Computational design of in vivo biomarkers

Fluorescent semiconductor nanocrystals (or quantum dots) are very promising agents for bioimaging applications because their optical properties are superior compared to those of conventional organic dyes. However, not all the properties of these quantum dots suit the stringent criteria of in vivo applications, i.e. their employment in living organisms that might be of importance in therapy and medicine. In our review, we first summarize the properties of an 'ideal' biomarker needed for in vivo applications. Despite recent efforts, no such hand-made fluorescent quantum dot exists that may be considered as 'ideal' in this respect. We propose that ab initio atomistic simulations with predictive power can be used to design 'ideal' in vivo fluorescent semiconductor nanoparticles. We briefly review such ab initio methods that can be applied to calculate the electronic and optical properties of very small nanocrystals, with extra emphasis on density functional theory (DFT) and time-dependent DFT which are the most suitable approaches for the description of these systems. Finally, we present our recent results on this topic where we investigated the applicability of nanodiamonds and silicon carbide nanocrystals for in vivo bioimaging.