Functionalization of Polydopamine via the Aza-Michael Reaction for Antimicrobial Interfaces

Abstract

Polydopamine (pDA) coatings afford tremendous versatility due to their capabilities to provide substrate-independent functionalization with a wide range of amine- and thiol-containing molecules. In this work, we developed a new and facile conjugation approach to the formation of β-amino carbonyl linkages between pDA and acrylate/acrylamide molecules via the aza-Michael reaction. Sulfobetaine acrylamide (SBAA), sulfobetaine methacrylate (SBMA), and poly(ethylene glycol) methacrylate (PEGMA) were employed to graft onto pDA films, giving rise to formation of antifouling coatings. Because of the universal adhesive property of pDA, the coating strategy was applied to different substrates, including TiO2, gold, SiO2, Nitinol alloy, polystyrene, and poly(dimethylsiloxane). The variation of surface chemistry and surface wettability upon pDA modification and subsequent conjugation was monitored with X-ray photoelectron spectroscopy (XPS) and water contact angle measurements. Antifouling properties of coatings were challenged by three common Gram-negative and Gram-positive bacteria. Cytocompatibility of the coatings with NIH-3T3 fibroblasts was accessed using MTT assay. The results showed that pDA coatings grafted with SBAA exhibited superhydrophilicity and excellent fouling resistance likely due to the high chemical reactivity of acrylamide, leading to high grafting density. In addition, dual functional coatings containing passive and active antibacterial components were constructed through the in situ deposition of antimicrobial agent, silver nanoparticles, in pDA, followed by the grafting of SBAA for bacterial repellence. The composite coatings allowed reducing adsorption of E. coli by >95%, while killing attached bacteria by up to 98% upon the releasing of Ag(+) ions as measured by inductively coupled plasma mass spectrometry. Consequently, this work paves a new avenue to the grafting strategy to engineer pDA and to the functional bioinspired antifouling interfaces in a substrate-independent fashion.

In Situ Infrared Spectroscopic Monitoring and Characterization of the Growth of Polydopamine (PDA) Films

“…As mentioned before, the PDA surfaces contain a rich variety of functional groups (e.g., OH, NH 2 , or CO), which allow the further versatile modification for applications in biomedical or bio‐related fields. Via a Schiff base reaction or Michael‐type addition reaction, the amine (NH 2 ) or thiol group (SH) terminated organic molecules in particular biomolecules (e.g., cysteine‐modified protein or peptide) can be immobilized on the PDA surfaces. Following this functionalization route, bio‐active, or bio‐inert interfaces can be constructed .…”

Chemistry of Polydopamine – Scope, Variation, and Limitation

“…[65c] Scheme 18. Reactions of PDA at amino groups: acylation, [65c,81,82] azomethine formation, [84] aza-Michael addition, [86] diazo transfer to azido groups, [87a] sulfonation, [87b] reaction with NO to PDA-diazeniumdiolate. [87c] Reaction of a PDA-coating with 1,3,5-benzenetricarbonyl trichloride in organic media resulted in amide formation.…”

“…The amino groups of PDA can undergo Aza-Michael-reactions as shown with acryl amides and acrylates (Scheme 18). [86] A chemical proof for the existence of uncyclized DA units in PDA was provided by diazo transfer reaction that can only occur at primary amino groups transforming them into azido groups (Scheme 18). The resulting PDA derivative was used to perform Cu-assisted CuAAC click reaction to 1,2,3-triazoles with alkyne species containing practically interesting entities.…”

Multifunctional and Stimuli‐Responsive Polydopamine Nanoparticle‐Based Platform for Targeted Antimicrobial Applications

“…Rather, polydopamine has mostly been used as coatings for rendering surfaces with antimicrobial properties, or as photothermally active biocidal film to prevent fouling. [30][31][32][33] As it is easier to thermally kill mammalian cells than bacteria, localized photothermal heating (i.e., focused on areas in close proximity to the pathogen surface) is required for in vivo applications, to avoid damaging the surrounding mammalian cells. [16,34] An effective strategy involves modifying the surface of PdNP with bacterial targeting molecules.…”