Bacterial infection has drawn serious attention in modern medicine, either in respect to biomaterial infection or invasion of tissue surfaces in human bodies. Bacterial adhesion is an essential step in biofilm formation and subsequent infection. Among those factors involved in the complex adhesion process, specific adhesion is a major determinant of cell-cell and cell-substratum adhesions. Currently, the receptor:ligand theory is widely adopted as the governing mechanism of specific cell adhesion.Staphylococcus epidermidis , a prevailing nosocomial pathogen of biomedical implants and devices, uses the specific adhesion binding with human fibronectin (FN), a glycoprotein found in extracellular matrix and plasma. A FN specific receptor on S. epidermidis and the protein FN pair as the receptor:ligand in specific adhesion. This dissertation reports an experimental study of the specific adhesion of S. epidermidis cells to fibronectin-coated substrata under uniform shear flow. The effects of ligand density on specific adhesion as well as the binding affinities between bacterial cells and different portions of the ligands were studied. The amount of FN molecule bound on the substratum was verified by radiolabeling. Results revealed that exposed NH 2 functional groups of FN exhibited better binding affinity with S. epidermidis cells than to the FN molecule with -COOH functional groups free. Increases in FN density on the substratum with the NH 2 groups exposed to bacterial cells led to increased rates and extent of bacterial adhesion.A dynamic model, proposed in a previous work, was used to describe bacterial cell adhesion that is mediated by specific receptor:ligand binding. Computer simulations of specific adhesion were carried out by introducing the actual laboratory conditions and experimental parameters into the model to interpret the results. The computer simulations agreed well with the experiments with lower inlet cell concentration, while larger deviations existed in the range of higher inlet cell concentration.
蒙大拿州立大學 土木工程所 博士論文 Montana State University Dissertation