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

Abstract

A simple two-step, shaking-assisted polydopamine (PDA) coating technique was used to impart polypropylene (PP) mesh with antimicrobial properties. In this modified method, a relatively large concentration of dopamine (20 mg ml−1) was first used to create a stable PDA primer layer, while the second step utilized a significantly lower concentration of dopamine (2 mg ml−1) to promote the formation and deposition of large aggregates of PDA nanoparticles. Gentle shaking (70 rpm) was employed to increase the deposition of PDA nanoparticle aggregates and the formation of a thicker PDA coating with nano-scaled surface roughness (RMS = 110 nm and Ra = 82 nm). Cyclic voltammetry experiment confirmed that the PDA coating remained redox active, despite extensive oxidative cross-linking. When the PDA-coated mesh was hydrated in phosphate saline buffer (pH 7.4), it was activated to generate 200 μM hydrogen peroxide (H2O2) for over 48 h. The sustained release of low doses of H2O2 was antibacterial against both gram-positive (Staphylococcus epidermidis) and gram-negative (Escherichia coli) bacteria. PDA coating achieved 100% reduction (LRV ~3.15) when incubated against E. coli and 98.9% reduction (LRV ~1.97) against S. epi in 24 h.

Fabrication and Characterization of Calcium-Phosphate Lipid System for Potential Dental Application

“…Three hundred microliter of 25 mM Na 2 HPO 4 (pH = 9.0) in chloroform was dispersed in the same solution to form the phosphate phase, and 200 µL (20 mg/mL) dioleoylphosphatydicacid (DOPA) in chloroform was added. The amphiphilic DOPA could stay at the interface of micro-emulsions and interact with the precipitated CaP core through binding with the surface Ca 2+ (Kord Forooshani et al, 2019).The above two solutions were mixed adequately for 20 min, then 30 mL ethanol was used to wash the cyclohexane and surfactant 2-3 times (centrifuging at 12,000 g for 15 min each time). The pellets were dissolved in 1 mL chloroform forming CaP core suspension.…”

Tuning the antimicrobial activity of low molecular weight hydrogels using dopamine autoxidation

“…During this oxidation process reactive oxygen species such as superoxide anions and hydrogen peroxide (H 2 O 2 ) are generated as by-products. 22 Despite widespread interest in the use of polydopamine as an antimicrobial agent, there is still dispute as to the exact mechanism by which it develops, however, it is known that the selfpolymerization process requires alkaline conditions and the presence of oxygen. 23 H 2 O 2 is well known for its antimicrobial activity, 3,24 and the sustained release of H 2 O 2 generated as a result of the dopamine self-polymerization process has demonstrated broad spectrum antimicrobial activity against Grampositive and Gram-negative organisms.…”

“…23 H 2 O 2 is well known for its antimicrobial activity, 3,24 and the sustained release of H 2 O 2 generated as a result of the dopamine self-polymerization process has demonstrated broad spectrum antimicrobial activity against Grampositive and Gram-negative organisms. 22 One group of gels that has been used to form antimicrobial gels are LMWGs. Specifically here, we work with LMWG with a hydrophobic group attached to a dipeptide; this class can be tailored to specific requirements.…”

“…44 Interestingly, work by Forooshani et al found the sustained release of low doses of H 2 O 2 , generated during polydopamine production, was sufficient to achieve broad spectrum activity against both Grampositive and Gram-negative bacteria. 22 Antibacterial efficacy may therefore be a concentration dependent effect reliant on the rate at which H 2 O 2 or other reactive oxygen species are produced within the system. Gram-negative microorganisms demonstrate increased resistance to reactive oxygen species, requiring increased exposure time or concentration to achieve significant kill.…”

“…Gram-negative microorganisms demonstrate increased resistance to reactive oxygen species, requiring increased exposure time or concentration to achieve significant kill. 22 Unfortunately, it is not possible to determine due to the colour of our gels as well as the assays only being suitable for fully solubilised systems.…”