Bioartificial pancreas: alternative supply of insulin-secreting cells

Intelligent Surfaces for Cell and Tissue Delivery

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.

Tissue-culture surfaces with mixtures of aminated and fluorinated functional groups. Part 2. Growth and function of transgenic rat insulinoma cells (betaG I/17)

Interactions of transplantable cells with synthetic polymers can influence the function of biohybrid artificial organs. This study explored growth and secretion of human insulin by betaG I/17 cells cultured on surfaces bearing diamine groups (N2), trifluoropropyl groups (F3) and mixtures of the two. Cells cultured on high-F3 and high-N2 surfaces spread well, grew rapidly and produced >1.8 mol lactate per mol glucose consumed, closely resembling cells grown on the permissive control, glass. On one mixed surface, with a molar ratio of 33 N2 groups:67 F3 groups, cells had a lower lactate/glucose ratio, adopted a rounded form, grew slowly and were quick to form emergent aggregates, similar to cultures on the inhibitory control, untreated polystyrene. Cultures on surfaces with higher F3 content secreted the most insulin and, in the case of the highest-F3 surface, showed improved responsiveness to secretagogues. Hormone secretion was roughly 50% greater when cells were grown on F3 surfaces conditioned by earlier cultures of betaG I/17. Incubation of conditioned surfaces with high concentrations of a polyclonal anti-laminin serum prior to re-plating partially abolished this improvement in secretory function. Polymers bearing trifluoropropyl groups appear to be attractive candidates for use in the artificial endocrine pancreas. Surface coatings that include laminin might promote function of transgenic insulinoma cells in vitro and in vivo.