This review synthesizes current research on the in vivo dark toxicity of upconversion nanoparticles (UCNPs) for biomedical applications, including luminescent imaging, diagnostics, and photoinduced therapy. The aim is to assess key toxicity determinants – nanoparticle type, surface coating, concentration, and dose relative to body weight – and to establish safe exposure thresholds. Analysis of comprehensive histological and biochemical studies indicates that UCNPs generally exhibit low toxicity under tested conditions. The most non-toxic concentration identified across studies is 2 mg/mL. For mice, the maximum permissible dose for short-term exposure (12 h) is 10 mg/kg, and for long-term exposure (120 days) is 50 mg/kg. For rats, a dose of 5 mg/kg is safe for both short- and long-term studies. While positively charged coatings (e.g., PEI) enhance cellular uptake, they may increase cytotoxicity compared to neutral or negatively charged coatings (e.g., PAA, PEG). Dissolution of UCNPs releasing rare-earth and fluoride ions contributes to dark toxicity, but biocompatible shells (silica, PEG) reduce this effect. Overall, UCNPs demonstrate favorable biocompatibility at established doses, supporting their continued development for in vivo theranostic applications. This review is the first of three parts; subsequent parts address phototoxicity and toxicity of multimodal particles.
This study focuses on the effects of moderate thermal heating on microcirculation and peripheral hemodynamics, as well as on the interrelationship between changes detected by Laser Doppler Flowmetry (LDF) and Ultrasound Doppler (USD). Microcirculation and peripheral hemodynamics were evaluated in the context of cardiovascular diagnostics using LDF and USDG. LDF non-invasively assessed tissue perfusion, reflecting the state of arterioles, venules, precapillary sphincters, and capillaries, thereby evaluating blood filling and tone in the microcirculatory bed. USDG was employed to assess blood flow in major arteries and calculate peripheral resistance indices, including resistance and pulsatility indices. General thermal heating from 20°C to 30°C was applied to observe its impact on both microvascular tone and major artery resistance indices. Moderate thermal heating increased perfusion and amplified the amplitude of neurogenic and myogenic oscillation rhythms. Peripheral resistance, as determined by USDG, decreased with rising temperature. The retrograde blood flow component, indicative of the tone of distal muscular-type vessels, disappeared upon warming, suggesting reduced resistance in both major arteries and microvessels. Additionally, the amplitude of antegrade diastolic flow, associated with the properties of elastic-type arteries, increased. Changes in microcirculation and peripheral hemodynamics are interconnected and follow a common physiological pattern: vasodilation and reduced tone in the microcirculatory bed. The decrease in USDG spectral indices in major arteries during heating correlates directly with the reduction in microvascular tone. While USDG can detect vascular resistance changes within a single cardiac cycle, LDF requires significantly more time to register such changes in microvascular tone.
We used time-resolved polarized fluorescence spectroscopy for the study of nicotinamide adenine dinucleotide phosphate (NADPH) bound to isocitrate dehydrogenase (IDH) and alcohol dehydrogenase (ADH). It was shown that the fluorescence lifetimes of bound NADPH are strongly enzyme-dependent and are practically identical to those of bound NADH, indicating that fluorescence lifetime imaging microscopy (FLIM) analysis cannot universally distinguish between these two coenzymes. However, in the polarization-sensitive experiments we observed sub-nanosecond fluorescence anisotropy decay components of NADPH bound to IDH and ADH that we found to be significantly enzyme-specific. This result suggests that combined lifetime and anisotropy analysis provides increased molecular specificity for NAD(P)H.
The aim of this study was to develop an irradiant exposure strategy able to control validity of the exposure reciprocity law upon exposing tarso-conjunctival tissue to ultraviolet A (UVA) radiation as a treatment for palpebral laxity, and thus to establish a research-based criterion for implementing optimal irradiation levels in clinical settings. Tarso-conjunctival specimens were harvested postmortem from ovine and caprine eyelids and exposed to UVA radiation (365 nm) in specified conditions. Thermographic infrared analysis was applied to monitor the photothermal response. By performing irradiation in the presence of a photosensitizer (riboflavin) a photochemomechanical response was also determined based on changes in mechanical properties as evaluated in a mechanical tester. A graphical method was employed to define the failure zones of reciprocity law when applied to radiation-induced photoresponses. Discontinuities in law’s validity were found and confirmed by descending values of Schwarzschild’s p-coefficients. The photothermal response showed that law’s failure zone centered on an irradiance of 30 mW/cm2 in both sheep and goat tissues, for radiant exposures between 6 and 18 J/cm2. The photochemomechanical response indicated a failure onset around 60 mW/cm2. Anticipating the concept of safest application route, an irradiance of 30 mW/cm2 appeared an appropriate upper limit for the validity zone of reciprocity law, as indicated by the photothermal response, at exposure durations assuring a radiant exposure between 5 and 20 J/cm2.
In this work, we propose a promising non-invasive approach based on the Raman spectroscopy of human serum for chronic heart failure (CHF) diagnosis. Due to the limited sample size, which limits the performance of machine learning classifiers, this study explores data augmentation techniques to improve the classification of low- and high-grade CHF spectra using k-nearest neighbor (kNN) and partial least squares discriminant analysis (PLS-DA) algorithms. Raman spectra of 151 patients with CHF of the different stages were acquired at 532 nm excitation from serum samples collected at Samara City Clinical Hospital. Two augmentation approaches were systematically evaluated: (1) combined approach based on the linear spectral transformations (wavenumber shifting ±1–2 cm⁻¹, intensity stretching 0.9-1.1) and (2) Wasserstein Generative Adversarial Network (WGAN)-based synthetic spectrum generation, expanding training datasets 10-fold while preserving physiochemical realism. Augmentation based on linear spectral transformations yielded algorithm-specific results: kNN showed no significant receiver operating characteristic area under curve (ROC AUC) improvement (0.67 ± 0.11 original vs. 0.67–0.69 augmented), while PLS-DA achieved statistically significant gains (0.71 ± 0.11 vs. 0.80–0.81; z = 2.3–2.6, p < 0.05). WGAN augmentation proved superior across both methods, with k-NN reaching 0.74 ± 0.08 and PLS-DA achieving 0.83 ± 0.09. These findings establish WGAN as an optimal augmentation strategy for Raman-based CHF classification, achieving clinically relevant performance (ROC AUC > 0.80) from limited cohorts while enabling biomarker identification for cardiovascular diagnostics.
