Superparamagnetic iron oxide nanoparticles (SPIONs), due to their controllable sizes, relatively long in vivo half-life and limited agglomeration are ideal for biomedical applications such as magnetic labeling, hyperthermia cancer treatment, targeted drug delivery and for magnetic resonance imaging (MRI) as contrast enhancement agents. However, very limited studies exist on detecting and characterizing these SPIONs in vitro in physiologically relevant conditions. It would be of interest to localize and characterize individual SPIONs at the nanoscale in physiologically relevant conditions. MFM offers great potential for this purpose. We evaluate the applicability of Magnetic Force Microscopy (MFM) in air as well as in liquid to characterize bare and SiO2 coated SPIONs on mica .The magnetic properties of bare and SiO2 coated SPIONs are compared on the nanoscale using MFM. MFM phase- shift dependence on scan height is investigated using SPION samples that have been coated in hydrophobic polymers, polystyrene (PS) and poly (methyl methacrylate) (PMMA). The polymers are used to spin-coat SPION samples and mimic cell lipid bilayers. Nanoscale MFM images of SPIONs in a liquid environment, covered with these hydrophobic polymers are also presented for the first time. The use of 3-merceptopropyltrimethoxysilane (3-MPTS) to covalently attach SiO2 SPIONs to gold substrates for the potential purpose of MFM imaging in liquid is also briefly addressed. These results will allow us to understand the feasibility of detecting magnetic nanoparticles within cell membranes without any labeling or modifications and present MFM as a potential magnetic analogue for fluorescence microscopy. These results could be applied to cell studies and will lead to a better understanding of how SPIONs interact with cell membranes and have a valuable impact for biomedical applications of all types of magnetic nanoparticles.

Magnetic particles offer attractive features, so its development in a wide range of disciplines, including medical applications, has been very fruitful. As a result of the special physical properties of magnetic nanoparticles, many potential applications are made available in biomedicine. The most important feature of these particles is its magnetic forces, and it has been utilized in applications such as magnetic separation, drug delivery, hyperthermia and magnetic resonance imaging contrast agent. The important properties of magnetic particles for biomedical applications are nontoxicity, biocompatiblilty, injectability, and high-level accumulation in the target tissue or organ to two most important property among those mentioned above are nontoxicity and biocompatiblilty for available clinical trials. Some researchers have used polymers or polysaccharides coating on these surface of the magnetic material to improve the material's nontoxicity and biocompatiblilty. Common materials are dextran, polyethylene glycol, polyvinyl alcohol, starch and chitin and so on. We embedd Fe3O4 magnetic nanoparticles into agar hydrogels in the experiment, then made into powder by drying and grinding, using XRD, FTIR, TEM, SQUID, TGA and zeta potential identification of material properties. We examined its toxicity and the possibility for large scale production. This method can make use of simple and inexpensive way to mass-produce synthetic these biocompatible magnetic materials.

Superparamagnetic iron oxide nanoparticles (SPIONs), due to their controllable sizes, relatively long in vivo half-life and limited agglomeration are ideal for biomedical applications such as magnetic labeling, hyperthermia cancer treatment, targeted drug delivery and for magnetic resonance imaging (MRI) as contrast enhancement agents. However, very limited studies exist on detecting and characterizing these SPIONs in vitro in physiologically relevant conditions. It would be of interest to localize and characterize individual SPIONs at the nanoscale in physiologically relevant conditions. MFM offers great potential for this purpose. We evaluate the applicability of Magnetic Force Microscopy (MFM) in air as well as in liquid to characterize bare and SiO2 coated SPIONs on mica .The magnetic properties of bare and SiO2 coated SPIONs are compared on the nanoscale using MFM. MFM phase- shift dependence on scan height is investigated using SPION samples that have been coated in hydrophobic polymers, polystyrene (PS) and poly (methyl methacrylate) (PMMA). The polymers are used to spin-coat SPION samples and mimic cell lipid bilayers. Nanoscale MFM images of SPIONs in a liquid environment, covered with these hydrophobic polymers are also presented for the first time. The use of 3-merceptopropyltrimethoxysilane (3-MPTS) to covalently attach SiO2 SPIONs to gold substrates for the potential purpose of MFM imaging in liquid is also briefly addressed. These results will allow us to understand the feasibility of detecting magnetic nanoparticles within cell membranes without any labeling or modifications and present MFM as a potential magnetic analogue for fluorescence microscopy. These results could be applied to cell studies and will lead to a better understanding of how SPIONs interact with cell membranes and have a valuable impact for biomedical applications of all types of magnetic nanoparticles.

This thesis is to study on the preparation of iron nano-particles by electrochemical method in aqueous solution. The resultant particles are stabilized as a colloidal suspension by the use of cationic surfactants. The advantages include those high yield, low cost, and simple control of particle size by adjustment of the current density. It is revealed that current density, distance between electrodes, temperature, and surfactant concentration of aqueous solution play important roles on the preparation of nano-particles. The morphology, structure, composition, and optical properties of nano-particles are studied by Ultraviolet-Visible spectrophotometer (UV/Vis spectrophotometer), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The effect of particle size on the magnetic properties of nano-particles has been studied using superconducting quantum interference device (SQUID). According to the experimental results, the greater imposed current density is applied, the smaller the particle size is obtained. The absorption spectra of the particles exhibit that the characteristic peak of surface plasmon band is at 264 nm. The maghemite (£^-Fe2O3) phase is clearly confirmed by X-ray diffraction and TEM analysis. From the hysteresis loop studies, particles are paramagnetic at room temperature and they exhibited super-paramagnetic phenomenon. They become ferromagnetic at low temperature. The increase of the coercive force is due to the reduction of thermal vibration.

>Magister Scientiae - MSc / Magnetosomes, produced by magnetotactic bacteria (MTB), are the most attractive alternative source of non-toxic biocompatible magnetic nanoparticles (MNPs). A magnetosome contains Fe2O4 magnetite with properties superior to MNPs synthesized by the traditional chemical route. However, synthesis of magnetosomes on large scale has not been achieved yet because magnetotactic bacteria are fastidious to grow. In addition, magnetosomes are generally “soft” magnetic materials which can only be used for some applications, while other applications require “hard” magnetic materials. Here at the Institute of Microbial Biotechnology and Metagenomic (IMBM), a study is being conducted on cloning and expression of the magnetosome gene island (MIA), the genetic machinery for magnetosome formation, in an easy to culture E. coli strain. The magnetic properties of the magnetosome can be manipulated by doping with divalent metals such as Ni2+ or Co2+ for a variety of applications. The specific objective of this study was to genetically engineer E. coli strains which accumulate intracellular Ni2+ or Co2+ in order to manipulate the magnetic properties of the magnetosomes. Three E. coli mutants and a wild type strain were transformed with high affinity Ni2+ or Co2+ uptake genes and evaluated for intracellular accumulation at different medium concentrations of NiCl2 or CoCl2. Cellular iron and magnesium were also evaluated because iron is the major component of the magnetosome and magnesium is important for cell growth. The wild type strain, EPI 300 habouring Ni2+ uptake permease the hoxN gene or Co2+ uptake ABC type transporter cbiKMQO operon was found to accumulate the most intracellular Ni2+ or Co2+ in medium conditions most likely to induce magnetosome formation and magnetite manipulation. This strain can be used to co-express the MIA and Ni2+ or Co2+ uptake gene for mass production of magnetosome with altered magnetic properties.

Energy harvesting using ferrofluid in OHP. Characterization of as-synthesized (bare) and surface-modified ferrofluid samples was performed using Fourier transform infrared spectroscopy, dynamic light scattering, X-ray powder diffraction, transmission electron microscopy, and atomic force microscopy. These ferrofluids were tested in a novel oscillating heat pipe set-up was utilized to harvest electricity, demonstrating the concept of ferrofluidic induction. Cobalterrite nanoparticles surface-modified with citric acid demonstrated good magnetic strengths and generated voltages close to those of the as-synthesized ferrofluids while maintaining dispersion. Surface modification of ferrous nanoparticles with SRP. Thermo responsive polymer poly(N-isopropylacrylamide) was successfully grown from the surface of cobalt-zinc ferrite nanoparticles. A dual responsive block copolymer, pH and thermo responsive comprised of poly(itaconic) acid and poly(N-isopropylacrylamide) was successfully polymerized from the surface of ferrous oxide nanoparticles. These composite having magnetic properties along with stimulus can be used in applications such as controlled drug delivery and similar biomedical applications.

This thesis explores a method to fabricate magnetic membranes with asymmetric distribution of particles and their testing as actuators. Focus of this research is to fabricate thin polymeric sheets and thickness range of 120-125µm, with asymmetric distribution of magnetic nano particles, employing micromagnets during the fabrication. The micromagnets are used to localize the magnetic particles during the curing process at selected locations. The effect of the asymmetric distribution of magnetic particles in the membrane is used for the first time. Magnetite (Fe3O4) is used as the magnetic particles that is embedded into a polymeric membrane made of polydimethylsiloxane (PDMS); the membrane is then tested in terms of deflection observed by using a high-resolution camera. From the perspective of the biomedical application, PDMS is chosen for its excellent biocompatibility and mechanical properties, and Fe3O4 for its non-toxic nature. Since magnetic actuation does not require onboard batteries or other power systems, it is very convenient to use in embedded devices or where the access is made difficult. A comparative study of membranes with asymmetric and randomly distributed particles is carried out in this thesis. The asymmetric distribution of magnetic particles can benefit applications involving localized and targeted treatments and precision medicine.

Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: ß-Galactosidase of Escherichia coli is the equivalent of lactase in humans and has the ability to bind and hydrolyse lactose. Lactase de ciency is a common phenomenon present in almost 70% of the world's population. This has resulted in greater than before demands on the food processing industry to develop a method that will allow for the hydrolysis of the disaccharide lactose in milk but will also allow for the removal of the remaining active enzyme. In this thesis, a new method, that is bio-speci c and well characterized for the removal of lactose from a lactose containing solution, is described. The E537D mutated version of ß-Galactosidase, which has a much lower activity compared to the wildtype and is able to bio-speci cally bind lactose for longer periods, was covalently immobilised to commercially available magnetic nanoparticles (fl uidMAG-Amine) via two coupling strategies. Glutaraldehyde is a cross-linking agent that reacts with amine groups, while N- (3-Dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC) is a coupling agent that activates carboxylic groups. These agents are widely used for the coupling of biomolecules to solid supports. The covalently coupled fluidMAG-E537D ß-Galactosidase particles were characterized regarding retained enzymatic activity and ability to bind and physically remove lactose from a lactose containing solution by applying an external magnetic eld, after lactose binding, to the enzyme-particle complex in solution. Each component aimed at yielding this functionally immobilised enzyme complex was studied and optimized to contribute to the development of this novel technique, which is a ordable and simple, for the removal of lactose from solution for the ultimate production of lactose free milk. Results indicated the glutaraldehyde method of ß-Gal cross-linking to fluidMAG-Amine to be the preferred strategy since it allowed an increased carrier capacity of protein to the particles. The glutaraldehyde cross-linked protein also exhibited a two-fold higher activity than the EDC coupled protein. Furthermore, the glutaraldehyde cross-linked fluidMAG-E537D ß-Gal was able to physically remove 34 % of the lactose from a 0.2 nmol/L lactose in solution. This, therefore, con rmed the potential use of this novel technique in the food processing industry. / AFRIKAANSE OPSOMMING: ß-Galaktosidase vanaf Escherichia coli is dieselfde as laktase in mense en beskik oor die vermoë om laktose te bind en te hidroliseer. 'n Gebrek aan laktase kom algemeen voor en ongeveer 70 % van die wêreldbevolking ly hieraan. Laasgenoemde het daartoe gelei dat daar meer druk as vantevore op die voedselproduksie industrie is om 'n metode te ontwikkel waarmee die hidrolise van die disakkaried laktose in melk moontlik sal wees asook die verwydering van die oorblywende aktiewe ensiem. In hierdie tesis word 'n nuwe metode beskryf wat biospesi ek en goed gekarakteriseer is vir die verwydering van laktose vanuit 'n laktose bevattende oplossing. Die E537D gemuteerde weergawe van ß-Galaktosidase, wat beskik oor 'n baie laer aktiwiteit as die wildetipe asook die vermoë om laktose biospesi ek vir langer periodes te bind, is kovalent geïmmobiliseer op kommersieel beskikbare magnetiese nanopartikels (fluidMAG-Amine) via twee koppelingsstrategieë. Glutaraldehied is 'n kruisbindingsagent wat met amino groepe reageer, terwyl EDC 'n koppelingsagent is wat karboksie groepe aktiveer. Hierdie agente word algemeen gebruik vir die binding van biomolekules aan soliede matrikse. Die kovalent gekoppelde fluidMAG-E537D ß-Galaktosidase partikels is gekarakteriseer met betrekking tot behoue ensimatiese aktiwiteit en vermoë om laktose te bind en sies te verwyder vanuit 'n oplossing wat laktose bevat deur 'n eksterne magneetveld op die ensiem-partikel kompleks in oplossing toe te pas, nadat die binding van laktose plaasgevind het. Elke komponent van hierdie funksioneel geïmmobiliseerde ensiemkomplekse is ondersoek en geoptimaliseer met die doel om by te dra tot die ontwikkeling van 'n nuwe tegniek wat bekostigbaar en eenvoudig is vir die verwydering van laktose vanuit 'n oplossing vir die uiteindelike gebruik in die produksie van laktose-vrye melk. Resultate het getoon dat die glutaraldehied metode van ß-Gal kruisbinding op fluidMAG-Amine verkies word aangesien dit 'n verhoogde draerkapasiteit van proteïene op die partikels moontlik maak. Die glutaraldehied gekoppelde proteïene beskik ook oor twee keer meer aktiwiteit as die EDC gekoppelde proteïene. Die glutaraldehied gekoppelde fluidMAG-E537D ß -Gal kon 34 % van die laktose teenwoordig in 'n 0.2 nmol/L laktose oplossing sies verwyder. Hierdie het dus die potensiële gebruik van hierdie nuwe metode in die voedselproduksie industrie bevestig.

The constant growth in population worldwide over the past decades continues to put forward the need to provide access to safe, clean water to meet human needs. There is a need for cost-effective technologies for water and wastewater treatment that can meet the global demands and the rigorous water quality standards and at the same maximizing pollutant efficiency removal. Current remediation technologies have failed in keeping up with these factors without becoming cost-prohibitive. Nanotechnology has recently been sought as a promising option to achieve these goals. The use of iron oxide magnetic nanoparticles as nanoadsorbents has led to a new class of magnetic separation strategies for water treatment. We have developed magnetic nanocomposite systems able to capture polychlorinated biphenyls (PCBs), as model organic pollutants, in aqueous solution, providing a cost-effective water remediation technique. Two distinct methods were employed to develop these polyphenolic nanocomposite materials. The polyphenolic moieties were incorporated to create high affinity binding sites for organic pollutants within the nanocomposites. The first method utilized a surface initiated polymerization of polyphenolic-based crosslinkers and co-monomers on the surface of iron oxide magnetic nanoparticles to create a core-shell nanocomposite. The second method utilized a bulk polymerization method to create macroscale films composed of iron oxide nanoparticles incorporated into a polyphenolic-based polymer matrix, which were then processed into microparticles. Both methods produce nanocomposite materials that can bind chlorinated organics, can rapidly separate bound organics from contaminated water sources using magnetic decantation, and can use thermal destabilization of the polymer matrix for contaminant release and material regeneration. The polyphenol functionalities used to bind organic pollutants were quercetin multiacrylate (QMA) and curcumin multiacrylate (CMA), which are acrylated forms of the nutrient polyphenols quercetin (found in berries) and curcumin (found in turmeric), both with expected affinity for chlorinated organics. The affinity of these novel materials for PCB 126 was evaluated at equilibrium conditions using a gas chromatography coupled to electron capture detection (GC-ECD) for quantification purposes, and the data was fitted to the nonlinear Langmuir model to determine binding affinity (KD) and maximum biding capacity (Bmax). The KD values obtained demonstrated that the presence of the polyphenolic-based moieties, CMA and QMA, as crosslinkers enhanced the binding affinity for PCB 126, expected to be a result of their aromatic rich nature which provides sites for π – π stacking interactions between the nanoparticle surface and the PCBs in solution. These values are lower that the reported affinity coefficients for activated carbon, which is the gold standard for capture/binding of organic contaminants in water and waste water treatment. Furthermore, upon exposure to an alternating magnetic field (AMF) for a period of 5 minutes, over 90% of the bound PCB on these materials was released, offering a low-cost regeneration method for the nanocomposites. Additionally, this novel regeneration strategy does not require the use of large volumes of harsh organic solvents that oftentimes become harmful byproducts. Overall, we have provided strong evidence that these novel nanocomposites have a promising application as nanoadsorbents for specific organic contaminants in contaminated water sources providing high binding affinities, a low-cost regeneration technique and are capable of withstanding use under environmental conditions offering a cost effective alternative to current remediation approaches.

We present a systematic methodology to functionalize magnetic nanoparticles through surface-initiated atom-transfer radical polymerization (ATRP). The magnetite nanoparticles are prepared according to the method proposed by Sun et al. (2004), which leads to a monodisperse population of ~ 6 nm particles stabilized by oleic acid. The functionalization of the nanoparticles has been performed by transforming particles into macro-initiators for the ATRP, and to achieve this two different routes have been explored. The first one is the ligand-exchange method, which consists of replacing some oleic acid molecules adsorbed on the particle surface with molecules that act as an initiator for ATRP. The second method consists in using the addition reaction of bromine to the oleic acid double bond, which turns the oleic acid itself into an initiator for the ATRP. We have then grown polymer brushes of a variety of acrylic polymers on the particles, including polyisopropylacrylamide and polyacrylic acid. The nanoparticles so functionalized are water soluble and show responsive behavior: either temperature responsive behavior when polyisopropylacrylamide is grown from the surface or PH responsive in the case of polyacrylic acid. This methodology has potential applications in the control of clustering of magnetic nanoparticles. / Singapore-MIT Alliance (SMA)