| Summary: | 博士 === 國立臺灣科技大學 === 高分子工程系 === 93 === The main focus of this thesis is to modify the surface properties of polyesters by blending, γ-ray irradiating, or ozone treating, to improve the antibacterial activity and biocompatibility of polyesters. In this work, either polyester fibers or membranes were
employed: poly(ethylene terephthalate) (PET) and poly(sodium ethylene 5-sulfoisophthalte) (PSES) were blended in various ratios and made into membranes; three fibers, PET, poly(2-methyl-1,3-propylene terephthalate -co- ethylene terephthalate) (PMPT), and
poly(1,4-cyclohexylene terephthalate -co- ethylene terephthalate)(PCHT) were irradiated with 60Co-γ-ray; poly(3-hydroxybutyric acid) (PHB) and poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid) (PHBV) membranes were treated with ozone.
Chitosan (CS) or chitooligosaccharides (COS) was grafted to the surfaces of irradiated or ozone-treated polyester and then grafted with hyaluronic acid (HA) or chondroitin-6-sulfate (ChS). The effect of the positive charges of CS- or COS-grafted materials on the adsorption of negatively charged proteins of human serum albumin (HSA) and human plasma fibrinogen (HPF), or the attachment and inhibition of Gram positive Staphylococus aureus strain-1 (S. aureus-1), Staphylococus aureus strain-2 (S. aureus-2), or Gram negative Escherichia coli O157:H7, and Pseudomonas aeruginosa, and the attachment and proliferation of L929 fibroblasts were studied. After grafting, the interaction between the membrane surface and the negatively charged bacteria, cells or proteins were electrostatic
attraction. Thus amount of adsorption/attachment increased with the surface charge on the membranes. Moreover, the number of cells growth on surface decreased with the increase of the surface charge on the membrane and, however, bacterial inhibition on surface
increased. On the other hand, on negatively charged polyester surfaces, the adsorption amount of bacteria or cells was higher than that on the neutral surface of unmodified polyester. The proliferation amount of bacteria or cells was also higher than on the neutral surface.
The interfacial free energy between the polymer surface and the liquid (γSL) decreased with number of the sulfonic group, which is thus affected by the content of PSES. The negative free energy of adhesion (-∆Fadh) and hence the number of attached bacteria increased
as the γSL increased. Furthermore, -∆Fadh decreased linearly with γp
SV (the polar component of γSV) (due to the increase of negatively charged sulfonic groups). In other words, negatively-charged bacteria attracted to surface decreased as the negative charge on the
polymeric surface increased, and thus -∆Fadh was reduced that made bacteria difficult to be adsorbed on the surface.
To describe the maximum velocity of bacterial growth (or nhibition), Vmax(V'max) and the equilibrium dissociation of bacterial growth (or inhibition) Km (K'm)were regressed based
on the Michaelis-Menten (or Monod) model. In the bacterial growth phase, the values of Vmax and Km of PHBV and the control (blank solution without polymer sample) were very close. This may be due to the adhesion of some bacteria to the surfaces of PHBV, which have no factors affecting the bacterial metabolism and growth. In the bacterial inhibition process, both V'max and K'm increased with the increase of the amine group on the surfaces.
This is because amine group would bind to the surface of bacteria, interfere the bacterial metabolism and growth, and eventually would lead to the death of bacteria. In the three-parameter kinetic model of bacterial growth or inhibition, S (reactant in bacteria) formed complex with E (enzyme for bacterial growth reaction) or E' (enzyme for bacterial inhibition reaction) to ES and E'S. After the formation of ES and E'S complex, the possibility of another substrate binding with to form ES2 orE'S2 was much lower. Accordingly, the K2 and K'2 (equilibrium constant of bacterial growth or inhibition) were small. Thus Michaelis-Menten (or Monod) model is sufficient to describe the kinetics of bacterial growth
and inhibition in this work.
This study shows that the characteristics of surface charge (sign and density) and the number of specific polar functional groups can affect the interaction between the cells/proteins and the materials, and hence are the major factors controlling the biocompatibility and the antibacterial activity.
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