查找使用阿拉丁产品的科研文献

pH-dependent and self-healing properties of mussel modified poly(vinyl alcohol) hydrogels in a metal-free environment

Dongjian Shi,Rongjin Liu,Weifu Dong,Xiaojie Li,Hongji Zhang,Mingqing Chen,Mitsuru Akashi

3,4-Dihydroxyphenylalanine (DOPA)-based polymers are well-known to form functional hydrogels with self-healing properties by chelating metal ions. However, DOPA-based hydrogels with self-healing properties are difficult to obtain in the absence of the metal ions, as previously reported. Thus, the aim of this study is to prepare a self-healable DOPA-based hydrogel in the absence of metal ions. Firstly, poly(vinyl alcohol)–DOPA (PVA–DOPA) was synthesized by modifying PVA with DOPA through an esterification reaction. The composition of the PVA–DOPA polymer was determined by proton nuclear magnetic resonance (1H NMR) spectroscopy. Then, the PVA–DOPA hydrogel in a metal-free environment could be easily prepared by dissolving the polymer in buffer solution. Rheological analyses showed that the PVA–DOPA polymers had different dynamic moduli depending on the pH of the buffer solutions. The results from the FTIR and UV-vis spectra indicated that there were hydrogen bond interactions between the PVA–DOPA polymers under low pH conditions, while there were both hydrogen bond and covalent interactions under high pH conditions. The PVA–DOPA hydrogel could be rapidly self-healed within 270 s, which was much quicker than the hydrogel prepared in the presence of Fe3+ (about 600 s). The metal-free PVA–DOPA hydrogel has the potential for application in coating and biomedical fields.

Injectable shell-crosslinked F127 micelle/hydrogel composites with pH and redox sensitivity for combined release of anticancer drugs

Nannan Gao,Shaoyu Lü,Chunmei Gao,Xinggang Wang,Xiubin Xu,Xiao Bai,Chen Feng,Mingzhu Liu

Combination chemotherapy as a preferred strategy for cancer treatment has been widely developed recently. However, single drug carriers of the combination chemotherapy systems are difficult to address the performance requirement that delivers hydrophilic and hydrophobic drugs simultaneously. In this work, a smart dual drug delivery system of injectable micelle/hydrogel composite was developed. This smart drug delivery system consists of curcumin (Cur) loaded shell-crosslinked F127 micelle and 5-fluorouracil (Fu) dispersed chitosan/oxidized dextran (CS/ODex) hydrogel. Both of the shell-crosslinked F127 micelle and CS/ODex hydrogel were prepared based on Schiff base bonds, which provides pH-sensitivity and biodegradability for the system. In addition, disulfide bonds were introduced in the shell of F127 micelle, allowing for redox-sensitivity of the system. The system was detailed characterized by 1 H NMR, FTIR, TEM, SEM, DLS and fluorescence spectroscopy. Independent release behaviors of the two drugs are observed under conditions of different precursor concentration, different CS/ODex proportion, different pH and different concentration of DTT. The results show that the drug carrier has pH and redox sensitivity and the release rate can be adjusted by the concentration of the precursor solution. In vitro degradation experiment and cytotoxicity assay determine that the system has good biodegradability and biocompatibility. These results indicated that the injectable shell-crosslinked F127 micelle/hydrogel composite may load and deliver hydrophobic and hydrophilic drugs simultaneously and find application in combination chemotherapy for cancer treatment.

The fabrication of pH-responsive polymeric layer with switchable surface wettability on cotton fabric for oil/water separation

Jindan Wu,Yuelin Jiang,Dongjie Jiang,Ju He,Guoqiang Cai,Jiping Wang

Cotton textile with special surface wettability has a promising future for oil/water separation due to its high adsorption capacity and low cost. A facile method was employed to prepare a durable polymeric layer with pH-triggered switchable surface wettability on cotton fabric. An amino-containing dye intermediate (2-Chloro-4,6-diamino-1,3,5-triazine, CDATA) was used to produce more reactive grafting sites for surface initiated atom transfer radical polymerization (SI-ATRP) of poly(methacrylic acid) (PMAA). The obtained cotton-PMAA fabric showed high pH-responsibility, which was indicated by the shift of O–C=O peaks in Infrared (IR) spectrum and the transition of water/oil contact angle (WCA/OCA). Moreover, with the rising pH, the surface transited from superhydrophobic to superhydrophilic and underwater superoleophobic, leading to efficient oil/water separation. This study provides an innovative way to fabricate smart cotton fabric with high efficiency and high selectivity for oil/water separation.

pH-Controlled Selective Separation of Neodymium (III) and Samarium (III) from Transition Metals with Carboxyl-Functionalized Ionic Liquids

Yuehua Chen,Huiyong Wang,Yuanchao Pei,Jiao Ren,Jianji Wang

The recovery of rare-earth metals from waste materials is very important due to the risks associated with having a low supply of them in the future. In this work, hydrophobic 1-alkylcarboxylic acid-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquids, [(CH2)nCOOHmin][Tf2N] (n = 3, 5, 7), were synthesized and used to separate neodymium (III) from Fe(III) and samarium (III) from Co(II) in aqueous solutions. The factors affecting the solvent extraction process such as phase volume ratio, contact time, pH value of the aqueous phase, alkyl chain length of the ionic liquids, and temperature of the system were examined systematically. It was found that the maxmium extraction efficiency of the investigated metal ions was as high as 99%, and Sm(III) and Nd(III) could be selectively separated from Co(II) and Fe(III), with separation factors of 104–105, by simply modulation of the aqueous phase pH. After extraction, about 97% of the metal ions could be stripped from ionic liquid phase in a single stripping step by using dilute aqueous HCl or oxalic acid, and the ionic liquids would be recovered and reused in the next extraction process. These results indicate that the ionic liquids developed here are useful for the selective recovery of rare-earth metals from NdFeB and SmCo permanent magnets.

pH/redox responsive core cross-linked nanoparticles from thiolated carboxymethyl chitosan for in vitro release study of methotrexate

Cheng Gao,Ting Liu,Yinghua Dang,Zhiyan Yu,Wei Wang,Jingjing Guo,Xueqiong Zhang,Guanghua He,Hua Zheng,Yihua Yin,Xiangqi Kong

A novel amphiphilic thiolated carboxymethyl chitosan was synthesized. It self-assembled into disulfide bond cross-linked nanoparticles in deionized water. The TEM showed that these nanoparticles had a core–shell structure with an average diameter of 160   nm. Dynamic light scattering showed that the nanoparticles were stable in water solution. The particle size changed with pH values and GSH concentrations, and reached a maximum diameter at pH 7.0 and 20   mM GSH respectively, exhibiting an obvious pH/redox responsibility. Methotrexate was encapsulated in nanoparticles reaching encapsulation efficiency as much as 43.4%. Release profiles of methotrexate showed a release rate of 19   wt% in pH 7.4 buffer containing 10   μM GSH, whereas as high as 93   wt% in pH 5.0 buffer containing 20   mM GSH, indicating that the nanoparticles may be used for tumor-specific drug release. The anticancer activity test in vitro showed that the inhibition rate of methotrexate-loaded nanoparticles against HeLa cells reached 90%.

Hierarchical Porous Co9S8/Nitrogen-Doped Carbon@MoS2 Polyhedrons as pH Universal Electrocatalysts for Highly Efficient Hydrogen Evolution Reaction

Hongmei Li,Xing Qian,Chong Xu,Shaowei Huang,Changli Zhu,Xiancai Jiang,Li Shao,Linxi Hou

The development of highly active and stable earth-abundant electrocatalysts to reduce or eliminate the reliance on noble-metal based ones for hydrogen evolution reaction (HER) over a broad pH range remains a great challenge. Herein, hierarchical porous Co9S8/N-doped carbon@MoS2 (Co9S8/NC@MoS2) polyhedrons have been synthesized by a facile hydrothermal approach using highly conductive Co/NC polyhedrons composed of cobalt nanoparticles embedded in N-doped carbon matrices as both the structural support and cobalt source. The Co/NC polyhedrons were prepared by direct carbonization of Co-based zeolitic imidazolate framework (ZIF-67) in Ar atmosphere. Benefiting from the prominent synergistic effect of N-doped carbon enhancing the conductivity of the hybrid, MoS2 and Co9S8 providing abundant catalytically active sites as well as the well-defined polyhedral structure promoting mechanical stability, the as-synthesized Co9S8/NC@MoS2 shows excellent HER activity and good stability over a broad pH range, with onset overpotentials of 4, 38, and 45 mV, Tafel slopes of 60.3, 68.8, and 126.1 mV dec–1, and overpotentials of 67, 117, and 261 mV at 10 mA cm–2 in 1.0 M KOH, 0.5 M H2SO4, and 1.0 M phosphate buffer solution (PBS), respectively. This work provides a general and promising approach for the design and synthesis of inexpensive and efficient pH-universal HER electrocatalysts.

pH-dependent KOW provides new insights in understanding the adsorption mechanism of ionizable organic chemicals on carbonaceous materials

Hao Li,Yanbei Cao,Di Zhang,Bo Pan

The dominant adsorption mechanism of ionizable organic chemicals (IOCs) on carbonaceous materials is still unclear. This study used benzoic acid (BA), o -chlorobenzoic acid (2-CBA) and p -chlorobenzoic acid (4-CBA) as representatives of IOCs to investigate the dominant adsorption mechanism on graphene oxide (GO) and graphite (GP), with a specific emphasis on the impact of pH-dependent K OW . The order of apparent adsorption of the investigated chemicals changed with pH, which could not be explained by their constant K OW . According to our measurement, K OW varied greatly with pH. The pH-dependent adsorption of BA, 2-CBA and 4-CBA were significantly correlated with pH-dependent K OW for both GO and GP. Our observations indicated that the hydrophobic effects may dominate the apparent adsorption of BA, 2-CBA and 4-CBA on GO and GP. Electrostatic repulsion played a minor role in their reduced adsorption at high pH. Negative charge-assisted H-bond and π-π interactions may explain the adsorption of negatively charged BA, 2-CBA and 4-CBA on negatively charged GO. This study implied that pH-dependent K OW rather than constant K OW should be incorporated to understand IOC adsorption as affected by pH.

A off–on pH fluorescence probe derived from phenanthro[9,10-d]imidazol-fluorescein based on ESIPT and ICT

Li Shaoxin,Zhao Bing,Kan Wei,Wang Liyan,Song Bo,Chen Shuwen

A novel pH fluorescence probe (PIF), derived from phenanthro[9,10- d ]imidazole bound to the fluorescein, is designed and synthesized based on the intramolecular hydrogen bond and then its spectra properties are investigated. Probe PIF exhibits negligible fluorescence intensity at acidic pH condition due to ESIPT quenching caused by the formation of the intramolecular hydrogen bonds, and a significant fluorescence enhancement in neutral and weak alkaline environments because of the strengthened ICT process arose from the fracture of the intramolecular hydrogen bonds. The studies of UV–Vis and fluorescence spectra mean that probe PIF is able to respond linearly and reversibly over pH from 6.5 to 9.0 with p K a of 7.0. Moreover, the pH responses of probe PIF are stable and not disturbed by the common cations and anions. The possible response mechanism has been proposed according to the analysis of 1 H NMR and DFT calculations.

Synthesis and in vitro evaluation of pH-sensitive PEG-I-dC16 block polymer micelles for anticancer drug delivery

Rongbin Huang,Lei Xiang,Ying Liu,Xiangping Deng,Xuan Cao,Lanfang Li,Cuiyun Yu,Yanming Chen,Guotao Tang

ObjectivesTo develop an acid trigger release of antitumour drug delivery carriers, pH-sensitive amphiphilic poly (ethyleneglycol)-imine-benzoic-dipalmitate (PEG-I-dC16) polymers were designed and synthesized and the drug-loaded micelles were evaluated in vitro.MethodsPEG-I-dC16 synthesized by Schiff base synthetic method and characterized by 1H-NMR. To determine the drug-loading capacity, doxorubicin (DOX) was encapsulated in the micelles using membrane dialysis method. Zeta potential, particle size, drug-loading capacity, in vitro drug release in different pH conditions and cytotoxicity evaluation of micelles were carried out comparing with non-acid liable PEG–amide–benzoic–dipalmitate (PEG-A-dC16) polymers micelles. The cellular uptake and intracellular distribution of DOX were detected by flow cytometry and confocal laser scanning microscope.Key findingsDrug-loading capacity and encapsulation efficiency of micelle (PEG molecular weight 2k) were 12.7 ± 1.1% and 49.8 ± 2.2%, respectively. The average particle size was 72.3 ± 2.5 nm. The DOX release rate of PEG-I-dC16 micelles is much higher at pH 6.5 than at pH 7.4. DOX cellular uptake and nuclear accumulation of PEG-I-dC16 micelles were more efficiency than that of PEG-A-dC16 micelles.ConclusionThe pH-sensitive PEG-I-dC16 micelles could be a promising drug delivery system for anticancer drugs.

Preparation, antibacterial activity and pH-responsive release behavior of silver sulfadiazine loaded bacterial cellulose for wound dressing applications

Wei Shao,Hui Liu,Jimin Wu,Shuxia Wang,Xiufeng Liu,Min Huang,Peng Xu

Bacterial cellulose (BC) has been extensively explored as some of the most promising biomaterials for biomedical applications. However, BC does not have intrinsically antibacterial property. In the present study, antibacterial BC-silver sulfadiazine (AgSD) composites were prepared by a simple blend method since AgSD is a topical antibacterial agents used as a topical cream on burns. The prepared composites were characterized by several techniques including SEM, FTIR, XRD and TG. These results indicate AgSD was successfully impregnated into BC matrix. The releases of Ag + and SD − ions from BC-AgSD composites at different pH values were studied, which showed pH-sensitive controlled release behaviors. The antibacterial performances of BC-AgSD composites were evaluated with Staphylococcus aureus and Candida albicans . Moreover, the cytotoxicity of BC-AgSD composites was performed on HEK293 cells. The present work demonstrates a facile way to prepare BC-AgSD composites with excellent antibacterial activities and good biocompatibility, which can be used as potential wound dressings.

Novel europium (III)-gatifloxacin complex structure with dual functionality for pH sensing and metal recognition in aqueous environment

Muhua Chen,Yuhui Zheng,Jinwei Gao,Qianming Wang

A new type of Eu(III)-gatifloxacin complex with characteristic red luminescence has been prepared. Due to the presence of ionization effect linked to the organic chromophore , the molecular fluorescent sensor demonstrated variable pH-sensitive absorption and emission curves. The red emission derived from europium ions was strong during pH range 8–10. Between pH = 7 and 4, the europium emission remained relatively stable and fluorescence signals of gatifloxacin has been improved substantially. Under acidic conditions (pH = 1 to 3), the dramatic changes in the emission colors (from red, yellow to green) were clearly observed. Moreover, the excitation wavelength can be extended into the visible light range (Ex = 411 nm) by using the concentration effect experiment. Importantly, it gave turn- off emissions in the presence of Cu 2+ or Fe 3+ and the detection limits were determined to be 6.5 μM for Cu 2+ and 6.2 μM for Fe 3+ respectively.

Magnetic targeted drug delivery carriers encapsulated with pH-sensitive polymer: synthesis, characterization and in vitro doxorubicin release studies

Juan Wu,Yueqing Shen,Wei Jiang,Wei Jiang,Yewen Shen