Reversible changes in the self-organization of polysoaps may be induced by controlling their charge numbers via covalently bound redox moieties. This is illustrated with two viologen polysoaps, which in response to an electrochemical stimulus, change their solubility and aggregation in water, leading from homogeneously dissolved and aggregated molecules to collapsed ones and vice verse. Using the electrochemical quartz crystal microbalance (EQCM), it could be shown that the reversibility of this process is better than 95% in 16 cycles. /

In order to develop blood biocompatible materials a heparin surface and a phosphorylcholine (PC) functionalized polymer surface were characterized using photoelectron spectroscopy (PES). The formation of the heparin surface was studied by quartz crystal microbalance with dissipation monitoring (QCM-D). This heparin surface consists of heparin conjugates deposited on a conditioning layer, applied once or twice. The PC functionalized polymer, poly(trimethylene carbonate), was linked to a silicon substrate through 3-amino- propyltrimethoxysilane (APTMS), also studied using PES. Synchrotron radiation based PES showed that the thicker heparin film resulted in complete coverage of the substrate, while the thinner did not. This could explain the difference in blood biocompatibility between the two films, as observed by others. It was also found that the heparin chains bend down towards the substrate (under vacuum). For the thinner heparin film the modifications, resulting from extensive irradiation of the sample, were studied with synchrotron radiation based PES. This was done at a pressure of about 10-7 mbar and in 0.5 mbar water vapor. It was found that the modification is slower under water vapor than at low pressures and that the damaged film incorporates water upon exposure. The heparin coating was found to be stable and wear resistant enough to still be present on artificial heart valves after three weeks testing in circulating plasma. It then had about the same antithrombin uptake as a non-tested surface. The film was, however, partly destroyed by the durability test and plasma proteins were deposited. The PC functionalized, APTMS linked polymer was found to be much shorter than could be expected from random reactions. One plausible explanation is an interaction between the PC group and the silane surface, favoring aminolysis close to the PC group. This is consistent with our finding that the PC group bends down towards the surface.

A framework to compartmentalize microfluidic surfaces was developed. Substrates are separated from surface modifying agents with an intermediate binding layer (IBL). The IBL is comprised of two compounds which bind together using a non-covalent interaction; a host compound is immobilized on the substrate, and a guest compound is conjugated to the surface modifying agent. The primary benefit of the IBL architecture is adaptability: substrates and surface compounds become modular components with standard connectors. Beta-Cyclodextrin (BCD) and adamantane (AD) were selected as the model immobilized host and conjugated guest, respectively. A quartz crystal microbalance (QCM) was assembled and developed to study the BCD/AD complexation interaction. Kinetic, thermodynamic, and Langmuir isotherm data were reported for AD-derivatives binding with immobilized BCD. QCM was also used to investigate neutravidin (NA) binding onto AD-PEG and AD-PEG-biotin coatings immobilized to t-BCD surfaces. QCM was an effective platform to validate the use of BCD/AD as the IBL interaction prior to microfluidic implementation. The BCD/AD IBL was successfully demonstrated in a microfluidic environment. Microfluidic devices were fabricated using the soft-lithographic technique. Adapted surface modifications were visualized using fluorescein isothiocyanate (FITC) probes within the microfluidic device and detected using confocal laser scanning microscopy (CLSM). Surface modifications were applied to demonstrate the fundamental functions of surface passivation, specific binding, and visualization using the IBL architecture. Consistent with QCM data, AD-PEG passivated the surface and AD-PEG-biotin specifically bound NA to the BCD surface. Thus, an adaptable surface modification architecture for microfluidic applications was developed and demonstrated.

A modified Split Hopkinson Pressure Bar (SHPB) system is used to determine the mechanical properties of soft and ultra-soft materials. An aluminum bar is introduced to reduce the impedance mismatch between the test system and sample. The small signal of the forces was measured by a quartz crystal gauge system. The high precision Laser gap gauge (LGG) system was used to measure the deformation of samples. The compressive tests of Cemented Paste Backfill (CPB), fresh CPB and Polymethylmethacrylate (PMMA) and the fracture toughness tests of PMMA were conducted to approve the legitimacy of our modified SHPB system. From these experiments, the efficiency and economy of the modified SHPB system were attested.

A modified Split Hopkinson Pressure Bar (SHPB) system is used to determine the mechanical properties of soft and ultra-soft materials. An aluminum bar is introduced to reduce the impedance mismatch between the test system and sample. The small signal of the forces was measured by a quartz crystal gauge system. The high precision Laser gap gauge (LGG) system was used to measure the deformation of samples. The compressive tests of Cemented Paste Backfill (CPB), fresh CPB and Polymethylmethacrylate (PMMA) and the fracture toughness tests of PMMA were conducted to approve the legitimacy of our modified SHPB system. From these experiments, the efficiency and economy of the modified SHPB system were attested.

A framework to compartmentalize microfluidic surfaces was developed. Substrates are separated from surface modifying agents with an intermediate binding layer (IBL). The IBL is comprised of two compounds which bind together using a non-covalent interaction; a host compound is immobilized on the substrate, and a guest compound is conjugated to the surface modifying agent. The primary benefit of the IBL architecture is adaptability: substrates and surface compounds become modular components with standard connectors. Beta-Cyclodextrin (BCD) and adamantane (AD) were selected as the model immobilized host and conjugated guest, respectively. A quartz crystal microbalance (QCM) was assembled and developed to study the BCD/AD complexation interaction. Kinetic, thermodynamic, and Langmuir isotherm data were reported for AD-derivatives binding with immobilized BCD. QCM was also used to investigate neutravidin (NA) binding onto AD-PEG and AD-PEG-biotin coatings immobilized to t-BCD surfaces. QCM was an effective platform to validate the use of BCD/AD as the IBL interaction prior to microfluidic implementation. The BCD/AD IBL was successfully demonstrated in a microfluidic environment. Microfluidic devices were fabricated using the soft-lithographic technique. Adapted surface modifications were visualized using fluorescein isothiocyanate (FITC) probes within the microfluidic device and detected using confocal laser scanning microscopy (CLSM). Surface modifications were applied to demonstrate the fundamental functions of surface passivation, specific binding, and visualization using the IBL architecture. Consistent with QCM data, AD-PEG passivated the surface and AD-PEG-biotin specifically bound NA to the BCD surface. Thus, an adaptable surface modification architecture for microfluidic applications was developed and demonstrated.

Thesis (Ph.D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Janata, Jiri; Committee Co-Chair: Hunt, William; Committee Member: Allen, Mark; Committee Member: Brand, Oliver; Committee Member: Ferguson, Ian; Committee Member: Lyon, Andrew

Thesis (Ph. D. in Chemistry)--Vanderbilt University, Dec. 2009. / Title from title screen. Includes bibliographical references.

L’objectif de cette thèse est de synthétiser de nouvelles surfaces spécifiques nécessaires à l’immobilisation des biomolécules ; visant à développer à terme un biocapteur pour la détection de pathogènes en industrie agroalimentaire. Cette nouvelle procédure de fonctionnalisation de surface consiste d’une part à greffer des molécules organiques sur un substrat métallique à partir d’une réaction électrochimique et d’autre part de synthétiser un monomère photopolymérisable sur tout type de surface. Ces surfaces sont enfin utilisées pour immobiliser les biomolécules. Ce procédé ainsi développé permet d’éliminer les multiples étapes, l’utilisation excessive de réactifs observés dans les protocoles classiques de fonctionnalisation de surface pour la capture de microorganismes. Deux stratégies de fonctionnalisation ont été investiguées : la polymérisation sur une plaque de platine et le dépôt de monocouche sur une surface d’or. La fonctionnalisation de surfaces ainsi que l’immobilisation de biomolécules ont été caractérisées par la spectroscopie Raman, la microbalance à cristal de quartz, la microscopie à force atomique (AFM) pour le premier et en plus la microscopie à fluorescence pour le second. Les résultats de la fonctionnalisation de surfaces par dépôt de polymère ont montré, une déstabilisation du polymère en présence de l’eau. Afin d’optimiser la synthèse, nous avons travaillé en milieu inerte, sous alumine activée. De plus, on note une large couverture de la zone spectrale des biomolécules par les signaux du polymère ; Pour le dépôt de monocouche, l’on a obtenu une surface très réactive, homogène. La diffusion Raman est la principale technique de caractérisation utilisée. Elle présente l'avantage d'être une méthode de caractérisation physico-chimique non destructive et non invasive. Longtemps délaissée dans les sciences du vivant, cette méthode apparaît maintenant particulièrement prometteuse grâce à un développement récent de spectromètres intégrés performants. La diffusion Raman sur la monocouche déposée montre une intensité accrue des signaux par l’utilisation de la surface d’or et un spectre plus dégagé conduisant à l’identification aisée des biomolécules après fixation. Elle permet non seulement d’identifier les bandes de vibrations de chaque groupement mais aussi la conformation des structures. Les résultats d’immobilisation ont montré que l’accroche des biomolécules sur les surfaces fonctionnalisées était spécifique. La fonctionnalisation de surface d’or par dépôt de monocouche constitue finalement une technique très rapide à mettre en œuvre, peu coûteuse permettant d’ancrer efficacement les biomolécules et peut être utilisée pour diverses applications. La synthèse du monomère photopolymérisable a été abordée et est en cours d’investigation. / In food processing industry, detecting bacteria or viruses is crucial. Nowadays, it can be achieved with microbiological tests but, it requires several days. The objective of the project was to synthesize new specific surfaces capable of biomolecules immobilization in order to develop a biosensor for the detection of various pathogenics in food-processing industry. This new procedure of surface functionalisation consists on one hand in anchoring organic molecules on a metallic substrate by an electrochemical reaction and on the other hand to synthesize a photocrosslinkable monomer on every type of surface. These surfaces are finally used to immobilize biomolecules. Two strategies of surface functionalisation were investigated: the polymerization on a platinium surface and the deposition of monolayer on a gold surface. Both processes were characterized by spectroscopy Raman, Quartz Crystal Microbalance, Atomic Force Microscopy and Fluorescence Microscopy. The results of the functionalisation of surfaces by deposition of polymer showed a destabilization of the polymer in presence of water. To optimize the synthesis, we worked in sluggish middle, under activated alumina. Furthermore, we noted a wide coverage of the spectral zone of biomolecules by the signals of the polymer; For the monolayer deposition, we obtained a very reactive and homogeneous surface. The Raman spectroscopy was the main technique used to the characterization. It presented the advantage to be a non-destructive and non invasive physico-chemical method. This method seemed now particularly promising due to a recent development of successful integrated spectrometers. Raman Spectroscopy showed an enhanced intensity of the signals by the use of the gold surface and a more clear spectrum well-to-do identification of biomolecules after binding. It allowed not only the identification of the bands of vibrations of every connection but also the conformation of the structures. The results of the immobilization showed that the grafting of biomolecules on functionalised surfaces was specific and efficient. The functionalisation of gold surface by monolayer deposition constituted at the end an efficient and low cost technique allowing to anchor biomolecules and can be used for multitude applications. The last step consisting of the synthesis of photocrosslinkable monomer was started and still investigated.

As the two most abundant natural polymers on earth, cellulose and chitin have attracted increasing attention as a source of renewable energy and functional materials. Thin films of cellulose and chitin are useful for studying interactions of these materials with other natural and synthetic molecules via techniques such as quartz crystal microbalance with dissipation monitoring (QCM-D) and surface plasmon resonance (SPR). Because of the difficulty of extracting native cellulose, regenerated cellulose (RC), sulfated nanocrystalline cellulose (SNC), and desulfated nanocrystalline cellulose (DNC) thin films are often studied in its place. In this work, QCM-D solvent exchange studies showed that water contents of RC, SNC and DNC films were proportional to the film thickness (d). Accessibility and degradation of the films was further analyzed via substrate exposure to cellulase. Cellulase adsorption onto RC films was independent of d, whereas cellulase adsorption onto SNC and DNC films increased with d. Enhanced access to guest molecules for SNC and DNC films relative to RC films revealed they are more porous. The porosity of these cellulose films aided in understanding the observed differences of xyloglucan (XG) adsorption onto their surfaces. Xyloglucan adsorption onto RC, SNC, and DNC was studied by QCM-D and SPR. The amount of adsorbed XG increased in the order RC < SNC < DNC. XG adsorption onto RC films was independent of d, whereas XG adsorption was weakly dependent upon d for SNC films and strongly dependent upon d for DNC films. However, XG adsorbed onto "monolayer" thin films of RC, SNC, and DNC in approximately the same amount. These results suggested that the morphology and surface charge of the cellulose substrate had a limited effect upon XG adsorption and that accessible surface area of the cellulose film may be the factor leading to apparent differences in XG adsorption for different surfaces. The porosity and surface charge of SNC films presented a unique opportunity to examine polyelectrolyte adsorption and subsequent dewatering of the SNC substrate. The adsorption of a series of cationically derivatized dextran (cDex) polyelectrolytes with various degrees of substitution (DS) onto SNC was studied using QCM-D and SPR. As the hydrophobic character of the cDex samples increased, the water content of the adsorbed cDex layer decreased. For cDex with the greatest hydrophobic content, nearly 50% by mass of the initial water present in the porous SNC film was removed upon cDex adsorption. This study indicated that the water content of the film could be tailored by controlling the DS and hydrophobic character of the polyelectrolyte. This work also presents the first report of smooth, homogeneous, ultrathin chitin films, opening the door to surface studies of binding interactions, adsorption kinetics, and enzymatic degradation. The chitin films were formed by spincoating trimethylsilyl chitin onto gold or silica substrates, followed by regeneration to a chitin film. The utility of these chitin films as biosensors was evident from QCM-D and SPR studies that revealed bovine serum albumin adsorbed as a monolayer. / Ph. D.