Phase behavior of salt-free catanionic surfactant aqueous solutions with fullerene C60 solubilized

A salt-free catanionic surfactant system, tetradecyltrimethylammonium laurate (TTAL), was constructed by mixing tetradecyltrimethylammonium hydroxide (TTAOH) and lauric acid (LA). The H+ and OH- counterions form water (TTAOH+LA-->TTAL+H2O), leaving the solution salt-free. The phase behaviors at fixing the total surfactant concentration (cTTAL) to be 33.0 and 55.0 mmol L(-1), respectively, were studied through varying the molar ratio of r=nLA/nTTAOH from 0.70 to 1.20. With an increasing value of r, one observed an L1-region, an Lalpha/L1 two-phase region with a birefringent Lalpha-phase at the top, and finally a single Lalpha-phase. The ability to solubilize a fullerene mixture of C60 and C70 of different phases in different regions was tested. The colloidal stability and phase behavior of different phases with embedded fullerenes were investigated as a function of r, cTTAL, and weight ratio of fullerene to surfactant (WF/WTTAL). The 33.0 or 55.0 mmol L(-1) zero-charged vesicle-phase at r=1.00 could solubilize a considerable amount of fullerenes without macroscopic phase separation and obvious vesicular structure breakage. However, these colloidal solutions became unstable at lower concentrations of surfactants, and a precipitate would be observed at the bottom. The micellar (L1-phase) solubilization at the TTAOH-rich side was less pronounced compared to the vesicular solubilization of the zero-charged vesicle-phase, and the solubilizing ability decreased at higher r values. In the Lalpha/L1 two-phase region, a brown or dark-brown Lalpha-phase was usually found at the top of a colorless or yellowish L1-phase, indicating that most of the fullerenes were embedded in the upper Lalpha-phase. The influence of fullerene incorporation on the property of the zero-charged TTAL vesicle-phase was also investigated, and evidence has been found that the system tended to be more fluid after fullerenes were incorporated into the hydrophobic microdomains of aggregates.     

Phase behavior and properties of reverse vesicles in salt-free catanionic surfactant mixtures

Salt-free 1:1 cationic/anionic (catanionic) surfactant mixture tetradecyltrimethylammonium laurate (TTAL) could be prepared by mixing equimolar tetradecyltrimethylammonium hydroxide (TTAOH) and lauric acid (LA) in water. Given the condition of suitable range of weight fraction of TTAL in total surfactant, rho=WTTAL/(WTTAL+WLA), and at existence of a small amount of water, it was found that the mixtures of so-obtained TTAL and LA could spontaneously form stable reverse vesicles in various organic solvents including toluene, tert-butylbenzene, and cyclohexane. The reverse vesicle phase shows a blue color against room light and exhibits strong birefringence under polarized microscope. The reverse vesicles are very sensitive to temperature change. Increasing temperature could make the rho values within which reverse vesicles were constructed move to higher values. In organic solvents of alkanes such as n-heptane, reverse vesicles could still form but become unstable upon time and centrifugation. Increasing temperature could accelerate phase separation, and finally a gel-like bottom phase was usually observed. Interestingly, the stable reverse vesicles formed by so-called salt-free catanionic surfactant mixtures still show some resistance against adding inorganic salts. They can trap inorganic ions such as Zn2+ and S2- into their hydrophilic layers. This opens the door for template applications of reverse vesicles to prepare inorganic nanoparticles.     

Phase behavior, rheological property, and transmutation of vesicles in fluorocarbon and hydrocarbon surfactant mixtures

We present a detailed study of a salt-free cationic/anionic (catanionic) surfactant system where a strongly alkaline cationic surfactant (tetradecyltrimethylammonium hydroxide, TTAOH) was mixed with a single-chain fluorocarbon acid (nonadecafluorodecanoic acid, NFDA) and a hyperbranched hydrocarbon acid [di-(2-ethylhexyl)phosphoric acid, DEHPA] in water. Typically the concentration of TTAOH is fixed while the total concentration and mixing molar ratio of NFDA and DEHPA is varied. In the absence of DEHPA and at a TTAOH concentration of 80 mmol·L(-1), an isotropic L(1) phase, an L(1)/L(α) two-phase region, and a single L(α) phase were observed successively with increasing mixing molar ratio of NFDA to TTAOH (n(NFDA)/n(TTAOH)). In the NFDA-rich region (n(NFDA)/n(TTAOH) > 1), a small amount of excess NFDA can be solubilized into the L(α) phase while a large excess of NFDA eventually leads to phase separation. When NFDA is replaced gradually by DEHPA, the mixed system of TTAOH/NFDA/DEHPA/H(2)O follows the same phase sequence as that of the TTAOH/NFDA/H(2)O system and the phase boundaries remain almost unchanged. However, the viscoelasticity of the samples in the single L(α) phase region becomes higher at the same total surfactant concentration as characterized by rheological measurements. Cryo-transmission electron microscopic (cryo-TEM) observations revealed a microstructural evolution from unilamellar vesicles to multilamellar ones and finally to gaint onions. The size of the vesicle and number of lamella can be controlled by adjusting the molar ratio of NFDA to DEHPA. The dynamic properties of the vesicular solutions have also been investigated. It is found that the yield stress and the storage modulus are time-dependent after a static mixing process between the two different types of vesicle solutions, indicating the occurrence of a dynamic fusion between the two types of vesicles. The microenvironmental changes induced by aggregate transitions were probed by (19)F NMR as well as (31)P NMR measurements. Upon replacement of NFDA by DEHPA, the signal from the (19)F atoms adjacent to the hydrophilic headgroup disappears and that from the (19)F atoms on the main chain becomes sharper. This could be interpreted as an increase of microfluidity in the mixed vesicle bilayers at higher content of DEHPA, whose alkyl chains are expected to have a lower chain melting point. Our results provide basic knowledge on vesicle formation and their structural evolution in salt-free catanionic surfactant systems containing mixed ion pairs, which may contribute to a deeper understanding of the rules governing the formation and properties of surfactant self-assembly.     

Two routes to vesicle formation: metal-ligand complexation and ionic interactions

Two routes to vesicle formation were designed to prepare uni- and multilamellar vesicles in salt-free aqueous solutions of surfactants. The formation of a surfactant complex between a double-chain anionic surfactant with a divalent-metal ion as the counterion and a single-chain zwitterionic surfactant with the polar group of amine-oxide group is described for the first time as a powerful driving force for vesicle-phases constructed from salt-free mixtures of aqueous surfactant solutions. As a typical example, a Zn(2+)-induced charged complex fluid, vesicle-phase has been studied in aqueous mixtures of tetradecyldimethylamine oxide (C(14)DMAO) and zinc 2,2-dihydroperfluorooctanoate [Zn(OOCCH(2)C(6)F(13))(2)]. This ionically charged vesicle-phase formed due to surfactant complexation has interesting rheological properties and is not shielded by excess salts because there are no counterions in the solution. Such a vesicle-phase of surfactant complex is important for many applications; for example, the vesicle-phase was further used to produce in situ the vesicle-phase of the salt-free cationic/anionic (catanionic) surfactants, C(14)DMAOH(+)-(-)OOCCH(2)C(6)F(13). The salt-free catanionic vesicle-phase could be produced through injecting H(2)S gas into the C(14)DMAO/Zn(OOCCH(2)C(6)F(13))(2) vesicle-phase, because the zwitterionic surfactant C(14)DMAO can be charged by the H(+) released from H(2)S to become a cationic surfactant and Zn(2+) was precipitated as ZnS. After the ZnS precipitates were removed from C(14)DMAO/Zn(OOCCH(2)C(6)F(13))(2) solutions, the final mixed solution does not contain excess salts as do other cationic/anionic surfactant systems. Both the C(14)DMAO-Zn(OOCCH(2)C(6)F(13))(2) complex and the resulting catanionic C(14)DMAOH(+)-(-)OOCCH(2)C(6)F(13) solution are birefringent Lalpha-phase solutions that consist of uni- and multilamellar vesicles. Ring-shaped semiconductor ZnS materials with encapsulated ZnS precipitates and regular spherical ZnS particles were prepared, which resulted in a transition from vesicles composed of metal-ligand complexes to vesicles held together by ionic interactions in the salt-free aqueous systems. This strategy should provide a new method to prepare inorganic materials. The present routes to form vesicles solve a problem: how to prepare nanomaterials using surfactant self-assembly, with structure controlled not by the growing material, but by the phase behavior of the surfactants.     

Aggregation behavior and adsorption properties of salt-free catanionic surfactant mixtures containing tetradecyltrimethyl ammonium salts

The aggregation behavior of salt-free catanionic surfactants, tetradecyltrimethyl ammonium hydroxide (TTAOH)/fatty acid (FA) including octanoic acid (OA), decylic acid (DA) and lauric acid (LA) in aqueous solutions were studied. The critical micelle concentration(cmc), surface tension at cmc (γ_cmc), surface excess (Г_max), mean molecular surface area (A_min), adsorption efficiency (pc₂₀) and surface tension reduction effectiveness (π_cmc) were obtained from surface tension isotherms. The influence of temperature on the surface tension of salt-free TTAOH/FA (TTAOF) systems was investigated. Data of adsorption dynamics indicated that at fixed adsorption time, the order of adsorption capacity was TTAOH?相似文献   

Densely stacked multilamellar and oligovesicular vesicles, bilayer cylinders, and tubes joining with vesicles of a salt-free catanionic extractant and surfactant system

In the phase diagram of an excellent extractant of rare earth metal ions, di(2-ethylhexyl) phosphate (HDEHP, commercial name P204), mixing with a cationic trimethyltetradecylammonium hydroxide (TTAOH) in water, a birefringent Lalpha phase was found, which consists of densely stacked multilamellar vesicles. The densely stacked multilamellar vesicles are remarkably deformed, as observed by means of cryotransmission electron microscopy (cryo-TEM). Further, self-assembled structures-oligovesicular vesicles, bilayer cylinders, and tubes joining with vesicles-were also observed. The self-assembled phase is transparent, anisotropic, and highly viscous, possessing elastic properties determined by rheological measurements. This is the first time that birefringent Lalpha phase with remarkably deformed amphiphilic bilayer membranes has been constructed through combining a hydrophobic organic extractant having double chains with a water-soluble surfactant having a single chain, which may direct primarily toward acquiring an understanding of the mechanism of salt-free catanionic vesicles and secondarily to determine if vesicle-extraction technology utilizing extractants is possible.     

Phase behavior and rheological properties of a salt-free catanionic surfactant TTAOH/LA/H2O system

Conventional cationic and anionic (catanionic) surfactant mixtures tend to form precipitates at the mixing molar ratio of the cationic and anionic surfactant of 1:1 because of the excess salt formed by their counterions. By using OH- and H+ as the counterions, however, excess salt can be eliminated, and salt-free catanionic systems can be obtained. Here, we report the detailed phase behavior and rheological properties of salt-free catanionic surfactant system of tetradecyltrimethylammonium hydroxide (TTAOH)/lauric acid (LA)/H2O. With the variation of mixing molar ratio of LA to TTAOH (rho=nLA/nTTAOH), the system exhibits much richer phase behavior induced by growth and transition of aggregates. Correspondingly, the rheological property of the system changes significantly. Take the series of samples with fixed total surfactant concentration (cT) to be 15 mg.mL(-1), the system only forms a low viscous L 1 phase with a Newton fluid character at the TTAOH-rich side. With increasing rho, first a shear-thickening L1 phase region is observed at 0.70or=1.05, and finally, at rho>or=1.13, the excess LA will separate from the bulk solution and form a white top layer. Investigations were also carried out by varying c T at fixed rho and by changing temperature, respectively. It was found micelle growth would be greatly suppressed at higher temperatures. However, the vesicle phases showed a considerable resistance against temperature rise.     

Investigations into the bending constant and edge energy of bilayers of salt-free catanionic vesicles

Using molecular dynamics simulation, we performed theoretical calculations on the curvature constant and edge energy of bilayers of salt-free, zero-charged, cationic and anionic (catanionic) surfactant vesicles composed of alkylammonium cations (C(m)(+)) and fatty acid anions (C(n)(-)). Both the minimum size and edge energy of vesicles were calculated to examine the relation between the length of the surfactant molecules and the mechanical properties of the catanionic bilayers. Our simulation results clearly demonstrate that, when the chain lengths of the cationic and anionic surfactants are equal, both the edge energy and the rigidity of the catanionic bilayers increase dramatically, changing from around 0.36 to 2.77 kBT·nm(-1) and around 0.86 to 6.51 kBT·nm(-1), respectively. For the smallest catanionic vesicles, the curvature is not uniform and the surfactant molecules adopt a multicurvature arrangement in the vesicle bilayers. We suspect that the multicurvature bending of bilayers of catanionic vesicles is a common phenomenon in rigid bilayer systems, which could aid understanding of ion transport through bilayer membranes.     

Effect of addition of dendritic C60 amphiphiles on the structure of cationic surfactant solutions

The aggregation behavior of two water-soluble carboxylic C60 derivatives, dendritic methano[60] fullerene octadeca acid (1) and ennea acid (2), in aqueous solutions was investigated. Both 1 and 2 were highly soluble in pure water and buffer solutions with pH >or=7.0. Their spectral properties, especially those in the visible region, were found to be influenced greatly by solution parameters and additives. In pure water, dynamic laser light scattering (DLS) measurements revealed that both 1 and 2 could form aggregates. When 1 or 2 was added to micelle solution of a cationic surfactant, tetradecyltrimethylammonium hydroxide (TTAOH), unilamellar vesicles with diameters of several hundreds of nanometers were detected by freeze-fracture transmission electron microscope and DLS both below and above the critical micellar concentration of TTAOH. Vesicle formation was greatly suppressed when 1 or 2 was added to tetradecyltrimethylammonium bromide micelle solution and no vesicles were detected for 1 or 2 mixed with the aqueous solutions of tetrabutylammonium hydroxide or tetramethylammonium hydroxide, indicating that counterions and the hydrophobic chain length of the cationic surfactants played important roles in vesicle formation. At the same time, for mixtures of 1 and 2 with anionic surfactant sodium dodecyl sulfate, no vesicles were detected. In highly concentrated NaCl solutions, it was found that 1 and 2 could also form vesicles, which could be due to the shielding of the electrostatic interactions among hydrophilic parts of 1 and 2.     

Phase behavior and rheological properties of salt-free catanionic TTAOH/DA/H2O system in the presence of hydrophilic and hydrophobic salts

In the cationic and anionic (catanionic) surfactant mixed system, tetradecyltrimethylammonium hydroxide (TTAOH)/decanoic acid (DA)/H(2)O, abundant phase behaviors were obtained in the presence of hydrophilic and hydrophobic salts. The microstructures of typical L(α) phases with the different compositions were characterized by the transmission electron microscope (TEM) images. Aqueous double-phase transition induced by addition of hydrophilic salts was observed when the cationic surfactant was in excess. Salt-induced reversible vesicle phases could be obtained when the anionic surfactant was excess, whereas the vesicle phase at lower salinity behaves highly viscoelastic but is much less viscoelastic with high salinity which was demonstrated by measuring their rheological properties. The L(α) phase with the positive membrane charges can be finally transferred into an L(1) phase with added salts. The ion specificity of hydrophilic and hydrophobic salts is discussed, and the order of cations is summarized, which is significant for the further study of the Hofmeister effects on catanionic surfactant mixed systems.     

Vesicles of a new salt-free cat-anionic fluoro/hydrocarbon surfactant system

Weakly basic tetradecyldimethylaminoxide (C14DMAO) molecules can be protonated to form a cationic surfactant, C14DMAOH+, by an acidic fluorocarbon surfactant, an 8-2-fluorotelomer unsaturated acid (C7F15CF==CHCOOH), to form a salt-free cationic and anionic (cat-anionic) fluoro/hydrocarbon surfactant system in aqueous solution. The high Krafft point of C7F15CF==CHCOOH was largely reduced as a result of being mixed with a C14DMAO micelle solution. A study of the phase behavior of the new salt-free cat-anionic fluoro/hydrocarbon surfactant system clearly indicates the existence of a birefringent Lalpha-phase region at (25.0+/-0.1) degrees C. The birefringent Lalpha phase consists of vesicles, which include uni- and multilamellar vesicles with one to dozens of shells, and oligovesicular vesicles, as demonstrated by freeze-fracture and cryo-transmission electron microscopy (FF- and cryo-TEM) images. The size distribution and structural transitions in the salt-free cat-anionic fluoro/hydrocarbon surfactant system were studied by dynamic light scattering (DLS) and 1H and 19F NMR spectroscopy. The formation of a salt-free cat-anionic vesicle phase could be induced by the strong electrostatic interaction between the cationic hydrocarbon C14DMAOH+ and the anionic fluorocarbon C7F15CF==CHCOO-, which provided evidence that the electrostatic interaction between the cationic and anionic surfactants is larger than the nonsynergistic interaction between the stiff fluorocarbon and the soft hydrocarbon chains of the surfactants.     

SOLUBILIZATION SITES AND ACID-BASE FORMS OF DIBUCAINE-HYDROCHLORIDE IN NEUTRAL AND CHARGED MICELLAR SOLUTIONS

Steady-state and time-resolved emission spectroscopic techniques have been employed to characterize the drug species of dibucaine and to identify its location in micellar Triton X-100 (neutral), hexadecyltrimethyl ammonium bromide (cationic) and lithium dodecyl sulfate (anionic) solutions at 77 K. Under physiological conditions, the dibucaine is shown to exist in the free base form (D) while solubilized in the hydrocarbon core of neutral micelles. In cationic micellar solution, dibucaine exists as the monocation species (DH+) where the anesthetic is solubilized in the extramicellar aqueous solution and D is solubilized in the hydrophobic region with close proximity to the micellar interface. In the anionic micelles, interfacial solubilization is most consistent with a site in which the tertiary amino group of the monocation dibucaine (DH+) is anchored at the micellar interface with its quinoline analog penetrating the hydrophobic region. The distinct properties observed for the drug species (i.e. D and DH+) and their solubilization sites in micelles are consistent with a balance between hydrophobic forces, surface polarity and the interfacial electrostatic potential present in the micellar solubilization sites. These observations could lend insight into the molecular basis of pharmacological action, in particular the mechanism of local anesthetic drug transport across membranes.     

LA/C14DMAO/H2O体系多结构自组装体及其模板金纳米材料制备与性能

月桂酸(LA)与十四烷基二甲基氧化胺(C₁₄DMAO)形成的无盐阴/阳离子表面活性剂混合体系表现出丰富的相行为。运用冷冻蚀刻透射电子显微镜(FF-TEM)和偏光显微镜(POM)、差示扫描量热(DSC)、流变和[2]H NMR测定对体系相行为和微观结构进行了研究,发现水溶液中可自聚集形成胶束(L₁)、层状(L_αl)、囊泡(L_αν)和凝胶相。以胶束相和层状相为软模板制备了金纳米材料,运用透射电子显微镜(TEM)和能谱仪(EDS)表征了金纳米材料。与用传统阳离子表面活性剂溶液制备金纳米材料相比,该体系由于具有自身还原性而不需要加入还原剂NaBH₄。实验证明：还原过程不会破坏模板溶液原有微观结构,且可通过调控聚集体结构实现控制制备金纳米材料形貌的目的。HK-2细胞的噻唑蓝(MTT)比色法实验进一步证明,本体系制备的球形金纳米材料作为基因载体具有高效和低毒的特点,在基因治疗中具有潜在的实际应用价值,可为寻求安全可靠的基因治疗途径提供实验数据和理论参考。     

Interaction between zero-charged catanionic vesicles and PEO–PPO–PEO triblock copolymers

We investigate the interaction between zero-charged catanionic vesicles and PEO–PPO–PEO (poly(ethylene oxide–poly(propylene oxide)–poly(ethylene oxide)) triblock copolymers. The 25-mg mL^?1 aqueous solution of tetradecyltrimethylammonium laurate (TTAL) contains closely packed uni- and multi-lamellar vesicles and shows viscoelastic properties with a dominant elastic modulus (G′) over a viscous modulus (G″). When a small amount of F127 ((EO)₉₇(PO)₆₉(EO)₉₇) or F68 ((EO)₇₆(PO)₂₉(EO)₇₆) was added, an improvement of the viscoelasticity was observed at suitable polymer concentrations. Freeze–fracture transmission electron microscopy (FF-TEM) observations on an F68-containing system revealed interesting aggregate transition from vesicles to flexible tubules and back to vesicles. The improvement of the viscoelasticity of the vesicular solution containing F68 or F127 can be explained by the formation of tubule and polymer–vesicle associates, while no such phenomenon was noticed for P123 ((EO)₁₉(PO)₆₉(EO)₁₉) which has the highest propylene oxide (PO) content and the strongest ability to self-associate in aqueous solution. In all the cases, vesicles will be destroyed and phase separation can be observed at high polymer contents (>5-mg mL^?1).     

Metal-ligand-coordinated vesicles and vesicle-assisted preparation of calcium oxalate

A Ca(2+) -ligand-coordinated vesicle phase was prepared from a mixture of tetradecyldimethylamine oxide (C14DMAO) and calcium tetradecylamidomethyl sulfate [(CH3(CH2)13NHCOCH2OSO3)2Ca] in aqueous solution. At the appropriate mixing ratios, Ca(2+) -ligand coordination results in the formation of molecular bilayers because Ca(2+) can firmly bind to the head groups of C14DMAO and (CH3(CH2)13NHCOCH2OSO3)2Ca by complexation which reduces the area of head group. In this system, no counterions in aqueous solution exist because of the Ca(2+) -ligand coordination, and the bilayer membranes are not shielded by salts, i.e., a salt-free but charged molecular bilayer. The structures of the birefringent solutions of (CH3(CH2)13NHCOCH2OSO3)2Ca and C14DMAO mixtures were determined by transmission electron microscopy (TEM) images and rheological measurements, demonstrating that the birefringent sample solutions consist of vesicles. The Ca(2+) -ligand complex vesicle phase was used as a microreactor to prepare calcium oxalate (CaC2O4) crystals. Dimethyl oxalate, as a precursor, can hydrolyze to oxalic acid and methanol. Oxalic acid should precipitate Ca(2+) ions binding to the head groups of C14DMAO and (CH3(CH2)13NHCOCH2OSO3)2Ca to produce CaC2O4 crystals (Ca(2+) + H2C2O4 --> CaC2O4 (downward arrow) + 2H+). The obtained particles were CaC2O4 monohydrate, which were dominated by (020) faces. CaC2O4 precipitates were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FT-IR) analysis. After removal of CaC2O4 precipitates, a new cationic and anionic (catanionic) vesicle phase was constructed through electrostatic interaction between cationic C14DMAOH+ (C14DMAO + H+ --> C14DMAOH+) and anionic CH3(CH12)13 NHCOCH2OSO3-.     

DNA encapsulation by biocompatible catanionic vesicles

The encapsulation of DNA by catanionic vesicles has been investigated; the vesicles are composed of one cationic surfactant, in excess, and one anionic. Since cationic systems are often toxic, we introduced a novel divalent cationic amino-acid-based amphiphile, which may enhance transfection and appears to be nontoxic, in our catanionic vesicle mixtures. The cationic amphiphile is arginine-N-lauroyl amide dihydrochloride (ALA), while the anionic one is sodium cetylsulfate (SCS). Vesicles formed spontaneously in aqueous mixtures of the two surfactants and were characterized with respect to internal structure and size by cryogenic transmission electron microscopy (cryo-TEM); the vesicles are markedly polydisperse. The results are compared with a study of an analogous system based on a short-chained anionic surfactant, sodium octylsulfate (SOS). Addition of DNA to catanionic vesicles resulted in associative phase separation at very low DNA concentrations; there is a separation into a precipitate and a supernatant solution; the latter is first bluish but becomes clearer as more DNA is added. From studies using cryo-TEM and small angle X-ray scattering (SAXS) it is demonstrated that there is a lamellar structure with DNA arranged between the amphiphile bilayers. Comparing the SOS containing DNA-vesicle complexes with the SCS ones, an increase in the repeat distance is perceived for SCS. Regarding the phase-separating DNA-amphiphile particles, cryo-TEM demonstrates a large and nonmonotonic variation of particle size as the DNA-amphiphile ratio is varied, with the largest particles obtained in the vicinity of overall charge neutrality. No major differences in phase behavior were noticed for the systems here presented as compared with those based on classical cationic surfactants. However, the prospect of using these systems in real biological applications offers a great advantage.     

Incorporation and release behavior of amitriptylene in core-shell-corona type triblock copolymer micelles

A cationic antidepressant drug, amitriptylene (AMT), was successfully incorporated into core-shell-corona micelles of poly[styrene-b-sodium 2-(acrylamido)-2-methyl-1-propanesulfonate-b-ethylene oxide] (PS-b-PAMPS-b-PEO). Zeta-potential measurements revealed that both electrostatic and hydrophobic interactions contributed to the binding of the drug to the polymer. The AMT/PS-b-PAMPS-b-PEO nanocomplexes were characterized by dynamic light scattering, scanning electron microscopy, and transmission electron microscopy. The hydrodynamic diameter of the AMT loaded nanocomplexes decreased from 80 to 40nm depending on the amount of the drug loaded on the polymer. This is attributed to the cancellation of the negative charge of the PAMPS group by the cationic drug. The AMT/PS-b-PAMPS-b-PEO nanocomplexes were stable in aqueous solution exhibiting no aggregation or no precipitation for several months. Release of the AMT from the nanocomplexes was investigated in vitro in salt-free and 0.1M NaCl solutions. The drug was released faster in the 0.1M NaCl solution than in the salt-free solution. This is due to the shielding effect of the salt on the electrostatic interaction. However, in both cases, the drug release mainly occurs by the Fickian diffusion mechanism.     

碳氟醇对阳离子表面活性剂表面活性及胶团反离子结合度的影响

用表面张力及电动势法研究了C₁₀H₂₁N(CH₃)3Br、C₁₂H₂₅N(CH₃)3Br与C₃F₇CH₂OH混合水溶液的表面与胶团性质。结果表明,对于阳离子表面活性剂,C₃F₇CH₂OH的加入一方面增加表面活性,另一方面降低胶团反离子结合度。后者不同于阴离子表面活性剂/C₃F₇CH₂OH混合体系,可归因于C₃F₇CH₂OH略有酸性,因而具备一些类似阴离子表面活性剂的性质。     

Synthesis of two pentaarylated [60]fullerene derivatives Ar_5C_(60)-H (Ar = p-MeC_6H_4, m-MeC_6H_4) and their novel electrochemical properties

Through one pot reaction of C60 with organocopper/magne-sium reagent ( p - MeQ H4 )2 CuMgBr or ( m - MeC6 H )2 -CuMgBr prepared from CuBr-Me2S and p-MeC6H4MgBr or m-MeC6H4MgBr and subsequent quenching with aqueous NH4Cl, two pentaarylated [60] fullerene derivatives (p-MeC6H4)5C60H (1) and (m-MeC6H4)5C60H (2) have been synthesized in 94% and 96% yields, respectively. While known compound 1 prepared via this improved method is unambiguously identified, new compound 2 is fully characterized by elemental analysis, IR, UV-vis, 1H NMR and 13C NMR spectroscopies. Additionally, electrochemical study shows that the two [60] fullerene derivatives 1 and 2 in dichloromethane solution display two sequential one-electron reductions which are shifted by about 0.4V towards more negative potential values with respect to free C60. Such remarkable cathodic shift is attributed to the multiple breakage of the double-bond conjugation within the fullerene core.     

Production of monoclonal antibodies against fullerene C60 and development of a fullerene enzyme immunoassay

The aim of the present study was to produce monoclonal anti-fullerene C(60) antibodies and to develop the enzyme immunoassay for the detection in the first use of free fullerene C(60) both in solutions and in multicomponent biological probes. The immunization of mice with the conjugate of fullerene C(60) carboxylic derivative with thyroglobulin synthesized by carbodiimide activation led to the production of eight clones of anti-fullerene antibodies. The specificity of the antibody-fullerene binding was confirmed. Indirect competitive enzyme-linked immunosorbent assay (ELISA) was developed for the determination of water-soluble protein-conjugated fullerene, the fullerene aminocaproic acid, fullerenol and for pristine fullerene in solution. To solubilize extremely hydrophobic free fullerene C(60) a specially selected water-organic mixture compatible with immunoassay was proposed. The detection limit of free fullerene C(60) in solution was 2 μg L(-1). Fullerene C(60) was also detected by ELISA in organ homogenates of rats intraperitoneally or intragastrically administered with fullerene. To reduce the influence of biomatrices on the assay results a technique was developed for the biological sample pretreatment by the extraction of C(60) from bioprobe by toluene followed by the evaporation of toluene and dissolution of the fullerene-containing extract in the selected water-organic media. The ELISA procedure in the first use allowed the detection of fullerene C(60) in different tissues.