Optoacoustic and fluorescence lifetime visualization based on chlorophyll-loaded particles in phantoms
Timofei Torokhov1,2, Sergei Perkov1,3 Julijana Cvjetinovic1, Alexey Kurnikov4, Maksim Mokrousov1,5, Igor Sergeev1, Arkady Abdurashitov6,7, Pavel Subochev4, Vladislav Shcheslavskiy8,9, Dmitry Gorin1,3; 1Laboratory of Biophotonics, Center for Photonic Science and Engineering, Skolkovo Institute of Science and Technology, Moscow, Russia; 2Prokhorov General Physics Institute of the Russian Academy of Sciences, Moscow, Russia; 3Laboratory of Digital Biophotonics, Central University, Moscow, Russia; 4Institute of Applied Physics of the Russian Academy of Sciences, Nizhny Novgorod, Russia; 5Moscow Institute of Physics and Technology, Dolgoprudny, Russia; 6Center for Bio- and Medical Technologies, Skolkovo Institute of Science and Technology, Moscow, Russia; 7Life Improvement by Future Technologies Center, Moscow, Russia; 8Institute of Experimental Oncology and Biomedical Technologies, Privolzhsky Research Medical University, Nizhny Novgorod, Russia; 9Becker&Hickl GmbH, Berlin, Germany
Abstract
Optoacoustic imaging (OA) and fluorescence lifetime imaging microscopy (FLIM) are complementary imaging modalities that provide deep functional imaging and molecular microenvironment information, respectively. The development of integrated OA–FLIM systems requires tissue-mimicking phantoms with reproducible optical, acoustic, and fluorescence lifetime properties.
Here, we present a bimodal phantom based on chlorophyll-loaded vaterite microparticles embedded in agarose gel. Chlorophyll was extracted from spinach leaves, encapsulated into porous vaterite particles (3–5 μm) using freeze-induced loading. The phantoms were characterized by absorption and fluorescence spectroscopy, scanning electron microscopy, fluorescence microscopy, fluorescence lifetime imaging (375 nm excitation), and multispectral optoacoustic tomography (660–760 nm).
Spectroscopy and microscopy confirmed successful chlorophyll encapsulation, preservation of fluorescence properties, and homogeneous particle distribution with negligible pigment leakage into the gel matrix. FLIM measurements revealed fluorescence localized within particle clusters, with concentration-dependent lifetime distributions: increasing particle concentration reduced the dominant fluorescence lifetime from approximately 970 ps to 760 ps, consistent with concentration quenching and enhanced intermolecular energy transfer. OA imaging demonstrated a strong absorption maximum at ~675 nm and a more than twofold increase in signal amplitude for the higher-concentration phantom, exceeding linear scaling due to particle aggregation and enhanced non-radiative relaxation.
The proposed chlorophyll-based phantom provides reproducible and tunable contrast for both OA and FLIM. This platform offers a simple and cost-effective solution for calibration, validation, and cross-platform comparison of combined OA–FLIM imaging systems.
Acknowledgement: This work was supported by the Russian Science Foundation (Grant No. 24-19-00618).
Speaker
Timothy Torokhov
Prokhorov General Physics Institute of the Russian Academy of Sciences, Skolkovo Institute of Science and Technology
Russian Federation
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