Inside the Dolomite Labs: Alginate bead formation using FluoSurf
Alginate is an anionic polysaccharide extracted from brown algae commonly used in biomedical, bioprocessing and pharmaceutical applications. Its mild ionic gelation makes it an attractive hydrogel for the encapsulation of cells and tissue engineering. So, this month the Dolomite team has been looking at producing alginate beads using microfluidics! Conventionally, extrusion method is used to produce large alginate beads (500 µm) in a calcium chloride bath however, there is poor control over bead size and shape. This is due to the viscous nature of the alginate which proves challenging in pinching smaller drops resulting in a large tear shaped beads being formed.
Figure 1, a) 3D pore 100 µm droplet chip junction, b) 80 µm, c) 100 µm alginate beads.
The Dolomite Team is using microfluidics to produce small (80-120 µm) alginate beads suitable for cell encapsulation. A 2 % alginate solution was dissolved in water overnight with subsequent addition of Ca-EDTA. For the oil phase, 1 % Fluosurf in HFE 7500 was used with 0.05 % acetic acid to release the chelated calcium in the Ca-EDTA complex and allow alginate crosslinking from within. Both solutions were introduced into a 100 µm 3D pore fluorophilic single junction chip (figure 1a) to form spherical monodispersed beads. Depending on flow rates (Qd 16 µlmin-1 Qc 10 µlmin-1 and Qd 10 µlmin-1 Qc 18 µlmin-1) 80 µm (figure 1b) and 100 µm (figure 1c) alginate beads were produced respectively.
If you are interested in producing alginate beads for your applications, please contact us at email@example.com, and keep an eye out for our alginate bead application note showing cell encapsulation, which we will be releasing onto the website in the near future.