Substrate-Independent Photografting of Hyaluronic Acid for Antifouling Coatings.

This work introduces a substrate-independent method for covalently immobilizing pristine hyaluronic acid (HA) as an antifouling coating on various surfaces. A tyrosine-conjugated perfluorophenyl azide (Tyr-PFPA) was synthesized, containing a tyrosine moiety that undergoes tyrosinase-mediated oxidation to form a melanin-mimetic film on various substrates and a PFPA moiety that undergoes photolysis to generate nitrenes. The resulting poly(Tyr-PFPA) film enabled the covalent grafting of HA via simple photoirradiation following physical adsorption, forming a poly(Tyr-PFPA)-HA film.

Melanin-Inspired Maleimide Coatings on Various Substrates for Rapid Thiol Functionalization.

In this study, a substrate-independent maleimide film is developed that can be formed under mild aqueous conditions (pH 7.4), and which allows rapid and efficient external thiol immobilization onto the coated surfaces. For the coating block, tyrosine-conjugated maleimide (Tyr-Mal) containing a phenolic amine moiety is prepared as a substrate-independent dormant coating precursor, wherein the maleimide component permits a rapid Michael addition reaction with the thiol moiety of interest.

Fabrication of Versatile Antifouling Coatings Inspired by Melanogenesis Using a Tyrosine-Conjugated Carboxybetaine Derivative.

In this study, we developed zwitterionic surface coatings of carboxybetaine by mimicking natural melanogenesis. We synthesized an unnatural tyrosine-conjugated carboxybetaine (Tyr-CB) that undergoes melanin-like oxidation upon treatment with tyrosinase under various aqueous conditions. The thickness of the resulting poly(Tyr-CB) film was tuned by adjusting the pH during the coating process.

Formation of Antifouling Brushes on Various Substrates Using a Melanin-Inspired Initiator Film.

In this study, we developed a substrate-independent initiator film that can undergo surface-initiated polymerization to form an antifouling brush. Inspired by the melanogenesis found in nature, we synthesized a tyrosine-conjugated bromide initiator (Tyr-Br) that contains phenolic amine groups as the dormant coating precursor and α-bromoisobutyryl groups as the initiator. The resultant Tyr-Br was stable under ambient air conditions and underwent melanin-like oxidation only in the presence of tyrosinase to form an initiator film on various substrates.

Antifouling Surface Coating on Various Substrates by Inducing Tyrosinase-Mediated Oxidation of a Tyrosine-Conjugated Sulfobetaine Derivative.

Inspired by the melanogenesis occurring in nature, we report tyrosinase-mediated antifouling surface coating by synthesizing a tyrosine-conjugated sulfobetaine derivative (Tyr-SB). Synthetic Tyr-SB contains zwitterionic sulfobetaine and tyrosine, whose phenolic amine group acts as a dormant coating precursor. In contrast to catecholamine derivatives, tyrosine derivatives are stable against auto-oxidation and are enzymatically oxidized only in the presence of tyrosinase to initiate melanin-like oxidation.

Development of Universal and Clickable Film by Mimicking Melanogenesis: On-Demand Oxidation of Tyrosine-Based Azido Derivative by Tyrosinase.

A tyrosine-based azido derivative (TBAD) that permits both substrate-independent surface coating and clickable film functionalization by mimicking natural melanogenesis is synthesized here. In contrast to catechol derivatives, which are generally susceptible to oxidation by air under ambient conditions, the monophenol-based TBAD remains stable under alkaline and neutral conditions and is activated to oxidized quinone in situ by tyrosinase to initiate melanin-like polymerization. The resulting poly(TBAD) film can be formed on various substrates including noble metals, metal oxides, and synthetic polymers, which can undergo click reaction with terminal alkyne moieties on the entire surface or a specific region through Cu(I)-catalyzed azide-alkyne cycloaddition.

Highly stable graphene oxide composite nanofiltration membrane.

Graphene oxide (GO) based membranes are promising for advanced nanofiltration in water treatments but there is a need to improve water flux and membrane stability. Although the interlayer distance of GO membranes can be expanded using intercalants to improve permeability, achieving uniform intercalation without the added complication of water-induced swelling is challenging. Herein, we report the fabrication of GO hybrid lamellar membranes with controllable layer structures to achieve high performance in nanofiltration.