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Gene therapy has the potential to facilitate targeted expression of therapeutic proteins to promote cartilage regeneration in osteoarthritis (OA). The dense, avascular, aggrecan‐glycosaminoglycan (GAG) rich negatively charged cartilage, however, hinders their transport to reach chondrocytes in effective doses. While viral vector mediated gene delivery has shown promise, concerns over immunogenicity and tumorigenic side‐effects persist. To address these issues, this study develops surface‐modified cartilage‐targeting exosomes as non‐viral carriers for gene therapy. Charge‐reversed cationic exosomes are engineered for mRNA delivery by anchoring cartilage targeting optimally charged arginine‐rich cationic motifs into the anionic exosome bilayer by using buffer pH as a charge‐reversal switch. Cationic exosomes penetrated through the full‐thickness of early‐stage arthritic human cartilage owing to weak‐reversible ionic binding with GAGs and efficiently delivered the encapsulated eGFP mRNA to chondrocytes residing in tissue deep layers, while unmodified anionic exosomes do not. When intra‐articularly injected into destabilized medial meniscus mice knees with early‐stage OA, mRNA loaded charge‐reversed exosomes overcame joint clearance and rapidly penetrated into cartilage, creating an intra‐tissue depot and efficiently expressing eGFP; native exosomes remained unsuccessful. Cationic exosomes thus hold strong translational potential as a platform technology for cartilage‐targeted non‐viral delivery of any relevant mRNA targets for OA treatment. [ABSTRACT FROM AUTHOR]

In this study, we use modified cationic nanocarriers as vehicles for the intracellular delivery of therapeutic siRNA. After developing nanocarrier formulations with appropriate pKa, size, swellability, and cytocompatibility, we investigated the importance of siRNA loading methods by studying the impact of the pH and time over which siRNA is loaded into the nanocarriers. We concentrate on diffusion‐based loading in the presence and absence of electrostatic interactions. siRNA release kinetics were studied using samples prepared from nanocarriers loaded by both mechanisms. In addition, siRNA delivery was evaluated for two formulations. While previous studies were conducted with samples prepared by siRNA loading at low pH values, this research provides evidence that loading conditions of siRNA affect the release behavior. This study concludes that this concept could prove advantageous for eliciting prolonged intracellular release of nucleic acids and negatively charged molecules, effectively decreasing dose frequency and contributing to more effective therapies and improved patient outcomes. In addition, our findings could be leveraged for enhanced control over siRNA release kinetics, providing novel methods for the continued optimization of cationic nanoparticles in a wide array of RNA interference‐based applications. [ABSTRACT FROM AUTHOR]

The effect of Ru substitution on the structure and electrochemical properties of P2‐type Na0.67CoO2 is investigated. The first‐discharge capacities of Na0.67CoO2 and Na0.6 [Co0.78Ru0.22]O2 materials are 128 and 163 mAh g−1 (23.5 mA g−1), respectively. Furthermore, the rate capability is improved due to the electro‐conducting nature of Ru doping. Operando X‐ray diffraction analysis reveals that the Na0.67CoO2 does not undergo a phase transition; however, multiple Na+/vacancy ordered superstructures within the P2 phase appear during Na+ extraction/insertion. In contrast, the Na0.6[Co0.78Ru0.22]O2 material undergoes a P2–OP4 phase transition during desodiation, with no formation of Na+/vacancy ordering within the P2 phase. The increased discharge capacity of Na0.6[Co0.78Ru0.22]O2 is most likely associated with additional cationic Ru4+/Ru5+ redox and increased anionic O2−/(O2n−) redox participation. Combined experimental (galvanostatic cycling, X‐ray absorption spectroscopy, differential electrochemical mass spectrometry) and theoretical (density functional theory calculations) studies confirm that Ru substitution provokes the oxygen‐redox reaction and that partial O2 release from the oxide lattice is the origin of the reaction. The findings provide new insight for improving the electrode performance of cathode materials via 4d Ru substitution and motivate the development of a new strategy for the design of high‐capacity cathode materials for sodium‐ion batteries. [ABSTRACT FROM AUTHOR]

Scandium(III) and ytterbium(III) trifluoromethanesulfonate are active for the terminationless polymerization of moderate reactivity olefins (β‐pinene, isobutene, styrene) in conjunction with a variety of initiators (e.g., Brønsted acids, halogens, and carbocation synthons). Neither Lewis acid requires chlorinated/toxic solvents to operate. The Yb congener is quantitatively recovered by aqueous extraction, reactivated by dehydration, and maintains its activity after multiple reuses. Both acids produce good yields (up to ~100%) of polyisobutene with an average exo‐olefinic end‐group content for Sc(OTf)3 of 86% (Alfa Asear) and 75% (Aldrich), and 94% for Yb(OTf)3 (Aldrich). The molecular weights of poly(β‐pinene) and polyisobutene made by scandium(III) and ytterbium(III) trifluoromethanesulfonate, respectively, in combination with methanol are quite favorable at ambient temperature. [ABSTRACT FROM AUTHOR]

Oxygen‐redox‐based‐layered cathode materials are of great importance in realizing high‐energy‐density sodium‐ion batteries (SIBs) that can satisfy the demands of next‐generation energy storage technologies. However, Mn‐based‐layered materials (P2‐type Na‐poor Nay[AxMn1−x]O2, where A = alkali ions) still suffer from poor reversibility during oxygen‐redox reactions and low conductivity. In this work, the dual Li and Co replacement is investigated in P2‐type‐layered NaxMnO2. Experimentally and theoretically, it is demonstrated that the efficacy of the dual Li and Co replacement in Na0.6[Li0.15Co0.15Mn0.7]O2 is that it improves the structural and cycling stability despite the reversible Li migration from the transition metal layer during de‐/sodiation. Operando X‐ray diffraction and ex situ neutron diffraction analysis prove that the material maintains a P2‐type structure during the entire range of Na+ extraction and insertion with a small volume change of ≈4.3%. In Na0.6[Li0.15Co0.15Mn0.7]O2, the reversible electrochemical activity of Co3+/Co4+, Mn3+/Mn4+, and O2‐/(O2)n‐ redox is identified as a reliable mechanism for the remarkable stable electrochemical performance. From a broader perspective, this study highlights a possible design roadmap for developing cathode materials with optimized cationic and anionic activities and excellent structural stabilities for SIBs. [ABSTRACT FROM AUTHOR]

Biodegradable cationic waterborne polyurethanes (WPUs) were successfully prepared using poly(caprolactone) diol as the soft segment. To improve the mechanical performance, adhesive strength and water resistance of the WPU films, different amounts of trimethylol propane monooleate (TMPM) containing biodegradable long‐branched aliphatic chains were incorporated in the PU structure. The T‐peel strength of WPU‐3 reached 42.8 N/25 mm, which was about 324% higher than that of WPU (10.1 N/25 mm) without TMPM. On the other hand, the elongation at break of WPU‐5 was 811%. On enhancing the TMPM content from 0 to 7.8 wt %, the surface tension decreased from 53.6 to 41.5 mN/m and the water contact angle of the WPU films increased from 52.4 to 81.0°, whereas the water absorption was observed to decrease from 15.6% to 9.6%. The fracture mechanism of the WPU films transformed from the brittle failure to the ductile fracture. The experiment results showed the cationic WPU modified by TMPM displayed excellent film‐forming property flexibility and adhesion, the surface tension of WPU dispersion and crystallinity of the resulting film were significantly reduced. For the first time, a biodegradable cationic WPU has been prepared by modification with TMPM, which can be employed for constructing the eco‐friendly biodegradable cationic WPUs. [ABSTRACT FROM AUTHOR]

Herein, stable cationic and anionic redox in an O3‐type layered Na[Ni2/3Ru1/3]O2 cathode for sodium‐ion batteries (SIBs) is revealed. Density functional theory (DFT) calculation shows that the electron density features change in density of state with mixing of delocalized valence states as well as localized deeper energy states of O(p), Ni(d), and Ru(d) for the highly desodiated Na1−x[Ni2/3Ru1/3]O2 electrode, revealing the covalent characteristic of the transition metal (TM)O and TMTM bonds in the charged system. These properties lead to cycling stability for 200 cycles, with ≈79% of the capacity retained at a rate of 1C (210 mA g−1). Operando X‐ray diffraction, X‐ray absorption spectroscopy, and DFT calculations reveal the reversible electrochemical activity of the Ni2+/Ni3+ and O2−/O1− redox reactions, which are sustainable throughout the cycles. In addition, no loss of oxygen from the crystal structure of Na[Ni2/3Ru1/3]O2 occurs according to differential electrochemical mass spectrometry. The findings provide additional insight into the complex mechanism of the oxygen redox activity of high‐capacity O3‐type cathode materials for SIBs, encouraging further studies on their development. [ABSTRACT FROM AUTHOR]

Two series of monotailed and bolaphiles surfactants having quaternary ammonium bromide polar head have been synthesized and characterized. The critical micelle concentration (CMC) of the synthesized cationic surfactants was determined by conductimetric method. According to CMC values, the increase in alkyl chain length leads to a decrease in CMC and the bola‐type exhibits a higher CMC than their counterpart's monotailed. [ABSTRACT FROM AUTHOR]

The influence of the structure of cationic molybdenum imido alkylidene N‐heterocyclic carbene (NHC) catalysts, i. e. of [Mo(N‐2‐tert‐butyl‐C6H4) (CHCMe2Ph)(NHC)X+ B(ArF)4−] (NHC=1,3‐di(2‐Pr)imidazol‐2‐ylidene (iPr), 1,3‐dimesitylimidazol‐2‐ylidene (IMes); X=pyrrolide, OCH(CF3)2, B(ArF)4−=tetrakis(3,5‐bis(trifluoromethyl)phenyl)borate) and of [Mo(N‐3,5‐Me2‐C6H3)(CHCMe2Ph)(NHC)(CH3CN)X+ B(ArF)4−] (NHC=1,3‐dimesitylimidazol‐2‐ylidene, 1,3‐dimesitylimidazolin‐2‐ylidene (IMesH2); X=CF3SO3, OCPh(CF3)2) on E/Z‐selectivity in the ring‐opening cross‐metathesis (ROCM) of endo, endo‐2,3‐dicarbomethoxynorborn‐5‐ene (endo, endo‐DCMNBE), exo, exo‐2,3‐dicarbomethoxynorborn‐5‐ene (exo, exo‐DCMNBE), endo, exo‐2,3‐dicarbomethoxynorborn‐5‐ene ((+) DCMNBE) and 2,3‐exo,exo‐bis(acetoxymethyl)‐7‐oxabicyclo[2.2.l]hept‐5‐ene (7‐oxa‐NBE) with 1‐pentene, styrene, allyltrimethylsilane, allyl benzyl ether, allyl phenyl ether and allyl ethyl ether has been studied. With the exception of the ROCM reaction of endo, endo‐DCMNBE with styrene, all other ROCM reactions of endo, endo‐DCMNBE proceeded under thermodynamic control without any post‐metathesis isomerization reactions with full retention of the configuration of the newly formed 1,2‐disubstituted double bond as confirmed by kinetic studies. Similar accounts for selected homometathesis reactions. Catalyst structure‐selectivity correlations based on the buried volume, Vbur, of the N‐imido ligand are presented. [ABSTRACT FROM AUTHOR]

The design of intracellular drug delivery vehicles demands an in‐depth understanding of their internalization and function upon entering the cell to tailor the physicochemical characteristics of these platforms and achieve efficacious treatments. Polymeric cationic systems have been broadly accepted to be membrane disruptive thus being beneficial for drug delivery inside the cell. However, if excessive destabilization takes place, it can lead to adverse effects. One of the strategies used to modulate the cationic charge is the incorporation of hydrophobic moieties, thus increasing the hydrophobic content. We have demonstrated the successful synthesis of nanogels based on diethylaminoethyl methacrylate and poly(ethylene glycol) methyl ether methacrylate. Addition of the hydrophobic monomers tert‐butyl methacrylate or 2‐(tert‐butylamino)ethyl methacrylate shows improved polymer hydrophobicity and modulation of the critical swelling pH. Here, we evaluate the cytocompatibility, uptake, and function of these membrane‐destabilizing cationic methacrylated nanogels using in vitro models. The obtained results suggest that the incorporation of hydrophobic monomers decreases the cytotoxicity of the nanogels to epithelial colorectal adenocarcinoma cells. Furthermore, analysis of the internalization pathways of these vehicles using inhibitors and imaging flow cytometry showed a significant decrease in uptake when macropinocytosis/phagocytosis inhibitors were present. The membrane‐disruptive abilities of the cationic polymeric nanogels were confirmed using three different models. They demonstrated to cause hemolysis in sheep erythrocytes, lactate dehydrogenase leakage from a model cell line, and disrupt giant unilamellar vesicles. These findings provide new insights of the potential of polymeric nanoformulations for intracellular delivery. [ABSTRACT FROM AUTHOR]

Abstract: The formation of positively charged polystyrene latex particles via the surfactant‐free emulsion polymerization of styrene with cationic initiator is investigated. Using the comonomer (vinylbenzyl)trimethyl‐ammonium chloride (VBTMAC) it is shown that the particle size can be tuned rather precisely between above 350 nm and below 70 nm. The simple functional dependence of the particle size on the inverse cube root of the comonomer concentration leads to propose, with reasonable assumptions, that VBTMAC comonomer addition allows the separation of nucleation and growth for this reaction. Thereby the comonomer concentration determines the nucleation rate and number of particles produced, while the styrene amount determines by how much the nucleated particles grow. Support for this model is obtained through zeta potential measurements at different pH values. The latter confirmed that the surface density of cationic groups resulting from the comonomer relative to that of groups resulting from the initiator decreases with decreasing comonomer concentration. [ABSTRACT FROM AUTHOR]

ABSTRACT Cationic, amphiphilic microgels of differing compositions based on hydrophilic, pH, and thermoresponsive 2-(dimethylamino)ethyl methacrylate (DMAEMA) and hydrophobic, nonionic n-butyl acrylate (BuA) are synthesized using a lab-on-a-chip device. Hydrophobic oil-in-water (o/w) droplets are generated via a microfluidic platform, with the dispersed (droplet) phase containing the DMAEMA and BuA, alongside the hydrophobic cross-linker, ethylene glycol dimethacrylate, and a free radical initiator in an organic solvent. Finally, the hydrophobic droplets are photopolymerized via a UV light source as they traverse the microfluidic channel to produce the cationic amphiphilic microgels. This platform enables the rapid, automated, and in situ production of amphiphilic microgels, which do not match the core-shell structure of conventionally prepared microgels but are instead based on random amphiphilic copolymers of DMAEMA and BuA between the hydrophobic cross-links. The microgels are characterized in terms of their swelling and encapsulation abilities, which are found to be influenced by both the pH response and the hydrophobic content of the microgels. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 59-66 [ABSTRACT FROM AUTHOR]

The rise in resistant bacteria strains worldwide is proving to be a challenge to the healthcare industry. These 'superbugs' are emerging faster than the rate of new antibiotic discovery. This has a heavy impact on medical devices as they are susceptible to biofilm production. Antimicrobial resistance (AMR) causes infections to be difficult to treat, especially postimplantation of a medical device. To prevent bacterial adhesion on devices, various types are coatings are introduced. By binding antibiotics to polymers, an effective adhesive coating on the surface can be created. However, with AMR on the rise, these polymers are losing their efficacy in the application. Another class of antimicrobial polymers with a different mode of mechanism will be explored in this project. Biocidal polymers are effective antimicrobial agents as they rely on the electrostatic interactions between the polymeric charged groups and the charged microbial membrane. Polyethylenimine (PEI) can be modified to achieve a macromolecule containing various charged cationic groups. Quaternizing low-molecular-weight PEI with different alkyl groups of short, long, and aromatic groups will give rise to various structural differences. The structure of the quaternized PEI is characterized, and its antimicrobial activity and compatibility are shown to be remarkably improved. [ABSTRACT FROM AUTHOR]

The first enantioselective total synthesis of the bisnorditerpene (+)-(5β,8α,10α)-8-hydroxy-13-methylpodocarpa-9(11),13-diene-3,12-dione ( 1) was accomplished in 7 steps with 18.5 % overall yield from known aldehyde and chiral epoxide. Key steps of the synthesis include a cationic domino cyclization used to construct the [6,6,6] fused framework, and an oxidative dearomatization reaction used to form the 1,4-quinoid moiety. [ABSTRACT FROM AUTHOR]

Pyrylium salts are found to be effective initiators for both photochemical and thermal cationic polymerization of epoxy resin. The photopolymerization results show that triphenylpyrylium salt derivatives are the most efficient structures. These compounds also exhibit some thermal reactivity at room temperature in the absence of light. However in such case, the gel time of the resin is quite high. Therefore, to speed up the thermal reaction, nucleophilic compounds are added as coinitiators, these compounds being known to yield a fast decomposition of pyrylium salts. This indeed increases the polymerization of epoxy resin at room temperature, opening the way to the development of quite efficient dual-cure photochemical/thermal initiating system for cationic polymerization. [ABSTRACT FROM AUTHOR]

Bioflocculants have been previously recognized as an alternative to synthetic polymers due to their renewable sources and biodegradability. In this study, the flocculating activity of lysozyme on kaolin suspensions was investigated and compared to a known flocculant, a cationic polyacrylamide. Lysozyme was found to significantly aid in the flocculation of kaolin particles. The flocculating activity of lysozyme on kaolin was affected by the pH of the suspensions, while the addition of Mg2+ and Ca2+ ions did not have a significant effect. Potential industrial applications such as the flocculation of powdered activated carbon and algae suspensions were investigated and the addition of lysozyme resulted in significant flocculation. Furthermore, the flocculating properties of lysozyme are independent of its enzymatic activity. Our results indicate that lysozyme acts as a low molecular mass cationic polymer, where the main mechanism for flocculation on negatively-charged particles is charge neutralization. Other cationic proteins could potentially be used as bioflocculants to enhance solid-liquid separation. [ABSTRACT FROM AUTHOR]

The methyl acrylamide propyl dimethyl butyl ammonium chloride (DMAPMA-C) and allyl-β-cyclodextrin (A-β-CD) were synthesized separately and then jointly copolymerized with acrylamide (AM) to form a novel cationic acrylamide polymer P(AM/A-β-CD/DMAPMA-C) through aqueous redox free-radical polymerization. The structure of the copolymer was characterized using Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM). Subsequently, a series of experiments were carried out to investigate its comprehensive performances, including temperature resistance, salt tolerance, aqueous stability, and sandpack flooding experiments. In addition, the rheological properties of P(AM/A-β-CD/DMAPMA-C) were also tested and calculated. The results showed that P(AM/A-β-CD/DMAPMA-C) possessed higher salt tolerance, temperature resistance, and aqueous stability than polyacrylamide (PAM). The rheological properties also indicated its applicability for enhanced oil recovery. The copolymer could significantly increase the oil recovery of 15.47%, which indicated its potential application for enhancing oil recovery in the oilfield. [ABSTRACT FROM AUTHOR]

The acyclic diene metathesis (ADMET) polymerization of 6-hydroxy-1,10-undecadiene ( M1) and 6-acetoxy-1,10-undecadiene ( M2) by the action of two different catalysts, i.e., the second-generation Grubbs-Hoveyda system ([RuCl2(IMesH2)(CH-2-(2-PrO-C6H4)]) ( 1) and the dicationic ruthenium alkylidene [Ru(DMF)3(IMesH2)(CH-2-(2-PrO-C6H4)] ( 2, IMesH2 = 1,3-dimesitylimidazolin-2-ylidene) is reported. Biphasic conditions using 1-butyl-2,3-dimethylimidazolium tetrafluoroborate ([BDMIM+BF4−]) and 1,2,4-trichlorobenzene (TCB) are applied. Under the chosen conditions ( T = 75 °C, 20 mbar), the use of catalyst 1 results only in the formation of low-molecular-weight polymers ( [ABSTRACT FROM AUTHOR]

The partitioning of corrosion inhibitor (CI) products is a measure of their potential to protect oilfield pipelines. In this paper the hydrophilic-lipophilic deviation (HLD) model is first used to quantify their partitioning in terms of the characteristic curvature ( C) of a series of anionic (alkoxylated phosphate esters) and cationic (alkoxylated amines, aromatic amines, imidazoline acetates and quaternary amines) actives. This parameter is expressed over a range of pHs within which pipeline corrosion occurs. The HLD model is next used to predict the partitioning of each active from water into toluene at increased salinities. Linear mixing rules are lastly used to predict the characteristic curvature of Product A ( C) as a function of the C of a subset of actives. [ABSTRACT FROM AUTHOR]

Efficient gene transfer is a critical goal in retroviral transduction. Several peptides capable of forming amyloid fibrils, such as the 39-residue semen-derived infection-enhancing peptide (SEVI), have demonstrated the ability to boost retroviral gene delivery. Here, a 13-residue peptide P13 (Ac-671NWFDITNWLWYIK683) derived from the membrane-proximal external region of the human immunodeficiency virus type 1 (HIV-1) gp41 transmembrane protein, together with its 16-residue peptide derivative (P16) were found to enhance HIV-1 infection significantly. Both peptides, P13 and P16, could form amyloid fibril structures to potently enhance HIV-1 infectivity. Further investigations showed that both aromatic Trp residues and cationic Lys residues contributed to the enhancement of HIV-1 infection by these two active peptides. P16 could more effectively augment HIV-1 YU-2 infection than SEVI, implying its potential applications as a tool in the lab to improve gene transfer rates. Copyright © 2013 European Peptide Society and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Mixtures of trisiloxane type nonionic silicone surfactant (SS) with sodium dodecylsulfate, tetradecyltrimethylammonium bromide or tert-octylphenol ethoxylated with 9.5 ethylene oxide groups were studied in water at 30 °C by dilute aqueous solution phase diagrams, surface tension and dilute solution viscosity methods. The cloud points for the silicone surfactant aqueous solutions increased upon addition of hydrocarbon surfactants indicating the formation of hydrophilic complexes in mixture solutions. The scrutiny of the surface tension isotherms plotted as a function of SS concentration revealed that competitive adsorption effects are the characteristic features in these mixtures depending upon the SS concentration. Otherwise the isotherms exhibited two break points and the difference of concentration between the two break points increased with the increase in SS concentration indicating the cooperative nature of interactions. The micellar mole fractions of individual surfactants were determined by Rublingh's regular solution theory; interaction parameters and activity coefficients were evaluated and interpreted in terms of synergistic type interactions in these mixtures. The surface active parameters in mixture solutions were estimated and their analysis shows that the molecular species in the mixture solutions have a preferential tendency for adsorption at the air/water interface than in association form in the bulk solution. The effect of hydrocarbon surfactants on the intrinsic viscosity of SS micelles was monitored and related to the enhanced hydration in mixed micelles. [ABSTRACT FROM AUTHOR]

Surface properties of the dodecyl isothiouronium cationic surfactant in a mixed solvent of water and polyethylene glycol of different molecular weights varied from ethylene glycol to polyethylene glycol-600 were determined using surface tension and conductivity measurements. The results showed an increase in the surface properties including critical micelle concentration, effectiveness and efficiency, compared to the surfactant in pure water as the solvent. The interaction between the cationic surfactant and the glycols was described and the molecular weight of the different glycols was rationalized. [ABSTRACT FROM AUTHOR]

We have carried out mixed micellization of pentanediyl-α,ω-bis(dimethyl cetylammonium bromide) (G5) with conventional cationic cetylpyridinium chloride (CPC) and nonionic polyoxyethylene (20) cetyl ether (C16E20) in aqueous media and explored their antimicrobial activity in single and binary systems against Escherichia coli ( E.coli), Pseudomonas aeruginosa ( P. aeruginosa) and Staphylococcus aureus ( S. aureus). The compounds tested showed excellent antibacterial activity: 0.76-3.38 g/l minimum inhibitory concentration (MIC) and were more active against gram +ve bacteria. For surfactant mixtures G5-C16E20 > G5-CPC, the ionic-nonionic binary surfactant showed greater antibacterial activity. The experimental results of this study may be profitably used to understand and predict the antibacterial activity of gemini-conventional surfactant systems and provide valuable information for selection of surfactant for microbiocidal action. [ABSTRACT FROM AUTHOR]

Minimally invasive and non-destructive methods to quantify glycosaminoglycans (GAGs) in articular cartilage extracellular matrix are of significant interest for the biochemical analysis of cartilage and diagnosis and tracking of osteoarthritis in vivo. Here, we report the use of cationic iodinated contrast agents in comparison to conventional anionic contrast agents for the quantitative monitoring of GAG concentrations with peripheral quantitative computed tomography. Using an ex vivo bovine osteochondral plug model, the cationic contrast agents were evaluated for their ability to distribute into articular cartilage and generate a positive relationship with GAG content. The cationic agents resulted in much higher equilibrium X-ray attenuations in cartilage extracellular matrix (ECM) than anionic agents. Experiments with samples subjected to enzymatic GAG degradation demonstrated that the cationic agents were up to five times more sensitive ( p = 0.0001) to changes in GAG content and had a 24% higher correlation ( p = 0.002) compared to the anionic agent ( R = 0.86, p < 0.0001 compared with R = 0.62, p = 0.004). The natural inhomogeneous distribution of GAGs in the ECM could clearly be identified in undegraded samples. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:704-709, 2011 [ABSTRACT FROM AUTHOR]

The physico-chemical properties of mixed surfactant aqueous solutions at various proportions of dodecyltrimethyl ammonium bromide DTAB and undecafluoro n-pentyl decaoxyethylene ether C5F11EO10 have been investigated at 25 °C using surface tension and conductivity measurements. The critical micelle concentration and superficial minimum tension have been experimentally estimated for different DTAB molar fractions. The micellar composition and mutual interaction parameters have been deduced on the basis the theoretical treatments proposed by Clint, Rubingh, and Motomura. The results show a significant synergism effect at about equimolarity of DTAB/C5F11EO10 system probably due to the efficient electrostatic self-repulsion reduction between DTAB cationic head groups related to the presence of the nonionic surfactant in the mixed micelles. [ABSTRACT FROM AUTHOR]

Modification of carbon materials such as graphite and glassy carbon in bulk quantities using diazonium salts is developed. We used both 4-nitrobenzenediazonium tetrafluoroborate and 1-antharaquinonediazonium chloride to modify graphite and glassy carbon surfaces. Experiments were carried out in the presence and absence of hypophosphorous acid and the mechanism involved in both cases were studied using cyclic voltammetry. The observed peak potentials for both the 4-nitrophenyl and 1-anthraquinonyl modified materials were found to differ depending on whether or not the hypophosphorous acid reducing agent was used. In the absence of hypophosphorous acid the derivatisation reaction was inferred to go through a cationic intermediate, whilst in the presence of the hypophosphorous acid the mechanism likely involves either a purely radical intermediate or a mixture of radical and cationic species. Derivatisation experiments from 5 to 70°C allowed us to determine the optimum derivatisation temperature for both cases, in the presence and absence of hypophosphorous acid. Optimum temperature was 20°C for the former and 35°C for the later. Copyright © 2008 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Transcutaneous immunization presents a major challenge on account of poor permeability of antigens through the skin barrier. To overcome this limitation, the deformable liposome could be a better method for transcutaneous delivery of these antigens. In this study, hepatitis B surface antigen (HBsAg) plasmid DNA–cationic complex deformable liposome was utilized as a mode for enhanced immunity against the antigen. Deformable liposome was prepared by conventional rotary evaporation method and characterized for various parameters such as vesicles shape and surface morphology, size and size distribution, entrapment efficiency, elasticity and stability. The immune stimulating activity was studied by measuring serum anti-HBsAg titre and cytokines level (interleukin-4 and interferon-γ) following topical application of liposome in BALB/c mice and results were compared with deformable liposome encapsulated DNA applied topically as well as naked DNA and pure recombinant HBsAg, administered intramuscularly. It was observed that deformable liposome elicited a comparable serum antibody titre and endogenous cytokines levels compared to other vaccinations. The study signifies the potential of deformable liposome as DNA vaccine carriers for effective transcutaneous immunization. [ABSTRACT FROM AUTHOR]

A series of cationic surfactants was prepared using economical raw materials. The chemical structures of the prepared compounds were confirmed using elemental analysis, FTIR and 1H-NMR spectra, and melting point determination. The synthesized surfactants were evaluated as oil-field protective additives. In this regard, several surface properties of the synthesized surfactants were studied including surface tension, critical micelle concentration, effectiveness, efficiency, maximum surface excess and minimum surface area. The results obtained from the surface activity measurements were correlated to their chemical structures. The emulsification power measurements for solutions of these surfactants showed their low emulsifying tendency towards paraffin and crude oil. The synthesized surfactants also exhibited high biocidal activity towards gram-positive and gram-negative bacteria and fungi. This activity was increased by increasing the hydrophobic chain length. The corrosion inhibition measurement of these surfactants for mild steel alloys in acidic media using a weight loss technique showed good protection of mild steel alloys against acidic environments. These properties qualify the synthesized compounds as economical oil-field protective additives. [ABSTRACT FROM AUTHOR]

In this study, the surface tension of mixtures of cationic surfactant dodecyl trimethylammonium bromide (DTAB) and anionic surfactant sodium perfluorooctanoate (SPFO) was evaluated as a function of DTAB-SPFO composition and total surfactant concentration, with and without added electrolyte. It was found that the critical micelle concentration (CMC) of these mixtures was reduced by more than two orders of magnitude when compared to the CMC of SPFO and DTAB alone. The surface tension, after CMC, of the mixtures was close to that of SPFO with added electrolyte and even lower than that of SPFO without added electrolyte. Using the appropriate, combination of SPFO and DTAB, surface tensions near 18 mJ/m2 were obtained using a concentration 1/500 of that required for SPFO alone. When these results were compared to those obtained for DTAB-sodium octanoate (SOCT) mixtures, it was evident that the DTAB-SPFO system shows a larger degree of synergism than the DTAB-SOCT system. Contact angle measurements on Teflon® surfaces corroborates that the lower surface tension of DTAB-SPFO mixtures improves wetting on these hydrophobic surfaces. Using the regular solution theory to interpret the data of CMC and C45mJ/m2 (monolayer formation) versus DTAB-SPFO composition, it was concluded that even when small concentrations of SPFO are introduced in the mixture, the composition of the micelles (at the CMC) and monolayer adsorbed at the air-water interface tends to be equimolar in SPFO and DTAB. [ABSTRACT FROM AUTHOR]

This research evaluated middle-phase microemulsion formation by varying the mole ratio of anionic and cationic surfactants in mixtures with four different oils (trichloroethylene, n-hexane, limonene, and n-hexadecane). Mixtures of a double-tailed anionic surfactant (sodium dihexyl sulfosuccinate, SDHS) and an unbalanced-tail (i.e., doubletailed with tails of different length) cationic surfactant (benzethonium chloride, BCl) were able to form microemulsions without alcohol addition. The amount of NaCl required to form the middle-phase microemulsion decreased dramatically as an equimolar anionic-cationic surfactant mixture was approached. Although the mixture of anionic and cationic surfactants demonstrated a higher critical microemulsion concentration (cμc) compared to the anionic surfactant alone, the Winsor Type IV single-phase microemulsion started at lower surfactant concentrations for the anionic-cationic mixture than for the anionic surfactant alone. Under optimum middlephase microemulsion conditions, mixed anionic-cationic surfactant systems solubilized more oil than the anionic surfactant alone. Pretreatment detergency studies were conducted to test the capacity of these mixed surfactant systems to remove oil form fabrics. It was found that anionic-rich mixed surfactant formulations yielded the largest oil removal, followed by cationic-rich systems. [ABSTRACT FROM AUTHOR]

Although mixtures of anionic and cationic surfactants can show great synergism, their potential to precipitate and form liquid crystals has limited their use. Previous studies have shown that alcohol addition can prevent liquid crystal formation, thereby allowing formation of middle-phase microemulsions with mixed anionic-cationic systems. This research investigates the role of surfactant selection in designing alcohol-free anionic-cationic microemulsions. Microemulsion phase behavior was studied for three anionic-cationic surfactant systems and three oils of widely varying hydrophobicity [trichloroethylene (TCE), hexane, and n-hexadecane]. Consistent with our hypothesis, using a branched surfactant and surfactants with varying tail length allowed us to form alcohol-free middle-phase microemulsion using mixed anionic-cationic systems (i.e., liquid crystals did not form). The anionic to cationic molar ratio required to form middle-phase microemulsions approached 1∶1 for univalent surfactants as oil hydrophobicity increased (i.e., TCE to hexane to n-hexadecane); even for these equimolar systems, liquid crystal formation was avoided. To test the use of these anionic-cationic surfactant mixtures in surfactant-enhanced subsurface remediation, we performed soil column studies: Greater than 95% of the oil was extracted in 2.5 pore volumes using an anionic-rich surfactant system. By contrast, cationic-rich systems performed very poorly (<1% oil removal), reflecting significant losses of the cationic-rich surfactant system in the porous media. The results thus suggest that, when properly designed, anionic-rich mixtures of anionic and cationic surfactants can be efficient for environmental remediation. By corollary, other industrial applications and consumer products should also find these mixtures advantageous. [ABSTRACT FROM AUTHOR]

A new type of cleavable cationic surfactant, based on the ortho ester link, is described. Ortho ester amines with alkyl chain lengths from C8 to C16 were synthesized from a short-chain ortho ester, a fatty alcohol, and an amino acohol. The ortho ester amine was subsequently quaternized with methyl chloride, yielding a cationic surfactant. The structures were confirmed by 1H and 13C nuclear magnetic resonance and the surface chemical properties were investigated by measuring both static and dynamic surface tensions. The results were compared to standard n-alkyl trimethyl ammonium bromides. The critical micelle concentrations were found to vary rather widely, whereas the surface tensions in some cases were comparatively low. The short alkyl chain ortho ester quaternaries were found to have low surface tensions at short surface ages and to induce rapid wetting of a hydrophobic surface in dynamic tests. Additionally, the new surfactants were found to hydrolyze rapidly under mild acidic conditions, as measured by both titation and monitoring of the dynamic surface tension. Further, they showed excellent long-term stability at pH 10 in dilute aqueous solutions. The effect of added electrolyte on rate of hydrolysis was also investigated. A marked enhancement in the hydrolysis rate was found when NaBr was added, whereas NaCl did not have the same effect. The new surfactants could potentially be used to provide temporary surfactant action in application areas such as disinfection, fabric care, personal care, chain lubrication, and mineral flotation as well as in textile processes such as dyeing or scouring. [ABSTRACT FROM AUTHOR]

We present a comprehensive review of the literature devoted to the analysis of surfactants. The period covered is 1995 through 1998. We address patents, reviews, books, journal articles, and any conference proceedings abstracted by Chemical Abstract Services. We consider classical, instrumental, and state-of-the-art analytical applications, including those not in common practice but in a developmental stage. We also include analytical techniques that make use of surfactants for improved performance, although such treatment is not comprehensive. Literature from foreign language sources is covered as completely as practical. [ABSTRACT FROM AUTHOR]

We present a comprehensive review of the literature devoted to the analysis of surfactants. The period covered is 1995 through 1998. We address patents, reviews, books, journal articles, and any conference proceedings abstracted by Chemical Abstract Services. We consider classical, instrumental, and state-of-the-art analytical applications, including those not in common practice but in a developmental stage. We also include analytical techniques that make use of surfactants for improved performance, although such treatment is not comprehensive. Literature from foreign language sources is covered as completely as practical. [ABSTRACT FROM AUTHOR]

Based on the association of bacterial plaque with the initiation of chronic gingivitis and progression of chronic periodontitis. chemical antiplaque agents have been employed both in prevention of periodontal disease and its treatment. In supragingival plaque control regimens, chlorhexidine has not been superceded as a chemical anti-plaque agent, although other compounds have been shown to be useful. The local side-effects of chlorhexidine and other cationic antiseptics, however, limit their long-term use for prevention. Extrinsic tooth staining in particular remains the greatest problem. Short-term anti-plaque uses for chlorhexidine include (1) as an adjunct to mechanical cleaning in the initial oral hygiene phase of treatment, (2) in situations where mechanical oral hygiene is difficult, including (i) postsurgery (ii) intermaxillary fixation. (iii) fixed orthodontic therapy. (iv) physically and mentally handicapped individuals, (v) systemic diseases with oral manifestations such as leukaemia. More recent interest in chlorhexidine has resulted from the delivery of compounds subgingivaliy in the treatment of chronic periodontitis. Such methods have extended the use of chlorhexidine into areas inaccessible to the action of antimicrobial drugs delivered locally by conventional means, such as tooth brushing or mouth rinsing. Available evidence suggests that chlorhexidine may not be as effective as some antimicrobial drugs whose activity is more specific for those organisms considered particularly pathogenic to the periodontal tissues. [ABSTRACT FROM AUTHOR]

Surface-active agents (surfactants) are characterized by the possession of 2 different moieties, both polar and non-polar regions on the same molecule. Surfactants are broadly classified as anionic, cationic, amphoteric, or non-ionic, according to the nature of hydrophile yielded in aqueous solution. In currently marketed household, personal and industrial cleaners,anionic surfactants are the most common class because of their relative ability to solubilize fats and oils, lower the surface tension of aqueous solutions, or form microemulsions. Many surfactants elicit irritant reactions when applied to the skin, partially due to their relative ability to solubilize lipid membranes. Hence, surfactants have become important implements in skin irritation investigations. In general, the physicochemical properties of surfactants are a crucial factor in eliciting skin irritation. Anionic surfactants are broadly accepted as potent irritants to human and animal skin. Cationic surfactants are reputedly at least equally irritating, but more cytotoxic than anionic, while the irritation potential of non-ionic surfactants is considered the lowest. Such classification of innumerable surfactants is convenient and held in high practical esteem. However, the categorization does not permit the exact determination of irritation and cytotoxicity potential of each surfactant. Ranking of surfactant skin irritancy and cytologist obtained by both in vitro and in vivo assays provides a helpful orientation for future work. [ABSTRACT FROM AUTHOR]

Front Cover: Nowaday, pyrylium salts could be considerate to be effective initiators for both photochemical and thermal cationic polymerization of epoxy resin. Triphenylpyrylium salt derivatives are the most efficient structures to photopolymerize the resin. Beside, these compounds also exhibit some thermal reactivity at room temperature in the absence of light, a fact opening the way to the development of new dual cure photochemical/thermal initiating system. Further details can be found in the article by David Maréchal, Xavier Allonas,* Maxime Lecompère, Adrien Criqui page 1169. [ABSTRACT FROM AUTHOR]

Minimally invasive and non-destructive methods to quantify glycosaminoglycans (GAGs) in articular cartilage extracellular matrix are of significant interest for the biochemical analysis of cartilage and diagnosis and tracking of osteoarthritis in vivo. Here, we report the use of cationic iodinated contrast agents in comparison to conventional anionic contrast agents for the quantitative monitoring of GAG concentrations with peripheral quantitative computed tomography. Using an ex vivo bovine osteochondral plug model, the cationic contrast agents were evaluated for their ability to distribute into articular cartilage and generate a positive relationship with GAG content. The cationic agents resulted in much higher equilibrium X-ray attenuations in cartilage extracellular matrix (ECM) than anionic agents. Experiments with samples subjected to enzymatic GAG degradation demonstrated that the cationic agents were up to five times more sensitive (p = 0.0001) to changes in GAG content and had a 24% higher correlation (p = 0.002) compared to the anionic agent (R2 = 0.86, p < 0.0001 compared with R2 = 0.62, p = 0.004). The natural inhomogeneous distribution of GAGs in the ECM could clearly be identified in undegraded samples., Chemistry and Chemical Biology