The multi-drug resistance properties of water-borne pathogens will keep them a significant threat to global health and safety. Due to this reason alone, research into preventive methods should be of utmost priority. Current mainstream antibacterial and water filtration technologies are not equipped to deal with the challenges arising from water-borne bacterial pathogens. Furthermore, they need to be more sustainable. Typically, mainstream water purification strategies are based on two main approaches. Chemical treatment which includes processes like chlorination or ozonisation. Unfortunately, this method requires energy and chemical input and results in the release of toxins. On the other hand, membrane filtration is a more widely adopted approach to remove bacteria with low energy input and without the release of toxins. However, certain shaped bacteria (such as spirillum-shaped Hylemonella gracilis) have been known to pass through it. Since membrane filtration works on the principle of size exclusion, material and maintenance costs due to clogging and biofouling for membranes make it unsustainable. In this research project, innovative material and strategy were studied to deal with the challenges of bacteria filtration. A flexible two-dimensional material was designed and synthesized that catches bacteria based on electrostatic attraction. Micrometer-size GO sheets were functionalized with an acrylate polymer with secondary amines via free radical polymerization of 2-dimethylammonium ethyl methacrylate. Secondary amines of the polymer were quaternized in the 2nd step by methylation reaction to change the charge of flexible sheets from negative to positive. Protocol was developed to quantify the charge per unit surface area of GO-PTEMA sheets. Upon interaction with bacteria, flexible sheets adapt to the shape of bacteria and bind the particles. AFM confirmed the wrapping of positively charged sheets with live bacteria in liquid cell. In the 2nd part of the research project, the GO-PTEMA sheets were covalently immobilized on cellulose fiber as support material (GOX fibers) to design and produce a filtration device. The immobilization was confirmed with SEM. Fluorescence microscopy was used to examine the interactions of GOX fiber with bacteria. Since there were few investigations into the filtration perimeters of bacteria-binding materials, protocols were developed to test the effect of parameters such as flow rate on the filtration performance. The filter performance of 3-log CFU reduction was achieved at flow rates around five times higher than membrane filters. 100 mg of the created GOX fibers, removing up to 109 CFU with 99.5% filtration efficiency. Since the principle of removing bacteria is based on binding via electrostatic attraction, the typical problem of membrane clogging and back pressure is not an issue when the filter is entirely loaded with bacteria. In a broader sense, this project provides a detailed report from the synthesis and characterization of a material for an application to design and manufacture prototypes with detailed testing. There are reports of polycationic polymers and zwitterionic systems that bind and inhibit bacteria proliferation with minimum inhibition concentration tests. However, there are few studies to take them to the next step of determining their abilities in filtration settings. Protocols developed during this project can be used to test many of the features and save time and effort. This work provides a platform to develop future hybrid materials for filtration applications.
