Controllable Self-Assembly of Peptide-Cyanine Conjugates In Vivo as Fine-Tunable Theranostics

The fabrication of functional assemblies with defined structures through controllable molecular packing under physiological conditions is challenging. Here, modularly designed peptide-cyanine conjugates that intracellularly self-assembly into 1D columnar superstructures with controlled cyanine aggregation were designed, and they exhibit distinct imaging or photothermal properties. The peptide backbone is cleaved by caspase-3/7 after entering the cells. Then the self-assembled residue, with a double cyanine substitution (Pr-2Cy), forms a P helical column in which H-aggregated cyanine dyes show 3.4-fold photothermal conversion efficiency compared to free ones. The self-assembled residue with a single cyanine substitution (Pr-1Cy) forms a loose column, in which cyanine dyes with undefined structure have a fluorescence quantum yield of up to 9.5 % (emission at 819 nm in H₂O). This work provides a simple way to modify in vivo self-assembled peptides with functional molecules for achieving desired bio-applications.