Department of Mechanical EngineeringIn recent years, extensive efforts have been devoted to developing antibiofilm material which can effectively prevent biofilm formation. Currently, the most common method of preventing protein or bacteria adhesion is to impart surface functionalization using PEGylated materials or zwitterionic materials with excellent antifouling properties. This method is resistant to the surface adhesion of proteins and microorganisms but is less mechanically durable and easily damaged by external physical and chemical stimuli, which can lead to the loss of antifouling performance. Bactericidal methods include chemical killing by antibiotics and physical killing due to surface structure. Chemical methods using silver, nitrates, or copper can cause microbial infections due to antibiotic resistance and can be toxic and biologically harmful.
To avoid this problem, researchers have been studying physical killing methods. Nanostructures which can be fabricated using silicon, metal, or polymers have been used to kill bacteria. However, these methods also have many limitations, such as complex fabrication methods, high cost, secondary biofilm formation, and especially the problem of the remaining dead bacterial carcasses. Furthermore, many previous studies, whether concerning the chemical or mechanical approaches, have focused on a single strategy, such as antifouling coatings, bactericidal materials, or nanopatterning. However, these single-strategy approaches have many limitations, such as the drug resistance of bacteria, toxicity to cells and the environment, low antifouling performance, high cost, or low mechanical and chemical durability in the prevention of biofilm formation. Therefore, to overcome these many drawbacks first of all, simple, cost-effective, environmentally friendly and reproducible fabrication methods are strongly required. Moreover, to overcome several problems of the single-strategy approaches, a multi-strategy or hybrid approach should be considered.
This dissertation presents the development of a hybrid strategy based on an antifouling material and bactericidal nanostructures that aim to combine both the antifouling and bactericidal functions to maintain effective anti-biofouling performance.
Our hybrid anti-biofouling surface consists of nanostructures with the biocompatible materials polyethylene glycol dimethacrylate (PEGDMA) and cellulose acetate (CA). The biocompatible nanostructure array was easily fabricated using UV molding and soft lithography. Moreover, 2-methacryloyloxyethyl phosphorylcholine (MPC), a zwitterionic polymer, was covalently grafted onto the fabricated nanostructures for superior antifouling performance. The surface can be applied to various 3D surfaces and large areas, due to the flexibility of the base material. Based on the synergetic integration of the bio- and ecofriendly nanostructural polymer and MPC, our hybrid strategy can easily fabricate an efficient anti-biofouling surface which can overcome the limitations of previous antifouling and antibacterial surfaces. Furthermore, our hybrid surface has high chemical / structural stability even in wet conditions. Not only can it effectively prevent bacterial attachment, but it also exhibits better bactericidal effects, regardless of the bacterial types, compared with single anti-biofouling strategies (repelling bacteria or killing bacteria). Furthermore, it preserves robust and excellent anti-biofouling activity, even under external stimuli and long-term fouling tests.
This novel hybrid anti-biofouling surface provides a more-promising solution for the prevention of initial bacterial attachment and subsequent biofilm formation. In particular, the hybrid anti-biofouling function makes these surfaces more suitable for applications in which long-term antibacterial activity is required. Also, our developed surfaces can play an important role in solving bio-contamination problems in the medical and marine industries.clos
