Ferrocenyl amphiphilic Janus dendrimers as redox‐responsive micellar carriers

Amphiphilic Janus dendrimers have attracted increasing attention due to their asymmetric structures and various functional properties compared to the conventional symmetric macromolecules. Herein, a novel ferrocenyl‐terminated amphiphilic Janus dendrimer containing nine hydrophilic triethylene glycol branches was synthesized by two synthetic routes, namely the typical chemo selective coupling method and the mixed modular approach. Chemical redox triggers, namely Fe₂(SO₄)₃ as oxidant and ascorbic acid as reductant, could regulate the self‐assembly behavior of the Janus dendrimer in water through the redox‐switching between ferrocene and ferricinium cations, and the change of micelles formed were investigated and confirmed through scanning electron microscopy and dynamic light scattering. The cargo‐loading property of the micelles self‐assembled by the Janus dendrimer was further proved by the successful fabrication of Rhodamine B (RhB)‐loaded micelles, and the oxidation‐triggered release behavior of the encapsulated RhB could be mediated by changing the concentration of oxidants. This work provides an effective approach to prepare ferrocenyl‐terminated amphiphilic Janus dendrimers and the self‐assembled micelles might be used as a promising molecular carrier in areas such as drug delivery and catalysis.     

Influence of pH on the Motion of Catalytic Janus Particles and Tubular Bubble‐Propelled Micromotors

Self‐propelled miniaturized machines harness the chemical potential of their environment for movement. Locomotion of chemically powered micromotors have been hugely dependent on the surroundings. The use of pH to alter the mobility of micromotors is demonstrated in this work through the manipulation of hydrogen peroxide chemistry in different acidity/alkalinity. The sequential addition of sodium hydroxide to increase the pH of the solution led to a consequent increase in activity of micromotors. Meanwhile, addition of hydrochloric acid compromised the structural integrity of the microstructures, culminating in locomotive changes. Such dramatic changes in activity and velocities of the micromotors allow the usage of this behavior for pH detection. This concept was illustrated with Janus silver micromotors and tubular bimetallic Cu/Pt micromotors. Alteration of pH serves as a useful general strategy for increasing hydrogen peroxide decomposition for enhanced oxygen‐bubble propulsion in catalytic micromotors.     

基于自组装溶胶凝胶法无机Janus纳米片的制备及其乳化性能研究

论文首先采用水解苯乙烯-马来酸酐共聚物为乳化剂,正硅酸乙酯、亲油性硅烷偶联剂和亲水性硅烷偶联剂三种前驱体溶于石蜡做为油相(分散相),水为连续相,乳化分散后通过溶胶凝胶法,制备得到了表面亲水/内部亲油的核壳实心微球;然后超声清洗除去石蜡后得到了表面亲水/内部亲油的二氧化硅空心球,将其破碎后即得到了无机Janus纳米片.实...     

A pH‐responsive self‐fluorescent polymeric micelle as a potential optical imaging probe

A series of methoxypolyethylene glycol‐terminated self‐fluorescent polyurethane multi‐block copolymers with excellent pH‐responsivity, self‐fluorescence, and biocompatibility are designed and synthesized. In our design, 1, 4‐bis (hydroxyethyl) piperazine is chosen as a pH‐responsive segment which can donate or accept protons in response to the change of environmental pH, and fluorescein isothiocyanate is used as a fluorescent dye conjugated into the micelles to offer self‐fluorescence. The chemical structure of the polyurethane multi‐block copolymers is characterized by nuclear magnetic resonance and Fourier transform infrared spectroscopy. The results of the acid‐based titration, the fluorescence spectrometry, and the ultraviolet visible spectroscopy indicate that the polyurethane multi‐block copolymers own an excellent pH‐buffering capacity responded to the change of pH values and the favorable self‐fluorescence property in an aqueous solution. And the ultraviolet absorption peaks of samples are strengthened with increasing of pH values, indicating that methoxypolyethylene glycol‐terminated self‐fluorescent polyurethane multi‐block copolymer can be a pH‐dependent fluorescent probe in a broad pH range. In addition, the in vitro cytotoxicity test showed that the polyurethane multi‐block copolymer has low cytotoxicity and good biocompatibility, which make it a promising nanoplatform for molecular imaging, diagnosis, and treatment of disease.     

Triple responsive block copolymers combining pH‐responsive,thermoresponsive, and glucose‐responsive behaviors

Polymers with multiple tunable responses were achieved by incorporating boronic acid functionality along the backbone of a thermoresponsive polymer. The inherent Lewis acidity and diol‐sensitivity of boronic acid moieties allowed these polymers to respond to changes in pH and glucose concentration. Through reversible addition‐fragmentation chain transfer copolymerization of boronic acid‐containing monomers with N‐isopropylacrylamide, well‐defined block copolymers were synthesized containing a hydrophilic N,N‐dimethylacrylamide block and a second, responsive block with temperature‐dependent water solubility, making the resulting polymers capable of self‐assembly into nanostructures upon heating. By incorporating boronic acids within the thermoresponsive block, the cloud point of the polymer depended on the solution conditions, including pH and diol concentration, allowing tunable cloud point ranges. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2309–2317     

Application of a pH responsive multimodal hydrophobic interaction chromatography medium for the analysis of glycosylated proteins

Protein glycosylation has significant effects on the structure and function of proteins. The efficient separation and enrichment of glycoproteins from complex biological samples is one key aspect and represents a major bottleneck of glycoproteome research. In this paper, we have explored pH multimodal hydrophobic interaction chromatography to separate glycosylated from non-glycosylated forms of proteins. Three different proteins, ribonuclease, invertase and IgG, have been examined and different glycoforms have been identified. The media itself shows strong responsiveness to small variations in pH, which makes it possible to fine-tune the chromatographic conditions according to the properties of the protein isolated. Optimal glycoprotein separation has been obtained at pH 4. The pH responsive multimodal HIC medium in contrast to conventional HIC media is able to resolve contaminating DNA.     

Janus超支化超分子聚合物的构筑及电化学响应性自组装行为研究

本工作报道了第一例具有电化学氧化还原刺激响应性的Janus超支化超分子聚合物,研究了其自组装及响应性解组装的行为.通过阴离子开环聚合和阳离子开环聚合的方法,分别合成了以β-环糊精为中心的亲水超支化聚缩水甘油醚CD-g-HPG和末端为二茂铁的疏水超支化聚(3-乙基-3-羟甲基环氧丁烷)Fc-g-HBPO.两者通过Fc/CD之间的主客体包结络合作用,构筑了两亲性Janus超支化超分子聚合物HBPO-b-HPG.该聚合物在水中可以自组装形成囊泡.通过动态光散射(DLS)跟踪、2D-NOESY和循环伏安曲线表征了CD-g-HPG和Fc-g-HBPO之间的主客体包结络合作用,通过扫描电子显微镜(SEM)和透射电子显微镜(TEM)表征了囊泡结构.最后,研究了囊泡在电化学刺激下的解组装行为,同时也验证了囊泡在加热、加入主客体竞争分子和化学氧化下的稳定性.     

pH and glucose dually responsive injectable hydrogel prepared by in situ crosslinking of phenylboronic modified chitosan and oxidized dextran

Injectable hydrogels with pH and glucose triggered drug release capability were synthesized based on biocompatible phenylboronic modified chitosan and oxidized dextran through the formation of covalent imine bond and phenylboronate ester. Rheological characterization demonstrated that the gelation rate was rapid, and the moduli of the hydrogels were able to be tuned with chemical composition as well as pH and glucose concentration of the polymer solution. Anticancer drugs could be incorporated inside the hydrogel through the in situ gel forming process and undergo a controlled release by altering pH or glucose concentration. The hydrogels had good biocompatibility with viable and proliferated cells cultured in the three dimensional matrix, and the cell proliferation was suppressed when a small amount of DOX was added, which is benefit for the application of the hydrogels as smart anticancer drug delivery system. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1235–1244     

pH responsive surfaces with nanoscale topography

We report the preparation of nanostructured adaptive polymer surfaces by diffusion of an amphihilic block copolymer toward the interface. The surface segregation of a diblock copolymer, polystyrene‐block‐poly(acrylic acid) (PS‐b‐PAA), occurred when blended with high molecular weight polystyrene employed as a matrix. On annealing, the polymer surfaces changed both the chemical composition and the hydrophilicity depending on the environment and pH, respectively. By exposure to either water vapor or air, the surface wettability varied between hydrophilic and hydrophobic. In addition, surface enrichment on diblock copolymer by water vapor annealing led to self‐assembly occurring at the interface. Hence, nanostructured domains can be observed by AFM in liquid media. Moreover, the PAA segments placed at the interface respond to pH and can switch from an extended hydrophilic state at basic pH values to a collapsed hydrophobic state in acidic media. Accordingly, the surface morphology changed from swelled micelles to nanometer size holes. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2982–2990, 2010     

The pH and temperature dual-responsive micelle transition in the mixture of hydrotrope potassium phthalic acid and quaternary ammonium surfactants cetyltrimethylammonium bromide

A facile and effective route to prepare a pH and temperature dual-responsive surfactant micelle has been introduced based on hydrotrope potassium phthalic acid (PPA) and quaternary ammonium surfactants cetyltrimethylammonium bromide (CTAB). The system can be switched between viscoelastic solution and water-like fluid by adjusting pH values. In this paper, different binding abilities between the hydrotrope and surfactants have been demonstrated during the process of adjusting pH because the hydrotrope has different ionization degrees with the pH variation. And with the aid of rheological measurements and cryo-TEM observation, we discussed the different effects of the hydrotrope on surfactants at various pH values in detail and analyzed the possible aggregate transition mechanism of CTAB–PPA system induced by pH. Besides, this CTAB–PPA system has temperature-responsive property when pH?<?2.50. The temperature sensitivity and reversible control of rheological properties may greatly facilitate practical applications of such responsive viscoelastic solution.     

Janus粒子制备研究*

具有不对称双面结构的Janus粒子以其独特性能,在乳液稳定、光学、生物传感、药物输送、电子学等领域具有潜在的应用前景。本文就近年来Janus粒子制备技术的研究进展进行了总结,详细地介绍了Janus粒子主要制备方法,包括微流体合成、拓扑选择表面改性、模板导向自组装、可控相分离及可控表面成核,并指出了各种Janus粒子制备技术存在的问题及其发展方向,认为基于可控相分离及表面成核的合成方法成本较低,产率较大,有可能得到更为广泛的应用。     

Tailored Synthesis of Octopus‐type Janus Nanoparticles for Synergistic Actively‐Targeted and Chemo‐Photothermal Therapy

A facile, reproducible, and scalable method was explored to construct uniform Au@poly(acrylic acid) (PAA) Janus nanoparticles (JNPs). The as‐prepared JNPs were used as templates to preferentially grow a mesoporous silica (mSiO₂) shell and Au branches separately modified with methoxy‐poly(ethylene glycol)‐thiol (PEG) to improve their stability, and lactobionic acid (LA) for tumor‐specific targeting. The obtained octopus‐type PEG‐Au‐PAA/mSiO₂‐LA Janus NPs (PEG‐OJNP‐LA) possess pH and NIR dual‐responsive release properties. Moreover, DOX‐loaded PEG‐OJNP‐LA, upon 808 nm NIR light irradiation, exhibit obviously higher toxicity at the cellular and animal levels compared with chemotherapy or photothermal therapy alone, indicating the PEG‐OJNP‐LA could be utilized as a multifunctional nanoplatform for in vitro and in vivo actively‐targeted and chemo‐photothermal cancer therapy.     

Triple stimuli‐responsive amphiphilic glycopolymer

Triple stimuli (temperature/pH/photo)‐responsive amphiphilic glycopolymer, poly(2‐(dimethylamino)ethyl methacrylate‐co‐6‐O‐methacryloyl‐1,2,3,4‐di‐O‐isopropylidene‐D‐galactopyranose)‐b‐poly(4‐(4‐methoxyphenylazo)phenoxy methacrylate) [P(DMAEMA‐co‐MAIpGP)‐b‐PMAZO] was synthesized by atom transfer radical polymerization, followed by the hydrolysis of MAIpGP groups, resulting in the target product poly(2‐(dimethylamino)ethyl methacrylate‐co‐6‐O‐methacryloyl‐D‐galactopyranose)‐b‐poly(4‐(4‐methoxyphenylazo)phenoxy methacrylate) [P(DMAEMA‐co‐MAGP)‐b‐PMAZO]. The composition, moleculer weight, and moleculer weight distribution of the resultant polymers were characterized by ¹H NMR and gel permeation chromatography. The micelles formed in aqueous solutions were simulated by various chemical and physical stimuli and characterized by dynamic light scattering, transmission electron microscopy, and UV‐vis spectroscopy. It was found that the glycopolymer is responsive to three different types of stimulus (light, temperature, and pH). The poly(2‐(dimethylamino) ethyl methacrylate) segments give thermo‐ and pH‐responsiveness. The presence of the azobenzene moiety endows the block copolymer to exhibit light‐responsiveness due to its reversible trans‐cis isomerization conversion. The triple stimuli‐responsive glycopolymer micelles can simulate biomacromolecues in vivo/in vitro environment and can be expected to open up new applications in various fields. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2131–2138     

Thermal and pH responsive high molecular weight poly(urethane‐amine) with high urethane content

Aliphatic poly(urethane‐amine) (PUA) was synthesized from copolymerization of CO₂ and 2‐methylaziridine (MAZ) using Y(CCl₃COO)₃‐ZnEt₂‐glycerine coordination catalyst, the urethane content of PUA was over 80%, and its yield could reach 90%. PUA with molecular weight as high as 31.0 kg/mol was obtained when the copolymerization reaction was carried out in N,N‐dimethylacetamide (DMAc), mainly due to the good solubility of PUA in DMAc. PUA exhibited reversible thermo‐responsive property in deionized water, and the lower critical solution temperature (LCST) was highly sensitive to its urethane content and molecular weight, which was observed in a broad window from 37 to 90 °C. Furthermore, the phase transition behavior could also be controlled by change of pH value. When the pH value of the PUA aqueous solution changed from 9.2 to 13, the LCST value of the solution decreased from 48.4 °C to 30 °C. Therefore, the PUA showed thermo‐ and pH‐ dual responsive performance in water. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

RAFT made methacrylate copolymers for reversible pH‐responsive nanoparticles

In this study, we designed and investigated pH‐responsive nanoparticles based on different ratios of monomers with primary, secondary or tertiary amino groups. For this purpose, copolymers of methyl methacrylate (MMA) with different compositions of amino methacrylates (2‐(dimethylamino)ethyl methacrylate (DMAEMA), 2‐(tert‐butylamino)ethyl methacrylate (tBAEMA) and 2‐aminoethyl methacrylate hydrochloride (AEMA·HCI)) were synthesized using the reversible addition‐fragmentation chain transfer (RAFT) polymerization process. The controlled nature of the radical polymerization was demonstrated by kinetic studies. All copolymers show low dispersities (?_M < 1.2) with amino contents between 9 and 21 mol %. For the nanoparticle formation, nanoprecipitation with subsequent solvent evaporation was used. All suspensions were characterized by dynamic light scattering (DLS) and scanning electron microscopy (SEM). Different initial conditions of the formulations resulted in differently sized nanoparticles that have monomodal size distributions, relatively narrow polydispersity index (PDI) values and positive zeta potential values. The pH‐stability test results demonstrated that, depending on the structure and amount of the amino content, the obtained nanoparticles reveal a reversible pH‐response, such as dissolution at acidic pH values. The ability of the nanoparticles to encapsulate guest molecules was confirmed by pyrene fluorescence studies. The cytotoxicity assay results showed that the nanoparticles did not have any significant cytotoxic effect. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2711–2721     

Ultrafine hydrogel fibers with dual temperature‐ and pH‐responsive swelling behaviors

Ultrafine hydrogel fibers that were responsive to both temperature and pH signals were prepared through the electrospinning of poly(N‐isopropylacrylamide) (PNIPAAm) and poly(acrylic acid) mixtures in dimethylformamide. Both the diameters (700 nm to 1.2 μm) and packing of the fibers could be controlled through changes in the polymer compositions and PNIPAAm molecular weights. These fibers were rendered water‐insoluble by the addition of either Na₂HPO₄ or poly(vinyl alcohol) (PVA) to the solution, followed by the heat curing of the fibers. The fibers crosslinked with Na₂HPO₄ swelled to 30–120 times in water; this was significantly higher than the swelling of those crosslinked with PVA. The PVA‐crosslinked hydrogel fibers, however, exhibited faster swelling kinetics; that is, they reached equilibrium swelling in less than 5 min at 25 °C. They were also more stable after 1 week of water exposure; that is, they lost less mass and retained their fibrous form better. All the hydrogel fibers showed a drastic increase in the swelling between pH 4 and 5. The PVA‐crosslinked hydrogel fibers exhibited distinct temperature‐responsive phase‐transition behavior of PNIPAAm, whereas the Na₂HPO₄‐crosslinked hydrogel fibers showed altered two‐stage phase transitions that reflected side‐chain modification of PNIPAAm. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6331–6339, 2004     

Janus复合材料

Janus复合材料基本特征在于其微尺度空间具有明确分区的化学和功能。关键问题在于发展新方法,精确控制形貌、微结构、和表面化学和功能严格分区。本文主要总结了本课题组的有关点滴成果,指出了存在的重要问题及发展方向,展望了近期有望突破领域。