CUPIDO since its beginning has worked to develop synergistic targeting techniques that could maximize nanoparticle delivery to the heart. One of the options considered by the project is the functionalization of the CaP nanoparticles with aptamers, which should enhance the internalization into myocardial cells (http://www.cupidoproject.eu/guidance-to-the-heart/)
Aptamers, short single stranded synthetic oligonucleotide, can fold into complex tertiary structures and thus are able to bind with high affinity to a specific target receptor on the surface of the target cells. Furthermore, compared to other targeting ligands and monoclonal antibodies, they show many additional advantages, such as low toxicity, high specificity, and superior stability in biological fluids. Based on these premises, in CUPIDO we first, generated a novel internalizing aptamer targeting cardiac cells, and then we efficiently functionalized the surface of the CaP nanoparticles with such aptamer. The combo aptamer-CaPs were then tested in vitro and in vivo.
After the success of the in vitro validation, CNR extended the analysis to several in vivo assays to assess whether, within the whole myocardial cell population, the presence of the aptamer on the CaP nanoparticle surface enhances the targeting towards cardiomyocytes compared to other myocardial cells. One of the assays is the FACS ( Fluorescence Activated Cell Sorting) analysis of single cells isolated from the whole heart of treated adult mice, as described already in this protocol (Transl Medicine 2018). Results showed a significantly increased accumulation in cardiomyocytes in mice treated with CaP-aptamer when compared to mice treated with standard CaP nanoparticles, thus providing the in vivo evidence that the novel aptamer is indeed effective in improving the targeting of CaPs towards the cardiac cells.