Novel radioisotope-based nanomedical approaches

Radioisotope therapy of cancer is on the rise applying mainly β-emitting radionuclides. However, due to exposure of healthy tissues, the maximum achievable radiation dose with these is limited. Auger-electron emitters (AEs) represent a promising alternative because of their mode of decay within a short nanometer range. The challenge is that their therapeutic efficacy relies on a close vicinity to DNA. To overcome this and to minimize toxicity, the construction of smart nanomedical devices is required, which ascertain tumor cell targeting with succeeding cellular uptake and nuclear translocation. In this review we describe the potential of AEs with focus on their delivery down to the DNA level and their cellular effects. Reported efforts comprise different tumor-targeting strategies, including the use of antibodies or peptides with nuclear localizing sequences. Recently, attention has shifted to various nanoparticle formats for overcoming delivery problems. To this end, these approaches have mostly been tested in cell lines in vitro applying AEs more suited for imaging than therapy. This defines a demand for nanomedical formulations with documented in vivo activity, using AEs selected for their therapeutic potential to come closer to real clinical settings.