Acridine orange interaction with DNA: Effect of ionic strength

Barium Sulfate Nanocomposites for Bioimaging and Chemo-photothermal Therapy of Physiologically Aggravated Lung Adenocarcinoma Cells

Cancer is a complex disease that displays physiomorphological transformation in different surrounding microenvironments. Therefore, the single treatment modalities are relatively less effective, and their efficiency varies with tumor cell physiology, leading to the development of tumor resistance. Combinatorial therapeutic approaches, such as chemo-photothermal therapy, are promising for efficiently mitigating tumor progression irrespective of cancer physiology. Nanotechnology has played a significant role in this regard. Therefore, the present study reports the synthesis of poly(acrylic acid)-tetraethylene glycol (PAA-TEG)-coated BaSO4 nanoparticles (NPs) with enhanced solubility, dispersibility, and X-ray attenuation. Next, nanocomposites (NCs) are synthesized by loading BaSO4 NPs with the therapeutic drug triiodobenzoic acid (Tiba) and the photosensitizer IR780 using a lipid coating. These fabricated NCs are analyzed for dual-modal imaging (fluorescence and X-ray-based imaging) properties and chemo-phototherapeutic ability against two-dimensional (2D) and three-dimensional (3D) cultures of A549 cells. Furthermore, A549 cells are morphologically and physiologically aggravated into potent malignant cells using tobacco leaf extract (TE), and the variation in the therapeutic effect of NCs compared to cisplatin is determined. The synthesized NCs display enhanced encapsulation and excellent synergistic anticancer activity through the generation of reactive oxygen species (ROS), mitochondrial damage, and genotoxicity. Also, the NCs are more potent in inhibiting cancer cell growth than cisplatin, and their impact is unaltered in the presence or absence of TE pretreatment of A549 cells. The present study holds significant potential for various theranostic applications, which are highly desired for laparoscopic image-guided lung cancer therapy.

The dyeing effect of acridine orange for multiple plasmid systems is sensitive to temperature

The Goldview dyeing of the natural multiplasmid system of Lactobacillus plantarum PC518 was affected by temperature. The article want to identify the specific molecules that cause temperature sensitivity, then experiment on the universality of temperature sensitivity, and finally preliminarily analyze the influencing factors. At 5°C and 25°C, single pDNA, multiplasmid system, and linear DNA samples were electrophoretic on agarose gel prestained by Goldview 1, 2, 3, and acridine orange (AO), respectively. Eighteen vectors of Escherichia coli and two vectors shortened by cloning were mixed into multiplasmid systems with different member numbers, and then electrophoresis with AO staining was performed within the range of 5°C-45°C, with a linearized multiplasmid system as the control. The lane profiles (peaks) were captured with Image Lab 5.1 software. After electrophoresis, the nine-plasmid-2 system was dyed with AO solutions of different ionic strengths to detect the effect of ionic strength on temperature sensitivity. It was measured that the UV-visible absorption spectra of the nine-plasmid-2 system dissolved in AO solutions with different ionic strengths and pH. Further, a response surface model was constructed using Design-Expert.V8.0.6 software. The electrophoresis result showed that the multiplasmid system from L. plantarum PC518 stained by AO staining showed a weak band at 5°C and five bands at 25°C, which was similar to the result of staining with Goldview 1, 2, and 3. The synthetic nine-plasmid-1 system and nine-plasmid-2 system displayed different band numbers on the electrophoresis gel in the electrophoresis temperature range of 5°C-45°C, namely 3, 4, 6, 4, and 2 bands, as well as 2, 6, 7, 8, and 5 bands. Using the 1× Tris-acetate-EDTA (TAE)-AO solution, the poststaining results of the nine-plasmid-2 system in the temperature range of 5°C-45°C were 4, 6, 9, 9, and 7 bands, respectively. Further, using 5×, 10×, or 25× TAE buffer, the AO poststaining results at 5°C were 4, 2, and 1 bands, respectively. The ultraviolet spectral results from 5°C to 25°C showed that there was a significant difference (3.5 times) in the fluctuation amplitude at the absorption peak of 261.2 nm between 0× and 1-10× TAE-AO solution containing the nine-plasmid-2 system. Specifically, the fluctuation amplitudes of 0×, 1×, 5×, and 10× samples were 0.032, 0.109, 0.112, and 0.110, respectively. At the same time, using 1× and 10× TAE buffer, the AO-stained linear nine-plasmid-2 system remained stable and did not display temperature sensitivity. The response surface models of the AO-stained nine-plasmid-2 system intuitively displayed that the absorbance of the 1× TAE samples increased significantly with increasing temperature compared to the 0× TAE samples, regardless of the pH value. The findings confirmed a temperature-dependent effect in AO staining of natural or synthetic multiplasmid systems, with the optimum staining result occurring at 25°C. Ion strength was a necessary condition for the temperature sensitivity mechanism. This study layed the groundwork for further investigation into the reasons or underlying mechanisms of temperature sensitivity in AO staining of multiplasmid systems.

The Study of the Effect of Dimethylsulfoxide (or Diethylsulfoxide) on Quinine Sulfate-DNA Binding by UV-Vis and Steady-State Fluorescence Spectroscopies

The effect of dimethylsulfoxide (DMSO) and diethylsulfoxide (DESO) on binding between quinine sulfate (QS) and DNA was studied by virtue of UV-Vis absorption, steady-state fluorescence spectroscopies, and fluorescence polarization measurements. The binding constant was determined at three different temperatures and the values of standard Gibbs energy change, enthalpy and entropy of binding were determined. The mechanism of binding and the effect of sulfoxides on this process was revealed. The values of binding constant, fluorescence polarization and iodide quenching studies confirmed that the main binding mode in QS-DNA system is groove binding. Addition of sulfoxides does not change the binding mechanism. Moreover, with addition of sulfoxides binding constant increases due to the removal of water molecules from DNA grooves making them more available for QS molecules. To explain the effect of DMSO and DESO on QS-DNA binding the photophysical properties of QS in aqueous solutions of DMSO and DESO were also studied. On the basis of quantum yield of QS in water, DMSO and DESO the types of intermolecular interactions were discussed. The obtained results show that quantum yield of QS in sulfoxides is lower compared with that in water and aqueous solution of 0.1 M H2SO4. QS forms ground state complexes with both DMSO and DESO that are stronger fluorophores compared with free QS molecules.

Multiple-Monitor HPLC Assays for Rapid Process Development, In-Process Monitoring, and Validation of AAV Production and Purification

HPLC is established as a fast convenient analytical technology for characterizing the content of empty and full capsids in purified samples containing adeno-associated virus (AAV). UV-based monitoring unfortunately over-estimates the proportion of full capsids and offers little value for characterizing unpurified samples. The present study combines dual-wavelength UV monitoring with intrinsic fluorescence, extrinsic fluorescence, and light-scattering to extend the utility of HPLC for supporting development of therapeutic AAV-based drugs. Applications with anion exchange (AEC), cation exchange (CEC), and size exclusion chromatography (SEC) are presented. Intrinsic fluorescence increases sensitivity of AAV detection over UV and enables more objective estimation of empty and full capsid ratios by comparison of their respective peak areas. Light scattering enables identification of AAV capsids in complex samples, plus semiquantitative estimation of empty and full capsid ratios from relative peak areas of empty and full capsids. Extrinsic Picogreen fluorescence enables semiquantitative tracking of DNA with all HPLC methods at all stages of purification. It does not detect encapsidated DNA but reveals DNA associated principally with the exteriors of empty capsids. It also enables monitoring of host DNA contamination across chromatograms. These enhancements support many opportunities to improve characterization of raw materials and process intermediates, to accelerate process development, provide rapid in-process monitoring, and support process validation.

p53 Enhances Artemisia annua L. Polyphenols-Induced Cell Death Through Upregulation of p53-Dependent Targets and Cleavage of PARP1 and Lamin A/C in HCT116 Colorectal Cancer Cells

Plant-derived natural polyphenols exhibit anticancer activity without showing any noticeable toxicities to normal cells. The aim of this study was to investigate the role of p53 on the anticancer effect of polyphenols isolated from Korean Artemisia annua L. (pKAL) in HCT116 human colorectal cancer cells. We confirmed that pKAL induced reactive oxygen species (ROS) production, propidium iodide (PI) uptake, nuclear structure change, and acidic vesicles in a p53-independent manner in p53-null HCT116 cells through fluorescence microscopy analysis of DCF/PI-, DAPI-, and AO-stained cells. The pKAL-induced anticancer effects were found to be significantly higher in p53-wild HCT116 cells than in p53-null by hematoxylin staining, CCK-8 assay, Western blot, and flow cytometric analysis of annexin V/PI-stained cells. In addition, expression of ectopic p53 in p53-null cells was upregulated by pKAL in both the nucleus and cytoplasm, increasing pKAL-induced cell death. Moreover, Western bot analysis revealed that pKAL-induced cell death was associated with upregulation of p53-dependent targets such as p21, Bax and DR5 and cleavage of PARP1 and lamin A/C in p53-wild HCT116 cells, but not in p53-null. Taken together, these results indicate that p53 plays an important role in enhancing the anticancer effects of pKAL by upregulating p53 downstream targets and inducing intracellular cell death processes.

Molecular complexes of calf thymus DNA with various bioactive compounds: Formation and characterization

The interaction between biomacromolecules and ligands has attracted great interest because of their biological properties. Calf thymus DNA (ctDNA) can interact with bioactive compounds to form complexes. Here, ctDNA-ligand complexes were studied using fluorescence, absorption, and infrared spectroscopy, circular dichroism, ABTS assay and competitive displacement. The binding constants of bioactive compounds at the intercalative site of ctDNA ranked in order kaempferol > apigenin > quercetin > curcumin > riboflavin, while the binding constants at minor groove sites ranked quercetin > kaempferol > naringenin ~ apigenin > hesperetin > curcumin ~ resveratrol ~ riboflavin > caffeic acid. CtDNA maintained stable B-form with an enhancement of base stacking and a decrease of right-handed helicity in the presence of these bioactive compounds, except for hesperetin and caffeic acid. Bioactive compounds preferentially bound to guanine bases and tended to transfer into a more hydrophobic environment upon complexation with ctDNA. The DNA complexation did not affect the ABTS·⁺ scavenging capacity of quercetin, kaempferol, resveratrol and apigenin but increased the ones of naringenin, caffeic acid, curcumin, hesperetin and riboflavin. The data gathered here should be useful to understand the binding modes of DNA with ligands for their potential application in pharmaceutical and food industries.

In Vitro Studies on Therapeutic Potential of Probiotic Yeasts Isolated from Various Sources

The present study investigates the therapeutic properties of probiotic yeasts viz. Yarrowia lipolytica VIT-MN01, Kluyveromyces lactis VIT-MN02, Lipomyces starkeyi VIT-MN03, Saccharomycopsis fibuligera VIT-MN04 and Brettanomyces custersianus VIT-MN05. The antimutagenic activity of probiotic yeasts against the mutagens viz. Benzo[a]pyrene (B[a]P), and Sodium azide (SA) was tested. S. fibuligera VIT-MN04 showed highest antimutagenicity (75%). Binding ability on the mutagen acridine orange (AO) was tested and L. starkeyi VIT-MN03 was able to bind AO effectively (88%). The probiotic yeasts were treated with the genotoxins viz. 4-Nitroquinoline 1-Oxide (NQO) and Methylnitronitrosoguanidine (MNNG). The prominent changes in UV shift confirmed the reduction in genotoxic activity of S. fibuligera VIT-MN04 and L. starkeyi VIT-MN03, respectively. Significant viability of probiotic yeasts was noted after being exposed to mutagens and genotoxins. The adhesion capacity and anticancer activity were also assessed using Caco-2 and IEC-6 cell lines. Adhesion ability was found to be more in IEC-6 cells and remarkable antiproliferative activity was noted in Caco-2 cells compared to normal cells. Further, antagonistic activity of probiotic yeasts was investigated against S. typhimurium which was found to be more in S. fibuligera VIT-MN04 and L. starkeyi VIT-MN03. The inhibition of α-glucosidase and α-amylase activity confirmed the antidiabetic activity of probiotic yeasts. Antioxidant activity was also tested using standard assays. Therefore, based on the results, it can be concluded that probiotic yeasts can serve as potential therapeutic agents for the prevention and treatment of colon cancer, type 2 diabetes and gastrointestinal infections.

DNA Binding Characteristics and Protective Effects of Yellow Pigment from Freshly Cut Yam (Dioscorea opposita)

Yam yellow pigments (YP) are natural pigments formed during the storage of freshly cut yam (Dioscorea opposita) under certain conditions. The interaction of YP with calf thymus DNA (ctDNA) and its protective effect against DNA oxidative damage were investigated using multiple spectroscopic techniques, competitive binding experiments, viscosity measurements, and gel electrophoresis. Results showed that YP participated in intercalative binding with ctDNA. YP exhibited a protective effect against hydroxyl-induced DNA damage, which was attributed to the high hydroxyl radical scavenging activity of YP. Our findings improve our understanding of the mechanism of interaction between YP and ctDNA, and provide a theoretical basis for the application of YP in the food and drug industry.

Differential staining of peripheral nuclear chromatin with Acridine orange implies an A-form epichromatin conformation of the DNA

The chromatin observed by conventional electron microscopy under the nuclear envelope constitutes a single layer of dense 30–35 nm granules, while ∼30 nm fibrils laterally attached to them, form large patches of lamin-associated domains (LADs). This particular surface “epichromatin” can be discerned by specific (H2A+H2B+DNA) conformational antibody at the inner nuclear envelope and around mitotic chromosomes. In order to differentiate the DNA conformation of the peripheral chromatin we applied an Acridine orange (AO) DNA structural test involving RNAse treatment and the addition of AO after acid pre-treatment. MCF-7 cells treated in this way revealed yellow/red patches of LADs attached to a thin green nuclear rim and with mitotic chromosomes outlined in green, topologically corresponding to epichromatin epitope staining by immunofluorescence. Differentially from LADs, the epichromatin was unable to provide metachromatic staining by AO, unless thermally denatured at 94^oC. DNA enrichment in GC stretches has been recently reported for immunoprecipitated ∼ 1Kb epichromatin domains. Together these data suggest that certain epichromatin segments assume the relatively hydrophobic DNA A-conformation at the nuclear envelope and surface of mitotic chromosomes, preventing AO side dimerisation.  We hypothesize that epichromatin domains form nucleosome superbeads. Hydrophobic interactions stack these superbeads and align them at the nuclear envelope, while repulsing the hydrophilic LADs. The hydrophobicity of epichromatin explains its location at the surface of mitotic chromosomes and its function in mediating chromosome attachment to the restituting nuclear envelope during telophase.

Label-free microfluidic chip for the identification of mesothelial cell clusters in pleural effusion

The detection of tumor cells and clusters in pleural effusion assists in the diagnosis of lung cancer. The proportion of tumor cells and clusters to the total number of cells in each patient varies substantially due to individual differences and the severity of the disease. The identification of one tumor cell or cluster from a large number of pleural effusions is the main challenge for hydrothorax tumor cell detection techniques. In the present study, by using A549 lung cancer and Met-5A mesothelial cell lines, a label-free microfluidic chip based on cell cluster size was designed. By setting the parameters of the chip, individual cells and clusters were able to enter different microfluidic channels. Subsequent to non-specific staining, the recovered components were stained using acridine orange (AO). A charge-coupled device camera was used to captured images of the cell, and the features of these cells were analyzed in their R and G channels using Matlab software to establish the characteristics and finally differentiate between the tumor and non-tumor cell or clusters. According to the results, when inlet A and B were under a velocity of 10 and 8.5 ml/h, respectively, the tumor cell clusters were successfully collected through microfluidic channels III–V, with a recovery rate of ~80%. Subsequent to staining with AO, the feature values in the R and G channels were identified, and initial differentiation was achieved. The present study combined the microfluidic chip, which is based on cluster size, with a computer identification method for pleural effusion. The successful differentiation of tumor cell clusters from non-tumor clusters provides the basis for the identification of tumor clusters in hydrothorax.