The adhesion of proteins and marine microorganisms onto surfaces often leads to biofouling which is an unwanted, invasive and persistent microbial mediated surface degradation phenomenon. In this process, biomolecules and micro/large organisms accumulate irreversibly, which poses a major threat to various applications such as marine industrial equipment [1], [2], [3], biological implants [4], and biosensors [5]. Using surface antifouling coatings is the simplest and most effective antifouling technology [6]. However, due to the strict environmental protection requirements, many effective antibacterial substances cannot be used, such as tin and lead [7].

Many methods have been proposed to address surface fouling, which mainly fall into two categories: surface microstructure biomimetic antifouling surfaces and surface modification with antifouling agents [8], [9]. Surface microstructure-based antifouling aims to create antifouling surfaces with specific micro/nano structures by emulating the micro/nano structures on the surfaces of natural organisms. Nevertheless, these surfaces typically suffer from shortcomings including intricate processing, inadequate structural replication, and high costs [10], [11], [12]. As a result, their extensive application in the area of ship hull antifouling remains challenging. Surface modification with antifouling agents achieve the effect by developing various surface coatings, including fouling release coatings (FRC) [13], low surface energy coatings [14], zwitterionic hydrogels [15] and self-polishing copolymer (SPC) coatings [16], which have been employed to mitigate biofouling; however, these methods often fail to offer long-term solutions due to issues such as environmental toxicity, coating stability and the development of resistance among organisms [17], [18]. Consequently, there is an urgent need for innovative and sustainable approaches to combat biofouling on marine structures.

Recent studies have highlighted the potential of antimicrobial peptides (AMPs) derived from marine organisms as a promising alternative for the prevention of surface biofouling [19], [20]. AMPs exhibit broad-spectrum antibacterial properties and have been successfully utilized in various applications, including medical implants and food packaging, due to their efficacy against diverse pathogens [21]. The present study results have demonstrated the biocompatibility and antibacterial efficacy of AMPs, making them suitable candidates for surface modifications aimed at reducing biofouling [22], [23], [24]. Antibacterial peptides are mainly combined onto the substrate surface through chemical grafting methods. That is, antibacterial peptide molecules are grafted onto the material surface through chemical reactions, which changes the chemical properties of the surface, endowing the surface with antifouling properties such as resistance to protein adsorption, thus achieving the purpose of antifouling. The molecular structure of dopamine contains catechol groups and amino groups. In an alkaline environment, dopamine undergoes an auto-oxidation reaction, generating polydopamine (PDA) and some quinone intermediates [22], [25]. Quinone substances have strong oxidizing properties and can react with biological macromolecules such as proteins and lipids on the cell walls and membranes of bacteria, destroying the integrity and permeability of the cell membrane, causing the leakage of intracellular substances, and ultimately leading to the death of bacteria [26]. Generally speaking, within a certain range, as the pH value increases, the auto- oxidation rate of dopamine accelerates, the production of antibacterial active substances such as quinones increases, and the antibacterial performance is enhanced [27]. There is a positive correlation between the dopamine concentration and the antibacterial performance. A higher concentration of dopamine can produce more antibacterial active quinone substances and form a thicker antibacterial coating on the material surface, thus more effectively inhibiting the growth of bacteria [28].

This study employed dopamine as a coupling agent to immobilize antimicrobial peptides derived from marine organisms onto the surface of stainless steel. The surface physicochemical properties were characterized using relevant instruments. The antibacterial/antialgal properties and the antifouling mechanisms of the surface were analyzed through bacterial and algal adhesion experiments. This work provides new ideas and methods for the antifouling of ship hull surfaces.