Simple Micelles Research Articles

Integrating Single-Walled Carbon Nanotubes into Supramolecular Assemblies: From Basic Interactions to Emerging Applications.

Integrating single-walled carbon nanotubes (SWCNTs) into supramolecular self-assemblies harnesses the distinctive mechanical, optical, and electronic properties of the nanoparticles alongside the structural and chemical properties of the assemblies. Organic molecules capable of forming supramolecular assemblies through hydrophobic, van der Waals, and π-π interactions have been demonstrated to be particularly effective in dispersing and functionalizing SWCNTs, as these same interactions facilitate the binding to the hydrophobic graphene-like surface of the SWCNTs. This review discusses a variety of self-assembling structures that were shown to integrate SWCNTs, ranging from simple micelles and ring structures to complex DNA origami and three-dimensional hydrogels formed by low-molecular-weight gelators. We explore the integration of SWCNTs into various supramolecular assemblies and highlight emerging applications of these composite materials, such as the mechanical enforcement of self-assembling hydrogels and leveraging the near-infrared (NIR) fluorescence properties of SWCNTs for monitoring the molecular self-assembly process. Notably, the distinctive NIR fluorescence of SWCNTs, which overlaps with the biological transparency window, offers significant opportunities for noninvasive sensing applications within the supramolecular platforms. Future research into a deeper understanding of the interactions between SWCNTs and different supramolecular frameworks will expand the potential applications of SWCNT-integrated supramolecular assemblies in fields like biomedical engineering, electronic devices, and environmental sensing.

Design of polymeric carriers to enhance antimicrobial photodynamic inactivation

Mixed polymeric micelles are a promising tool for the design of nanocarriers with pharmaceutical properties. These micellar systems allow reversing numerous properties of lipophilic drugs. Particularly, when applied to transport photosensitizers (PSs), they give rise to a wide variety of nanophotosensitizers (nPSs). These compounds are used to inactivate numerous bacteria resistant to conventional antibiotics. This research proposes the development of new mixed micelles, with better properties than simple micelles, for the trapping of Neutral Red (NR) and its monobrominated derivative (NRBr). Based on the combination of Pluronic P-123 with Pluronic F-108, Pluronic L-61 and Tween 80, 15 binary micellar systems were obtained. These mixed micelles presented a single population of homogeneous particles, with a diameter less than 70 nm. Moreover, several mixed micelles show smaller CMC than the simple system. These properties are predictors of high micellar stability and good anti-dilution properties, favoring their drug delivery applications. For these reasons, were loaded with NR and NRBr, showing good encapsulation efficiency. The 30 new nPSs presented an adequate size for pharmaceutical use and markedly enhanced the photochemical reactivity of the free PSs. Many of the mixed micellar systems showed greater production of singlet oxygen than the simple micelles of Pluronic P-123. Furthermore, all micellar systems increased the chemical stability of NRBr, which degrades in pH 7.4 buffer solution. Finally, all nPSs presented greater phototoxic activity against methicillin-resistant Staphylococcus aureus than free PSs. The nPSs formed by P-123: F-108 (90:10) + NR, P-123: F-108 (90:10) + NRBr, P-123: L-61 (80:20) + NRBr and P −123: T80 (80:20) + NRBr caused greater photodynamic inactivation of the microorganism than simple P-123 micellar systems. These nPSs could be considered excellent candidates for application in the treatment of infections caused by bacteria resistant to antibiotics.

Tumor pH-Responsive Nanocarriers With Light-Activatable Drug Release for Chemo-Photodynamic Therapy of Breast Cancer.

Developing bioresponsive nanocarriers with particular tumor cell targeting and on-demand payload release has remained a great challenge for combined chemo-photodynamic therapy (chemo-PDT). In this study, an intelligent nanocarrier (DATAT-NPCe6) responded to hierarchical endogenous tumor pH, and an exogenous red light was developed through a simple mixed micelle approach. The outside TAT ligand was masked to prevent an unexpected interaction in blood circulation. Following the accumulation of DATAT-NPCe6 in tumor tissues, tumor acidity at pH ∼6.5 recovered its targeting ability via triggering DA moiety degradation. Furthermore, the cascaded chemo-PDT was accomplished through light-stimulated nanocarrier disassembly and doxorubicin (DOX) release. Taking advantage of stability and controllability, this work provides a facile approach to designing bioresponsive nanocarriers and represents a proof-of-concept combinatorial chemo-PDT treatment.

Does Stochasticity Favour Complexity in a Prebiotic Peptide-Micelle System?

A primordial environment that hosted complex pre- or proto-biochemical activity would have been subject to random fluctuations. A relevant question is then: What might be the optimum variance of such fluctuations, such that net progress could be made towards a living system? Since lipid-based membrane encapsulation was undoubtedly a key step in chemical evolution, we used a peptide-micelle system in simulated experiments where simple micelles and peptide-stabilized micelles compete for the same amphiphilic lipid substrate. As cyclic thermal driver and energy source we used a thermochemical redox oscillator, to which the micelle reactions are coupled thermally through the activation energies. The long-time series averages taken for increasing values of the fluctuation variance show two distinct minima for simple micelles, but are smoothly increasing for complex micelles. This result suggests that the fluctuation variance is an important parameter in developing and perpetuating complexity. We hypothesize that such an environment may be self-selecting for a complex, evolving chemical system to outcompete simple or parasitic molecular structures.

Glucose-responsive complex micelles for self-regulated delivery of insulin with effective protection of insulin and enhanced hypoglycemic activity in vivo

Large amounts of insulin-loaded glucose-responsive micelles based on poly(amino acid)s have been developed for diabetes treatment over last decades, but most of them could not effectively protect insulin from enzymatic degradation in vivo because the micellar core was biodegradable and lacked protective structure for insulin, which would lower the efficacy of insulin to a large extent. In this study, we fabricated a new type of insulin-loaded glucose-responsive complex micelles (CMs), which were self-assembled by a phenylboronic acid (PBA)-modified block copolymer PEG-b-P(Asp-co-AspPBA) and a glucosamine (GA)/nitrilotriacetic acid (NTA)-functionalized block copolymer PNIPAM-b-P(Asp-co-AspGA-co-AspNTA), for self-regulated delivery of insulin with effective protection of insulin and enhanced hypoglycemic activity in vivo. The CMs possessed mixed shell of PEG/PNIPAM and cross-linked core of PBA/GA complex, which could be disintegrated under the condition of high glucose concentration (5 g/L) while maintaining stable at low glucose concentration (1 g/L). The NTA groups of CMs greatly improved the loading content of insulin by specifically bind insulin via the chelated zinc ions. More importantly, PNIPAM chains in the mixed shell would collapse under 37 °C and form hydrophobic domains around the micellar core, which could significantly protect the micellar core as well as the encapsulated insulin from attacking by external proteases. In a murine model of type 1 diabetes, the CMs with insulin chelated by NTA showed a long hypoglycemic effect, which is superior to insulin-loaded simple micelles without PNIPAM and insulin in PBS buffer (pH 7.4). Therefore, this kind of CMs could be a potential candidate for insulin delivery in diabetes therapy.

Molecular Mechanisms for Protection of Hepatocytes against Bile Salt Cytotoxicity.

Biliary lipids consist mainly of bile salts, phospholipids and cholesterol, which form mixed micelles and vesicles. Bile salts play various physiological roles but have damaging effects on cell membranes due to their detergent properties. The cytotoxicity of bile salts on hepatocytes leads to liver injuries and is largely determined by the bile salt species, the concentrations of bile salts, phospholipids and cholesterol, and the lipid composition of cell membranes. In bile, monomers and simple micelles of bile salts coexist with mixed micelles and vesicles in dynamic equilibrium, and contribute to the cytotoxicity on hepatocytes. The ATP-binding cassette (ABC) transporter family members, ABCB11, ABCB4 and ABCG5/ABCG8, mediate the biliary secretion of bile salts, phospholipids and cholesterol, respectively. Mutations in ABCB4 result in severe cholestatic diseases, and the biliary phospholipids are necessary for the attenuation of bile salt cytotoxicity. On the other hand, cholesterol reverses the cytoprotective effects of phospholipids against bile salts. In addition, phosphatidylethanolamine N-methyltransferase increases the cell resistance to bile salts by changing the phospholipid composition and structures of the apical membranes. In this review, we focus on the molecular mechanisms for the protection of hepatocytes against bile salt cytotoxicity. Further understanding of these mechanisms will help to develop new therapeutic strategies for cholestatic liver diseases.

Novel Endothelial Cell Targeted Peptide Nanoformulation for Inhibiting von Willebrand Factor Secretion to Reduce Thrombotic Complications in Sepsis

RationaleMicrovascular thrombosis and disseminated intravascular coagulation (DIC) are primary determinants of ischemia, organ failure and mortality/morbidity in sepsis. Interestingly, elevated plasma level of von Willebrand factor (vWF), the glue to which platelets adhere to form a clot, is associated with reduced survival and poor outcome in septic patients. Previously, we demonstrated that endothelial cell (EC) Gα12 is required for soluble N‐ethylmaleimide‐sensitive‐fusion factor attachment protein α (αSNAP)‐dependent vWF secretion from Weibel Palade bodies. Here, we report that sterically stabilized simple micelles (SSM) containing cell‐permeable myristoylated αSNAP binding domain (Myr‐SBD) peptide based on the unique N‐terminal Gα12 sequence that binds to αSNAP, inhibits vWF secretion.MethodsStructural complex of αSNAP/SBD was determined by blind‐ and data‐driven docking using AutoDock and HADDOCK, respectively. After incorporating Myr‐SBD into SSM (Myr‐SBD‐SSM) by film hydration method, micelle size and shape were confirmed by dynamic light scattering and transmission electron microscopy (TEM), respectively. Intracellular delivery of Myr‐SBD‐SSM was evaluated by fluorescence microscopy and fluorometry in cultured ECs. Cecal ligation and puncture (CLP) in C57BL/6 mice (14–16 wks, 25 g) was used to induce severe inflammation, microvascular thrombosis and DIC, and blood was collected 6 h and 24 h post CLP. The effect of Myr‐SBD‐SSM on plasma vWF, platelet count and inflammatory cytokines was assessed following addition of 0, 2 or 4 μmol Myr‐SBD/kg given i.v. at the time of surgery. Bleeding was assessed by tail‐snip assay. Glomerular fibrin deposition was scored by IHC analysis at 24 h post CLP.ResultsThe αSNAP/SBD structure showed the potential interaction between Arg of SBD peptide and Glu139 of αSNAP by H‐bond. Spherical shape of Myr‐SBD‐SSM (14.1 ± 2.7 nm in diameter) was confirmed by negative staining TEM. Addition of Myr‐SBD‐SSM to ECs resulted in the intracellular accumulation of Myr‐SBD which blocked thrombin‐induced vWF secretion. Intravenous delivery of Myr‐SBD‐SSM to mice at the time of CLP blunted the increase in plasma vWF and associated microvascular thrombosis in the kidney glomerulus. Importantly, Myr‐SBD‐SSM treatment resulted in increased platelet and WBC counts 6 h after surgery and improved survival compared to untreated or scrambled peptide treated mice with severe vascular inflammation suggesting Myr‐SBD‐SSM reduced clotting, platelet consumption and systemic inflammation in intraperitoneal sepsis. Moreover, Myr‐SBD‐SSM treatment did not increase tail‐snip bleeding time suggesting it did not prevent hemostasis.ConclusionOur studies demonstrate that Myr‐SBD‐SSM nanoformulation reduces vWF secretion and attenuates the thrombotic complications of severe inflammation.Support or Funding InformationThis work was supported by MPI R01 HL125356 (RDM, XD), Michael Reese Research and Education Foundation (RDM) and American Heart Association (MB, LR).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Porphyrin-Based Nanomaterials: Enhanced Electrochemiluminescence and the Application of Bioassay

Electrochemiluminescence (ECL) has become a powerful analytical tool and has been widely applied in many fields. However, ECL still has shortcomings like poor ability to repeatedly electrochemically cycle an individual luminophore, a broad emission spectroscopy, and signal loss due to ECL reagents leaving the detection zone. Therefore, further improvement of ECL signal is still of significance. Nanomaterials can be incorporated into ECL sensor to improve efficiency, but also represent a new class of ECL emitters. Porphyrins are 18p aromatic azaannulenes consisting of regularly arranged four methine carbons. Electrochemical and photochemical properties of porphyrins have attracted much attention for decades because of their unique aromatic structure and their beneficial characteristics such as high molar absorptivity, as well as the vital roles in biological processes such as photosynthesis, oxygen transport, and biocatalysis. Porphyrins have a flexible and adjustable molecular structure in chemical modification. The introduction of molecular-recognition motifs (e.g., hydrogen bonding, metal-ligand bonds andp-pstacking) into the porphyrin building blocks will make them form new structures, such as fibers, cubes, sheets, simple micelles and wheels. In our work, we have developed several enhanced ECL sensors based on porphyrin-nanocomposite. For example, we synthesized zirconium-based porphyrinic metal−organic framework (MOF) for the detection of a phosphoprotein. The active center ZnTCPP in MOF-525-Zn as electron media reacts with O2 in the 3D nanocage to produce 1O2, resulting in enhanced ECL signal. Figure 1

Micelle System Based on Molecular Economy Principle for Overcoming Multidrug Resistance and Inhibiting Metastasis.

The high mortality of cancer is mainly attributed to multidrug resistance (MDR) and metastasis. A simple micelle system was constructed here to codeliver doxorubicin (DOX), adjudin (ADD), and nitric oxide (NO) for overcoming MDR and inhibiting metastasis. It was devised based on the "molecular economy" principle as the micelle system was easy to fabricate and exhibited high drug loading efficiency, and importantly, each component of the micelles would exert one or more active functions. DOX acted as the main cell killing agent supplemented with ADD, NO, and d-α-tocopheryl polyethylene glycol 1000 succinate (TPGS). MDR was overcome by synergistic effects of mitochondria inhibition agents, TPGS and ADD. A TPGS-based NO donor can be used as a drug carrier, and it can release NO to enhance drug accumulation and penetration in tumor, resulting in a positive cycle of drug delivery. This DOX-ADD conjugate self-assembly system demonstrated controlled drug release, increased cellular uptake and cytotoxicity, enhanced accumulation at tumor site, and improved in vivo metastasis inhibition of breast cancer. The micelles can fully take advantage of the functions of each component, and they provide a potential strategy for nanomedicine design and clinical cancer treatment.

Structural control of the hybrid colloids by cooperative assembly of PS-b-PAA and semiconductor nanoparticles from the solvent aspects

Well-defined polymer/inorganic nanoparticle (NP) hybrids are of vital importance to the development of nanomaterials with desired optical, electric, magnetic, and many other properties. We demonstrate the efficient incorporation of n-trioctylphosphine oxide (TOPO)-coated CdSe quantum dots (QDs) into polystyrene-b-polyacrylic acid (PS-b-PAA) colloids by a “solution phase self-assembly” approach. Driven by the hydrophobic interactions, the CdSe QDs are homogeneously encapsulated in the hybrid colloids. The sizes of the hybrid colloids with different structures, i.e., simple spherical micelles and big compound micelles, are tuned from 45 to 126 nm by varying the THF content in the cosolvents of THF and DMF, as well as changing the content or addition rate of selective solvent (water). The PS-b-PAA@CdSe QD hybrid colloids, which show brightly green fluorescence, can be endocytosed into biological cells and be released from the cells evolutionally, indicating their potential applications in biological imaging, labeling, and sensing, among others.

Cholesterol attenuates cytoprotective effects of phosphatidylcholine against bile salts

Bile salts have potent detergent properties and damaging effects on cell membranes, leading to liver injury. However, the molecular mechanisms for the protection of hepatocytes against bile salts are not fully understood. In this study, we demonstrated that the cytotoxicity of nine human major bile salts to HepG2 cells and primary human hepatocytes was prevented by phosphatidylcholine (PC). In contrast, cholesterol had no direct cytotoxic effects but suppressed the cytoprotective effects of PC. PC reduced the cell-association of bile salt, which was reversed by cholesterol. Light scattering measurements and gel filtration chromatography revealed that cholesterol within bile salt/PC dispersions decreased mixed micelles but increased vesicles, bile salt simple micelles and monomers. These results suggest that cholesterol attenuates the cytoprotective effects of PC against bile salts by facilitating the formation of bile salt simple micelles and monomers. Therefore, biliary PC and cholesterol may play different roles in the pathogenesis of bile salt-induced liver injury.

A Model Prediction for Chenodeoxycholate Aggregate Formation

A relationship between the chenodeoxycholate (CDC) monomer concentration and the total concentration of CDC was established using a kinetic dialysis technique. Meanwhile, the sizes of the formed simple CDC micelles were measured by a quasielastic light-scattering (QLS) technique to be nearly constant. The QLS results led to a suggestion for equilibrium models of CDC aggregate formation. According to the established relationship and the suggested models, the best curve-fitting model was selected by a least-squares technique. Furthermore, the model parameters were quantified. Based on the quantified parameters, at a minimum detectable concentration of simple CDC micelles to be ∼0.2 mM, an appropriate model corresponding concentration of CDC monomers was estimated to be ∼3.08 mM. This value is consistent with a minimum monomer CDC concentration of ∼3.13 mM for simple CDC micelle formation estimated according to the present QLS detection and the model prediction. The consistency confirms the model prediction that at a low CDC monomer concentration (<3 mM), the concentration of stable CDC dimers is much higher than that of simple CDC micelles but the contribution of simple CDC micelles to the total CDC concentration cannot be negligible.

Highly Sensitive Micellar Enhanced Spectrofluorimetric Method for Determination of Mirtazapine in Tablets and Human Urine: Application to In Vitro Drug Release and Content Uniformity Test

A highly sensitive and simple micelle enhanced spectrofluorimetric method was developed for assaying mirtazapine (MRZ) in REMERON® tablets and spiked human urine directly without the need of derivatizing agent. The basis of the current procedure is the examination of the relative fluorescence intensity (RFI) of MRZ in sodium lauryl sulphate (SLS) micellar medium. The RFI of MRZ in water was enhanced markedly on addition of SLS. The RFI was measured at 403 nm after excitation at 320 nm. The fluorescence-concentration relationship was linear over the range 1–500 ng/mL, with lower detection limit of 0.399 ng/mL. The proposed method was successfully applied to the determination of MRZ in dosage form and spiked human urine. Recovery percentages of MRZ utilizing the current method were99.05±1.83,98.37±1.96, and100.41±2.61% for pure powder, pharmaceutical dosage form, and spiked human urine, respectively. The application of the proposed method was extended to test content uniformity and the in vitro drug release of REMERON tablets, according to USP guidelines.

Intranasal Administration of Antiretroviral-Loaded Micelles for Anatomical Targeting to The Brain in HIV

To investigate the intranasal administration of poly(ethylene oxide)-poly(propylene oxide) polymeric micelles loaded with high payloads of the first-line antiretroviral drug efavirenz for targeting to the CNS. The effect of micellar size and composition and drug payload was assessed, employing simple micelles made of a highly hydrophilic copolymer, poloxamer F127, loaded with 20 mg/ml drug and mixed micelles containing 75% of a poloxamine of intermediate hydrophobicity, T904, and 25% F127 loaded with 20 and 30 mg/ml drug. F127 confers high physical stability, while T904 substantially improves the encapsulation capacity of the micelles. The bioavailability of the drug in the CNS was increased fourfold and the relative exposure index (ratio between the area under the curve in the CNS and plasma) was increased fivefold with respect to the same system administered intravenously. These findings demonstrate the potential of this scalable and cost-viable strategy to address the HIV sanctuary in the CNS.

Amphiphiles in aqueous solution: well beyond a soap bubble

Owing to their "dual" affinity, amphiphiles self-assemble in water to form different kinds of nanoscale multimolecular assemblies ranging from simple micelles and vesicles to highly organized fibers, helices and tubes. In this tutorial review the aggregates formed in water by head/tail amphiphiles are revisited and discussed from the point of view of supramolecular chemistry with a focus on their structure and recognition abilities. Their applications in materials chemistry, as soft templates for inorganic nanostructures, as well as in biological and medicinal chemistry are also illustrated. Special attention is paid to highlight intriguing aspects, for example the control of morphology and chirality, their modulation by experimental parameters and chiral symmetry breaking.

Su1749 Biophysical Evidence That NSAIDs Form Mixed Micelles With Bile Acids as a Possible Mechanism of NSAID-Induced Lower Gut Injury

Background: An increasing amount of evidence suggests that consumption of non-aspirin NSAIDs is associated with injury to the lower gut in humans, as has been established in rodent model systems. NSAID-induced lower gut injury may in fact explain the linkage between NSAID consumption and the development of ileitis, diverticulitis and inflammatory bowel disease. Evidence from our and other labs indicates that NSAID-induced injury to the lower gut is dependent on the presence of bile, based upon In Vitro (synthetic membranes and GI cells in culture) and In Vivo (rodent) studies, and we have hypothesized that NSAIDs may form toxic mixed micelles with bile acids (BAs). Aim: To test this hypothesis that NSAIDs and BAs spontaneously form mixed micellar aggregates we used a combination of powerful computational and spectroscopic techniques to gain insights into atomic associations between cholic acid (CA) and ibuprofen (IBU). Methods & Results: Using Molecular Dynamics (MD) simulations in tandem with Nuclear Magnetic Resonance (NMR) spectroscopy, we found that CA and IBU form mixed micelles in a concentration dependent manner, so that multiple CA molecules form ‘pseudo-rings' into which IBUs insert their hydrophobic tails. This ‘β-face-to-tail' packing between the steroid rings of CA and the alkyl carbons of IBU promotes the hydrophobic interaction of these two classes of amphipathic molecules. We also found that the IBU-CA mixed micelles have much larger sizes and higher net surface charges than simple CA micelles, the total charge being the sum of the single negative charge arising from each of the CA and IBU molecules. Furthermore, the IBU-CA mixed micelles adopt amore spherical shape that differs from the oblate shape formed by the pure CA clusters. These results highlight the power of a combined NMR/MD approach for characterizing the molecular interactions in the binarymixtures of NSAIDs and BAs. Conclusions: Our combined NMR/MD analysis yielded compelling structural evidence that NSAIDs and BAs form mixed micelles at concentrations greater than or equal to the CMC of the two species, which likely occur in the small intestinal lumen. The significance of the altered micellar morphology and charge density of these BA/NSAID mixed micelles to the drugs' cytotoxicity to the epithelium of the lower gut is an important area for future investigation. (Supported by NIH grants RC1 DK086304 and P30 DK56338.)

Su1753 ACAP4-ezrin Interaction is Essential for Canalicular Remodeling in Histamine-Stimulated Parietal Cell Secretion

Background: An increasing amount of evidence suggests that consumption of non-aspirin NSAIDs is associated with injury to the lower gut in humans, as has been established in rodent model systems. NSAID-induced lower gut injury may in fact explain the linkage between NSAID consumption and the development of ileitis, diverticulitis and inflammatory bowel disease. Evidence from our and other labs indicates that NSAID-induced injury to the lower gut is dependent on the presence of bile, based upon In Vitro (synthetic membranes and GI cells in culture) and In Vivo (rodent) studies, and we have hypothesized that NSAIDs may form toxic mixed micelles with bile acids (BAs). Aim: To test this hypothesis that NSAIDs and BAs spontaneously form mixed micellar aggregates we used a combination of powerful computational and spectroscopic techniques to gain insights into atomic associations between cholic acid (CA) and ibuprofen (IBU). Methods & Results: Using Molecular Dynamics (MD) simulations in tandem with Nuclear Magnetic Resonance (NMR) spectroscopy, we found that CA and IBU form mixed micelles in a concentration dependent manner, so that multiple CA molecules form ‘pseudo-rings' into which IBUs insert their hydrophobic tails. This ‘β-face-to-tail' packing between the steroid rings of CA and the alkyl carbons of IBU promotes the hydrophobic interaction of these two classes of amphipathic molecules. We also found that the IBU-CA mixed micelles have much larger sizes and higher net surface charges than simple CA micelles, the total charge being the sum of the single negative charge arising from each of the CA and IBU molecules. Furthermore, the IBU-CA mixed micelles adopt amore spherical shape that differs from the oblate shape formed by the pure CA clusters. These results highlight the power of a combined NMR/MD approach for characterizing the molecular interactions in the binarymixtures of NSAIDs and BAs. Conclusions: Our combined NMR/MD analysis yielded compelling structural evidence that NSAIDs and BAs form mixed micelles at concentrations greater than or equal to the CMC of the two species, which likely occur in the small intestinal lumen. The significance of the altered micellar morphology and charge density of these BA/NSAID mixed micelles to the drugs' cytotoxicity to the epithelium of the lower gut is an important area for future investigation. (Supported by NIH grants RC1 DK086304 and P30 DK56338.)

Calorimetric study on the solubilization of butanol by alkylphosphate and alkylphosphate-lecithin systems.

Microcalorimetric studies on alkylphosphate-butanol and alkylphosphate-butanol-lecithin systems were carried out as a first step to study the role of butanol (used as cosurfactant) in the formation of microemulsions. The enthalpy of solubilization; delta H, of the same amount of butanol (1.806 mol kg-1) in aqueous sodium monoalkyl-phosphates, with a hydrocarbon chain varying from 6 to 10 carbon atoms, was investigated as a function of alkylphosphate concentration. Measurements were performed in the presence and in the absence of lecithin. The enthalpy values measured upon addition of butanol to the mixtures were negative in all cases. Below the critical micelle concentration (CMC) of the alkylphosphates, the heats of butanol dissolution were found to decrease upon increasing the concentration of the alkylphosphate. This behaviour was related to the dissolution of butanol in water and to the formation of mixed butanol-alkylphosphate and butanol-alkylphosphate-lecithin micelles. Above the CMC essentially constant delta H values were found. The delta H measured may be the sum of simultaneous effects--heat of alcohol dissolution and the simple alkylphosphate micelle dissociation or alkylphosphate-lecithin mixed aggregate dissociation and the heat of mixed micelle formation. The delta H at the plateaus were linearly related to the corresponding CMC values of the alkylphosphates.

Synthesis of polypyrrole nanoparticles and its grafting with silica gel for selective binding of chromium(VI)

Polypyrrole nanoparticles of desired structure have been synthesized through simple micelle technique. It is then grafted with functionalized silica gel to develop a novel organic–inorganic hybrid material. The role of dimethyl dichloro silane (coupling agent) in grafting is demonstrated. The nanoparticles are characterized by TEM, SEM and TGA. Grafting reactions are evaluated by spectral (FTIR) analysis and chemical test. The Cr(VI) binding behavior of the composite is studied in various pH of the medium. The selectivity in binding Cr(VI) is monitored. The metal ion adsorption capacity and surface area of the material are found to be 38mg/g and 235m2/g, respectively.

Synthesis of polyaniline nanoparticle grafted silica gel and study of its Cr(VI) binding property

AbstractPolyaniline nanoparticles have been synthesized through simple micelle technique and then grafted it with silanized silica gel to develop a novel hybrid material. The nanoparticles are characterized by UV‐Vis, TEM, CV, SEM, TGA, DTG, and DSC. Silanization and grafting reactions are evaluated by FTIR and chemical test. The Cr(VI) binding behavior of the composite is studied in various pH of the medium, and both competitive and noncompetitive conditions. The particle size, adsorption capacity, and surface area of the material are found to be 100 nm, 135 mg/g, and 720 m2/g, respectively. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011