Self-assembling peptides have emerged as new nanobiomaterials and received considerable attention in the areas of nanoscience and biomedical engineering. In this category are ionic-complementary peptides, which contain a repeating charge distribution and alternating hydrophobic and hydrophilic residues in the amino acid sequence, leading to the unusual combination of amphiphilicity and ionic complementarity. Although their self-assembled nanostructures have been successfully applied as scaffoldings for tissue engineering, novel materials for regenerative medicine and nanocarriers for drug and gene/siRNA delivery, aspects of the assembly process remain unclear. Since many of these applications involve peptide-modified interfaces and surfaces, a better understanding and control of the peptide assembly on a surface are very crucial for future development of peptide-based applications in nano-biotechnology. This thesis contains two major parts: (i) fundamental study of the assembly of a model ionic-complementary peptide EAK16-II on surfaces and (ii) potential applications of such a peptide in surface modification and nanofabrication. In the fundamental study, EAK16-II assembly on negatively charged mica was first investigated via in-situ Atomic Force Microscopy (AFM). It was found that EAK16-II nanofiber growth on mica is surface-assisted and follows a nucleation and growth mechanism involving two steps: (i) adsorption of nanofibers and fiber clusters (from the bulk solution) on the surface to serve as the seeds and (ii) fiber elongation from the active ends of the seeds. Such a process can be controlled by adjusting the solution pH since it modulates the adsorption of the seeds and the growth rates. Unlike what is observed on mica, EAK16-II formed well-ordered nanofiber patterns with preferential orientations at angles of 60° or 120° to each other on hydrophobic highly ordered pyrolytic graphite (HOPG) surfaces, resembling the crystallographic structure of the graphite. Nanofiber formation on HOPG is also surface-assisted and adopts a nucleation and growth mechanism that can be affected by solution pH. The pH-dependent adsorption of peptides to HOPG is attributed to the resulting changes in peptide hydrophobicity. It was also found that EAK16-II assembly can be induced by the mechanical force of a tapping AFM tip. It occurs when the tip cuts the adsorbed EAK16-II nanofibers into segments that then serve as seeds for new nanofiber growth. This finding allows one to locally grow nanofibers at specific regions of the surface. The tip cutting has been combined with the effect that solution pH has on peptide assembly to develop a new AFM lithography method to fabricate local patterned peptide nanostructures on HOPG. To study the use of EAK16-II for surface modification applications, the wettability and stability of the peptide-modified surfaces were characterized. EAK16-II-modified mica becomes slightly hydrophobic as the water contact angle increases from <10° to 20.3 ± 2.9°. However, the hydrophobicity of the HOPG surface is significantly reduced, as reflected in a contact angle change from 71.2 ± 11.1° to 39.4 ± 4.3°. The EAK16-II-modified mica surface is stable in acidic solution, while the modified HOPG surface is stable in both acidic and alkaline solutions. The peptide-modified HOPG shows potential as a biocompatible electrode for (bio)molecular sensing. The ability of EAK16-II to form nanofibers on surfaces has also promoted research on peptide-based metallic nanowire fabrication. Our approach is to provide EAK16-II with metal ion binding ability by adding a GGH motif to the C-terminus. This new peptide EAK16(II)GGH has been found to form one-dimensional nanofibers while binding to Cu2+ ions. The dimensions of the nanofibers were significantly affected by the nature of the anions (SO42-, Cl- and NO3-) in the copper salt solution. This work demonstrates the potential usage of EAK16-II for nanowire fabrication.

Self-assembling peptides have emerged as new nanobiomaterials and received considerable attention in the areas of nanoscience and biomedical engineering. In this category are ionic-complementary peptides, which contain a repeating charge distribution and alternating hydrophobic and hydrophilic residues in the amino acid sequence, leading to the unusual combination of amphiphilicity and ionic complementarity. Although their self-assembled nanostructures have been successfully applied as scaffoldings for tissue engineering, novel materials for regenerative medicine and nanocarriers for drug and gene/siRNA delivery, aspects of the assembly process remain unclear. Since many of these applications involve peptide-modified interfaces and surfaces, a better understanding and control of the peptide assembly on a surface are very crucial for future development of peptide-based applications in nano-biotechnology. This thesis contains two major parts: (i) fundamental study of the assembly of a model ionic-complementary peptide EAK16-II on surfaces and (ii) potential applications of such a peptide in surface modification and nanofabrication. In the fundamental study, EAK16-II assembly on negatively charged mica was first investigated via in-situ Atomic Force Microscopy (AFM). It was found that EAK16-II nanofiber growth on mica is surface-assisted and follows a nucleation and growth mechanism involving two steps: (i) adsorption of nanofibers and fiber clusters (from the bulk solution) on the surface to serve as the seeds and (ii) fiber elongation from the active ends of the seeds. Such a process can be controlled by adjusting the solution pH since it modulates the adsorption of the seeds and the growth rates. Unlike what is observed on mica, EAK16-II formed well-ordered nanofiber patterns with preferential orientations at angles of 60° or 120° to each other on hydrophobic highly ordered pyrolytic graphite (HOPG) surfaces, resembling the crystallographic structure of the graphite. Nanofiber formation on HOPG is also surface-assisted and adopts a nucleation and growth mechanism that can be affected by solution pH. The pH-dependent adsorption of peptides to HOPG is attributed to the resulting changes in peptide hydrophobicity. It was also found that EAK16-II assembly can be induced by the mechanical force of a tapping AFM tip. It occurs when the tip cuts the adsorbed EAK16-II nanofibers into segments that then serve as seeds for new nanofiber growth. This finding allows one to locally grow nanofibers at specific regions of the surface. The tip cutting has been combined with the effect that solution pH has on peptide assembly to develop a new AFM lithography method to fabricate local patterned peptide nanostructures on HOPG. To study the use of EAK16-II for surface modification applications, the wettability and stability of the peptide-modified surfaces were characterized. EAK16-II-modified mica becomes slightly hydrophobic as the water contact angle increases from <10° to 20.3 ± 2.9°. However, the hydrophobicity of the HOPG surface is significantly reduced, as reflected in a contact angle change from 71.2 ± 11.1° to 39.4 ± 4.3°. The EAK16-II-modified mica surface is stable in acidic solution, while the modified HOPG surface is stable in both acidic and alkaline solutions. The peptide-modified HOPG shows potential as a biocompatible electrode for (bio)molecular sensing. The ability of EAK16-II to form nanofibers on surfaces has also promoted research on peptide-based metallic nanowire fabrication. Our approach is to provide EAK16-II with metal ion binding ability by adding a GGH motif to the C-terminus. This new peptide EAK16(II)GGH has been found to form one-dimensional nanofibers while binding to Cu2+ ions. The dimensions of the nanofibers were significantly affected by the nature of the anions (SO42-, Cl- and NO3-) in the copper salt solution. This work demonstrates the potential usage of EAK16-II for nanowire fabrication.

Surface grafting and modification of poly(acrylic acid) (PAA) were performed on nylon 6,6 carpet fibers to achieve permanent stain and soil resistance. PAA was grafted to nylon and modified with 1H, 1H-pentadecafluorooctyl amine (PDFOA) using an amidation agent, 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMTMM). The first goal was to optimize acrylamide modification of PAA in solution. Aqueous reactions with taurine, hydroxyethyl amine, and butyl amine progressed ~100%, while PDFOA reactions in MeOH progressed ~80%. Reaction products precipitated at 77% butyl or 52% PDFOA acrylamide contents. The second goal was to optimize the PAA grafting process. First, PAA was adsorbed onto nylon 6,6 films. Next, DMTMM initiated grafting of adsorbed PAA. PAA surface coverage was ~78%, determined by contact angle analysis of the top 0.1-1 nm and x-ray photoelectron spectroscopy (XPS) analysis of the top 3-10 nm. The third goal was to modify PAA grafted nylon films with butyl amine and PDFOA. Randomly methylated beta-cyclodextrin (RAMEB) solubilized PDFOA in water. Contact angle detected ~ 100% surface reaction for each amine, while XPS detected ~77% butyl amine (H2O) and ~50% for PDFOA (MeOH or H2O pH=7) reactions. In H2O pH=12, the PDFOA reaction progressed ~89%, perhaps due to greater efficiency, access and solubility. The fourth goal was to perform surface depth profiling via angle-resolved XPS analysis (ARXPS). The PAA surface coverage from contact angle and XPS was confirmed. Further, adsorbed PAA was thicker than grafted PAA, supporting the theory that PAA adsorption occurs in thick layers onto nylon followed by DMTMM-activated spreading and grafting of thinner PAA layers across the surface. The PDFOA reaction in MeOH produced a highly fluorinated but thin exterior and an unreacted PAA interior. The PDFOA reaction in H2O pH=12 produced a completely fluorinated exterior and highly fluorinated interior. Thus surface modification levels from contact angle and XPS were confirmed. The final goal was to PAA-graft and PDFOA-modify nylon 6,6 fabrics and carpets. PDFOA modification achieved significant water and oil repellency. Stainblocking was slightly improved for ionized PAA-g-nylon and greatly improved for PDFOA-modified PAA-g-nylon. However, traditional stainblockers may be necessary to completely prevent dye penetration into carpet tufts.

Arsenic and perchlorate are two types of emerging contaminants commonly found in various water bodies worldwide. Therefore, the development of effective removal technologies has become an important issue today. To this end, the following research studies were conducted. First, trimethylchlorosilane (TMCS) was used for the surface modification of a laboratory-prepared outside-in tubular TiO2/Al2O3 composite membrane aiming at enhancing the filtration performance of the said membrane layer. Second, the TMCS-modified tubular ceramic membrane coupled with the simultaneous electrocoagulation/ electrofiltration (EC/EF) process was tested and evaluated their combined performance in the remediation of arsenic- and perchlorate-spiked waters and one actual As-contaminated groundwater. In this research, the results of a preliminary electrocoagulation study have indicated that aluminum outperformed iron as the anode material. Thus, aluminum was selected as the sacrificial anode for the EC/EF tests throughout this work. In the course of various EC/EF testing, the removal efficiencies of the target contaminant in the test water specimens were compared for the tubular TiO2/Al2O3 composite membranes with and without surface modification. Also evaluated included the permeate flux, unit mass of target contaminant removed, and relevant power consumption. Though surface modification might not yield a better removal efficiency of the concerned contaminant, it gave rise to a greater permeate flux resulting in a greater removed mass of the contaminant for each of the synthetic wastewaters. Meanwhile, lower power consumption was found as compared with the case of no surface modification. As for the actual As-contaminated groundwater, the optimal EC/EF conditions for the tubular composite membrane without surface modification could low the As concentration to meet the local irrigation water quality criteria.

Microfluidics emerged during the early 1990s with channel networks in silicon or glass. Microprocessing of these materials is labor-intensive and time-consuming, it requires sophisticated equipment in a clean room, and often involves hazardous chemicals. The subsequent use of polymer greatly simplified the fabrication of microchips and led to the rapid development of the field. Polymer such as poly(dimethylsiloxane) (PDMS), has other attractive properties, such as being elastic (easy to make efficient microvalves), permeable to gases, and compatible with culturing biological cells. Despite these advantages, applications of PDMS chips are severely limited by a few drawbacks that are inherent to this material: (i) strong adsorption of molecules, particularly large biomolecules, onto its surface; (ii) absorption of nonpolar and weakly polar molecules into PDMS bulk; (iii) leaching of small molecules from PDMS bulk into solutions; and (iv) incompatibility with organic solvents. To overcome all these problems, Teflon plastics seem to be the perfect solution. They are well-known for their superior inertness to almost all chemicals and all solvents; they also show excellent resistance to molecular adsorption and molecule leaching from the polymer bulk to solutions. However, Teflon has a high chemical inertness of the surface, which is restricted the bonding temperature (>260¢XC).It is not conducive to the low-temperature packaging process. This study presents a simple and rapid process for sealing Teflon-based microfluidic chip at a temperature of 140oC which is lower than typical bonding temperature of 260oC. A simple ammonium plasma treatment is used to enhance the surface energy of Teflon substrates such that the bonding temperature can be greatly reduced. Results indicate that the ammonium plasma treated Teflon substrates can be sealed using hot press bonding at a temperature of 140oC for 20 min. The measured iv bonding strength for the Teflon-based microfluidic devices is higher than those bonded at a reported temperature of 260oC for 60 min. It shows the measured contact angle for the Teflon substrates treated with different plasmas. Results indicated that the ammonium hydroxide plasma exhibited the best wettability property and the contact angle reached the minimum value of 45o after 5 min of treatment. The ESCA analysis showed the best Defluorination by ammonium plasma. The fluorine/carbon atomic ratio degraded from 1.96 to 1.10 by 5 minutes. The measured bonding strength for the Teflon substrates bonded with different surface activation protocols. Results showed that the bonding strength was enhanced upto 93% after the plasma treatment. The plasma treatment not only enhanced the bonding strength but also reduced the bonding temperature and time. The measured surface roughness only increased 15¡Ó5 nm (Ra) after the plasma treatment, which is acceptable for most applications in microfluidic systems. Finally, the fluorescence optical architecture and cross-chip successfully detected and isolated £XX-174 fragment of DNA samples confirmed the Teflon substrate for the emerging microfluidic plastic chip. The developed method provides a simple and rapid way to fabricate Teflon-based microfluidic devices.

In this study, pH-sensitive poly(acrylamide-co-acrylic acid) hydrogels were synthesized as controlled release systems in the presence of N,N-methylene bisacrylamide as crosslinker and ammonium persulfate as initiator. A set of hydrogels were used in the form they were prepared. One set of hydrogels were prepared as porous networks by incorporating sodium chloride into the reaction medium and then leaching of it after the completion of polymerization reaction. Two sets of hydrogels were modified by argon-plasma at different discharge powers. Hydrogels were characterized by 13C-NMR, XPS, SEM, ATR-FTIR, ESR as well as equilibrium degree of swelling (EDS) and contact angle measurements. Prepared hydrogels were loaded with a model antibiotic, ciprofloxacin-HCl (CPFX), and in-vitro release of CPFX from hydrogel matrices were examined in buffer solutions of varying pH values. There are two factors determining the release rates of CPFX / one is the pH-dependent solubility of CPFX and the other is EDS of the hydrogel samples. For porous samples drug loading and release rates were higher when compared to the control samples and CPFX solubility dominated over release kinetics. Plasma treatment resulted in prolonged release rates in acidic medium.

In this study calcium carbonate (CaCO3) particles are surface modified by using plasma polymerized natural gas and effects of surface modification of CaCO3 filler on mechanical properties of CaCO3-PP composites are investigated. Different combination of plasma factors / RF power, natural gas flow rate, and plasma discharge durations, are investigated. Mechanical properties such as tensile strength and Young&rsquo / s Modulus are measured by tensile testing machine. Storage modulus and loss modulus measurements are done by DMA. Some information about structures generated by natural gas plasma surface modification is obtained by FTIR tests. The tensile fracture surfaces of prepared composites are investigated by using SEM micrographs. It is concluded that, despite some enhancement obtained in the moduli / the technique of natural gas plasma surface modification of CaCO3 particles did not introduce significant improvement in mechanical properties of composite as expected. This result may partially be attributed to selected plasma parameters (i.e., flow rate, RF power, and discharge duration).

Thrombus formation and blood coagulation is a major problem associated with blood contacting products such as catheters, vascular grafts and artificial hearts. An intense research is being conducted towards the synthesis of new hemocompatible materials and mdifications of surfaces with biological molecules. In this study, polyurethane (PU) films were synthesized in medical purity from diisocyanate and polyol without using any other ingredients and the chemical, thermal and mechanical properties were characterized by solid state NMR, FTIR, GPC, mechanical tests, DMA and TGA. The surfaces of PU films were modified by covalent immobilization of different molecular weight heparins / low molecular weight heparin (LMWH) and unfractionated heparin (UFH) and these surfaces were examined by ESCA, ATR-FTIR, AFM and contact angle goniometer. Cell adhesion studies were conducted with whole human blood and examined by SEM. The effects of different types of heparins on blood protein adsorption and on platelet adhesion were analyzed by electrophresis and SEM, respectively. The surfaces of the UFH immobilized polyurethane films (PU-UFH) resulted in lesser red blood cell adhesion in comparison to LMWH immobilized polyurethane film surfaces (PU-LMWH). When the PU films were treated with blood plasma, the surfaces modified with two different heparin types showed a clearly different protein adsorption behavior especially in the early stage of blood plasma interaction. PU-LMWH samples showed about three times less protein adsorption compared to PU-UFH samples. The morphologies of platelets adhered on material surfaces demonstrated differences / such as PU-UFH had clusters with some pseudopodia extensions, while PU-LMWH had round shaped platelets with little clustering. PU surfaces modified by immobilization of LMWH and UFH, demonstrated promising results for the improvement of non-thrombogenic devices and surfaces.

Magnetic nanoparticles have been used in many areas owing to their variable characteristic behaviors. Among these iron oxide nanoparticles are one of the mostly preferred type of nanoparticles. In this study Fe3O4, namely magnetite, which is one type of magnetic iron oxide nanoparticles was used. Magnetite nanoparticles with a narrow size distribution were prepared in aqueous solution using the controlled coprecipitation method. They were characterized by electron microscopic methods (SEM and TEM), crystal structure analysis (XRD), particle size analyzer, vibrating sample magnetometer (VSM) and Raman spectrometry. The nanoparticles were coated with a thin (ca 20 nm) silica shell utilizing the hydrolysis and the polycondensation of tetraethoxysilane (TEOS) under alkaline conditions in ethanol. The presence of silica coating was investigated by energy dispersive X-ray spectrometer (EDX) measurement. After surface modification with an amino silane coupling agent, (3-Aminopropyl)triethoxysilane, histidine was covalently linked to the amine group using glutaraldehyde as cross-linker. Carbonyl complexes of rhenium [Re(CO)3(H2O)3]+ was prepared through reductive carboxylation utilyzing gaseous carbon monoxide as a source of carbonyl and amine borane (BH3NH3) as the reducing agent. The complex formation was followed by HPLC- ICP-MS system and 95% conversion of perrhanete into the complex was achieved. The magnetic nanoparticles were then labeled with the Re complex with a yield of 86.8% through the replacement of labile H2O groups with imidazolyl groups. Thus prepared particles were showed good stability in vitro. Herein rhenium was selected as a surrogate of radioactive 99mTc. However radioactive isotopes of rhenium (186-Re and 188 Re) is also used for radioactive therapy.

The magnetic separation approach has several advantages compared with conventional separation methods / it can be performed directly in crude samples containing suspended solid materials without pretreatment, and can easily isolate some biomolecules from aqueous systems in the presence of magnetic gradient fields. This thesis focused on the development of new class of magnetic separation material particularly useful for the separation of histidine-tagged proteins from the complex matrixes through the use of imidazole side chains of histidine molecules. For that reason surface modified cobalt ferrite nanoparticles which contain Ni-NTA affinity group were synthesized. Firstly, cobalt ferrite nanoparticles with a narrow size distribution were prepared in aqueous solution using the controlled coprecipitation method. In order to obtain small size of agglomerates two different dispersants, oleic acid and sodium chloride, were tried. After obtaining the best dispersant and optimum experimental conditions, ultrasonic bath was used in order to decrease the size of agglomerates. Then, they were coated with silica and this was followed by surface modification of these nanoparticles by amine in order to add functional groups on silica shell. Next, &ndash / COOH functional groups were added to silica coated cobalt ferrite magnetic nanoparticles through the NH2 groups. After that N&alpha / ,N&alpha / -Bis(carboxymethyl)-L-lysine hydrate, NTA, was attached to carboxyl side of the structure. Finally, nanoparticles were labeled with Ni (II) ions. The size of the magnetic nanoparticles and their agglomerates were determined by FE-SEM images, particle size analyzer, and zeta potential analyzer (zeta-sizer). Vibrational sample magnetometer (VSM) was used to measure the magnetic behavior of cobalt ferrite and silica coated cobalt ferrite magnetic nanoparticles. Surface modifications of magnetic nanoparticles were followed by FT-IR measurements. ICP-OES was used to find the amount of Ni (II) ion concentration that was attached to the magnetic nanoparticle.