To meet the demand for more environmentally friendly antifouling coatings and to improve fouling-resistant coatings with both "offense" and "defense" functionalities, polysaccharides (PSa)-based self-polishing multilayer coatings were developed for combating biofouling. Dextran aldehyde (Dex-CHO) and carboxymethyl chitosan (CMCS) were synthesized and alternatively incorporated via imine linkage into the multilayer coating in layer-by-layer (LbL) deposition. Surface plasmon resonance (SPR) technique was utilized to monitor the LbL assembly process. With increasing number of assembled bilayers, the antifouling performances against bovine serum albumin (BSA) adsorption, bacterial (S. aureus and E. coli) adhesion, and alga (Amphora cof feaeformis) attachment improved steadily. The self-polishing ability of the multilayer coatings was achieved via cleavage of pH-responsive imine linkage under acidic environments. As such, dense bacterial adhesion induced detachment of the outmost layer of the coatings. The efficacies of antifouling and antimicrobial adhesion were thus enhanced by the self-polishing ability of the multilayer coatings. Therefore, the LbL-deposited self-polishing dextran/chitosan multilayer coatings offer an environmentally friendly and sustainable alternative for combating biofouling in aquatic environments.

Controlled architecture of bifunctional polymers on surfaces is highly challenged because of the stringent reaction conditions or tedious operations required for surface modification. Herein, a simple and effective method was developed to assemble zwitterionic and cationic binary polymer brushes onto polydopamine-anchored stainless steel (SS) surfaces. Zwitterionic poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) was first graft polymerized from the functionalized SS surface via thiol−ene "click" reaction. Alkynyl-modified cationic poly(2-(methacryloyloxy) ethyl trimethylammonium chloride) (alkynyl-PMETA) was subsequently introduced via azide−alkyne "click" reaction. After the grafting of PMPC/PMETA binary polymer brushes, the resulting functionalized SS surfaces can cooperatively reduce the adhesion of Gram-positive bacteria Staphylococcus aureus (S. aureus) and Gram-negative bacteria Pseudomonas sp., as well as the attachment of microalgae Amphora coffeaeformis. In addition, the binary polymer brushes coatings were ascertained to be stable and durable after 30-day exposure to filtered seawater. Thus, surface functionalization with zwitterionic and cationic binary polymer brushes offers an environmentally friendly alternative for biofouling inhibition in the marine and aquatic environments. In addition, surface modification via dual "click" reactions provides another alternation for developing surface coatings with multifunctionalities.

Layer-by-layer (LBL) deposition of polyethylenimine-β-cyclodextrin (PEI-β-CD) and ferrocene-modified chitosan (Fc-CHT) via host–guest interaction chemistry was developed for the fabrication of low-fouling, antimicrobial, and biocorrosion inhibition multilayer coatings on stainless steel. An electrochemical method is proposed to monitor and determine the LBL deposition process. The resulting multilayer coatings exhibit good resistance to bacterial adhesion, including Pseudomonas sp. and Staphylococcus aureus, and microalgal attachment of Amphora coffeaeformis. Settlement of barnacle cyprids is also significantly reduced on the bilayer-coated substrates. As the number of assembled host–guest bilayers increases, the antifouling efficacy, antimicrobial efficiency, and antibiocorrosion performance also improve progressively. The stability and durability of the multilayer coatings were ascertained after a 30-day immersion treatment in seawater. Thus, the multilayer coatings deposited via LBL method are potentially useful as environmentally friendly coatings for combatting biofouling and biocorrosion in marine and aquatic environments.

Tannic acid and parasin I were deposited alternatively on stainless steel surface by Michael addition/Schiff base reaction-enabled layer-by-layer deposition technique.

It is highly desirable to develop new and more potent biocompatible antimicrobial agents to reduce the increasing risk of bacterial infection worldwide. To address this problem, we prepared a smart pH-sensitive polymer, poly(N′-citraconyl-2-(3-aminopropyl-N,Ndimethylammonium)ethyl methacrylate), or P(CitAPDMAEMA), which can undergo change in functionality from a biocompatible zwitterionic polymer to an antimicrobial cationic polymer at acidic bacterial infection sites. The precursor polymer, poly(2-(3-aminopropyl-N,Ndimethylammonium)ethyl methacrylate) (P(APDMAEMA)), was first prepared by reversible addition−fragmentation chain transfer (RAFT) polymerization, and then modified with citraconic anhydride to obtain the zwitterionic P(CitAPDMAEMA). P(CitAPDMAEMA) is zwitterionic at physiological pH and exhibits low hemotoxicity and good biocompatibility. However, P(CitAPDMAEMA) can change from neutral to cationic with decreasing pH because of the hydrolysis of citraconic amide under low pH conditions. This switch leads to pronounced bacteria binding of cationic P(CitAPDMAEMA) under acidic conditions of the infection sites and significantly inhibits the growth of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). These results indicate that P(CitAPDMAEMA) is potentially a new on-demand antimicrobial agent.