Spectroscopic study on interaction between three cationic surfactants with different alkyl chain lengths and DNA

Complexation of Oligo- and Polynucleotides with Methoxyphenyl-Functionalized Imidazolium Surfactants

Interaction between cationic surfactants and nucleic acids attracts much attention due to the possibility of using such systems for gene delivery. Herein, the lipoplexes based on cationic surfactants with imidazolium head group bearing methoxyphenyl fragment (MPI-n, n = 10, 12, 14, 16) and nucleic acids (oligonucleotide and plasmid DNA) were explored. The complex formation was confirmed by dynamic/electrophoretic light scattering, transmission electron microscopy, fluorescence spectroscopy, circular dichroism, and gel electrophoresis. The nanosized lipoplex formation (of about 100-200 nm), contributed by electrostatic, hydrophobic interactions, and intercalation mechanism, has been shown. Significant effects of the hydrocarbon tail length of surfactant and the type of nucleic acid on their interaction was revealed. The cytotoxic effect and transfection ability of lipoplexes studied were determined using M-HeLa, A549 cancer cell lines, and normal Chang liver cells. A selective reduced cytotoxic effect of the complexes on M-HeLa cancer cells was established, as well as a high ability of the systems to be transfected into cancer cells. MPI-n/DNA complexes showed a pronounced transfection activity equal to the commercial preparation Lipofectamine 3000. Thus, it has been shown that MPI-n surfactants are effective agents for nucleic acid condensation and can be considered as potential non-viral vectors for gene delivery.

Simple and Rapid Detection of Ibuprofen─A Typical Pharmaceuticals and Personal Care Products─by a Liquid Crystal Aptasensor

This work established a liquid crystal (LC) aptasensor for simple and rapid detection of ibuprofen, a typical pharmaceuticals and personal care products (PPCPs) pollutant. A negatively charged DNA aptamer specific for ibuprofen and a positively charged amphiphilic surfactant, hexadecyltrimethylammonium bromide (CTAB), were incubated with the sample and then directly added onto the LC interface. In the presence of ibuprofen, the specific binding of ibuprofen with the DNA aptamer will release CTAB, which then adsorbed at the LC-aqueous interface and induced the orientational change of LCs to homeotropic orientation with a dark optical signal output. While in the absence of ibuprofen, the DNA aptamer binds with CTAB through hydrophobic and electrostatic interactions, LCs remained in the planar orientation with a bright optical signal output. This LC aptasensor also has good specificity for ibuprofen and can even detect ibuprofen drug in tap water. Moreover, the response time of the LC aptasensor is fast in minutes. Additionally, this LC aptasensor benefits in monitoring the water quality and inspires the exploration of a general platform for PPCPs detection.

Recent advances in materials for hemostatic management

Traumatic hemorrhage can be a fatal event, particularly when large quantities of blood are lost in a short period of time. Therefore, hemostasis has become a crucial part of emergency treatment. For small wounds, hemostasis can be achieved intrinsically depending on the body's own blood coagulation mechanism; however, for large-area wounds, particularly battlefield and complex wounds, materials delivering rapid and effective hemostasis are required. In parallel with the constant progress in science, technology, and society, advances in hemostatic materials have also undergone various iterations by integrating new ideas with old concepts. There are various natural and synthetic hemostatic materials, including hemostatic powders, adhesives, hydrogels, and tourniquets, for the treatment of severe external trauma. This review covers the differences among the currently available hemostatic materials and comprehensively describes the hemostatic effects of different materials based on the underlying mechanisms. Finally, solutions for current issues related to trauma bleeding are discussed, and the prospects of hemostatic materials are proposed.

Effect of Alkyl Chain Length on the Photophysical, Photochemical, and Photobiological Properties of Ruthenium(II) Polypyridyl Complexes for Their Application as DNA-Targeting, Cellular-Imaging, and Light-Activated Therapeutic Agents

A family of six Ru(II) polypyridyl complexes (1-6) which contain phenanthroline-based ligands functionalized with alkyl chains of different lengths (one methyl group, 10 and 21 carbon alkyl chains) and either 1,10-phenanthroline (phen) or 1,4,5,8-tetraazaphenanthrene (TAP) as ancillary ligands have been synthesized and characterized. The influence of the alkyl chain length on their photophysical and photochemical properties as well as in their photobiological applications has been elucidated by monitoring the changes in their MLCT-centered absorption and emission bands. The presence of one methyl group or 10 carbon alkyl chains does not seem to significantly affect the photophysical and photochemical properties of the resulting Ru(II) complexes when compared to the well-known [Ru(phen)₃]²⁺ and [Ru(TAP)₂phen]²⁺. However, an effect on their emission properties and in their ability to photosensitize singlet oxygen is observed for the Ru(II) complexes containing 21 carbon alkyl chains. The binding of these complexes to salmon testes DNA (stDNA) was investigated by observing the changes in the photophysical properties. Complexes 1, 2, 4, and 5 all showed changes in their MLCT bands that could be analyzed using conventional fitting methods, such as the Bard equation. In contrast, complexes 3 and 6, possessing long aliphatic chains, gave rise to nonclassic behavior. In addition to these analyses, both thermal denaturation and circular dichroism studies of 1-6 were carried out in the presence of stDNA which confirmed that these complexes bind to DNA. Confocal microscopy and viability studies in HeLa cervical cancer cells reveal an alkyl chain-length dependence on the cellular uptake and cytotoxicity of the resulting Ru(II) complexes due to an enhancement of their lipophilicity with increasing alkyl chain length. Thus, complexes containing 10 and 21 carbon alkyl chains are rapidly taken up into HeLa cells and, in particular, those with 21 carbon alkyl chains show a significant phototoxicity against the same cell line. Therefore, this study provides further insight into the possible modulation of the photophysical, photochemical, and photobiological properties of Ru(II) polypyridyl complexes by varying the length of the alkyl chains attached to the polypyridyl ligands coordinated to the Ru(II) center and the nature of the auxiliary groups, which we show has a significant effect on photophysical and biological properties.

Cationic Single-Chained Surfactants with a Functional Group at the End of the Hydrophobic Tail DNA Compacting Efficiency

The interaction between calf-thymus DNA, ctDNA, and various single-chained surfactants with different functional groups at the end of hydrophobic tail was studied with the goal of investigating the influence of the functional group nature on surfactant DNA compacting efficiency. The surfactants investigated were dodecyltriethylammonium bromide (DTEABr), triethyl(1-phenoxydodecyl)ammonium bromide (12PhBr), triethyl(2-naphthoxydodecyl)ammonium bromide (12NBr) and 11-(isonicotinoyloxy)-N,N,N-triethyl-1-undecanaminium bromide (11PyBr). Results made evident that the surfactants' tendencies to self-aggregation is the key factor determining their efficiency to compact the nucleic acid. Subsequently, DOPE/12NBr/pEGFP-C1 lipoplexes, with different cationic surfactant molar fractions (α) and mass ratios (L/D), were prepared and characterized. DOPE is a zwitterionic phospholipid 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine, and the plasmid pEGFP-C1 carries a GFP coding sequence with the necessary regulatory elements for constitutive expression of the gene in human cells. 12NBr was chosen because it was the most efficient DNA compacting agent among the surfactants investigated. Finally, the cytotoxicity and transfection efficiency (TE) of DOPE/12NBr/pDNA lipoplexes, with different compositions, were investigated.

Influence of the degree of oligomerization of surfactants on the DNA/surfactant interaction

The interaction between calf thymus DNA, ctDNA, and a series of oligomeric surfactants derived from N-benzyl-N,N-dimethyl-N-(1-dodecyl)ammonium chloride is investigated. The influence of the surfactants' degree of oligomerization (2, 3 and 4) on the ctDNA/surfactant interaction is studied, as well as the effect of the structure of the spacer group linking the individual surfactant fragments. In particular, the effect of the distance between the positive charges and the hydrophobic chains within the oligomers on these interactions was examined, by using the three positional isomers (i.e., ortho-, meta-, and para-) with the rigid xylidene moiety as spacer. Results show that the dimeric ("gemini") surfactants are much more efficient in the inversion of the nucleic acid charge than the single-chained (monomeric) surfactant. Whereas the ortho - isomer causes a partial condensation, the meta - and para - isomers can completely condense ctDNA. The meta - and para - isomers of the trimeric surfactants can also completely condense the polynucleotide. In contrast, the tetrameric surfactant investigated does not change the morphology of the nucleic acid from an elongated coil into a compacted form, in spite of effectively inverting the nucleic acid's charge in their complex. Accordingly, the capacity for ctDNA compaction of oligomeric surfactants is not simply correlated to their degree of oligomerization, but depends on a complex balance of the number and relative distance of cationic charges and/or hydrophobic tails in the surfactants for effectively interacting with the nucleic acid to form the appropriate complex. This information will help to design more effective cationic surfactants as non-viral vectors for gene therapy.

Possible sensor applications of selected DNA-surfactant complexes

Although much research has been performed on DNA complexes carrying long alkyl chains (C10, C16, and C18), there is no information about physicochemical characterization of synthesized composites with allyl imidazole-based ionic liquids and quaternary ammonium salts with n-butyl chains. Here, complexes were synthesized by ion-exchange reactions between sonicated DNA and three ionic liquids (ILs) formed from two imidazole-based compounds, 1-allyl-3-methylimidazolium bromide (Amim) or 1-butyl-3-methylimidazolium bromide (Bmim), and from the quaternary ammonium salt tetra-n-butylammonium bromide (TBAB). Signals in UV-Vis, IR, and CD spectra indicating inclusion of small molecules into the DNA structure confirmed the formation of DNA complexes. Both IR and CD spectra indicated that the B-form conformation of the DNA did not change after the formation of the complexes. Similarly, X-ray diffraction patterns revealed that the formation of IL-DNA complexes did not change the structure of native B-form DNA. Molecular weight (M_w) and radii of gyration (R_g) values of IL-DNA complex chains, established by high-performance size exclusion chromatography coupled with multiangle-laser light-scattering with a differential refractive index detector, were significantly lower than those values found for native DNA molecules due to DNA fragmentation by sonication during complex formation and the direct effects of the IL on the DNA. Scanning electron microscopy images indicate the formation of nanofibres in DNA-Amim and DNA-Bmim complexes, whereas the formation of nanowires was found in samples of DNA-TBAB complexes. Changes in optical properties confirmed by UV and photoluminescence make DNA-IL complexes potential candidates for biosensor application.

Investigation on interaction of DNA and several cationic surfactants with different head groups by spectroscopy, gel electrophoresis and viscosity technologies

In this study, the interaction between DNA and several cationic surfactants with different head groups such as ethyl hexadecyl dimethyl ammonium bromide (EHDAB), hexadecyl dimethyl benzyl ammonium chloride (HDBAC), and cetyl pyridinium bromide (CPB) were investigated by UV-vis absorption, fluorescence and circular dichroism (CD) spectroscopy, gel electrophoresis, and viscosity technologies. The results show that these cationic surfactants can interact with DNA and major binding modes are electrostatic and hydrophobic. Also, CPB and HDBAC molecules interact with DNA by partial intercalation, and CPB has slightly stronger intercalation than HDBAC, while EHDAB interacts with DNA by non-intercalation. The different head groups of the surfactant molecules can influence the interaction strength. CPB has the stronger interaction with DNA than the others. Moreover, surfactant concentration, the ratio of DNA and fluorescence probe, ionic strength can influence the interaction. The surfactants may interact with DNA by the competition reactions with BR for DNA-BR. The increase of ionic strength may favor the surface binding between DNA and surfactants to some extent. This work provides deep mechanistic insight on the toxicity of cationic surfactants with different head groups to DNA molecules.