Surfaces of organic and inorganic materials can be coated with a polydopamine (PDA) layer via immersion of the substrates in a basic solution of dopamine. The PDA layer can then serve as a convenient anchor for subsequent functionalization. For example, it can reduce silver ions to silver nanoparticles (AgNPs) to form an antimicrobial coating on the substrates. However, this method faces two limitations in scaling up for practical applications. To achieve a robust PDA layer that completely covers the surface, an immersion period of 24 h is typically required, and in the presence of oxygen and base, the onset of polymerization of dopamine cannot be easily controlled. In our presentation, we will describe the synthesis of two dopamine derivatives which will enhance the practicality of using polydopamine to prepare surface coatings. Dopamine substituted with an electron-donating methoxy group (OMeDA) polymerized faster than dopamine under similar reaction conditions. A polymer coating of 13 nm thickness on a silicon surface can be obtained with OMeDA after 8 h, compared to the 24 h required for dopamine to form a coating of similar thickness. Both polymer coatings are equally effective in reducing Ag+ from solution and immobilizing the formed AgNPs. To further shorten the processing time, a one-pot method can be used to prepare a strongly bactericidal coating by immersing the substrate in a basic solution containing OMeDA and silver nitrate for 2 h. The second dopamine derivative, o-nitrobenzyl dopamine (NBDA), was designed to be photolabile, and UV irradiation of a methanolic solution of NBDA at 365 nm for 40 min induced ~ 85% deprotection. A one-pot UV-triggered deprotection and subsequent polymerization technique was developed for modifying surfaces with PDA via spray coating using ethylene glycol and Tris buffer as the solvent. The formed PDA coating is highly stable in water, and silver incorporated in the coating imparts antimicrobial properties. The ability to control the onset of polymerization coupled with ease of spray coating facilitates the preparation of antimicrobial coatings for large surfaces.

Dopamine derivatives for enhancing practicality of fabricating polydopamine-based antimicrobial coatings

254th National Meeting (2017)

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