Alginate-Based Cell Microencapsulation for Tissue Engineering and Regenerative Medicine

Abstract

Increasing numbers of requests for transplantable organs and their scarcity has led to a pressing need to find alternative solutions to standard transplantation. An appealing but challenging proposal came from the fields of tissue engineering and regenerative medicine, the purpose of which is to build tissues/organs from scratch in the laboratory and use them as either permanent substitutes for direct implantation into the patient's body, or as temporary substitutes to bridge patients until organ regeneration or transplantation. Using bioartificial constructs requires administration of immunosuppressant therapies to prevent rejection by the recipient. Microencapsulation has been identified as promising technology for immunoisolating biological materials from immune system attacks by the patient. It is based on entrapping cellular material within a spherical semipermeable polymeric scaffold. This latter defines the boundary between the internal native-like environment and the external "aggressive" one. The scaffold thus acts like a selective filter that makes possible an appropriate supply of nutrients and oxygen to the cellular constructs, while blocking the passage for adverse molecules. Alginate, which is a natural polymer, is the main biomaterial used in this context. Its excellent properties and mild gelation ability provide suitable conditions for supporting viability and preserving the functionalities of the cellular- engineered constructs over long periods. Although much remains to be done before bringing microencapsulated constructs into clinical practice, an increasing number of applications for alginate-based microencapsulation in numerous medical areas confirm the considerable potential for this technology in providing a cure for transplant in patients that excludes immunosuppressive therapies.

A Versatile Microencapsulation Platform for Hyaluronic Acid and Polyethylene Glycol

“…Current methods for cell microencapsulation are predominantly based on alginate spheres because of the quick gelation rate. 33,34 Other hydrogels utilized for microencapsulation involve oil-emulsion techniques, 13,35 which can have issues with toxicity to cells. Alternatively, our method, termed CSS, could be used for a wide variety of hydrogel materials and is compatible with standard, commercially available and GMP-ready equipment, and is minimally cytotoxic to islets.…”

One-step automated bioprinting-based method for cumulus-oocyte complex microencapsulation for 3D in vitro maturation

“…The liquid droplet lands in a beaker filled with a crosslinking solution whereupon it forms a hydrogel bead. In these microbeads, cells are enclosed in a 3D microenvironment with COC-related dimensions (about 1000 μm in radius) in a biopolymer whereby an adequate supply of oxygen and nutrients in the media as well as waste removal is guaranteed [ 55 , 56 ]. Fig 1 shows the spherical hydrogel generator Sphyga (A, B), the calcium-induced gelification (C) and the Sphyga set-up for microbead preparation (D-E).…”

Bioengineering Organs for Blood Detoxification

“…In addition, its relatively low cost and gelation capacity by divalent cations such as Ca 2+ [194] makes the process suitable for hepatocyte encapsulation. [151] Alginate is suitable for cell encapsulation because it has very limited inherent cell adhesion and cellular interaction (being a hydrophilic polymer, it promotes spheroid formation and thus enhances cell-cell interaction and hepatocyte functionality. [195] ) This however can be a disadvantage for tissue engineering applications as there is a lack of specific cellular signals promoting adherence or differentiation.…”