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Biofilm Formation On The Surface Of Polyethylene And Its Inhibition

Posted on:2010-07-18Degree:DoctorType:Dissertation
Country:ChinaCandidate:H X LiFull Text:PDF
GTID:1101360278460431Subject:Organic Chemistry
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Medical polymers are used widely in medical fields due to their excellent mechanical properties. However, just as other medical materials, they are vulnerable by microorganisms. Their surfaces are often colonized by bacterial biofilm, in which microorganisms are protected against the host immune system and cannot be easily eradicated with antibiotics. Consequently, infections are difficult to treat via conventional antibiotic therapy and often lead to additional costs and patient's suffering. Thus, It is important for catheter related infections prevention that developing polymers against infectious biofilms formation.In this thesis, Triclosan and silver antibacterial agent were incorporated into LDPE by blending. Four pathogens commonly implicated in nosocomial infections, Staphyococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Candida Albicans were used for the adhesion studies. The main results obtained in this work are summarized as follows:(1) The contact angles differences of three samples were very tiny, it indicated that antibacterial agents added to LDPE had little influence on hydrophilicity. According to the evaluation method of JIS Z 2801:2000, the test results showed that both of the modified LDPE samples exhibited excellent antimicrobial ability against S. aureus and E. coli. In the model system that inoculum was used for forming biofilm, bacteria could adhere to the control sample and develop into a mature biofilm.(2) In vitro assay, the adhesion and propagation of four pathogens, especially Staphyococcus aureus, were evidently reduced by triclosan added into LDPE; thereby the formation of biofilm was prevented. However, the amount of bacteria on LDPE with silver antimicrobial agent was no less than that on the control sample. It meant that the adding of silver antimicrobial agent could not inhibit biofilm formation on LDPE surfaces.(3) The influences of nutritional condition, bacterial concentration and antibacterial agent concentration to pathogens behaviors were investigated. The results indicated that poor nutritional condition can limit the bacteria growth and lead to a decrease of the resultant microbial biomass. In the bacterial suspension with low bacterial concentration and limited nutrition, LDPE containing 0.3% of triclosan could significantly reduce the account of bacteria on surfaces and inhibit biofilm formation. Contrarily, LDPE containing 1% of silver antimicrobial agent did not take obvious inhibitory effects on biofilm formation. The inhibitory effects on pathogens were enhanced remarkably by increasing triclosan content.(4) SEM and CLSM (confocal laser scanning microscopy) were adopted to evaluate the structural characteristic of biofilm. SEM images demonstrated that there were a lot of bacteria enclosed in matrix of extracellular polymeric substances on the surfaces of control sample and LDPE with silver antimicrobial agent, almost no bacteria adhering to LDPE containing triclosan. With CLSM, direct observations of living biofilms showed that the structural of biofilm was heterogeneous. There were more viable cells in the outer regions of the biofilm, and the inner portion of biofilm contained more dead cells than the outer portion. CLSM results showed that there were more dead cells in biofilms on LDPE with silver antimicrobial agent than in biofilms on control sample.(5) The results indicated that the antibacterial agents added did not change the mechanical properties of the host polymer. According to GB/T16886, the results of biosafety evaluation indicated that antimicrobial polymers met the requirements of medical devices.
Keywords/Search Tags:medical polymer materials, biofilm, inhibition, adhesion, infection
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