The counterion-mediated hydrogen bonding(CMHB)is related to the hydrogen bonding between bound counterions and polyelectrolyte chains in polyelectrolyte systems,where the counterions can both electrostatically bind to...The counterion-mediated hydrogen bonding(CMHB)is related to the hydrogen bonding between bound counterions and polyelectrolyte chains in polyelectrolyte systems,where the counterions can both electrostatically bind to the charged groups of polyelectrolyte chains and act as hydrogen bond donors or acceptors to form hydrogen bonds with the hydrogen bond sites associated with polyelectrolyte chains simultaneously.A large number of literatures illustrate that strong polyelectrolytes(SPs)are insensitive to pH,which severely limmits the applications of SPs as smart materials.However,our studies have demonstrated that the CMHB makes SPs pH-responsive.This perspective discusses the mechanism of pH responsiveness of SPs and the pH-tunable properties of SPs,based on the pH-controlled CMHB effect.The future research directions on the pH responsiveness of SPs are also discussed here.It is anticipated that the study of the pH responsiveness of SPs not only will provide a new understanding of the fundamental properties of SPs,but also will greatly expand the applications of SPs in the field of smart materials.展开更多
The liquid-liquid phase separation of biopolymers in living cells contains multiple interactions and occurs in a dynamic environment.Resolving the regulation mechanism is still a challenge.In this work,we designed a s...The liquid-liquid phase separation of biopolymers in living cells contains multiple interactions and occurs in a dynamic environment.Resolving the regulation mechanism is still a challenge.In this work,we designed a series of peptides(XXLY)_(6)SSSGSS and studied their complexation and coacervation behavior with single-stranded oligonucleotides.The“X”and“Y”are varied to combine known amounts of charged and non-charged amino acids,together with the introduction of secondary structures and pH responsiveness.Results show that the electrostatic interaction,which is described as charge density,controls both the strength of complexation and the degree of chain relaxation,and thus determines the growth and size of the coacervates.The hydrophobic interaction is prominent when the charges are neutralized.Interestingly,the secondary structures of peptides exhibit profound effect on the morphology of the phases,such as solid phase to liquid phase transition.Our study gains insight into the phase separation under physiological conditions.It is also helpful to create coacervates with desirable structures and functions.展开更多
We investigate the solution self-assembly of a mixture of positively charged homopolymers and AB diblock copolymers,in which the A blocks are negatively charged,and the B blocks are neutral.The electrostatic complexat...We investigate the solution self-assembly of a mixture of positively charged homopolymers and AB diblock copolymers,in which the A blocks are negatively charged,and the B blocks are neutral.The electrostatic complexation between oppositely charged polymers drives the formation of many ordered phases.The microstructures and phase diagrams are calculated using self-consistent field theory(SCFT)based on an ion-pair model with an equilibrium constant K to characterize the strength of binding between positively and negatively charged monomers.The effects of the charge ratio,representing the ratio of charges from the homopolymer over all charges from polymers in the system,on the ordered structure are systematically studied,both for hydrophobic and hydrophilic A blocks.The charge ratio plays an important role in determining the phase boundaries in the phase diagram of salt concentration versus polymer concentration.We also provide information about the varying tendency of the domain spacing and core size of the spherical phase when the charge ratio is changed,and the results are in good agreement with experiments.These studies provide a deep understanding of the self-assembled microstructures of oppositely charged diblock copolymer-homopolymer systems.展开更多
Polyelectrolyte complexes(PECs)of hyperbranched(HB)and linear polysaccharides are promising as more effective encapsulation agents compared to PECs formed by linear polysaccharides.We investigated the PECs between the...Polyelectrolyte complexes(PECs)of hyperbranched(HB)and linear polysaccharides are promising as more effective encapsulation agents compared to PECs formed by linear polysaccharides.We investigated the PECs between the HB anionic polysaccharide fucoidan(FUC)and the cationic linear polysaccharide chitosan(CS).The FUC had a molecular weight(MW)of 30×106.The PECs were prepared in three solvents(water,0.01 and 0.1 mol/L acetic acid)with CS of MW of 15,110 and 170 kDa,and deacetylation degrees(DDA)of 70%and 97%.The structures of the PECs and the initial FUC were investigated by multi-angle static and dynamic light scattering.As the FUC contained 18 wt%of—OSO3 groups and 5 wt%of uronic acid units,it was a“strong-weak”copolyanion,so the HB macromolecules of the FUC formed nanogel particles in 0.1 mol/L AcOH and open branched structures in water,as confirmed by the Kratky plots.After mixing the solutions of original components,the PEC structures underwent an equilibration period,the duration of which increased with the MW of CS.As the charge stoichiometry was approached,the PECs shrank;the fractal dimension approached unity,indicating the side-by-side packing of adjacent FUC branches with the help of CS.Secondary aggregation in the vicinity of the charge compensation was hardly observed,as it occurred in a very narrow region.The PEC content at theζ-potential inversion depended on solvents’pH and the DDA of CS.In the extreme case of core-shell PECs in 0.1 mol/L AcOH,obtained by mixing FUC nanogels with the solutions of high MW CS of 97%DDA,the protruding tails of CS formed a positively charged shell in the whole range of FUC content(10 wt%<WFUC<90 wt%).Scanning electron microscopy and atomic force microscopy images of dried samples were discussed in relation to the light scattering results.展开更多
Cationic polyethylenimine （PEI） with dextran fluorescein anionic （DFA） or oligodeoxynucleotide （ODN） could form polyelectrolyte complex by self-assembly as a gene delivery vector. This study was designed to inve...Cationic polyethylenimine （PEI） with dextran fluorescein anionic （DFA） or oligodeoxynucleotide （ODN） could form polyelectrolyte complex by self-assembly as a gene delivery vector. This study was designed to investigate the effects on pharmaceutical characteristics and cell uptake PEI after a long-circulation modification with poly（ethylene glycol） （PEG）. DFA or ODN reacted with PEI or PEI-PEG to form polyelectrolyte complexes. Surface characters of these complexes and the retardation of ODN by PEI and PEI-PEG were evaluated. The uptake rates of DFA/PEI and DFA/PEI-PEG complexes by MCF-7 cells were evaluated by flow cytometry. Confocal laser scanning microscopy was utilized to visualize the internalization of these complexes. ODN/PEI complex showed the dependence of their size and ξ potential on the N/P ratio. ODN/PEI-PEG complex were much less affected by N/P ratio and their size was around 30 100 nm. PEI and PEI-PEG retarded ODN even at N/P ratio as low as 4, and complete retardation was found at N/P ratio of 8. The uptake rate by MCF-7 cells was direct correlated to the DFA concentration and incubation time, and the uptake rate could exceed 99% under the selected condition. The results in this study showed that PEI self-assembly polyelectrolyte complex after stealth or long circulation modification may increase the ability as a gene vector to delivery genes into cells.展开更多
The achievement of both robust fire-safety and mechanical properties is of vital requirement for carbon fiber(CF)composites.To this end,a facile interracial strategy for fabricating flame-retardant carbon fibers decor...The achievement of both robust fire-safety and mechanical properties is of vital requirement for carbon fiber(CF)composites.To this end,a facile interracial strategy for fabricating flame-retardant carbon fibers decorated by bio-based polyelectrolyte complexes(PEC)consisting of chitosan(CH)and ammonium polyphosphate(APP)was developed,and its corresponding fire-retarded epoxy resin composites(EP/(PEC@CF))without any other additional flame retardants were prepared.The decorated CFs were characterized by SEM-EDX,XPS and XRD,indicating that the flame-retardant PEC coating was successfully constructed on the surface of CF.Thanks to the nitrogen-and phosphorous-containing PEC,the resulting composites exhibited excellent flame retardancy as the limiting oxygen index(LOI)increased from 31.0%of EP/CF to 40.5%and UL-94 V-0 rating was achieved with only 8.1 wt%PEC.EP/(PEC8.1@CF)also performed well in cone calorimetry with the decrease of peak-heat release rate(PHRR)and smoke production rate(SPR)by 50.0%and 30.4%,respectively,and the value of fire growth rate(FIGRA)was also reduced to 3.41 kW·m-2-s-1 from 4.84 kW·m-2·s-1,suggesting a considerably enhanced fire safety.Furthermore,SEM images of the burning residues revealed that the PEC coating exhibited the dominant flame-retardant activity in condensed phase via the formation of compact phosphorus-rich char.In addition,the impact strength of the composite was improved,together with no obvious deterioration of flexural properties and glass transition temperature.Taking advantage of the features,the PEC-decorated carbon fibers and the relevant composites fabricated by the cost-effective and facile strategy would bring more chances for widespread applications.展开更多
In general,productions of natural pigment in submerged microorganism culture were much less than that in solid-state fermentation,because the solid-state culture can provide a support carrier for the mycelium. To impr...In general,productions of natural pigment in submerged microorganism culture were much less than that in solid-state fermentation,because the solid-state culture can provide a support carrier for the mycelium. To improve natural pigment production,the cultivation of Monascus purpureus in submerged encapsulated cell was investigated. Monascus purpureus immobilized in polyelectrolyte complex(PEC) microcapsules,which were pre-pared by sodium cellulose sulphate(NaCS) and poly-dimethyl-diallyl-ammonium chloride(PDMDAAC),was a good substitute for submerged cell culture because it mimicked the solid-state environment. The repeated-batch process with encapsulated cells was studied in flasks and a bubble column. The results indicated that the bubble column was more suitable for the encapsulation culture than the shaking flasks because of its good mass transfer performance and minor shear stress on cells. Owing to the protection of the microcapsule's membrane,Monascus purpureus in microcapsules increased approximately three times over that in free cell culture with negligible cell leakage to the medium. The pigment production in the bubble column finally reached 3.82(OD500) ,which was two times higher than in free cell culture. In addition,the duration of each batch was shortened to 15% of that in free cell culture.展开更多
The objective of this study is to design sustained-release tablets using matrix technology, which can well control the release of highly water-soluble drugs with good system robustness and simple preparation process. ...The objective of this study is to design sustained-release tablets using matrix technology, which can well control the release of highly water-soluble drugs with good system robustness and simple preparation process. Taking venlafaxine hydrochloride(VH) as a drug model, the feasibility of using chitosan(CS), carbomer(CBM) combination system to achieve this goal was studied. Formulation and process variables influencing drug release from CS–CBM matrix tablets were investigated. It was found that CS–CBM combination system weakened the potential influence of CS, CBM material properties and gastric emptying time on drug release profile. Demonstrated by direct observation, differential scanning calorimetry(DSC) and Fourier transform infrared spectroscopy(FTIR), in situ self-assembled polyelectrolyte complex(PEC) film was formed on the tablet surface during gastrointestinal tract transition, which contributed to the tunable and robust control of drug release. The sustained drug release behavior was further demonstrated in vivo in Beagle dogs, with level A in vitro and in vivo correlation(IVIVC) established successfully. In conclusion, CS–CBM matrix tablets are promising system to tune and control the release of highly water-soluble drugs with good system robustness.展开更多
Polyelectrolyte-surfactant complexes（PESCs） were fabricated through the interaction of poly（acrylic acid） and four different cationic surfactants or their mixtures. PESC membranes were prepared by solution casting...Polyelectrolyte-surfactant complexes（PESCs） were fabricated through the interaction of poly（acrylic acid） and four different cationic surfactants or their mixtures. PESC membranes were prepared by solution casting method and were applied in ethanol recovery from aqueous solution via pervaporation. Elemental analysis（EA）, Fourier transform infrared spectroscopy（FTIR）, water contact angle（CA） measurement, differential scanning calorimetry（DSC） and X-ray scattering were employed to characterize the composition, structure and properties of PESCs. The results reveal that the investigated PESCs are similar in hydrophobicity but different in hierarchical nanostructures. In separating 5 wt% ethanol/water mixture, PESC membranes with high crystallinity will have both low flux and ethanol selectivity because of the high packing density and low permeability of crystalline regions. Meanwhile, the hierarchical nanostructures of PESC membranes change under pervaporation environment as was revealed by in situ synchrotron radiation X-ray scattering measurement. That is, the crystalline region could melt at high temperature in swelling state, thus consequently enhancing the ethanol selectivity.展开更多
Three dendronized polymers from generation one to generation three have been prepared by complexing negatively charged Frechet-type dendrons with a polyanion, poly（diallydimethylammoniurn chloride） （PDADMAC）. The ...Three dendronized polymers from generation one to generation three have been prepared by complexing negatively charged Frechet-type dendrons with a polyanion, poly（diallydimethylammoniurn chloride） （PDADMAC）. The gaffing degree has been confirmed mainly by elemental analysis. In dilute solutions of tetrahydrofuran, static light scattering studies indicate that the first generation complex has a coil-like conformation, even more flexible than PDADMAC. The second and third generation complexes exhibit polyelectrolyte behavior. Dynamic light scattering experiments indicate that all the three complexes have almost the same hydrodynamic radius, indicating that they might own similar coil conformation. Atomic force microscopy shows the existence of disordered globules formed by one or a couple of complex coils. All these observations can be explained by the flowerlike coil conformation, which is formed by the intra-molecular association. This is totally different from the stretched chain conformation formed by covalently connected dendronized polymers. This result also explains why some ordered supramolecular structures, found in condensed state of the similar complexes, are not as perfect as those of conventional dendronized polymers.展开更多
The polyelectrolyte complex formed from the polyanion and polycation was studied by turbidimetry, static and electrophoretic light scattering, and elementary analysis. Sodium salts of polyacrylate （PA） and heparin ...The polyelectrolyte complex formed from the polyanion and polycation was studied by turbidimetry, static and electrophoretic light scattering, and elementary analysis. Sodium salts of polyacrylate （PA） and heparin （Hep） were chosen as the polyanion, and hydrochloric salts of poly（vinyl amine） （PVA） and chitosan （Chts） as the polycation. Although these vinyl polymers and polysaccharides have remarkably different backbone chemical structures and linear charge densities, all the four combinations PA-PVA, PA-Chts, Hep-PVA, and Hep-Chts provide almost stoichiometric polyelectrolyte complexes which are slightly charged owing to the adsorption of the excess polyelectrolyte component onto the neutral complex. The charges stabilize the complex colloids in aqueous solution of a non-stoichiometric mixture, and the aggregation number of the complex colloids increases with approaching to the stoichiometric mixing ratio. The mixing ratio dependence of the aggregation number for the four complexes is explained by the model proposed in the previous study.展开更多
The flocculating properties of polymer-colloid complexes (PCCs) formed via noncovalent interactions of positively charged aluminoxane particles (APs) with macromolecules of weakly charged cationic acrylamide copolymer...The flocculating properties of polymer-colloid complexes (PCCs) formed via noncovalent interactions of positively charged aluminoxane particles (APs) with macromolecules of weakly charged cationic acrylamide copolymers from the Praestol and Organopol series have been studied. The PCCs that spontaneously formed during mixing of sols of a high-basicity aluminum polyhydroxochloride (APHC) with aqueous solutions of the copolymers exhibit high flocculating ability under the conditions of gravity sedimentation of the model kaolin dispersion with Сd = 8 g/dm3, and their efficiency exceeds both that of the copolymers and the earlier obtained PCCs with nonionogenic polyacrylamide (PAA). In contrast to weakly charged polycationites, the fully charged KF-99 polyelectrolyte does not form PCCs and the products of its mixing with APHC do not reveal an increased flocculating effect.展开更多
We produced low-molecular-weight heparin/protamine micro (nano) particles (LMW-H/P MPs·NPs) as a carrier for heparin-binding growth factors (GFs), such as fibroblast growth factor (FGF)-2 and various GFs in plate...We produced low-molecular-weight heparin/protamine micro (nano) particles (LMW-H/P MPs·NPs) as a carrier for heparin-binding growth factors (GFs), such as fibroblast growth factor (FGF)-2 and various GFs in platelet-rich plasma (PRP). A mixture of LMW-H (MW: approximately 5000 Da, 6.4 mg/ml) and protamine (MW: approximately 3000 Da, 10 mg/ml) at a ratio of 7:3 (vol:vol) yields a dispersion of micro (nano) particles (200 nm - 3 μm in diameter). The diluted LMW-H solution in saline (0.32 mg/ml) mixed with diluted protamine (0.5 mg/ml) at a ratio at 7:3 (vol:vol) resulted in soluble nanoparticles (approximately 100 nm in diameter). The generated NPs could be then stabilized by adding 2 mg/ml dextran (MW: 178-217 kDa) and remained soluble after lyophilization of dialyzed LMW-H /P NPs solution. The LMW-H/P MPs·NPs adsorb GFs, control their release, protect GFs and activate their biological activities. Furthermore, administration of GFs-containing F/P MPs·NPs exhibited significantly higher inductions of vascularization and fibrous tissue formation in vivo than GFs alone. LMW-H/P MPs·NPs can also efficiently bind to tissue culture plates and retain the binding of GFs. The LMW-H/P MPs·NP-coated matrix with various GFs or cytokines provided novel biomaterials that could control cellular activity such as proliferation and differentiation. Thus, LMW-H/P MPs·NPs are an excellent carrier for GFs and are a functional coating matrix for various kinds of cell cultures.展开更多
Chitosan,a renewable,non-toxic,and natural cationic polyelectrolyte,can be combined with many anionic polyelectrolytes(such as sodium alginate,hyaluronic acid,xylan,and gelatin)via electrostatic forces to form chitosa...Chitosan,a renewable,non-toxic,and natural cationic polyelectrolyte,can be combined with many anionic polyelectrolytes(such as sodium alginate,hyaluronic acid,xylan,and gelatin)via electrostatic forces to form chitosan-based polyelectrolyte composites under certain conditions.This review summarizes various methods of preparing chitosan-based polyelectrolyte composites and analyzes their applications in clinical medicine and agriculture,as well as pharmaceutical,tissue,food,environmental,and textile engineering fields.The future development direction and potential of chitosan-based polyelectrolytes are also discussed.展开更多
Redox-active polyelectrolyte-surfactant complexes（PSC） were prepared via the ionic self-assembly of sodium poly（styrenesulfonate） （PSS） and ferrocenyl surfactant,（11-ferrocenylundecyl）trimethylammonium bromide...Redox-active polyelectrolyte-surfactant complexes（PSC） were prepared via the ionic self-assembly of sodium poly（styrenesulfonate） （PSS） and ferrocenyl surfactant,（11-ferrocenylundecyl）trimethylammonium bromide（FTMA） in aqueous solution. The PSS-FTMA complex exhibited an ordered interdigitated monolayer mesomorphous structure with the long period of d = 3.13 nm,and was in the ionic thermotropic liquid crystal SmA state at room temperature.Interestingly,in the solid complex, the ferrocenyl moieties formed H-aggregation showing an increase in theπ-π~＊ energy transfer of cyclopentadienes in the ferrocene moieties as known from the blue-shift in the UV spectrum.The complexes showed higher thermal stability compared with their components due to the ionic interaction.The PSS-FTMA film had a good redox reversibility,which promised to be used in electrochemical sensors.展开更多
Poly(arylene ether ketone)s with carboxylic groups(PAEK-COOH)is a good membrane fabrication material,a kind of polyacids,while polyethylenimine(PEI)is a weak organic base,a kind of polybases.Those polyacids and polyba...Poly(arylene ether ketone)s with carboxylic groups(PAEK-COOH)is a good membrane fabrication material,a kind of polyacids,while polyethylenimine(PEI)is a weak organic base,a kind of polybases.Those polyacids and polybases would form ionic complexation at the interface of two liquid phases.In this paper,PAEK-COOH/N-methyl pyrrolidone(NMP)/1,4-dioxane(DO)mixture,employed as polymer casting solution and aqueous solution of PEI,used as coagulation bath,respectively.Then ion complexation induced phase inversion process is applied to prepare positively charged nanofiltration membrane with thinner but denser separation skin layer.The complexing reaction at the interface of two liquid phases has great influence on the kinetic aspects of phase inversion process,which in accordance would affect the morphology and performance of the membrane.The obtained membrane,fabricated via the ion complexation induced phase inversion method,is positively charged,has high water permeability,and possesses high rejection towards divalent cations,such as Mg^(2+),Ca^(2+),Pb^(2+)etc.,which could be used for removal of heavy metals from polluted water.At the optimal condition,the pure water flux of the PAEK-COOH-PEI nanofiltration membrane is 24.3 L·m^(-2)·h^(-1),with MgCl_2rejection of 92.2%.展开更多
基金supported by the National Natural Science Foundation of China(Nos.22273098,52033001,22373003 and 22103002)the Fundamental Research Funds for the Central Universities(No.WK2480000007).
文摘The counterion-mediated hydrogen bonding(CMHB)is related to the hydrogen bonding between bound counterions and polyelectrolyte chains in polyelectrolyte systems,where the counterions can both electrostatically bind to the charged groups of polyelectrolyte chains and act as hydrogen bond donors or acceptors to form hydrogen bonds with the hydrogen bond sites associated with polyelectrolyte chains simultaneously.A large number of literatures illustrate that strong polyelectrolytes(SPs)are insensitive to pH,which severely limmits the applications of SPs as smart materials.However,our studies have demonstrated that the CMHB makes SPs pH-responsive.This perspective discusses the mechanism of pH responsiveness of SPs and the pH-tunable properties of SPs,based on the pH-controlled CMHB effect.The future research directions on the pH responsiveness of SPs are also discussed here.It is anticipated that the study of the pH responsiveness of SPs not only will provide a new understanding of the fundamental properties of SPs,but also will greatly expand the applications of SPs in the field of smart materials.
基金supported by the National Natural Science Foundation of China(No.21973002).
文摘The liquid-liquid phase separation of biopolymers in living cells contains multiple interactions and occurs in a dynamic environment.Resolving the regulation mechanism is still a challenge.In this work,we designed a series of peptides(XXLY)_(6)SSSGSS and studied their complexation and coacervation behavior with single-stranded oligonucleotides.The“X”and“Y”are varied to combine known amounts of charged and non-charged amino acids,together with the introduction of secondary structures and pH responsiveness.Results show that the electrostatic interaction,which is described as charge density,controls both the strength of complexation and the degree of chain relaxation,and thus determines the growth and size of the coacervates.The hydrophobic interaction is prominent when the charges are neutralized.Interestingly,the secondary structures of peptides exhibit profound effect on the morphology of the phases,such as solid phase to liquid phase transition.Our study gains insight into the phase separation under physiological conditions.It is also helpful to create coacervates with desirable structures and functions.
基金supported by the National Natural Science Foundation of China(NSFC)(Nos.22073002,51921002 and 22373008).
文摘We investigate the solution self-assembly of a mixture of positively charged homopolymers and AB diblock copolymers,in which the A blocks are negatively charged,and the B blocks are neutral.The electrostatic complexation between oppositely charged polymers drives the formation of many ordered phases.The microstructures and phase diagrams are calculated using self-consistent field theory(SCFT)based on an ion-pair model with an equilibrium constant K to characterize the strength of binding between positively and negatively charged monomers.The effects of the charge ratio,representing the ratio of charges from the homopolymer over all charges from polymers in the system,on the ordered structure are systematically studied,both for hydrophobic and hydrophilic A blocks.The charge ratio plays an important role in determining the phase boundaries in the phase diagram of salt concentration versus polymer concentration.We also provide information about the varying tendency of the domain spacing and core size of the spherical phase when the charge ratio is changed,and the results are in good agreement with experiments.These studies provide a deep understanding of the self-assembled microstructures of oppositely charged diblock copolymer-homopolymer systems.
基金jointly funded by the Russian Science Foundationthe St.-Petersburg Science Foundation(No.23-23-10005)
文摘Polyelectrolyte complexes(PECs)of hyperbranched(HB)and linear polysaccharides are promising as more effective encapsulation agents compared to PECs formed by linear polysaccharides.We investigated the PECs between the HB anionic polysaccharide fucoidan(FUC)and the cationic linear polysaccharide chitosan(CS).The FUC had a molecular weight(MW)of 30×106.The PECs were prepared in three solvents(water,0.01 and 0.1 mol/L acetic acid)with CS of MW of 15,110 and 170 kDa,and deacetylation degrees(DDA)of 70%and 97%.The structures of the PECs and the initial FUC were investigated by multi-angle static and dynamic light scattering.As the FUC contained 18 wt%of—OSO3 groups and 5 wt%of uronic acid units,it was a“strong-weak”copolyanion,so the HB macromolecules of the FUC formed nanogel particles in 0.1 mol/L AcOH and open branched structures in water,as confirmed by the Kratky plots.After mixing the solutions of original components,the PEC structures underwent an equilibration period,the duration of which increased with the MW of CS.As the charge stoichiometry was approached,the PECs shrank;the fractal dimension approached unity,indicating the side-by-side packing of adjacent FUC branches with the help of CS.Secondary aggregation in the vicinity of the charge compensation was hardly observed,as it occurred in a very narrow region.The PEC content at theζ-potential inversion depended on solvents’pH and the DDA of CS.In the extreme case of core-shell PECs in 0.1 mol/L AcOH,obtained by mixing FUC nanogels with the solutions of high MW CS of 97%DDA,the protruding tails of CS formed a positively charged shell in the whole range of FUC content(10 wt%<WFUC<90 wt%).Scanning electron microscopy and atomic force microscopy images of dried samples were discussed in relation to the light scattering results.
基金National Nature Science Foundation of China (Grant No.30772665)Beijing Nature Science Foundation (Grant No.7083111).
文摘Cationic polyethylenimine （PEI） with dextran fluorescein anionic （DFA） or oligodeoxynucleotide （ODN） could form polyelectrolyte complex by self-assembly as a gene delivery vector. This study was designed to investigate the effects on pharmaceutical characteristics and cell uptake PEI after a long-circulation modification with poly（ethylene glycol） （PEG）. DFA or ODN reacted with PEI or PEI-PEG to form polyelectrolyte complexes. Surface characters of these complexes and the retardation of ODN by PEI and PEI-PEG were evaluated. The uptake rates of DFA/PEI and DFA/PEI-PEG complexes by MCF-7 cells were evaluated by flow cytometry. Confocal laser scanning microscopy was utilized to visualize the internalization of these complexes. ODN/PEI complex showed the dependence of their size and ξ potential on the N/P ratio. ODN/PEI-PEG complex were much less affected by N/P ratio and their size was around 30 100 nm. PEI and PEI-PEG retarded ODN even at N/P ratio as low as 4, and complete retardation was found at N/P ratio of 8. The uptake rate by MCF-7 cells was direct correlated to the DFA concentration and incubation time, and the uptake rate could exceed 99% under the selected condition. The results in this study showed that PEI self-assembly polyelectrolyte complex after stealth or long circulation modification may increase the ability as a gene vector to delivery genes into cells.
基金Financial supports by the National Natural Science Foundation of China(Nos.51773137 and 51721091)the Sichuan Province Youth Science and Technology Innovation Team(No.2017TD0006)
文摘The achievement of both robust fire-safety and mechanical properties is of vital requirement for carbon fiber(CF)composites.To this end,a facile interracial strategy for fabricating flame-retardant carbon fibers decorated by bio-based polyelectrolyte complexes(PEC)consisting of chitosan(CH)and ammonium polyphosphate(APP)was developed,and its corresponding fire-retarded epoxy resin composites(EP/(PEC@CF))without any other additional flame retardants were prepared.The decorated CFs were characterized by SEM-EDX,XPS and XRD,indicating that the flame-retardant PEC coating was successfully constructed on the surface of CF.Thanks to the nitrogen-and phosphorous-containing PEC,the resulting composites exhibited excellent flame retardancy as the limiting oxygen index(LOI)increased from 31.0%of EP/CF to 40.5%and UL-94 V-0 rating was achieved with only 8.1 wt%PEC.EP/(PEC8.1@CF)also performed well in cone calorimetry with the decrease of peak-heat release rate(PHRR)and smoke production rate(SPR)by 50.0%and 30.4%,respectively,and the value of fire growth rate(FIGRA)was also reduced to 3.41 kW·m-2-s-1 from 4.84 kW·m-2·s-1,suggesting a considerably enhanced fire safety.Furthermore,SEM images of the burning residues revealed that the PEC coating exhibited the dominant flame-retardant activity in condensed phase via the formation of compact phosphorus-rich char.In addition,the impact strength of the composite was improved,together with no obvious deterioration of flexural properties and glass transition temperature.Taking advantage of the features,the PEC-decorated carbon fibers and the relevant composites fabricated by the cost-effective and facile strategy would bring more chances for widespread applications.
基金Supported by the National Basic Research Program of China（2007CB707805） the National Natural Science Foundation of China（20876139）
文摘In general,productions of natural pigment in submerged microorganism culture were much less than that in solid-state fermentation,because the solid-state culture can provide a support carrier for the mycelium. To improve natural pigment production,the cultivation of Monascus purpureus in submerged encapsulated cell was investigated. Monascus purpureus immobilized in polyelectrolyte complex(PEC) microcapsules,which were pre-pared by sodium cellulose sulphate(NaCS) and poly-dimethyl-diallyl-ammonium chloride(PDMDAAC),was a good substitute for submerged cell culture because it mimicked the solid-state environment. The repeated-batch process with encapsulated cells was studied in flasks and a bubble column. The results indicated that the bubble column was more suitable for the encapsulation culture than the shaking flasks because of its good mass transfer performance and minor shear stress on cells. Owing to the protection of the microcapsule's membrane,Monascus purpureus in microcapsules increased approximately three times over that in free cell culture with negligible cell leakage to the medium. The pigment production in the bubble column finally reached 3.82(OD500) ,which was two times higher than in free cell culture. In addition,the duration of each batch was shortened to 15% of that in free cell culture.
基金supported by the Distinguished Professor Project of Liaoning Province(2015)
文摘The objective of this study is to design sustained-release tablets using matrix technology, which can well control the release of highly water-soluble drugs with good system robustness and simple preparation process. Taking venlafaxine hydrochloride(VH) as a drug model, the feasibility of using chitosan(CS), carbomer(CBM) combination system to achieve this goal was studied. Formulation and process variables influencing drug release from CS–CBM matrix tablets were investigated. It was found that CS–CBM combination system weakened the potential influence of CS, CBM material properties and gastric emptying time on drug release profile. Demonstrated by direct observation, differential scanning calorimetry(DSC) and Fourier transform infrared spectroscopy(FTIR), in situ self-assembled polyelectrolyte complex(PEC) film was formed on the tablet surface during gastrointestinal tract transition, which contributed to the tunable and robust control of drug release. The sustained drug release behavior was further demonstrated in vivo in Beagle dogs, with level A in vitro and in vivo correlation(IVIVC) established successfully. In conclusion, CS–CBM matrix tablets are promising system to tune and control the release of highly water-soluble drugs with good system robustness.
基金financially supported by the National Natural Science Foundation of China(Nos.21376206 and 21676233)Zhejiang Province Natural Science Foundation(No.LR15B060001)
文摘Polyelectrolyte-surfactant complexes（PESCs） were fabricated through the interaction of poly（acrylic acid） and four different cationic surfactants or their mixtures. PESC membranes were prepared by solution casting method and were applied in ethanol recovery from aqueous solution via pervaporation. Elemental analysis（EA）, Fourier transform infrared spectroscopy（FTIR）, water contact angle（CA） measurement, differential scanning calorimetry（DSC） and X-ray scattering were employed to characterize the composition, structure and properties of PESCs. The results reveal that the investigated PESCs are similar in hydrophobicity but different in hierarchical nanostructures. In separating 5 wt% ethanol/water mixture, PESC membranes with high crystallinity will have both low flux and ethanol selectivity because of the high packing density and low permeability of crystalline regions. Meanwhile, the hierarchical nanostructures of PESC membranes change under pervaporation environment as was revealed by in situ synchrotron radiation X-ray scattering measurement. That is, the crystalline region could melt at high temperature in swelling state, thus consequently enhancing the ethanol selectivity.
基金supported by the National Natural Science Foundation of China(No.20734001)
文摘Three dendronized polymers from generation one to generation three have been prepared by complexing negatively charged Frechet-type dendrons with a polyanion, poly（diallydimethylammoniurn chloride） （PDADMAC）. The gaffing degree has been confirmed mainly by elemental analysis. In dilute solutions of tetrahydrofuran, static light scattering studies indicate that the first generation complex has a coil-like conformation, even more flexible than PDADMAC. The second and third generation complexes exhibit polyelectrolyte behavior. Dynamic light scattering experiments indicate that all the three complexes have almost the same hydrodynamic radius, indicating that they might own similar coil conformation. Atomic force microscopy shows the existence of disordered globules formed by one or a couple of complex coils. All these observations can be explained by the flowerlike coil conformation, which is formed by the intra-molecular association. This is totally different from the stretched chain conformation formed by covalently connected dendronized polymers. This result also explains why some ordered supramolecular structures, found in condensed state of the similar complexes, are not as perfect as those of conventional dendronized polymers.
基金supported by the a Grant-in-Aid for Scientific Research (No. 23350055) from the Japan Society for the Promotion of Science
文摘The polyelectrolyte complex formed from the polyanion and polycation was studied by turbidimetry, static and electrophoretic light scattering, and elementary analysis. Sodium salts of polyacrylate （PA） and heparin （Hep） were chosen as the polyanion, and hydrochloric salts of poly（vinyl amine） （PVA） and chitosan （Chts） as the polycation. Although these vinyl polymers and polysaccharides have remarkably different backbone chemical structures and linear charge densities, all the four combinations PA-PVA, PA-Chts, Hep-PVA, and Hep-Chts provide almost stoichiometric polyelectrolyte complexes which are slightly charged owing to the adsorption of the excess polyelectrolyte component onto the neutral complex. The charges stabilize the complex colloids in aqueous solution of a non-stoichiometric mixture, and the aggregation number of the complex colloids increases with approaching to the stoichiometric mixing ratio. The mixing ratio dependence of the aggregation number for the four complexes is explained by the model proposed in the previous study.
文摘The flocculating properties of polymer-colloid complexes (PCCs) formed via noncovalent interactions of positively charged aluminoxane particles (APs) with macromolecules of weakly charged cationic acrylamide copolymers from the Praestol and Organopol series have been studied. The PCCs that spontaneously formed during mixing of sols of a high-basicity aluminum polyhydroxochloride (APHC) with aqueous solutions of the copolymers exhibit high flocculating ability under the conditions of gravity sedimentation of the model kaolin dispersion with Сd = 8 g/dm3, and their efficiency exceeds both that of the copolymers and the earlier obtained PCCs with nonionogenic polyacrylamide (PAA). In contrast to weakly charged polycationites, the fully charged KF-99 polyelectrolyte does not form PCCs and the products of its mixing with APHC do not reveal an increased flocculating effect.
文摘We produced low-molecular-weight heparin/protamine micro (nano) particles (LMW-H/P MPs·NPs) as a carrier for heparin-binding growth factors (GFs), such as fibroblast growth factor (FGF)-2 and various GFs in platelet-rich plasma (PRP). A mixture of LMW-H (MW: approximately 5000 Da, 6.4 mg/ml) and protamine (MW: approximately 3000 Da, 10 mg/ml) at a ratio of 7:3 (vol:vol) yields a dispersion of micro (nano) particles (200 nm - 3 μm in diameter). The diluted LMW-H solution in saline (0.32 mg/ml) mixed with diluted protamine (0.5 mg/ml) at a ratio at 7:3 (vol:vol) resulted in soluble nanoparticles (approximately 100 nm in diameter). The generated NPs could be then stabilized by adding 2 mg/ml dextran (MW: 178-217 kDa) and remained soluble after lyophilization of dialyzed LMW-H /P NPs solution. The LMW-H/P MPs·NPs adsorb GFs, control their release, protect GFs and activate their biological activities. Furthermore, administration of GFs-containing F/P MPs·NPs exhibited significantly higher inductions of vascularization and fibrous tissue formation in vivo than GFs alone. LMW-H/P MPs·NPs can also efficiently bind to tissue culture plates and retain the binding of GFs. The LMW-H/P MPs·NP-coated matrix with various GFs or cytokines provided novel biomaterials that could control cellular activity such as proliferation and differentiation. Thus, LMW-H/P MPs·NPs are an excellent carrier for GFs and are a functional coating matrix for various kinds of cell cultures.
文摘Chitosan,a renewable,non-toxic,and natural cationic polyelectrolyte,can be combined with many anionic polyelectrolytes(such as sodium alginate,hyaluronic acid,xylan,and gelatin)via electrostatic forces to form chitosan-based polyelectrolyte composites under certain conditions.This review summarizes various methods of preparing chitosan-based polyelectrolyte composites and analyzes their applications in clinical medicine and agriculture,as well as pharmaceutical,tissue,food,environmental,and textile engineering fields.The future development direction and potential of chitosan-based polyelectrolytes are also discussed.
基金The financial support from the NSFC(No50873037)China Postdoctoral Science Foundation(Nos20100470908 and 201104349)the NSF of Guangdong Province(No10451064101005118)
文摘Redox-active polyelectrolyte-surfactant complexes（PSC） were prepared via the ionic self-assembly of sodium poly（styrenesulfonate） （PSS） and ferrocenyl surfactant,（11-ferrocenylundecyl）trimethylammonium bromide（FTMA） in aqueous solution. The PSS-FTMA complex exhibited an ordered interdigitated monolayer mesomorphous structure with the long period of d = 3.13 nm,and was in the ionic thermotropic liquid crystal SmA state at room temperature.Interestingly,in the solid complex, the ferrocenyl moieties formed H-aggregation showing an increase in theπ-π~＊ energy transfer of cyclopentadienes in the ferrocene moieties as known from the blue-shift in the UV spectrum.The complexes showed higher thermal stability compared with their components due to the ionic interaction.The PSS-FTMA film had a good redox reversibility,which promised to be used in electrochemical sensors.
基金Supported by the National Basic Research Program of China(2015CB655302)the National Science Foundation of China(51133008,51473163 and 51503199)the Development of Scientific and Technological Project of the Jilin Province(20160101316JC)
文摘Poly(arylene ether ketone)s with carboxylic groups(PAEK-COOH)is a good membrane fabrication material,a kind of polyacids,while polyethylenimine(PEI)is a weak organic base,a kind of polybases.Those polyacids and polybases would form ionic complexation at the interface of two liquid phases.In this paper,PAEK-COOH/N-methyl pyrrolidone(NMP)/1,4-dioxane(DO)mixture,employed as polymer casting solution and aqueous solution of PEI,used as coagulation bath,respectively.Then ion complexation induced phase inversion process is applied to prepare positively charged nanofiltration membrane with thinner but denser separation skin layer.The complexing reaction at the interface of two liquid phases has great influence on the kinetic aspects of phase inversion process,which in accordance would affect the morphology and performance of the membrane.The obtained membrane,fabricated via the ion complexation induced phase inversion method,is positively charged,has high water permeability,and possesses high rejection towards divalent cations,such as Mg^(2+),Ca^(2+),Pb^(2+)etc.,which could be used for removal of heavy metals from polluted water.At the optimal condition,the pure water flux of the PAEK-COOH-PEI nanofiltration membrane is 24.3 L·m^(-2)·h^(-1),with MgCl_2rejection of 92.2%.
