Dicky Pranantyo

Tea stains-inspired initiator primer for surface grafting of antifouling and antimicrobial polymer brush coatings.

Inspired by tea stains, plant polyphenolic tannic acid (TA) was beneficially employed as the primer anchor for functional polymer brushes. The brominated TA (TABr) initiator primer was synthesized by partial modification of TA with alkyl bromide functionalities. TABr with trihydroxyphenyl moieties can readily anchor on a wide range of substrates, including metal, metal oxide, polymer, glass, and silicon. Concomitantly, the alkyl bromide terminals serve as initiation sites for atom transfer radical polymerization (ATRP). Cationic [2-(methacryloyloxy)ethyl]trimethylammonium chloride (META) and zwitterionic 2-methacryloyloxyethyl phosphorylcholine (MPC) and N-(3-sulfopropyl)-N-(methacryloxyethyl)-N,N-dimethylammonium betaine (SBMA) were graft-polymerized from the TABr-anchored stainless steel (SS) surface. The cationic polymer brushes on the modified surfaces are bactericidal, while the zwitterionic coatings exhibit resistance against bacterial adhesion. In addition, microalgal attachment (microfouling) and barnacle cyprid settlement (macrofouling) on the functional polymer-grafted surfaces were significantly reduced, in comparison to the pristine SS surface. Thus, the bifunctional TABr initiator primer provides a unique surface anchor for the preparation of functional polymer brushes for inhibiting both microfouling and macrofouling.

Synthesis of catechol and zwitterion-bifunctionalized poly(ethylene glycol) for the construction of antifouling surfaces

The synthesis of catechol-containing small molecules and macromolecules always requires multiple reaction steps, coupling agents, or enzymes. In this study, a simple and scalable strategy for the preparation of catechol-containing poly(ethylene glycol) (CaPEG) by epoxide–amine polymerization of PEG diglycidyl ether with dopamine is described. The as-formed tertiary amine groups in the backbone of CaPEG can be converted into sulfobetaine structures in an alkylsulfonation step, leading to the formation of catechol and zwitterion-bifunctionalized PEG (SBCaPEG). The resulting catechol-containing CaPEG and SBCaPEG can be anchored on various substrate surfaces, including stainless steel (SS), titanium and silicon wafer, under mild conditions. Since SS is susceptible to fouling by a variety of microorganisms, the antifouling properties of the polymer-coated SS surfaces are studied in detail. The CaPEG- and SBCaPEG-coated SS surfaces effectively reduced the adsorption of protein (albumin–fluorescein isothiocyanate conjugate and bovine plasma fibrinogen), as well as the adhesion of bacteria (Pseudomonas sp. and Escherichia coli) and microalgae (Amphora coffeaeformis), as compared to that of the pristine SS surface. In comparison with the CaPEG-coated SS surfaces, the zwitterionic SBCaPEG-coated SS surfaces exhibited even better antifouling efficiencies.

Layer-by-layer deposition of antifouling coatings on stainless steel via catechol-amine reaction

Stainless steel (SS) has been widely used as a construction material in maritime structures due to its good corrosion resistance. However, bacteria, algae, barnacles and other marine organisms can readily adhere to its surface in the process of biofouling, leading to serious structure failures and economic losses. In this work, layer-by-layer (LBL) deposition of functional polymer coatings on SS surface provides an alternative approach to combating marine fouling. The catechol-containing antifouling copolymer of dopamine methacrylamide and poly(ethylene glycol) methyl ether methacrylate (P(DMA-co-PEGMEMA)), and amino-rich branched poly(ethyleneimine) (PEI) were assembled sequentially on the SS surface via catechol-amine reaction in a LBL manner. The PEI/P(DMA-co-PEGMEMA) multiple bilayer-coated SS surfaces can effectively reduce the adhesion of bacteria and microalgae (microfouling), and settlement of barnacle cyprids (macrofouling), as compared to the pristine SS surface. The antifouling efficiencies of PEI/P(DMA-co-PEGMEMA) bilayer-coated SS surfaces were also significantly higher than that of the P(DMA-co-PEGMEMA) monolayer-coated SS surface.

Photoinduced anchoring and micropatterning of macroinitiators on polyurethane surfaces for graft polymerization of antifouling brush coatings

Poly[3-azido-2-(2-bromo-2-methylpropanoyloxy)propyl methacrylate] (PAzBrMA) was synthesized as the macroinitiator and anchor for a functional polymer brush coating on polyurethane (PU) films. Ring-opening reaction of the epoxide group of poly(glycidyl methacrylate) with sodium azide produced the hydroxyl and azide functional groups. The hydroxyl groups were substituted with 2-bromoisobutyryl bromide to introduce the alkyl halide initiator. For anchoring, ultraviolet irradiation was applied to convert the azide groups of PAzBrMA physically coated on the PU surface into nitrene intermediates. The nitrene groups reacted with hydrocarbon moieties on the PU surface through hydrogen abstraction to form amine linkages. A photomask could then be employed to create a patterned surface during irradiation. Thus, the anchoring of a PAzBrMA macroinitiator can be achieved under mild conditions, without the use of strong solvents and high temperatures, which will swell or degrade the PU substrates. Finally, 2-hydroxyethyl methacrylate (HEMA) and poly(ethylene glycol) methacrylate (PEGMA) are graft-polymerized on the PAzBrMA-anchored PU film by surface-initiated atom transfer radical polymerization. In comparison with the pristine PU surface, the PU surfaces with grafted HEMA and PEGMA brush coatings were effective in reducing bovine serum albumin adsorption (protein fouling), adhesion of Staphylococcus epidermidis and Pseudomonas sp. (microfouling), and barnacle cyprid settlement (macrofouling). The present surface modification approach provides a simple and versatile means for micropatterning and functionalization of the polymer surfaces.

Tannic acid anchored layer-by-layer covalent deposition of parasin I peptide for antifouling and antimicrobial coatings

Tannic acid can serve as an initiator anchor for surface functionalization. Parasin I is an antimicrobial peptide derived from histone. Multilayer coatings on stainless steel were prepared by alternative deposition of these two materials via the Michael addition/Schiff base reaction-enabled layer-by-layer (LBL) deposition technique. The as-prepared multilayer coating exhibits good resistance to Gram-negative bacteria (Pseudomonas sp. and E. coli), Gram-positive bacteria (S. aureus and S. epidermidis) and microalgae (Amphora coffeaeformis). The antifouling and antimicrobial efficacy increase with an increasing number of the assembled multilayers. The stability and durability of multilayer coatings were also ascertained by prolonged exposure to seawater. The LBL covalently deposited multilayer coatings are thus potentially useful as effective and environmental benign coatings to combat biofouling in marine and aqueous environments.

Increasing bacterial affinity and cytocompatibility with four-arm star glycopolymers and antimicrobial α-polylysine

A series of four-arm star copolymers, incorporating glycopolymer and antimicrobial polypeptide domains, was developed in the design of forthcoming anti-infective agents. Mannose, glucose, and galactose-based glycopolymers with a variety of well-defined chain lengths were prepared via atom transfer radical polymerization, whereas linear α-polylysine was prepared via ring-opening polymerization of N-carboxyanhydride monomers. Copper-catalyzed azide–alkyne cycloaddition was employed for ‘click’ conjugation of the glycopolymer arms and the polypeptide chains. The glycopolymer–polypeptide conjugates were non-hemolytic and exhibited higher cytocompatibility than the linear α-polylysine. The conjugates with shorter chains of mannose-based glycopolymer arms showed an enhanced bactericidal efficacy against Gram-negative and Gram-positive bacteria, with a therapeutic selectivity half of that of the linear α-polylysine. The pendant mannose moieties of the conjugates increased microbial targeting due to their specific affinity for bacterial surfaces, and binding competition with free mannopyranoside was demonstrated. Therefore, the molecular combination of glycopolymers and polypeptides without loss of their respective activities provides an interesting concept in the design of antimicrobial agents to combat infectious disease.

Antifouling coatings based on covalently cross-linked agarose film via thermal azide-alkyne cycloaddition.

Coatings based on thin films of agarose-poly(ethylene glycol) (Agr-PEG) cross-linked systems are developed as environmentally-friendly and fouling-resistant marine coatings. The Agr-PEG cross-linked systems were prepared via thermal azide-alkyne cycloaddition (AAC) using azido-functionalized Agr (AgrAz) and activated alkynyl-containing poly(2-propiolamidoethyl methacrylate-co-poly(ethylene glycol)methyl ether methacrylate) P(PEMA-co-PEGMEMA) random copolymers as the precursors. The Agr-PEG cross-linked systems were further deposited onto a SS surface, pre-functionalized with an alkynyl-containing biomimetic anchor, dopamine propiolamide, to form a thin film after thermal treatment. The thin film-coated SS surfaces can effectively reduce the adhesion of marine algae and the settlement of barnacle cyprids. Upon covalent cross-linking, the covalently cross-linked Agr-PEG films coated SS surfaces exhibit good stability in flowing artificial seawater, and enhanced resistance to the settlement of barnacle cyprids, in comparison to that of the surfaces coated with physically cross-linked AgrAz films.

Tailoring Polyelectrolyte Architecture To Promote Cell Growth and Inhibit Bacterial Adhesion

An important challenge facing the application of implanted biomaterials for tissue engineering is the need to facilitate desirable tissue interactions with the implant while simultaneously inhibiting bacterial colonization, which can lead to implant-associated infection. In this study, we explore the relevance of the physical parameters of polyelectrolyte multilayers, such as surface charge, wettability, and stiffness, in tissue cell/surface and bacteria/surface interactions, and investigate the tuning of the multilayer architecture to differentially control such interactions. Polyions with different side-chain chemical structures were paired with polyethylenimine to assemble multilayers with parallel control over surface charge and wettability under controlled conditions. The multilayers can be successfully cross-linked to yield stiffer (the apparent Youngs modulus was increased more than three times its original value) and more stable films while maintaining parallel control over surface charge and wettability. The initial adhesion and proliferation of 3T3 fibroblast cells were found to be strongly affected by surface charge and wettability on the non-cross-linked multilayers. On the other hand, these cells adhered and proliferated in a manner similar to those on the cross-linked multilayers (apparent Youngs modulus ∼2 MPa), regardless of surface charge and wettability. In contrast, Staphylococcus aureus ( S. aureus) and Escherichia coli ( E. coli) adhesion was primarily controlled by surface charge and wettability on both cross-linked and non-cross-linked multilayers. In both cases, negative charge and hydrophilicity inhibited their adhesion. Thus, a surface coating with a relatively high degree of stiffness from covalent cross-linking coupled with negative surface charge and high wettability can serve as an efficient strategy to enhance host cell growth while resisting bacterial colonization.

Dominant Albumin–Surface Interactions under Independent Control of Surface Charge and Wettability

Understanding protein adsorption behaviors on solid surfaces constitutes an important step toward development of efficacious and biocompatible medical devices. Both surface charge and wettability have been shown to influence protein adsorption attributes, including kinetics, quantities, deformation, and reversibility. However, determining the dominant interaction in these surface-induced phenomena is challenging because of the complexity of inter-related mechanisms at the liquid/solid interface. Herein, we reveal the dominant interfacial forces in these essential protein adsorption attributes under the influence of a combination of surface charge and wettability, using quartz crystal microbalance with dissipation monitoring and atomic force microscopy-based force spectroscopy on a series of model surfaces. These surfaces were fabricated via layer-by-layer assembly, which allowed two-dimensional control of surface charge and wettability with minimal cross-parameter dependency. We focused on a soft globular protein, bovine serum albumin (BSA), which is prone to conformational changes during adsorption. The information obtained from the two techniques shows that both surface charge and hydrophobicity can increase the protein-surface interaction forces and the adsorbed amount. However, surface hydrophobicity triggered a greater extent of deformation in the adsorbed BSA molecules, leading to more dehydration, spreading, and resistance to elution by ionic strength changes regardless of the surface charge. The role played by the surface charge in the adsorbed protein conformation and extent of desorption induced by changes in the ionic strength is secondary to that of surface hydrophobicity. These findings advance the understanding of how surface chemistry and properties can be tailored for directing protein-substrate interactions.