Rational Design of Amphiphilic Peptides and Its Effect on Antifouling Performance.

Biofouling, the unwanted adhesion of organisms to surfaces, has a negative impact on energy, food, water, and health resources. One possible strategy to fight biofouling is to modify the surface using a peptide-based coating that will change the surface properties. We reveal the importance of rational design and positioning of individual amino acids in an amphiphilic peptide sequence. By just manipulating the position of the amino acids within the peptide chain having the same chemical composition, we improved the antifouling performance of an amphiphilic peptide-based coating, Phe(4-F)-Lys-DOPA, by 30%. We have judiciously tailored the peptide configurations to achieve the best antifouling performance by (i) positioning the amino acid lysine adjacent to the DOPA moiety in the linear peptide chain for better adhesion, (ii) having a linear fluorinated N-terminal to improve the packing density of the film by straightening the peptide chain, and (iii) placing DOPA at the C-terminal. We have also compared the antifouling performances of amphiphilic, hydrophobic, hydrophilic, and alternately arranged peptides. Our results show a reduction of ∼80% in bacterial adhesion for an amphiphilic peptide-coated surface when compared to a bare titanium surface. This work provides important strategic design guidelines for future peptide-related materials that have effective antifouling properties.

Electrochemical Approach for Effective Antifouling and Antimicrobial Surfaces.

Biofouling, the adsorption of organisms to a surface, is a major problem today in many areas of our lives. This includes: (i) health, as biofouling on medical device leads to hospital-acquired infections, (ii) water, since the accumulation of organisms on membranes and pipes in desalination systems harms the function of the system, and (iii) energy, due to the heavy load of the organic layer that accumulates on marine vessels and causes a larger consumption of fuel. This paper presents an effective electrochemical approach for generating antifouling and antimicrobial surfaces. Distinct from previously reported antifouling or antimicrobial electrochemical studies, we demonstrate the formation of a hydrogen gas bubble layer through the application of a low-voltage square-waveform pulses to the conductive surface. This electrochemically generated gas bubble layer serves as a separation barrier between the surroundings and the target surface where the adhesion of bacteria can be deterred. Our results indicate that this barrier could effectively reduce the adsorption of bacteria to the surface by 99.5%. We propose that the antimicrobial mechanism correlates with the fundamental of hydrogen evolution reaction (HER). HER leads to an arid environment that does not allow the existence of live bacteria. In addition, we show that this drought condition kills the preadhered bacteria on the surface due to water stress. This work serves as the basis for the exploration of future self-sustainable antifouling techniques such as incorporating it with photocatalytic and photoelectrochemical reactions.