Effects Of Surface-Modification On Bacterial Adhesion

Bacterial adhesion on surfaces often occurs in medical equipment and food processing industry, and causes implanted infections, food spoilage and human illness. Bacterial adhesion usually caused biofilms formation, which increased the possibility of the damage above.Besides, biofilms was resistant to the bactericide, which made regular bactericide and sanitizer useless. Preventing initial adhesion to materials could be an important step in avoiding the safety and health problems. Recent studies showed that the initial bacterial adhesion was impacted by several factors, such as hydrophobicity, surface charge and surface energy. As a result, the mechanism of bacterial adhesion is too complex to be predicted.In this study, various strategies have been developed to limit bacterial colonization on material surfaces by surface modification. The effects of surface hydrophobicity, electrical property, surface topography and surface chemical composition on inhibiting bacterial adhesion were studied, the results obtained might provide guidance for the future development of anti-bacterial materials.Firstly, materials with different surface wettability were fabricated via chemical grafting method. The surface wettability was modulated by changing the ratio of cysteamine and3-mercaptopropionic acid through the octadecanethiol/cysteamine,octadecanethiol/3-mercaptopropionic acid grafting. Three typical pathogenic bacteria strains(Escherichia coli BL21, Staphylococcus aureus 6538 and Pseudomonas aeruginosa ATCC9027) were studied to determine the influence of surface wettability on bacterial adhesion,and the results showed that increasing surface hydrophobicity reduced bacterial adhesion.Besides, negative charged surfaces were demonstrated to be more effectively to inhibit bacterial adhesion.Secondly, three different micro-patterned polydimethylsiloxane(PDMS) films with various pattern sizes from 0.5 to 4 ?m were fabricated by electron lithography and soft stamp technology. The three strains above were used to quantitatively show the anti-adhesive properties of the films. The results showed that the micro-patterned topography could weaken the attachment of these three strains to the films. The difference between the pattern size and the bacterial size was crucial to the amount of bacteria adhered on the surfaces. If the pattern size was smaller than the bacteria size, then fewer bacteria adhered on the surfaces. It was also shown that increasing surface hydrophobicity and shear stress could also reduce bacterial adhesion.Finally, the bactericide, Ag+ was implanted into the surface of polyethylene(PE) films with different concentration by ion implantation and bacterial adhesion on the modified films was reduced. Bacteria could also be killed by this material. Besides, the concentration of Ag+dissolved in the medium was lower than 0.01mg/L.