Indocyanine Green‐Based Test‐Platform With Tunable Contrast for Optoacoustic and Fluorescence Lifetime Visualization

ABSTRACT Multimodal approaches to diagnostics and therapy have lately attracted considerable attention. A promising combination of fluorescence lifetime and optoacoustic imaging offers complementary advantages: fluorescence signals provide metabolic tissue information, while optoacoustic data assess oxygen status and vascularization. This combination is particularly valuable for the in vivo differentiation of normal and pathological tissues, including cancer. Therefore, a stable platform for testing this equipment is crucial. Indocyanine Green (ICG), a clinically approved near‐infrared fluorescent dye, has limited optoacoustic imaging capabilities in its monomeric form. However, converting ICG into J‐aggregates (IJAs) enhances optoacoustic performance by decreasing fluorescence quantum yield and transferring ICG monomers/dimers to nanoparticles. This study evaluates the optical properties of tissue phantoms containing various ratios of vaterite nanoparticles with ICG and IJA for further use in fluorescence lifetime imaging microscopy (FLIM) and optoacoustic tomography. Loading ICG and IJA into vaterite allows for fine‐tuning of FLIM and OA contrast based on the nanoparticles concentrations. This approach facilitates testing of a novel imaging system combining FLIM and OA modalities, opening up new avenues for preclinical and clinical in vivo diagnostics.