Microemulsion Template Research Articles

Catalytically Active Pd-Ag Alloy Nanoparticles Synthesized in Microemulsion Template.

This work investigates the possibility to form catalytically active bimetallic Pd-Ag nanoparticles synthesized in the water pools of a reversed microemulsion using methanol, a more environmental- and user-friendly reductant compared to hydrazine or sodium borohydride, which are commonly used for this type of synthesis. The nanoparticles were characterized with regards to crystallinity and size by X-ray diffraction and transmission electron microscopy. CO chemisorption and oxidation followed by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was used for investigating the elemental composition of the surface and catalytic activity, respectively. Moreover, the structural composition of the bimetallic particles was determined by scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy. The particles were shown to be crystalline nanoalloys of around 5-12 nm. CO adsorption followed by in situ DRIFTS suggests that the particle surfaces are composed of the same Pd-Ag ratios as the entire particles, regardless of elemental ratio (i.e., no core-shell structures can be detected). This is also shown by numerical simulations using a Monte Carlo based model. Furthermore, CO oxidation confirms that the synthesized particles are catalytically active.

Gold Nanorods Conjugated Porous Silicon Nanoparticles Encapsulated in Calcium Alginate Nano Hydrogels Using Microemulsion Templates

Porous silicon nanoparticles (PSiNPs) and gold nanorods (AuNRs) can be used as biocompatible nanocarriers for delivery of therapeutics but undesired leakage makes them inefficient. By encapsulating the PSiNPs and AuNRs in a hydrogel shell, we create a biocompatible functional nanocarrier that enables sustained release of therapeutics. Here, we report the fabrication of AuNRs-conjugated PSi nanoparticles (AuNRsPSiNPs) through two-step chemical reaction for high-capacity loading of hydrophobic and hydrophilic therapeutics with photothermal property. Furthermore, using water-in-oil microemulsion templates, we encapsulate the AuNRsPSiNPs within a calcium alginate hydrogel nanoshell, creating a versatile biocompatible nanocarrier to codeliver therapeutics for biomedical applications. We find that the functionalized nanohydrogel effectively controls the release rate of the therapeutics while maintaining a high loading efficiency and tunable loading ratios. Notably, combinations of therapeutics coloaded in the functionalized nanohydrogels significantly enhance inhibition of multidrug resistance through synergism and promote faster cancer cell death when combined with photothermal therapy. Moreover, the AuNRs can mediate the conversion of near-infrared laser radiation into heat, increasing the release of therapeutics as well as thermally inducing cell damage to promote faster cancer cell death. Our AuNRsPSiNPs functionalized calcium alginate nanohydrogel holds great promise for photothermal combination therapy and other advanced biomedical applications.

No Catalyst Dye Photodegradation in a Microemulsion Template

This paper proposes an innovative solution for the efficient dye degradation from water treatment plant effluent, using microemulsion assisted photodegradation without the addition of a solid catalyst. Total photodegradation of dyes was achieved using for the first time a process based on combined photocatalytic effects of the water/oil interface processes and the potential activity of ethyl acetate as a UV initiator. The catalytic effect of nanostructured fluids based on the carboxylic oil phase is an absolute scientific premiere, and microemulsion assisted photodegradation processes open a new direction to pollutants photodegradation approach, exceeding the performances of both homogeneous and heterogeneous catalysis. The phenomenological modeling, with and without initiator, on both homogeneous and heterogeneous systems showed that the photodegradation of cationic and anionic dyes in a water/nonionic surfactant/ethyl acetate microemulsion is a radical process based on a chain reaction scheme. The compl...

Nanostructured lipid carriers of artemether–lumefantrine combination for intravenous therapy of cerebral malaria

Patients with cerebral malaria (CM) are unable to take oral medication due to impaired consciousness and vomiting thus necessitating parenteral therapy. Quinine, artemether, and artesunate which are currently used for parenteral malaria therapy have their own drawbacks. The World Health Organization (WHO) has now banned monotherapy and recommends artemisinin-based combination therapy for malaria treatment. However, presently there is no intravenous formulation available for combination therapy of malaria. Artemether–Lumefantrine (ARM–LFN) is a WHO approved combination for oral malaria therapy. However, the low aqueous solubility of ARM and LFN hinders their intravenous delivery. The objective of this study was to formulate ARM–LFN nanostructured lipid carriers (NLC) for intravenous therapy of CM. ARM–LFN NLC were prepared by microemulsion template technique and characterized for size, drug content, entrapment efficiency, drug release, crystallinity, morphology, amenability to autoclaving, compatibility with infusion fluids, stability, antimalarial efficacy in mice, and toxicity in rats. The ARM–LFN NLC showed sustained drug release, amenability to autoclaving, compatibility with infusion fluids, good stability, complete parasite clearance and reversal of CM symptoms with 100% survival in Plasmodium berghei-infected mice, and safety in rats. The biocompatible ARM–LFN NLC fabricated by an industrially feasible technique offer a promising solution for intravenous therapy of CM.

Artemether⿿lumefantrine nanostructured lipid carriers for oral malaria therapy: Enhanced efficacy at reduced dose and dosing frequency

Artemether⿿lumefantrine (ARM⿿LFN) is a World Health Organization (WHO) approved fixed-dose combination having low solubility and poor oral bioavailability. Nanostructured lipid carriers (NLC) were developed to enhance the oral efficacy of this combination using the microemulsion template technique. They were characterized for drug content, entrapment efficiency, size distribution, in vitro release, antimalarial efficacy, and toxicity. The NLC showed sustained drug release. The recommended adult therapeutic dose is 80mg ARM and 480mg LFN (4 tablets) twice a day, which amounts to 160mg ARM and 960mg LFN daily. ARM⿿LFN NLC given once a day at 1/5 of therapeutic dose (16mg ARM and 96mg LFN) showed complete parasite clearance and 100% survival in Plasmodium berghei-infected mice. 33% of the mice treated with marketed tablets twice a day at the therapeutic dose showed late-stage recrudescence. Thus, NLC showed enhanced efficacy at 1/10 of the daily dose of ARM⿿LFN. The 10-fold reduced daily dose was formulated in two soft gelatin capsules thus reducing the number of units to be taken at a time by the patient. The capsules showed good stability at room temperature for a year. The NLC were found to be safe in rats. The biocompatible NLC developed using an industrially feasible technique offer a promising solution for oral malaria therapy.

Construction of ordered porous polymer film and functionality of pore structure via microemulsion template method

Surface ordered porous polymer films have shown the great application prospect in the fields of optoelectronic devices, separation, bioscience, filtration and medicine. Among the various kinds of self-assembled methods, water droplet template approach has been widely investigated owing to its easy operation, wide application and low cost features. In this paper, we present and review the preparation of ordered porous polymer films via microemulsion method and the functionalization of cavity structures. We firstly introduce the development of microemulsion approach, the detail preparation procedures, morphology and dimension of ordered porous surfaces which usually exhibit hexagonal close packed honeycomb structures at several micrometers. Then we discuss the influence factors of preparation for ordered cavity structures, such as the surfactant, solvent, water content, droplet dimension and so on, and after that we provide the formation mechanism of porous films through microemulsion method utilizing the dynamic integration, thermal capillary force and interface energy balance concepts. Further, we discuss the modification method of cavity inner surface which realizes the local assembly of diverse functional water-soluble components into the cavities by just adding these compounds into water phase of emulsion solution, and several kinds of water soluble components have been adopted, such as polyoxometalates and proteins. We also list some characterization methods for cavity decoration, for example, EDX analysis which can be used to test the location of large mass or high content elements, and CLSM images which can be adopted to detect the positon of fluorescent molecules. Then, we review the current applications of cavity structures, for example, using the components within the cavities to complete specific recognition of proteins and construction of protein microarray, constructing glucose-responsive insulin delivery system by adopting the modified cavities as the drug reservoir, and fabricating cell pattern through employing the cavities to in situ fix the cells whose reactivity can be maintained after the assembling process. Different with the bottom-up breath figure method, the advantages of the emulsion approach are that diverse functional water-soluble components can be assembled into the cavities in one step and the introduced stabilizer can also be used to modify the pore surface, indicating synchronous self-assemble decoration of pore surface and introduction of new components. It is envisioned that polymer porous membranes could be used in the fields of biological materials and detection, drug delivery devices and cell modification and assembly, and so forth.

Catalytic evaluation of dendrimer and reverse microemulsion template Pd and Pt nanoparticles for the selective oxidation of styrene using TBHP

Here, we employed colloidal Pd and Pt nanoparticles synthesized by dendrimer templates as well as reverse microemulsions in the selective oxidation of styrene using tert-butyl hydroperoxide (TBHP) as an oxidant. We investigate their catalytic behavior and the feasibility as oxidation catalysts. High selectivity to styrene oxide, was achieved in the oxidation of styrene. The catalytic activities in terms of styrene conversion decreased in the order of dendrimer-templated Pd nanoparticles>thiol-capped Pd nanoparticles by reverse microemulsions>dendrimer-templated Pt nanoparticles>thiol-capped Pt nanoparticles by reverse microemulsions. This indicated that Pd-based catalysts were more efficient to catalyze the styrene oxidation reaction as compared to Pt-based catalysts. Furthermore, the dendrimer template synthetic method produced catalysts with higher activity as compared to those prepared by the reverse microemulsion template. The catalytic activities and selectivity profiles in various reaction conditions such as solvent type, styrene to TBHP ratio, type of catalysts, catalyst dosing, and temperature are discussed. The changes of average nanoparticle size after the reactions and the recyclability of Pd and Pt catalysts are examined. Overall results indicated that although higher catalytic activities were obtained with the use of dendrimer-templated nanoparticles, better recyclability as well as selectivity to styrene oxide was achieved with the use of thiol-capped Pd nanoparticles synthesized by reverse microemulsions.

MCFs的碳化对其葡萄糖氧化酶吸附性能的影响

本文以三嵌段共聚物聚氧乙烯–聚氧丙烯–聚氧乙烯(Pluronic P123)及三甲苯(TMB)为模板剂及扩孔剂，制备出介孔硅泡沫分子筛。以糠醇为碳源，运用硬模板法对介孔硅泡沫分子筛进行碳化，得到介孔碳泡沫分子筛。采用SEM观察、TEM观察及氮气吸附等手段对碳化后的介孔碳泡沫分子筛及之前的硅模板的外部形貌、粒径及孔道结构进行表征。结果表明，经过碳化后的介孔泡沫分子筛较好地保持了之前模板剂的颗粒尺寸和外部形貌。碳化后的介孔泡沫分子筛其窗口孔径、胞体孔径和孔容都有所下降，但比表面积却有所增大。将所制备的介孔碳泡沫分子筛和硅基模板剂分别用于葡萄糖氧化酶的负载，碳化后的介孔材料对葡萄糖氧化酶的吸附量大于硅基模板，表明拥有较小窗口粒径、较小胞体孔径和孔容的介孔碳泡沫分子筛表现出更优异的葡萄糖氧化酶负载性能，有望成为优良的酶载体材料。 The mesostructured cellular foams (MCFs) were synthesized using microemulsion templating, in which the nonionic triblock copolymer surfactant Pluronic P123 was served as template and 1,3,5-trimethylbenzene (TMB) as organic swelling agent. Then, by using mesostructured cellular foam silica as templates, furfuryl alcohol as carbon precursors, the carbon-based mesostructured cellular foam was prepared. The exterior morphologies and pore structures of the samples were characterized by Scanning Electron Microscope (SEM), Transmission Electron Microscopy (TEM) and nitrogen adsorption. It was found that mesostructured cellular foams kept its original particle size and external morphology after carbonization, and possessed the smaller windows and cell diameters and the smaller pore volumes, but had larger specific surface area. Both carbon-based and silicon-based mesocellular foams were used as the carriers for immobilization of glucose oxi-dase. The loading amounts on carbonaceous mesocellular foams were much higher than on the corresponding silicon templates. We can conclude that carbon-based mesocellular foam with smaller particle size, smaller window size and smaller pore volume had a better glucose oxidase adsorption performance. It might be served as the prospective enzyme carrier material.

Non-Platinum Group Metal Catalysts for Oxygen Reduction in Fuel Cell Applictaions

Over the last two decades the attention to alternative, low cost catalysts for fuel cells has been steadily rising. Non-Platinum Group Metal (Non-PGM) catalysts of several different types have been proposed, with those based on transition metal and nitrogen-carbon matrix (M-N-C) gaining the most attention. These catalysts are almost exclusively synthesized by pyrolysis in inert or reactive (ammonia-containing) atmosphere. Often a templating approach is used whether explicitly (hard template) or as a part of the processing conditions (soft template or pore-forming agents). Lately, such Non-PGM catalyst have started to be tested in Proton Exchange Membrane (PEM) and Alkaline Exchange Membrane (AEM) fuel cells, often aiming automotive applications. UNM has developed and demonstrated a family of Non-PGM catalysts from the M-N-C family of materials derived with the use of hard (oxide) templates. These catalysts were transferred as a technology to Pajarito Powder Co. and deployed as products for variety of applications. In this overview we will address the critical challenges that the UNM team has faced on the way to introduction of such catalysts for both acid and alkaline polymer electrolyte fuel cells. UNM catalysts synthesis is based on a Sacrificial Support Method (SSM). This is a templated synthesis approach for obtaining hierarchically structured materials based on the "lost wax technique" practiced through pyrolysis. In this method the catalysts precursors are being absorbed on mono-dispersed silica (or other oxide powder), or on meso-structured silica material, obtained by micro-emulsion templating, aerosol synthesis routes or evaporation-induced self-assembly. This oxide template is impregnated with the solution of the catalyst precursors: transition metal salt and a nitrogen-containing organic substance (usually an amine, nitrogen-containing polymer or macrocycle). Alternatively, a mechanochemical approach is used based on mechanically mixing (ball-milling) the support (usually mono-dispersed or meso-structured structured silica) and the transition metal, and nitrogen-carbon precursor. The mix is then thermally processed (pyrolyzed) and then the silica support is removed by etching (in KOH or HF). This results in a open frame structure of a “self-supported” material that consists of the catalyst only. The support has been removed by chemical dissolution. Synthesis of Non-PGM catalysts based on transition metals and N-containing carbonaceous materials obtained by both methods will be discussed. 1-5 Such hierarchical structures are advantageous in enhancement of the fuel cell performance since they correspond to the different levels of transport in the corrugated electrode matrixes. The fact that these materials consist of catalytic substance only (the support has been etched away) allows detail structural characterization. Using several methods: XPS, XAFS/XANES, Mossbauer Spectroscopy, BET and adsorption isotherm-derived pose size distribution, etc. we have built a hypothesis of the active site that includes graphene-like material with N-defects that include transition metal atomically dispersed and associated with the nitrogen defects in graphene (see Fig.). The mechanism of the oxygen reduction reaction on these M-N-C materials will be discussed as well. A wide variety of materials can be made by these methods in which not only the composition but also the microstructure can be varied. It is the combination of these attributes - control over microstructure at a number of different length scales and composition, simultaneously - that is extremely important to the performance of the electrocatalyst materials in a fuel cells. This paper will bring examples of successful practical applications of our materials in automotive technologies using both Polymer Electrolyte (PEMFC) and Alkaline Membrane (AMFC) Fuel Cells with gaseous and liquid fuels. 6-10 References 1 K. Artyushkova, et al., Top. Catalysis, 46 (2007) 263-275 2 S. Pylypenko, et al., Electrochim. Acta, 53 (2008) 7875-7883 3 J. Ziegelbauer, et al., J. Phys. Chem. C, 112 (2008) 8839–8849 4 T. Olson, et al., J. Power Sources, 183 (2008) 557–563 5 T. Olson, et al., J. Electrochem. Society, 157 (2010) B54-B63 6 A. Serov, et al., Electrochem. Comm., 22 (2012) 53-56 7 A. Serov, et al., Appl. Catalysis B: Env., 127 (2012) 300-306 8 M. Robson, et al., Electrochim. Acta, 90 (2013) 656–665 9 P. Atanassov and A. Serov, Japanese Society of Automotive Engineers, 67 (2013) 68-71 A. Serov, et al., Advanced Energy Materials, 4 (2014) DOI: 10.1002/aenm.201301735 Figure 1

A facile microemulsion template route for producing hollow silica nanospheres as imaging agents and drug nanocarriers

Hollow silica nanospheres with uniform size distribution and tuneable shell thickness were synthesized through a one-step reverse microemulsion method at room temperature within 24 h. These hollow nanospheres demonstrated effective encapsulation ability for FITC, Eu3+-complexes, iron oxide nanoparticles and chemotherapy drugs for potential imaging and drug delivery applications.

Fabrication of mesoporous silica nanospheres with radially oriented mesochannels by microemulsion templating for adsorption and controlled release of aspirin

The MSN spheres with narrow size distribution and radially oriented mesoporous channels were prepared using an O/W microemulsion system, consisting of CTAB (or PVP), ethanol, cyclohexane and water as template.

Preparation, characterization and lysozyme immobilization studies on siliceous mesocellular foams: Effect of precursor chemistry on pore size, wall thickness and interpore spacing

Three homologous series of siliceous meso-cellular foams (MCFs) were synthesized using microemulsion templating by incremental variation of ratio of organic pore expander, trimethyl benzene (TMB), and silica precursor (TEOS) concentrations using Pluronic™ block co-polymer (P123) as the surfactant. The calcined materials were tested for lysozyme immobilization to relate the adsorption capacities to meso-structure. Small angle X-ray scattering (SAXS) shows a short range ordering of pores. The pore size and wall thickness were determined from Porod analysis of the SAXS data combined with gas adsorption data. The pore size and lysozyme loading both increase systematically with TMB/P123 ratio, and decrease with increasing TEOS/P123 ratio. By comparing gas adsorption and SAXS data, we show that the BET method overestimates the mesopore specific surface area and therefore leads to an underestimate of the pore size. The effective pore size determined by the BdB-FHH method on the other hand is consistent with that determined by SAXS surface area analysis. The wall thickness (4.4±0.5nm), interpore distance (23.9±1.5nm) and meso-pore volume fraction (0.82±0.04) are independent of synthesis conditions. The mean pore size (33±8nm, spherical equivalent) is generally larger than the interpore distance, which forces the system to adopt a more cylindrical pore morphology at large pore and window sizes, which is confirmed by SAXS and TEM. TEM shows worm-like pores intermixed along with the familiar cellular foam phase.

Synthesis of hierarchically porous silicas with mesophase transformations in a four-component microemulsion-type system and the catalytic performance for dibenzothiophene hydrodesulfurization

Hierarchical porous materials especially the silica-based ones are undergoing rapid development due to potential applications in the fields of catalysis, adsorption, separation, and biomedical processes. Although various synthesis methods involving emulsions, colloids, and surfactants have been reported, synthesis of hierarchical porous silicas (HPS) with complex mesophase transformations by using a four-component microemulsion (surfactant/cosurfactant/oil/water) templating approach is still challenging. Herein, we have successfully synthesized porous silica materials by introducing n-butanol (Bu) as the cosurfactant and 1,3,5-trimethylbenzene (TMB) as the oil component in a four-component P123–n-butanol–1,3,5-trimethylbenzene–water system. By simply increasing the molar ratio of Bu to TMB continuously while keeping a fixed mass of TMB in the mean time, mesophase transformations, progressing from mesocellular foam (MCF) via a vesicle-like structure to an ordered 2D hexagonal structure (SBA-15), can be observed. Moreover, an opposite phase transformation process was also proved by gradually increasing the molar ratio of TMB to Bu by maintaining a certain value for the Bu content in the initial system. All the mixed phase silica materials including hexagonal–vesicle, MCF–vesicle–hexagonal, and MCF–disordered-SBA-15-type show hierarchically porous structures. The mechanism for the mesophase transformation was proposed and a micelle/microemulsion method with bimodal templates was put forward to form hierarchical porous silicas with a mixed phase of the MCF–disordered-SBA-15-type structure. Furthermore, a series of Al-containing mesoporous silicas with different structures (hexagonal, vesicle, MCF, MCF–vesicle–hexagonal, and MCF–disordered-SBA-15-type) were used as catalyst supports for dibenzothiophene hydrodesulfurization. The NiMo/Al-hierarchical porous silica catalyst with pore structures of MCF–disordered-SBA-15-type displayed the best hydrodesulfurization performance among all the studied catalysts.

Active curcumin nanoparticles formed from a volatile microemulsion template.

We report on biological performance of organic nanoparticles formed by a simple method based on rapid solvent removal from a volatile microemulsion. The particular focus of the study was on testing the suitability of the method for substances soluble in partially water-miscible organic solvents as well as on evaluating the therapeutic activity of the resultant nanoparticles. Curcumin was employed as a model for hydrophobic drug, and, as it is soluble in water-miscible organic solvents, it was successfully incorporated into a new cyclopentanone-water microemulsion system. During rapid solvent removal by spray-drying, the nanometric droplets of the microemulsion were converted into nanoparticles containing amorphous curcumin with the average size of 20.2±3.4 nm, having ζ potential of -36.2 ±1.8 mV. These nanoparticles were dispersible in water and retained the high loading of the active substance. The therapeutic activity of the resulting nanoparticles was demonstrated in a pancreatic cancer cell line Panc-1. The effective concentration for reducing the metabolic activity was found to be 11.5 μM for nanoparticles compared with 19.5 μM for free curcumin.

Comparative in vitro and in vivo evaluation of lipid based nanocarriers of Huperzine A

The purpose of the present investigation was to explore feasibility of nanocarrier based transdermal delivery of Huperzine A (HupA) for the treatment of Alzheimer's disease. For this investigation, microemulsion (ME), solid lipid nanoparticles (SLNs), and nanostructured lipid carriers (NLCs) were formulated and characterized for physicochemical parameters. The pseudo-ternary phase diagrams for microemulsion region were developed using generally recognized as safe (GRAS) excipients. The SLNs and NLCs were prepared by microemulsion template technique. These nanodispersions were formulated into gels for transdermal application and evaluated for various physicochemical parameters. In vitro permeation profiles in rat skin exhibited zero-order kinetics. HupA loaded ME exhibited superior permeation than NLCs followed by SLNs and cumulative amount permeated after 24h was found to be 147.68±9.42 μg/cm(2), 129.11±32.76 μg/cm(2) and 10.74±0.68 μg/cm(2), respectively. Furthermore, optimized gels were subjected to primary skin irritation testing over a period of 48 h and were found to be safe for skin application. In vivo efficacy tested in scopolamine induced amnesia model indicated significant improvement in cognitive function in mice group treated with developed nanocarrier based formulations as compared to the control group.

不同孔径MCFs的制备及其对溶菌酶的吸附性能

以三嵌段共聚物聚氧乙烯–聚氧丙烯–聚氧乙烯(Pluronic P123)及三甲苯(TMB)为模板剂及扩孔剂，采用微乳液模板法，通过控制TMB与P123的质量比合成了一系列不同孔径的介孔泡沫分子筛(MCFs)，利用TEM、N2吸附等手段对材料进行结构及性能表征。当TMB/P123质量比由0.5增至1.0时，材料的孔径增大，当其继续增至1.5时，孔径变小；溶菌酶吸附性能测试发现，质量比为1.5时合成的MCFs，其吸附速率最快，约1 h达到平衡，且其对酶的固定最牢固，酶不易脱落，吸附量可达到490 mg/g；此外，FT-IR分析发现MCFs吸附对溶菌酶的结构无明显影响。研究结果表明，MCFs合成时的TMB/P123质量比通过影响MCFs孔结构从而对酶吸附性能产生重要的影响；MCFs有望成为优良的酶载体材料。 The mesostructured cellular foams (MCFs) were synthesized using microemulsion templating, in which the nonionic triblock copolymer surfactant Pluronic P123 was served as template and 1,3,5-trimethylbenzene (TMB) as organic swelling agent. By controlling the mass ratio of TMB/P123, a series of MCFs with different pore size were prepared, and then the structural and chemical properties of MCFs were characterized by TEM and nitrogen adsorption. It was found that the pore size of MCFs increased when the mass ratio of TMB/P123 increased from 0.5 to 1.0, while that of MCFs decreased when the mass ratio continuously increased to 1.5. The MCFs were used as adsorbent for the adsorption of lysozyme. The maximum adsorption rate was obtained on MCFs-1.5 (mass ratio of TMB/P123 was 1.5), meaning that the sample reached equilibrium within 1 h. The immobilization of lysozyme on MCFs-1.5 prevented the leaching of enzyme effectively and the immobilized amount was up to 490 mg/g. Furthermore, FT-IR analysis revealed that the lysozyme adsorbed on MCFs could be held without evident structure changes. This study suggested that enzyme loading efficiency was clearly dependent on the size matching between the enzyme molecules and carrier pores, and the synthesized MCFs could be applied as excellent carriers for enzyme immobilization.

Synthesis of hydroxyapatite nanoparticles trough polyelectrolyte-modified microemulsions

The paper is focused on the formation of hydroxyapatite nanoparticles (HAp) in polyelectrolyte-modified microemulsions, in a microemulsion template phase consisting of cyclohexane, water, cationic surfactant and cosurfactant, in the presence of Na-polyacrylate (PAA) as an anionic polyelectrolyte. It is shown that PAA, can be incorporated into the individual inverse microemulsion droplets. The microemulsion droplets and PAA-filled microemulsion droplets can be successfully used as a template phase for the nanoparticles formation. Prepared HAp in presence of polyelectrolyte has a different morphology from samples which are synthesized in absence of polyelectrolyte. PAA leads to formation of needle-like HAp (20-30nm in diameter and 100-200nm in length). Formation of HAp at room temperature was confirmed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Size and morphology of the HAp samples were characterized using transmission electron microscopy (TEM).

Concentration sérique du vémurafénib

Artemether⿿lumefantrine (ARM⿿LFN) is a World Health Organization (WHO) approved fixed-dose combination having low solubility and poor oral bioavailability. Nanostructured lipid carriers (NLC) were developed to enhance the oral efficacy of this combination using the microemulsion template technique. They were characterized for drug content, entrapment efficiency, size distribution, in vitro release, antimalarial efficacy, and toxicity. The NLC showed sustained drug release. The recommended adult therapeutic dose is 80 mg ARM and 480 mg LFN (4 tablets) twice a day, which amounts to 160 mg ARM and 960 mg LFN daily. ARM⿿LFN NLC given once a day at 1/5 of therapeutic dose (16 mg ARM and 96 mg LFN) showed complete parasite clearance and 100% survival in Plasmodium berghei-infected mice. 33% of the mice treated with marketed tablets twice a day at the therapeutic dose showed late-stage recrudescence. Thus, NLC showed enhanced efficacy at 1/10 of the daily dose of ARM⿿LFN. The 10-fold reduced daily dose was formulated in two soft gelatin capsules thus reducing the number of units to be taken at a time by the patient. The capsules showed good stability at room temperature for a year. The NLC were found to be safe in rats. The biocompatible NLC developed using an industrially feasible technique offer a promising solution for oral malaria therapy.

Improved biochemical characteristics of crosslinked β-glucosidase on nanoporous silica foams

Large mesoporous cellular foam (LMCF) materials were synthesized using the microemulsion templating route. For the enzyme stabilization, β-glucosidase was immobilized onto mesocellular silica foams (MCFs) in a simple and effective way, a process achieved using enzyme adsorption followed by glutaraldehyde (GA) crosslinking. This resulted in the formation of crosslinked enzyme aggregates (CLEAs) of nanometer scale. The structural and chemical properties of these prepared materials were characterized by TG, CPMAS NMR and nitrogen adsorption measurements. The crosslinked immobilizates retained activity over wider ranges of temperature and pH than those of the free enzyme. Kinetic parameter (Km) of the immobilized β-glucosidase is lower than that of its free counterpart. The resulting CLEA was proved to be active and recyclable up to 10 cycles without much loss in activity. This demonstrates its prospects for commercial applications. The immobilizate exhibited enhanced storage stability characteristics than the native enzyme. In contrast to adsorbed GL and covalently bound glucosidase, the resulting crosslinked enzyme aggregates (CLEAs) showed an impressive stability with high enzyme loadings.

Interpenetrating polymer networks templated on bicontinuous microemulsions containing silicone oil, methacrylic acid, and hydroxyethyl methacrylate

Polydimethylsiloxane-poly(methacrylic acid—hydroxyethyl methacrylate) interpenetrating polymer networks (PDMS-P(MAA–HEMA) IPN) were formulated and polymerized simultaneously from bicontinuous microemulsion templates. Microemulsions containing reactive silicone oils and MAA/HEMA in aqueous solution were stabilized with silicone surfactants, and were then reacted at 50 °C for 3 h under an N2 atmosphere. The formation of bicontinuous morphology was confirmed by laser scanning confocal microscopy, reversible swelling behavior, differential scanning calorimetry, texture analysis, and permeability to vitamin B12 in aqueous solution. Incorporating polymerizable surfactants into the microemulsion aided in stabilizing the initial microemulsion structure during polymerization, yielding a more uniform IPN morphology with domain sizes of <200 nm at equilibrium swelling. The process developed here demonstrates a simple, single-step polymerization approach to forming IPNs from low viscosity microemulsion templates, and could potentially be extended to a variety of hydrophilic and hydrophobic monomers.