Synergistic anionic/zwitterionic mixed surfactant system with high emulsification efficiency for enhanced oil recovery in low permeability reservoirs

Emulsification is one of the important mechanisms of surfactant flooding. To improve oil recovery for low permeability reservoirs, a highly efficient emulsification oil flooding system consisting of anionic surfactant sodium alkyl glucosyl hydroxypropyl sulfonate(APGSHS) and zwitterionic surfactant octadecyl betaine(BS-18) is proposed. The performance of APGSHS/BS-18 mixed surfactant system was evaluated in terms of interfacial tension, emulsification capability, emulsion size and distribution, wettability alteration, temperature-resistance and salt-resistance. The emulsification speed was used to evaluate the emulsification ability of surfactant systems, and the results show that mixed surfactant systems can completely emulsify the crude oil into emulsions droplets even under low energy conditions. Meanwhile,the system exhibits good temperature and salt resistance. Finally, the best oil recovery of 25.45% is achieved for low permeability core by the mixed surfactant system with a total concentration of 0.3 wt%while the molar ratio of APGSHS:BS-18 is 4:6. The current study indicates that the anionic/zwitterionic mixed surfactant system can improve the oil flooding efficiency and is potential candidate for application in low permeability reservoirs.

Bacterial Cellulose/Zwitterionic Dual-network Porous Gel Polymer Electrolytes with High Ionic Conductivity

Bacterial cellulose(BC)was innovatively combined with zwitterionic copolymer acrylamide and sulfobetaine methacrylic acid ester[P(AM-co-SBMA)]to build a dual-network porous structure gel polymer electrolytes(GPEs)with high ionic conductivity.The dual network structure BC/P(AM-co-SBMA)gels were formed by a simple one-step polymerization method.The results show that ionic conductivity of BC/P(AM-co-SBMA)GPEs at the room temperature are 3.2×10^(-2) S/cm@1 M H_(2)SO_(4),4.5×10^(-2) S/cm@4 M KOH,and 3.6×10^(-2) S/cm@1 M NaCl,respectively.Using active carbon(AC)as the electrodes,BC/P(AM-co-SBMA)GPEs as both separator and electrolyte matrix,and 4 M KOH as the electrolyte,a symmetric solid supercapacitors(SSC)(AC-GPE-KOH)was assembled and testified.The specific capacitance of AC electrode is 173 F/g and remains 95.0%of the initial value after 5000 cycles and 86.2%after 10,000 cycles.

Recent advances in zwitterionic nanoscale drug delivery systems to overcome biological barriers

Nanoscale drug delivery systems(nDDS)have been employed widely in enhancing the therapeutic efficacy of drugs against diseases with reduced side effects.Although several nDDS have been successfully approved for clinical use up to now,biological barriers between the administration site and the target site hinder the wider clinical adoption of nDDS in disease treatment.Polyethylene glycol(PEG)-modification(or PEGylation)has been regarded as the gold standard for stabilising nDDS in complex biological environment.However,the accelerated blood clearance(ABC)of PEGylated nDDS after repeated injections becomes great challenges for their clinical applications.Zwitterionic polymer,a novel family of antifouling materials,have evolved as an alternative to PEG due to their super-hydrophilicity and biocompatibility.Zwitterionic nDDS could avoid the generation of ABC phenomenon and exhibit longer blood circulation time than the PEGylated analogues.More impressively,zwitterionic nDDS have recently been shown to overcome multiple biological barriers such as nonspecific organ distribution,pressure gradients,impermeable cell membranes and lysosomal degradation without the need of any complex chemical modifications.The realization of overcoming multiple biological barriers by zwitterionic nDDS may simplify the current overly complex design of nDDS,which could facilitate their better clinical translation.Herein,we summarise the recent progress of zwitterionic nDDS at overcoming various biological barriers and analyse their underlyingmechanisms.Finally,prospects and challenges are introduced to guide the rational design of zwitterionic nDDS for disease treatment.

Zwitterionic polymer-coated porous poly(vinyl acetate–divinyl benzene)microsphere: A new support for enhanced performance of immobilized lipase

Enzyme immobilization has attracted great attention for improving the performance of enzymes in industrial applications.This work was designed to create a new support for Candida rugosa lipase(CRL)immobilization.A porous poly(vinyl acetate–divinyl benzene)microsphere coated by a zwitterionic polymer,poly(maleic anhydride-alt-1-octadecene)and N,N-dimethylethylenediamine derivative,was developed for CRL immobilization via hydrophobic binding.The catalytic activity,reaction kinetics,stabilities and reusability of the immobilized CRL were investigated.It demonstrated the success of the zwitterionic polymer coating and subsequent CRL immobilization on the porous microsphere.The immobilized lipase(p2-MS-CRL)reached27.6 mg·g^-1 dry carrier and displayed a specific activity 1.5 times higher than free CRL.The increase of Vmax and decrease of Kmwere also observed,indicating the improvement of catalytic activity and enzyme-substrate affinity of the immobilized lipase.Besides,p2-MS-CRL exhibited significantly enhanced thermal stability and pH tolerance.The improved performance was considered due to the interfacial activation regulated by the hydrophobic interaction and stabilization effect arisen by the zwitterionic polymer coating.This study has thus proved the advantages of the zwitterionic polymer-coated porous carrier for lipase immobilization and its potential for further development in various enzyme immobilizations.

Fabrication and characterization of epoxylated zwitterionic copolymergrafted silica nanoparticle as a new support for lipase immobilization

Our previous work proved that the thermal stability of Candida rugosa lipase(CRL)immobilized on zwitterionic polymer(poly(carboxybetaine methacrylate))grafted silica nanoparticle(SNP)was much higher than that on poly(glycidyl methecrylate)(pGMA)grafted SNP,while the latter showed significantly increased activity.Inspired by the research,we have herein proposed to synthesize copolymers of zwitterionic sulfobetaine methacrylate(SBMA)and GMA for CRL immobilization.The copolymers were grafted onto SNP surface at three GMA/SBMA(G/S)molar ratios(G100/S0,G50/S50,G10/S90),followed by the covalent coupling of CRL to the surface copolymers.The immobilized CRLs on the corresponding supports were denoted as p(G100-S0)-CRL,p(G50-S50)-CRL and p(G10-S90)-CRL.The enzyme loading increased with the increase of GMA content in the copolymer,while the activity varied with the grafted copolymer composition.Kinetic study proved the improvement of enzyme-substrate affinity after immobilization.In comparison to p(G100-S0)-CRL,p(G50-S50)-CRL and p(G10-S90)-CRL presented remarkably enhanced thermal stability and pH tolerance,and p(G10-S90)-CRL showed the highest stability.These results suggest that the copolymer design is promising for development as a versatile platform for enzyme immobilization.

MOLECULAR ENGINEERING STUDIES ON NONTHROMBOGENIC BIOMATERIALS——A NOVEL CLASS OF NONTHROMBOGENIC BIOMATERIALS WITH ZWITTERIONIC STRUCTURE OF CARBOXYBETAINES

N,N-dimethyl-N-methacryloyloxyethyl-N-carboxyethyl ammonium(DMMCA)was graft-copolymerized onto thesurface of segmented poly(ether urethane)(SPEU)and PE film.The carboxybetaine structure on SPEU and PE filmsurfaces was confirmed by ATR-FTIR,XPS and water contact angle measurements.Through the experiments with plateletadhesion and protein adhesion assay in vitro,the two materials studied,including poly-DMMCA gel,all show excellentnonthrombogenicity.This confirms once again that the zwitterionic molecular structure on the surfaces of materials isessential for improving their nonthrombogenicity and biocompatibility.

Preparation of antifouling ultrafiltration membranes from copolymers of polysulfone and zwitterionic poly(arylene ether sulfone)s

The past few decades have witnessed rapid gains in our demands of antifouling membranes such as water purification membranes and hemodialysis membranes.A variety of methodologies have been proposed for improving the antifouling performance and the hemocompatibility of the membranes.In this study,a series of copolymers(PSF-PESSB)containing polysulfone(PSF)and poly(arylene ether sulfone)bearing pendant zwitterionic sulfobetaine groups(PESSB)were prepared via one-pot polycondensation.Subsequently,the ultrafiltration(UF)membranes were prepared from different zwitterion-containing copolymers.The prepared membranes showed high thermal stability and mechanical properties.Besides,it also displayed attractive antifouling performance and blood compatibility.Compared with the original PSF membrane,the amount of protein absorption on the modified membrane was reduced;the flux recovery ratio and the resistance to blood cells were significantly improved.The results of this work suggest that PSF-PESSB membranes are expected to be applied in blood purification.The introduction of zwitterion-containing polymers to membranes paves ways for developing advanced hemodialysis technologies for crucial process.

Zwitterionic monolayer grafted ceramic membrane with an antifouling performance for the efficient oil-water separation

Enormous demands on the separation of oil/water(O/W)emulsions in various industries,such as petrochemical,food and pharmaceutical industries,are looking for high performance and energy-efficient separation methods.Ceramic membranes have been used to deal with O/W emulsions,for its outstanding characteristics of easy-operation,high-flux,and long-term stability.However,membrane fouling is still a challenge in the industrial application of ceramic membranes.Herein,antifouling ceramic membranes were fabricated by grafting zwitterions on the membrane surface via an environment-friendly two-step grafting method,which improves the antifouling property and permeability.Successful grafting of such zwitterion on the ceramic surface was assessed by the combination of FTIR and XPS characterization.More importantly,the hydration can be formed by electrostatic interactions layer on the modified membrane,which was confirmed by TGA characterization.The antifouling performance of prepared zwitterionic ceramic membranes in the separation of O/W emulsions was systematically tested.The results suggested that zwitterion can significantly improve the flux of ceramic ultrafiltration membrane,and can also improve antifouling property dramatically by reducing the irreversible fouling in the separation of O/W emulsions.Therefore,zwitterionic ceramic membranes hold promising potentials as an antifouling,highly efficient and green method in the practical purification of the O/W emulsions.

Conjugation of a zwitterionic polymer with dimethyl chains to lipase significantly increases the enzyme activity and stability

Enzyme-polymer conjugates are complex molecules with great practical significance.This work was designed to develop a novel enzyme-polymer conjugate by covalently coupling a zwitterionic polymer with side dimethyl chains(pID)to Candida rugosa lipase(CRL)via the reaction between the anhydrides of polymer chains with the amino groups of the enzyme.The resulting two CRL-pID conjugates with different pID grafting densities were investigated in term of the catalytic activity,stability and structural changes.In comparison with native CRL,both the CRL conjugates displayed 2.2 times higher activity than the native enzyme,and showed an increase in the maximum reaction rate(V_(max))and a decrease in the Michaelis constant(K_(m)),thus resulting in about three-fold increases in the catalytic efficiency(k_(cat)/K_(m)).These are mainly attributed to the activation of lipase by the hydrophobic alky side chains.Moreover,the thermostability and pH tolerance of the lipase conjugates were significantly enhanced due to the stabilizing effect of the zwitterion moieties.For instance,a five-fold increase of the enzyme half-life at 50℃ for the high-pID conjugated CRL was observed.Spectroscopic studies reveal that the pID conjugation protected the enzyme in the changes in its microenvironment and conformation,well correlating with enhanced activity and stability of lipase conjugates.The findings indicate that enzyme conjugation to the zwitterionic polymer is promising for improving enzyme performance and deserves further development.

A zwitterionic polymer-inspired material mediated efficient CRISPR-Cas9 gene editing

The typeⅡ prokaryotic CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 (CRISPR/Cas9) adaptive immune system is a cutting-edge genome-editing toolbox.However,its applications are still limited by its inefficient transduction.Herein,we present a novel gene vector,the zwitterionic polymer-inspired material with branched structure (ZEBRA) for efficient CRISPR/Cas9 delivery.Polo-like kinase 1 (PLK1) acts as a master regulator of mitosis and overexpresses in multiple tumor cells.The Cas9 and single guide sgRNA (sgRNA)-encoded plasmid was transduced to knockout Plk1 gene,which was expected to inhibit the expression of PLK1.Our studies demonstrated that ZEBRA enabled to transduce the CRISPR/Cas9 system with large size into the cells efficiently.The transduction with ZEBRA was cell line dependent,which showed~10-fold higher in CD44-positive cancer cell lines compared with CD44-negative ones.Furthermore,ZEBRA induced highlevel expression of Cas9 proteins by the delivery of CRISPR/Cas9 and efficient gene editing of Plk1 gene,and inhibited the tumor cell growth significantly.This zwitterionic polymerinspired material is an effective and targeted gene delivery vector and further studies are required to explore its potential in gene delivery applications.

Novel Zwitterionic Surfactants: Synthesis and Surface Active Properties of N-(3-Alkoxy-2-Hydroxypropyl)-N, N-Dimethyl glycine Betaines

Five new zwitterionic surfactants with long chain alkyl betaine structure incorporated with hydroxylpropyl group have been synthesized. Their structures were identified by elemental analysis, IR (HNMR)-H-1, and (CNMR)-C-13. Surface tension experiments showed that these surfactants have higher surface activity than those without hydroxypropyl group. The values of CMC and gamma(CMC) of these surfactants have been determined.

Buffer standards for the physiological pH of the zwitterionic buffer 3-[<i>N</i>-tris(hydroxymethyl)methylamino]-2-hydroxypropanesulfonic Acid (TAPSO) From (278.15 to 328.15) K

The second dissociation constant, pK2, and related thermodynamic quantities for TAPSO have been previously determined and reported from the temperatures (278.15 to 328.15) K. In the current study there are five buffer solutions without NaCl and five buffer solutions with NaCl present which yield an ionic strength (I = 0.16 mol·kg-1) similar to that of blood plasma. These buffer solutions have been evaluated in the temperature range of (278.15 to 328.15) K using the extended Debye-Hückel equation, due to the limitations of the Bates-Guggenheim convention such that it is only valid when I -1. The liquid junction potential (Ej) values between the TAPSO solution and the saturated KCl calomel electrode solution have been estimated at (298.15 and 310.15) K using a flowing junction cell measurement. The previously mentioned Ej values have been used in determining the operational pH values at (298.15 and 310.15) K. These TAPSO buffer solutions are recommended as reference solutions for pH measurements in saline media with an ionic strength of I = 0.16 mol·kg-1.

Interactions in Aqueous Solution of a Zwitterionic Surfactant with a Water Treatment Protein from Moringa oleifera Seeds Studied by Surface Tension and Ultrasonic Velocity Measurements

The interaction of a zwitterionic surfactant with the water treatment protein extracted from Moringa oleifera has been investigated by surface tension and ultrasonic velocity measurements. The critical micelle concentration (CMC) of zwitterionic surfactant was determined to be 2.4 ± 0.3 mM by both techniques and the partial specific volume ν = 0.78 ± 0.06 cm3/g for the protein was found. There seems to be a mild interaction between the protein and the surfactant as shown by surface tension measurements. The ultrasonic velocity was found to decrease in the vicinity of the critical micelle concentration which may be due to micelle aggregates formation and the protein caused a shift of the surfactant’s CMC to a higher concentration.

IMPROVING NONTHROMBOGENICITY OF CHITIN WITH ZWITTERIONIC STRUCTURE OF SULFOBETAINE

In order to improve the nonthrombogenicity of chitin,a new monomer,N,N-dimethyl(β-hydroxyethyloxyethyl) ammonium propanesulfonate(DHAPS)was designed,synthesized and grafted onto the chitin membrane by using hexamethylene diisocyanate(HDI)as a coupling agent.Surface analysis of the grafted membranes by ATR-FTIR and XPS confirms that DHAPS has been successfully grafted onto the membrane surface.The platelet resistant property of the grafted membranes was evaluated by a platelet-rich plasma adhesion method.The results showed that platelet-adhesive resistance of the modified membrane has been greatly improved.

The Structure of Montmorillonites Modified with Zwitterionic Surfactants and Their Sorption Ability

In the past four decades, there is a growing use of surfactant modified clay complexes in wide range of applications. The mostly used surfactants to modify the swelling clay minerals are cationic surfactants, such as quaternary ammonium, which consists of two distinct moieties, a hydrophilic head, where the positive charge is concentrated, and a hydrophobic hydrocarbon chain tail. During the surface modification, this kind of surfactant molecules attach on the inner and outer surface of clay minerals, the hydrophilic surface of raw clay minerals may changed into hydrophobic surface. The changes of organophilicity and hydrophobicity of clay minerals enable them used in more wide fields, such as adsorbents for organic contaminant, geotechnical barriers, filling of nanocomposite, etc.

Surface Modification of Silk Fibroin Films with Zwitterionic Phosphobetaine to Improve the Hemocompatibility

Zwitterionic phosphobetaine bearing a hydroxyl and a zwitterionic group,8-hydroxy-2-octyl phosphorylcholine（HOPC）,was synthesized and constructed to the surface of silk fibroin（SF） films in order to improve the hemocompatibility of fibroin films by a an isocyanate head group.The surface characteristics of the modified films were measured by attenuated total reflection Fourier transform infrared spectroscopy（ATR-FTIR） and electron spectroscopy for chemical analysis（ESCA）,displaying the successful immobilization of Zwitterionic phosphobetaine on the surface of these fibroin films.Moreover,the further platelet adhesion test in platelets rich plasma（PRP） of human beings showed the zwitterionic phosphobetaine led mainly to good nonthrombogenicity.The experimental results indicated a reasonable approach to improve the blood compatibility of fibroin films.

A NOVEL ZWITTERIONIC SILANE COUPLING AGENT FOR NONTHROMBOGENIC BIOMATERIALS

A novel silane coupling agent bearing sulfobetaine group, N,N-diethyl-N-（3-sulfopropyl）-aminopropyl- trimethoxysilane （DESATS）, was first designed, synthesized and characterized. Its solution property was studied by means of dynamic light scattering. DESATS was successfully bonded onto the surface of the glass and proved by ESCA. Platelet adhesion assay in vitro indicated that the nonthrombogenicity of glass slide modified with DESATS is greatly improved.

Synthesis, Crystal Structure and Luminescence of One Cd^Ⅱ Coordination Polymer with Bifunctional Zwitterionic Ligand

One coordination polymer with bifunctional zwitterionic ligand bearing both carboxylate and tetrazolate groups, [Cd（L1）（N3）]n·n H2O（1, L1 = 1-（carboxylatomethyl）-4-（5-tetrazolato）pyridinium], has been in situ hydrothermally synthesized and structurally characterized. Compound 1 crystallizes in monoclinic with C2/m space group, a = 21.8038（17）, b = 7.6087（6）, c = 7.8342（6） A, β = 106.166（2）o, V = 1248.29（17） A3, Z = 4, Mr = 376.62, Dc = 2.004 g·cm-3, F（000） = 736, μ = 1.772 mm-1, Rint = 0.0217, S = 1.088, the final R = 0.0415 and w R = 0.1128 for 1020 observed reflections with I 2σ（I）. The compound exhibits two-dimensional coordination sheets, in which infinite anionic [Cd（CN4）（N3）（OCO）]n chains with the tricomponent（μ-azide）（μ-tetrazolate）（μ-carboxylate） bridges are cross-linked by cationic 1-methylenepyridinium spacers of the L1 ligand. This compound in the solid state exhibits blue luminescence assignable to intraligand transitions.

Assembling Zwitterionic, Water-Soluble Porphyrin and Its Biological Studies

A kind of zwitterionic water-soluble porphyrin5-(N-trimethyl-4-aminiumphenyl)-10, 15, 20-tri (4-sulfon-atephenyl) porphyrin trisammonium salt, hasbeen synthe-sized. Its biological studies, interactions with DNA and bacteria cells, wereinvestigated. The damage to the cell wall of bacteria E. coli were observed firstly by AFM (AtomicForce Microscope).

Rapid fabrication of zwitterionic sulfobetaine vinylimidazole-based monoliths via photoinitiated copolymerization for hydrophilic interaction chromatography

Zwitterionic sulfobetaine-based monolithic stationary phases have attracted increasing attention for their use in hydrophilic interaction chromatography.In this study,a novel hydrophilic polymeric monolith was fabricated through photo-initiated copolymerization of 3-(3-vinyl-1-imidazolio)-1-propanesulfonate(SBVI)with pentaerythritol triacrylate using methanol and tetrahydrofuran as the porogenic system.Notably,the duration for the preparation of this novel monolith was as little as 5 min,which was significantly shorter than that required for previously reported sulfobetaine-based monoliths prepared via conventional thermally initiated copolymerization.Moreover,these monoliths showed good morphology,permeability,porosity(62.4%),mechanical strength(over 15 MPa),column efficiency(51,230 plates/m),and reproducibility(relative standard deviations for all analytes were lower than 4.6%).Mechanistic studies indicated that strong hydrophilic and negative electrostatic interactions might be responsible for the retention of polar analytes on the zwitterionic SBVI-based monolith.In particular,the resulting monolith exhibited good anti-protein adhesion ability and low nonspecific protein adsorption.These excellent features seem to favor its application in bioanalysis.Therefore,the novel zwitterionic sulfobetaine-based monolith was successfully employed for the highly selective separation of small bioactive compounds and the efficient enrichment of N-glycopeptides from complex samples.In this study,we prepared a novel zwitterionic sulfobetaine-based monolith with good performance and developed a simpler and faster method for preparation of zwitterionic monoliths.