Towards a medically approved technology for alginate-based microcapsules allowing long-term immunoisolated transplantation

Abstract

The concept of encapsulated-cell therapy is very appealing, but in practice a great deal of technology and know-how is needed for the production of long-term functional transplants. Alginate is one of the most promising biomaterials for immunoisolation of allogeneic and xenogeneic cells and tissues (such as Langerhans islets). Although great advances in alginate-based cell encapsulation have been reported, several improvements need to be made before routine clinical applications can be considered. Among these is the production of purified alginates with consistently high transplantation-grade quality. This depends to a great extent on the purity of the input algal source as well as on the development of alginate extraction and purification processes that can be validated. A key engineering challenge in designing immunoisolating alginate-based microcapsules is that of maintaining unimpeded exchange of nutrients, oxygen and therapeutic factors (released by the encapsulated cells), while simultaneously avoiding swelling and subsequent rupture of the microcapsules. This requires the development of efficient, validated and well-documented technology for cross-linking alginates with divalent cations. Clinical applications also require validated technology for long-term cryopreservation of encapsulated cells to maintaining a product inventory in order to meet end-user demands. As shown here these demands could be met by the development of novel, validated technologies for production of transplantation-grade alginate and microcapsule engineering and storage. The advances in alginate-based therapy are demonstrated by transplantation of encapsulated rat and human islet grafts that functioned properly for about 1 year in diabetic mice.

A case report on the use of sustained release platelet-rich plasma for the treatment of chronic pressure ulcers

“…18 Alginate is a biomaterial, typically derived from seaweed or algae, which is commonly used as a wound dressing in the treatment of pressure ulcers and has a long history of biocompatibility. 1,19,20 The purpose of this report is to demonstrate, through a small three-person case study, the results of using CaCl 2 -activated PRP and PRP containing alginate beads as a delivery vehicle for the sustained release of PRP-derived growth factors and cytokines to stimulate healing in stalled pressure ulcers where conventional treatment methods have failed.…”

Isolation of monoclonal microcarriers colonized by fluorescent E. coli

“…miniature gel-microcarriers (7)(8)(9)(10)(11). These microcarriers readily allow exchange of nutrients or reactants through the gelstructure but are well suited to retain cells.…”

Encapsulation technologies in beta cell replacement therapies for Type 1 diabetes

“…A majority of macroencapsulation devices [32][33][34][35][36][37][38][39][40] that have been evaluated for use in islet and stem cell transplantation are implanted at extravascular sites. This is because recipients do not suffer the hemorrhagic complications seen with implantable intravascular devices.…”