Bioinspired Surface Modification for Antifouling and Antibacterial Applications
Creators: Asha, Anika Benozir 
Publisher: name: University of Alberta Library
Year: 2022

<p>Biofouling is a serious problem in the medical, marine, and several other industrial fields as it poses significant health risks and financial losses. Therefore, there is a great need to endow surfaces with antifouling and antimicrobial properties to mitigate biofouling. For long-term biofouling resistance, a unifunctional antimicrobial or non-adhesive surface is insufficient for preventing biofilm formation. To overcome this limitation, non-adhesive and antimicrobial dual-functional surfaces are highly desirable. Zwitterionic polymers have been used extensively as one of the best antifouling materials for surface modification. Being a super hydrophilic polymer, zwitterionic polymers need a strong binding agent to maintain attachment to the surface for long-term applications. In this thesis work, new strategies have been explored for surface modification to covalently graft zwitterionic polymers using mussel-inspired dopamine chemistry and prebiotic chemistry for long-term antifouling and antimicrobial applications.<br>
In the first project, a facile surface modification technique using dopamine chemistry was developed to prepare a super hydrophilic coating with both antifouling and antimicrobial properties. Catechol containing adhesive monomer dopamine methacrylamide (DMA) was copolymerized with bioinspired zwitterionic 2-methacryloyloxyethyl phosphorylcholine (MPC) monomer, and the synthesized copolymers were covalently grafted onto the amino (−NH2) rich polyethylenimine (PEI)/polydopamine (PDA) codeposited surface to obtain a stable antifouling surface. The resulting surface was used for in situ deposition of antimicrobial silver nanoparticles (AgNPs), facilitated by the presence of catechol groups of the coating. This dual functional coating significantly reduced the adhesion of both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria and showed excellent resistance to bovine serum albumin adsorption. This bioinspired and efficient surface modification strategy with dual functional coating promises its potential application in implantable biomedical devices.<br>
In the second project, a smart surface was developed which can not only kill the attached microbials but also can release the dead cells and foulants from the surface under a particular incitement on demand. In this project, sugar responsive self-cleaning coating was developed by forming covalent boronic ester bonds between catechol groups from polydopamine and benzoxaborole pendant from zwitterionic and cationic polymers. To incorporate antifouling property and enhance biocompatibility of the coating, zwitterionic compound MPC was chosen and benzoxaborole pendant containing zwitterionic polymer poly (MPC-st-MAABO) (MAABO: 5-Methacrylamido-1,2-benzoxaborole) was synthesized. Additionally, to impart antibacterial properties to the surface, quaternary ammonium containing cationic polymer poly (2-(methacryloyloxy)ethyl trimethylammonium (META)-st-MAABO)) was synthesized. These synthesized polymers were covalently grafted to PDA coated surface by forming a strong cyclic boronic ester complex with catechol group of PDA layer endowing the surface with bacteria contact-killing property and capturing specific protein. After the addition of cis-diol containing competitive molecules i.e. sugars, this boronic ester complex with catechol group of PDA was replaced and attached polymer layer cleaved from the surface resulting in the release of both absorbed protein and live/killed bacteria electrostatically attached to the polymer layer. This dynamic self-cleaning surface can be a promising material for biomedical applications avoiding the gathering of dead cells and debris which is typically encountered on traditional biocidal surfaces.<br>
In practice macro or micro scratches or damages can happen to the coating which can act as an active site for microbial deposition and destroy the antifouling or antibacterial functionality of the coating. In the third project, an excellent biocompatible and multifunctional coating with antifouling, antibacterial and self-healing property was developed. Prebiotic chemistry inspired self-polymerization of AMN was used as a primary coating layer which act as a primer to graft vitamin B5 analogous methacrylamide polymer poly(B5AMA) and zwitterionic compound MPC containing polymer poly (MPC-st-B5AMA) by forming strong hydrogen bond. B5AMA having multiple polar groups into the structure acted as an intrinsic self-healing material and showed excellent antifouling property against protein and bacteria maintaining a good hydration layer. To impart the antibacterial property into the coating AgNps has also been incorporated which showed more that 90% killing efficiency against both gram-positive and gram-negative bacteria with significant reduction of their adhesion on the surface. Incorporation of self-healing property into the fouling repelling and antibacterial coating can significantly extend the durability of the multifunctional coating making it promising for biomedical applications.<br>
Three different surface modification techniques explored in this thesis, not only demonstrates excellent antifouling and antibacterial property but also provides fundamental insights into the facile development of multifunctional coating in various biomedical applications.</p>