Layer-by-layer system for antimicrobial applications

• Main Author: Liu, Jiaman.
• Other Authors: Chan Vincent
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering::Chemical engineering::Biotechnological production
• Online Access: http://hdl.handle.net/10356/16381
• Institution: Nanyang Technological University

With broadening public health understanding about the effects of bacteria and microorganisms, increasing attention has been drawn to create antibacterial or antimicrobial materials. In this paper, Layer-by-Layer (LbL) technique using Terephthaldehyde (TA)/Polyethyleneimine (PEI) as building blocks, coupled with silver as antiseptic agent was applied on titanium metal pieces, to create a multifunctional antimicrobial coating. Three properties namely anti-adhesive property, contact killing capacity and release killing ability were investigated by conducting the following tests. Coated Ti substrate was immersed in bacterial suspension containing E. coli and S. aureus, followed by staining with a combination dye to test the viability of the bacteria. Results have showed that the antimicrobial coating coated Ti substrate was able to kill bacteria on contact with its surface. In addition, the total bacterial count on the surface of the coated Ti substrate was little as compared to a plain titanium metal substrate. These have showed that the coated Ti substrate possesses contact killing capacity and anti-adhesive property. The coated Ti substrate was also immersed in a test tube containing 105 cells/ml of E. coli in 5ml of LB to test the ability to kill bacteria in solution, by measuring the optical density of the solution. The optical density was found to be low, which indicates the ability of the coated Ti substrate to release silver ions to inhibit the growth of bacteria. To further investigate this release killing property, Kirby-Bauer test was used to evaluate the zone of inhibition after the coated Ti substrate was incubated for 24 hours at 35°C on a gelatinous agar growth medium, swabbed with solutions of E. coli. A zone of inhibition around the coated Ti substrate was observed, where no bacterial colonies were seen, which clearly indicates the ability of the antimicrobial coating to release silver ions to kill the bacteria. From each of the tests, results have demonstrated that the antimicrobial coating coated Ti substrate has exhibited multifunctional properties; namely anti-adhesive property, contact killing capacity and release killing ability.