Effects of Lipid Composition on the Catalytic Behavior and Colloidal Stability of Palladium Nanoparticle-containing Lipid-nanoparticle Assemblies PDF Download
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Author: Nicholas Pavlakovich (Graduate student)
Publisher:
ISBN:
Category : Catalysis
Languages : en
Pages : 42
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Book Description
The research described in this thesis details the preparation and characterization of catalytically active LNAs. Palladium nanoparticles (PdNP) embedded in the lipid bilayer of LNAs dispersed in water were able to catalyze the hydrogenation of 1-octene when under 1 atm hydrogen gas. The rate of hydrogenation was dependent on the lipid composition of LNAs; cholesterol had a deleterious effect on activity but aided in stabilizing the colloidal dispersions. LNAs composed of DLPC performed hydrogenation more quickly than those of DSPC and also had greater colloidal stability. LNAs prepared in this study however showed decreased colloidal stability compared to their counterpart liposomes lacking PdNP.
Author: Nicholas Pavlakovich (Graduate student)
Publisher:
ISBN:
Category : Catalysis
Languages : en
Pages : 42
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Book Description
The research described in this thesis details the preparation and characterization of catalytically active LNAs. Palladium nanoparticles (PdNP) embedded in the lipid bilayer of LNAs dispersed in water were able to catalyze the hydrogenation of 1-octene when under 1 atm hydrogen gas. The rate of hydrogenation was dependent on the lipid composition of LNAs; cholesterol had a deleterious effect on activity but aided in stabilizing the colloidal dispersions. LNAs composed of DLPC performed hydrogenation more quickly than those of DSPC and also had greater colloidal stability. LNAs prepared in this study however showed decreased colloidal stability compared to their counterpart liposomes lacking PdNP.
Author: Rohan Shah
Publisher: Springer
ISBN: 3319107119
Category : Medical
Languages : en
Pages : 105
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Book Description
What are lipid nanoparticles? How are they structured? How are they formed? What techniques are best to characterize them? How great is their potential as drug delivery systems? These questions and more are answered in this comprehensive and highly readable work on lipid nanoparticles. This work sets out to provide the reader with a clear and understandable understanding of the current practices in formulation, characterization and drug delivery of lipid nanoparticles. A comprehensive description of the current understanding of synthesis, characterization, stability optimization and drug incorporation of solid lipid nanoparticles is provided. Nanoparticles have attracted great interest over the past few decades with almost exponential growth in their research and application. Their small particle size and subsequent high surface area make them ideal in many uses, but particularly as drug carrier systems. Nanoparticles made from lipids are especially attractive because of their enhanced biocompatibility imparted by the lipid. The work provides a detailed description of the types of lipid nanoparticles available (e.g. SLN, NLC, LDC, PLN) and how they range from imperfect crystalline to amorphous in structure. Current thoughts on where drugs are situated (e.g. in the core, or at the interface) and how this can be manipulated are discussed. The many techniques for production, including the author’s own variant of microwave heating, are fully discussed. Techniques for measuring arguably the most important characteristics of particle size and polydispersity are discussed, along with techniques to measure crystallinity, shape and drug capacity. Finally, a full chapter on techniques for measuring stability, both in the absence and presence of drugs, is discussed, along with suggestions on how to optimize that stability. This work appeals to students of colloid science, practitioners of research into drug delivery and academics alike.
Author: Dominick Damian Ortega (Graduate student)
Publisher:
ISBN:
Category : Alkenes
Languages : en
Pages : 46
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Book Description
Abstract: Despite the availability of many water-soluble organometallic and nanoparticulate catalysts, the direct application of water-soluble catalysts for the reaction of immiscible and hydrophobic substrates has been hindered by the low solubility of nonpolar reactants in water. Our research group has shown that alkanethiolate-capped palladium nanoparticles (PdNP) exhibit excellent catalytic activity and selectivity for hydrogenation of unsaturated compounds in organic solvents. This PdNP was synthesized using the thiosulfate protocol using sodium S-dodecylthiosulfate as ligand precursor. The purpose of this study is to examine the catalytic activity of PdNP encapsulated in 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) lipids in water. After the liposome film assembly of PdNP with PC in chloroform, the solvent was removed under vacuum and the hybrid was hydrated with phosphate buffered saline (PBS) solution. The resulting liposome- PdNP hybrids dissolved in water were characterized by 1H NMR, dynamic light scattering (DLS), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). During the catalysis reaction, the bilayer characteristics of liposome-PdNP hybrid would allow the hydrophobic substrate such as 1-octene and its isomers to momentarily enter the hydrophobic region of the catalysts with adequate stirring force. After the reaction, the resulting products from bi-phasic system were subsequently extracted with organic solvents and analyzed using gas chromatography (GC). The results suggested that the transformation of 1-octene to trans-2-octene and cis-2-octene occur after 1 h of reaction time. Transformation of trans-2-octene and cis-2-octene to octane appears to take place after the completion of a 24 h reaction time. Phase transition study was also done to evaluate the effects of temperature on the fluidity of the bilayer and on the catalytic activity of the system. Temperature study results indicate a significant increase in conversion percentage of substrate into product below the phase transition temperature while no further increase was observed at the phase transition temperature of DSPC. Further investigation using differential scanning calorimetry (DSC) showed that the phase transition temperature of DSPC slightly increased with the incorporation of the PdNP into the bilayer. Substrate effects were explored by using a longer alkyl substrate, 1-tetradecene, which lead to overall lower conversion after 24 h due to its larger and bulkier size.
Author: John D. Attelah
Publisher:
ISBN:
Category : Nanostructured materials
Languages : en
Pages : 0
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Book Description
Author's abstract: Rational design of active and stable palladium nanoparticles using peptide is emerging field in nanomaterial technology. Nanoparticles are preferred as catalysts compared to their bulk counter-parts due to their large surface area-to-volume ratio making them more reactive. The use of peptide to facilitate the formation and stabilization of the inorganic nanoparticles such as palladium is desirable due to their less toxic nature, and desired products formed after the completion of the reaction. In addition, peptide is known to impart high level of control over size and shape in nanoparticles. In this work, peptide-driven fabrication of catalytically stable and reactive palladium was conducted in organic solvents and used in Heck reaction catalysis of iodobenzene and butyl acrylate to form butyl cinnamate. The use of a peptide ligands contrasts with the traditional toxic bulky phosphine ligands, which are conventionally used to stabilize and solubilize bulky palladium metal catalyst. The optimum temperature for maximum yield of butyl cinnamate was investigated in series of reactions set up from 25 to 80 °C with other reaction parameters kept constant. Heck coupling reaction is industrially important in synthesis of various pharmaceuticals We successfully conducted, characterized, and quantified the Heck coupling reaction in ethanol and DMSO at 80 °C using palladium-capped peptide nanoparticles and triethyl amine base. Different engineered and control peptides were used to fabricate palladium nanoparticles formation and for enhancing their colloidal and stability during the Heck reaction. The peptides used were engineered from the control Pd4 (TSNAVHPTLRHL) peptide, which is known to specifically bind palladium metal via the histidines at positions six and eleven. The S2 (AFILPTG) peptide, which is specific to silica, was attached at either ends of the Pd4 peptide to form S2Pd4, Pd4S2, and S2Pd4S2. The engineered peptide-capped palladium nanoparticles were investigated for their colloidal stability and catalytic activity.
Author: May Maung
Publisher:
ISBN: 9781339826233
Category : Allyl alcohol
Languages : en
Pages : 48
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Book Description
Abstract: This thesis presents the systematic evaluation of palladium nanoparticles functionalized with well-defined small organic ligands that can provide a spatial control in the surrounding environment of nanoparticle catalyst surfaces. Various thiolate ligand-capped palladium nanoparticles are produced by using different S-alkylthiosufate ligand precursors in a two-phase system composed of toluene and water. These palladium nanoparticles are then characterized using transmission electron microscopy, thermogravimetric analysis, NMR, FT-IR, and UV-vis spectroscopy. The catalysis studies on alkanethiolate-capped palladium nanoparticles with different ligand structures (linear alkyl vs cyclohexyl vs phenyl) show that the chemical and structural composition of a monolayer surrounding the palladium nanoparticles greatly influences the overall activity and selectivity of nanoparticle catalysts for the hydrogenation, isomerization, and hydrogenolysis of allylic alcohols. Especially, the effect of non-covalent interactions between surface ligands and incoming substrates in the near-surface environment is observed. Furthermore, the catalytic properties of & ohgr;-carboxylate-functionalized alkanethiolate-capped palladium nanoparticles are studied for the biphasic reactions of hydrophobic allylic alcohols that are immiscible in aqueous solution. The systematic investigations on the influence of pH and substrate size are performed to check the utility of structurally stable and water-soluble palladium nanoparticles as new micellar catalysts.
Author: Teja Gošek
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Author: Ana Catarina Silva
Publisher: Mdpi AG
ISBN: 9783036515502
Category :
Languages : en
Pages : 352
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Book Description
The use of lipid-based nanosystems, including lipid nanoparticles (solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC)), nanoemulsions, and liposomes, among others, is widespread. Several researchers have described the advantages of different applications of these nanosystems. For instance, they can increase the targeting and bioavailability of drugs, improving therapeutic effects. Their use in the cosmetic field is also promising, owing to their moisturizing properties and ability to protect labile cosmetic actives. Thus, it is surprising that only a few lipid-based nanosystems have reached the market. This can be explained by the strict regulatory requirements of medicines and the occurrence of unexpected in vivo failure, which highlights the need to conduct more preclinical studies. Current research is focused on testing the in vitro, ex vivo, and in vivo efficacy of lipidbased nanosystems to predict their clinical performance. However, there is a lack of method validation, which compromises the comparison between different studies. This book brings together the latest research and reviews that report on in vitro, ex vivo, and in vivo preclinical studies using lipid-based nanosystems. Readers can find up-todate information on the most common experiments performed to predict the clinical behavior of lipid-based nanosystems. A series of 15 research articles and a review are presented, with authors from 15 different countries, which demonstrates the universality of the investigations that have been carried out in this area.
Author: Yihui Yang
Publisher:
ISBN:
Category :
Languages : en
Pages : 94
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Book Description
This thesis presents both experimental and modeling studies on the formulation of stable lipid nanoparticle dispersions. A population balance equation (PBE) model was developed for prediction of the average polymorph content and aggregate size distribution to better understand the undesirable SLN aggregation behavior. Experimental and modeling studies showed that the polymorphic transformation was the rate determining step for my system, SLNs with smaller initial size distributions aggregated more rapidly, and aggregates contained particles with both alpha and beta crystals. Next the effect of different liquid carrier oils on the crystallization and aggregation behavior of tristearin NLC dispersions was investigated. I found that NLC dispersion stability was strongly affected by the type and amount of the oil. The results suggested that oil trapped within the growing crystal matrix accelerated the polymorphic transformation but retarded the large shape change normally associated with the transformation. Based on PBE simulation results, I hypothesized that improved NLC dispersion stability was attributable to both reduced particle shape change, which created less new surface area to be covered by surfactant, and increased mobility of surfactant molecules, which resulted in available surfactant being more efficient at covering created surface area. Finally I also studied the effect of formulation variables on the aggregation behavior and rheology of NLC dispersions. I found that NLC dispersion viscosity was strongly affected by particle aggregation. The viscosity of the dispersion could be modified by at least an order of magnitude by controlling particle aggregation using different surfactant and oil concentrations. Oscillatory sweep tests showed typical behaviors of a viscoelastic liquid and a viscoelastic solid for non-aggregated and aggregated NLC dispersions, respectively. Modeling results suggested a stronger bonding force and a higher aggregation efficiency with decreasing surfactant and/or oil concentrations. Both oscillatory sweep experiments and modeling results indicated an interconnected network structure in the aggregated dispersions, while no indication of network formation was observed for non-aggregated dispersions. These results suggested that controlled aggregation represents a promising approach for modifying the viscosity of NLC dispersions without adding viscosity enhancers and could reduce the time and cost for NLC production.
Author: Bhrat Jyoti
Publisher:
ISBN:
Category :
Languages : en
Pages : 102
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Book Description
Author: Matthew Ryan Preiss
Publisher:
ISBN:
Category : Lipids
Languages : en
Pages : 426
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Book Description
