Surfactant-like Peptide Self-Assembled into Hybrid Nanostructures for Electronic Nose Applications.

An electronic nose (e-nose) utilizes a multisensor array, which relies on the vector contrast of combinatorial responses, to effectively discriminate between volatile organic compounds (VOCs). In recent years, hierarchical structures made of nonbiological materials have been used to achieve the required sensor diversity. With the advent of self-assembling peptides, the ability to tune nanostructuration, surprisingly, has not been exploited for sensor array diversification. In this work, a designer surfactant-like peptide sequence, CG7-NH2, is used to fabricate morphologically and physicochemically heterogeneous "biohybrid" surfaces on Au-covered chips. These multistructural sensing surfaces, containing immobilized hierarchical nanostructures surrounded by self-assembled monolayers, are used for the detection and discrimination of VOCs. Through a simple and judicious design process, involving changes in pH and water content of peptide solutions, a five-element biohybrid sensor array coupled with a gas-phase surface plasmon resonance imaging system is shown to achieve sufficient discriminatory capabilities for four VOCs. Moreover, the limit of detection of the multiarray system is bench-marked at <1 and 6 ppbv for hexanoic acid and phenol (esophago-gastric biomarkers), respectively. Finally, the humidity effects are characterized, identifying the dissociation rate constant as a robust descriptor for classification, further exemplifying their efficacy as biomaterials in the field of artificial olfaction.

Metallic Conductive Nanowires Elaborated by PVD Metal Deposition on Suspended DNA Bundles.

Metallic conductive nanowires (NWs) with DNA bundle core are achieved, thanks to an original process relying on double-stranded DNA alignment and physical vapor deposition (PVD) metallization steps involving a silicon substrate. First, bundles of DNA are suspended with a repeatable process between 2 µm high parallel electrodes with separating gaps ranging from 800 nm to 2 µm. The process consists in the drop deposition of a DNA lambda-phage solution on the electrodes followed by a naturally evaporation step. The deposition process is controlled by the DNA concentration within the buffer solution, the drop volume, and the electrode hydrophobicity. The suspended bundles are finally metallized with various thicknesses of titanium and gold by a PVD e-beam evaporation process. The achieved NWs have a width ranging from a few nanometers up to 100 nm. The electrical behavior of the achieved 60 and 80 nm width metallic NWs is shown to be Ohmic and their intrinsic resistance is estimated according to different geometrical models of the NW section area. For the 80 nm width NWs, a resistance of about few ohms is established, opening exploration fields for applications in microelectronics.

Immobilization of proteases on chitosan for the development of films with anti-biofilm properties.

Bacterial resistance due to biofilm formation-particularly Staphylococci biofilms-is associated with multiple problems in medical settings where biofilms can colonize medical indwelling devices and cause nosocomial infections. It was against this backdrop that we explored the anti-biofilm activities of a set of proteases against biofilm formation by Staphylococcus aureus, Listeria monocytogenes and Pseudomonas aeruginosa. The selected screened enzymes were immobilized on chitosan to obtain films with anti-biofilm activities. Immobilization efficiency was about 94% for protease from Bacillus licheniformis and reached up to 96% for Neutrase. In vitro assays performed in brain heart infusion (BHI) broth using the Biofilm Ring Test highlighted that immobilized enzymes were efficient against biofilms of Staphylococci cultures, especially protease from B. licheniformis and Neutrase from Bacillus amyloliquefaciens.