Cerebral ischaemia is an acute state characterised by a severe decrease in the supply of oxygen (O2) to the brain, resulting in the death of neurons and glial cells. Despite multiple studies investigating the processes that lead to cell damage under ischaemic stroke, there is still a lack of information about the changes in blood properties under various phases of transient ischaemia with restoration of blood flow or under prolonged ischaemia. Blood, as a source of O2, might either contribute to the brain damage owing to the development of oxidative stress, or might prevent cell death by the modulation of O2 bioavailability to cells. Here, we studied hydrogen peroxide (H2O2) generation in mitochondria of neurons in vivo using the H2O2-sensitive biosensor HyPer7, and blood properties [haemoglobin (Hb) oxygenation and Hb affinity to O2, estimated with Raman microspectroscopy (RS)] in two experimental rat models: transient 60-min ischaemia induced by the occlusion of the middle cerebral artery (MCAO) followed by 48 h reperfusion, and permanent 48-h MCAO-induced ischaemia. We found that an increase in the amount of H2O2 synthesised in neuronal mitochondria under the reperfusion period correlated with a decrease in blood oxygenation level, whereas permanent ischaemia did not affect the amount of oxyhaemoglobin but led to an increase in the affinity of Hb to O2. We hypothesise that H2O2 may initiate processes that lead to increased O2 penetration to the brain tissue under reperfusion, and that increased Hb affinity to O2 may be an adaptive reaction of the blood system to acute prolonged ischaemia.

This review highlights current insights into the regulation of the mitochondrial respiratory chain (electron transport chain, ETC) activity. The regulation of ETC properties optimizes ATP synthesis and controls the generation of the superoxide anion radical (O2•−) which can be converted into other reactive oxygen species (ROS) playing a dual role by initiating signaling cascades or contributing to oxidative stress. We examine how ETC activity is influenced by the structure and conformation of its complexes, their allosteric or post-translational modifications, and their interactions with membrane lipids. The formation and function of supercomplexes, as well as their cell-type-specific characteristics, are also discussed, alongside with the role of intracellular Ca2+ concentration in the modulation of ETC activity. Furthermore, we discuss mechanisms and sites of O2•− generation within ETC complexes, O2•− fate in the mitochondrial matrix, and the impact of cytochrome c (Cyt c) conformation and allosteric modifications on ETC function. Finally, we discuss various abnormalities in ETC complexes, emphasizing their relevance to mitochondrial dysfunction and disease.

Clothianidin (CL) is a neonicotinoid insecticide widely used in crop protection against insect pests. However, its effects on photosynthesis remain largely unknown. Here, by investigating the influence of CL at the concentrations of 22 and 110 μg/L on the primary processes of photosynthesis, membrane fluidity and structural changes of pea chloroplasts, we located several primary binding sites of this pesticide. Similar dynamics were observed for both concentrations. However, statistically significant differences were only found at 110 μg/L for all methods used. The light saturated rate of linear electron flow decreased mainly due to the disturbance of electron flow on the acceptor side of photosystem II (PSII) associated with the appearance of QB-nonreducing centers and empty QB binding sites of PSII. The functioning of the donor side of PSII, the activity of photosystem I (PSI) and the maximum quantum yield of PSII photochemistry (Fv/Fm) were not found to be significantly altered. Increased membrane fluidity and structural alterations of the thylakoid membrane led to a decrease in the development of the proton gradient ΔрН and membrane energization processes.

Fluoroquinolone antibiotics such as ciprofloxacin have been actively used in medical practice, including the COVID-19 pandemic, to suppress adverse bacterial infections. Widespread application and improper disposal have resulted in the ubiquity of antibiotics in the environment, which can affect aquatic life, including phytoplankton. The effect of fluoroquinolone antibiotics on the photosynthetic processes of marine diatoms, which are the main producers in marine ecosystems, has been little studied. In this work the effect of the antibiotic ciprofloxacin on the primary photosynthetic processes in the marine diatom Thalassiosira weissflogii was studied. It has been shown that ciprofloxacin affects the functioning of PSII, preventing the transfer of absorbed energy from the excited antenna chlorophyll molecules to the PSII RC (φDo). Under the influence of ciprofloxacin, a decrease in the efficiency of electron donation to P680+ (FV / FO), inhibition of the quantum yield of PSII (FV / FM), a decrease in the proportion of active RCs (ABS / RC), and an increase in the dissipation of absorbed energy in RCs (DIo / RC) were revealed. It has been shown that the mechanism of action of ciprofloxacin is associated with damage of PSII RC. Ciprofloxacin enhances the photosensitivity of microalgae and causes an increase in lipid peroxidation products. It is proposed to apply the parameters of chlorophyll fluorescence analyzing the effect of antibiotics on microalgae.

Carbon dots are a new type of carbon-based material with some unique properties which are attractive for agricultural, biological, medical and nanotechnological applications. The widespread production of graphene for composite materials as well as the formation of carbon dots as by-products (industry, food heat treatment etc.) leading to inevitable environmental pollution. However, the environmental impact posed by them on living organisms is still insufficient investigated. We studied the effects of carbon dots synthesized in our laboratory via electrochemical (classified as graphene quantum dots), hydrothermal and microwave (classified as carbon nanodots) methods on the green microalga Scenedesmus quadricauda. The microalgae were exposed to different concentrations of carbon dots for 6 days. Our results showed that carbon dots did not induce oxidative stress and affect the photosynthetic activity of microalgae. However, carbon dots could decrease the growth rate of microalgae mainly due to reducing light, which occurred via the shading of microalgae by nanoparticles. The obtained results contribute to the understanding of the interaction of carbon dots and microalgae.

Oxidative stress leads to multiple changes in properties of cells and of biological liquids that can cause various pathologies including cardiovascular and metabolic diseases. Modern test systems make it possible to assess the concentration of oxidized molecules in the blood plasma, but do not provide direct information about oxidation of cell membranes. In this work, we presented an effective, scalable, and inexpensive technique for manufacturing biomimetic SERS sensors for the detection of biomembrane oxidation. The main feature of this technique is the use of rose petals as templates for scalable manufacturing of SERS substrates with a cavity structure that promotes the capture and immobilization of blood cells on the grooved inner surfaces of microcavities. To obtain the SERS effect in these microcavities, the silicone replicas of rose petals were covered with an Au thin film (100 nm) and spherical Au nanoparticles by the sequential deposition and annealing processes. The application of SERS substrates with a cavity structure enables to perform studies on individual erythrocytes and detect first signs of their membrane oxidation, which can be used for early diagnostics of various blood and metabolic diseases.

The balance between the mitochondrial respiratory chain activity and the cell's needs in ATP ensures optimal cellular function. Cytochrome c is an essential component of the electron transport chain (ETC), which regulates ETC activity, oxygen consumption, ATP synthesis and can initiate apoptosis. The impact of conformational changes in cytochrome c on its function is not understood for the lack of access to these changes in intact mitochondria. We have developed a novel sensor that uses unique properties of label-free surface-enhanced Raman spectroscopy (SERS) to identify conformational changes in heme of cytochrome c and to elucidate their role in functioning mitochondria. We have verified that molecule bond vibrations assessed by SERS are a reliable indicator of the heme conformation during changes in the inner mitochondrial membrane potential and ETC activity. We have demonstrated that cytochrome c heme reversibly switches between planar and ruffled conformations in response to the inner mitochondrial membrane potential (ΔΨ) and H+ concentration in the intermembrane space. This regulates the efficiency of the mitochondrial respiratory chain, thus, adjusting the mitochondrial respiration to the cell's consumption of ATP and the overall activity. We have found that under hypertensive conditions cytochrome c heme loses its sensitivity to ΔΨ that can affect the regulation of ETC activity. The ability of the proposed SERS-based sensor to track mitochondrial function opens broad perspectives in cell bioenergetics.

Widely used in biomedical and bioanalytical applications, the detonation nanodiamonds (NDs) are generally considered to be biocompatible and non-toxic to a wide range of eukaryotic cells. Due to their high susceptibility to chemical modifications, surface functionalisation is often used to tune the biocompatibility and antioxidant activity of the NDs. The response of photosynthetic microorganisms to redox-active NDs is still poorly understood and is the focus of the present study. The green microalga Chlamydomonas reinhardtii was used to assess the potential phytotoxicity and antioxidant activity of NDs hosting hydroxyl functional groups at concentrations of 5–80 μg NDs/mL. The photosynthetic capacity of microalgae was assessed by measuring the maximum quantum yield of PSII photochemistry and the light-saturated oxygen evolution rate, while oxidative stress was assessed by lipid peroxidation and ferric-reducing antioxidant capacity. We demonstrated that hydroxylated NDs might reduce cellular levels of oxidative stress, protect PSII photochemistry and facilitate the PSII repair under methyl viologen and high light associated stress conditions. Factors involved in this protection may include the low phytotoxicity of hydroxylated NDs in microalgae and their ability to accumulate in cells and scavenge reactive oxygen species. Our findings could pave the way for using hydroxylated NDs as antioxidants to improve cellular stability in algae-based biotechnological applications or semi-artificial photosynthetic systems.

In the present study, complex patterns of algal response to chromium (K2Cr2O7, Cr) and cadmium (CdSO4, Cd) toxicity were examined. Chlorophyll and starch content, photosynthetic activity and respiration rate, fatty acid content and composition, cell density (growth rate), malondialdehyde content (oxidative stress), ferric reducing antioxidant power and phenolic content (antioxidant activity) were measured in the model green algae species Scenedesmus quadricauda and Chlorella sorokiniana during exposure to 20 or 50 μM of Cr or Cd. Cell response to Cd showed similar patterns in both algae, whereas Cr effects differed, especially regarding the antioxidant activity. Malondialdehyde content, starch content, and respiration rate were the parameters most affected by both metals in both species. Only respiration rate increased dramatically under all treatments studied. In general, the Cd or Cr poisoning induced the transition of cell metabolism from “assimilatory” mode with active photosynthesis to “catabolic” mode characterized by elevated respiration and increased content of starch, a substrate for respiration. Chlorella sorokiniana cells showed a prominent response to Cr indicating suitability for bioassay of Cr contamination in the aquatic environment. A method for comprehensive screening of algal species on their heavy metal tolerance is proposed.

Surface-enhanced Raman spectroscopy (SERS) is a promising tool that can be used in the detection of molecular changes triggered by disease development. Cardiovascular diseases (CVDs) are caused by multiple pathologies originating at the cellular level. The identification of these deteriorations can provide a better understanding of CVD mechanisms, and the monitoring of the identified molecular changes can be employed in the development of novel biosensor tools for early diagnostics. We applied plasmonic SERS nanosensors to assess changes in the properties of erythrocytes under normotensive and hypertensive conditions in the animal model. We found that spontaneous hypertension in rats leads (i) to a decrease in the erythrocyte plasma membrane fluidity and (ii) to a decrease in the mobility of the heme of the membrane-bound hemoglobin. We identified SERS parameters that can be used to detect pathological changes in the plasma membrane and submembrane region of erythrocytes.

The number of microplastic particles in the environment is constantly increasing as a result of the decay of plastic waste, the incineration of which is associated with air emissions and the concentration of toxic combustion products in ash residues. Although numerous researchers have studied the effects of MPs on living organisms, only a small part of the published data is devoted to the study of the long-term toxic effects that MPs and combustion products of plastic have on phytoplankton organisms. The effect of different types of MPs and plastic incineration ash on the structural and functional growth parameters of a green microalga Scenedesmus quadricauda culture used as a test object was studied in a chronic experiment lasting 21 days. The development of the species was studied with the addition of five types of weathered MPs samples, obtained from macroplastics, collected in the supralittoral of the Barents Sea and one unweathered control sample at a concentration of 3 mg/L. In terms of changes in the number of Scenedesmus quadricauda cells, the following toxicity series was obtained in descending order: PU (polyurethane foam, weathered) > HDPE (food package, white, weathered) > HDPE (food package, red, weathered) > EPS (packaging material, weathered) > EPS (packaging material, unweathered) > PP (ship rope, weathered). In terms of the efficiency of photosynthesis (maximum quantum yield of PSII photochemistry ( F V / F M )), polyurethane foam was found to be nontoxic, while other samples of MPs had a weak toxic effect. The effect of MPs on the culture caused a mosaic response, assessed by different parameters of the test object state: a strong inhibition of culture growth (with the addition of polyurethane foam) can be accompanied by a significant increase in thiobarbituric acid reactive substances (TBARS) in microalgal cells, while photosynthesis efficiency may not change. The toxicity of the residual ash obtained from the incineration of a mixture of weathered macroplastics was significantly higher than the toxicity of microplastics. Residual ash was studied at concentrations of 0.01, 0.1, 1, 10, 100, and 1000 mg/L and the toxicity was detected in terms of the change in the cell number only at a concentration of 1000 mg/L, at 0.01 mg/L in terms of the photosynthesis efficiency, and at 0.1 mg/L and above by the change in the amount of TBARS in microalgal cells.

Carotenoids are potent antioxidants with a wide range of biomedical applications. However, their delivery into human cells is challenging and relatively inefficient. While the use of natural water-soluble carotenoproteins capable to reversibly bind carotenoids and transfer them into membranes is promising, the quantitative estimation of the delivery remains unclear. In the present work, we studied echinenone (ECN) delivery by cyanobacterial carotenoprotein AnaCTDH (C-terminal domain homolog of the Orange Carotenoid Protein from Anabaena), into liposome membranes labelled with BODIPY fluorescent probe. We observed that addition of AnaCTDH-ECN to liposomes led to the significant changes in the fast-kinetic component of the fluorescence decay curve, pointing on the dipole-dipole interactions between the probe and ECN within the membrane. It may serve as an indirect evidence of ECN delivery into membrane. To study the delivery in detail, we carried out molecular dynamics modeling of the localization of ECN within the lipid bilayer and calculate its orientation factor. Next, we exploited FRET to assess concentration of ECN delivered by AnaCTDH. Finally, we used time-resolved fluorescence anisotropy to assess changes in microviscosity of liposomal membranes. Incorporation of liposomes with β-carotene increased membrane microviscosity while the effect of astaxanthin and its mono- and diester forms was less pronounced. At temperatures below 30 °C addition of AnaCTDH-ECN increased membrane microviscosity in a concentration-dependent manner, supporting the protein-mediated carotenoid delivery mechanism. Combining all data, we propose FRET-based analysis and assessment of membrane microviscosity as potent approaches to characterize the efficiency of carotenoids delivery into membranes.

A key event in the cytochrome c-dependent apoptotic pathway is the permeabilization of the outer mitochondrial membrane, resulting in the release of various apoptogenic factors, including cytochrome c, into the cytosol. It is believed that the permeabilization of the outer mitochondrial membrane can be induced by the peroxidase activity of cytochrome c in a complex with cardiolipin. Using a number of mutant variants of cytochrome c, we showed that both substitutions of Lys residues from the universal binding site for oppositely charged Glu residues and mutations leading to a decrease in the conformational mobility of the red Ω-loop in almost all cases did not affect the ability of cytochrome c to bind to cardiolipin. At the same time, the peroxidase activity of all mutant variants in a complex with cardiolipin was three to five times higher than that of the wild type. A pronounced increase in the ability to permeabilize the lipid membrane in the presence of hydrogen peroxide, as measured by calcein leakage from liposomes, was observed only in the case of four substitutions in the red Ω-loop (M4 mutant). According to resonance and surface-enhanced Raman spectroscopy, the mutations caused significant changes in the heme of oxidized cytochrome c molecules resulting in an increased probability of the plane heme conformation and the enhancement of the rigidity of the protein surrounding the heme. The binding of wild-type and mutant forms of oxidized cytochrome c to cardiolipin-containing liposomes caused the disordering of the acyl lipid chains that was more pronounced for the M4 mutant. Our findings indicate that the Ω-loop is important for the pore formation in cardiolipin-containing membranes.

Red blood cell (RBC) aggregation and deformation are governed by the molecular processes occurring on the membrane. Since several social important diseases are accompanied by alterations in RBC aggregation and deformability, it is important to develop a diagnostic parameter of RBC membrane structural integrity and stability. In this work, we propose membrane microviscosity assessed by time-resolved fluorescence anisotropy of the lipophilic PKH26 fluorescent probe as a diagnostic parameter. We measured the fluorescence decay curves of the PKH26 probe in the RBC membrane to establish the optimal parameters of the developed fluorescence assay. We observed a complex biphasic profile of the fluorescence anisotropy decay characterized by two correlation times corresponding to the rotational diffusion of free PKH26, and membrane-bounded molecules of the probe. The developed assay allowed us to estimate membrane microviscosity ηm in the range of 100–500 cP depending on the temperature, which paves the way for assessing RBC membrane properties in clinical applications as predictors of blood microrheological abnormalities.

— Intrauterine hypoxia is the most common prenatal risk factor presenting a direct danger not only to the life of the fetus but also to the future postnatal life of the organism. The aim of this study is to reveal an association between fetal hypoxia and oxidative stress as well as to estimate the significance of gestational age and gender for the development of oxidative stress. Pregnant rats were exposed to acute hypoxia on the tenth or 20th day of pregnancy, which corresponds to the first and second trimesters of human pregnancy. In newborn rats on the second day of life and in sexually mature offspring of both sexes on the 60th day of life, the state of antioxidant protection was estimated by the content of nonprotein thiols in the blood and liver homogenate, catalase, and superoxide dismutase activity in the liver homogenate, total antioxidant activity, and ceruloplasmin level in blood plasma as well as by the intensity of lipid peroxidation in blood plasma and liver homogenate. Regardless of the gestational age at which the offspring experienced acute hypoxia numerous changes in the indices of the antioxidant protection system were recorded in newborn rats, indicating in favor of the development of oxidative stress; this can be a cause of neurological and cardiological disorders shown already in adult animals.

Pregnancy in mammals is characterized by an increase in basal oxygen consumption. As it develops, there is an increase in oxidative stress, while the oxidative damage enhances in pregnancy complicated by hypoxic stress. The oxidative stress during prenatal development seems to be one of the key factors in the pathogenesis of most pregnancy disorders, including preterm birth and preeclampsia. The growing demand for oxygen increases either the production of reactive oxygen species or the synthesis of antioxidant defense components. To assess the antioxidant defense activity in rats, the content of nonprotein thiols in the blood and liver homogenate, catalase activity in liver homogenate, superoxide dismutase activity in blood plasma and liver homogenate, total antioxidant capacity in blood plasma, and the intensity of lipid peroxidation in blood plasma and liver homogenate were determined. According to obtained data, a decrease in antioxidant defense activity in blood plasma and liver of females is shown in the prenatal period of normal pregnancy and, particularly, in the same period of pregnancy complicated by hypoxic stress. It can be assumed that changes in blood’s antioxidant defense parameters reflect changes not only in the mother’s body but also in the placenta, providing potential danger to the developing fetus.

An automated interference microscope has been used to determine the rms amplitude of fluctuations of living cells in vitro. The geometric thickness of cells has been calculated based on the measured optical path differences of light waves and the equivalent elastic constants of these cells have been estimated. The determined rms amplitude of fluctuations of the optical path difference is 0.3–2.7 nm, which corresponds to 4–40 nm rms amplitude of membrane-thickness fluctuations. The amplitudes of fluctuations of spread cells (endothelial cells and macrophages) are smaller relative to unattached cells (in vitro red blood cells and lymphocytes). At the same time, the amplitude of fluctuations observed in HeLa tumor cells spread on a substrate exceeds the amplitude of fluctuations of other spread cells (endothelial cells and macrophages). The obtained experimental data are in agreement with the earlier results obtained using other optical methods.

The antioxidant system activity during normal pregnancy and pregnancy following by hypoxic stress Pregnancy in mammals is characterized by an increase in basal oxygen consumption, as it develops there is an increase in oxidative stress while in pregnancy complicated by hypoxic stress the oxidative damage enhances. The oxidative stress during prenatal development seems to be one of the key factors in the pathogenesis of most pregnancy disorders, including preterm birth and preeclampsia. The growing demand for oxygen increases either the production of reactive oxygen species or the synthesis of antioxidant defense components. To assess the antioxidant defense activity in rats, the content of non-protein thiols in the blood and liver homogenate, catalase activity in liver homogenate, superoxide dismutase activity in blood plasma and liver homogenate, total antioxidant activity in blood plasma, and the intensity of lipid peroxidation in blood plasma and liver homogenate were determined. According to data obtained a decrease in antioxidant defense activity in blood plasma and liver of females is shown in the prenatal period of normal pregnancy and, particularly, in the same period of pregnancy complicated by hypoxic stress. It can be assumed that changes in blood antioxidant defense parameters reflect changes not only in mother’s body, but also in placenta, providing potential danger to the developing fetus.