The formation of electronically excited species in the human multiple myeloma cell suspension

Mining reactive triplet carbonyls in biological systems

Aliphatic triplet carbonyls can be treated as short-lived radicals, since both species share similar reactions such as hydrogen atom abstraction, cyclization, addition, and isomerization. Importantly, enzyme-generated triplet carbonyls excite triplet molecular oxygen to the highly reactive, electrophilic singlet state by resonance energy transfer, which can react with proteins, lipids, and DNA. Carbonyl triplets, singlet oxygen, and radicals are endowed with the potential to trigger both normal and pathological responses. In this paper, we present a short review of easy, fast, and inexpensive preliminary tests for the detection of transient triplet carbonyls in chemical and biological systems. This paper covers direct and indirect methods to look for triplet carbonyls based on their spectral distribution of chemiluminescence, photoproduct analysis, quenching of light emission by conjugated dienes, and enhancement of light emission by the sensitizer 9,10-dibromoanthracence-2-sulfonate ion (DBAS).

Biological autoluminescence as a perturbance-free method for monitoring oxidation in biosystems

Biological oxidation processes are in the core of life energetics, play an important role in cellular biophysics, physiological cell signaling or cellular pathophysiology. Understanding of biooxidation processes is also crucial for biotechnological applications. Therefore, a plethora of methods has been developed for monitoring oxidation so far, each with distinct advantages and disadvantages. We review here the available methods for monitoring oxidation and their basic characteristics and capabilities. Then we focus on a unique method - the only one that does not require input of additional external energy or chemicals - which employs detection of biological autoluminescence (BAL). We highlight the pros and cons of this method and provide an overview of how BAL can be used to report on various aspects of cellular oxidation processes starting from oxygen consumption to the generation of oxidation products such as carbonyls. This review highlights the application potential of this completely non-invasive and label-free biophotonic diagnostic method.

Spectral Distribution of Ultra-Weak Photon Emission as a Response to Wounding in Plants: An In Vivo Study

It is well established that every living organism spontaneously emits photons referred to as ultra-weak photon emission (synonym biophotons or low-level chemiluminescence) which inherently embodies information about the wellbeing of the source. In recent years, efforts have been made to use this feature as a non-invasive diagnostic tool related to the detection of food quality, agriculture and biomedicine. The current study deals with stress resulting from wounding (mechanical injury) on Arabidopsis thaliana and how it modifies the spontaneous ultra-weak photon emission. The ultra-weak photon emission from control (non-wounded) and stressed (wounded) plants was monitored using different modes of ultra-weak photon emission measurement sensors like charge-coupled device (CCD) cameras and photomultiplier tubes (PMT) and the collected data were analyzed to determine the level of stress generated, photon emission patterns, and underlying biochemical process. It is generally considered that electronically excited species formed during the oxidative metabolic processes are responsible for the ultra-weak photon emission. In the current study, a high-performance cryogenic full-frame CCD camera was employed for two-dimensional in-vivo imaging of ultra-weak photon emission (up to several counts/s) and the spectral analysis was done by using spectral system connected to a PMT. The results show that Arabidopsis subjected to mechanical injury enhances the photon emission and also leads to changes in the spectral pattern of ultra-weak photon emission. Thus, ultra-weak photon emission can be used as a tool for oxidative stress imaging and can pave its way into numerous plant application research.

Anticancer Photodynamic Therapy Properties of Sulfur-Doped Graphene Quantum Dot and Methylene Blue Preparations in MCF-7 Breast Cancer Cell Culture

Photodynamic therapy (PDT) is a field with many applications including chemotherapy. Graphene quantum dots (GQDs) exhibit a variety of unique properties and can be used in PDT to generate singlet oxygen that destroys pathogenic bacteria and cancer cells. The PDT agent, methylene blue (MB), like GQDs, has been successfully exploited to destroy bacteria and cancer cells by increasing reactive oxygen species generation. Recently, combinations of GQDs and MB have been shown to destroy pathogenic bacteria via increased singlet oxygen generation. Here, we performed a spectrophotometric assay to detect and measure the uptake of GQDs, MB and several GQD-MB combinations in MCF-7 breast cancer cells. Then, we used a cell counting method to evaluate the cytotoxicity of GQDs, MB and a 1:1 GQD:MB preparation. Singlet oxygen generation in cells was then detected and measured using singlet oxygen sensor green. The dye, H₂ DCFDA, was used to measure reactive oxygen species production. We found that GQD and MB uptake into MCF-7 cells occurred, but that MB, followed by 1:1 GQD:MB, caused superior cytotoxicity and singlet oxygen and reactive oxygen species generation. Our results suggest that methylene blue's effect against MCF-7 cells is not potentiated by GQDs, either in light or dark conditions.

Short-time fractal analysis of biological autoluminescence

Biological systems manifest continuous weak autoluminescence, which is present even in the absence of external stimuli. Since this autoluminescence arises from internal metabolic and physiological processes, several works suggested that it could carry information in the time series of the detected photon counts. However, there is little experimental work which would show any difference of this signal from random Poisson noise and some works were prone to artifacts due to lacking or improper reference signals. Here we apply rigorous statistical methods and advanced reference signals to test the hypothesis whether time series of autoluminescence from germinating mung beans display any intrinsic correlations. Utilizing the fractional Brownian bridge that employs short samples of time series in the method kernel, we suggest that the detected autoluminescence signal from mung beans is not totally random, but it seems to involve a process with a negative memory. Our results contribute to the development of the rigorous methodology of signal analysis of photonic biosignals.

Mechanism of the Formation of Electronically Excited Species by Oxidative Metabolic Processes: Role of Reactive Oxygen Species

It is well known that biological systems, such as microorganisms, plants, and animals, including human beings, form spontaneous electronically excited species through oxidative metabolic processes. Though the mechanism responsible for the formation of electronically excited species is still not clearly understood, several lines of evidence suggest that reactive oxygen species (ROS) are involved in the formation of electronically excited species. This review attempts to describe the role of ROS in the formation of electronically excited species during oxidative metabolic processes. Briefly, the oxidation of biomolecules, such as lipids, proteins, and nucleic acids by ROS initiates a cascade of reactions that leads to the formation of triplet excited carbonyls formed by the decomposition of cyclic (1,2-dioxetane) and linear (tetroxide) high-energy intermediates. When chromophores are in proximity to triplet excited carbonyls, the triplet-singlet and triplet-triplet energy transfers from triplet excited carbonyls to chromophores result in the formation of singlet and triplet excited chromophores, respectively. Alternatively, when molecular oxygen is present, the triplet-singlet energy transfer from triplet excited carbonyls to molecular oxygen initiates the formation of singlet oxygen. Understanding the mechanism of the formation of electronically excited species allows us to use electronically excited species as a marker for oxidative metabolic processes in cells.

Light Emission from the Fe2+-EGTA-H₂O₂ System: Possible Application for the Determination of Antioxidant Activity of Plant Phenolics

Oxidative reactions can result in the formation of electronically excited species that undergo radiative decay depending on electronic transition from the excited state to the ground state with subsequent ultra-weak photon emission (UPE). We investigated the UPE from the Fe²⁺-EGTA (ethylene glycol-bis(β-aminoethyl ether)-N,N,N′,N′-tetraacetic acid)–H₂O₂ system with a multitube luminometer (Peltier-cooled photon counter, spectral range 380 to 630 nm). The UPE of 92.6 µmol/L Fe²⁺—185.2 µmol/L EGTA—2.6 mmol/L H₂O₂ reached 4319 ± 755 relative light units during 2 min measurement and was about seven times higher (p < 0.001) than the UPE of incomplete systems (Fe²⁺-H₂O₂, EGTA-H₂O₂) and medium alone. Substitution of Fe²⁺ with Cr²⁺, Co²⁺, Mn²⁺ or Cu²⁺ as well as of EGTA with EDTA (ethylenediaminetetraacetic acid) or citrate completely abolished UPE. Experiments with ROS scavengers revealed the dependence of UPE on hydroxyl radicals suggesting occurrence of oxidative attack and cleavage of the ether bond in EGTA backbone structure and formation of triplet excited carbonyl groups with subsequent light emission. Plant phenolics (ferulic, chlorogenic and caffec acids) at concentration 87 µmol/L and ascorbate at 0.46 mmol/L inhibited UPE by 90 ± 4%, 90 ± 5%, 97 ± 2% and 92 ± 1%, respectively. Quenching of UPE from Fe²⁺-EGTA-H₂O₂ system can be used for evaluation of antioxidant activity of phytochemicals.

Spectrum of spontaneous photon emission as a promising biophysical indicator for breast cancer research

In this study, we investigated the spectral characteristics of Spontaneous Photon Emission (SPE) from the body surface of a human breast cancer-bearing nude mice model during the overall growth process of breast cancers. By comparing and analyzing the data, we found that there was a striking difference between tumor mice and healthy controls in the spectral distribution of SPE from the body surface of lesion site, even when the morphological changes at the lesion site were not obvious. The spectral distribution of SPE from the healthy site of the tumor mice also differed from that of the healthy controls as the breast cancer developed to a certain stage. In addition, the difference in spectrum was related with different growth states of tumors. Interestingly, there was a positive correlation between the spectral ratio (610-630/395-455 nm) and the logarithm of the tumor volume for both the lesion site (R² = 0.947; p < 0.001) and the normal site (R² = 0.892; p < 0.001) of the tumor mice. The results suggested that the spectrum of SPE was sensitive to changes in the tumor status.

Oxidative species-induced excitonic transport in tubulin aromatic networks: Potential implications for neurodegenerative disease

Oxidative stress is a pathological hallmark of neurodegenerative tauopathic disorders such as Alzheimer's disease and Parkinson's disease-related dementia, which are characterized by altered forms of the microtubule-associated protein (MAP) tau. MAP tau is a key protein in stabilizing the microtubule architecture that regulates neuron morphology and synaptic strength. When MAP tau is degraded in tauopathic disorders, neuron dysfunction results. The precise role of reactive oxygen species (ROS) in the tauopathic disease process, however, is poorly understood. Classically, mitochondrial dysfunction has been viewed as the major source of oxidative stress and has been shown to precede tau and amyloid pathology in various dementias, but the exact mechanisms are not clear. It is known that the production of ROS by mitochondria can result in ultraweak photon emission (UPE) within cells. While of low intensity, surrounding proteins within the cytosol can still absorb these energetic photons via aromatic amino acids (e.g., tryptophan and tyrosine). One likely absorber of these photons is the microtubule cytoskeleton, as it forms a vast network spanning neurons, is highly co-localized with mitochondria, and shows a high density of aromatic amino acids. Functional microtubule networks may traffic this ROS-generated endogenous photon energy for cellular signaling, or they may serve as dissipaters/conduits of such energy to protect the cell from potentially harmful effects. Experimentally, after in vitro exposure to exogenous photons, microtubules have been shown to reorient and reorganize in a dose-dependent manner with the greatest effect being observed around 280nm, in the tryptophan and tyrosine absorption range. In this paper, recent modeling efforts based on ambient temperature experiment are presented, showing that tubulin polymers can feasibly absorb and channel these photoexcitations via resonance energy transfer, on the order of dendritic length scales and neuronal fine structure. Since microtubule networks are compromised in tauopathic diseases such as Alzheimer's and Parkinson's dementias, patients with these illnesses would be unable to support effective channeling of these photons for signaling or dissipation. Consequent emission surplus due to increased UPE production or decreased ability to absorb and transfer may lead to increased cellular oxidative damage, thus hastening the neurodegenerative process.

The Contribution of Singlet Oxygen to Insulin Resistance

Insulin resistance contributes to the development of diabetes and cardiovascular dysfunctions. Recent studies showed that elevated singlet oxygen-mediated lipid peroxidation precedes and predicts diet-induced insulin resistance (IR), and neutrophils were suggested to be responsible for such singlet oxygen production. This review highlights literature suggesting that insulin-responsive cells such as endothelial cells, hepatocytes, adipocytes, and myocytes also produce singlet oxygen, which contributes to insulin resistance, for example, by generating bioactive aldehydes, inducing endoplasmic reticulum (ER) stress, and modifying mitochondrial DNA. In these cells, nutrient overload leads to the activation of Toll-like receptor 4 and other receptors, leading to the production of both peroxynitrite and hydrogen peroxide, which react to produce singlet oxygen. Cytochrome P450 2E1 and cytochrome c also contribute to singlet oxygen formation in the ER and mitochondria, respectively. Endothelial cell-derived singlet oxygen is suggested to mediate the formation of oxidized low-density lipoprotein which perpetuates IR, partly through neutrophil recruitment to adipose tissue. New singlet oxygen-involving pathways for the formation of IR-inducing bioactive aldehydes such as 4-hydroperoxy-(or hydroxy or oxo)-2-nonenal, malondialdehyde, and cholesterol secosterol A are proposed. Strategies against IR should target the singlet oxygen-producing pathways, singlet oxygen quenching, and singlet oxygen-induced cellular responses.

Versatile Polymer Nanoparticles as Two-Photon-Triggered Photosensitizers for Simultaneous Cellular, Deep-Tissue Imaging, and Photodynamic Therapy

Clinical applications of current photodynamic therapy (PDT) photosensitizers (PSs) are often limited by their absorption in the UV-vis range that possesses limited tissue penetration ability, leading to ineffective therapeutic response for deep-seated tumors. Alternatively, two-photon excited PS (TPE-PS) using NIR light triggered is one the most promising candidates for PDT improvement. Herein, multimodal polymer nanoparticles (PNPs) from polythiophene derivative as two-photon fluorescence imaging as well as two-photon-excited PDT agent are developed. The prepared PNPs exhibit excellent water dispersibility, high photostability and pH stability, strong fluorescence brightness, and low dark toxicity. More importantly, the PNPs also possess other outstanding features including: (1) the high ¹ O₂ quantum yield; (2) the strong two-photon-induced fluorescence and efficient ¹ O₂ generation; (3) the specific accumulation in lysosomes of HeLa cells; and (4) the imaging detection depth up to 2100 µm in the mock tissue under two-photon. The multifunctional PNPs are promising candidates as TPE-PDT agent for simultaneous cellular, deep-tissue imaging, and highly efficient in vivo PDT of cancer.

Endogenous Generation of Singlet Oxygen and Ozone in Human and Animal Tissues: Mechanisms, Biological Significance, and Influence of Dietary Components

Recent studies have shown that exposing antibodies or amino acids to singlet oxygen results in the formation of ozone (or an ozone-like oxidant) and hydrogen peroxide and that human neutrophils produce both singlet oxygen and ozone during bacterial killing. There is also mounting evidence that endogenous singlet oxygen production may be a common occurrence in cells through various mechanisms. Thus, the ozone-producing combination of singlet oxygen and amino acids might be a common cellular occurrence. This paper reviews the potential pathways of formation of singlet oxygen and ozone in vivo and also proposes some new pathways for singlet oxygen formation. Physiological consequences of the endogenous formation of these oxidants in human tissues are discussed, as well as examples of how dietary factors may promote or inhibit their generation and activity.

High-Throughput Method for Automated Colony and Cell Counting by Digital Image Analysis Based on Edge Detection

Counting cells and colonies is an integral part of high-throughput screens and quantitative cellular assays. Due to its subjective and time-intensive nature, manual counting has hindered the adoption of cellular assays such as tumor spheroid formation in high-throughput screens. The objective of this study was to develop an automated method for quick and reliable counting of cells and colonies from digital images. For this purpose, I developed an ImageJ macro Cell Colony Edge and a CellProfiler Pipeline Cell Colony Counting, and compared them to other open-source digital methods and manual counts. The ImageJ macro Cell Colony Edge is valuable in counting cells and colonies, and measuring their area, volume, morphology, and intensity. In this study, I demonstrate that Cell Colony Edge is superior to other open-source methods, in speed, accuracy and applicability to diverse cellular assays. It can fulfill the need to automate colony/cell counting in high-throughput screens, colony forming assays, and cellular assays.

Reactive oxygen species: Reactions and detection from photosynthetic tissues

Reactive oxygen species (ROS) have long been recognized as compounds with dual roles. They cause cellular damage by reacting with biomolecules but they also function as agents of cellular signaling. Several different oxygen-containing compounds are classified as ROS because they react, at least with certain partners, more rapidly than ground-state molecular oxygen or because they are known to have biological effects. The present review describes the typical reactions of the most important ROS. The reactions are the basis for both the detection methods and for prediction of reactions between ROS and biomolecules. Chemical and physical methods used for detection, visualization and quantification of ROS from plants, algae and cyanobacteria will be reviewed. The main focus will be on photosynthetic tissues, and limitations of the methods will be discussed.