Fabrication and application of polydopamine nanocomposites in antibacterial coatings on digital microfluidic platforms

Abstract

Digital microfluidics (DMF) is an emerging fluid-handling technology popular in chemical, biological, and biomedical applications due to its portability, automation, small reagent consumption, short analysis time, parallelization of different processes, and flexible device geometry. In this thesis, polydopamine (PDA) nanoparticles (NPs) synthesis was optimized on the DMF platform by adjusting the incubation time, reagent concentration, and molar ratio. The synthesis of monodispersed PDA NPs with a narrow size distribution was confirmed with SEM images. In addition, a new sandwich-structured PDA-silver hybrid material was designed and produced with a layer-by-layer assembly process named as PDA-Ag-PDA, where silver nanoparticles were wrapped between two layers of PDA, and the film was subsequently integrated with DMF. Each layer of PDA-Ag-PDA coating was analysed with 3D surface metrology, contact angle meter, and SEM-EDS, and AFM to measure their roughness values, water contact angle, element distribution, respectively. Silver is a common Surface Enhanced Raman Spectroscopy (SERS) material, and the enhancement factor of PDA-Ag-PDA was estimated to be 1.9 × 10⁴ using Rhodamine 6G as a probe molecule. The antibacterial property assays were performed on DMF by real-time monitoring the oxygen consumption during E. coli growth; the microfluidic approach consumed a smaller volume of reagent, required a shorter analysis time (maximum 10 hours), and allowed parallel operations to be performed. The PDA-Ag-PDA film with low cytotoxicity and strong antimicrobial effect was successfully developed and integrated with DMF, which can be an alternative platform for conducting biological applications on DMF in the future, in particular, for the adhesive protein and cells analysis.

Date of Award	2021
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology
Supervisor	Stefan NAGL (Supervisor)