Folate receptor-targeted nanoprobes for molecular imaging of cancer: Friend or foe?

•Folate receptors are overexpressed on most cancer cells, with a very high affinity for folate.•Folate receptor-targeted nanoprobes have been successfully used in pre-clinical models to image cancer tissue with multiple modalities.•Challenges for clinical translation include the non-desired uptake of particles in the liver, spleen, and kidney.