A Green Solvent Induced DNA Package

Toward Greater DNA Stability by Leveraging the Proton-Donating Ability of Protic Ionic Liquids

Deoxyribonucleic acid (DNA) stability is a prerequisite in many applications, ranging from DNA-based vaccines and data storage to gene therapy. However, the strategies to enhance DNA stability are limited, and the underlying mechanisms are poorly understood. Ionic liquids (ILs), molten salts of organic cations and organic/inorganic anions, are showing tremendous prospects in myriads of applications. With a judicious choice of constituent ions, the protic nature of ILs can be tuned. In this work, we investigate the relative stability of full-length genomic DNA in aqueous IL solutions of increasing protic nature. Our experimental measurements show that the protic ionic liquids (PILs) enhance the DNA melting temperature significantly while unaltering its native B-conformation. Molecular dynamics simulations and quantum mechanical calculation results suggest that the intramolecular Watson-Crick H-bonding in DNA remains unaffected and, in addition, the PILs induce stronger H-bonding networks in solution through their ability to make multiple intermolecular H-bonds with the nucleobases and among its constituent ions, thus aiding greater DNA stability. The detailed understanding obtained from this study could bring about the much-awaited breakthrough in improved DNA stability for its sustained use in the aforesaid applications!

Critical assessment of interactions between ct-DNA and choline-based magnetic ionic liquids: evidences of compaction

Ionic liquids (ILs) have become an alternative green solvent for storage and for stability of DNA. However, an in-depth understanding of binding and molecular interactions between ILs and DNA is needed. In this respect, magnetic ILs (MILs) are promising due to their tunable physicochemical properties. Various spectroscopic techniques and molecular simulations have been employed to unravel the critical factors of the strength and binding mechanism of MILs with DNA. UV-vis spectra unravel the multimodal binding of MILs with DNA, and the intrusion of IL molecules into the minor groove of DNA has been observed from dye displacement studies. Fluorescence correlation spectroscopic studies and scanning electron microscopy confirm the compaction of the DNA. ITC and molecular docking studies estimate the binding affinity of DNA with MILs, of ∼7 kcal mol-1. The 1 μs long-MD simulations give insight into the structural changes in the DNA in the MIL environment. Due to strong interaction with choline ions in the close vicinity, DNA helixes bend or squeeze in length and dilate in diameter (elliptical → spherical), leading to compaction. The post-MD parameters suggest a stronger interaction with [Ch]2[Mn] IL than with [Ch][Fe] IL; hence, the former induces DNA compaction to a more significant extent. Furthermore, decompaction is observed with the addition of sodium salts and is characterized using spectroscopic methods.

Synthesis of water-soluble novel bioactive pyridine-based azo coumarin derivative and competitive cytotoxicity, DNA binding, BSA binding study, and in silico analysis with coumarin

The diazo coupliling reaction of 3- amino pyridine with coumarin in water medium produces water soluble 6-[3-pyridyl]azocoumarin. The synthesised compound has been fully charecterised by IR, NMR, and Mass spectroscopy. The frontier molecular orbital calculations reveal that 6-[3-pyridyl]azocoumarin is more biologically and chemically active in comparison to coumarin. The cytotoxicity evaluation confirms that 6-[3-pyridyl]azocoumarin is more active than coumarin against human brain glioblastoma cell lines, LN-229 with IC50 value 9.09 μM (IC50 value for coumarin is 9.9 μM). The compound (I) has been synthesized by coupling of diazotized solution of 3-aminopyridine with coumarin in an aqueous medium at ∼ pH 10. The structure of the compound (I) has been characterized using UV-vis, IR, NMR, and Mass spectral studies. Frontier molecular orbital calculations reveal that 6-[3-pyridyl]azocoumarin (I) is more active chemically and biologically in comparison to coumarin. IC50 value 9.09 and 9.9 μM of 6-[3-pyridyl]azocoumarin and coumarin respectively obtained in cytotoxicity evaluation confirms the enhanced activity of the synthesized compound against human brain glioblastoma cell lines, LN-229. The synthesized compound also shows strong binding interactions with DNA and BSA in comparison with coumarin. The DNA binding study shows groove binding interaction of the synthesized compound with CT-DNA. The nature of interaction, binding parameters and structural variations of BSA in the presence of the synthesized compound and coumarin have been evaluated using several usefull spectroscopy approaches such as UV -Vis, time resolved and stady state flurescence. The molecular docking interaction has been carried out to justify the experimental binding interaction with DNA and BSA.

DNA nanotechnology in ionic liquids and deep eutectic solvents

Nucleic acids have the ability to generate advanced nanostructures in a controlled manner and can interact with target sequences or molecules with high affinity and selectivity. For this reason, they have applications in a variety of nanotechnology applications, from highly specific sensors to smart nanomachines and even in other applications such as enantioselective catalysis or drug delivery systems. However, a common disadvantage is the use of water as the ubiquitous solvent. The use of nucleic acids in non-aqueous solvents offers the opportunity to create a completely new toolbox with unprecedented degrees of freedom. Ionic liquids (ILs) and deep eutectic solvents (DESs) are the most promising alternative solvents due to their unique electrolyte and solvent roles, as well as their ability to maintain the stability and functionality of nucleic acids. This review aims to be a comprehensive, critical, and accessible evaluation of how much this goal has been achieved and what are the most critical parameters for accomplishing a breakthrough.

Assessing the Suitability of a Dicationic Ionic Liquid as a Stabilizing Material for the Storage of DNA in Aqueous Medium

The present study has been undertaken with an objective to find out a suitable medium for the long-term stability and storage of the ct-DNA structure in aqueous solution. For this purpose, the potential of a pyrrolidinium-based dicationic ionic liquid (DIL) in stabilizing ct-DNA structure has been investigated by following the DNA-DIL interaction. Additionally, in order to understand the fundamental aspects regarding the DNA-DIL interaction in a comprehensive manner, studies are also done by employing structurally similar monocationic ionic liquids (MILs). The investigations have been carried out both at ensemble-average and single molecular level by using various spectroscopic techniques. The molecular docking study has also been performed to throw more light into the experimental observations. The combined steady-state and time-resolved fluorescence, fluorescence correlation spectroscopy, and circular dichroism measurements have demonstrated that DILs can effectively be used as better storage media for ct-DNA as compared to MILs. Investigations have also shown that the extra electrostatic interaction between the cationic head group of DIL and the phosphate backbone of DNA is primarily responsible for providing better stabilization to ct-DNA, retaining its native structure in aqueous medium. The outcomes of the present study are also expected to provide valuable insights in designing new polycationic IL systems that can be used in nucleic acid-based applications.

Synthesis and Evaluation of Antiproliferative Activity, Topoisomerase IIα Inhibition, DNA Binding and Non-Clinical Toxicity of New Acridine-Thiosemicarbazone Derivatives

In this study, we report the synthesis of twenty new acridine–thiosemicarbazone derivatives and their antiproliferative activities. Mechanisms of action such as the inhibition of topoisomerase IIα and the interaction with DNA have been studied for some of the most active derivatives by means of both in silico and in vitro methods, and evaluations of the non-clinical toxicities (in vivo) in mice. In general, the compounds showed greater cytotoxicity against B16-F10 cells, with the highest potency for DL-08 (IC₅₀ = 14.79 µM). Derivatives DL-01 (77%), DL-07 (74%) and DL-08 (79%) showed interesting inhibition of topoisomerase IIα when compared to amsacrine, at 100 µM. In silico studies proposed the way of bonding of these compounds and a possible stereoelectronic reason for the absence of enzymatic activity for CL-07 and DL-06. Interactions with DNA presented different spectroscopic effects and indicate that the compound CL-07 has higher affinity for DNA (Kb = 4.75 × 10⁴ M⁻¹; Ksv = 2.6 × 10³ M⁻¹). In addition, compounds selected for non-clinical toxicity testing did not show serious signs of toxicity at the dose of 2000 mg/kg in mice; cytotoxic tests performed on leukemic cells (K-562) and its resistant form (K-562 Lucena 1) identified moderate potency for DL-01 and DL-08, with IC₅₀ between 11.45 and 17.32 µM.

Mo(VI) Potential Metallodrugs: Explaining the Transport and Cytotoxicity by Chemical Transformations

The transport and cytotoxicity of molybdenum-based drugs have been explained with the concept of chemical transformation, a very important idea in inorganic medicinal chemistry that is often overlooked in the interpretation of the biological activity of metal-containing systems. Two monomeric, [MoO₂(L¹)(MeOH)] (1) and [MoO₂(L²)(EtOH)] (2), and two mixed-ligand dimeric Mo^VIO₂ species, [{MoO₂(L^1-2)}₂(μ-4,4'-bipy)] (3-4), were synthesized and characterized. The structures of the solid complexes were solved through SC-XRD, while their transformation in water was clarified by UV-vis, ESI-MS, and DFT. In aqueous solution, 1-4 lead to the penta-coordinated [MoO₂(L^1-2)] active species after the release of the solvent molecule (1 and 2) or removal of the 4,4'-bipy bridge (3 and 4). [MoO₂(L^1-2)] are stable in solution and react with neither serum bioligand nor cellular reductants. The binding affinity of 1-4 toward HSA and DNA were evaluated through analytical and computational methods and in both cases a non-covalent interaction is expected. Furthermore, the in vitro cytotoxicity of the complexes was also determined and flow cytometry analysis showed the apoptotic death of the cancer cells. Interestingly, μ-4,4'-bipy bridged complexes 3 and 4 were found to be more active than monomeric 1 and 2, due to the mixture of species generated, that is [MoO₂(L^1-2)] and the cytotoxic 4,4'-bipy released after their dissociation. Since in the cytosol neither the reduction of Mo^VI to Mo^V/IV takes place nor the production of reactive oxygen species (ROS) through Fenton-like reactions of 1-4 with H₂O₂ occurs, the mechanism of cytotoxicity should be attributable to the direct interaction with DNA that happens with a minor-groove binding which results in cell death through an apoptotic mechanism.

Binding of tetrabutylammonium bromide based deep eutectic solvent to DNA by spectroscopic analysis

The binding characteristics of DNA in deep eutectic solvents (DESs), particularly the binding energy and interaction mechanism, are not widely known. In this study, the binding of tetrabutylammonium bromide (TBABr) based DES of different hydrogen bond donors (HBD), including ethylene glycol (EG), glycerol (Gly), 1,3-propanediol (1,3-PD) and 1,5-pentanediol (1,5-PD), to calf thymus DNA was investigated using fluorescence spectroscopy. It was found that the shorter the alkyl chain length (2 carbons) and higher EG ratios of TBABr:EG (1:5) increased the binding constant (K_b) between DES and DNA up to 5.75 × 10⁵ kJ mol^-1 and decreased the binding of Gibbs energy (ΔG^o) to 32.86 kJ mol^-1. Through displacement studies, all synthesised DESs have been shown to displace DAPI (4',6-diamidino-2-phenylindole) and were able to bind on the minor groove of Adenine-Thymine (AT)-rich DNA. A higher number of hydroxyl (OH) groups caused the TBABr:Gly to form more hydrogen bonds with DNA bases and had the highest ability to quench DAPI from DNA, with Stern-Volmer constants (K_sv) of 115.16 M^-1. This study demonstrated that the synthesised DESs were strongly bound to DNA through a combination of electrostatic, hydrophobic, and groove binding. Hence, DES has the potential to solvate and stabilise nucleic acid structures.

Ionic liquids: prospects for nucleic acid handling and delivery

Operations with nucleic acids are among the main means of studying the mechanisms of gene function and developing novel methods of molecular medicine and gene therapy. These endeavours usually imply the necessity of nucleic acid storage and delivery into eukaryotic cells. In spite of diversity of the existing dedicated techniques, all of them have their limitations. Thus, a recent notion of using ionic liquids in manipulations of nucleic acids has been attracting significant attention lately. Due to their unique physicochemical properties, in particular, their micro-structuring impact and tunability, ionic liquids are currently applied as solvents and stabilizing media in chemical synthesis, electrochemistry, biotechnology, and other areas. Here, we review the current knowledge on interactions between nucleic acids and ionic liquids and discuss potential advantages of applying the latter in delivery of the former into eukaryotic cells.

Insights on the DNA Stability in Aqueous Solutions of Ionic Liquids

Deoxyribonucleic acid (DNA) carries the genetic information essential for the growth and functioning of living organisms, playing a significant role in life sciences research. However, the long-term storage and preservation of DNA, while ensuring its bioactivity, are still current challenges to overcome. In this work, aqueous solutions of ionic liquids (ILs) were investigated as potential preservation media for double stranded (dsDNA). A screening of several ILs, by combining the cholinium, tetrabutylammonium, tetrabutylphosphonium, and 1-ethyl-3-methylimidazolium, cations with the anions bromide, chloride, dihydrogen phosphate, acetate, and glycolate, was carried out in order to gather fundamental knowledge on the molecular features of ILs that improve the dsDNA stability. Different IL concentrations and the pH effect were also addressed. Circular dichroism (CD) spectroscopy was used to evaluate the conformational structure and stability of dsDNA. IL-DNA interactions were appraised by UV-Vis absorption spectrophotometry and ³¹P nuclear magnetic resonance (NMR) spectroscopy. The results obtained demonstrate that pH has a significant effect towards the dsDNA stability. Amongst the ILs investigated, cholinium-based ILs are the most promising class of ILs to preserve the dsDNA structure, in which electrostatic interactions between the cholinium cation and the DNA phosphate groups play a significant role as demonstrated by the ³¹P NMR data, being more relevant at higher IL concentrations. On the other hand, the denaturation of dsDNA mainly occurs with ILs composed of more hydrophobic cations and able to establish dispersive interactions with the nucleobases environment. Furthermore, the IL anion has a weaker impact when compared to the IL cation effect to interact with DNA molecules. The experimental data of this work provide relevant fundamental knowledge for the application of ILs in the preservation of nucleic acids, being of high relevance in the biotechnology field.

Threading Intercalator-Induced Nanocondensates and Role of Endogenous Metal Ions in Decondensation for DNA Delivery

The interplay of condensation and decondensation of DNA plays a crucial role in chromosome maintenance and gene expression. The molecular architectonics governing the chromatin condensation-decondensation cycle are worth studying, as DNA performs unique and distinct roles in each state and switches between two states without the loss of structural and functional integrity. This phenomenon has been adapted and implemented in transfection studies. Effective gene delivery into the cells to achieve respectable transfection efficiency has remained a challenge and emphasizes the need for understanding the steps involved in DNA delivery and transfection. Especially, recognizing the factors that effectively regulate DNA decondensation can provide logical solutions to the hurdles affecting the transfection efficiency. We designed a set of small molecule-based threading intercalation ligands as model condensing agents to study various factors influencing the DNA condensation and decondensation process. This study revealed condensation of DNA into nanocondensate by the threading intercalator and endogenous stimuli induced effective decondensation. Further, DNA nanocondensates are tracked using the intrinsic fluorescence in the lower pH of endocytic pathway and were evaluated as nonviral vectors for in cellulo delivery of plasmids. The correlation of decondensation of DNA nanocondensate with endogenous metal ions at their physiological concentrations provided valuable insights and implications for intracellular DNA delivery.

Hydrogen bonding of ionic liquids in the groove region of DNA controls the extent of its stabilization: synthesis, spectroscopic and simulation studies

Ionic liquids (ILs) have been extensively used for stabilization and long-term DNA storage. However, molecular level understanding of the role of the hydrogen bond of DNA with ILs in its stabilization is still inadequate. Two ILs, namely, 1,1,3,3-tetramethylguanidinium acetate (TMG) and 2,2-diethyl-1,1,3,3-tetramethylguanidinium acetate (DETMG), have been synthesized, of which TMG has a hydrogen bonding N-H group whereas DETMG does not contain any hydrogen bonding site. It has been found that both TMG and DETMG cations interact in the groove region of DNA; however, their mode of interaction is distinctly different, which causes the stabilization of DNA in the presence of TMG, whereas the effect is opposite in the case of DETMG. It is apparent from the data that only the accommodation of ILs in the groove region is not enough for the stabilization of DNA. MD simulation and spectroscopic studies combinedly indicate that the hydrogen bonding capability of the TMG cation enhances the hydrogen bonding between the Watson-Crick base pairs of DNA, resulting in its stabilization. In contrast, the bigger size as well as the absence of the hydrogen bonding site of the DETMG cation perturbs the minor groove width and base pair step parameters of DNA during its intrusion into the minor groove, which decreases the hydrogen bond between the Watson-Crick base pairs of DNA, leading to destabilization.

Fluorescence and Molecular Simulation Studies on the Interaction between Imidazolium-Based Ionic Liquids and Calf Thymus DNA

This work presents a molecular level investigation on the nature and mode of binding between imidazolium-based ionic liquids (ILs) ([Cnbim]Br where n = 2, 4, 6) with calf thymus DNA. This investigation offers valuable insight into the mechanisms of interactions that can affect the structural features of DNA and possibly cause the alteration or inhibition of DNA function. To expedite analysis, the study resorted to using molecular docking and COnductor like Screening MOdel for Real Solvents (COSMO-RS) in conjunction with fluorescence spectroscopic data for confirmation and validation of computational results. Both the fluorescence and docking studies consistently revealed a weak interaction between the two molecules, which corresponded to the binding energy of a stable docking conformation in the range of −5.19 to −7.75 kcal mol−1. As predicted, the rod-like structure of imidazolium-based ILs prefers to bind to the double-helix DNA through a minor groove. Interestingly, the occurrence of T-shape π-π stacking was observed between the amine group in adenine that faces the aromatic ring of imidazole. In addition, data of COSMO-RS for the interaction of individual nucleic acid bases to imidazolium-based ILs affirmed that ILs showed a propensity to bind to different bases, the highest being guanine followed by cytosine, thymine, uracil, and adenine.

Polynuclear zinc(II) complexes of thiosemicarbazone: Synthesis, X-ray structure and biological evaluation

Two new dimeric Zn(II) ([{ZnL¹(DMSO₂)}₂]·DMSO (1), [{ZnL²Cl}₂] (2)) and a novel tetrameric Zn(II) complex ([(Zn₂L³)₂(μ-OAc)₂(μ₃-O)₂] (3)), where H₂L¹ = 4-(p-methoxyphenyl) thiosemicarbazone of o-hydroxynapthaldehyde, HL² = 4-(p-methoxyphenyl)thiosemicarbazone of benzoyl pyridine and H₂L³ = 4-(p-chlorophenyl)thiosemicarbazone of o-vanillin are reported. Ligands and their complexes were characterized by spectroscopic and single crystal X-ray diffraction techniques. In addition, the complexes exhibited good binding affinity towards HSA (10¹² M^-1), which is supported by their ability to quench the tryptophan fluorescence emission spectra of HSA. The complexes were also screened for their DNA binding propensity through UV-vis absorption titration, circular dichroism and fluorescence spectral studies. Results show that they effectively interact with CT-DNA through an intercalative mode of binding, with binding constants ranging from 10³ to 10⁴ M^-1. Among the three complexes 1 has the highest binding affinity towards CT-DNA. Further, the phosphatase activity was evaluated using bis(2,4-dinitrophenyl)phosphate (BDNPP) as substrate, however, the complexes did not yield any measurable catalytic activity. Nevertheless the complexes showed significant cytotoxic potential against HeLa and HT-29 cancer cell lines that was assessed through MTT assay and DAPI staining. Remarkably, complex 1 showed better activity than cisplatin against HT-29 cell line.

Evaluation of plasmid DNA stability against ultrasonic shear stress and its in vitro delivery efficiency using ionic liquid [Bmim][PF6]

The hydrophobic ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate [Bmim][PF₆] forms nanostructures with negatively charged plasmid DNA through electrostatic interactions. The formation of plasmid DNA/IL nanostructures was confirmed by measuring the zeta potential of plasmid DNA as well as plasmid DNA/IL nanostructures. The zeta potential of the nanostructures was positive, although plasmid DNA is negatively charged. The positive zeta potential is due to the complexation between plasmid DNA and positively charged ionic liquid [Bmim][PF₆]. The ability of ionic liquid [Bmim][PF₆] to protect plasmid DNA against ultrasonic shear stress was also investigated using an agarose gel electrophoretic assay and showed that ionic liquid stabilizes plasmid DNA against ultrasonication. The plasmid DNA and plasmid DNA/IL nanostructures were subjected to ultrasonic shear stress for different time periods and the biological functionality of pristine plasmid DNA (i.e., expression of the eGFP gene) as well as the self-assembled nanostructures was investigated in vitro using three different cell lines, COS7, HEK293 and HeLa. Ionic liquid [Bmim][PF₆] protected the plasmid DNA against ultrasonic shear stress and also enhanced gene transfection efficiency in vitro. Furthermore, the cytotoxicity of ionic liquid [Bmim][PF₆] was assayed in vitro using all three cell lines and the toxicity was very low. Therefore, the ionic liquid [Bmim][PF₆] stabilizes plasmid DNA against ultrasonic shear stress and also enhances its in vitro delivery efficiency.

The hydrophobic ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate [Bmim][PF₆] forms ultrasonically stable and functional nanostructures with negatively charged plasmid DNA through electrostatic interactions.

Critical Assessment of the Interaction between DNA and Choline Amino Acid Ionic Liquids: Evidences of Multimodal Binding and Stability Enhancement

Long-term storage and stability of DNA is of paramount importance in biomedical applications. Ever since the emergence of ionic liquids (ILs) as alternate green solvents to aqueous and organic solvents, their exploration for the extraction and application of DNA need conscientious understanding of the binding characteristics and molecular interactions between IL and DNA. Choline amino acid ILs (CAAILs) in this regard seem to be promising due to their non-cytotoxic, completely biobased and environment-friendly nature. To unravel the key factors for the strength and binding mechanism of CAAILs with DNA, various spectroscopic techniques, molecular docking, and molecular dynamics simulations were employed in this work. UV-Vis spectra indicate multimodal binding of CAAILs with DNA, whereas dye displacement studies through fluorescence emission confirm the intrusion of IL molecules into the minor groove of DNA. Circular dichorism spectra show that DNA retains its native B-conformation in CAAILs. Both isothermal titration calorimetry and molecular docking studies provide an estimate of the binding affinity of DNA with CAAILs ≈ 4 kcal/mol. The heterogeneity in binding modes of CAAIL-DNA system with evolution of time was established by molecular dynamics simulations. Choline cation while approaching DNA first binds at surface through electrostatic interactions, whereas a stronger binding at minor groove occurs via van der Waals and hydrophobic interactions irrespective of anions considered in this study. We hope this result can encourage and guide the researchers in designing new bio-ILs for biomolecular studies in future.

Cholinium-based Good's buffers ionic liquids as remarkable stabilizers and recyclable preservation media for recombinant small RNAs

RNA is a biopolymer of high relevance in the biopharmaceuticals field and in fundamental and applied research; however, the preservation of the RNA stability is still a remarkable challenge. Herein, we demonstrate the enhanced potential of aqueous solutions of self-buffering cholinium-based Good's buffers ionic liquids (GB-ILs), at 20 and 50 % (w/w), as alternative preservation media of recombinant small RNAs. The thermal stability of RNA is highly enhanced by GB-ILs, with an increase of 14 °C in the biopolymer melting temperature - the highest increase observed up to date with ILs. Most GB-ILs investigated improve the stability of RNA at least up to 30-days, both at 25 °C and at 4 °C, without requiring the typical samples freezing. Molecular dynamics simulations were applied to better understand the molecular-level mechanisms responsible for the observed RNA improved stability. The number of IL cations surrounding the RNA chain is similar, yet with differences found for the IL anions, which are responsible for the overall charge of the biopolymer first solvation sphere. No cytotoxicity of the studied solutions containing RNA and ILs at 20 % (w/w) was observed onto two distinct human cell lines, reinforcing their potential to act as preservation media when foreseeing biopharmaceutical applications. Finally, RNA was successfully recovered from the ILs aqueous solutions, without changes in its structural integrity, and the ILs successfully recycled and reused.

Ionic liquids in whole-cell biocatalysis: a compromise between toxicity and efficiency

Comparison of chemical catalysis by metal complexes, enzymatic catalysis and whole-cell biocatalysis shows well-addressed advantages of the latter approach. However, a critical limitation in the practical applications originates from the high sensitivity of microorganisms to the toxic effects of organic solvents. In the present review, we consider toxic solvent properties of ionic liquid/water systems towards the development of efficient applications in practical organic transformations.

Ionic liquid induced G-quadruplex formation and stabilization: spectroscopic and simulation studies

Among different polymorphs of DNA, G-quadruplex (GQ) formation in guanine rich sequences has received special attention due to its direct relevance to cellular aging and abnormal cell growths. To date, smaller ions like Na⁺, K⁺, Li⁺, and NH₄⁺ are the best possible selective GQ stabilizing materials. Herein, we report that an ionic liquid (IL), i.e. guanidinium tris(pentafluoroethyl)trifluorophosphate, can not only instigate the GQ formation in the absence of conventional GQ forming ions (like Na⁺, K⁺, NH₄⁺, etc.), but also stabilizes the GQ structure. This conformational transition has been confirmed through different spectroscopic tools and molecular dynamics (MD) simulation studies. MD simulation shows that one of the guanidinium cations resides in the G-tetrad core, while bulky anions prefer to stay near the GQ surface resulting in GQ formation and stabilization. This study thus brings out a special type of ionic liquid that acts as a GQ stabilizer. The origin of GQ stabilization by IL presented here may also help in the future design of IL for GQ formation and stabilization.

Single-probe multistate detection of DNA via aggregation-induced emission on a graphene oxide platform

Graphene and graphene oxides (GO), or their reduced forms, have been introduced in a variety of biosensing platforms and have exhibited enhanced performance levels in these forms. We herein report a DNA sensing platform consisting of aggregation-induced emission (AIE) molecules and complementary DNA (comDNA) adsorbed on GO. We experimentally turned the AIE molecule on and off by adjusting its distance, which correlates with DNA structures as shown in our computational results, from the GO sheet, which quenches depending on its distance from the graphene plane. The changes in florescence are reproducible, which demonstrates the probe's ability to identify the binding state of the DNA. Our molecular dynamics simulation results reveal strong π-π interactions between single-strand DNA (ssDNA) and GO, which enable the ssDNA molecule to move closer to the graphene oxide. This reduces the center of mass and binding free energies in the simulation. When hybridized with comDNA, the increased distance, evidenced by the reduced interaction, eliminates the quenching effect and turns on the AIE molecule. Our protocol use of the AIE molecule as a probe thus avoids the complicated steps involved in covalent functionalization and allows the rapid and label-free detection of DNA molecules.

STATEMENT OF SIGNIFICANCE

A simple, rapid method of fluorescent measurement of DNA hybridization in the presence of graphene (oxide) is presented. Conventional fluorescent dyes offer high performance in biosensors. However, labeling procedures are synthetically demanding in time and resources making it less cost-effective. Molecules with aggregation-induced-emission (AIE) property have advantages over traditional fluorescent molecules because of their intrinsic preference for detection as a turn-on probe and their single-molecule detection ability. Previous work has shown AIE dyes act as excellent "label-free" bioprobes with high sensitivity but with limited selectivity. Graphene oxide (GO) with its unique optical properties and affinity to different kinds of biomolecules can be used as an auxiliary to enhance selectivity of AIE dyes. In this work, we report a label-free strategy to detect DNA of particular sequence by water-soluble AIE probes with the aid of GO, supported by the computational explanations for this phenomenon.

Biological Activity of Ionic Liquids and Their Application in Pharmaceutics and Medicine

Ionic liquids are remarkable chemical compounds, which find applications in many areas of modern science. Because of their highly tunable nature and exceptional properties, ionic liquids have become essential players in the fields of synthesis and catalysis, extraction, electrochemistry, analytics, biotechnology, etc. Apart from physical and chemical features of ionic liquids, their high biological activity has been attracting significant attention from biochemists, ecologists, and medical scientists. This Review is dedicated to biological activities of ionic liquids, with a special emphasis on their potential employment in pharmaceutics and medicine. The accumulated data on the biological activity of ionic liquids, including their antimicrobial and cytotoxic properties, are discussed in view of possible applications in drug synthesis and drug delivery systems. Dedicated attention is given to a novel active pharmaceutical ingredient-ionic liquid (API-IL) concept, which suggests using traditional drugs in the form of ionic liquid species. The main aim of this Review is to attract a broad audience of chemical, biological, and medical scientists to study advantages of ionic liquid pharmaceutics. Overall, the discussed data highlight the importance of the research direction defined as "Ioliomics", studies of ions in liquids in modern chemistry, biology, and medicine.

Active biopolymers in green non-conventional media: a sustainable tool for developing clean chemical processes

By understanding structure–function relationships of active biopolymers (e.g. enzymes and nucleic acids) in green non-conventional media, sustainable chemical processes may be developed.

Oxidovanadium(v) complexes of aroylhydrazones incorporating heterocycles: synthesis, characterization and study of DNA binding, photo-induced DNA cleavage and cytotoxic activities

The interaction of four neutral oxidovanadium(v) complexes with DNA and their cytotoxic activities have been reported.