WEB Biodegradable microbeads for stem cells amplification
The adoption of auto- or xeno- grafts is frequently used in surgery, but this approach raises several concerns in terms of risk of rejection, infection, availability, limited amount or weakening of tissue. For all these reasons, regenerative medicine becomes more attractive, allowing to restore or replace damaged tissues and organs by diseases or trauma.
The daily application of this new clinical strategy imposes to solve several challenges. One of them is linked to the low amount of stem cells (~40,000) which can typically be recovered from a human donor compared to the needs required in clinical therapy (500 million of stem needed to achieve efficient therapy). This high dose of stem cells is explained due to their rapid diffusion from the injection site and their low survival rate upon implantation. The adoption of biocompatible and biodegradable microcarriers to amplify stem cells in vitro should allow to answer these two main issues. Stem cells can be already pre-cultured on these microcarriers before proceeding to their local injection within the injury site. This approach combines the following main advantages : i) a large surface-to-volume ratio promoting cell expansion, ii) an easiness for parenteral administration without needs to detach MSCs, a main source for low survival rate iii) biocompatibility and biodegradability enhancing tissue reconstruction.
Our microcarriers have been designed by using an emulsion/evaporation process (raw microbeads). The size of the microcarriers has been easily adjusted by playing on the viscosity of the oil phase of the emulsion.
To promote cell adhesion and proliferation, microbeads have been functionalized by physical deposition of polyelectrolytes. The efficacy and the stability of different coatings have been demonstrated using fluorescent polyelectrolytes. In order to adjust the thickness, stability and surface density of this coating, different polymers have been assessed differing in terms of macromolecular characteristics, i.e. molecular weight, charge density and chain mobility. Indeed, all these surface features are well known to influence the cellular behavior, including their mobility, gene expression or their cytoskeleton reorganization. After sterilization, biocompatibility of these microbeads has been analyzed in vitro using cytotoxicity tests (MTT and Hoechst nuclear labeling).
Cell detachment from these microcarriers has been also investigated as an alternative strategy.
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