Nanostructure‐Dependent Ratiometric NIR Fluorescence Enabled by Ordered Dye Aggregation

Abstract Nanocarriers incorporating therapeutic and imaging agents within a single nanostructure are emerging tools for drug development and treatment planning. Additional information can be provided using activatable fluorescence that dynamically reports nanocarrier disruption and drug release. Dual‐wavelength activation encodes a unique fluorescence signal for each nanocarrier state, enabling use of ratiometric imaging to measure the proportion of intact and disrupted nanocarriers within tissues. Here we investigate dual‐wavelength activation using a single dye whose optical properties are intricately linked to the nanocarrier structure. Natural bacteriochlorophyll incorporated within a compact lipoprotein nanocarrier forms ordered dye aggregates with red‐shifted fluorescence emission from 765 nm to 825 nm. We demonstrate that bacteriochlorophyll‐ordered aggregation is a feasible strategy to distinguish intact and disrupted theranostic nanocarriers by ratiometric fluorescence imaging.