F127 Block Copolymer Research Articles

Interaction between Albumin and Pluronic F127 Block Copolymer Revealed by Global and Local Physicochemical Profiling.

The interaction of human serum albumin (HSA) with amphiphilic block copolymer Pluronic F127 has been investigated by several physical methods. Interest in studying this system stems from a broad range of bioactivities involving both macromolecules. Serum albumins constitute a significant class of proteins in the circulatory system, acting as carriers for a wide spectrum of compounds or assemblies. Pluronic block copolymers have revealed their capacity to ferry a variety of biologically active compounds. Circular dichroism, rheological measurements, and differential scanning microcalorimetry (μDSC) were employed to get insight into the interaction betweeen the two macromolecules. The results reveal that Pluronic F127 induces conformational changes to albumin if it is organized in a micellar form, while albumin influences the self-assembly of Pluronic F127 into micelles or gels. F127 micelles, however, induce smaller conformational changes compared to ionic surfactants. The μDSC thermograms obtained for HSA and/or F127 show that HSA shifts the critical micellar temperature (cmt) to lower values, while concurrently the HSA denaturation behavior is influenced by F127, depending on its concentration. Rheological measurements on solutions of F127 17% have shown that a sol-to-gel transition occurs at higher temperatures in the presence of HSA and the resulting gel is weaker. The global profile on HSA/F127 systems was complemented by local information provided by EPR measurements. A series of X-band EPR experiments was performed with spin probes 4-(N,N'-dimethyl-N-hexadecyl)ammonium-2,2',6,6'-tetramethylpiperidine-1-oxyl iodide (CAT16) and 5-doxyl stearic acid (5-DSA). These spin probes bind to albumin sites and are sensitive to phase transformations in Pluronic block copolymer solutions. For a given F127 concentration, the spin probe binds only to HSA below cmt and migrates to the F127 micelles above cmt. The collective data suggest soft interactions between the macromolecules, with the emerging results projecting potential applications linked to reaching optimal conditions for certain drug formulations.

Enhanced Binding of Phenosafranin to Triblock Copolymer F127 Induced by Sodium Dodecyl Sulfate: A Mixed Micellar System as an Efficient Drug Delivery Vehicle.

In this study, we explored the interaction of a cationic phenazinium dye, phenosafranin (PSF, here used as a model drug), with pluronic block copolymer F127, both in the presence and in the absence of the anionic surfactant sodium dodecyl sulfate (SDS), which forms mixed micelles with F127. We applied both steady-state and time-resolved spectroscopic techniques, along with isothermal titration calorimetry (ITC), to demonstrate the binding of the probe PSF to both the pluronic and F127/SDS mixed micelles. Dynamic light scattering (DLS) study revealed that, upon interaction with SDS, the hydrodynamic diameter (dH) of F127 micelles decreased due to the formation of the mixed micelles. The PSF penetrated to the more hydrophobic interior of the mixed micellar system as compared to F127 micelles alone. Micropolarity and fluorescence-quenching experiments revealed that PSF is more deeply seated in the case of F127/SDS mixed micelles. Through a partition coefficient, lifetime measurements, and time-resolved anisotropy experiments, we also established that the partitioning of the probe within the F127 micelles in the presence of SDS is almost double than that in its absence. ITC data corroborates the fact that the binding of PSF is the strongest and most thermodynamically favorable when mixed micelles are formed, which enables our system to serve as an excellent drug delivery vehicle when compared to F127 alone.

Aqueous synthesis of bimodal mesoporous carbons and carbon-silica mesostructures under basic conditions

Carbonization of the composite materials obtained by co-condensation of phenol-formaldehyde resin and tetraethyl orthosilicate (TEOS) in a basic aqueous solution in the presence of Pluronic F127 block copolymer template yields mesoporous carbon/silica composite materials (CSX). These materials have mesopore volumes of about 0.4 cm3/g and pore sizes between 6 and 8 nm (at the maximum of the pore size distribution) that are larger than those of the ordered mesoporous carbons (OMC) synthesized by the same procedure but without TEOS. Calcination of CSX in air yields mesoporous silicas (SX) with pore sizes around 11 nm and pore volumes of about 1 cm3/g. Dissolution of the silica domains in CSX yields carbons (CX) with pore volumes and surface areas as high as 1.84 cm3/g and 1500 m2/g, respectively. These carbons feature bimodal structures with larger mesopores of about 7–8 nm (porosity of CSX) and smaller mesopores with sizes closer to 5 nm, which are created by silica dissolution. The mesopore volume of CX after silica dissolution can be tuned by varying carbonization temperature (between 500 and 850 °C) to modify the concentration of silica nanodomains in CSX without significant change in the size of mesopores in CSX. Regardless of the phenol/TEOS ratio used (between 2 and 7) all the materials have similar composition, pore size distribution and pore volumes; however, the synthesis yield decreases with decreasing amount of TEOS. The final SiO2 content in CSX does not increase with the amount of TEOS added like in the synthesis of OMC by evaporation induced self-assembly or self-assembly in acidic solutions.

Copolymer-assisted fabrication of rambutan-like SnO2 hierarchical nanostructure with enhanced sensitivity for n-butanol

In this paper, rambutan-like SnO2 hierarchical nanostructure assembled with a number of nanosheets has been successfully prepared through a facile hydrothermal route with the synergistic effect of block copolymer F127 (EO106-PO70-EO106) and Na3C6H5O7. The structure and morphology were characterized by TEM, SEM, XRD, IR and BET techniques. The formation of SnO2 architecture underwent the nucleation, oriented growth and a phase transformation process. Besides that, Ag/SnO2 products with different amounts of Ag doping were also obtained. As gas-sensing materials, both SnO2 and Ag/SnO2 products demonstrated sensitive and selective response to several hazardous gases, especially for n-butanol at a low work temperature of 140 °C compared with the commercial SnO2. Significantly, the Ag/SnO2 product with 5 wt% Ag doping exhibited the most excellent gas sensing proprieties of 44.3–100 ppm n-butanol at 140 °C with a fast response and recovery time of 8/5s. The improvement may on account of their unique nanostructures, large surface areas and the decoration of Ag nanoparticles.

Deposition of silicon dioxide antireflection coatings on glass by sol-gel method in the presence of Pluronic® F127 block-copolymer

Hydrolysis of tetraethoxysilane in the presence of Pluronic® F127 block-copolymer in a water-alcohol mixture was used to obtain sol-formulations from which antireflection coatings were deposited onto silicate glass by the dip-coating method and then calcined at high temperatures (200–500°C). Electron spectroscopy was used to study the dependence of the optical transmission of glass samples with a coating on the concentration of Pluronic® F127 in the starting sol, introduction of organic additives (toluene) into the sol, and calcination temperature of the glasses obtained. The refractive index and hardness of the film coatings were determined and their surface structure was assessed.

Catalytic hydroxylation enables phenol to efficient assembly of ordered mesoporous carbon under highly acidic conditions

As an important route towards the preparation of ordered mesoporous carbon (OMC), the aqueous assembly method with phenol as precursor still faces a challenge of yielding an OMC under acidic conditions because of the formation of thermoplastic resin in acidic conditions, which leads to structure collapse during carbonization. Herein, we developed an approach combined catalytic hydroxylation of phenol with assembly process to prepare OMC under acidic conditions. In our route, phenol was first partially converted into highly reactive phenols (catechol and hydroquinone) by catalytic hydroxylation, and the resulted mixture of phenols then interacted with template of Pluronic block copolymer F127 under acidic conditions to form a thermosetting mesophase through phase separation, which was carbonized to form OMC. The obtained carbon possesses ordered mesostructure with surface area of 435 m2/g, pore volume of 0.41 cm3/g and achieves high capacitance of 231 F/g for supercapacitor compared to that of normal mesoporous carbon (151 F/g) and activated carbon (AC, 119 F/g), which may be attributed to its high oxygen content resulted from catalytic hydroxylation. The developed strategy not only affords a novel approach for the synthesis of OMC but also provides a way to introduce pseudocapacitive oxygen on ordered mesoporous carbon.

Synthesis of activated carbon nanospheres with hierarchical porous structure for high volumetric performance supercapacitors

Activated carbon nanospheres (ACNS) with hierarchical porosity have been synthesized via a low-concentration hydrothermal reaction with phenolic resin as a carbon source and block copolymer F127 as a soft template, followed by subsequent KOH activation. As-obtained ACNS material integrates several advantages, such as a nanoscale particle size, a hierarchical porosity, abundant oxygen-containing functional groups and a high mass density (0.81gcm−3). The electrochemical tests in KOH aqueous electrolyte shows superior capacitive performances, i.e. both high gravimetric and volumetric capacitance of 243Fg−1 and 198Fcm−3, a large areal capacitance of 25.5μFcm−2, an excellent rate capability as well as a superior long-term cycling stability (96.1% capacitance retention over 10000 cycles). Moreover, symmetric supercapacitors based on ACNS electrodes achieve a high volumetric energy density of 6.0WhL−1, which maintains 3.7WhL−1 even at a high power density of 6.6kWL−1. Such ACNS thus shows great potential as a promising porous carbon material for high volumetric performance supercapacitors.

Dual-functional c(RGDyK)-decorated Pluronic micelles designed for antiangiogenesis and the treatment of drug-resistant tumor.

Dual-functional drug delivery system was developed by decorating c(RGDyK) (cyclic RGD [arginine-glycine-aspartic acid] peptide) with Pluronic polymeric micelles (c[RGDyK]-FP-DP) to overcome the drawbacks of low transport of chemotherapeutics across the blood–tumor barrier and poor multidrug-resistant (MDR) tumor therapy. c(RGDyK) that can bind to the integrin protein richly expressed at the site of tumor vascular endothelial cells and tumor cells with high affinity and specificity was conjugated to the N-hydroxysuccinimide-activated PEO terminus of the Pluronic F127 block copolymer. In this study, decreased tumor angiogenic and increased apoptotic activity in MDR cancer cells were observed after the treatment with c(RGDyK)-FP-DP. c(RGDyK)-FP-DP was fully characterized in terms of morphology, particle size, zeta potential, and drug release. Importantly, in vitro antiangiogenesis results demonstrated that c(RGDyK)-FP-DP had a significant inhibition effect on the tubular formation of human umbilical vein endothelial cells and promoted cellular apoptotic activity in MDR KBv cells. In addition, the growth inhibition efficacy of KBv tumor spheroids after crossing the blood–tumor barrier was obviously increased by c(RGDyK)-FP-DP compared to other control groups. Results suggested that c(RGDyK)-decorated Pluronic polymeric micelles can take pharmacological action on both human umbilical vein endothelial cells and KBv MDR cancer cells, resulting in a dual-functional anticancer effect similar to that observed in our in vitro cellular studies.

Effects of Precursor Solution Aging and Other Parameters on Synthesis of Ordered Mesoporous Titania Powders

Evaporation-induced self-assembly (EISA) of ordered mesoporous titania powders using block copolymer templates Brij 58 and F127 has been studied as a function of the precursor solution composition and age as well as the evaporation conditions. Small-angle X-ray scattering was used to monitor the degree of order in the mesoporous structure of materials synthesized under these varying conditions. Also, for the first time, the time-dependent formation of Ti structures in precursor solutions and the effect of those structures on the creation of mesostructural order have been demonstrated. The interactions of the Ti precursor with Brij 58 and F127 were investigated and showed that the different templates caused formation of Ti oligomers of unique sizes and structures. Precursor solution composition and evaporation conditions were also shown to affect the order and stability of the mesoporous titania produced. Overall, this systematic study has provided fundamental insights into the synthesis conditions that maximize the degree of order and thermal stability of the final materials. These “optimal” conditions are highly dependent on the choice of template. As a result of this improved understanding, the synthesis of ordered mesoporous titania powders using the block copolymer F127 as a template has been achieved without the use of stabilizing agents for the first time.

Ordered mesoporous carbon–titania composites and their enhanced photocatalytic properties

A series of ordered mesoporous titania–carbon composites was synthesized by self-assembly of carbon and titania precursors in the presence of Pluronic F127 block copolymer as a template under acidic conditions. Resorcinol and formaldehyde were used as carbon precursors and titanium isopropoxide was employed as titania precursor. Pluronic F127 [poly(ethylene oxide) – poly(propylene oxide) – poly(ethylene oxide) triblock copolymer] was employed as a soft template. The controlled polymerization of phenolic resin precursors and condensation of titania precursor in hydrophilic domains of the block copolymer template followed by carbonization resulted in ordered mesoporous titania–carbon composites. These composites possessed uniform ordered cylindrical mesopores (7–8nm) created by thermal decomposition of the soft template, crystalline titania particles (anatase phase, 7–8nm) embedded in the carbon matrix, and high percentage of titania (up to 48%). N2 adsorption analysis showed that the aforementioned composites exhibited large surface area (close to reaching 600m2/g) and enhanced photocatalytic activity toward photodegradation of rhodomine B due to the presence of titania nanoparticles uniformly dispersed in the carbon mesostructure.

Effect of Pluronic block copolymers on aqueous dispersions of graphene oxide

The effect of Pluronic block copolymers F127 and P123 on aqueous dispersions of graphene oxide (GO) was studied.

Rod-shaped hydroxyapatite with mesoporous structure as drug carriers for proteins

Rod-shaped hydroxyapatite (HAp) with mesoporous structure was synthesized by a hydrothermal method using Pluronic block co-polymer F127 as the template. The rod-shaped HAp was then tested as protein drug carriers by investigating their protein adsorption/release properties. Bovine serum albumin (BSA) and lysozyme (LSZ) were used as the model drugs. Various instrumental methods were used to characterize the structure, morphology, texture and protein drug adsorption/release properties of the samples. The amounts of BSA or LSZ adsorbed onto the rod-shaped HAp and their release profiles were evaluated in a simulated body fluid (SBF). The synthesized rod-shaped HAp had irregular mesostructures with lengths of 75–125nm and diameters of about 25nm. The rod-shaped HAp exhibited a higher loading capacity for BSA than for LSZ in the SBF. This adsorption behavior can be explained by the morphology of the rod-shaped HAp, which grew along the c-axis, leading to an a(b)-plane area that is larger than the c-plane area. Consequently, the number of positive charges on the surface of the rod-shaped HAp increased relative to the number of negative charges. The BSA release rate in SBF was slower than that of LSZ which is a result of the HAp surface properties.

Role of Pluronic F127 micelles in enhancing ocular delivery of ciprofloxacin

In this study, Pluronic F127 micellar systems have been utilized to enhance ocular delivery of ciprofloxacin (CPX) antibiotic. Critical micelle concentration of the Pluronic F127 block copolymer had been determined in isotonic phosphate buffer at pH7.4 and in simulated lacrimal fluid (SLF) at 25 and 34°C. Micellar systems of Pluronic F127 have been accordingly used to improve CPX solubility in isotonic phosphate buffer solution at different pH. In vitro release rate of CPX from micellar systems was investigated in SLF. Ocular delivery of selected CPX micellar formulations has been investigated and compared with that of commercially available CPX eye drops (Ciprocin®) in rabbit's eye. Pharmacokinetic parameters such as Cmax, Tmax, elimination rate constant, t1/2, MRT and AUC0−∞ were determined. The results of this study showed that, Pluronic F127 micellar systems have been shown to significantly improve CPX solubility in isotonic phosphate buffer solution at different pH. The viscosity of these systems was low indicating the formation of aqueous eye drops. Also, in vitro release rate of CPX was significantly higher from Pluronic F127 system prepared at pH4.5 and 6 than that at pH7. The investigated micellar formulations showed a significant improvement in ocular delivery of CPX compared with that of commercial CPX eye drops.

Temperature responsive 3D structure of rod-like bionanoparticles induced by depletion interaction

Herein, we show that rod-like tobacco mosaic virus (TMV) can self-assemble into 3D bundled structures in aqueous solution using azobenzene modified Pluronics F127 block copolymers (Azo-F127) to induce depletion. The structures are characterized by both transmission electron microscopy and dynamic light scattering. The self-assembly process can be controlled reversibly by temperature. The formation of Azo-F127 hard spheres during the self-assembly is the main cause of this phenomenon.

Preparation of silica nanoflakes with spherical mesopores using a dual-templating approach

A pair of chiral low-molecular-weight amphiphiles (LMWAs) was synthesized from phenylglycine, which forms a viscous solution in water. Mesoporous silica nanoflakes were prepared via a dual-templating approach using F127 block copolymer and the LMWAs. The morphologies and pore architectures of the silica nanoflakes were studied using transmission electron microscopy, field-emission scanning electron microscopy, powder X-ray diffraction, and N2 sorptions. The spherical mesopores opened onto the surfaces of the nanoflakes and were organized in a two-dimensional, hexagonal-like structure. We believe that the pore architectures and morphologies were controlled by the F127 block copolymer and the self-assembly of the LMWAs, respectively. This kind of material has potential for applications in separation and catalysis.

Optimizing the synthesis of CdS/ZnS core/shell semiconductor nanocrystals for bioimaging applications.

In this study, we report on CdS/ZnS nanocrystals as a luminescence probe for bioimaging applications. CdS nanocrystals capped with a ZnS shell had enhanced luminescence intensity, stronger stability and exhibited a longer lifetime compared to uncapped CdS. The CdS/ZnS nanocrystals were stabilized in Pluronic F127 block copolymer micelles, offering an optically and colloidally stable contrast agents for in vitro and in vivo imaging. Photostability test exhibited that the ZnS protective shell not only enhances the brightness of the QDs but also improves their stability in a biological environment. An in-vivo imaging study showed that F127-CdS/ZnS micelles had strong luminescence. These results suggest that these nanoparticles have significant advantages for bioimaging applications and may offer a new direction for the early detection of cancer in humans.

Formation of Subnanometer Zr-WOx Clusters within Mesoporous W–Zr Mixed Oxides as Strong Solid Acid Catalysts for Friedel–Crafts Alkylation

WO3-ZrO2 mixed metal oxides is an important class of acid solid. Here, we successfully synthesized a variety of mesoporous WO3-ZrO2 mixed metal oxides by a well-controlled sol-gel process (AcHE) using Zr(OBu)(4) and WCl6 as the inorganic precursors in the presence of poly block copolymer F127. Their structures and acid properties have been well characterized by XRD, Raman, N-2 adsorption measurement, and HRTEM analyses. In addition, new insights from TG-DSC and P-31 NMR characterization also provide useful information on the formation of strong acidity of this important solid acid. Moreover, their structure-to-properties relationship has been studied in the Friedel-Crafts (F-C) reaction of anisole and benzyl alcohol. We identified that the subnanometer WOx clusters act as the most active sites for the F-C reaction. Most importantly, we show that the formation of these subnanometer WOx clusters can be rationally controlled. It is shown that a minimum W concentration (0.07 at the calcination temperature of 800 degrees C) and a minimum calcination temperature (650 degrees C at a given W concentration of 0.1) are required during the preparation of these acid catalysts for the development of highly active subnano WOx clusters.

Structural characterization and adsorption properties of pluronic F127 onto iron oxides magnetic nanoparticles.

Superparamagnetic iron oxide nanoparticles coated with polymers have shown low toxicity and chemical stability in physiological condition, thereby can be used to deliver encapsulated drugs throughout the body by external magnetic fields. In this study, magnetic nanoparticles were synthesized thorough co-precipitation method and their interaction with Pluronic F127 block copolymer as well as adsorption properties of polymer onto nanoparticles were investigated. Adsorption measurement revealed different adsorption behaviors below and above the polymer's critical micelle concentration. The Freundlich isotherm was found to better describe the adsorption behavior of Pluronic F127 onto SIONPs particles below the block copolymer critical micelle concentration. At higher concentration, the adsorbed amount is likely to diminish due to interpenetration of the adsorbed macromolecular micelles and volume-excluded effects for block copolymers. Furthermore, magnetic nanocomposites with different concentration of polymers were prepared through hydrothermal method. The crystalline structure, morphology, pore structure, and magnetic properties of magnetic nanoparticles/nanocomposites products at different pH and polymer concentration were studied. Results showed that due to the hematite impurities, magnetic nanocomposites synthesized at higher pH have lower magnetization.

Formation of hexagonal and cubic fluorescent periodic mesoporous organosilicas in the channels of anodic alumina membranes

The synthesis of periodic mesoporous organosilicas (PMOs) in the confinement of porous anodic alumina membranes (AAMs) was successfully achieved through a modified evaporation-induced self-assembly (EISA) process. 1,3,5-Tris(4-triethoxysilylstyryl)benzene, (a three-armed oligo(phenylenevinylene) organosilane compound, abbr. 3a-OPV), the precursor of the first reported charge-conducting PMO, was used as an organosilica source. Triblock-copolymers Pluronic F127 (EO106 PO70 EO106) or F108 (EO132 PO50 EO132) were used as structure directing agents. The block-copolymer F127 led to a 2D-hexagonal circular mesostructure within the AAM channels and the block copolymer Pluronic F108 resulted in a mesophase with a body-centered cubic (Imm) structure. Compared to the previously reported 3a-OPV-PMO film, the resulting hierarchical PMO/AAM systems have improved features, that is, the synthesized PMOs have a pore size of around 10 nm and the compounds are found to be stable against thermal treatment at temperatures of up to 200 °C and they are also stable in the electron beam of the electron microscope. Additionally, both of the resulting hierarchical mesoporous composites show fluorescence in the visible region due to the strongly interacting phenylenevinylene chromophores in the PMO frameworks.

Photogeneration of Silver Nanoparticle Facilitated by Pluronic F127 Surfactant in Ethanolic Solution

In the present study, the photo-generation of silver nanoparticles in ethanolic solution and in the presence of F127 block copolymer using UV irradiation have been investigated. The aim of the present study is preparing the green, facile and much faster method than previous studies. The kinetics of silver nanoparticles formation has been investigated by using UV-vis spectroscopy. The two-dimensioanl map technique has been used to estimate the switching time between the nucleation and growth of Ag nanoparticles. The results show that the dispersed Ag nanoparticle in ethanol can be formed by high intensity ultraviolet exposure within few minutes.