Study of cyclic antibacterial polymers
Sagar, Kundan Kumar
Date of Issue2016
School of Chemical and Biomedical Engineering
The pervasiveness of microbial infections and the development of resistance in bacteria against traditional antibiotics have created a need for an alternative solution. Synthetic materials such as cationic cyclic Poly 2-(dimethylamino)ethyl methacrylate copolymerized with tert-butyl methacrylate P(DMAEMA-co-tBMA) are of interest due to the difficulty for bacteria to modify their entire cell membrane to develop resistance. This paper reports the successful synthesis of the cyclic and linear architectures of cationic P(DMAEMA-co-tBMA) to investigate and compare their respective antimicrobial properties. The two variants were polymerized utilizing ATRP and the cyclic structure was obtained via intra-chain ‘click’ cyclization. They were then characterized using nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR) and size exclusion chromatography (SEC). The antimicrobial properties were tested using minimum inhibitory concentration (MIC) tests, live/dead assays and SEM to assess cell viability and effects that polymers have on Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) cell membranes. The MIC tests show that cyclic structures have superior antimicrobial effects in comparison to linear structures. In the case of E. coli, cyclic structures required 78 μg/ml MIC as compared to 156 μg/ml for linear and 40 μg/ml vs 78 μg/ml for S. aureus. This could be attributed to the smaller hydrodynamic diameter of cyclic probably due to self-assembly which condenses the cationic charges and increases electrostatic interactions with bacteria cell walls.