Abstract
In this work, we report the design of pH-controlled releasing behaviors of polydopamine/tannic acid-allicin@chitosan (PDA/TA-ALL@CS) multilayer coatings to realize antibacterial and antifouling effects. The pH-responsive ALL@CS capsules were prepared using the microemulsion method with about 262–452 nm diameter. The bacteriostasis of ALL@CS microcapsules against E. coli, S. aureus, and P. aeruginosa all exceeded 94% as evaluated using the colony counting method. Because of the protonation in acid environments and deprotonation in alkaline environments for the amino groups of CS, ALL as biocides can be released from the nanocapsules and exert outstanding antibacterial properties. Confirmed by the plate colony counts, the ALL@CS capsules possessed an outstanding antibacterial effect for E. coli in acid solutions but were less effective in alkaline solutions. The PDA/TA-ALL@CS-7 coatings showed durable pH-responsive antibacterial activities with an efficiency of ∼87% after immersion in pH 8 solutions for seven days. The PDA/TA-ALL@CS coating with controlled release performance and antibacterial properties may provide a new solution for developing antifouling coating applications in the marine environment.
Highlights
Biofouling issue in the marine environment brings a series of problems such as decreasing the speed of vehicles, increasing economic losses, and triggering the invasion of exotic species (Lejars et al, 2012)
Exploring antifouling coatings that release pH-Responsive Allicin-Based Antibacterial Coating antifoulant as required, especially at low-speed and at anchor states, is a critical guide for the future. Because the secretions such as acetic acid and lactic acid produced by bacterial metabolisms can decrease the pH of the microenvironment to acidic (Qian et al, 2007a; Traba and Liang, 2015; Hao et al, 2019; Saadouli et al, 2021), pH-responsive antifouling coatings have attracted increasing attention and developed rapidly in recent years (Hao et al, 2019; Hao et al, 2020; Huang et al, 2020; Xu et al, 2020)
The suspensions were shaken at 120 rpm and incubated at 37°C or 30°C for 18 h, and each 20 μL diluted bacterial suspension was taken for colony counting by spreading on the solid medium plate and incubating overnight at different temperature conditions
Summary
Biofouling issue in the marine environment brings a series of problems such as decreasing the speed of vehicles, increasing economic losses, and triggering the invasion of exotic species (Lejars et al, 2012). PH-Responsive Allicin-Based Antibacterial Coating antifoulant as required, especially at low-speed and at anchor states, is a critical guide for the future. The pH-responsive antibacterial properties of the nanocapsules were detected using DLS and the plate colony method. The antifouling and antibacterial performance of the PDA/TA-ALL@CS-n coatings were evaluated using the colony counting method and live/dead fluorescence. The ALL releasing behavior in different pH environments was measured using an ultraviolet–visible spectrophotometer (UV-Vis), and the pH-responsive antibacterial properties of the coatings were characterized using the colony counting method. The suspensions were shaken at 120 rpm and incubated at 37°C or 30°C for 18 h, and each 20 μL diluted bacterial suspension was taken for colony counting by spreading on the solid medium plate and incubating overnight at different temperature conditions. The CLSM (Zeiss Observer Z1, Germany) was applied to determine the fluorescent assay
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