The semiconductor industry has been growing at a fast pace in the last several decades and this growth is expected to continue in the future. One process that is repeated several times in a microchip fabrication is the Chemical Mechanical Planarization (CMP). CMP is a critical process that must be employed after the metal deposition step to eliminate any topography over which the next layer must be processed. Today, copper interconnect is widely used. In addition to possess a high resistance to electro migration effects and low electrical resistivity, copper techniques require fewer (approximately 25%) processing steps. CMP and post-CMP cleaning processes are projected to account for 50 percent of the water consumed by fabrication's ultra pure water. While there are a variety of treatment schemes currently available for the removal of heavy metals from CMP wastewater streams, many introduce additional chemicals to the process, have large space requirement, or are not effective. Polyethyleneimine (PEI) is well known to use in the ion metal affinity chromatography (IMAC) due to the great metal ion binding abilities. While work has been conducted on the use of PEI on membrane filtration for binding metals from industrial wastewaters, the experiments performed in this research are novel with respect to the waste (Cu CMP) treated as well as the method of packed bed column treatment. This research focused primarily on the study of an alternative technique to remove both metal ions and metal-chelated complexes from Cu CMP wastewater streams. Not only copper, wastewater often contains chelating agents, surfactant, organic compounds, and inhibitors. Thus, most of the time copper ions form complexes with chelating agents, which made typical ion exchange resins ineffective. The work, then, explored the effect of components typically found in Cu CMP waste streams on the binding of copper ions to PEI. The competitive binding of copper between PEI and other complexing agents were also investigated. A secondary focus of this study was to fully develop and characterize the column performance and behavior. This includes the understanding of the chemistry of CMP waste characterization. This treatment technique using a PEI packed bed column showed great copper binding capacity. The column is capable of removing Cu CMP waste streams, which contain both copper ions and copper complexes, due to the unique ability of PEI that can play both cation and anion exchanger roles. This waste treatment technique is feasible for the semiconductor industry as large volumes of copper contaminated solutions from actual waste can be concentrated twelve-fold for metal recovery using hydrochloric acid. The adsorbent can be regenerated more than hundred of times with changing in the performance and the reproducibility.

Due to recent advances in molecular biology and genomic research, numerous diseases have been given their genetic identities for which gene therapy may be a possible prescription. Gradually, the development of viral and non-viral vectors to translocate genes has become a bottleneck. For non-viral vectors, polyethylenimine (PEI) is considered as a potential vector candidate for gene delivery because of its ability to compact DNA and its intrinsic pH buffering capacity. PEI and its derivates have been widely tested in both in-vitro and in-vivo gene transfection experiments. The progress is limited due to the lack of a better understanding of the intracellular mechanism. So far, their cytotoxicity is relatively high and gene transfection efficiency is low. This study was designed to modify PEI and optimize its cytotoxicity and gene transfection efficiency. / During the complexes formation, both LLS and zeta-potential were used to follow the process. The results showed that most of anionic DNA are complexed by cationic PEI-based polymers when the molar ratio of nitrogen from PEI to phosphate from DNA (N:P) reaches ∼3, but the gene transfection reaches the highest efficiency when N:P ∼10. When N:P > 3, there exist two population of PEI chains in the solution mixture: bound to DNA and free in the solution. The bound PEI chains condense and protect DNA. Our current study confirms that it is those free PEI chains that play a vital role in promoting the gene transfection. Our preliminary data shows that the promotion mainly occurs in the intracellular space. The detailed mechanism is still lacking at this moment. Nevertheless, our finding leads to a totally different way in the development of non-viral vectors. / Further, we grafted PEI with polyethylene glycol (PEG), respectively via a reductive disulfide -S-S- and a non-degradable -C-C- bond to form two copolymer vectors. A comparative study shows that the polyplexes formed between the two copolymers and DNA are more stable than that formed between unmodified PEI and DNA under the physiological condition, presumably because the grated PEG chains form a protective hydrophilic shell on the PEI/DNA polyplexes. However, PEGylation reduces the internalization of the copolymer/DNA polyplexes in in-vitro experiments. For the two copolymer vectors, PEG-SS-PEI is 2-8 times more effective than its counterpart (PEG-CC-PEI) in the gene transfection, presumably due to the cleavage of the grafted PEG chains inside the reductive cytosol, which promotes the release and translocation of DNA. Our results demonstrate that using the disulfide as a linker is a promising approach to overcome the PEGylation dilemma in the development of low cytotoxic and high efficient non-viral polymeric vectors. / It has been known that short PEI chains are less toxic, but long chains are more effective in gene transfection. Therefore, we decide to use the disulfide bond (-S-S-) to extend short PEI chains to increase efficiency and also utilize the reductive cytosol environment to cleave such extended PEI chains to reduce their cytotoxicity inside the cell. Laser light scattering (LLS) was used to in-situ monitor the linking reaction between short PEI chains (M w = 2000 g/mol) and dithiobis(succinimidyl propionate) (DSP). The molar mass and crosslinking degree of the extended PEI chains was controlled by either the amounts or the adding rate of DSP. A comparative study of two linked PEI samples (PEI-7K-L and PEI-400K-L, respectively with M w = 6.5 x 103 and 3.8 x 10 5 g/mol) reveals that cytotoxicity and gene transfection efficiency of such extended PEI chains are related to the chain length and structure. Namely, PEI-7K-L with an extended chain structure is less cytotoxic and 2--10 times more effective in the gene transfection than the "golden standard" (PEI25K) and the widely used commercial vector, Lipofectamine 2000RTM. Comparatively, PEI-400K-L with a spherical microgel structure is ineffective in spite of its non-toxicity. Our study clearly demonstrates that a proper control of the chain length and structure is important. / by Deng, Rui. / Adviser: Chi Wu. / Source: Dissertation Abstracts International, Volume: 72-04, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Yue, Yanan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 62-63). / Abstract also in Chinese. / ABSTRACT (Chinese) --- p.i / ABSTRACT --- p.iii / CONTENT --- p.v / ACKNOWLEDGMENT --- p.vii / ABBREVIATIONS --- p.viii / Chapter CHAPTER 1 --- Introduction and Background / Chapter 1.1 --- Methods of Gene Delivery --- p.1 / Chapter 1.1.1 --- Viral Delivery Systems --- p.2 / Chapter 1.1.2 --- Non-Viral Delivery Systems --- p.3 / Chapter 1.2 --- The Gene-delivery Problems --- p.7 / Chapter 1.2.1 --- Extracellular Barriers --- p.8 / Chapter 1.2.2 --- Intracellular Barriers --- p.10 / Chapter 1.3 --- Polymer-Mediated Systems for Gene Delivery --- p.13 / Chapter 1.3.1 --- Polyethylenimine (PEI)-Based Vectors --- p.13 / Chapter 1.3.2 --- Cyclodextrin-Based Vectors --- p.15 / Chapter 1.4 --- Objective and Main Achievements --- p.16 / Chapter 1.5 --- References --- p.18 / Chapter CHAPTER 2 --- Effect of Free Polyethylenimine-Mediated Polycations on Gene Delivery: Fundamentals and Vital Factors / Chapter 2.1 --- Introduction --- p.24 / Chapter 2.2 --- Experimental Section --- p.25 / Chapter 2.3 --- Results and Discussions --- p.29 / Chapter 2.3.1 --- Fundamentals --- p.29 / Chapter 2.3.2 --- Vital Factors for the Efficacy of Free Chains --- p.37 / Chapter 2.4 --- Conclusions --- p.42 / Chapter 2.5 --- References --- p.42 / Chapter CHAPTER 3 --- Effect of Free Polyethylenimine-Mediated Polycations on Gene Delivery: Mechanistic Study / Chapter 3.1 --- Introduction --- p.44 / Chapter 3.2 --- Experimental Sections --- p.46 / Chapter 3.3 --- Results and Discussion / Chapter 3.3.1 --- Potential Effect of Free PEI Chains on Cellular Uptake --- p.49 / Chapter 3.3.2 --- Potential Effect of Free PEI Chains on Endolysosomal Release --- p.51 / Chapter 3.3.3 --- Exploration on Proton Sponge Hypothesis --- p.53 / Chapter 3.3.4 --- Interactions of PEI-based Polycations and Phospholipid Membranes --- p.55 / Chapter 3.4 --- Conclusions --- p.61 / Chapter 3.5 --- References --- p.62

Many biopharmaceuticals, already approved for sale or currently under development, are post-translationally modified proteins, such as recombinant monoclonal antibodies or recombinant hormones. These are generally expressed in continuous (stable) mammalian cell lines, which are capable of long-term, commercial-scale production of recombinant proteins of the highest complexity. Yet, the development of a stable cell line capable of expressing heterologous proteins is very costly and can take up to 9–15 months. Therefore, transient gene expression (TGE) in animal cells has become the method of choice for many researchers who wish to obtain small to moderate quantities (1-500 mg) of novel complex recombinant proteins for further functional and structural characterisation within weeks of cDNA discovery. TGE is more cost-effective than the time-consuming establishment of stable cell clones, but a key factor in ensuring that these transient systems have practical application is the availability of efficient and robust transfection agents/methods. While chemical transfection methods currently dominate transient systems, the underlying fundamentals such as the formation of DNA complexes or their mode of function are not fully understood and the characteristics of the complexes and their subsequent ability to transfect cells are variable. This often renders the development of a successful transfection protocol for a new cell line random and researchers frequently have to resort to a trial-and-error approach, testing different media and/or conditions during DNA complex formation, as well as having to fine-tune the cell culture regime pre-, during, and post-transfection. This thesis aimed to explore novel transfection agents and develop DNA complex structure/property—transfection efficiency relationships for these reagents. Two different chemical approaches to transient transfection were investigated: i) a recently suggested inorganic nanoparticle based transfection system which utilises the anion exchange capacity of nanoparticles of a particular family of anionic clays, layered double hydroxides (LDHs), and ii) a modified polyethyleneimine (PEI)-based system, which aimed to reduce the inherent cytotoxicity of high molecular weight (MW) PEI, which is a very effective transfection agent, by constructing high MW mimics from low MW building blocks that are linked to each other via biodegradable linkers such as azomethine groups. While the LDH nanoparticles failed to give satisfactory transfection results for plasmid DNA, they were able to functionally deliver smaller nucleic acids such as siRNA. A mechanism different to that currently accepted for the transfection of mammalian cells with plasmid DNA using LDH nanoparticles as carriers is proposed. The modified polymeric transfection agents were shown to result in significantly less cell death, while maintaining the ability to transfect mammalian cells with almost similar efficiency to that obtained with high MW polyethyleneimine. Generic DNA complex structure/property—transfection efficiency relationships were developed by systematically studying the influence of particle size and zeta potential on transfection results.

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DNA vaccines in larger animals, such as horses, are generally less effective and elicit significantly weaker immune responses, than in small animal model systems. To provide optimal protection against pathogenic microorganisms, the induction of both humoral and cellular immune responses from DNA vaccination may be necessary. One limitation to DNA immunization in the horse is the difficulty in generating high levels of antigen-specific antibody and CTL responses. Previous work in the laboratory has demonstrated that expression constructs containing native sequences encoding the surface unit (SU) envelope glycoprotein (pCiSU) of the Equine Infectious Anemia Virus (EIAV) are ineffective at stimulating immune responses in the horse. This was attributed to an unusual codon-usage bias of the EIAV genome that significantly limits the expression of SU sequences. Optimizing the codon usage of pCiSU (pSYNSU) in DNA vaccines stimulated low-titer immune responses in inoculated ponies. Another plausible explanation for the reduced effectiveness of these DNA vaccines may be transfection deficiency and low level expression elicited by plasmid vectors in the horse. These studies investigated if the addition of a cationic polymer, deacylated polyethyleneimine (PEI), and/or codon optimized molecular immune-stimulatory cytokines could augment the relatively weak immunogenicity of pSYNSU in DNA vaccination of horses/ponies. Administration of DNA in formulation with PEI resulted in the robust production of very long-lived humoral (15 months after vaccination) responses and induced cell-mediated IFN-y responses five days after immunization.. Additionally, the co-expression of a family of IL-15 cytokines expanded the repertoire of T cell recognition to SU-specific peptides, in terms of lymphoproliferation. DNA vaccination incorporating one IL-15 family member, IL-15 (SSLSS) significantly enhanced serum antibody levels of IgGA and IFN-y mRNA expression levels. These responses were distinctly different from results seen with vaccinates that received „naked‟ pSYNSU DNA vaccines. It is evident from these vaccine studies that PEI can enhance DNA vaccine-elicited antibody and CTL-associated responses in the horse and IL-15 (SSLSS) can dramatically augment these responses. These results demonstrate an important role for PEI in promoting the longevity of immune responses to genetic immunization, which has not been reported previously in any large animal model.

The evolution of nanotechnology over the past 20 years has allowed researchers to use a wide variety of techniques and instruments to synthesize and characterize new materials on the nano scale. Due to their size, these nano materials have a wide variety of interesting properties, including, high tensile strength, novel electronic and optical properties and high surface areas. In any absorption system, a high surface areas is desirable, making carbon nano materials ideal candidates for use in absorption systems. To that end, we have prepared a variety of nano carbons, single walled carbon nanotubes, multi walled carbon nanotubes, graphite intercalation compounds, graphite oxide, phenylalanine modified graphite and fullerenes, for the absorption of carbon dioxide. These nano carbons are functionalized with the polymer, polyethyleneimine, and fully characterized using Raman spectroscopy, x-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy, solid state 13 C NMR, and thermogravimetric analysis. The carbon dioxide absorption potential of the PEI-nano carbons was evaluated using thermogravimetric analysis at standard room temperature and pressure. We have demonstrated the high gravimetric capacity of carbon dioxide capture on these materials with extremely high capacities for PEI-C 60 .

In this study we fabricated free standing multilayer films of polyelectrolyte complexes for potential use in tissue engineering of corneal stroma by using the layer-by-layer (LbL) approach. In the formation of these LbL films negatively charged, photocrosslinkable (methacrylated) hyaluronic acid (MA-HA) was used along with polycations polyethyleneimine (PEI) and poly(L-lysine) (PLL). Type I collagen (Col) was blended in with PLL for improving the water absorption and cell attachment properties of the films. It was shown that the LbL films could be easily peeled off from glass substrates due to the photocrosslinking of one of the LbL components, the hyaluronic acid. Film growth and composition were monitored with FTIR-ATR. Heights of peaks at 3383 cm-1, and 2958 cm-1increased along with the bilayer number confirming the polymer build-up. Film integrity and thickness were investigated by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). Films thicker than 5 bilayers (BLs) were found to be uniform in appearance and 10 BL (PEI/MeHA) films were calculated to be ca. 6 &mu / m thick. Atomic force microscopy (AFM) revealed that as the number of BLs increased, surface roughness decreased. Activity of methacrylated hyaluronic acid was shown by the increased resistance of photocrosslinked multilayer films against hydrolysis by hyaluronidase. Patterns could be created on the films by photocrosslinking further proving that the crosslinking step is successful. Since the ultimate goal was to construct a corneal stroma PEI/MA-HA films were tested with corneal stroma cells, keratocytes. Cell proliferation on PEI/MA-HA films was quite poor in comparison to TCPS. In order to improve the cell adhesion the tests were repeated with PLL/MA-HA. Collagen was added to decrease the hydrophilicity and introduce cell adhesion sequences (Arg-Gly-Asp, RGD) to improve cell proliferation on the films and thus PLL+Col/MA-HA films were also tested. Introduction of collagen to the PLL/MA-HA films was found to decrease water retention of the multilayer films and improve cell viability and proliferation. Col+PLL/MA-HA LbL thus appear to be a promising platform for tissue engineering, especially of corneal stroma.

Nowadays, there is an increasing risk of bacterial infections from bacteria strains resistant towards antibiotics. Thus, it is of utmost importance to research novel therapies which can overcome this difficulty. The presented thesis focuses on the preparation, characterization and antibacterial evaluation of polystyrene polymer nanomaterials (nanofiber membranes and nanoparticles) modified with compounds that can efficiently inhibit bacterial growth either by their nature (polyethyleneimine) or by photoactivation upon visible light excitation (NO- photodonors, photosensitizers) and consequent production of highly reactive inorganic bactericidal species, nitric oxide (NO) and singlet oxygen (O2(1 g)). All materials were fully characterized by several independent methods. The concentrations of NO and O2(1 g) were measured by amperometric and time-resolved spectroscopic techniques and by variety of chemical analytic procedures. Due to the presence of bactericidal species and the efficient photogeneration of NO and O2(1 g) at physiological conditions, all materials exhibit strong antibacterial action tested on a Gram-negative bacterial strain Escherichia coli. Hence, these functionalized polymer nanomaterials may be intriguing systems for medical-, biological-, or environmental- application where a...

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