Optical phantoms containing ICG and IJA encapsulated in vaterites for optoacoustic and fluorescence lifetime visualization

Abstract

The development of multimodal imaging techniques for diagnostics and therapy has attracted significant attention in recent decades [1–3]. A particularly powerful combination is that of fluorescence lifetime imaging (FLIM) and optoacoustic (OA) tomography, as these modalities offer complementary data: FLIM can reveal metabolic activity [4,5], while OA can provide detailed information on oxygen levels and tissue vascularization [6,7]. Together, these modalities hold significant promise for accurately distinguishing between healthy and pathological tissues. Testing such setups on in vivo is difficult due to heterogenous and complex internal structure of biological tissues, so phantoms with known optical properties are routinely used in such cases as testing and calibration of new setups [8,9].
To provide fluorescent and optoacoustic contrast clinically approved near-infrared dye, Indocyanine Green (ICG) was chosen. Monomeric ICG is a versatile fluorescent agent [10], but it performs poorly in OA imaging due to limited depth penetration and detectability [11]. However, transforming ICG into its J-aggregate form (IJA) drastically improves its OA performance by reducing its fluorescence quantum yield and assembling it into nanoparticles [12,13]. However, both forms suffer from limited stability. To enhance the dyes stability, both monomers and J-aggregates were loaded into vaterite particles via freezing-induced loading (FIL).
In this work, phantoms containing variable ratios of monomeric ICG and IJA (with same total dye concentration of 15 μM) were fabricated and imaged using TriTom setup that combines optoacoustic and fluorescence tomography, IVIS Spectrum CT setup that provides fluorescence imaging, and a custom made FLIM setup.

This work was supported by the Russian Science Foundation (RSF), Grant № 24-19-00618
 
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Speaker

Timothy Torokhov
Prokhorov General Physics Institute, Skolkovo Institute of Science and Technology
Russian Federation

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