Cadherins as a tool to attach magnetic nanoparticles to the cell membrane

Abstract

Magnetic nanoparticles (MNPs) present the ability of generating heat when exposed to an alternating magnetic field (AMF). This property is being exploited in different fields, specially biomedicine and cancer treatment through magnetic hyperthermia. The possibility of attaching MNPs to the cell membrane would also enable its controlled and localized heating, allowing to broaden the knowledge regarding cell-nanoparticle interaction and to study the effect of localized heating on the membrane, and its possible applications in transfection and cell membrane biophysics studies. So far, different biomolecules have been used to vectorize nanoparticles, but there is no universal strategy to functionalize MNPs to target the cell membrane. Cadherins are great candidates to fulfil this aim, due to their attachment via homophilic interaction and their ubiquity in animal tissues. Functionalizing MNPs with cadherins would allow them to attach to the cadherins on the cell membrane in a Ca2+- and orientation-dependant manner. In addition, this superfamily of proteins plays a key role in cell-cell adhesion and cell development and is also crucial in cancer evolution. Therefore, targeting a specific member of the family would provide selectivity towards tumoral cells. In this work, 12-nm MNPs grafted with polyethylene glycol are functionalized with a nitrilotriacetic acid derivative (NTA), a molecule able to chelate Cu2+. Then, histidine tagged (His-tagged) recombinant cadherins are bound to the surface of the MNPs through chelation effect with the Cu2+. This functionalization strategy presents two main advantages: the control of the orientation of the cadherins on the MNP surface - essential to ensure an effective interaction within the small contact area of the MNP-cell interface -, and the straightforward adaptation of the protocol to any His-tagged protein. As a proof of concept, MNPs have been functionalized with different types of cadherins (such as a wild type E-cadherin or a mutated one) and incubated with different cell lines expressing or lacking these proteins to test the specificity of the system (i.e. MDCK and Balb/c).