CHAPTER 23:Intelligent Surfaces for Cell and Tissue Delivery
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Cell transplantation remains a powerful approach for promising numerous biomedical applications to promote tissue regeneration. Therefore, smart delivery systems of therapeutic cells, as well as therapeutic oligonucleotides and proteins, are required. Although cells have been conventionally delivered by direct injection to target sites, a number of clinical studies showed a limitation due to poor cell retention and survival at the sites, resulting in insufficient effect on tissue/organ repair. Therefore, at present, numerous delivery strategies have been developed, and a variety of polymeric materials play important roles. For example, encapsulation in semi-permeable membrane made from biocompatible polymers (e.g. alginate-poly(l-lysine)-alginate) allows xenograft islets to be delivered in vivo without immune suppression. With progress in tissue engineering, scaffold-based cell/tissue delivery reached the mainstream for regenerating damaged tissues. Various kinds of scaffolds have been fabricated from natural and synthetic polymers, such as collagen or poly(l-lactic-co-glycolic acid), and allowed to provide appropriate nutritional conditions and spatial organization for cell growth. Whereas these scaffolds produce reliable architectures to design cell/tissue delivery, scaffold-free cell/tissue delivery also has opened up a new class technology in the field of regenerative medicine. Thermo-responsive poly(N-isopropylacrylamide)-grafted surfaces allow one to fabricate tissue-like cell monolayers, “cell sheets”, and deliver the cell-dense tissue with associated extra-cellular matrix (ECM) to damaged sites without scaffold implantation. The chapter focuses on unique cell/tissue delivery techniques using the intelligent surfaces. This technology has already been applied to human clinical studies for tissue regeneration, and microfabricated thermo-responsive surfaces are further developing for delivering more complex tissue.