Binding Interactions of Toluidine Blue O with Escherichia Coli DNA: Formation of Bridged Structure

A multifunctional DNA tetrahedron for imaging, gene therapy, and chemotherapy-phototherapy combination: Binding affinity and anticancer activity

Imaging, silencing cancer-related microRNA, and chemotherapy-phototherapy (CTPT) combination therapy are crucial for cancer diagnosis and drug resistance overcoming. In this study, we designed a multifunctional DNA tetrahedron (MB-MUC1-TD) for the targeted delivery of combined daunorubicin (DAU) + toluidine blue O (TBO). The detection limit of miRNA-21 was determined to be 0.91 nM. The intercalation of DAU and TBO into MB-MUC1-TD was proved by spectroscopic and calorimetric methods. The thermodynamic parameters for the interactions of DAU and/or TBO with MB-MUC1-TD confirmed high drug loading. The first addition of TBO in the ternary system achieved a higher loading of both drugs and a more stable complex structure. Deoxyribonuclease I (DNase I) accelerated the release of DAU and/or TBO loaded in MB-MUC1-TD. Confocal laser scanning microscope demonstrated that MB-MUC1-TD exhibited good imaging ability for miRNA-21 to accurately identify cancer cells, and DAU/TBO was predominantly distributed within the nucleus of cancer cells. In vitro cytotoxicity showed better gene therapy efficacy of MB on MCF-7 cells, better biocompatibility of loaded DAU and TBO on LO2 cells, and stronger synergistic cytotoxicity of DAU + TBO on MCF-7/ADR cells. This study may establish a theoretical foundation for co-loading CTPT combination drugs based on multifunctional DNA nanostructures.

Effect of the combined binding of topotecan and catechin/protocatechuic acid to a pH-sensitive DNA tetrahedron on release and cytotoxicity: Spectroscopic and calorimetric studies

The therapeutic efficacy of chemotherapy drugs can be effectively improved through the dual effects of their combination with natural polyphenols and the delivery of targeted DNA nanostructures. In this work, the interactions of topotecan (TPT), (+)-catechin (CAT), or protocatechuic acid (PCA) with a pH-sensitive DNA tetrahedron (MUC1-TD) in the binary and ternary systems at pHs 5.0 and 7.4 were investigated by fluorescence spectroscopy and calorimetry. The intercalative binding mode of TPT/CAT/PC to MUC1-TD was confirmed, and their affinity was ranked in the order of PCA > CAT > TPT. The effects of the pH-sensitivity of MUC1-TD and different molecular structures of CAT and PCA on the loading, release, and cytotoxicity of TPT were discussed. The weakened interaction under acidic conditions and the co-loading of CAT/PCA, especially PCA, improved the release of TPT loaded by MUC1-TD. The targeting of MUC1-TD and the synergistic effect with CAT/PCA, especially CAT, enhanced the cytotoxicity of TPT on A549 cells. For L02 cells, the protective effect of CAT/PCA reduced the damage caused by TPT. The single or combined TPT loaded by MUC1-TD was mainly concentrated in the nucleus of A549 cells. This work will provide key information for the combined application of TPT and CAT/PCA loaded by DNA nanostructures to improve chemotherapy efficacy and reduce side effects.

Enhancing Phototoxicity in Human Colorectal Tumor Cells Through Nanoarchitectonics for Synergistic Photothermal and Photodynamic Therapies

Phototherapies are promising for noninvasive treatment of aggressive tumors, especially when combining heat induction and oxidative processes. Herein, we show enhanced phototoxicity of gold shell-isolated nanorods conjugated with toluidine blue-O (AuSHINRs@TBO) against human colorectal tumor cells (Caco-2) with synergic effects of photothermal (PTT) and photodynamic therapies (PDT). Mitochondrial metabolic activity tests (MTT) performed on Caco-2 cell cultures indicated a photothermal effect from AuSHINRs owing to enhanced light absorption from the localized surface plasmon resonance (LSPR). The phototoxicity against Caco-2 cells was further increased with AuSHINRs@TBO where oxidative processes, such as hydroperoxidation, were also present, leading to a cell viability reduction from 85.5 to 39.0%. The molecular-level mechanisms responsible for these effects were investigated on bioinspired tumor membranes using Langmuir monolayers of Caco-2 lipid extract. Polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS) revealed that the AuSHINRs@TBO incorporation is due to attractive electrostatic interactions with negatively charged groups of the Caco-2 lipid extract, resulting in the expansion of surface pressure isotherms. Upon irradiation, Caco-2 lipid extract monolayers containing AuSHINRs@TBO (1:1 v/v) exhibited ca. 1.0% increase in surface area. This is attributed to the generation of reactive oxygen species (ROS) and their interaction with Caco-2 lipid extract monolayers, leading to hydroperoxide formation. The oxidative effects are facilitated by AuSHINRs@TBO penetration into the polar groups of the extract, allowing oxidative reactions with carbon chain unsaturations. These mechanisms are consistent with findings from confocal fluorescence microscopy, where the Caco-2 plasma membrane was the primary site of the cell death induction process.

Gold nanoparticle-decorated earth-abundant clay nanotubes as catalyst for the degradation of phenothiazine dyes and reduction of 4-(4-nitrophenyl)morpholine

In the present work, halloysite nanotubes modified with gold nanoparticles (AuNPs-HNT) are successfully prepared by wet chemical method for the catalytic degradation of phenothiazine dyes (azure B (AZB) and toluidine blue O (TBO)) and also cleaner reduction of 4-(4-nitrophenyl)morpholine (4NM) in the sodium borohydride (NaBH4) media. The catalyst is formulated by modifying the HNT support with a 0.964% metal loading using the HNT supports modified with 3-aminopropyl-trimethoxysilane (APTMS) coupling agent to facilitate the anchoring sites to trap the AuNPs and to prevent their agglomeration/aggregation. The AuNPs-HNT catalyst is investigated for structural and morphological characterization to get insights about the formation of the catalyst for the effective catalytic reduction of dyes and 4NM. The microscopic studies demonstrate that AuNPs (2.75 nm) are decorated on the outer surface of HNT. The as-prepared AuNPs-HNT catalyst demonstrates AZB and TBO dye degradation efficiency up to 96% in 10 and 11 min, respectively, and catalytic reduction of 4NM to 4-morpholinoaniline (MAN) is achieved up to 97% in 11 min, in the presence of NaBH4 without the formation of any by-products. The pseudo-first-order rate constant (K1) value of the AuNPs-HNT catalyst for AZB, TBO, and 4NM were calculated to be 0.0078, 0.0055, and 0.0066 s-1, respectively. Moreover, the synthesized catalyst shows an excellent reusability with stable catalytic reduction for 7 successive cycles for both the dyes and 4NM. A plausible mechanism for the catalytic dye degradation and reduction of 4NM by AuNPs-HNT catalyst is proposed as well. The obtained results clearly indicate the potential of AuNPs-HNT as an efficient catalyst for the removal of dye contaminants from the aquatic environments and cleaner reduction of 4NM to MAN, insinuating future pharmaceutical applications.

Facile preparation of toluidine blue-loaded DNA nanogels for anticancer photodynamic therapy

Photodynamic therapy (PDT) provides an effective therapeutic option for different types of cancer in addition to surgery, radiation, and chemotherapy. The treatment outcome of PDT is largely determined by both the light and dark toxicity of photosensitizers (PSs), which can be technically improved with the assistance of a drug delivery system, especially the nanocarriers. Toluidine blue (TB) is a representative PS that demonstrates high PDT efficacy; however, its application is largely limited by the associated dark toxicity. Inspired by TB's noncovalent binding with nucleic acids, in this study, we demonstrated that DNA nanogel (NG) could serve as an effective TB delivery vehicle to facilitate anticancer PDT. The DNA/TB NG was constructed by the simple self-assembly between TB and short DNA segments using cisplatin as a crosslinker. Compared with TB alone, DNA/TB NG displayed a controlled TB-releasing behavior, effective cellular uptake, and phototoxicity while reducing the dark toxicity in breast cancer cells MCF-7. This DNA/TB NG represented a promising strategy to improve TB-mediated PDT for cancer treatments.

Host-assisted delivery of a model drug to genomic DNA: Key information from ultrafast spectroscopy and in silico study

Intended drug delivery to a target without adverse effect is one of the major criteria for its acceptance in real use. Herein, we have made an attempt to explore the delivery efficacy of SDS surfactant in a monomer and micellar stage during the delivery of model drug, Toluidine Blue (TB) from micellar cavity to DNA. Molecular recognition of pre-micellar SDS encapsulated TB with DNA occurs at a rate constant (k1~652 s-1). On the contrary, no significant release of encapsulated TB at micellar concentration was observed within the experimental time frame. This originated from the higher binding affinity of TB towards the nano cavity of SDS at micellar concentration which doesn't allow the delivery of TB from the nano cavity of SDS micelle to DNA. Thus, molecular recognition controls the extent of DNA recognition by TB which in turn modulates the rate of delivery of TB from SDS in a concentration dependent morphology.

Studies of eosin Y - DNA interaction using a competitive binding assay

The interaction between xanthene dye eosin Y and double stranded DNA has been studied by spectrophotometry. The conventional titration study does not show the interaction in the eosin Y - DNA system. Therefore, the competitive binding assay was carried out. The DNA-targeted ligands proflavine and methylene blue were used as competitors. Multivariate curve resolution - alternative least squares method (MCR-ALS) was applied to analyze the spectrophotometric titration data. The experimental binding isotherms were fitted by Scatchard and McGee equations. The binding constant of eosin Y with DNA was found to be 1.7·10⁴ M^-1. It is shown that the competitive binding assay requires consideration of heteroassociation for the correct determination of ligand-DNA binding parameters.

Role of Toluidine Blue-O Binding Mechanism for Photooxidation in Bioinspired Bacterial Membranes

The alarming increase in bacterial resistance to antibiotics has demanded new strategies for microbial inactivation, which include photodynamic therapy whose activity relies on the photoreaction damage to the microorganism membrane. Herein, the binding mechanisms of the photosensitizer toluidine blue-O (TBO) on simplified models of bacterial membrane with Langmuir monolayers of 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) and 1,2-dioleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (DOPG) were correlated to the effects of the photoinduced lipid oxidation. Langmuir monolayers of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) were also used as a reference of mammalian membranes. The surface pressure isotherms combined with polarization-modulated infrared reflection absorption spectroscopy revealed that TBO expands DOPC, DOPE, and DOPG monolayers owing to electrostatic interactions with the negatively charged groups in the phospholipids, with a stronger adsorption on DOPG, which has a net surface charge. Light irradiation made the TBO-containing DOPC and DOPE monolayers less unstable as a result of the singlet oxygen (¹O₂) reaction with the chain unsaturation and hydroperoxide formation. In contrast, the decreased stability of the irradiated TBO-containing DOPG monolayer suggests the cleavage of carbon chains. The anionic nature of DOPG allowed a deeper penetration of TBO into the chain region, favoring contact-dependent reactions between the excited triplet state of TBO and lipid unsaturations or/and hydroperoxide groups, which is the key for the cleavage reactions and further membrane permeabilization.

DNA-based bioassay of legionella pneumonia pathogen using gold nanostructure: A new platform for diagnosis of legionellosis

The specific diagnosis of hard-growing bacteria is one of the most important concerns of medical bacteriology. Legionella pneumophila is one of the most important bacteria in hard growth. In spite remarkable trends in bacteriology, now day, culture is the gold standard for detection of L. pneumophila. This work is an attempt to quantification of L. pneumophila bacteria using a bioassay. The fabrication of a new electrochemical DNA-based bioassay using gold nano architecture combined with as a transducer substrate combined with toluidine blue (TB) as a redox marker was performed successful. Also, the mixture of beta‑cyclodextrin and dopamine as Poly (dopamine‑β‑Cyclodextrin) was used to proper a biointerface for stabilization of gold nanoparticles optimum immobilize of pDNA sequence (5-SH-TCGA TAC TCT CCC CGC CCC TT T TGTATCGACG-3). So, a specific thiolated pDNA was immobilized on the transducer substrate and DNA hybridization was followed by C-DNA sequence (5-ACA AAA GGG GCG GGG AGA GTA-3) using square wave voltammetry and differential pulse voltammetry. At the optimum conditions, linear range was 1 μM to 1 ZM and low limit of quantification (LLOQ) was 1 Zepto-molar. L. pneumophila were sensitively distinguished by the planned DNA sensor. Finally, the engineered DNA based bioassay could be used for identifying the L. pneumophila samples from patients or environments.

In vitro interaction of cefotaxime with calf thymus DNA: Insights from spectroscopic, calorimetric and molecular modelling studies

Cefotaxime is third generation antibiotic with known therapeutic efficacy against bacterial infections including cerebral abscesses and bacterial meningitis. The β-lactam group of drugs are considered safest antibiotics. Many antibiotics directly interact with DNA and alter their expression profile. Thus, it is necessary to understand the binding mode and its relevance to drug activity and toxicity. There is considerably a remarkable focus on deciphering the binding mechanism of these therapeutic agents as DNA is one of the major target for wide range of drugs. Cefotaxime has been extensively studied for its pharmacological properties while its binding mode to DNA has not been explicated so far. In this study, we have unveiled the binding mechanism of cefotaxime to DNA by using various biophysical, thermodynamic and in silico techniques. UV-vis spectroscopy confirmed the formation cefotaxime-DNA complex along with a brief idea about the extent of interaction. Fluorescence spectroscopy yielded the values of various binding constants and explained mode of fluorescence quenching to be static. CD spectroscopy, thermal denaturation, KI quenching and viscosity measurement explained that cefotaxime is groove binder. Measuring the effect of ions on cefotaxime-DNA complex ensured that it does not bind to DNA electrostatically. Dye displacement experiments finally confirmed that cefotaxime binds to the minor groove of DNA. ITC gave the thermodynamic profile of this binding in which negative value of Gibb's free energy change revealed that the process is spontaneous. Molecular modelling finally strengthened our experimental results that cefotaxime was located in curved contour of minor groove of DNA. The findings support on safety of drug and may have a little interference on normal biological functions.

Clinical Approach of High Technology Techniques for Control and Elimination of Endodontic Microbiota

The main goal in endodontic treatment is to eradicate or at least reduce intraradicular microbial population to levels that are more compatible with periapical lesions healing process. Since endodontic infections are polymicrobial in nature, intraradicular survival of endodontic microbiota and their pathogenic properties are influenced by a combination of their virulence factors. The purpose of this article is to review the endodontic microbiota and their respective virulence attributes, as well as perform a literature review of the effects of disinfection procedures in the treatment of endodontic infections to gain best practices. Conventional technique for root canal preparation includes mechanical debridement and application of antimicrobial irrigants. Recently, laser irradiation has been used to enhance the results of root canal treatment through its thermal effect. To reduce thermal side effects, laser activated irrigation (LAI) and photon induced photoacoustic streaming (PIPS) were introduced. Antimicrobial photodynamic therapy (aPDT) by photochemical reaction uses light at a specific wavelength to activate a nontoxic photosensitizer (PS) in the presence of oxygen to produce cytotoxic products. Different PSs are used in dentistry including methylene blue (MB), toluidine blue O (TBO), indocyanine green (ICG) and curcumin. Among different options, ICG could be the best choice due to its peak absorption at wavelength of 808 nm, which coincides with the commercial diode laser devices. Also, this wavelength has more penetration depth compared to other wavelengths used in aPDT.

Unraveling the binding interaction of Toluidine blue O with bovine hemoglobin – a multi spectroscopic and molecular modeling approach

Toluidine blue O (TBO) is a cationic photosensitizer that belongs to the class of phenothiazinium dyes.

Synthesis, characterization and cyclic voltammetric study of copper(II) and nickel(II) polymer chelates

Graft copolymers based on dextran (Dx) and 2-acrylamido-2-methyl-1-propane sulphonic acid (AMPS) were synthesized by free radical initiated solution polymerization technique using ceric ammonium nitrate as initiator. These graft copolymers were used to prepare Cu(II) and Ni(II) chelates by reactions with Cu(II) and Ni(II) metal ions respectively. Graft copolymer and metal chelates were characterized by elemental analysis, intrinsic viscosity, FT-IR, scanning electron microscopy (SEM), atomic force microscopy (AFM), thermogravimetric analysis (TGA) and powder X-ray diffraction (XRD). Elemental analysis, intrinsic viscosity and FT-IR studies revealed the incorporation of metal ions to form metal chelates. SEM studies showed the change in morphology due to metal incorporation. From AFM studies it was observed that there was increase in Root mean square (RMS) roughness values in case of metal complexes. Metal chelates were observed to be thermally more stable than graft copolymer from TGA. UV-vis spectroscopy study revealed increase in absorbance values and cyclic voltammetric (CV) studies showed more than tenfold increase in redox current due to formation of Cu(II) and Ni(II) metal chelates. The binding constants of each complex determined by using UV-visible spectroscopy revealed that Cu(II) has more binding ability than Ni(II).

Age-related reduction of structural complexity in spleen hematopoietic tissue architecture in mice

The effects of aging on structural complexity in hematopoietic tissue are unknown. In this work, in a mouse experimental model, we report the age-related reduction of spleen hematopoietic tissue (SHT) complexity. Spleen tissue was obtained from the total of 64 male Swiss albino mice divided into 8 age groups: newborns (0 days old), 10 days, 20 days, 30 days, 120 days, 210 days, 300 and 390 days old. SHT was stained using conventional hematoxylin/eosin, and DNA-binding toluidine blue dyes. Fractal dimension as an indicator of cellular complexity, and lacunarity as indicator of tissue heterogeneity were determined based on the binarized SHT micrographs. Results indicate that fractal dimension of mice spleen hematopoietic tissue decreases with age, while lacunarity increases. These changes/trends have been detected in SHT stained both with toluidine blue and conventional hematoxylin/eosin. Fractal dimension was negatively correlated with lacunarity. The detected reduction in complexity suggests that age-related structural changes are present in mouse SHT both in general tissue architecture and progenitor cell DNA.

Spectroscopic studies on the binding interaction of phenothiazinium dyes toluidine blue O, azure A and azure B to DNA

In this study a detailed characterization of the binding aspects of three phenothiazinium dyes, toluidine blue O (TBO), azure A and azure B with herring testes DNA is presented employing spectroscopic techniques. The absorbance and fluorescence properties of these dyes have been remarkably modified upon binding with DNA and the interaction is manifested through noncooperative binding as revealed form non-linear Scatchard plots with negative slopes at all binding ratios. The binding clearly revealed the high preference of TBO to DNA followed by the other two dyes azure A and azure B. The affinity of TBO was higher by about two times than that of the azures. From the series of studies using absorption, steady-state emission, the effect of ferrocyanide ion-induced steady-state fluorescence quenching, fluorescence polarization anisotropy, circular dichroism, the mode of binding of these dyes to the DNA double helix has been substantiated to be principally intercalative in nature. The stoichiometry of the association of these dyes to DNA was determined by the continuous variation analysis of Job from fluorescence data. The conformational aspects of the interaction was delineated from circular dichroism studies wherein higher perturbation was observed with TBO. Hydrodynamic study using viscosity measurements of linear rod like DNA confirmed that the binding was intercalative and strongest for TBO and weaker for azure A and azure B. The utility of the present work lies in exploring the potential binding applicability of these dyes to DNA for their development as effective therapeutic agents.