Polydopamine films change their physicochemical and antimicrobial properties with a change in reaction conditions

Abstract

The morphology and physicochemical properties of polydopamine are not totally inherent and undergo changes with differing reaction conditions like the choice of solvent used for polymerization. The polymerisation of dopamine to polydopamine carried out in different solvents like sodium hydroxide, sodium bicarbonate, PBS and Tris leads to polydopamine with exceptionally different morphological and physicochemical features with each solvent. Additionally, the different physicochemical characteristics and morphologies bestow the polymer films with different extents of antimicrobial activity. Moreover, the findings supported by chemical evidence from X-ray photoelectron spectroscopy reveal that higher antibacterial activities were obtained against E. coli and S. aureus with polydopamine films prepared by Tris and NaOH solvent induced polymerization. The antibacterial activity observed in saline was found to be higher than that in PBS medium for both E. coli and S. aureus. The higher antibacterial activity of polydopamine films prepared in Tris and NaOH solvents was attributed to the covalent incorporation of -OH groups on the surface provided by nucleophilic Tris and NaOH solvents during the polymerisation process. The distinct physicochemical and morphological changes were supported by the results from contact angle measurements, FE-SEM, EDAX, AFM, and XPS analysis. The present finding provides insight into the different chemistry, morphologies and properties of the designed polydopamine films with controlled antibacterial/antifouling properties. Additionally, new insights into the mechanism of formation, physicochemical changes in morphology and properties of polydopamine coatings were revealed.

Antibacterial Properties of Mussel-Inspired Polydopamine Coatings Prepared by a Simple Two-Step Shaking-Assisted Method

“…The surface chemical composition of the PDA-coated mesh was evaluated using XPS (Figure 4). All samples exhibited peaks corresponding to C1s (284.6 eV), N1s (399.8 eV), and O1s (533.6 eV) on their wide scan XPS spectra as expected based on previously published results on PDA coatings (Luo, 2017; Patel et al, 2018). All spectra also contain a Si peak, which corresponded to the silicon dioxide (SiO 2 ) at 102.2 eV binding energy on the surface of the sample holder used for the experiment.…”

“…All the mesh samples exhibited peaks associated with PP such as 2,916 cm −1 (C–H bands), 1,457 cm −1 (–CH 2 ), and 1,379 cm −1 (–CH 3 ) (Krylova and Dukštienė, 2013). Spectra of all the PDA-coated meshes contained additional peaks at 1,509 cm −1 (C = N of indole amine), 1,602 cm −1 (C=C of benzene ring), 1,723 cm −1 (C=O of quinone), and 3,100–3,700 cm −1 (N–H and O–H stretch vibration) (Patel et al, 2018). There was no apparent differences in the ATR-FTIR spectra for coatings that were prepared differently (i.e., non-shaken vs. shaken, and one-step vs. two-step).…”

Chemistry of Polydopamine – Scope, Variation, and Limitation

“…The properties of PDA depend very much on the mode of synthesis. [55a] The majority of PDAs are dark‐black solids insoluble in most solvents. A wide UV/Vis absorption is observed ranging from the UV till infrared.…”

“…The energy of absorbed light is released almost entirely radiationless (radiative quantum yield 0.2 %). [55b] This property was recently exploited in the development of sun screen gels or for internal protection of cells . PDA coating was also applied to protect poly(vinylidene fluoride) membranes against UV light or free radical initiated damage .…”

Micro-Structured Polydopamine Films via Pulsed Electrochemical Deposition

“…As the film height and morphology are not altered, the determination of roughness parameter and film thickness was performed in contact mode in air. In general, AFM characterization for chemically or electrochemically deposited PDA films is usually reported for rather small areas (e.g., 1 µm × 1 µm) or AFM images with insufficient quality are presented, which makes the evaluation of the film homogeneity difficult [15,39].…”