Development of a selective cell capture and release assay: impact of clustered RGD ligands†
There is a growing interest in isolating tumor cells from biological samples. Considering that circulating tumor cells can be rare in blood, it appears challenging to capture these cells onto a surface with high selectivity and sensitivity. In the present paper, we describe the design of functionalized surfaces aimed at selectively capturing tumor cells by using an RGD peptide ligand with either a tetrameric or a monomeric presentation. β-Cyclodextrin-coated self-assembled monolayers were used as platforms for the binding of RGD ligands endowed with a redox ferrocene cluster. The dissociation of the inclusion complex on the surface accounts for the release of the captured cells upon the electrochemical oxidation of ferrocene. For this purpose, we determined suitable RGD densities for both monovalent and tetravalent ligand presentations. The results indicate that the clustered RGD architecture efficiently improves selective cell capture at a very low RGD surface density (∼10 RGD per μm2) compared to the monovalent presentation (∼1000 RGD per μm2).