Rationale for the real-time and dynamic cell death assays using propidium iodide

pH-Responsive self-assembled polymer-photosensitizer conjugate for activable photodynamic therapy

This paper reports synthesis, aqueous self-assembly and relevance of the pH-triggered activable photodynamic therapy of amphiphilic polyurethane (P1S) functionalized with a heavy-atom free organic photosensitizer. Condensation polymerization between 1,4-diisocyanatobutane and two different dihydroxy monomers (one having a pendant hydrophilic wedge and the other having 1,3-dihydroxypropan-2-one with a reactive carbonyl group) in the presence of a measured amount of (S)-2-methylbutan-1-ol (chain-stopper) and DABCO catalyst produces a reactive pre-polymer P1. Hydrazide-functionalized thionated-naphthalenemonoimide (NMIS), which acts as a photosensitizer, reacted with the carbonyl-functionality of P1 to obtain the desired polymer-photosensitizer conjugate P1S in which the dye was attached to the polymer backbone via an acid-labile hydrazone linker. In water, P1S adopted an intra-chain H-bonding stabilized folded structure, which further assembled to produce a polymersome structure (Dh ≈ 200 nm), in which the hydrophobic membrane consists of aggregated NMIS and trialkoxy-benzene chromophores, as evident from UV/vis, CD and small-angle X-ray diffraction studies. In the aggregated state, NMIS loses its reactive oxygen species (ROS) generation ability and remains in a dormant state. However, under acidic conditions (pH 5.5), the photosensitizer is detached (presumably because of the cleavage of the hydrazone linker) and regains its full ROS-generation activity under photoirradiation, as evidenced from the standard DCFH assay. To test the possibility of such pH-activable intra-cellular ROS generation, P1S was treated with HeLa cells, as it is known that cancer cells are more acidic than normal cells. Indeed, photoirradiation-induced intra-cellular ROS generation was evident by the DCFH assay, resulting in efficient cell killing.

Acoustic enrichment of sperm for in vitro fertilization

Assisted reproductive technology (ART) has emerged as a crucial method in modern medicine for tackling infertility. However, the success of fertilization depends on the quality and quantity of sperm, often necessitating invasive surgical intervention, which presents challenges for non-invasive in vitro fertilization. Acoustic microfluidics technology has found widespread application across various biological contexts. In this paper, we propose to introduce a novel approach using asymmetric acoustic streaming generated by a single interdigital transducer (IDT) to enhance sperm concentration and improve fertilization in vitro, particularly in cases of moderate oligozoospermia. The concentration of particles increased approximately 6-fold in the central region after acoustic enrichment. Moreover, sperm motility was significantly improved without additional DNA fragmentation, and all the oocytes remained viable after 5 min of acoustic enrichment. Notably, acoustic enrichment accelerated fertilization and embryo development, leading to a higher fertilization rate and faster cleavage speed. Specifically, within 36 hours, the multiple-cell embryo ratio was significantly increased compared to the control group. This finding further validates the feasibility and non-invasiveness of acoustic enrichment for sperm fertilization in vitro. This work provides a promising tool for in vitro fertilization, holding significant implications for assisted reproduction.

Targeted Delivery of Sucrose-Coated Nanocarriers with Chemical Cargoes to the Plant Vasculature Enhances Long-Distance Translocation

Current practices for delivering agrochemicals are inefficient, with only a fraction reaching the intended targets in plants. The surfaces of nanocarriers are functionalized with sucrose, enabling rapid and efficient foliar delivery into the plant phloem, a vascular tissue that transports sugars, signaling molecules, and agrochemicals through the whole plant. The chemical affinity of sucrose molecules to sugar membrane transporters on the phloem cells enhances the uptake of sucrose-coated quantum dots (sucQD) and biocompatible carbon dots with β-cyclodextrin molecular baskets (suc-β-CD) that can carry a wide range of agrochemicals. The QD and CD fluorescence emission properties allowed detection and monitoring of rapid translocation (<40 min) in the vasculature of wheat leaves by confocal and epifluorescence microscopy. The suc-β-CDs more than doubled the delivery of chemical cargoes into the leaf vascular tissue. Inductively coupled plasma mass spectrometry (ICP-MS) analysis showed that the fraction of sucQDs loaded into the phloem and transported to roots is over 6.8 times higher than unmodified QDs. The sucrose coating of nanoparticles approach enables unprecedented targeted delivery to roots with ≈70% of phloem-loaded nanoparticles delivered to roots. The use of plant biorecognition molecules mediated delivery provides an efficient approach for guiding nanocarriers containing agrochemicals to the plant vasculature and whole plants.

Gasdermin E dictates inflammatory responses by controlling the mode of neutrophil death

Both lytic and apoptotic cell death remove senescent and damaged cells in living organisms. However, they elicit contrasting pro- and anti-inflammatory responses, respectively. The precise cellular mechanism that governs the choice between these two modes of death remains incompletely understood. Here we identify Gasdermin E (GSDME) as a master switch for neutrophil lytic pyroptotic death. The tightly regulated GSDME cleavage and activation in aging neutrophils are mediated by proteinase-3 and caspase-3, leading to pyroptosis. GSDME deficiency does not alter neutrophil overall survival rate; instead, it specifically precludes pyroptosis and skews neutrophil death towards apoptosis, thereby attenuating inflammatory responses due to augmented efferocytosis of apoptotic neutrophils by macrophages. In a clinically relevant acid-aspiration-induced lung injury model, neutrophil-specific deletion of GSDME reduces pulmonary inflammation, facilitates inflammation resolution, and alleviates lung injury. Thus, by controlling the mode of neutrophil death, GSDME dictates host inflammatory outcomes, providing a potential therapeutic target for infectious and inflammatory diseases.

Analysis of possible pathways on the mechanism of action of minocycline and doxycycline against strains of Candida spp. resistant to fluconazole

Species of the genus Candida, characterized as commensals of the human microbiota, are opportunistic pathogens capable of generating various types of infections with high associated costs. Considering the limited pharmacological arsenal and the emergence of antifungal-resistant strains, the repositioning of drugs is a strategy used to search for new therapeutic alternatives, in which minocycline and doxycycline have been evaluated as potential candidates. Thus, the objective was to evaluate the in vitro antifungal activity of two tetracyclines, minocycline and doxycycline, and their possible mechanism of action against fluconazole-resistant strains of Candida spp. The sensitivity test for antimicrobials was performed using the broth microdilution technique, and the pharmacological interaction with fluconazole was also analysed using the checkerboard method. To analyse the possible mechanisms of action, flow cytometry assays were performed. The minimum inhibitory concentration obtained was 4-427 µg ml-1 for minocycline and 128-512 µg ml-1 for doxycycline, and mostly indifferent and additive interactions with fluconazole were observed. These tetracyclines were found to promote cellular alterations that generated death by apoptosis, with concentration-dependent reactive oxygen species production and reduced cell viability. Therefore, minocycline and doxycycline present themselves as promising study molecules against Candida spp.

A Simple Radioassay to Detect Nanoscale Membrane Disruption

Understanding the mechanisms and kinetics of membrane damage is of interest to researchers in several overlapping fields of biology. In this study, we describe the development and validation of a simple 32PO43- release radioassay used to track nanometer-scale damage to the bacterial cell membrane. Nanoscale membrane damage will result in the release of small cytoplasmic molecules, such as amino acids, sugars, and osmolytes. Our radioassay tracks the release of these molecules using the release of cytoplasmic 32PO43- as a proxy. Our assay can both detect 32PO43- release and track release kinetics in the order of minutes. We demonstrate the use of our radioassay using A. baumannii treated with colistin and Ω76: two agents known to cause membrane damage. Our assay tracks greater membrane damage in A. baumannii treated with both these agents, compared to an untreated control. Our assay fills a niche that is not covered by traditional 51Cr release radioassays and fluorescent staining techniques. Furthermore, our assay can potentially be used to track membrane damage in other membrane systems such as lipid vesicles, animal cells, and organelles.

Label-Free Sensing of Cell Viability Using a Low-Cost Impedance Cytometry Device

Cell viability is an essential physiological status for drug screening. While cell staining is a conventional cell viability analysis method, dye staining is usually cytotoxic. Alternatively, impedance cytometry provides a straightforward and label-free sensing approach for the assessment of cell viability. A key element of impedance cytometry is its sensing electrodes. Most state-of-the-art electrodes are made of expensive metals, microfabricated by lithography, with a typical size of ten microns. In this work, we proposed a low-cost microfluidic impedance cytometry device with 100-micron wide indium tin oxide (ITO) electrodes to achieve a comparable performance to the 10-micron wide Au electrodes. The effectiveness was experimentally verified as 7 μm beads can be distinguished from 10 μm beads. To the best of our knowledge, this is the lowest geometry ratio of the target to the sensing unit in the impedance cytometry technology. Furthermore, a cell viability test was performed on MCF-7 cells. The proposed double differential impedance cytometry device has successfully differentiated the living and dead MCF-7 cells with a throughput of ~1000 cells/s. The label-free and low-cost, high-throughput impedance cytometry could benefit drug screening, fundamental biological research and other biomedical applications.

Thyroid hormone-induced cell death in sea urchin metamorphic development

Thyroid hormones (THs) are important regulators of development, metabolism and homeostasis in metazoans. Specifically, they have been shown to regulate the metamorphic transitions of vertebrates and invertebrates alike. Indirectly developing sea urchin larvae accelerate the formation of juvenile structures in response to thyroxine (T4) treatment, while reducing their larval arm length. The mechanisms underlying larval arm reduction are unknown and we hypothesized that programmed cell death (PCD) is linked to this process. To test this hypothesis, we measured larval arm retraction in response to different THs (T4, T3, rT3, Tetrac) and assessed cell death in larvae using three different methods (TUNEL, YO-PRO-1 and caspase-3 activity) in the sea urchin Strongylocentrotus purpuratus. We also compared the extent of PCD in response to TH treatment before and after the invagination of the larval ectoderm, which marks the initiation of juvenile development in larval sea urchin species. We found that T4 treatment results in the strongest reduction of larval arms but detected a significant increase of PCD in response to T4, T3 and Tetrac in post-ingression but not pre-ingression larvae. As post-ingression larvae have initiated metamorphic development and therefore allocate resources to both larval and the juvenile structures, these results provide evidence that THs regulate larval development differentially via PCD. PCD in combination with cell proliferation likely has a key function in sea urchin development.

Host transmission dynamics of first- and third-stage Angiostrongylus cantonensis larvae in Bullastra lessoni

Given the importance of angiostrongyliasis as an emerging infectious disease of humans, companion animals, and wildlife, the current study focused on the transmission dynamics of first- and third-stage larvae of the parasitic nematode, Angiostrongylus cantonensis. The migration of infective larvae and their subsequent distribution within the Lymnaeidae snail, Bullastra lessoni, were investigated over time using microscopic examination of histological sections and fresh tissue. Snails were divided into four anatomical regions: (i) anterior and (ii) posterior cephalopedal masses, (iii) mantle skirt and (iv) visceral mass. The viability of free-swimming third-stage larvae, after their release from snail tissues, was evaluated in vitro by propidium iodide staining and infectivity by in vivo infection of Wistar rats. Snails were sequentially dissected over time to assess the number and anatomical distribution of larvae within each snail and hence infer their migration pathway. Herein, ongoing larval migratory activity was detected over 28 days post-infection. A comparison of infection rates and the larval distribution within the four designated snail regions demonstrated a significant relationship between anatomical region and density of infective larvae, with larvae mostly distributed in the anterior cephalopedal mass (43.6 ± 10.8%) and the mantle skirt (33.0 ± 8.8%). Propidium iodide staining showed that free-swimming third-stage larvae retained viability for between 4 and 8 weeks when stored under laboratory conditions. In contrast to viability, larval infectivity in rats remained for up to 2 weeks only. Knowledge gained from the current work could provide information on the development of new approaches to controlling the transmission of this parasite.

Recent progress in cytometric technologies and their applications in ecotoxicology and environmental risk assessment

Environmental toxicology focuses on identifying and predicting impact of potentially toxic anthropogenic chemicals on biosphere at various levels of biological organization. Presently there is a significant drive to gain deeper understanding of cellular and sub-cellular mechanisms of ecotoxicity. Most notable is increased focus on elucidation of cellular-response networks, interactomes, and greater implementation of cell-based biotests using high-throughput procedures, while at the same time decreasing the reliance on standard animal models used in ecotoxicity testing. This is aimed at discovery and interpretation of molecular pathways of ecotoxicity at large scale. In this regard, the applications of cytometry are perhaps one of the most fundamental prospective analytical tools for the next generation and high-throughput ecotoxicology research. The diversity of this modern technology spans flow, laser-scanning, imaging, and more recently, Raman as well as mass cytometry. The cornerstone advantages of cytometry include the possibility of multi-parameter measurements, gating and rapid analysis. Cytometry overcomes, thus, limitations of traditional bulk techniques such as spectrophotometry or gel-based techniques that average the results from pooled cell populations or small model organisms. Novel technologies such as cell imaging in flow, laser scanning cytometry, as well as mass cytometry provide innovative and tremendously powerful capabilities to analyze cells, tissues as well as to perform in situ analysis of small model organisms. In this review, we outline cytometry as a tremendously diverse field that is still vastly underutilized and often largely unknown in environmental sciences. The main motivation of this work is to highlight the potential and wide-reaching applications of cytometry in ecotoxicology, guide environmental scientists in the technological aspects as well as popularize its broader adoption in environmental risk assessment.

Fast Fluorescence Titration Quantification of Plasmid DNA with DNA Attractive Magnetic Nanoparticles

Fluorescence titration using magnetic nanoparticles (FTMN) was performed as a rapid, inexpensive, and simple method for quantifying the amount of fluorophore-intercalated plasmid DNA on these DNA attractive nanoparticles. Binding of the propidium iodide (PI)-intercalated DNA (PI/DNA) to polyethylenimine (PEI)-coated monodisperse iron oxide magnetic nanoparticles (PEI-MNs) was confirmed with transmission electron microscopy after the two species were mixed in water for less than a minute. The amount of DNA on PEI-MNs in aqueous solution, however, could not be easily determined using direct fluorescence measurements due to strong scattering by aggregated MNs, especially at high nanoparticle concentrations. Instead, fluorescence measurements were taken immediately after the solution of PI/DNA and PEI-MN mixtures was treated with a magnet to pull the PEI-MNs out of the solution. The detected fluorescence signal of the remaining free PI/DNA in the solution decreased as the concentration of PEI-MNs in the pre-treated solutions increased, resulting in a titration curve, which was used to determine the amount of DNA on MNs, the dissociation constant, and binding energy after the concentration of PEI-MNs was calibrated with microwave-plasma atomic emission spectroscopy. Quantitative polymerase chain reaction was used to understand the binding of DNA to MNs and to measure the amount of free PI/DNA in solution, and the results were similar to those obtained with the FTMN method.

Integration of Engineered "Spark-Cell" Spheroids for Optical Pacing of Cardiac Tissue

Optogenetic methods for pacing of cardiac tissue can be realized by direct genetic modification of the cardiomyocytes to express light-sensitive actuators, such as channelrhodopsin-2, ChR2, or by introduction of light-sensitized non-myocytes that couple to the cardiac cells and yield responsiveness to optical pacing. In this study, we engineer three-dimensional “spark cells” spheroids, composed of ChR2-expressing human embryonic kidney cells (from 100 to 100,000 cells per spheroid), and characterize their morphology as function of cell density and time. These “spark-cell” spheroids are then deployed to demonstrate site-specific optical pacing of human stem-cell-derived cardiomyocytes (hiPSC-CMs) in 96-well format using non-localized light application and all-optical electrophysiology with voltage and calcium small-molecule dyes or genetically encoded sensors. We show that the spheroids can be handled using liquid pipetting and can confer optical responsiveness of cardiac tissue earlier than direct viral or liposomal genetic modification of the cardiomyocytes, with 24% providing reliable stimulation of the iPSC-CMs within 6 h and >80% within 24 h. Moreover, our data show that the spheroids can be frozen in liquid nitrogen for long-term storage and transportation, after which they can be deployed as a reagent on site for optical cardiac pacing. In all cases, optical stimulation was achieved at relatively low light levels (<0.15 mW/mm²) when 5 ms or longer pulses were used. Our results demonstrate a scalable, cost-effective method with a cryopreservable reagent to achieve contactless optical stimulation of cardiac cell constructs without genetically modifying the myocytes, that can be integrated in a robotics-amenable workflow for high-throughput drug testing.

In Vitro Liver Toxicity Testing of Chemicals: A Pragmatic Approach

The liver is among the most frequently targeted organs by noxious chemicals of diverse nature. Liver toxicity testing using laboratory animals not only raises serious ethical questions, but is also rather poorly predictive of human safety towards chemicals. Increasing attention is, therefore, being paid to the development of non-animal and human-based testing schemes, which rely to a great extent on in vitro methodology. The present paper proposes a rationalized tiered in vitro testing strategy to detect liver toxicity triggered by chemicals, in which the first tier is focused on assessing general cytotoxicity, while the second tier is aimed at identifying liver-specific toxicity as such. A state-of-the-art overview is provided of the most commonly used in vitro assays that can be used in both tiers. Advantages and disadvantages of each assay as well as overall practical considerations are discussed.

Multi-frequency single cell electrical impedance measurement for label-free cell viability analysis

Cell viability is a physiological status connected to cell membrane integrity and cytoplasmic topography, which is profoundly important for fundamental biological research and practical biomedical applications. A conventional method for assessing cell viability is through cell staining analysis. However, cell staining involves laborious and complicated processing procedures and is normally cytotoxic. Intrinsic cellular phenotypes thus provide new avenues for measuring cell viability in a stain-free and non-toxic manner. In this work, we present a label-free non-destructive impedance-based approach for cell viability assessment by simultaneously characterizing multiple electrical cellular phenotypes in a high-throughput manner (>1000 cells per min). A novel concept called the complex opacity spectrum is introduced for improving the discrimination of live and dead cells. The analysis of the complex opacity spectrum leads to the discovery of two frequency ranges that are optimized for characterizing membranous and cytoplasmic electrical phenotypes. The present impedance-based approach has successfully discriminated between living and dead cells in two different experimental scenarios, including mixed living and dead cells in both homogenous and heterogeneous cell samples. This impedance-based single cell phenotyping technique provides highly accurate and consistent cell viability analysis, which has been validated by commercial fluorescence-based flow cytometry (∼1% difference) using heterogeneous cell samples. This label-free high-throughput cell viability analysis strategy will have broad applications in the field of biology and medicine.

Microscopic Analysis of Viral Infection

Viruses engineered to express fluorescent proteins can be used with live-cell imaging techniques to monitor the progression of infection in real time. Here we describe a set of methods to track infection spreading from one cell population to another as well as to visualize transfer of virions between cells. This approach is extended to multiplexing with physiological readouts of cell death, which can be correlated with single-cell resolution to viral infection.

Rapid determination of nematode cell and organ susceptibility to toxic treatments

In research focused on the intestine of parasitic nematodes, we recently identified small molecule inhibitors toxic to intestinal cells of larval Ascaris suum (nematode intestinal toxins/toxicants; “NITs”). Some NITs had anthelmintic activity across the phylogenetic diversity of the Nematoda. The whole-worm motility inhibition assay quantified anthelmintic activity, but worm responses to NITs in relation to pathology or affected molecular pathways was not acquired. In this study we extended this research to more comprehensively determine in whole larval A. suum the cells, organ systems, molecular targets, and potential cellular pathways involved in mechanisms of toxicity leading to cell death. The experimental system utilized fluorescent nuclear probes (bisbenzimide, propidium iodide), NITs, an A. suum larval parasite culture system and transcriptional responses (RNA-seq) to NITs. The approach provides for rapid resolution of NIT-induced cell death among organ systems (e.g. intestine, excretory, esophagus, hypodermis and seam cells, and nervous), discriminates among NITs based on cell death profiles, and identifies cells and organ systems with the greatest NIT sensitivity (e.g. intestine and apparent neuronal cells adjacent to the nerve ring). Application was extended to identify cells and organs sensitive to several existing anthelmintics. This approach also resolved intestinal cell death and irreparable damage induced in adult A. suum by two NITs, establishing a new model to elucidate relevant pathologic mechanisms in adult worms. RNA-seq analysis resolved A. suum genes responsive to treatments with three NITs, identifying dihydroorotate dehydrogenase (uridine synthesis) and RAB GTPase(s) (vesicle transport) as potential targets/pathways leading to cell death. A set of genes induced by all three NITs tested suggest common stress or survival responses activated by NITs. Beyond the presented specific lines of research, elements of the overall experimental system presented in this study have broad application toward systematic development of new anthelmintics.

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A unique rapid cell death assay was developed for parasitic nematodes.

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Multiple drug-like molecules cause widespread cell death in many organs of A. suum.

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Multiple cell and organ systems were validated as targets for anthelmintics.

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Potential drug targets/pathways were implicated in activating cell death processes.

Validation of a death assay for Angiostrongylus cantonensis larvae (L3) using propidium iodide in a rat model (Rattus norvegicus)

Angiostrongylus cantonensis is a pathogenic nematode and the cause of neuroangiostrongyliasis, an eosinophilic meningitis more commonly known as rat lungworm disease. Transmission is thought to be primarily due to ingestion of infective third stage larvae (L3) in gastropods, on produce, or in contaminated water. The gold standard to determine the effects of physical and chemical treatments on the infectivity of A. cantonensis L3 larvae is to infect rodents with treated L3 larvae and monitor for infection, but animal studies are laborious and expensive and also raise ethical concerns. This study demonstrates propidium iodide (PI) to be a reliable marker of parasite death and loss of infective potential without adversely affecting the development and future reproduction of live A. cantonensis larvae. PI staining allows evaluation of the efficacy of test substances in vitro, an improvement upon the use of lack of motility as an indicator of death. Some potential applications of this assay include determining the effectiveness of various anthelmintics, vegetable washes, electromagnetic radiation and other treatments intended to kill larvae in the prevention and treatment of neuroangiostrongyliasis.

Nuclear cytometry and chromatin organization

The nuclear-targeting chemical probe, for the detection and quantification of DNA within cells, has been a mainstay of cytometry-from the colorimetric Feulgen stain to smart fluorescent agents with tuned functionality. The level of nuclear structure and function at which the probe aims to readout, or indeed at which a DNA-targeted drug acts, is shadowed by a wide range of detection modalities and analytical methods. These methods are invariably limited in terms of the resolution attainable versus the volume occupied by targeted chromatin structures. The scalar challenge arises from the need to understand the extent and different levels of compaction of genomic DNA and how such structures can be re-modeled, reported, or even perturbed by both probes and drugs. Nuclear cytometry can report on the complex levels of chromatin order, disorder, disassembly, and even active disruption by probes and drugs. Nuclear probes can report defining features of clinical and therapeutic interest as in NETosis and other cell death processes. New cytometric approaches continue to bridge the scalar challenges of analyzing chromatin organization. Advances in super-resolution microscopy address the resolution and depth of analysis issues in cellular systems. Typical of recent insights into chromatin organization enabled by exploiting a DNA interacting probe is ChromEM tomography (ChromEMT). ChromEMT uses the unique properties of the anthraquinone-based cytometric dye DRAQ5™ to reveal that local and global 3D chromatin structures effect differences in compaction. The focus of this review is nuclear and chromatin cytometry, with linked reference to DNA targeting probes and drugs as exemplified by the anthracenediones.

Incubation of human sperm with micelles made from glycerophospholipid mixtures increases sperm motility and resistance to oxidative stress

Membrane integrity is essential in maintaining sperm viability, signaling, and motility, which are essential for fertilization. Sperm are highly susceptible to oxidative stress, as they are rich in sensitive polyunsaturated fatty acids (PUFA), and are unable to synthesize and repair many essential membrane constituents. Because of this, sperm cellular membranes are important targets of this process. Membrane Lipid Replacement (MLR) with glycerophospholipid mixtures (GPL) has been shown to ameliorate oxidative stress in cells, restore their cellular membranes, and prevent loss of function. Therefore, we tested the effects of MLR on sperm by tracking and monitoring GPL incorporation into their membrane systems and studying their effects on sperm motility and viability under different experimental conditions. Incubation of sperm with mixtures of exogenous, unoxidized GPL results in their incorporation into sperm membranes, as shown by the use of fluorescent dyes attached to GPL. The percent overall (total) sperm motility was increased from 52±2.5% to 68±1.34% after adding GPL to the incubation media, and overall sperm motility was recovered from 7±2% after H2O2 treatment to 58±2.5%)(n = 8, p<0.01) by the incorporation of GPL into sperm membranes. When sperm were exposed to H2O2, the mitochondrial inner membrane potential (MIMP), monitored using the MIMP tracker dye JC-1 in flow cytometry, diminished, whereas the addition of GPL prevented the decrease in MIMP. Confocal microscopy with Rhodamine-123 and JC-1 confirmed the mitochondrial localization of the dyes. We conclude that incubation of human sperm with glycerolphospholipids into the membranes of sperm improves sperm viability, motility, and resistance to oxidizing agents like H2O2. This suggests that human sperm might be useful to test innovative new treatments like MLR, since such treatments could improve fertility when it is adversely affected by increased oxidative stress.

An Image-based Assay for High-throughput Analysis of Cell Proliferation and Cell Death of Adherent Cells

In this protocol, we describe a method to monitor cell proliferation and death by live-cell imaging of propidium iodide (PI)-stained adherent mammalian cells. PI is widely used to assess cell death. However, it is usually used in end-point assays. Recently, we implemented the use of PI for real-time cell death assessment by automated imaging. Cells are seeded in a 96-well format, and after attachment, the treatments are added directly to the wells together with PI. Thereafter, cells are subjected to automated time-lapse imaging and quantification by computer software. Combined analyses of phase-contrast and fluorescence images allow assessment of treatment effects on cell proliferation as well as the extent and kinetics of cell death.

Applications and Caveats on the Utilization of DNA-Specific Probes in Cell-Based Assays

To perform cell-based assays using fluorescence as the readout there is a fundamental need to identify individual cellular objects. In the majority of cases this requires the addition of a DNA dye or so-called nuclear counterstain and these have become integral to assay design. End-point assays can use live or fixed cells and thus it is beneficial if such reagents are cell membrane-permeant.Further, membrane-permeant DNA dyes can open new opportunities in dynamic real time assays with caveats according to the impact of their interaction with the chromatin in live cells. As cell-based assays offer information on the in vitro toxicity of treatments, cell viability has become a basic readout and cell membrane-impermeant fluorescent DNA-specific dyes can provide this information.In the case of both nuclear counterstaining and viability reporting, it is beneficial if the DNA dyes employed are suitably spectrally separated to permit multi-color experimental design. Methods will be described for these two important assay readouts.

Comparative real-time study of cellular uptake of a formulated conjugated linolenic acid rich nano and conventional macro emulsions and their bioactivity in ex vivo models for parenteral applications

The objective of the present study was to fabricate and monitor real-time, impact of a stable conjugated linolenic acid, α-eleostearic acid (ESA) rich nanoemulsion (NE) formulation (d < 200 nm) vis-à-vis ESA conventional emulsion (CE) system in ex vivo systems against both endogenous and exogenous reactive oxygen species (ROS). Accordingly, stable nanoemulsion formulation of ESA was engineered with the aid of bitter melon seed oil and non-toxic excipients. Morphology and particle size of the emulsion formulations were studied to validate stability. The real-time rapid uptake of the ESA NE and its increased prophylactic efficacy against induced endogenous and exogenous ROS in terms of cell viability and membrane integrity was evaluated flow-cytometrically and with fluorescence microscopic analysis of different primary cells. It was found that the fabricated non-toxic ESA NE had stable parameters (hydrodynamic mean diameter, particle size distribution and zeta potential) for over 12 weeks. Further, ESA NE at a concentration of ∼ 70 μM exhibited maximum efficacy in protecting cells from oxidative damage against both endogenous and exogenous ROS in lymphocytes and hepatocytes as compared to its corresponding presence in the CE formulation. This study provides a real-time empirical evidence on the influence of nano formulation in enhancing bioavailability and antioxidative properties of ESA.

Reduced Intracellular Drug Accumulation in Drug-Resistant Leukemia Cells is Not Only Solely Due to MDR-Mediated Efflux but also to Decreased Uptake

Expression of ABC family transporter proteins that promote drug efflux from cancer cells is a widely observed mechanism of multi-drug resistance of cancer cells. Cell adaptation in long-term culture of HL60 leukemic cells in the presence of chemotherapy leads to induction and maintenance of the ABC transporters expression, preventing further accumulation of drugs. However, we found that decreased accumulation of drugs and fluorescent dyes also contributed by a reduced uptake by the resistant cells. Confocal time-lapse microscopy and flow cytometry revealed that fluid-phase endocytosis was diminished in drug-resistant cells compared to drug-sensitive cells. Drug uptake was increased by insulin co-treatment when cells were grown in methylcellulose and monitored under the microscope, but not when cultured in suspension. We propose that multi-drug resistance is not only solely achieved by enhanced efflux capacity but also by supressed intake of the drug, offering an alternative target to overcome drug resistance or potentiate chemotherapy.

In vitro methods of assessing ocular biocompatibility using THP-1-derived macrophages

Macrophages play an important role in the elimination of infections, the removal of debris and in tissue repair after infection and trauma. In vitro models that assess ocular biomaterials for toxicity typically focus on the effects of these materials on epithelial or fibroblast cells. This investigation evaluated known ocular toxins deposited on model materials for their effects on the viability and activation of macrophages. THP-1-derived macrophages were cultured onto silicone films (used as a base biomaterial) deposited with chemical toxins (benzalkonium chloride (BAK), zinc diethyldithiocarbamate (ZDEC) and lipopolysaccharide (LPS)). Utilizing three fluorescent dyes calcein, ethidium homodimer-1 (EthD-1) and annexin V, the viability of macrophages attached to the biomaterial was determined using confocal microscopy. Propidium iodide (PI) staining and alamarBlue® (resazurin) reduction were used to assess cell death and metabolic activity. CD14, CD16, CD33, CD45, and CD54 expression of adherent macrophages, were also evaluated to detect LPS activation of macrophages using flow cytometry. The sensitivity of this test battery was demonstrated as significant toxicity from treated surfaces with ZDEC (0.001-0.01%), and BAK (0.001%-0.1%) was detected. Also, macrophage activation could be detected by measuring CD54 expression after exposure to adsorbed LPS. These in vitro methods will be helpful in determining the toxicity potential of new ocular biomaterials.

Kinetic viability assays using DRAQ7 probe

Cell death within cell populations is a stochastic process where cell-to-cell variation in temporal progression through the various stages of cell death arises from asynchrony of subtle fluctuations in the signaling pathways. Most cell death assays rely on detection of the specific marker of cell demise at the end-point of cell culturing. Such an approach cannot account for the asynchrony and the stochastic nature of cell response to the death-inducing signal. There is a need therefore for rapid and high-throughput bioassays capable of continuously tracking viability of individual cells from the time of encountering a stress signal up to final stages of their demise. In this context, a new anthracycline derivative, DRAQ7, is gaining increasing interest as an easy-to-use marker capable of long-term monitoring of cell death in real-time. This novel probe neither penetrates the plasma membrane of living cells nor does it affect the cells' susceptibility to the death-inducing agents. However, when the membrane integrity is compromised, DRAQ7 enters cells undergoing demise and binds readily to nuclear DNA to report cell death. Here, we provide three sets of protocols for viability assays using DRAQ7 probe. The first protocol describes the innovative use of single-color DRAQ7 real-time assay to dynamically track cell viability. The second protocol outlines a simplified end-point DRAQ7 staining approach. The final protocol highlights the real-time and multiparametric apoptosis assay utilizing DRAQ7 dye concurrently with tetramethylrhodamine methyl ester (TMRM), the mitochondrial trans-membrane electrochemical potential (ΔΨm) sensing probe.

The cell's nucleolus: an emerging target for chemotherapeutic intervention

The transient nucleolus plays a central role in the up-regulated synthesis of ribosomal RNA (rRNA) to sustain ribosome biogenesis, a hallmark of aberrant cell growth. This function, in conjunction with its unique pathohistological features in malignant cells and its ability to mediate apoptosis, renders this sub-nuclear structure a potential target for chemotherapeutic agents. In this Minireview, structurally and functionally diverse small molecules are discussed that have been reported to either interact with the nucleolus directly or perturb its function indirectly by acting on its dynamic components. These molecules include all major classes of nucleic-acid-targeted agents, antimetabolites, kinase inhibitors, anti-inflammatory drugs, natural product antibiotics, oligopeptides, as well as nanoparticles. Together, these molecules are invaluable probes of structure and function of the nucleolus. They also provide a unique opportunity to develop novel strategies for more selective and therefore better-tolerated chemotherapeutic intervention. In this regard, inhibition of RNA polymerase-I-mediated rRNA synthesis appears to be a promising mechanism for killing cancer cells. The recent development of molecules targeted at G-quadruplex-forming rRNA gene sequences, which are currently undergoing clinical trials, seems to attest to the success of this approach.

Relationship between DNA damage response, initiated by camptothecin or oxidative stress, and DNA replication, analyzed by quantitative 3D image analysis

A method of quantitative analysis of spatial (3D) relationship between discrete nuclear events detected by confocal microscopy is described and applied in analysis of a dependence between sites of DNA damage signaling (γH2AX foci) and DNA replication (EdU incorporation) in cells subjected to treatments with camptothecin (Cpt) or hydrogen peroxide (H2O2). Cpt induces γH2AX foci, likely reporting formation of DNA double-strand breaks (DSBs), almost exclusively at sites of DNA replication. This finding is consistent with the known mechanism of induction of DSBs by DNA topoisomerase I (topo1) inhibitors at the sites of collisions of the moving replication forks with topo1-DNA "cleavable complexes" stabilized by Cpt. Whereas an increased level of H2AX histone phosphorylation is seen in S-phase of cells subjected to H2O2, only a minor proportion of γH2AX foci coincide with DNA replication sites. Thus, the increased level of H2AX phosphorylation induced by H2O2 is not a direct consequence of formation of DNA lesions at the sites of moving DNA replication forks. These data suggest that oxidative stress induced by H2O2 and formation of the primary H2O2-induced lesions (8-oxo-7,8-dihydroguanosine) inhibits replication globally and triggers formation of γH2AX at various distances from replication forks. Quantitative analysis of a frequency of DNA replication sites and γH2AX foci suggests also that stalling of replicating forks by Cpt leads to activation of new DNA replication origins. © 2013 International Society for Advancement of Cytometry.

Standard fluorescent imaging of live cells is highly genotoxic

Fluorescence microscopy is commonly used for imaging live mammalian cells. Here, we describe studies aimed at revealing the potential genotoxic effects of standard fluorescence microscopy. To assess DNA damage, a high throughput platform for single cell gel electrophoresis is used (e.g., the CometChip). Light emitted by three standard filters was studied: (a) violet light [340-380 nm], used to excite DAPI and other blue fluorophores, (b) blue light [460-500 nm] commonly used to image green fluorescent protein (GFP) and Calcein AM, and (c) green light [528-553 nm], useful for imaging red fluorophores. Results show that exposure of samples to light during imaging is indeed genotoxic even when the selected wavelengths are outside the range known to induce significant damage levels. Shorter excitation wavelengths and longer irradiation times lead to higher levels of DNA damage. We have also measured DNA damage in cells expressing enhanced GFP or stained with Calcein AM, a widely used green fluorophore. Data show that Calcein AM leads to a synergistic increase in the levels of DNA damage and that even cells that are not being directly imaged sustain significant DNA damage from exposure to indirect light. The nature of light-induced DNA damage during imaging was assessed using the Fpg glycosylase, an enzyme that enables quantification of oxidative DNA damage. Oxidative damage was evident in cells exposed to violet light. Furthermore, the Fpg glycosylase revealed the presence of oxidative DNA damage in blue-light exposed cells for which DNA damage was not detected using standard analysis conditions. Taken together, the results of these studies call attention to the potential confounding effects of DNA damage induced by standard imaging conditions, and identify wavelength, exposure time, and fluorophore as parameters that can be modulated to reduce light-induced DNA damage.

Multivariate analysis of apoptotic markers versus cell cycle phase in living human cancer cells by microfluidic cytometry

Measurement of apoptotic markers in tumors can be directly correlated with the cell cycle phase using flow cytometry (FCM). The conventional DNA content analysis requires cell permeabilization to stain nuclei with fluorescent probes such as propidium iodide or use of a costly UV-excitation line for Hoechst 33342 probe. The access to FCM is also still limited to centralized core facilities due to its inherent high costs and complex operation. This work describes development and proof-of-concept validation of a portable and user-friendly microfluidic flow cytometer (μFCM) that can perform multivariate real time analysis on live cells using sampling volumes as small as 10 microliters. The μFCM system employs disposable microfluidic cartridges fabricated using injection molding in poly(methylmethacrylate) transparent thermoplastic. Furthermore, the dedicated and miniaturized electronic hardware interface enables up to six parameter detection using a combination of spatially separated solid-state 473 (10 mW) and 640 nm (20 mW) lasers and x-y stage for rapid laser alignment adjustment. We provide new evidence that a simple 2D flow focusing on a chip is sufficient to measure cellular DNA content in live tumor cells using a far-red DNA probe DRAQ5. The feasibility of using the μFCM system for a dose-response profiling of investigational anti-cancer agents on human hematopoietic cancer cells is also demonstrated. The data show that μFCM can provide a viable novel alternative to conventional FCM for multiparameter detection of caspase activation and dissipation of mitochondrial inner membrane potential (ΔΨm) in relation to DNA content (cell cycle phase) in live tumor cells.

Real-time cell viability assays using a new anthracycline derivative DRAQ7®

The exclusion of charged fluorescent dyes by intact cells has become a well-established assay for determining viability of cells. In search for a noninvasive fluorescent probe capable of long-term monitoring of cell death in real-time, we evaluated a new anthracycline derivative DRAQ7. The novel probe does not penetrate the plasma membrane of living cells but when the membrane integrity is compromised, it enters and binds readily to nuclear DNA to report cell death. It proved to be nontoxic to a panel of cancer cell lines grown continuously for up to 72 h and did not induce any detectable DNA damage signaling when analyzed using laser scanning microscopy and flow cytometry. The DRAQ7 provided a sensitive, real-time readout of cell death induced by a variety of stressors such as hypoxia, starvation, and drug-induced cytotoxicity. The overall responses to anticancer agents and resulting pharmacological dose-response profiles were not affected by the growth of tumor cells in the presence DRAQ7. Moreover, we for the first time introduced a near real-time microflow cytometric assay based on combination of DRAQ7 and mitochondrial inner membrane potential (ΔΨ(m) ) sensitive probe TMRM. We provide evidence that this low-dosage, real-time labeling procedure provides multiparameter and kinetic fingerprint of anticancer drug action.

Cytometry of apoptosis. Historical perspective and new advances

Characteristic changes in cell morphology paralleled by the appearance of a multitude of molecular and biochemical markers occur during apoptosis. These changes vary depending on the cell type, mechanism of induction of apoptosis, and the time-window at which the process of apoptosis is analyzed. By virtue of the capability of rapid measurement of individual cells the flow- and imaging-cytometry become preferred technologies to detect, identify and record incidence of apoptosis in large cell populations. It also provided a valuable tool to investigate molecular mechanisms in field of necrobiology. This review outlines the progress in development of the most commonly used cytometric methods probing cells death based on analysis of fragmentation of DNA, activation of caspases, analysis of mitochondrial potential, alterations in plasma membrane structure and other features that characterize programmed cell death. This article is part of a Special Issue entitled "Apoptosis: Four Decades Later"

Tumor necrosis factor-α-induced mononuclear cell death may contribute to polymorphonuclear cell predominance in the cerebrospinal fluid of patients with bacterial meningitis

BACKGROUND

Bacterial meningitis is characterized by a marked predominance of polymorphonuclear leukocytes (PMNs: segmented granulocytes or neutrophils) in the cerebrospinal fluid (CSF), whereas aseptic meningitis is characterized by a predominance of mononuclear leukocytes (MNs: lymphocytes or monocytes). However, the pathophysiology of this predominance of PMNs in the CSF of patients with bacterial meningitis has never, to our knowledge, been clearly described.

METHODS

To investigate the predominant cell components of CSF from pediatric patients with bacterial meningitis, we investigated cell death in association with levels of tumor necrosis factor-alpha (TNF-α) in the CSF, using the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide) assay and flow cytometry.

RESULTS

The MTT assay of the CSF revealed that the PMNs had survived, while the MNs rapidly had undergone cell death. Although PMNs survived in CSF with high levels of TNF-α, PMN apoptosis was demonstrated with flow cytometry.

CONCLUSIONS

The present study suggests that the pathophysiology of PMN predominance in the CSF of patients in the acute phase of bacterial meningitis is related to the rapid cell death of MNs and the survival of PMNs brought about by high levels of TNF-α.

Red/far-red fluorescing DNA-specific anthraquinones for nucl:cyto segmentation and viability reporting in cell-based assays

The advent and wide use of image-based, high-content screening assay formats demands reliable solutions for cellular compartment segmentation to track critical events-for example, those reported by GFP fusions within cell cycle control pathways, signaling pathways, protein translocations, and those associated with drug-induced toxicity such as mitochondrial membrane depolarization, plasma membrane permeabilization, and reactive oxygen species. To meet this need, a series of nuclear/cytoplasmic discriminating probes has been developed: the supravital dyes DRAQ5™ and CyTRAK Orange™ and most recently the viability dye DRAQ7™. These are all spectrally compatible with GFP reporters offering new solutions in imaging and cytometry. As red/far-red emitting dyes, they provide convenient fluorescent emission signatures which are spectrally separated from the majority of commonly used reporter proteins (e.g., eGFP, YFP, mRFP), and a wide range of fluorescent tags such as Alexafluor 488, fluorescein, and Cy2 and fluorescent functional probes used to report cell health status or demark organellar structures. In addition, they are not excited by UV wavelengths thus avoiding complications of the frequently seen pharmacophore UV-autofluorescence in drug discovery. Conversely, their preferential red excitation reduces interference by biological sample autofluorescence. High water solubility and high-affinity DNA-binding properties provide a convenient means of stoichiometrically labeling cell nuclei in live cells without the aid of DMSO and can equally be used for fixed cells. Powerfully, they permit the simultaneous and differential labeling of both nuclear and cytoplasmic compartments in live and fixed cells to clearly render the precise location of cell boundaries which may be beneficial for quantitative expression measurements, cell-cell interactions, and most recently compound in vitro toxicology testing. In one case, DRAQ7™, the core structure has been chemically derivatized to render it intact-cell-membrane impermeant. This far-red viability dye can be more widely combined with other fluorescent reporters to reveal temporally separated events and shows negligible cytotoxicity as determined by sensitive bioassays.

Dynamic analyses reveal cytoprotection by RPE melanosomes against non-photic stress

PURPOSE

Isolated melanosomes are known to have antioxidant properties but whether the granules perform an antioxidant function within cells is unclear. The aim of this study was to determine whether retinal pigment epithelium (RPE) melanosomes are competent to protect cultured cells against non-photic oxidative stress induced by treatment with H(2)O(2).

METHODS

Porcine melanosomes, either untreated or irradiated with visible light to simulate age-related melanin photobleaching, were introduced by phagocytosis into ARPE-19 cells. Cells were treated with H(2)O(2) using two delivery methods: as a pulse, or by continuous generation following addition of glucose oxidase to the medium. Cell survival in melanosome-containing cells was compared to survival in cells containing phagocytosed control latex beads using two real-time cell death assays.

RESULTS

Following H(2)O(2) delivery by either method, greater resistance to critical concentrations of H(2)O(2) was seen for cells containing melanosomes than for cells containing beads. Melanosome-mediated protection manifested as a delay in the time of onset of cell death and a slower rate of cell death over time. Photobleaching diminished the stress resistance conferred by the pigment granules. Individual cells in co-cultures were differentially sensitive to oxidative stress depending upon their particle content. Additional features of the time course of the cell death response were revealed by the dynamic analyses conducted over hours post oxidant treatment.

CONCLUSIONS

The results show, for the first time, that melanosomes perform a cytoprotective function within cultured cells by acting as an antioxidant. The outcomes imply that melanosomes perform functions within RPE cells aside from those related to light irradiation, and also suggest that susceptibility to ubiquitous pro-oxidizing agents like H(2)O(2) is partly determined by discrete features of individual RPE cells such as their granule content.

Cell fixation in zinc salt solution is compatible with DNA damage response detection by phospho-specific antibodies

By virtue of superior preservation of proteins and nucleic acids the zinc salt-based fixatives (ZBF) has been proposed as an alternative to precipitants and cross-linking fixatives in histopathology. It was recently reported that ZBF is compatible with analysis of cell surface immunophenotype and detection of intracellular epitopes by flow cytometry. The aim of this study was to explore whether ZBF is also compatible with the detection of DNA damage response assessed by phospho-specific antibodies (Abs) detecting phosphorylation of the key proteins of that pathway. DNA damage in human pulmonary adenocarcinoma A549 cells was induced by treatment with the DNA topoisomerase I inhibitor camptothecin and phosphorylation of histone H2AX on Ser139 (γH2AX) and of ATM on Ser1981 was detected with phospho-specific Abs; cellular fluorescence was measured by laser scanning cytometry (LSC). The sensitivity and accuracy of detection of H2AX and ATM phosphorylation concurrent with the detection of DNA replication by EdU incorporation and "click chemistry" was found in ZBF fixed cells to be comparable to that of cell fixed in formaldehyde. The accuracy of DNA content measurement as evident from the resolution of DNA content frequency histograms of cells stained with DAPI was somewhat better in ZBF- than in formaldehyde-fixed cells. The pattern of chromatin condensation revealed by the intensity of maximal pixel of DAPI that allows one to identify mitotic and immediately post-mitotic cells by LSC was preserved after ZBF fixation. ZBF fixation was also compatible with the detection of γH2AX foci considered to be the hallmarks of induction of DNA double-strand breaks. Analysis of cells by flow cytometry revealed that ZBF fixation of lymphoblastoid TK6 cells led to about 60 and 33% higher intensity of the side and forward light scatter, respectively, compared to formaldehyde fixed cells.

Apoptosis goes on a chip: advances in the microfluidic analysis of programmed cell death

Recent years have brought enormous progress in cell-based lab-on-a-chip technologies, allowing dynamic studies of cell death with an unprecedented accuracy. As interest in the microfabricated technologies for cell-based bioassays is rapidly gaining momentum, we highlight the most promising technologies that provide a new outlook for the rapid assessment of programmed and accidental cell death and are applicable in drug discovery, high-content drug screening, and personalized clinical diagnostics.

Cytometry of DNA replication and RNA synthesis: Historical perspective and recent advances based on "click chemistry"

This review covers progress in the development of cytometric methodologies designed to assess DNA replication and RNA synthesis. The early approaches utilizing autoradiography to detect incorporation of (3) H- or (14) C-labeled thymidine were able to identify the four fundamental phases of the cell cycle G(1) , S, G(2) , and M, and by analysis of the fraction of labeled mitosis (FLM), to precisely define the kinetics of cell progression through these phases. Analysis of (3) H-uridine incorporation and RNA content provided the means to distinguish quiescent G(0) from cycling G(1) cells. Subsequent progress in analysis of DNA replication was based on the use of BrdU as a DNA precursor and its detection by the quenching of the fluorescence intensity of DNA-bound fluorochromes such as Hoechst 33358 or acridine orange as measured by flow cytometry. Several variants of this methodology have been designed and used in studies to detect anticancer drug-induced perturbations of cell cycle kinetics. The next phase of method development, which was particularly useful in studies of the cell cycle in vivo, including clinical applications, relied on immunocytochemical detection of incorporated halogenated DNA or RNA precursors. This approach however was hampered by the need for DNA denaturation, which made it difficult to concurrently detect other cell constituents for multiparametric analysis. The recently introduced "click chemistry" approach has no such limitation and is the method of choice for analysis of DNA replication and RNA synthesis. This method is based on the use of 5-ethynyl-2'deoxyuridine (EdU) as a DNA precursor or 5-ethynyluridine (EU) as an RNA precursor and their detection with fluorochrome-tagged azides utilizing a copper (I) catalyzed [3+2] cycloaddition. Several examples are presented that illustrate incorporation of EdU or EU in cells subjected to DNA damage detected as histone H2AX phosphorylation that have been analyzed by flow or laser scanning cytometry.

Dynamic analysis of drug-induced cytotoxicity using chip-based dielectrophoretic cell immobilization technology

Quantification of programmed and accidental cell death provides useful end-points for the anticancer drug efficacy assessment. Cell death is, however, a stochastic process. Therefore, the opportunity to dynamically quantify individual cellular states is advantageous over the commonly employed static, end-point assays. In this work, we describe the development and application of a microfabricated, dielectrophoretic (DEP) cell immobilization platform for the real-time analysis of cancer drug-induced cytotoxicity. Microelectrode arrays were designed to generate weak electro-thermal vortices that support efficient drug mixing and rapid cell immobilization at the delta-shape regions of strong electric field formed between the opposite microelectrodes. We applied this technology to the dynamic analysis of hematopoietic tumor cells that represent a particular challenge for real-time imaging due to their dislodgement during image acquisition. The present study was designed to provide a comprehensive mechanistic rationale for accelerated cell-based assays on DEP chips using real-time labeling with cell permeability markers. In this context, we provide data on the complex behavior of viable vs dying cells in the DEP fields and probe the effects of DEP fields upon cell responses to anticancer drugs and overall bioassay performance. Results indicate that simple DEP cell immobilization technology can be readily applied for the dynamic analysis of investigational drugs in hematopoietic cancer cells. This ability is of particular importance in studying the outcome of patient derived cancer cells, when exposed to therapeutic drugs, as these cells are often rare and difficult to collect, purify and immobilize.

Real-time flow cytometry for the kinetic analysis of oncosis

The standard method of distinguishing apoptotic and oncotic cells has been by microscopic analysis of nuclei and cell membrane morphology. Thus a rapid test for analyzing large numbers of cells in the study of cell necrobiology has not been possible until the recent advent of the Amnis Image-stream and real-time Lab-on-a-Chip technologies. An interesting difference between apoptosis and oncosis is that they are ATP dependent and independent processes, respectively. Here we describe an assay measuring real-time kinetic changes in the potential differences of the inner mitochondrial membrane (mmp) and the plasma membrane (pmp) in cells immediately before and after the addition of the inducing agent. Live cells were loaded with carbocyanine dye DiIC(1) (5) and bis-oxonol (DiBAC(4) (5)) to measure mmp and pmp in conjunction with annexin V-FITC and DAPI labeling for gating out annexin V binding cells and dead cells respectively. Live cells gave specific membrane signatures in response to apoptotic or oncotic reagents in real-time. Apoptosis showed little change in mmp and pmp signals over the course of 25 min, the mitochondria only showed a slight hyperpolarization. In contrast chemical treatment with oxidative phosphorylation blocker, sodium azide (SA) caused an immediate hyperpolarization spike followed by a complete abrogation of mmp over a 25 min time course. Treatment with SA (1%) also caused plasma membrane depolarization. Likewise detergent (0.01% Triton X-100) treatments also caused abrogation of mmp and depolarization of pmp. Whereas heat shock (42°C) treatment showed only a slight mitochondrial membrane potential depolarization. These flow cytometric observations were confirmed by confocal microscopy. This novel real-time kinetic assay measuring mitochondrial and plasma membrane potential changes has important implications in the field of cell necrobiology in that it allows the researcher to differentiate apoptotic and oncotic processes in an immediate manner for the first time.

Introduction A: recent advances in cytometry instrumentation, probes, and methods--review

Cytometric techniques are continually being improved, refined, and adapted to new applications. This chapter briefly outlines recent advances in the field of cytometry with the main focus on new instrumentations in flow and image cytometry as well as new probes suitable for multiparametric analyses. There is a remarkable trend for miniaturizing cytometers, developing label-free and fluorescence-free analytical approaches, and designing "intelligent" probes. Furthermore, new methods for analyzing complex data for extracting relevant information are reviewed.

Microfluidics: Emerging prospects for anti-cancer drug screening

Cancer constitutes a heterogenic cellular system with a high level of spatio-temporal complexity. Recent discoveries by systems biologists have provided emerging evidence that cellular responses to anti-cancer modalities are stochastic in nature. To uncover the intricacies of cell-to-cell variability and its relevance to cancer therapy, new analytical screening technologies are needed. The last decade has brought forth spectacular innovations in the field of cytometry and single cell cytomics, opening new avenues for systems oncology and high-throughput real-time drug screening routines. The up-and-coming microfluidic Lab-on-a-Chip (LOC) technology and micro-total analysis systems (μTAS) are arguably the most promising platforms to address the inherent complexity of cellular systems with massive experimental parallelization and 4D analysis on a single cell level. The vast miniaturization of LOC systems and multiplexing enables innovative strategies to reduce drug screening expenditures while increasing throughput and content of information from a given sample. Small cell numbers and operational reagent volumes are sufficient for microfluidic analyzers and, as such, they enable next generation high-throughput and high-content screening of anti-cancer drugs on patient-derived specimens. Herein we highlight the selected advancements in this emerging field of bioengineering, and provide a snapshot of developments with relevance to anti-cancer drug screening routines.