Valeryia S. Kachan

Background/Objectives: Nanoparticles have emerged as indispensable tools in modern biomedicine, enabling precise diagnostics, targeted therapy, and controlled drug delivery. Despite their rapid progress, the translation of nanoparticle-based systems critically depends on the ability to detect, quantify, and track them across complex biological environments. Over the past two decades, a wide spectrum of detection modalities has been developed, encompassing optical, magnetic, acoustic, nuclear, cytometric, and mass spectrometric principles. Yet, no comprehensive framework has been established to compare these methods in terms of sensitivity, spatial resolution, and clinical applicability. Methods: Here we show a systematic analysis of all broadly applicable nanoparticle detection strategies, outlining their mechanisms, advantages, and drawbacks, and providing illustrative examples of practical applications. Results: This comparison reveals that each modality occupies a distinct niche: optical methods offer high sensitivity but limited penetration depth; magnetic and acoustic modalities enable repeated non-invasive tracking; nuclear imaging ensures quantitative, whole-body visualization; and invasive biochemical or histological assays achieve ultimate detection limits at the cost of tissue integrity. These findings redefine how each technique contributes to nanoparticle biodistribution and mechanistic studies, clarifying which are best suited for translational and clinical use. Conclusions: Placed in a broader context, this review bridges fundamental nanotechnology with biomedical applications, outlining a unified methodological framework that will guide the rational design, validation, and clinical implementation of nanoparticle-based therapeutics and diagnostics. By synthesizing the field into a single comparative framework, it also provides an accessible entry point for newcomers in nanotechnology and related biomedical sciences.

The conversion of nicotinamide adenine dinucleotide (NAD+) to its reduced form (NADH) by dehydrogenases is a key step in numerous redox reactions and, consequently, in cellular energy conversion. NADH autofluorescence imaging represents a promising method for the optical detection of metabolic dysfunction in living tissues. However, it is sensitive to the total NAD(H) content as well as to variations in absorption and light scattering, which may fluctuate independently. A major objective is, therefore, to identify invariant quantities that are responsive to reversible ischemic tissue injury while circumventing the limitations of intensity-based imaging. We show experimentally and in silico that glutamate dehydrogenase (GDH) drives the NAD+/NADH balance toward a competing semi-equilibrium (CSE) state when an external catalytic process promotes the NADH → NAD+ conversion. This CSE state is uniquely determined by the total NAD(H) pool, the GDH concentration, and the external catalytic activity. Experimental validation using UV-induced NADH photolysis (300–500 mW/cm2), implementing the NADH → NAD+ reaction, showed that GDH activity can be estimated in the epicardium of ex vivo Langendorff-perfused hearts by analyzing the CSE. These results present a new approach to the optical assessment of tissue metabolic activity based on autofluorescence imaging of NADH. Our method allows the assessment of cardiac tissue ischemia without knowledge of the photolysis rate, thereby overcoming the inherent limitations of optical detection in living tissues.

The conversion of nicotinamide adenine dinucleotide (NAD⁺) to its reduced form (NADH) by dehydrogenases is a key step in numerous redox reactions and, consequently, in cellular energy conversion. NADH autofluorescence imaging represents a promising method for the optical detection of metabolic dysfunction in living tissues. However, it is sensitive to the total NAD(H) content as well as to variations in absorption and light scattering, which may fluctuate independently. A major objective is therefore to identify invariant quantities that are responsive to reversible ischemic tissue injury while circumventing the limitations of intensity-based imaging. We show experimentally and in silico that glutamate dehydrogenase drives the NAD⁺/NADH balance toward a dissipative equilibrium when an external catalytic process promotes the NADH → NAD⁺ conversion. This dissipative equilibrium state is uniquely determined by the total NAD(H) pool, the GDH concentration, and the external catalytic activity. Experimental validation using UV-induced NADH photolysis (300–500 mW/cm²) implementing the NADH → NAD⁺ reaction showed that GDH activity can be estimated in the epicardium of ex vivo Langendorff-perfused hearts by analyzing the dissipative equilibrium. These results present a new approach to optical assessment of tissue metabolic activity based on autofluorescence imaging of NADH. Our method allows assessment of cardiac tissue ischemia without knowledge of the photolysis rate, thereby overcoming the inherent limitations of optical detection in living tissues.

Introduction: Preservation of isolated hearts in cardioplegic solution at normothermia is a promising strategy for increasing the organ lifespan. Further development of this strategy and search for new products for solution delivery can help optimize the technology of donor heart transportation. Objective: The study was aimed to test the efficacy of device for normothermic constant perfusion flow with innovative lines for the cardioplegic solution delivery (CardioSystemPharma, Khimki, Moscow Region, Russia) according to the Langendorff mode in comparison with a system based on nodes and tubes of Radnoti Langendorff Constant Perfusion Flow Apparatus (ADInstruments, Colorado Springs, USA) in a series of experiments on rat hearts.Methods: The innovative cardioplegic delivery system (CardioSystemPharma) and traditional perfusion system (Radnoti) were compared in experiments on rat hearts at normothermia without cardioplegic solution and using the cardioplegic solution Normacor (Mosfarm, Moscow Region, Russia). The time until complete cardiac arrest and the changes in the NADH coenzyme fluorescence were recorded. After cardiac arrest, immunohistochemical staining of ventricular sections was performed to detect myocardial injury during perfusion.Results: It was shown that the innovative cardioplegic delivery system was not inferior to the traditional perfusion system (Radnoti) and even surpassed it in terms of the time duration for preservation of the isolated heart. It was found that the using of elevated glucose concentration during normothermic perfusion could significantly increase the organ lifespan. The efficacy of normothermic perfusion in the experiment was confirmed by monitoring cellular respiration through recording the NADH fluorescence.Conclusion: Testing showed that long-term preservation under normothermia with usage of an innovative delivery system of Russian manufacture is a promising replacement for Radnoti solution delivery system. Received 16 October 2024. Revised 23 November 2024. Accepted 10 December 2024. FundingThe study was carried out within the framework of the project “Innovative cardioplegic lines for cardiac surgery” under the Agreement on the provision of a grant from the Government of the Moscow Region in the fields of science, technology, engineering and innovation No. 12/04-24 dated 04/27/2024. Conflict of interestThe authors declare no conflict of interest. Contribution of the authorsConception and study design: V.A. Tsvelaya, S.D. Robustova, V.S. Kachan, M.S. Nosov, A.K. Berezhnoy, V.A. Kozlov, K.I. AgladzeData collection and analysis: S.D. Robustova, V.S. Kachan, D.V. Kononova, A.S. Yarovoy, M.A. Gusev, V.V. Litvinenko, V.D. Dzhabrailov, A.A. Brichagina, Z.V. Obrazumova, S.D. Chekalina, S.S. Bakumenko, E.A. Turchaninova, V.A. TsvelayaStatistic analysis: S.D. Robustova, V.S. Kachan, D.V. Kononova, A.S. Yarovoy, M.A. Gusev, V.V. Litvinenko, V.D. Dzhabrailov, A.A. Brichagina, Z.V. Obrazumova, S.D. Chekalina, S.S. Bakumenko, E.A. TurchaninovaDrafting the article: S.D. Robustova, V.S. Kachan, D.V. Kononova, Z.V. Obrazumova, E.A. Turchaninova, V.A. TsvelayaCritical revision of the article: S.D. Robustova, E.A. Turchaninova, V.A. Tsvelaya, K.I. AgladzeFinal approval of the version to be published: S.D. Robustova, V.S. Kachan, D.V. Kononova, A.S. Yarovoy, M.A. Gusev, V.V. Litvinenko, V.D. Dzhabrailov, A.A. Brichagina, Z.V. Obrazumova, S.D. Chekalina, E.A. Turchaninova, S.S. Bakumenko, M.S. Nosov, A.K. Berezhnoy, V.A. Kozlov, V.A. Tsvelaya, K.I. Agladze