Dye Acridine Orange Research Articles

Impact of Solvents, Magnesium Oxide and Aluminium Oxide Nanoparticles on the Photophysical Properties of Acridine Orange Dye

Absorption and fluorescence spectroscopy techniques were applied to investigate the photophysical characteristics of acridine orange (AO) dye in solvents that included distilled water, dimethyl sulfoxide (DMSO), acetone and ethanol in various concentrations (1×10-4–1×10-6) M. All of the samples were served at room temperature. The relationships between various parameters describing the strength of optical transitions in atoms and molecules were reviewed. This study expresses various viewpoints by describing how concentration and solvent affect the dye's absorption and fluorescence spectra. The absorption spectra of AO exhibit a band at (490 nm), except for DMSO, which shifts more towards red by 5 nm. The fluorescence spectra show a blue shift in AO aqueous solution around 6 nm until (0.5×10-4) M, followed by a red shift at around 7 nm at (1×10-6) M. There is a blue shift in (1×10-5) M for DMSO at around 4 nm, then a 10 nm red shift in higher concentrations as well as a 9 nm red shift in acetone and 6 nm in ethanol. Adding magnesium oxide nanoparticles (MgO NPs) quenched AO in both absorption and fluorescence spectra, whereas maximum fluorescence and intensity increased when aluminium oxide nanoparticles (Al2O3 NPs) were added to the solution. KEYWORDS Laser dye, absorption spectrum, fluorescence spectrum, MgO NPs, Al2O3 NPs

Adsorptive removal of acridine orange dye by green tea/copper-activated carbon nanoparticles (Gt/Cu-AC np)

Abstract Textile production is the rapidly growing industry in present days with dying as one of the most prominent operations involved. Dumping untreated wastewater from dye houses contaminate the local water bodies. Thus, dye removal is of great importance and recent applications using Green tea/Copper-Activated Carbon nano materials showed high dye adsorption ability. This work deals with the removal of acridine orange dye by using depleted green tea leaves and activated carbon, both in the form of nano sized particles combinedly as Green tea/Copper-Activated Carbon nanoparticles (Gt/Cu-AC np). These particles are characterized using SEM, XRD and FTIR analysis. The Experimental study for Adsorption of Acridine Orange Dye is carried out in batch process and concentration measurement is done by indirect measurement mode using UV Spectrophotometer at a wavelength of 400 nm range. Various parameters such as agitation time, agitation speed, Dosage of adsorbent (Gt/Cu-AC np), Initial concentration, and pH of acridine orange dye solution vs %Removal of acridine orange dye in solution is studied using plots, while maintaining other parameters constant when dealing with one. Using these plots different parameters are optimised to obtain 98% dye removal. Kinetics for acridine orange dye removal is studied and it is observed that the data best fits into pseudo second order kinetics. Adsorption Isotherm studies are carried out using Langmuir, Freundlich, and Temkin Adsorption isotherms, and it is observed that the experimental data follows a more likely Freundlich Adsorption Isotherm model with maximum adsorption capacity of 95.43 mg of Acridine orange adsorbed per gram of Green tea/Copper-Activated Carbon nanoparticles. (Gt/Cu-AC np).

Investigation of Catalytic Property of Plant Mediated Silver Nanoparticles as Degradation of Toxic Dyes in Water

Nowadays, silver nano-compounds mediated by plant materials are widely used material in daily life chemistry as well as across the industries, medical, electronics, ceramics, and in all research fields, because it has some specific characteristics such as non-toxic, inexpensive, nature-friendly, heat resistant, catalytic activity, high electric conductivity and so on. In the present work we reported the photo-catalytic dye degradation of green synthesized silver nanoparticles of size 43.75 nm by using the flowers extract of Rhododendron campanulatum tree. Synthesized AgNPs have worked as a strong nano-catalyst for the degradation of toxic dyes such as malachite green (MG), and acridine orange (AO). As a catalyst, synthesized AgNPs degraded the malachite green (MG) dye 47.22 % within 90 min, and acridine orange (AO) dye 66.16 % in 4 h of solar irradiation, while in the absence of nanocatalyst, MG and AO dye degraded upto 22.13 % in 90 min and 46.75 % in 4 h of photo-irradiation respectively. Synthesized nano material (AgNPs) may be applicable as a strong catalytic agent for the degradation of toxic dyes, water purifying agent as well as a good antioxidant agent.

Incorporation of Fluorescent Dyes in Electrospun Chitosan/Poly(ethylene oxide)

Polymeric films have been increasingly investigated due to the ease of miniaturization and integration in several sensor devices. Films obtained from the electrospinning technique have a controlled diameter and homogeneity, and substances can be incorporated into the polymeric network. Electrospinning fiber of chitosan (Ch) and poly(ethylene oxide) (PEO) was obtained from solutions prepared at different concentrations in acetic acid, and varying the distance and the voltage applied. The obtained films were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and UV-Visible specular reflectance spectra (UV-SRS). The best conditions for electrospinning were obtained for a 2% m/v (Ch + PEO) solution in the ratio 90:10% m/m (Ch:PEO), applied voltage of 18 kV, and 18 cm distance between the capillary tube and collector. Acridine orange, sodium fluorescein, and erythrosine fluorescence dyes were successfully incorporated into Ch:PEO films. The spectrofluorometric spectra of the films showed excitation and emission processes and the acridine orange film showed evidence of excimer formation by the presence of an excitation peak at 569 nm. Ch-PEO films with the incorporation of fluorescent dyes may well be used as flexible probes or sensors in colorimetric devices in biochemical applications.

Electron flow through NDH-1 complexes is the major driver of cyclic electron flow-dependent proton pumping in cyanobacteria

Cyclic electron flow (CEF) around photosystem I is vital to balancing the photosynthetic energy budget of cyanobacteria and other photosynthetic organisms. The coupling of CEF to proton pumping has long been hypothesized to occur, providing proton motive force (PMF) for the synthesis of ATP with no net cost to [NADPH]. This is thought to occur largely through the activity of NDH-1 complexes, of which cyanobacteria have four with different activities. While a much work has been done to understand the steady-state PMF in both the light and dark, and fluorescent probes have been developed to observe these fluxes in vivo, little has been done to understand the kinetics of these fluxes, particularly with regard to NDH-1 complexes. To monitor the kinetics of proton pumping in Synechocystis sp. PCC 6803, the pH sensitive dye Acridine Orange was used alongside a suite of inhibitors in order to observe light-dependent proton pumping. The assay was demonstrated to measure photosynthetically driven proton pumping and used to measure the rates of proton pumping unimpeded by dark ΔpH. Here, the cyanobacterial NDH-1 complexes are shown to pump a sizable portion of proton flux when CEF-driven and LEF-driven proton pumping rates are observed and compared in mutants lacking some or all NDH-1 complexes. It is also demonstrated that PSII and LEF are responsible for the bulk of light induced proton pumping, though CEF and NDH-1 are capable of generating ~40% of the proton pumping rate when LEF is inactivated.

GO/PAMAM as a High Capacity Adsorbent for Removal of Alizarin Red S: Selective Separation of Dyes

Adsorption of Alizarin Red S (ARS) on graphene oxide/poly(amidoamine) (GO/PAMAM) was studied at different ARS initial concentrations, temperatures, pHs, shaking rates and contact times. Adsorption sites of GO/PAMAM were phenolic -OHgroup of GO and amine groups (-NH2, -NH3+ and -NHR2+) of PAMAM dendrimer moieties of GO/PAMAM. At pH = 2 and 318 K, maximum adsorption capacity of the adsorbent was 1275.2 mg g-1 which is one of the highest capacity in the literature. Thus, GO/PAMAM in this work acted as a superadsorbent for ARS. At the incipient of adsorption, molecules were adsorbed on sites that was reaction-controlled step, (Ea = 114.5 kJ mol-1). Adsorption of on the remaining sites was diffusion-controlled. In alkaline media, two other types of ARS molecules were identified during that were adsorbed on and sites. Further increasing the pH of the solution, decreased the number these two sites and yielded a reduced adsorption capacity . Methylene blue (MB), thionine (Th), pyronin Y (PY), acridine orange (AO), methyl blue (MEB) and janus green (JG) dyes were selectively separated from their mixtures with ARS molecules using GO/PAMAM at pH of 2. The used adsorbent was recycled efficiently by using ethylenediamine very fast.

The vibronic absorption spectra and electronic states of acridine orange in aqueous solution

The time-dependent density functional theory (TD-DFT) was used to obtain vibronic absorption spectra of acridine orange dye (AO) in an aqueous solution that were in good agreement with the experiment. The protonated and neutral forms of the dye have been investigated. The results of calculations using various functionals and basis sets have been analyzed. The best agreement with experiment was given by the level of theory X3LYP/6-31G(d,p). AO molecular orbitals involved in electronic transitions due light absorption in the visible region of the spectrum have been obtained. The dipole moments and atomic charges of the ground and excited states of the AO molecule have been calculated. Maps of the electrostatic potential have been drawn. An insignificant photoinduced electron transfer was found in the central ring of the chromophore of the dye molecule. According to our calculations, the vibronic coupling and the Boltzmann distribution play a significant role in the absorption spectra of the AO.

Cytotoxicity and insulin resistance reversal ability of biofunctional phytosynthesized MgO nanoparticles.

The present study investigates the cytotoxicity of hexagonal MgO nanoparticles synthesized via Amaranthus tricolor leaf extract and spherical MgO nanoparticles synthesized via Amaranthus blitum and Andrographis paniculata leaf extracts. In vitro cytotoxicity analysis showed that the hexagonal MgO nanoparticles synthesized from A. tricolor extract demonstrated the least toxicity to both diabetic and non-diabetic cells at 600μl/ml dosage. The viability of the diabetic cells (3T3-L1) after incubation with varying dosages of MgO nanoparticles was observed to be 55.3%. The viability of normal VERO cells was 86.6% and this stabilized to about 75% even after exposure to MgO nanoparticles dosage of up to 1000μl/ml. Colorimetric glucose assay revealed that the A. tricolor extract synthesized MgO nanoparticles resulted in ~ 28% insulin resistance reversal. A reduction in the expression of GLUT4 protein at 54 KDa after MgO nanopaSrticles incubation with diabetic cells was observed via western blot analysis to confirm insulin reversal ability. Fluorescence microscopic analysis with propidium iodide and acridine orange dyes showed the release of reactive oxygen species as a possible mechanism of the cytotoxic effect of MgO nanoparticles. It was inferred that the synergistic effect of the phytochemicals and MgO nanoparticles played a significant role in delivering enhanced insulin resistance reversal capability in adipose cells.

Optimization of acridine orange loading on 1:1 layered clay minerals for fluorescence enhancement

As a cationic fluorescence dye acridine orange (AO) is commonly used in biology and biochemistry for DNA analyses. In this study the light absorption and fluorescence of AO after being sorbed on kaolinite (Kao) and halloysite (Hal) were investigated. In dilute systems with initial AO concentrations of 1×10−6 to 1×10−4M (0.3–25μmol/g loadings on Kao), both light absorption and fluorescence emission increased as the initial AO concentrations, thus, the amounts of AO sorbed increased. In contrast, the light absorption and fluorescence emission reached maxima at 1×10−5M (3μmol/g) for Hal. In concentrated systems with initial AO concentrations of 5×10−4–5×10−3M (22–57 and 50–126μmol/g AO sorption on Kao and Hal), significant fluorescence quenching was observed and the fluorescence intensity decreased as the initial AO concentrations, thus, the amounts of AO sorbed increased. The results suggested that to achieve maximal fluorescence emission, monomeric AO configuration on the solid surface is a necessity. The AO sorption was mostly attributed to cation exchange between protonated AO and exchangeable cations on Kao and Hal surfaces. As such, both cation exchange capacity and specific surface area of the minerals control the maximal fluorescence emission.

Identification of Pathways of A498 Human Kidney Carcinoma Cell Death under the Action of Gratiola officinalis L. Extract and Green Tea Flavonoids Using Fluorescence Imaging Techniques

Using fluorescence methods for visualization of human tumor cell apoptosis and necrosis in vitro, the antitumor effects of flavonoid-containing Gratiola officinalis L. and green tea extracts at ultralow concentrations on A498 human kidney carcinoma cells after 24 and 48 h were compared. Fluorescent dyes (propidium iodide and acridine orange) were used in the “living and dead” test, which made it possible to identify the total number of cells that died by necrosis and apoptosis, as well as cells in which apoptosis has started and apoptotic bodies or pycnosis of the nucleus were detected. Gratiola officinalis L. extract had the most pronounced cytostatic activity 48 h after exposure; the number of cells per field of view decreased by a factor of 1.5 compared with the control. Green tea extract at a concentration of 0.0288 mg/mL had the most pronounced cytotoxic activity; its manifestation was growing 48 h after exposure. Gratiola officinalis L. extract exhibited cytotoxic activity at lower concentrations (0.0036 mg/mL).

Utilization of Lignocellulosic Waste for Acridine Orange Uptake: Insights into Multiparameter Isotherms Modeling with ANN-Aimed Formulation

AbstractFor the first time, a comprehensive study of 35 multiparameter isotherm models was conducted to describe the dynamics of the adsorption of acridine orange (AO) dye on an abundantly availabl...

Vernonia calvoana Shows Promise towards the Treatment of Ovarian Cancer.

The treatment for ovarian cancers includes chemotherapies which use drugs such as cisplatin, paclitaxel, carboplatin, platinum, taxanes, or their combination, and other molecular target therapies. However, these current therapies are often accompanied with side effects. Vernonia calvoana (VC) is a valuable edible medicinal plant that is widespread in West Africa. In vitro data in our lab demonstrated that VC crude extract inhibits human ovarian cancer cells in a dose-dependent manner, suggesting its antitumor activity. From the VC crude extract, we have generated 10 fractions and VC fraction 7 (F7) appears to show the highest antitumor activity towards ovarian cancer cells. However, the mechanisms by which VC F7 exerts its antitumor activity in cancer cells remain largely unknown. We hypothesized that VC F7 inhibits cell proliferation and induces DNA damage and cell cycle arrest in ovarian cells through oxidative stress. To test our hypothesis, we extracted and fractionated VC leaves. The effects of VC F7 were tested in OVCAR-3 cells. Viability was assessed by the means of MTS assay. Cell morphology was analyzed by acridine orange and propidium iodide (AO/PI) dye using a fluorescent microscope. Oxidative stress biomarkers were evaluated by the means of lipid peroxidation, catalase, and glutathione peroxidase assays, respectively. The degree of DNA damage was assessed by comet assay. Cell cycle distribution was assessed by flow cytometry. Data generated from the MTS assay demonstrated that VC F7 inhibits the growth of OVCAR-3 cells in a dose-dependent manner, showing a gradual increase in the loss of viability in VC F7-treated cells. Data obtained from the AO/PI dye assessment revealed morphological alterations and exhibited characteristics such as loss of cellular membrane integrity, cell shrinkage, cell membrane damage, organelle breakdown, and detachment from the culture plate. We observed a significant increase (p < 0.05) in the levels of malondialdhyde (MDA) production in treated cells compared to the control. A gradual decrease in both catalase and glutathione peroxidase activities were observed in the treated cells compared to the control. Data obtained from the comet assay showed a significant increase (p < 0.05) in the percentages of DNA cleavage and comet tail length. The results of the flow cytometry analysis indicated VC F7 treatment caused cell cycle arrest at the S-phase checkpoint. Taken together, our results demonstrate that VC F7 exerts its anticancer activity by inhibiting cell proliferation, inducing DNA damage, and causing cell cycle arrest through oxidative stress in OVAR-3 cells. This finding suggests that VC F7 may be a potential alternative dietary agent for the prevention and/or treatment of ovarian cancer.

Alkaloid Extract of Equisetum arvense Plant Induce Apoptosis in MCF7 Cancer Cell Line

This study was conducted to detect the ability of an alkaloid extracted from Equisetum arvense to induce apoptosis on MCF7 cancer cells. The IC50 concentration was employed in these experiments (325 μg/ml at 24hr), it was obtained from studying the effect of the alkaloid extract on the growth inhibition of cancer cells after 24 hours of exposure. genes involved in apoptosis (P53, BAX, Caspase8, and Caspase9) were assessed on the mRNA level.besides that, a study for the cells morphological changes that occurred via apoptosis was carried out by staining with a mixture of two fluorescence dyes acridine orange and propidium iodide. Mitochondrial membrane potential was also assessed. The results showed that the expression level of apoptosis genes was elevated. Apoptosis like morphological changes was noticed in cellular membranes and nucleus. Apoptosis characterization of the mitochondria membrane was detected as well. These results revealed the capability of this alkaloid extract to induce apoptosis in this breast cancer cell line. This study confirmed the substantial cytotoxic and pro-apoptotic activity of Equisetum arvense alkaloid extract toward the studied cell line, which indicates the utility of this substance in anticancer therapy.

Effect of montmorillonite clay on the fluorescence resonance energy transfer between two cationic dyes Acridine Orange and Rhodamine B in solution

In this article the Fluorescence resonance energy transfer (FRET) between two important cationic dyes namely Acridine Orange (AO) and Rhodamine B (RhB) in aqueous solution in presence and absence of montmorillonite (MMT) is demonstrated. The energy transfer is also studied in ethanolic solution. Excited state energy migration is occurred from AO to RhB molecules and the extent of energy transfer efficiency linearly increases with increase in RhB concentration in the solution. Interestingly the incorporation of MMT clay significantly increases the energy transfer efficiencies between the dye pair in the solution but the nature of interaction depends on the clay concentrations studied in the present work. The nature of quenching of steady state fluorescence emission of AO in presence of RhB as well as MMT clay in the mixed ensemble is systematically investigated and further confirmed by Time-resolved fluorescence and temperature-dependent steady state fluorescence emission experiments. AO and RhB dye molecules formed ground state complex with MMT clay followed by static quenching. As the clay platelets successfully control the FRET efficiency and it is also well known that MMT clay can host wide diversity of molecular species therefore, the present studies may provide a new insight for the design and the development of FRET-based molecular sensors.

Elution-extrusion and back-extrusion counter-current chromatography using three-phase solvent system for separation of organic dye mixture

In the present study, high-speed counter-current chromatography with a three-phase solvent system composed of n-hexane-acetonitrile-400 mM ammonium sulfate (1:1:1, v/v) was developed to recover four mixed dyes (methyl green, acridine orange, Congo red and oil red O) with diverse polarities. As a result, four dyes were successfully separated in a single HSCCC run using a step-wise gradient elution. Then, elution-extrusion and back-extrusion counter-current chromatography were used to reduce the separation time and solvent consumption. Among them back-extrusion CCC can save more time. Thus, the present study provides an effective method for dye recycling.

Functionalized graphene-based polyamide thin film nanocomposite membranes for organic solvent nanofiltration

This work deals with the use of octadecylamine (ODA)-functionalized reduced graphene oxide (rGO) for thin film nanocomposite (TFN) membranes. The functionalization of rGO with ODA leads to graphene-based nanofillers, more hydrophobic than GO, and thus to the easier dispersion in the organic phase of the interfacial polymerization (IP) reaction carried out to produce polyamide (PA) TFN membranes. The performance of the new TFN membranes is evaluated by organic solvent nanofiltration (OSN) of alcoholic solutions containing dyes Acridine Orange (AO, MW 265 g·mol−1), Sunset Yellow (SY, MW 452 g·mol−1) and Rose Bengal (RB, MW 974 g·mol−1). The functionalized nature of the nanoparticles introduced into the hydrophilic PA layer allows an increase of the ethanol permeance from 2.8, 3.4 and 3.7 L·m−2·h−1·bar−1 for AO, SY and RB, respectively, corresponding to the bare thin film composite membrane (without rGO-ODA particles), to 4.3, 4.6 and 6.0 L·m−2·h−1·bar−1 for AO, SY and RB, respectively, for the rGO-ODA based TFN membrane. In fact, we hypothesize that the increase of the ethanol flux achieved with the use of rGO-ODA as a filler in TFN membranes is owing to a combination of the simultaneous presence of polar and non-polar groups from rGO-ODA nanosheets and the creation of still selective narrow gaps between these particles and the polyamide (PA).

Eco-biocompatibility of chitosan coated biosynthesized copper oxide nanocomposite for enhanced industrial (Azo) dye removal from aqueous solution and antibacterial properties

In the present study, the biogenic synthesis of an ecofriendly and non-toxic chitosan (CS) coated copper oxide NPs (CS-CuO nanocomposite) using Psidium guajava aqueous leaf extract. The biogenic synthesized CS-CuO nanocomposite was characterized by using UV–vis spectroscopy analysis (UV-Vis), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Field emission scanning electron microscopy with energy dispersive X-ray spectroscopy (FE-SEM-EDS), Dynamic light scattering (DLS), and Transmission electron microscopy (TEM). The prepared CS-CuO nanocomposite was evaluated for antibacterial activity by agar well diffusion method as well as minimum inhibitory concentrations (MIC) were assessed against both Gram-positive Streptococcus pneumoniae, Staphylococcus epidermidis and Gram-negative Escherichia coli, Proteus mirabilis with good inhibition effects on Gram-negative bacteria than the Gram-positive bacteria. The interaction of the CS-CuO nanocomposite with the bacterial membrane was visually observed by confocal laser scanning microscopy and the live/dead cells were differentiated by treatment with acridine orange and ethidium bromide dyes.

Biophysical characterisation of DNA origami nanostructures reveals inaccessibility to intercalation binding sites

Intercalation of drug molecules into synthetic DNA nanostructures formed through self-assembled origami has been postulated as a valuable future method for targeted drug delivery. This is due to the excellent biocompatibility of synthetic DNA nanostructures, and high potential for flexible programmability including facile drug release into or near to target cells. Such favourable properties may enable high initial loading and efficient release for a predictable number of drug molecules per nanostructure carrier, important for efficient delivery of safe and effective drug doses to minimise non-specific release away from target cells. However, basic questions remain as to how intercalation-mediated loading depends on the DNA carrier structure. Here we use the interaction of dyes YOYO-1 and acridine orange with a tightly-packed 2D DNA origami tile as a simple model system to investigate intercalation-mediated loading. We employed multiple biophysical techniques including single-molecule fluorescence microscopy, atomic force microscopy, gel electrophoresis and controllable damage using low temperature plasma on synthetic DNA origami samples. Our results indicate that not all potential DNA binding sites are accessible for dye intercalation, which has implications for future DNA nanostructures designed for targeted drug delivery.

Application of synthesized tetragonal structured zirconium oxide nanoparticle on victoria blue B and acridine orange dye

Zirconium oxide with the tetragonal phase was prepared from zirconium nitrate and urea by solution combustion method. Nano-photocatalyst zirconium oxide was investigated by XRD, SEM-EDAX, TEM, UV absorbance spectroscopy and specific surface area analysis. The distribution size of ZrO was found to be less than 17nm and was confirmed by XRD and TEM studies. Further the ZrO nano-photocatalyst confirms the tetragonal phase by XRD. EDAX reveals the formation of ZrO. The efficiency of ZrO nanoparticles in the photodegradation of victoria blue B and acridine orange dye under sunlight was investigated. The results reveal that the degradation efficiency was found to be 95.42% for VBB (at 0.030g/pH 6/1×10−4mol/dm3) and 92.52% for AO (at 0.035g/pH 4/1×10−4mol/dm3). Further the degradation efficiency shown highest in VBB dye when compare to AO dye. Therefore, the ZrO nanoparticle has been found to be suitable for the treatment of textile effluents.

Agaricus bisporus mediated biosynthesis of copper nanoparticles and its biological effects: An in-vitro study

Biofabrication of Copper nanoparticles (CuNPs) using Agaricus bisporus aqueous extract and its potential in-vitro biological activities were attempted in the present work. The synthesized CuNPs was confirmed by absorption peak at 551 nm using UV–Vis spectroscopy. The crystalline properties and the biofunctional groups involved in the reduction process were authenticated by XRD and FTIR spectroscopic techniques. Zeta potential value of −40 mV confirmed the stability of CuNPs. SEM and TEM analysis revealed agglomerated morphology and the presence of elemental Cu was confirmed by EDAX. In-vitro anti-bacterial assay demonstrated good bactericidal effects with more inhibitory action against Enterobacter aerogens (15 ± 0.08 mm). Anti-oxidant assays revealed potential scavenging effect against ABTS radical (82%); NO radical (76%) and DPPH radical (72%). Cytotoxic assay also revealed potential inhibitory effects against human colon cancer cell lines (SW620) with 60% cell viability recorded at 500 μg/ml concentration. Fluorescent microscopic observation of SW620 cells stained by DCFHDA and acridine orange dye displayed fragmentation, membrane loss and generation of ROS apoptotic features.