In-vitro characterization of microencapsulated microtissue viability

Abstract

With the rising occurrence and frequency of Type 1 Diabetes Mellitus (T1DM) together with its complications, T1DM poses a burden on paediatric patients and their families. Although islet transplantation is an alternative treatment of T1DM without the excessive need of exogenous insulin therapy which is the typical method of treatment, it still has its restrictions such as the lack of donors due to the need of adequate dose of islets, long term immunosuppressive therapy and insulin resistance. The transplantation of immuno-isolated islets is a potential approach to treat T1DM as it enables the transplanted islets to produce insulin to restore normoglycemia without the need of immunosuppression. However, the encapsulated islets experience inadequate oxygen delivery as there is a lack of vasculature at the transplant location resulting in hypoxia and the death of tissues at the islet core which results in the eventual loss of insulin independence in the long term. Previously, unencapsulated toroid microtissues have exhibited enhanced cellular viability and metabolic activity compared to unencapsulated spheroid microtissues probably due to increased surface-to-volume ratio of toroidal geometry. However, the viability of microtissues encapsulated in microcapsules remains unexplored before. In this study, the viability of encapsulated microtissues were quantitatively evaluated using trypan blue exclusion assay following exposure of microtissue-encapsulating microcapsules to Ethylenediaminetetraacetic acid (EDTA) solution. We demonstrated that the retrieved number of cells per microtissue after exposure to EDTA solution for 0.5 minute was higher than that after EDTA treatment for 1 and 2 minutes. Furthermore, encapsulated toroid microtissues exhibited higher average cellular viability than encapsulated spheroid microtissues in a microcapsule system. Future study on characterizing viability of toroid and spheroid microtissues using non-proliferative primary cell source after prolonged period of culture could be useful in investigating the effect of microtissue geometry on cellular viability in a long-term.