UPM Biomedicals produces a highly biocompatible hydrogel, GrowDex®, that makes it possible for researchers worldwide to focus on developing active pharmaceutical ingredients with a focus on the human application while using less animal material. In order for the cells to form tiny organs (organoids and spheroids), they need a fibrous environment that mimics the extracellular matrix of our body. Normally, animal materials are used to create these 3D culture conditions. GrowDex is a ready-to-use hydrogel which is obtained from birch wood and therefore contains no material of animal or human origin.
The challenge: Dispensing a viscous hydrogel with extreme accuracy using a precise valve
GrowDex is thermally stable at temperatures from 0 °C to over 100 °C, making it ideal for high-throughput automation and screening. GrowDex is a shear-thinning material, which means that its viscosity changes with the force exerted on the material - it is liquid at high dispensing pressure, but as soon as the pressure is released, the material's solidity and viscosity increase again. As the cellulose nanofibers inside the material do not cross-link, but only intertwine, the material is a genuine hydrogel. This requires special attention with regard to controlling the pressure generated in the dispensing system.
UPM Biomedicals therefore approached the experts at the Festo LifeTech Application Center with a request to carry out a feasibility analysis for the automated dispensing of a shear-thinning hydrogel. The aim was to reliably achieve the specified CV (coefficient of variation) values for two target volumes, 25 µl and 100 µl. These volumes are typical for dispensing in 96-well and 384-well microwell plates.
"We often dispense customized liquids. When I first saw the GrowDex hydrogel in the syringes, I knew that it would not be easy to dispense it, even when it is diluted. But I also know that our system offers a lot of possibilities for finding the right solution," says Festo Application Engineer Manuel Rausch.
The solution: Varying and optimizing products and parameters
When it comes to automated liquid handling, Festo relies on the pressure-controlled dispensing method. Parameters such as pressure and opening times can be flexibly adapted to the properties of the liquid. For the test, both the Festo products used and the process parameters were varied, such as media-separated valves, needles, pressures and valve opening times.
First, the GrowDex or GrowDex-T hydrogels to be tested were manually diluted with the DMEM cell culture medium and filled into a glass bottle with a lid. A pressure-vacuum generator (PGVA-1) was used to pressurize the bottle via a connecting tube. The VAEM-V valve control module precisely controls the VYKB-F12 media-separated valve to dispense the displaced hydrogel mixture into a target vessel. The dispensed quantity was recorded gravimetrically with a pair of scales and used to evaluate the CV value.
The VYKB-F12 valve and a needle with a large internal diameter proved to be the best solution for keeping the flow resistance low. The chosen design also made it possible to use the compact pressure/vacuum generator PGVA-1, making a compressed air connection in the laboratory superfluous.
The result: The perfect dispensing process for GrowDex hydrogels
Festo's application engineers developed a set-up of components that enabled GrowDex to be dispensed at a concentration of 0.75% and GrowDex-T at a concentration of 0.5%, each mixed with DMEM at a ratio of 1:1. The CV values were within the specified tolerance.
UPM can now be confident that its GrowDex hydrogels can be dispensed automatically in customized systems when using a specific technical set-up. "Automation can now replace another manual step and makes 3D cell culture more reliable and faster," says a delighted Piia Mikkonen from UPM.
This is our joint step towards reducing the use of animal material while improving the reliability and repeatability of 3D culture results. Whether in drug screening or regenerative medicine, customized automated systems will play an important role in meeting regulatory requirements.
About the authors
Manuel Rausch
Application Engineer
Festo Germany
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Vesa Tomukorpi
Business Driver
Festo Finland
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Global, solution-oriented and networked: LifeTech Application Engineering
The LifeTech Application Engineering team at Festo offers customers worldwide support with their search for solutions; they carry out feasibility studies and parameter optimizations, training, prototype construction, commissioning and installations and also clarify the requirements of customers with new enquiries. The application engineers have extensive experience in the areas of liquid handling, motion and liquid control.
