Single-wavelength photoacoustic tomography for in vivo assessment of polyelectrolyte carrier delivery
Oksana A. Mayorova1, Polina A. Demina1, Natalia A. Shushunova1, Yulia I. Svenskaya1, Ekaterina S. Prikhozhdenko2, Svetlana A. Shevtsova1, Ilia O. Kozhevnikov1, Daniil N. Bratashov1,2; 1Saratov State University, Saratov, Russia; 2Moscow Institute of Physics and Technology, Dolgoprudnyy, Russia
Abstract
Photoacoustic tomography (PAT) is a non‑invasive imaging modality that enables tracking of contrast agents and drug carriers in biological tissues at depths of up to several centimetres. However, in vivo monitoring of targeted drug delivery remains constrained by the lack of reliable approaches for separating the signal from the administered agent from that of endogenous chromophores, particularly when operating at a single wavelength – a critical requirement for the development of compact instrumentation. The aim of this work was to evaluate the capability of PAT for monitoring transdermal delivery of polyelectrolyte microcapsules loaded with bovine serum albumin labelled with Cy7 dye in a BALB/c mouse model. Three‑dimensional photoacoustic images of animals were acquired before and after ultrasonic administration of the capsules (0.5 W/cm², 1 MHz, 10 min) at a wavelength of 750 nm, close to the absorption peak of Cy7. Post‑injection images revealed a marked increase in signal intensity in the dorsal region, with the appearance of local bright areas corresponding to carrier accumulations, whereas in control animals only large blood vessels and gastrointestinal contents were visualised. Intensity histograms did not show bimodal separation, indicating an overlay of the dye signal on background tissue absorption; nevertheless, pronounced distribution tails and the rise in mean intensity allowed reliable identification of capsule localisation without spectral unmixing. The instrument resolution (~100 µm) was insufficient for visualising individual particles, yet the integrated pattern provided reliable information on carrier accumulation zones. The capsules, stabilised by polymer bilayers, are expected to degrade slowly, offering the possibility of long‑term monitoring of drug release. Thus, single‑wavelength PAT proves effective for non‑invasive monitoring of transdermal delivery, overcoming the limitations of conventional ex vivo methods and biopsies, and may serve as a basis for developing affordable photoacoustic systems for clinical applications.
The study was supported by the Russian Science Foundation, grant No. 25‑19‑00828,
https://rscf.ru/project/25‑19‑00828/.
Speaker
Oksana A. Mayorova
Saratov State University
Russia
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