The use of nanoparticles in drug delivery offers key advantages: they can enable targeted drug delivery, protect active ingredients from premature degradation, extend their duration of action in the body and reduce side effects. However, as soon as nanoparticles come into contact with blood, proteins from the blood adsorb onto their surface—forming a so-called protein corona. This corona influences whether the particles are taken up by cells, how they distribute in the body or whether the immune system recognizes and attacks them.