Functionalization of magnetic nanowires by charged biopolymers.

We report on a facile method for the preparation of biocompatible and bioactive magnetic nanowires. The method consists of the direct deposition of polysaccharides by layer-by-layer (LbL) assembly onto a brush of metallic nanowires obtained by electrodeposition of the metal within the nanopores of an alumina template supported on a silicon wafer. Carboxymethylpullulan (CMP) and chitosan (CHI) multilayers were grown on brushes of Ni nanowires; subsequent grafting of an enzyme was performed by conjugating free amine side groups of chitosan with carboxylic groups of the enzyme. The nanowires are finally released by a gentle ultrasonic treatment. Transmission electron microscopy, electron energy-dispersive loss spectroscopy, and x-ray photoelectron spectroscopy indicate the formation of an homogeneous coating onto the nickel nanowires when one, two, or three CMP/CHI bilayers are deposited. This easy and efficient route to the biochemical functionalization of magnetic nanowires could find widespread use for the preparation of a broad range of nanowires with tailored surface properties.

Determination of substituents distribution in carboxymethylpullulans by NMR spectroscopy.

The distribution of carboxymethyl substituents in the alpha-(1 --> 6)-linked maltotriosyl repeating units of a carboxymethylpullulan (CMP) series was investigated by high resolution NMR spectroscopy on very short oligomers (DPn = 1.2-1.5) obtained by acid hydrolysis. A series of 2D NMR experiments on parent pullulan, hydrolysed pullulan and CMP was used to assign the proton and carbon chemical shifts of CMP acid hydrolysates. The degree of substitution (DS) and the relative distribution of -CH2COONa groups at OH-2, OH-3, OH-4 and OH-6 of glucose residues (DSi) were determined from 1H NMR measurements. From a set of CMP samples, widely different in degree of substitution, it was observed that the substitution at C-2 is predominant and decreases according to the order C-2 > C-3 > C-6 > C-4. Taking into account the availability of each OH group in the parent pullulan, an order of relative reactivity of hydroxyl groups is defined according to the relation: Ri = DSi/ni, where ni is the number of free OH groups in a maltotriose unit (MTU) for a given site C-i, the reactivity order was found to be OH-2 > OH-4 > OH-6 > OH-3.

Antibacterial surfaces developed from bio-inspired approaches.

Prevention of bacterial adhesion and biofilm formation on the surfaces of materials is a topic of major medical and societal importance. Various synthetic approaches based on immobilization or release of bactericidal substances such as metal derivatives, polyammonium salts and antibiotics were extensively explored to produce antibacterial coatings. Although providing encouraging results, these approaches suffer from the use of active agents which may be associated with side-effects such as cytotoxicity, hypersensibility, inflammatory responses or the progressive alarming phenomenon of antibiotic resistance. In addition to these synthetic approaches, living organisms, e.g. animals and plants, have developed fascinating strategies over millions of years to prevent efficiently the colonization of their surfaces by pathogens. These strategies have been recently mimicked to create a new generation of bio-inspired biofilm-resistant surfaces. In this review, we discuss some of these bio-inspired methods devoted to the development of antibiofilm surfaces. We describe the elaboration of antibacterial coatings based on natural bactericidal substances produced by living organisms such as antimicrobial peptides, bacteriolytic enzymes and essential oils. We discuss also the development of layers mimicking algae surfaces and based on anti-quorum-sensing molecules which affect cell-to-cell communication. Finally, we report on very recent strategies directly inspired from marine animal life and based on surface microstructuring.