades have allowed microfluidics to evolve from esoteric research to a widespread research tool, and now to a standardized industrial device for clinical applications and pharmaceutical development. It is a fascinating time for the field because we are at a stage where we have robust workflows to analyze cell biology at the single cell level, and the technology has matured to the point of becoming a commercial instrument. It inspires and motivates us to be a part of the ongoing research and development processes contributing to this momentum and driving additional growth in microfluidics.