Chemyx: Sustained-Release Therapeutic Carriers - The Microencapsulation of Cells

 

Microencapsulation: Agents & Applications

 

In culture and in vivo cell-microencapsulation has been accomplished using a person’s own cells (autologous), a donor’s cells (allogeneic), or another species’ cells (xenogeneic) for the immuno-protected and continuous release of the bioactive agents they produce. The semi-permeable membrane required for encapsulation has largely been of the hydrogel sort and polysaccharide-based, using agarose, alginate, chitosan, gelatin, collagen, among others, of which alginate is most-readily available and therefore widely used.^1,2

 

Depending on the intended therapeutic use, various degrees of porosity may be desired. For example, where immuno-protection is required (e.g., endocrine diseases like diabetes, anemia), the encapsulated cells being transplanted should have a matrix porosity that spares host antibody and/or T-cell attack while allowing for the passage of signaling molecules required for the sustained remedial response. 1 In the case of restorative applications, like tissue regeneration, a matrix susceptible to degradation may be advantageous, in that, once the cells are released, they’re free to work to replace the impaired host extracellular matrix.^₁ Of course, regardless of the end goal, oxygen, cell nutrients, and metabolites required for cell viability should be allowed to diffuse unhindered for optimal response. This often requires the generation of different concentration gradients to accommodate both the innermost and outermost cells of the capsule.^1,2

 

How can a syringe pump help?

 

Hydrogel matrices are processed and molded with the specific transport requirements in mind. The process typically involves gravitational dripping, where the hydrogel precursor material of choice and cells-of- interest are extruded through a small cylinder through which they fall freely into an appropriate hardening bath once the right mass is reached.¹ Monodispersion of the encapsulated products and maintenance of cell viability throughout requires careful control of their delivery and execution.² Once cumbersome and difficult, user-friendly syringe-pump microfluidic platforms allow for highly-precise operation by non-experts. Furthermore, microchannel chip approaches based on flow intensity for encapsulation and droplet formation can also be supported by the appropriate pressure pump, allowing for continuous encapsulation while minimizing human intervention right from the outset.