Substrate-independent adsorption of nanoparticles as anti-biofilm coatings.

Healthcare-associated infections are common causes of morbidity and mortality. Advanced nanotechnology provides a means of overcoming this problem, but it remains challenging to develop universal coating strategies for decorating antimicrobial nanomaterials onto various clinical devices. In this paper, we propose a general silane-based method for immobilizing monolayer metal nanoparticle (NP) arrays onto any type of substrate surface-especially for a diverse range of clinical implantable devices. The surface silanization was achieved simply through the adsorption of N1-(3-trimethoxysilylpropyl)diethylenetriamine (TMS), regardless of the material (polymer, metal, oxide) or morphology (flat, curved, textured) of the substrate, with no need for pretreatment or expensive instrumentation. Monolayers of various nanostructures (Ag, Au, and hollow Au NPs) were then decorated rapidly onto the TMS-treated substrates, thereby further functionalizing their surfaces. In particular, immobilization of the Ag NPs resulted in excellent anti-biofilm efficacy against three clinically life-threatening pathogens: Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus. Sustained release of Ag+ ions led to durable inhibition of bacterial attachment for up to 28 days. Studies with NIH3T3 fibroblasts revealed that the Ag NP arrays displayed no cytotoxicity toward mammalian cells. Overall, this universal coating process appears to be an innovative method for the surface-functionalization of diverse materials and devices employed in the fields of energy, sensing, and medicine-especially to prevent healthcare-associated infections arising from the use of clinical implantable devices in hospitals.

Food Quality Monitor: Paper-Based Plasmonic Sensors Prepared Through Reversal Nanoimprinting for Rapid Detection of Biogenic Amine Odorants.

This paper describes the fabrication of paper-based plasmonic refractometric sensors through the embedding of metal nanoparticles (NPs) onto flexible papers using reversal nanoimprint lithography. The NP-embedded papers can serve as gas sensors for the detection of volatile biogenic amines (BAs) released from spoiled food. Commercial inkjet papers were employed as sensor substrates-their high reflectance (>80%) and smooth surfaces (roughness: ca. 4.9 nm) providing significant optical signals for reflection-mode plasmonic refractometric sensing and high particle transfer efficiency, respectively; in addition, because inkjet papers have lightweight and are burnable and flexible, they are especially suitable for developing portable, disposable, cost-effective, eco-friendly sensing platforms. Solid silver NPs (SNPs), solid gold NPs (GNPs), and hollow Au-Ag alloyed NPs (HGNs) were immobilized on a solid mold and then transferred directly onto the softened paper surfaces. The particle number density and exposure height of the embedded NPs were dependent on two imprinting parameters: applied pressure and temperature. The optimal samples exhibited high particle transfer efficiency (ca. 85%), a sufficient exposure surface area (ca. 50% of particle surface area) presented to the target molecules, and a strong resonance reflectance dip for detection. Moreover, the HGN-embedded paper displayed a significant wavelength dip shift upon the spontaneous adsorption of BA vapors (e.g., Δλ = 33 nm for putrescine; Δλ = 24 nm for spermidine), indicating high refractometric sensitivity; in contrast, no visible spectroscopic responses were observed with respect to other possibly coexisting gases (e.g., air, N2, CO2, water vapor) during the food storage process, indicating high selectivity. Finally, the plasmonic sensing papers were used to monitor the freshness of a food product (salmon).