Electrochemical studies of danthron and the DNA–danthron interaction

Gelatin-Encapsulated Tetrahedral DNA Nanostructure Enhances Cellular Internalization for Treating Noise-Induced Hearing Loss

Nanoparticle-based drug delivery strategies have emerged as a crucial avenue for comprehensive sensorineural hearing loss treatment. Nevertheless, developing therapy vectors crossing both biological and cellular barriers has encountered significant challenges deriving from various external factors. Herein, the rational integration of gelatin nanoparticles (GNPs) with tetrahedral DNA nanostructures (TDNs) to engineer a distinct drug-delivery nanosystem (designed as TDN@GNP) efficiently enhances the biological permeability and cellular internalization, further resolving the dilemma of noise-induced hearing loss via loading epigallocatechin gallate (EGCG) with anti-lipid peroxidation property. Rationally engineering of TDN@GNP demonstrates dramatic alterations in the physicochemical key parameters of TDNs that are pivotal in cell-particle interactions and promote cellular uptake through multiple endocytic pathways. Furthermore, the EGCG-loaded nanosystem (TDN-EGCG@GNP) facilitates efficient inner ear drug delivery by superior permeability through the biological barrier (round window membrane), maintaining high drug concentration within the inner ear. The TDN-EGCG@GNP actively overcomes the cell membrane, exhibiting hearing protection from noise insults via reduced lipid peroxidation in outer hair cells and spiral ganglion neurons. This work exemplifies how integrating diverse vector functionalities can overcome biological and cellular barriers in the inner ear, offering promising applications for inner ear disorders.

Epigallocatechin gallate-loaded tetrahedral DNA nanostructures as a novel inner ear drug delivery system

The study of drug delivery systems to the inner ear is a crucial but challenging field. The sensory organ (in the inner ear) is protected by the petrous bone labyrinth and the membranous labyrinth, both of which need to be overcome during the drug delivery process. The requirements for such a delivery system include small size, appropriate flexibility and biodegradability. DNA nanostructures, biomaterials that can arrange multiple functional components with nanometer precision, exhibit characteristics that are compatible with the requirements for inner ear drug delivery. Herein, we report the development of a novel inner ear drug delivery system based on epigallocatechin gallate (EGCG)-loaded tetrahedral DNA nanostructures (TDNs, EGCG@TDNs). The TDNs self-assembled via base-pairing of four single-stranded DNA constructs and EGCG was loaded into the TDNs through non-covalent interactions. Cy5-labeled TDNs (Cy5-TDNs) were significantly internalized by the House Ear Institute-Organ of Corti 1 cell line, and this endocytosis was energy-, clathrin-, and micropinocytosis-dependent. Cy5-TDNs penetrated the round window membrane (RWM) rapidly in vivo. Local application of EGCG@TDNs onto the RWM of guinea pigs in a single dose continuously released EGCG over 4 hours. Drug concentrations in the perilymph were significantly elevated compared with the administration of free EGCG at the same dose. EGCG@TDNs were found to have favorable biocompatibility and strongly affected the RSL3-induced down-regulation of GPX4 and the generation of reactive oxygen species, on the basis of 2',7'-dichlorodihydrofluorescein diacetate staining. JC-1 staining suggested that EGCG@TDNs successfully reversed the decrease in mitochondrial membrane potential induced by RSL-3 in vitro and rescued cells from apoptosis, as demonstrated by the analysis of Annexin V-FITC/PI staining. Further functional studies showed that a locally administered single-dose of EGCG@TDNs effectively preserved spiral ganglion cells in C57/BL6 mice after noise-induced hearing loss. Hearing loss at 5.6 and 8 kHz frequencies was significantly attenuated when compared with the control EGCG formulation. Histological analyses indicated that the administration of TDNs and EGCG@TDNs did not induce local inflammatory responses. These favorable histological and functional effects resulting from the delivery of EGCG by TDNs through a local intratympanic injection suggest potential for therapeutic benefit in clinical applications.

The Interaction between DNA and Three Intercalating Anthracyclines Using Electrochemical DNA Nanobiosensor Based on Metal Nanoparticles Modified Screen-Printed Electrode

The screen-printed electrodes have gained increasing importance due to their advantages, such as robustness, portability, and easy handling. The manuscript presents the investigation of the interaction between double-strand deoxyribonucleic acid (dsDNA) and three anthracyclines: epirubicin (EPI), idarubicin (IDA), and doxorubicin (DOX) by differential pulse voltammetry on metal nanoparticles modified by screen-printed electrodes. In order to investigate the interaction, the voltammetric signals of dsDNA electroactive bases were used as an indicator. The effect of various metal nanomaterials on the signals of guanine and adenine was evaluated. Moreover, dsDNA/PtNPs/AgNPs/SPE (platinum nanoparticles/silver nanoparticles/screen-printed electrodes) was designed for anthracyclines–dsDNA interaction studies since the layer-by-layer modification strategy of metal nanoparticles increases the surface area. Using the signal of multi-layer calf thymus (ct)-dsDNA, the within-day reproducibility results (RSD%) for guanine and adenine peak currents were found as 0.58% and 0.73%, respectively, and the between-day reproducibility results (RSD%) for guanine and adenine peak currents were found as 1.04% and 1.26%, respectively. The effect of binding time and concentration of three anthracyclines on voltammetric signals of dsDNA bases were also evaluated. The response was examined in the range of 0.3–1.3 ppm EPI, 0.1–1.0 ppm IDA and DOX concentration on dsDNA/PtNPs/AgNPs/SPE. Electrochemical studies proposed that the interaction mechanism between three anthracyclines and dsDNA was an intercalation mode.

The numerical probability of carcinogenicity to humans of some pharmaceutical drugs: Alkylating agents, topoisomerase inhibitors or poisons, and DNA intercalators

The nonclinical branch of regulatory pharmacology has traditionally relied on the sensitivity and specificity of regulatorily recommended bioassays. Nonetheless, any predictive testing (eg, safety pharmacology) with less than 100% sensitivity or 100% specificity is prone to deliver false positive or negative results (namely, outcomes discordant to the clinical gold standard). It was recently suggested that the statistics-based and regulatory pertinent "predictive values approach" (PVA) might help to reach a more predictive use of preclinical testing data. To resolve the associated probability of carcinogenicity to humans, the PVA was applied to 37 pharmaceuticals bearing inadequate epidemiological evidence of carcinogenicity, but identifiable as unequivocal mutagens. According to current knowledge, a 98.9% (or more) probability of carcinogenicity to humans was reckoned for those 37 genotoxic drugs. Accordingly, these pharmaceutical drugs might be either scientifically or regulatorily regarded as "carcinogenic to humans." In the USA, European Union, or Canada as examples, the great majority of these 37 pharmaceuticals are authorized for medical use in humans. From the results of the present appraisal, the following is suggested (1) for the pharmaceuticals listed in this report, to include significant carcinogenicity warnings in their prescribing information; (2) to conduct pharmacoepidemiology studies or risk-benefit analyses (if warranted), and (3) based on the respective risk-benefit analyses, to re-evaluate the authorization of hydralazine and phenoxybenzamine as antihypertensives, oxcarbazepine as an anticonvulsant, and phenazopyridine as a urinary tract antimicrobial or analgesic. For the four latter drugs (eg, phenoxybenzamine), a 99.5% probability of carcinogenicity to humans was estimated.

Anthraquinones quinizarin and danthron unwind negatively supercoiled DNA and lengthen linear DNA

The intercalating drugs possess a planar aromatic chromophore unit by which they insert between DNA bases causing the distortion of classical B-DNA form. The planar tricyclic structure of anthraquinones belongs to the group of chromophore units and enables anthraquinones to bind to DNA by intercalating mode. The interactions of simple derivatives of anthraquinone, quinizarin (1,4-dihydroxyanthraquinone) and danthron (1,8-dihydroxyanthraquinone), with negatively supercoiled and linear DNA were investigated using a combination of the electrophoretic methods, fluorescence spectrophotometry and single molecule technique an atomic force microscopy. The detection of the topological change of negatively supercoiled plasmid DNA, unwinding of negatively supercoiled DNA, corresponding to appearance of DNA topoisomers with the low superhelicity and an increase of the contour length of linear DNA in the presence of quinizarin and danthron indicate the binding of both anthraquinones to DNA by intercalating mode.

Photochemistry and electrochemistry of anticancer uracils

The redox mechanism and electronic absorption behavior of a commercial anticancer drug, 5-fluorouracil (5-FU) and two potential anticancer drugs, 2-thiouracil (2-TU) and dithiouracil (DTU) have been investigated in a wide pH range by UV-Vis spectroscopy, cyclic voltammetry and differential pulse voltammetry. The effect of electrolytes, substituents, successive sweeps and potential scan rate on the voltammetric response of uracils was examined. Organized structure-activity relationships of these drugs were established on the basis of the results obtained from electronic absorption spectroscopy and cyclic voltammetry. The electrode reaction mechanism was suggested using the experimentally determined electrochemical parameters. The DNA binding propensity of uracils was found greater than the classical intercalator, proflavin and clinically used drug, epirubicin. Moreover, the results obtained through ab initio calculations for the oxidation potential of the three uracil derivatives were found in good agreement with the electrochemical results.

Interaction of 2-(9H-purin-6-ylamino)-4-(methylthio) butanoic acid with human serum albumin: fluorescence and modeling studies

This study was designed to investigate the interaction between (S)-2-(9H-purin-6-ylamino)-4-(methylthio) butanoic acid (PYMBA) and human serum albumin (HSA) using fluorescence spectroscopy. The combination of UV absorption and molecular docking under simulative physiological conditions was also applied to comprehensively understand the binding mechanism of PYMBA to HSA. Fluorescence data indicated that PYMBA has a strong ability to quench the intrinsic fluorescence of HSA. The binding constants (K) at different temperatures, thermodynamic parameters including enthalpy change (DeltaH) and entropy change (DeltaS) of PYMBA-HSA were correlated to the relevant fluorescence data, which suggested that the hydrophobic force played a very important role for the PYMBA binding to the HSA. The experimental results were in agreement with the results obtained via a molecular docking study. The effects of other ions on the binding constants were also studied.

Voltammetric Behavior of o-Nitrophenol and Damage to DNA

The electrochemical behavior of o-nitrophenol was studied in detail with a glassy carbon electrode (GCE). The dependence of peak potential on pH indicated that equivalent electrons and protons were involved in the process of o-nitrophenol reduction. The interaction of o-nitrophenol with calf thymus DNA was investigated by adding DNA to the o-nitrophenol solution and by immobilizing DNA on GCE, respectively. The peak current decrement and peak potential shift in presence of DNA indicated that o-nitrophenol could interact with DNA. The result was demonstrated that the in situ DNA damage was detected by differential pulse voltammetry after the o-nitrophenol was electrochemically reduced.

Electrochemical studies of (−)-epigallocatechin gallate and its interaction with DNA

In this paper, an electrochemical investigation of (-)-epigallocatechin gallate (EGCG) and its interaction with DNA is presented. Via an electrochemical approach assisted by ultraviolet-visible (UV-Vis) spectroscopy, we propose that EGCG can intercalate into DNA strands forming a nonelectroactive complex, which results in the decrease of the anodic peak current of EGCG. Meanwhile, an electrochemical study with the DNA-Cu(II)-EGCG system shows that damage to DNA can be recognized electrochemically via the increase in the anodic peak current resulting from the oxidation of guanine and adenine bases. The damage can also be recognized spectrophotometrically via an increase in the 260 nm absorption band. In addition, it was found that EGCG is able to discriminate dsDNA from ssDNA, making a potential electrochemical indicator for the detection of DNA hybridization events. A rapid and convenient method of detecting EGCG was also developed in this work.