"Theranostics are a combination of therapeutic and diagnostic strategies. Generally, this can be seen in two approaches. On the one hand are the so-called 'companion diagnostics', meaning diagnostics that accompany therapies," explains Dr. Sofia Dembski, Head of the Department of Theranostics at the Fraunhofer Institute for Silicate Research ISC in Würzburg, Germany. In this case, the physician reviews the effects of a treatment already during the course of therapy and is able to optimize it based on measured values for example. "On the other hand, there are also in situ diagnostics. Here, therapy and diagnostics are combined in one tool. This is an active component, nanoparticles, for example, that can be shown in the body by using various imaging techniques on the one hand while they are also transporting an active ingredient on the other."
These nanoparticles differ drastically, even if they generally serve a "theranostic" function. They can have different geometric shapes, such as rods, spheres or octahedrons for instance. Even if they are tools, we cannot clearly state to what extent form always follows function. "Every particle system contains too many parameters that interact," explains Dembski. "These combinations are very complex and we cannot always say that one specific factor alone influences the function of the particles."
If anything, the particle size and their composition appear to be important for the effect of particles in the body and the contrast in imaging techniques. The Fraunhofer ISC develops particles that consist of inorganic or hybrid (organic-inorganic) materials. Surface modifications also play a role in delivering the active ingredient to the targeted site.
The researchers in Würzburg study particles for various imaging techniques such as magnetic resonance imaging (MRI), fluorescence-based methods, computed tomography (CT) and magnetic particle imaging (MPI) - a method that is still in the development stage.
In this case and in the spirit of combining processes, they are not searching for a solution for a single method but rather for particles that can be used with multiple imaging techniques. The advantage of this approach is obvious if you see it from the perspective of radiology and nuclear medicine: it means less exposure to chemical agents for patients since they would otherwise be given a different contrast agent before every examination. "This is also a trend with several equipment manufacturers who are already developing combination products such as combined CT and MRI images or PET and MRI imaging," says Dembski. "There would subsequently only be one single contrast agent for these types of devices."