A robust antibacterial coating for stainless steel

Conference (2010, March 23)

Because of corrosion, chemical resistance, relevant mechanical and esthetical properties, stainless steel is widely used in the daily life, not only in the building industry but also in the food industry ... [more ▼]

Because of corrosion, chemical resistance, relevant mechanical and esthetical properties, stainless steel is widely used in the daily life, not only in the building industry but also in the food industry, the appliances or in the medical field, including implants in orthopedic surgery. However, stainless steel is unable to prevent bacteria from adhering, proliferating and forming a resistant biofilm. Therefore, surface modification is needed for providing the metal surface with antibacterial properties. The scientific literature is very rich in describing various methods for imparting antibacterial properties to different inorganic supports. However, the activity of the coating is generally time limited by the diffusion of the biocide in the environment. Novel robust and stable antibacterial coatings on stainless steel are thus highly desirable for the durability of the functionality. In this communication, we report on an all-in-one approach to prepare robust antimicrobial films on stainless steel using the layer-by-layer deposition of polyelectrolytes. Novel biocidal multilayered polyelectrolyte films in which the polycationic layer is silver loaded and bears 3,4-dihydroxyphenylalanine (DOPA), known as a promoter of adhesion to inorganic surfaces, were deposited onto stainless steel. DOPA was incorporated in the polycationic chains by radical copolymerisation of N-methacrylated DOPA with the commercially available quaternary ammonium salt of 2-(dimethylamino)ethyl methacrylate (DMAEMA+). Polystyrene sulfonate (PSS) was the polyanionic constituent of the films. In order to boost the antibacterial activity of the polycationic layer, AgNO3 was added to the aqueous solution of P(DOPA)-co-P(DMAEMA+), which resulted in the in-situ formation of silver based nanoparticles (Ag° and AgCl) that are sources of biocial Ag+. The layer-by-layer deposition of aqueous P(DOPA)-co-P(DMAEMA+)/AgCl/Ag0 suspension and aqueous solution of PSS provides stainless steel with high antibacterial activity against Gram-negative E. Coli bacteria. Moreover, after silver depletion, films retain some antimicrobial activity, thanks to the ammonium groups of the copolymer. We will also show how the antibacterial activity of the films can then be easily re-boosted. The multi-functionality of the P(DOPA)-co-P(DMAEMA+) is a key issue in this process (i) the DOPA co-units are anchored to stainless steel, (ii) these co-units reduce partly AgNO3 into Ag0 nanoparticles and stabilize them by chelation, (iii) the chloride counter-anions react with AgNO3 by ionic exchange, leading to the in situ formation of AgCl particles, and (iv) the ammonium groups are responsible for permanent antibacterial activity. Besides the advantage of the all-in-one process, another major advantage of the approach proposed here is the implementation of the whole process of film formation, including the synthesis of P(DOPA)-co-P(DMAEMA+), in aqueous media under very mild conditions. It makes the strategy very attractive for industrial scaling-up and sustainability applications. [less ▲]

All-in-one strategy for the fabrication of antimicrobial biomimetic films on stainless steel

in Journal of Materials Chemistry (2009), 19

Here we report on an all-in-one approach to prepare robust antimicrobial films on stainless steel. The strategy is based on the layer-by-layer deposition of polyelectrolytes. A polycationic copolymer ... [more ▼]

Here we report on an all-in-one approach to prepare robust antimicrobial films on stainless steel. The strategy is based on the layer-by-layer deposition of polyelectrolytes. A polycationic copolymer bearing 3,4-dihydroxyphenylalanine units (DOPA, a major component of natural adhesives) was synthesized and co-deposited with precursors of silver nanoparticles as the first layer. The presence of DOPA units ensures a strong anchoring on the stainless steel substrate, and the silver nanoparticles are sources of biocidal Ag+, providing stainless steel with antimicrobial activity. We show that multilayered films, obtained by alternating this nanoparticle-loaded polycationic copolymer with polystyrene sulfonate, a commercial polyanion, results in stainless steel with high antibacterial activity against Gram-negative E. coli bacteria. The polycationic layers are a reservoir of Ag+ that can be reactivated after depletion. The whole process of film formation, including the synthesis of the copolymer, is conducted in aqueous media under very mild conditions, which makes it very attractive for industrial scale-up and sustainable applications. [less ▲]

AFM tips functionalized with a bio-inspired polymer

Poster (2009, May 14)

Core-Shell-Corona Micelles by PS-b-P2VP-b-PEO Copolymers: Focus on the Water-Induced Micellization Process

in Langmuir (2008), 24(7), 3009-3015

It is now well established that amphiphilic PS-b-P2VP-b-PEO linear triblock copolymers can form multilayered assemblies, thus core-shell-corona (CSC) micelles, in water. Micellization is triggered by ... [more ▼]

It is now well established that amphiphilic PS-b-P2VP-b-PEO linear triblock copolymers can form multilayered assemblies, thus core-shell-corona (CSC) micelles, in water. Micellization is triggered by addition of a small amount of water into a dilute solution of the PS-b-P2VP-b-PEO copolymer in a non-selective organic solvent. However, the phenomena that take place at the very beginning of this process are poorly documented. How these copolymer chains are perturbed by addition of water was investigated in this work by light and neutron scattering techniques and transmission electron microscopy. It was accordingly possible to determine the critical water concentration (CWC), the compactness of the nano-objects in solution, their number of aggregation, and their hydrodynamic diameter at each step of the micellization process. [less ▲]

Fast multiresponsive micellar gels from a smart ABC triblock copolymer

in Angewandte Chemie (International ed. in English) (2007), 46(42), 7988-7992

The triblock copolymer PS-b-P2VP-b-PEO undergoes simultaneous micellization and gelation, leading to high-storage-modulus materials that have fast responses to pH value, temperature, ionic strength, and ... [more ▼]

The triblock copolymer PS-b-P2VP-b-PEO undergoes simultaneous micellization and gelation, leading to high-storage-modulus materials that have fast responses to pH value, temperature, ionic strength, and shearing. The gel has a hierarchical structure with spherical core-shell-corona micelles, which, in turn, pack closely into an ordered cubic structure. [less ▲]

Synthesis, characterization and applications of pH-responsive core-shell-corona micelles in water

Doctoral thesis (2007)

ABC triblock copolymers self-organize into a wide variety of supramolecular structures in the bulk. However, their associative behavior in selective solvents has scarcely been studied. Within the search ... [more ▼]

ABC triblock copolymers self-organize into a wide variety of supramolecular structures in the bulk. However, their associative behavior in selective solvents has scarcely been studied. Within the search for new stimuli-responsive supramolecular architectures, our attention focused on a pH-responsive polystyrene-b-poly(2-vinylpyridine)-b-poly(ethylene oxide) (PS-b-P2VP-b-PEO) triblock copolymer. In addition to the synthesis of monodisperse spherical core-shell-corona (CSC) micelles, the reversibility and the cooperativity of the response to pH variations were studied, morphological transitions were induced and multi-responsive micellar gels were prepared. The micellization mechanism, the structure, the responsiveness and the internal organization of these new nanomaterials were investigated using a combination of transmission electronic microscopy, atomic force microscopy, light scattering, small-angle neutron and X-ray scattering, nuclear magnetic resonance and rheology. Finally, efforts were geared towards potential applications. The ability of PS-b-P2VP-b-PEO CSC micelles to encapsulate and release hydrophobic species was probed and gold nanoparticles were successfully synthesized within the P2VP layer of spherical and cylindrical micelles, which acted as nanoreactors. [less ▲]

Synthesis of poly(vinyl acetate)-b-polystyrene and poly(vinyl alcohol)-b-polystyrene copolymers by cobalt-mediated radical polymerization

in Journal of Polymer Science Part A-Polymer Chemistry (2007), 45(1), 81-89

Well-defined poly(vinyl acetate) macroinitiators, with the chains thus end-capped by a cobalt complex, were synthesized by cobalt-mediated radical polymerization and used to initiate styrene ... [more ▼]

Well-defined poly(vinyl acetate) macroinitiators, with the chains thus end-capped by a cobalt complex, were synthesized by cobalt-mediated radical polymerization and used to initiate styrene polymerization at 30 degrees C. Although the polymerization of the second block was not controlled, poly(vinyl acetate)-b-polystyrene copolymers were successfully prepared and converted into amphiphilic poly(vinyl alcohol)-b-polystyrene copolymers by the methanolysis of the ester functions of the poly(vinyl acetate) block. These poly(vinyl alcohol)-b-polystyrene copolymers self-associated in water with the formation of nanocups, at least when the poly(vinyl alcohol) content was low enough. [less ▲]

pH-Responsive diblock copolymers prepared by the dual initiator strategy

in Macromolecules (2006), 39(11), 3760-3769

Diblock copolymers poly(tetrahydrofuran-b-tert-butyl acrylate) (PTHF-b-PtBA) and poly(tetrahydrofuranb- 1-ethoxyethyl acrylate) (PTHF-b-PEEA) were successfully synthesized by the dual initiator 4 ... [more ▼]

Diblock copolymers poly(tetrahydrofuran-b-tert-butyl acrylate) (PTHF-b-PtBA) and poly(tetrahydrofuranb- 1-ethoxyethyl acrylate) (PTHF-b-PEEA) were successfully synthesized by the dual initiator 4-hydroxybutyl-2- bromoisobutyrate (HBBIB). The isobutyrate and alcohol function of HBBIB were used for the atom transfer radical polymerization of tBA ( or EEA) and the living cationic ring-opening polymerization of THF, respectively. Hydrolysis or thermolysis of the aforementioned diblock copolymers results in amphiphilic pH-responsive copolymers PTHF-b-poly( acrylic acid) ( PTHF-b-PAA). Matrix-assisted laser desorption/ ionization time-of-flight (MALDI-TOF) and nuclear magnetic resonance spectroscopy (H-1 NMR) were used to analyze the PTHF macroinitiator, while clear evidence for the formation of well-defined block copolymer structures was obtained by 1H NMR, gel permeation chromatography (GPC), and infrared spectroscopy (FT-IR). The amorphous PtBA block in PTHF-b-PtBA resulted in a decrease of the crystallinity and the melting point of PTHF, as shown by differential scanning calorimetry (DSC). Self-assembly of PTHF-b-PAA copolymers in water into aggregates and micelles when exposed to specific pH values was confirmed by dynamic light scattering, infrared, and NMR spectroscopies. [less ▲]

Synthesis of poly(vinyl acetate) and poly(vinyl alcohol) containing block copolymers by combination of cobalt-mediated radical polymerization and ATRP

in Macromolecules (2005), 38(23), 9488-9496

Poly(vinyl acetate) (PVAc) chains of a low polydispersity (Mw/Mn similar to 1.1-1.2) have been prepared by cobalt-mediated radical polymerization of vinyl acetate (VAc). They have been end-capped by an ... [more ▼]

Poly(vinyl acetate) (PVAc) chains of a low polydispersity (Mw/Mn similar to 1.1-1.2) have been prepared by cobalt-mediated radical polymerization of vinyl acetate (VAc). They have been end-capped by an activated bromide by addition of an alpha-bromoester or an alpha-bromoketone containing nitroxide and converted into effective macroinitiators for the atom transfer radical polymerization of styrene (Sty), ethyl acrylate, and methyl methacrylate. Because each block is formed by a controlled process, well-defined PVAc containing diblock copolymers are easily prepared. The PVAc-b-PS copolymers synthesized from alpha-bromoketone end-capped PVAc can be converted into well-defined poly(vinyl alcohol)-b-polystyrene amphiphiles by methanolysis of the poly(vinyl acetate) block. Self-association of an amphiphilic poly(vinyl alcohol)(3500)-b-polystyrene(16 600) in a (4/1) water/tetrahydrofuran mixture results in the formation of vesicles as observed by transmission electron microscopy. [less ▲]

ABC triblock copolymers for pH sensitive micelles

Poster (2005, June 01)