Growing gold nanostructures for shape-selective cellular uptake.

With development in the synthesis of shape- and size-dependent gold (Au) nanostructures (NSs) and their applications in nanomedicine, one of the biggest challenges is to understand the interaction of these shapes with cancer cells. Herein, we study the interaction of Au NSs of five different shapes with glioblastoma-astrocytoma cells. Three different shapes (nanorods, tetrahexahedra, and bipyramids), possessing tunable optical properties, have been synthesized by a single-step seed-mediated growth approach employing binary surfactant mixtures of CTAB and a secondary surfactant. By the use of two-step seed-mediated approach, we obtained new NSs, named nanomakura (Makura is a Japanese word used for pillow) which is reported for the first time here. Spherical Au nanoparticles were prepared by the Turkevich method. To study NS-cell interactions, we functionalized the NSs using thiolated PEG followed by 11-Mercaptoundecanoic acid. The influence of shape and concentration of NSs on the cytotoxicity were assessed with a LIVE/DEAD assay in glioblastoma-astrocytoma cells. Furthermore, the time-dependent uptake of nanomakura was studied with TEM. Our results indicate that unlike the other shapes studied here, the nanomakura were taken up both via receptor-mediated endocytosis and macropinocytosis. Thus, from our library of different NSs with similar surface functionality, the shape is found to be an important parameter for cellular uptake

Enhancing ASP flooding by using special combinations of surfactants and starch nanoparticles

This study aimed to address the challenges faced by mature oilfields in extracting substantial oil quantities. It focused on improving the efficiency of alkaline–surfactant–polymer (ASP) flooding technique, which is a proven tertiary recovery technology, to overcome scaling issues and other hindrances in its large-scale implementation. Appropriate materials and their suitable concentrations were selected to enhance the ASP flooding technique. Special surfactants from Indonesia were introduced to improve the interfacial tension reduction and wettability alteration. Reservoir rock model that resembling Langgak oilfield in Sumatra was utilized, and low-salinity water was employed to mimic the oilfield conditions. Starches derived from cassava nanoparticles (CSNPs) and purple yam nanoparticles (PYNPs) were combined separately with conventional hydrolyzed polyacrylamide (HPAM) polymer to enhance its performance. Sodium hydroxide and sodium carbonate were used as alkaline in final ASP formula. It was demonstrated from this research that only two combinations of ASP formulations have led to improved oil recovery. One combination utilizing PYNPs resulted in 39.17% progressive recovery, while the other combination incorporating CSNPs achieved 35% incremental oil recovery. The ASP combination that resulted in recovery rate of 39.17% was composed of sodium hydroxide (NaOH) at a concentration of 1.28 wt.%, PSC EOR 2.2 (0.98 wt.%), and a combined polymer consisting of HPAM (0.2 wt.%) and PYNPs nano-starch (0.6 wt.%). The second combination led to 35% recovery rate and involved NaOH also at concentration 1.28 wt.%, PSC HOMF (0.63 wt.%), and a combined polymer comprising from HPAM (0.2 wt.%) and CSNPs nano-starch (0.8 wt.%). These findings of this study highlighted the potential of this modified ASP flooding to enhance oil recovery in mature oilfields, thereby offering valuable insights for oil industry

Smart and Multifunctional Core-Shell Nanoparticles (NPs) for Drug Delivery

Nanomaterials designed for drug delivery applications require important properties that include monodispersity, biocompatibility, long circulation time which are dependent on size, shape, composition, surface charge among others. Incorporation of targeting and imaging modalities into such nanomaterials allows for both therapeutic and diagnostic functions. Au nanoparticles (NPs), besides being biocompatible, are known to show remarkable optical properties, widely exploited for both bio-sensing and imaging. Setting in of anisotropy causes a wider frequency response range in terms of plasmonic properties, making them promising candidates for hyperthermia. On the other hand, Fe NPs display superparamagnetic properties that can be used for targeting as well as imaging based on magnetic resonance. Another field of nanomaterials that has garnered interest in recent times is stimuli sensitive hydrogels that swell and collapse in response to temperature and/or pH. These entropically driven volumetric transitions enable release of the cargo as a function of changing stimuli, making them promising candidates for controlled release. Combination of nanomaterials leads to synergistic enhancement of properties stemming from their respective counterparts. Core-shell NPs is one such combination that has been studied in this work. The main focus of this thesis has been to synthesize, characterize and functionalize core-shell NPs with an aim to use these nanomaterials for theranostic (therapeutic and diagnostic combined) applications. In this pursuit, core-shell Fe@Au NPs, anisotropic Au NPs, poly(N-isopropylacrylamide) (pNIPAM) based hydrogels and hybrid NPs formed by combination of metallic NPs and hydrogels have been studied. The physico-chemical properties of these NPs have been mapped using a wide array of characterization techniques. Size measurements have been done using dynamic light scattering (DLS) and scanning transmission electron microscopy S(T)EM. The plasmonic properties of Au have been characterized primarily using UV-Vis spectroscopy while surface properties of the NPs have been tracked using electrophoretic mobility measurements, X-ray photoelectron spectroscopy (XPS) among other techniques. Different hybrid NPs have been loaded with model protein drug Cytochrome-C or L-Dopa, a drug administered for Parkinson’s disease, in order to understand the effects of size, shape, particle number density, drug-carrier interaction, response to stimuli on both loading and release. Release kinetics have been modelled in order to understand the conformational changes in the NPs leading to effective release of the drug. Fe@Au NPs have been shown to have negligible cytotoxic effects on different cell lines, in addition to their remarkable magnetic and optical properties. In order to further modify the optical properties, anisotropic Au NPs have been synthesized to understand their growth mechanisms. Five differently shaped Au NPs have been thereafter functionalized to assess their cytotoxicity on cancer cells and also to understand the role of shape in the release kinetics of a model protein drug. One of the main findings from the thesis work is that incorporation of metallic NPs inside temperature and/or pH sensitive hydrogels enhances drug loading capacities. In addition, the loaded drug is squeezed out at a faster rate from these systems when the hydrogel units collapse above volume phase transition temperature (VPTT). The swellingcollapse properties of the hydrogels have been captured using a robust methodology developed for the determination of VPTT. A predictive reversibility parameter has been defined for the first time taking all the system state points into consideration. Thus, the NPs studied within the scope of this work provide an incremental contribution to the ever expanding search for smart materials for drug delivery applications

Biodegradable Nano-Clusters as Drug Delivery Vehicles

The master thesis has investigated primarily on the synthesis of different polymeric NPs viz PLA (synthesized in house as well as commercial grade), PLGA (commercial) and PCL(synthesized in house, having different functionalities ?COOH, -PEG and their blends) employing flash nano-precipitation technique in a multi inlet vortex mixer (MIVM), previously optimized in the Morbidelli group at ETH. These NPs were characterized using DLS (Dynamic Light Scattering) and Zeta-Sizer to report the variation of the sizes and zeta potentials respectively of the NPs as a function of polymer molecular weight and initial concentration of polymer. The lowest possible sizes of the NPs were then selected for further studies as the overall motivation of the work is to synthesize NCs composed of primary particles and thereafter compare and contrast drug loading, encapsulation efficiencies and release kinetics of a model drug between the two. Ibuprofen (model drug) was loaded into the primary NPs using the MIVM setup, following which drug loading and encapsulation efficiencies were measured using High Performance Liquid Chromatography (HPLC). The release kinetics experiments were performed at 37°C and also studied at room temperature (25°C) and 45°C to evaluate the effect of temperature on release mechanism. The drug-loaded NPs were separated from the free drug in solution at different times using centrifugal filtration. The amount of drug released over time was measured by analyzing these supernatants using HPLC. The MIVM setup is found to produce stable polymeric NPs as small as 50nm and as large as 155nm depending on polymer concentration and nature of polymer. The results indicate that this setup is capable of producing drug loaded NPs with high drug loading efficiencies varying between 75% and 88% differing with polymers. This particular aspect has been established to be both reproducible and valid for a wide range of polymers through subsequent experiments. On the contrary, the release kinetics from almost all the different types of polymeric systems is slow; lasting over several days and moreover, it is not possible to release the entire loaded drug. It is claimed that either the chemical interaction of the polymers with ibuprofen or the location of the drug inside the polymeric NPs is the potential reason for extremely slow release kinetics. It is therefore suggested that further investigation is needed for the same system with another drug, having similar solubility parameters as ibuprofen to confirm the observed behaviour or even a completely different synthesis method for drug loaded polymeric NPs using ibuprofen to substantiate the observed results

Biodegradable Nano-Clusters as Drug Delivery Vehicles

The master thesis has investigated primarily on the synthesis of different polymeric NPs viz PLA (synthesized in house as well as commercial grade), PLGA (commercial) and PCL(synthesized in house, having different functionalities ?COOH, -PEG and their blends) employing flash nano-precipitation technique in a multi inlet vortex mixer (MIVM), previously optimized in the Morbidelli group at ETH. These NPs were characterized using DLS (Dynamic Light Scattering) and Zeta-Sizer to report the variation of the sizes and zeta potentials respectively of the NPs as a function of polymer molecular weight and initial concentration of polymer. The lowest possible sizes of the NPs were then selected for further studies as the overall motivation of the work is to synthesize NCs composed of primary particles and thereafter compare and contrast drug loading, encapsulation efficiencies and release kinetics of a model drug between the two. Ibuprofen (model drug) was loaded into the primary NPs using the MIVM setup, following which drug loading and encapsulation efficiencies were measured using High Performance Liquid Chromatography (HPLC). The release kinetics experiments were performed at 37°C and also studied at room temperature (25°C) and 45°C to evaluate the effect of temperature on release mechanism. The drug-loaded NPs were separated from the free drug in solution at different times using centrifugal filtration. The amount of drug released over time was measured by analyzing these supernatants using HPLC. The MIVM setup is found to produce stable polymeric NPs as small as 50nm and as large as 155nm depending on polymer concentration and nature of polymer. The results indicate that this setup is capable of producing drug loaded NPs with high drug loading efficiencies varying between 75% and 88% differing with polymers. This particular aspect has been established to be both reproducible and valid for a wide range of polymers through subsequent experiments. On the contrary, the release kinetics from almost all the different types of polymeric systems is slow; lasting over several days and moreover, it is not possible to release the entire loaded drug. It is claimed that either the chemical interaction of the polymers with ibuprofen or the location of the drug inside the polymeric NPs is the potential reason for extremely slow release kinetics. It is therefore suggested that further investigation is needed for the same system with another drug, having similar solubility parameters as ibuprofen to confirm the observed behaviour or even a completely different synthesis method for drug loaded polymeric NPs using ibuprofen to substantiate the observed results

The Influence of Differently Shaped Gold Nanoparticles Functionalized with NIPAM-Based Hydrogels on the Release of Cytochrome C

Here, we report the synthesis and functionalization of five different shapes of Au nanoparticles (NPs), namely nanorods, tetrahexahedral, bipyramids, nanomakura, and spheres with PEG and poly (N-isopropylacrylamide)-acrylic acid (pNIPAm-AAc) hydrogels. The anisotropic NPs are synthesized using seed-mediated growth in the presence of silver. The NPs have been characterized using Dynamic Light Scattering (DLS), zeta potential measurements, UV-Visible spectrophotometry (UV-Vis), and Scanning Transmission Electron Microscopy (S(T)EM). Cyt C was loaded into the PEG-hydrogel-coated AuNPs using a modified breathing-in method. Loading efficiencies (up to 80%), dependent on particle geometry, concentration, and hydrogel content, were obtained. Release experiments conducted at high temperature (40 °C) and acidic pH (3) showed higher release for larger sizes of PEG-hydrogel-coated AuNPs, with temporal transition from spherical to thin film release geometry. AuNP shape, size, number density, and hydrogel content are found to influence the loading as well as release kinetics of Cyt C from these systems

Application of biopolymer schizophyllan derived from local sources in Malaysia for polymer flooding operation

After the application of primary and secondary recovery methods, a significant amount of oil gets left behind in the reservoir. Thus, Enhanced Oil Recovery (EOR) methods are the only viable options. Polymer flooding has been widely used for many years. The ability of a polymer to sustain high temperature and salinity reservoir conditions, while taking into account the cost of the polymer, is a challenging aspect of its application in polymer flooding. Due to the forthcoming environmental regulation, the eco-friendly biopolymers have been gaining importance. This study aims to investigate the biopolymer schizophyllan produced utilizing locally and cheaply available sources in Malaysia for its rheological property at various range of biopolymer concentration. Also, the effect of aging at high temperature on the biopolymer viscosity was studied. A core flooding experiment was also performed utilizing a Berea sandstone core at an 80?°C reservoir temperature and a salinity of 90,000?ppm. The rheological studies showed a shear thinning behavior at all biopolymer concentrations. The effect of aging up to a period of 6 months exhibited insignificant decrease in biopolymer viscosity. Core flooding experiments using the biopolymer derived from local sources showed an incremental oil recovery of 17.25% after waterflooding

Effect of Iron Oxide Nanoparticles on the Properties of Water-Based Drilling Fluids

In recent years, several studies have indicated the impact of nanoparticles (NPs) on various properties (such as viscosity and fluid loss) of conventional drilling fluids. Our previous study with commercial iron oxide NPs indicated the potential of using NPs to improve the properties of a laboratory bentonite-based drilling fluid without barite. In the present work, iron oxide NPs have been synthesized using the co-precipitation method. The effect of these hydrophilic NPs has been evaluated in bentonite and KCl-based drilling fluids. Rheological properties at different temperatures, viscoelastic properties, lubricity, and filtrate loss were measured to study the effect of NPs on the base fluid. Also, elemental analysis of the filtrate and microscale analysis of the filter cake was performed. Results for bentonite-based fluid showed that 0.019 wt% (0.1 g) of NPs reduced the coefficient of friction by 47%, and 0.0095 wt% (0.05 g) of NPs reduced the fluid loss by 20%. Moreover, for KCl-based fluids, 0.019 wt% (0.1 g) of additive reduced the coefficient of friction by 45%, while higher concentration of 0.038 wt% (0.2 g) of NPs shows 14% reduction in the filtrate loss. Microscale analysis shows that presence of NPs in the cake structure produces a more compact and less porous structure. This study indicates that very small concentration of NPs can provide better performance for the drilling fluids. Additionally, results from this work indicate the ability of NPs to fine-tune the properties of drilling fluids.publishedVersio

Current developments and future outlook in nano fluid flooding: a comprehensive review of various parameters influencing oil recovery mechanisms

Utilization of nanoparticles for enhanced oil recovery (EOR) has attracted great attention in recent decades. However, various constraints influence fluid-fluid and fluid-rock interactions of nanofluids and subsequently oil recovery. A comprehensive review of existing literatures on how to mitigate against these limits are presented in this study. Furthermore, nanofluid EOR mechanisms and various application parameters which may influence nanofluid flooding efficiency were discussed. Also, the basic steps for preliminary investigation of nanomaterials for EOR, the challenges, gaps, and future trends associated with nanofluids reservoir field applications were suggested. Field trials results have proven that nanofluids can influence various EOR mechanisms

Impact of various nanoparticles on the viscous properties of water based drilling fluids

Properly designed drilling fluid is a key element in achieving safe and effective drilling operations. Rheological parameters of drilling fluid determine the equivalent circulation density, the pump pressure, and hole cleaning efficiency. Also, they have a significant role in predicting the stability of drilling fluid under static and low shear rates. The chemical composition of the drilling fluid controls the rheological parameters. Recently, studies have shown that a small concentration of nanosized materials in the drilling fluid can substantially impact the rheological parameters of the drilling fluids. In this study, various nanoparticles (NPs) with different shapes, sizes, and surface charges were used to investigate their impact on the viscous properties of water-based drilling fluid. Bentonite and KCl water-based drilling fluids were used as the base fluids. NPs such as Iron oxide, Silica (SiO2), and multi-walled carbon nanotubes (MWCNT) were added to these base fluids. Also, surface functionalization of the NPs with polymer and functional groups such as -OH and -COOH groups was done to compare the effect of bare NPs with surface functionalized NPs. Hershel-Buckley model with dimensionless shear rates was used to calculate the low and high shear curvature exponents, surplus stress, and yield stress of the samples. Results indicate that NPs alter drilling fluid’s viscous properties based on their sizes, shapes, and surface charges. Moreover, the functionalization of NPs also modifies the properties based on the functional group attached to the NPs surface. This work shows that changing the size, shape, and surface charge of NPs has impact on viscous parameters, and NPs with different properties can fine-tune the fluid’s viscous properties based on the requirement for drilling fluid