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.
The effects of processing parameters on the laser beam welded dissimilar steel joints has been investigated. The following conclusions can be drawn from the study: (1) The power and speed combinations should be selected to minimize heat input with the requirement of producing a satisfactory weld bead with reliable quality; (2) Root opening can be used for composition adjustment by feeding the appropriate amount of filler metal, e.g., the filler metal content in the weld metal can be increased by increasing the root opening accordingly. This can be used to exploit certain special applications in which an increased alloy element content is required. However, a 0.2-mm root opening with sufficient wire feed rate is recommended in order to obtain a fully austenitic structure in this study with taking full advantage of the process. (3) Laser beam alignment should be placed in the weld centerline or on the austenitic stainless steel side to a maximum of 0.25 mm in order to control the dilution and avoid loss of alloying elements, which in turn leads to the formation of a hard martensitic phase in the weld metals. (4) Overall, the investigation indicates that correct selection of processing parameters not only determines themore » weld quality, but also takes full advantage of the process.« less
The in vitro biocompatibility of a novel magnesium phosphate whisker (M-PW) was evaluated by real-time cellular analysis (RTCA) and Annexin-V/PI double marking methods, and its antibacterial property was evaluated by co-culture method. Results show that the in vitro biocompatibility of the MPW decreased with the increase of M-PW in the suspensions. It possessed excellent in vitro biocompatibility for the suspensions containing 500 μg/mL or lower amount of the M-PW. It had no toxic effect on osteoblast cells for the suspension with 50 and 200 μg/mL of M-PW respectively. The antibacterial efficacy of the suspensions increased with the increasing amount of MPW. The antibacterial efficacy against Escherichia coli and Staphylococcus aureus achieved 96.84% and 99.93% respectively for the suspension with 500 μg/mL of M-PW, demonstrating that the novel phosphorous-magnesium whisker possesses excellent antibacterial property.
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