The influence of the structure of the surface of functional organosilicas on the adsorption of cholic acid

High-dispersity silica was modified by functional groups capable of protonating or carrying a constant positive charge. IR and UV spectroscopy, temperature-programmed thermogravimetry, pH metry, and quantitative analysis of grafted compounds were used to determine the structure of the surface of functional organosilicas. The adsorption of primary bile (cholic) acid on silica adsorbents and cholestiramine was studied. The adsorption of cholic acid from solutions with pH 2–8 was substantially higher on adsorbents with positively charged surfaces. The silica adsorbents synthesized were shown to have higher cholic acid adsorption parameters compared with adsorbents used in medicine.     

The influence of the structure of the surface of hydrophilic-hydrophobic silicas on the adsorption of cholic acid

We synthesized hydrophilic-hydrophobic silicas with uniform and island arrangements of functional groups over the surface and various degrees of surface hydrophobicity. The adsorption of cholic acid on hydrophilic-hydrophobic silicas was studied as depending on acid concentration in solution. Adsorption was shown to be largely determined by dispersion interactions between hydrophobic surface regions and steroid cholic acid segments. Enhanced adsorption ability was observed for hydrophilic-hydrophobic silica with a mosaic surface structure. This was caused by the contribution of geometric cholic acid imprints into the total adsorption.     

Bacterial adhesion inhibition of the quaternary ammonium functionalized silica nanoparticles

Quaternary ammonium compounds have been considered as excellent antibacterial agents due to their effective biocidal activity, long term durability and environmentally friendly performance. In this work, 3-(trimethoxysilyl)-propyldimethyloctadecylammonium chloride as a quaternary ammonium silane was applied for the surface modification of silica nanoparticles. The quaternary ammonium silane provided silica surface with hydrophobicity and antibacterial properties. In addition, the glass surface which was coated with the surface modified silica nanoparticles presented bacterial growth inhibition activity. For comparison of bacterial growth resistance, hydrophobic silane (alkyl functionalized silane) modified silica nanoparticles and pristine silica nanoparticles were prepared. As a result of bacterial adhesion test, the quaternary ammonium functionalized silica nanoparticles exhibited the enhanced inhibition performance against growth of Gram-negative Escherichia coli (96.6%), Gram-positive Staphylococcus aureus (98.5%) and Deinococcus geothermalis (99.6%) compared to pristine silica nanoparticles. These bacteria resistances also were stronger than that of hydrophobically modified silica nanoparticles. It could be explained that the improved bacteria inhibition performance originated from the synergistic effect of hydrophobicity and antibacterial property of quaternary ammonium silane. Additionally, the antimicrobial efficacy of the fabricated nanoparticles increased with decreasing size of the nanoparticles.     

以硅胶为载体合成水不溶性季铵盐类杀菌剂

硅胶载体;水不溶性杀菌剂;以硅胶为载体合成水不溶性季铵盐类杀菌剂     

Bifunctionalized SBA-15 as a novel micropipette tip sorbent for selective removal and enrichment of biomolecules

Selective enrichment or removal of specific proteins prior to analysis can minimize nonspecific interferences as well as information loss, which has been an important issue in current proteomics fields. In this work, two kinds of mesoporous silica SBA-15 (mean pore diameter of 5 nm and 7 nm), bifunctionalized with quaternary ammonium and C18 groups via silylanization reaction, was used to investigate the adsorption behavior for different proteins (bovine serum albumin (BSA), ovalbumin (OVA), hemoglobin (Hb), lysozyme (Lys) and cytochrome c (cyt c)). As possessing anion exchange (quaternary ammonium) groups, the bifunctionalized SBA-15 showed selective adsorption of the negative charged proteins, BSA and OVA. Based on these properties, sequential fractionation based on different SBA-15 materials as micropipette tip sorbents was developed for sample preparation prior to protein analysis. As expected, after the sequential treatment of the sample, the detection signal of the high abundant BSA was significantly decreased and that of the low abundant cyt c was obviously enlarged, which solved the problem that low abundant protein was suppressed by adjacent high abundant protein. The sample preparation technique significantly improved protein identification and this sequential fractionation approach could be potentially applied to extend information on the protein identification for biological samples with a wide dynamic range.     

Adsorption of Cationic Surfactants on Highly Dispersed Silica

Comparative study was made of adsorption of cationic surfactants, decamethoxine, ethonium, and cetyltrimethylammonium bromide, on a highly dispersed amorphous silica at different pH values. Contrary to the adsorption of monoquaternary ammonium compound, cetyltrimethylammonium bromide, the adsorption of bis(quaternary ammonium) compounds, ethonium and decamethoxine, was found to be caused mainly by electrostatic interaction. The adsorption of antiseptic decamethoxine is reversible at pH 6; this may be used to design carriers capable of controlled drug release into the surrounding medium.     

Estimation of the dissociation constants for functional groups on modified and unmodified silica gel supports from the relationship between electroosmotic flow velocity and pH

Electroosmotic volume flow was directly observed in a simple instrument consisting of 1 cm long a home-made support, packed between two polyethylene frits in the polypropylene tube. Equations relating electroosmotic flow (EOF) velocity and pH for two functional groups on the surface of the solid materials were developed. With these equations, we can estimate the dissociation constants of two different kinds of functional groups on modified silica gel materials simultaneously. The dissociation constants of silanol groups, benzene sulfonic acid groups, and alkyl quaternary ammonium groups on the modified and unmodified silica gel supports were estimated. The estimated pK values of the silanol groups on the silica gel and modified silica gel surfaces are between 4.0 and 4.3. The estimated pK values of the benzene sulfonic acid groups and alkyl quaternary ammonium groups on the surface of the modified silica gel are 2.6 and 8.6, respectively.     

High-performance liquid chromatography on dynamically modified silica : III. Modification of silica with long-chain and symmetrical quarternary ammonium compounds

The influence of the nature of quaternary ammonium compounds on retention in high-performance liquid chromatography on dynamically modified silica was investigated. Adsorption isotherms were determined on bare silica (LiChrosorb Si 60) for four alkyltrimethylammonium bromides and two symmetrical tetraalkylammonium bromides, each containing 15–21 carbon atoms. It was found that only the long-chain quaternary ammonium ions are adsorbed on to the silica surface in appreciable amounts and that the affinity increasing number of carbon atoms in the alkyl chain. The maximum amount that can be adsorbed per gram of silica is of the same order of magnitude for each of the four long-chain quaternary ammonium compounds. This amount, however, is reached at lower concentrations in the eluent the longer is the alkyl chain.The retention of five test compounds was determined over the whole concentration range investigated for each of the modiflying agents. The surfactant concentration that causes maximum retention for four of five test compounds coincides with its critical micellar concentration. The retention mechanisms and the influence of the type of the modifying agent on selectivity are discussed, and compared with published results on related experiments on chemically bonded stationary phases.     

2种癸二酸咪唑啉季铵盐的合成及缓蚀性能评价

合成了2种癸二酸咪唑啉季铵盐癸二酸-水杨酸咪唑啉季铵盐(SSAI)和癸二酸咪唑啉季铵盐(SAI),并采用失重法和电化学方法研究了这2种咪唑啉季铵盐对N80钢在1 mol/L HCl溶液中的缓蚀性能和吸附行为。 结果表明,在1 mol/L HCl溶液中这2种化合物对N80钢均有较好的缓蚀作用,缓蚀效率大小顺序为SSAI＞SAI。 SSAI和SAI均为混合偏阳极型缓蚀剂。 2种化合物在N80钢表面的吸附服从Langmuir吸附等温式,属于化学吸附。     

An FTIR study of the adsorption of surfactants on silica

The absorption of cetyltrimethyl ammonium bromide onto silica was studied by FTIR as an example of the interaction of cationic surfactants with surfaces of medium polarity. It was found that the free silanol groups of the silica interacted strongly with the surfactant and that the methylene group adsorption bands varied with coverage in both frequency and width. These results could be interpreted in terms of chemisorption of a first layer of surfactant followed by physisorption of subsequent layers, or in terms of the inhomogeneity of the silica surface.     

高比表面季铵基树脂的结构调控及在三七叶总皂甙纯化中的应用研究

利用Davankov后交联反应,合成了一类兼具高比表面积和高功能基含量的季铵基(—N+(CH)3)吸附树脂,考察了树脂比表面积和功能基含量的调控规律,并将其用于三七叶总皂甙的进一步纯化.结果表明,当树脂比表面积为692m2/g,交换量为2.1mmol/g时,树脂具有最佳的纯化效果,只通过吸附—解吸一步工艺,产品纯度即可从32.0%提高到90%以上,皂甙的回收率高于95%.最后,初步探讨了树脂对皂甙和色素的吸附机理,认为树脂对皂甙的吸附是单纯的疏水性作用力,而对色素的吸附应为疏水-离子交换双重作用的协同效应.     

Intermolecular interactions in the bilirubin-cholate-silica system

Bilirubin-cholate interactions in aqueous solutions were studied. The constants of binding of bilirubin with taurocholate dimers and taurodeoxycholate trimers were calculated. The adsorption of bilirubin and cholates on the surface of highly dispersed silica was studied. It was shown that taurine-conjugated cholates are poorly adsorbed from micellar solutions on the silica surface, the specific amount of bilirubin adsorbed decreases with increasing concentration of cholates in the solution, the affinity of free bilirubin for the silica surface is independent of the nature of the cholic acid, and that the affinity of cholate-bilirubin complexes for the silica surface is lower than the affinity of free bilirubin.     

Capillary electrochromatography with a silica column with a dynamically modified cationic surfactant.

A novel mode of capillary electrochromatography (CEC), called dynamically modified silica-capillary electrochromatography, is described in this paper. The column packed with bare silica was dynamically modified with long chain quaternary ammonium salt, cetyltrimethylammonium bromide (CTAB), which was added into the mobile phase. CTAB ions were adsorbed onto the surface of bare silica, and the resulted hydrophobic layer on the silica gel was used as the stationary phase. Using the dynamically modified silica column, neutral solutes were separated by CEC. The highest number of theoretical plates obtained was about 71,500/m and the relative standard deviations for t0 and capacity factor of toluene were 4.7% and 4.9% for 20 consecutive runs, respectively. The separation mechanism of neutral solutes and the influence of mobile phase composition on the separation was investigated. The separation of nitrogen-containing solutes was carried out with this mode and the peak tailing of basic solute was effectively eliminated because the adsorption of basic solute on silica was blocked by the preferred adsorption of CTAB.     

Novel Porphyrin-Cholic Acid Conjugates as Receptors for Biologically Important Anions

A series of novel receptors showing high binding affinity in aqueous media for biologically important anions are reported. These naturally chromophoric porphyrin-based receptors contain cholic acids connected via quaternary alkyl ammonium amido linkages.     

Preparation of magnetic anion exchange resin and their adsorption kinetic behavior of reactive blue

Magnetic anion exchange resin(MD-1) was prepared from quaternization of magnetic copolymeric resin(glycidyl methacrylate -eo-divinylbenzene).For comparison,magnetic resin MD-0 without quaternization and non-magnetic resin(D-1) were also synthesized for the adsorption process.It was found that the adsorption was mainly contributed to the chemical interaction between quaternary ammonium groups and reactive blue RXHC.Due to the smaller size,MD-1 had faster adsorption and desorption kinetics than D-1.Coupled with the advantage of easy separation,the magnetic anion exchange resin was considered to be superior to common anion exchange resin in removal of reactive dye.     

Selective extraction of organic compounds as ion-pairs and adducts

Selective and easily regulated systems for extraction of organic compounds as ion-pairs and/or adducts are presented. The effect of different kinds of hydrophobic agents that give adducts in the organic phase are demonstrated: mesitylene for nitrophenols, ethyl acetate and diethyl ether for hexestrol (diphenol), lipophilic alcohols for organic ammonium ion-pairs, dibenzo-18-crown-6 for ion-pairs of primary ammonium ions, HDEHP for hydrophilic aminophenols (adrenaline, isoproterenol, synephrine). It is shown that the extraction selectivity decreases with increasing content of the complexing agent in the adduct. The influence of the hydrogen-bonding character of the counter-ion and the organic solvent on the selectivity of ion-pair extractions is demonstrated with ammonium compounds (nortriptyline, amitriptyline and N-methylainitriptyline) and inorganic anions. Highly hydrophilic anionic compounds (e.g., glucuronides, cholic acid derivatives) can be extracted into chloroform as ion-pairs with large quaternary alkylammonium ions. The extraction efficiency of the cation increases with the number of methylene groups to a limit which is due to co-extraction of other sample components (e.g., buffer anions).     

芳氧亚甲基咪唑啉季铵盐的合成及缓蚀性能评价

合成了苯氧亚甲基咪唑啉季铵盐（POAI）和萘氧亚甲基咪唑啉季铵盐（NOAI）,通过失重法、电化学方法研究了二者在1 mol/L HCl中对A3钢的缓蚀性能,并对二者在A3钢表面的吸附行为进行了探讨。 结果表明,二者在1 mol/L HCl中对A3钢均有较好的缓蚀作用,其中NOAI对A3钢的缓蚀性能优于POAI的缓蚀性能;两化合物均为混合型缓蚀剂。 缓蚀性能随缓蚀剂浓度和温度的增大而增大;二者在A3钢表面的吸附过程吸热,是化学吸附,符合Langmuir吸附等温式。     

Direct force measurements between adlayers consisting of poly(amidoamine) dendrimers with primary amino groups or quaternary ammonium groups

Adsorption of poly(amidoamine) generation 3 (PAMAM G3) dendrimer with surface amino groups or PAMAM G0 dendrimer with quaternary ammonium groups (C8qbG0) onto glass has been studied by colloidal probe atomic force microscopy. The adlayer-adlayer interactions for these adsorbates are quite different despite the fact that they are almost equal in the hydrodynamic radius. In aqueous PAMAM G3 dendrimer solutions the electrostatic repulsion is predominant. The conformation of the adsorbed layer is flat and the protrusion of the individual dendrimers is negligible. On the other hand, C8qbG0 behaves as a surfactant and the layered structure of C8qbG0 is expected to be a patchy bilayer. Dispersion stability of silica suspensions with the adsorption of these dendrimers can be correlated with the force data obtained.     

Adsorption of a cationic surfactant, miramistin, from aqueous solutions on the surface of highly dispersed silica

The adsorption of a universal antiseptic agent, the cationic surfactant miramistin, on the surface of highly dispersed silica has been studied. It has been shown that, when miramistin is adsorbed from acidic premicellar solutions, the main contribution to miramistin binding with the surface is made by hydrogen bonding between amide groups of surfactant molecules and silanol groups of silica, which is, at higher pH values, accompanied by ionic interaction between positively charged quaternary nitrogen atoms of miramistin and negatively charged dissociated silanol groups. In the case of adsorption from a micellar solution, an increase in the surface concentration of miramistin is almost independent of solution pH, because the second layer is predominantly formed due to hydrophobic interactions.     

Surface modification of poly(2‐hydroxyethyl methacrylate) hydrogel for contact lens application

The present study examined poly(2‐hydroxyethyl methacrylate) (PHEMA)‐based hydrogels that have been extensively used in biomedical applications, including contact lens. In this research, we aimed to reduce adsorption of protein components from tears and bacterial deposition by surface modification of the hydrogel with different functional groups that included carboxylic acid, primary amine, and quaternary ammonium. The PHEMA was treated with a solution of sulfuric acid for partial hydrolysis of the HEMA ester groups to induce acid groups on the surface of the hydrogel. Carboxylic acid groups of the modified PHEMA were converted to primary amine and quaternary ammonium groups via carbodiimide chemistry. The surface physical and chemical properties of different samples were investigated by atomic force microscopy and X‐ray photoelectron spectroscopy, respectively. We conducted the bicinchoninic acid assay to evaluate protein deposition from artificial tear fluid on samples. Antibacterial properties of the modified hydrogels were investigated with a culture of Staphylococcus aureus, one of the major causes of eye infections. Our data showed that positively charged amine and ammonium groups efficiently resisted protein adsorption and bacterial deposition compared to alcohol and carboxylic acid groups.