Browsing by Subject "biosensor"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item Characterization and applications of microfluidic devices based on immobilized biomaterials(Texas A&M University, 2007-04-25) Heo, JinseokMicrofluidic biosensors and bioreactors based on immobilized biomaterials are described in this dissertation. Photocrosslinkable hydrogel or polymeric microbeads were used as a supporting matrix for immobilizing E.coli or enzymes in a microfluidic device. This dissertation covers a microfluidic bioreactor based on hydrogel-entrapped E.coli, a microfluidic biosensor based on an array of hydrogel-entrapped enzymes, and a microfluidic bioreactor based on microbead-immobilized enzymes. Hydrogel micropatches containing E.coli were fabricated within a microfluidic channel by in-situ photopolymerization. The cells were viable in the hydrogel micropatch and their membranes could be porated by lysating agents. Entrapment of viable cells within hydrogels, followed by lysis, could provide a convenient means for preparing biocatalysts without the need for enzyme extraction and purification. Our results suggested that hydrogel-entrapped cells, immobilized within microfluidic channels, can act as sensors for small molecules and as bioreactors for carrying out reactions. A microfluidic biosensor based on an array of hydrogel-entrapped enzymes could be used to simultaneously detect different concentrations of the same analyte or multiple analyte in real time. The concentration of an enzyme inhibitor could be quantified using the same basic approach. Isolations of the microchannels within different microfluidic channels could eliminate the possibility of cross talk between enzymes. Finally, we characterized microfluidic bioreactors packed with microbead-immobilized enzymes that can carry out sequential, two-step enzyme-catalyzed reactions under flow conditions. The overall efficiency of the reactors depended on the spatial relationship of the two enzymes immobilized on the beads. Digital simulations confirmed the experimental results.Item Thermodynamics and Applications of Elastin-like Polypeptides(2010-10-12) Cho, Youn HeeUnderstanding protein stability and folding is of central importance in chemistry, biology, and medicine. Despite its importance, a molecular level understanding of protein stability still remains illusive due to the complexity of the system. In this study, we employed protein-like polypeptides to study several aspects of protein stability in different aqueous environments. The model system employed here is elastin-like polypeptides (ELPs). First, the modulation of the lower critical solution temperature (LCST) of neutral ELPs was investigated in the presence of 11 sodium salts that span the Hofmeister series for anions. It was found that the hydrophobic collapse/aggregation of these ELPs generally followed the series. Specifically, kosmotropic anions decreased the LCST by polarizing interfacial water molecules involved in hydrating amide groups on the ELPs. By contrast, chaotropic anions lowered the LCST through a surface tension effect. Additionally, chaotropic anions showed salting-in properties at low salt concentrations that were related to the saturation binding of anions with the biopolymers. These overall mechanistic effects were also compared to the results previously found for the hydrophobic collapse and aggregation of poly(N-isoproplyacrylamide). A positively charged ELP, ELP KV6-112, was used as a next model system. We observed both inverse and direct Hofmeister effects on LCST with five chaotropic salts. Next, the solvent isotope effects on the LCST of ELPs were investigated as a function of ELP chain length and guest residue chemistry using D2O and H2O. Differences in the LCST values with heavy and light water were correlated with secondary structure formation of the polypeptide chains which was quantified by circular dichroism, FTIR, and differential scanning calorimetry measurements. It was found that there is a great change in the LCST values between H2O and D2O for those polypeptides which form the greatest amount of b-spiral structure. This study suggests that hydrogen bonding rather than hydrophobicity is the key factor in the stabilization of ELPs in D2O over H2O. The phase transition property of ELPs can also be applied to development of stimuli responsive biosensor system. In this study, we employed ELP-conjugate solid supported lipid bilayer as a size selective binding sensor.