Scheme 1. (A) Chemical Structures of amp-inert¹¹ and amp-TCO, π-Conjugated Small Molecules, Which Self Assemble into SMNPs. (B) Two-Step Radiolabeling Strategy Starts with Chelation of the Radioisotope to the Tetrazine-DOTA Derivative Followed by (C) Conjugation to the SMNP Co-Self-Assembled from amp-inert and amp-TCO.