Evaluation of different RGD ligand densities in the development of cell-based drug delivery systems

Background: The inclusion of the tripeptide Arg-Gly-Asp (RGD) in otherwise inert biomaterials employed for cell encapsulation has been observed to be an effective strategy to provide the immobilized cells with a more suitable microenvironment.Purpose: The objective of this study was to determine the impact of different RGD densities on the behavior of baby hamster kidney (BHK) fibroblasts able to secrete vascular endothelial growth factor (VEGF) encapsulated in alginate microcapsules.Methods: Alginate was modified by varying the concentration of RGD peptides in the coupling reaction. After obtaining four different types of alginate, cells were encapsulated in alginate-poly-l-lysine-alginate (APA) microcapsules.Results and discussion: The results obtained after viability, cell proliferation and VEGF secretion assays showed that the inclusion of RGD in alginate enhances the functionality of immobilized cells, obtaining the highest values with the intermediate RGD density.Conclusion: These results put in evidence that alginate modification influences the behavior of immobilized cells but even more that the employed density of the tripeptide is of crucial importance, obtaining in some cases even excessive activity of the encapsulated cells.