Effect Of Spacer Chain Length Research Articles

Binding Interaction of Gemini Surfactants with Nanotubes of β‐Cyclodextrin and Controlled Release of Guest Molecules: Effect of Spacer Chain Length and Concentration of Surfactants

AbstractThe formation of guest molecule (Coumarin 485, C‐485) induced nanotubes by β‐cyclodextrin (β‐CD) and their interactions with cationic gemini surfactants (12‐n‐12, where n=3, 6, and 12) have been explored by means of UV‐visible absorption, steady‐state fluorescence and fluorescence anisotropy, time‐resolved fluorescence and fluorescence anisotropy, and dynamic light scattering (DLS) measurements. β‐CD at its high concentration form extended nanotubes and secondary aggregates of nanotubes. A gemini surfactant has a significant role in binding interactions between C‐485 and nanotubes of β‐CD. In a low concentration range, surfactant molecules are co‐associated with the guest molecules, C‐485, however, at high concentrations, they are capable of pushing C‐485 out of the nanotubular cavities. A gemini molecule with a comparatively longer spacer chain is more efficient in removing the guest molecules out of the nanotubular cavities. Also, the rate of release of guest molecules increases with increasing concentration of surfactants. Release of guest molecules from the nanotubes can be tuned by changing the spacer chain length and concentration of gemini surfactants. Guest molecules after coming out of the nanotubular cavities, get solubilized in the micelles formed by surfactant molecules in the solution. The results of the present work suggest potential application in the development of promising drug delivery systems.

Fine tuning neuronal targeting of nanoparticles by adjusting the ligand grafting density and combining PEG spacers of different length

Poly(ethylene glycol) (PEG) has been extensively used to coat the surface of nanocarriers to improve their physicochemical properties and allow the grafting of targeting moieties. Still, to date there is no common agreement on the ideal PEG coverage-density or length to be used for optimum vector performance. In this study, we aimed to investigate the impact of both PEG density and length on the vectoring capacity of neuron-targeted gene-carrying trimethyl chitosan nanoparticles. The non-toxic fragment from the tetanus toxin (HC) was coupled to a 5 kDa heterobifunctional PEG (HC-PEG5k) reactive for the thiol groups inserted into the polymer backbone and grafted at different densities onto the nanoparticles. Internalization and transfection studies on neuronal versus non-neuronal cell lines allowed to determine the PEG density of 2 mol% of PEG chains per mol of primary amine groups as the one with superior biological performance. To enhance HC exposure and maximize cell-nanoparticle specific interaction, NPs containing different ratios of HC-PEG5k and 2 kDa methoxy-PEG at the same grafting density were produced. By intercalating HC-PEG5k with methoxy-PEG2k we attained the best performance in terms of internalization (higher payload delivery into cells) and transfection efficiency, using twice lower amount of HC. This outcome highlights the need for fine-tuning of PEG-modified nanoparticles towards the achievement of optimal targeting. Statement of SignificanceThe amount and exposure of targeting moieties at a nanoparticle surface are critical parameters regarding the targeting potential of nanosized delivery vectors. However, to date, few studies have considered fundamental aspects impacting the ligand-receptor pair interaction, such as the effect of spacer chain length, flexibility or conformation. By optimizing the PEG spacer density and chain length grafted into nanoparticles, we were able to establish the formulation that maximizes cell-nanoparticle specific interaction and has superior biological performance. Our work shows that the precise adjustment of the PEG coverage-density presents a significant impact on the selectivity and bioactivity of the developed formulation, emphasizing the need for the fine-tuning of PEG-modified nanoparticles for the successful development of the next-generation nanomedicines.

Effect of spacer chain length on the liquid structure of aqueous dicationic ionic liquid solutions: molecular dynamics studies.

The liquid structure of aqueous solutions of five different imidazolium based gemini dicationic ionic liquids 1,n-bis(3-methylimidazolium-1-yl) alkane bromide (n being the length of the spacer alkyl chain), with propyl, pentyl, octyl, decyl and hexadecyl spacer chains has been studied using atomistic molecular dynamics simulations. While solutions with propyl and pentyl spacers are homogeneous, those with octyl and decyl spacers show spatial heterogeneity. Microscopic inhomogeneity in the bulk solution phase increases with an increase in the length of the spacer chain leading to polydisperse aggregates in the solution with a hexadecyl spacer. Organization of the cations at the solution-vapor interface also depends upon the length of the spacer chain with the most organized interfacial layer observed in the solution with a hexadecyl spacer chain.

Effects of Spacer Chain Length of Amino Acid-Based Gemini Surfactants on Wormlike Micelle Formation

We studied the effects of the spacer chain length of amino acid-based gemini surfactants on the formation of wormlike micelles in aqueous solutions. The surfactants used were synthesized by reacting dodecanoylglutamic acid anhydride with diamine compounds (ethylenediamine, pentanediamine, and octanediamine), and were abbreviated as 12-GsG-12 (s: the spacer chain length of 2, 5, and 8 methylene units). These surfactants yielded viscoelastic wormlike micellar solutions at pH 9 upon mixing with a cationic monomeric surfactant, hexadecyltrimethylammonium bromide (HTAB). We found that the rheological behavior was strongly dependent on the spacer chain length and HTAB concentration. When the shortest spacer chain analogue (12-G2G-12) was used, an increased HTAB concentration resulted in the following structural transformations of the micelles: (i) spherical or rodlike micelles; (ii) anionic wormlike micelles exhibiting a transient network structure; (iii) anionic wormlike micelles with a micellar branching or interconnected structure; and (iv) cationic wormlike micelles. Similarly, when the middle spacer chain analogue (12-G5G-12) was used, a structural transformation from anionic to cationic wormlike micelles occurs; however, molecular aggregates with a lower positive curvature were also formed in this transition region. When the longest spacer analogue (12-G8G-12) was used, the formation of cation-rich molecular aggregates was not observed. These transition behaviors were attributed to the packing geometry of the gemini surfactants with HTAB. Additionally, as the spacer chain length increased, the zero-shear viscosity in the anionic wormlike micellar region decreased, suggesting limited one-dimensional micellar growth of spherical, rodlike, or anionic wormlike micelles.

Discotic liquid crystals of transition metal complexes 49: establishment of helical structure of fullerene moieties in columnar mesophase of phthalocyanine-fullerene dyads

A homologous series of the phthalocyanine-fullerene dyads, Cn-PcM(OFbaC60) (n = 6, 8, 10, 12; M = Cu , Ni , Co : 3a–3f) have been synthesized to obtain homeotropic alignment at rt and investigate the effects of spacer chain length (n = 6, 8, 10, 12) and central metal ( M = Cu , Ni , Co ) on the mesomorphism. Interestingly, the shorter-spacer-substituted (n = 6, 8; M = Cu ) dyads 3a and 3b showed a hexagonal columnar mesophase (Colh), whereas the longer-spacer-substituted (n = 10, 12; M = Cu , Ni , Co ) dyads 3c–3f showed a tetragonal columnar mesophase (Coltet). Moreover, each of the homologs 3a–3e shows perfect homeotropic alignment in both the Colh and Coltet mesophases at rt. More interestingly, these columnar mesophases gave a very unique XRD reflection peak denoted as Peak H in a very small angle region of 0.8 < 2θ < 2.0 degree. We have established at the first time from our developed two new XRD sample preparation techniques that the Peak H is due to the helical structure of fullerenes around columns formed by one-dimensionally stacked Pc cores. 1D nano array structure of donor and acceptor between two electrodes is recently proposed to obtain higher photoelectric conversion efficiency for organic thin film solar cells. This 1D nano array structure is almost compatible with the present homeotropically aligned Pc- C 60 dyads 3a–3f between two glass plates. Hence, these novel Pc- C 60 dyads 3a–3f may be very suitable to organic thin film solar cells.

Synthesis and properties of novel alkyl sulfate gemini surfactants

Four anionic gemini surfactants of the sulfate type C12CnC12, where n is the spacer chain length (n = 3, 4, 6, and 10) were synthesized. The structures of these surfactants were confirmed by FT-IR, 1H NMR, ESI mass spectra (ESI-MS), and elemental analysis. The surface-active properties of these compounds were investigated by means of surface tension, electrical conductivity, and fluorescence measurements. Premicellar aggregations were found for the four gemini surfactants, as revealed by the conductivity measurement. The formation of premicellar aggregates may account for the discrepancy between the critical micelle concentration (cmc) obtained by the surface tension and conductivity measurement. The cmc values of these gemini surfactants were much lower than that of sodium dodecylsulfate (SDS) and decreased monotonously with the increase of spacer chain length from 3 to 10. The effect of spacer chain length on the performance properties like foaming, emulsion stability, and lime soap dispersing ability were also studied and discussed. Practical applications: Alkyl sulfate surfactants are one of the most widely used surfactants. The new alkyl sulfate gemini surfactants synthesized in our study are more surface-active than sodium dodecylsulfate. These gemini surfactants possess low critical micelle concentrations, high emulsion stability, and excellent lime soap dispersing ability. They have potential applications in the fields of cosmetics, detergents, etc.

Interaction Between Nonionic and Gemini (Cationic) Surfactants: Effect of Spacer Chain Length

AbstractThe interaction between mixtures of nonionic surfactant polyethylene glycol p‐(1,1,3,3‐tetramethyl butyl)‐phenyl ether and cationic gemini surfactants alkanediyl‐α,ω‐bis(dimethyldodecylammonium bromide) (12‐s‐12, where s = 2, 4 and 6) was studied using surface tension and small‐angle neutron scattering measurements. Marked interaction was observed for the investigated surfactants mixtures which depend upon the hydrophobic spacer length of the gemini surfactant and also on the fraction of nonionic surfactant in the mixed systems. The results are discussed in terms of interaction parameters calculated according to the theory of regular solutions which uses the critical micelle concentration determined tensiometrically to calculate the molecular interaction parameter and the mole fractions of the two components in the mixed micelles. A relatively high negative molecular interaction parameter value (up to −3.40) obtained for mixtures of nonionic and cationic gemini surfactant indicates a presence of strong attractive interaction in the mixed system that increases with the spacer length of the gemini surfactant. Micellar parameters deduced from small‐angle neutron scattering measurements also compliment the surface tension results.

Effects of Spacer Chain Length and Additives on Solution Properties of Cationic Gemini Surfactant

The critical micelle concentration (CMC) has been determined for the gemini surfactant trimethylene-1,3-bis(dodecyldimethyl ammonium bromide)12-s-12,2Br−1 by means of electricity conductivity measurements. For the same number of carbon atoms in the hydrophobic chain per hydrophilic head group, geminis have CMC values well below those of conventional single-chain cationic surfactants. The CMC of 12-3-12 reduces with the addition of n-alcohol except ethanol and with the increase of n-alcohol chain length as well as increase of concentration of n-butanol and sodium chloride. Steady-state fluorescence quenching technology has been employed to study the aggregation number of micelle, which increases with increase in the length of n-alcohol. The Kraft temperature measurements also indicate that the stability of solid surfactant hydrate decreases along with the improvement of concentration of n-butanol and sodium chloride.

Magnetic Field Effects on Photoelectrochemical Responses of Modified Electrodes with Langmuir-Blodgett Monolayer Containing Porphyrin-Viologen Linked Compounds

Modified electrodes were prepared by depositing a monolaycr containing porphyrin-viologcn linked compounds with various spacer chain-length on ITO electrodes by Langmuir-Blodgctt method. Stable anodic photocurrcnts were observed by visible light irradiation upon the modified electrodes. The photocurrents were clearly enhanced in the presence of magnetic fields. Effects of spacer chain-length on the magnetic field effects arc caused by photoactive triplet radical pairs.

Spectroscopic studies on exchange properties in through-ring cyclodextrin complexes of carbazole-viologen linked compounds: effects of spacer chain length

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSpectroscopic studies on exchange properties in through-ring cyclodextrin complexes of carbazole-viologen linked compounds: effects of spacer chain lengthHiroaki Yonemura, Motohiro Kasahara, Hide Saito, Hiroshi Nakamura, and Taku MatsuoCite this: J. Phys. Chem. 1992, 96, 14, 5765–5770Publication Date (Print):July 1, 1992Publication History Published online1 May 2002Published inissue 1 July 1992https://doi.org/10.1021/j100193a021RIGHTS & PERMISSIONSArticle Views281Altmetric-Citations64LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (698 KB) Supporting Info (1)»Supporting Information Supporting Information Get e-Alerts