芘在Pluronic两亲嵌段共聚物胶团中的增溶

用稳态荧光法研究芘（Py）在Pluronic两亲嵌段共聚物胶团水溶液中的增溶,结果表明共聚物分子中的PPO实际含量越大,越有利于Py的增溶。加入无机盐KCl导致生成了表面较少水化的较大胶团,并且由于KCl解离产生的离子使溶剂极性增加,这些因素促进了Py的增溶。     

A viscosity-tunable polymer for DNA separation by microchip electrophoresis

A thermo-responsive separation matrix, consisting of Pluronic F127 tri-block copolymers of poly(ethylene oxide) and poly(propylene oxide), was used to separate DNA fragments by microchip electrophoresis. At low temperature, the polymer matrix was low in viscosity and allowed rapid loading into a microchannel under low pressure. With increasing temperatures above 25°C, the Pluronic F127 solution forms a liquid crystalline phase consisting of spherical micelles with diameters of 17–19 nm. The solution can be used to separate DNA fragments from 100 bp to 1500 bp on poly(methyl methacrylate) (PMMA) chips. This temperature-sensitive and viscosity-tunable polymer provided excellent resolution over a wide range of DNA sizes. Separation is based on a different mechanism compared with conventional matrices such as methylcellulose. To illustrate the separation mechanism of DNA in a Pluronic F127 solution, DNA molecular imaging was performed by fluorescence microscopy with F127 polymer as the separation matrix in microchip electrophoresis. Figure Temperature dependence of the viscosity of 20% w/w Pluronic F127 solution in 1xTBE buffer. Dotted approximates resultant curve.     

Dissolution enhancement of quercetin through nanofabrication, complexation, and solid dispersion

The main aim of this study was to enhance the dissolution rate of a poorly water-soluble antioxidant drug, quercetin, by fabricating its nanoparticles, complexes and solid dispersions using evaporative precipitation of nanosuspension (EPN). We studied the influence of the type of antisolvent, drug concentration and solvent to antisolvent ratio on the quercetin particles formed during EPN. With water as antisolvent, the particles were big, irregular and flake type but with benzene or hexane as antisolvent, the particles were smaller and needle type. Smallest particles of 220 nm diameter were achieved with hexane as antisolvent, lowest drug concentration and highest solvent to antisolvent ratio. The relative dissolution values showed that the dissolution rate of the EPN prepared quercetin nanoparticles was much higher than that of the raw drug. Quercetin formed inclusion complexes with β-cyclodextrin, and solid dispersions with polyvinylpyrrolidone and pluronic F127, where quercetin was present in an amorphous form and/or was dispersed at a molecular level. The dissolution rate of quercetin in its complexes and solid dispersions improved significantly from the raw quercetin as indicated by the percent dissolution efficiency. It was interesting to note that at lower carrier concentration, the solid dispersions of quercetin with polyvinylpyrrolidone and pluronic F127 presented better dissolution than its complex with β-cyclodextrin but at higher carrier concentration, there was no significant difference in the dissolution behavior of the three formulations. Using Korsmeyer-Peppas model, diffusion was found to be the main release mechanism.     

The Effects of Salts and Ionic Surfactants on the Micellar Structure of Tri‐Block Copolymer PEO‐PPO‐PEO in Aqueous Solution

The micelles of two poly(ethylene oxide)‐poly(propylene oxide)‐poly(ethylene oxide) (PEO‐PPO‐PEO) block copolymers, P123 and F127 (same mol wt of PPO but different % PEO) in aqueous solution in the absence and presence of salts as well as ionic surfactants were mainly examined by dynamic light scattering (DLS). The study is further supported by cloud point and viscosity measurements. The change in cloud point (CP), as well as the size of micelles in aqueous solution in presence of salts obeys the Hofmeister lyotropic series. Addition of both cationic cetylpyridinium chloride (CPC) and anionic sodium dodecylsulfate (SDS) surfactants in the aqueous solution of P123 show initial decrease of micellar size from 20 nm to nearly 7 nm and then increasing with a double relaxation mode, further in the presence of NaCl this double relaxation mode vanishes. The effect of surfactant on F127, which has much bigger hydrophilic part is different than P123 and have no double relaxation. The relaxation time distributions is obtained using the Laplace inversion routine REPES. Two relaxation modes for P123 are explained on the bases of Pluronic rich mixed micelles containing ionic surfactants and the other smaller, predominantly surfactant rich micelles domains.     

Synthesis and characterization of amphiphilic fluorinated pentablock copolymers based on Pluronic F127

The synthesis and self‐assembly behavior of pentablock copolymers consisting of Pluronic F127 (PEO₁₀₀‐PPO₆₅‐PEO₁₀₀) and poly(2, 2, 3, 3, 4, 4, 5, 5‐octafluoropentyl methacrylate) (POFPMA) is herein described. Using the difunctional potassium alcoholate of F127, K⁺O^–‐(PEO₁₀₀‐PPO₆₅‐PEO₁₀₀)‐O^–K⁺, as the macroinitiator, the POFPMA‐F127‐POFPMA pentablock copolymers were synthesized via oxyanion‐initiated polymerization. The chain length of POFPMA can be controlled by the original molar ratio of macroinitiator to OFPMA monomer, that is, F‐monomer. The composition and chemical structure of POFPMA‐F127‐POFPMA pentablock copolymers have been characterized by FTIR, ¹HNMR, and ¹⁹F NMR spectroscopy, and gel permeation chromatography techniques. The solution behavior of POFPMA‐F127‐POFPMA copolymers was investigated by the methods of surface tension, cloud point, transmission electron microscopy, and high performance particle sizer (HPPS). The results indicate that these Pluronic F127‐based block copolymers modified with fluorinated segments possess relatively high surface activity and low cloud points, depending on various factors, such as the length of fluorinated block, the concentration of the copolymers in aqueous solution, and the adscititious inorganic salt. TEM measurements showed that the pentablock copolymers can self‐assemble in aqueous solution to form various micellar morphologies. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3029–3041, 2008     

Simple,Rapid, and Large-Scale Fabrication of Multi-Branched Hydrogels Based on Viscous Fingering for Cell Culture Applications

Hydrogels are widely used in cell culture applications. For fabricating tissues and organs, it is essential to produce hydrogels with specific structures. For instance, multiple-branched hydrogels are desirable for the development of network architectures that resemble the biological vascular network. However, existing techniques are inefficient and time-consuming for this application. To address this issue, a simple, rapid, and large-scale fabrication method based on viscous fingering is proposed. This approach utilizes only two plates. To produce a thin solution, a high-viscosity solution is introduced into the space between the plates, and one of the plates is peeled off. During this procedure, the solution's high viscosity results in the formation of multi-branched structures. Using this strategy, 180 mm × 200 mm multi-branched Pluronic F-127 hydrogels are successfully fabricated within 1 min. These structures are used as sacrificial layers for the fabrication of polydimethylsiloxane channels for culturing human umbilical vein endothelial cells (HUVECs). Similarly, multi-branched Matrigel and calcium (Ca)-alginate hydrogel structures are fabricated, and HUVECs are successfully cultured inside the hydrogels. Also, the hydrogels are collected from the plate, while maintaining their structures. The proposed fabrication technique will contribute to the development of network architectures such as vascular structures in tissue engineering.     

Fast separation of single-stranded oligonucleotides by capillary electrophoresis using OliGreen as fluorescence inducing agent

The fast separation of oligonucleotide (oligos) sizing marker by CE using OliGreen and including effects due to the concentration of separation medium and urea denaturant is presented. OliGreen dye is found to be more sensitive than ethidium bromide (by a factor of about 6 based on S/N considerations) for the oligos' separations. Higher concentration of F127 in 1xTris-boricacid-EDTA (TBE) up to 30% w/v leads to better resolution of oligos separations. The addition of urea into the separation medium decreases the sensitivity. With an optimized running condition, the oligos sizing marker could be successfully separated with 1-base resolution within 1.3 min by using 30% w/v F127/1xTBE solution as the separation medium at an applied electric field of 800 V/cm in a 3 cm long capillary, the fastest capillary gel electrophoresis separation with high resolution reported to date for oligos in the similar size range.     

Facile fabrication of novel polycaprolactone-based electrospun fibers using in-process water exposure

To overcome the problems related to the low surface enrichment of blended fibers from hydrophilic polymer, routine blend electrospinning setup was modified by exposing the polycaprolactone (PCL)–Pluronic P123 solution to water in order to attract the hydrophilic chains toward the fiber surface. Analysis of the modified fibers revealed a drastic surge of hydrophilic polymer surface enrichment value in comparison with that of the routine method which suggested homogenously positioned Pluronic on the surface and the subsequent reduction of its accumulations within fibers. The thermogram of the proposed method showed induced crystallization in the Pluronic section. Furthermore, the intensity of PCL characteristic peaks decreased for this method.     

Amphiphilic polylactide-poly(ethylene oxide)-poly(propylene oxide) block copolymers: Self-assembly behavior and cell affinity

Polylactide (PLA) is a biodegradable polyester recognized for its potential use as a biomedical material. Poly(ethylene oxide) (PEO) and copolymers based on PEO and poly(propylene oxide) (PPO) are biocompatible polyethers widely applied in the biomedical field, particularly as macromolecular nonionic surfactants. In this work, PLA blocks were attached to the PEO and to the PEO and PPO-based triblock copolymer PEO–PPO–PEO, through ring-opening polymerization of racemic lactide (rac-LA) to obtain the amphiphilic triblock PLA–PEO–PLA and pentablock PLA–PEO–PPO–PEO–PLA copolymers containing hydrophilic/hydrophobic blocks with variable block mass ratios. The copolymers were evaluated for chemical composition, molar mass, and thermal properties, and they were used to prepare self-assemble aggregates in water from tetrahydrofuran polymer solutions. The combination of scattering light experiments and microscopy techniques revealed the spherical morphology of the aggregates with diameters around 180–200 nm, which comprises a hydrophobic PLA core and a hydrophilic polyether shell. The aggregates are nontoxic to human cervical cancer cell line — HeLa cells, as determined by MTS assay, and the aggregates are potential candidates to be applied in the encapsulation of hydrophobic compounds. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2203–2213     

Micellization-induced deprotonation of thermoresponsive surfactant CAE-85 — the telechelic carboxylic group derivative of Pluronic P85

Temperature-induced micellization of CAE-85, a carboxylic acid end-standing derivative of a triblock copolymer Pluronic P85, was studied by attenuated total reflectance Fourier-transform infrared spectroscopy (ATR FTIR) and density functional theory (DFT) model calculations. It was found that in polymer micelles carboxyl end groups dissociated and it was a two stage process. The first stage of deprotonation appeared with the onset of micellization and it was in agreement with predictions of existing models and theories for ionization processes in micellar corona. In micelles well above the critical micellization temperature, the degree of CAE-85 deprotonation increased further to values significantly higher compared to unimer solution. It is proposed that such deprotonation correlates with the formation of hydrogen bonded carboxyl end groups enabled by sufficient density of chains in the corona of developing micelles. It was demonstrated that the proton dissociation constant, pK_m, specific to the micellar form existed and was different from the proton dissociation constant of solution of unimers, pK_a.