Use of hygiene protocols to control the spread of viruses in a hotel.

The goals of this study were to observe the spread of viruses in a hotel setting and to assess the effectiveness of a hygiene intervention in reducing their spread. Selected fomites in one hotel room were inoculated with bacteriophage ϕx-174, and fomites in a conference center within the same hotel were inoculated using bacteriophage MS2. Cleaning of the contaminated room resulted in the spread of viruses to other rooms by the housekeeping staff. Furthermore, viruses were transferred by hotel guests to the conference center and a communal kitchen area. Additionally, conference attendees transferred viruses from the conference center to their hotel rooms and a communal kitchen area. This study demonstrated how viruses can be spread throughout a hotel setting by both housekeepers and guests. A hygiene intervention, which included providing hand hygiene products and facial tissues to the guests and disinfecting solutions with disposable wipes to the housekeeping staff, was successful in reducing the spread of viruses between the hotel guest rooms and conference center. The hygiene intervention resulted in significantly reduced transfer of the ϕx-174 between the contaminated hotel room and other hotel rooms, communal areas, and the conference center (p = 0.02).

Aggregation and interaction of cationic nanoparticles on bacterial surfaces.

Cationic monolayer-protected gold nanoparticles (AuNPs) with sizes of 6 or 2 nm interact with the cell membranes of Escherichia coli (Gram-) and Bacillus subtilis (Gram+), resulting in the formation of strikingly distinct AuNP surface aggregation patterns or lysis depending upon the size of the AuNPs. The aggregation phenomena were investigated by transmission electron microscopy and UV-vis spectroscopy. Upon proteolytic treatment of the bacteria, the distinct aggregation patterns disappeared.

Plasmonic field enhancement of the exciton-exciton annihilation process in a poly(p-phenyleneethynylene) fluorescent polymer by Ag nanocubes.

Using the Langmuir-Blodgett (LB) technique, a poly(paraphenyleneethynylene) (PPE) fluorescent conjugated polymer was assembled on either a quartz substrate (system I) or on the surface of silver nanocube (AgNC) monolayers (system II). The fluorescence intensity of the polymer was studied in system I as a function of the surface density of the polymer sample when deposited on quartz substrates and in system II on the surface coverage of the underlying AgNC monolayers. In system I, a continual increase in the fluorescence intensity is observed as the surface density of excited polymer is increased. In system II, the fluorescence intensity of the polymer first increased until a threshold surface coverage of AgNC was reached, after which it decreased rapidly with increasing surface coverage in the AgNC monolayer. The exciting light intensity dependence is studied before and after this threshold in system II. The results suggest that one-photon processes were responsible for the increased intensity before the threshold, and two-photon processes were responsible for the rapid decrease in the polymer fluorescence intensity after the threshold. These observations are explained by the increase of the surface plasmon enhancement of the exciting light intensity as the nanoparticle surface coverage is increased. In turn, this increases the polymer absorption rate, which results in a continuous increase in the exciton density and is evident by an increase in the fluorescence intensity. At the threshold, the increased exciton density leads to an increase in the rate of exciton-exciton collisions, which leads to exciton-exciton annihilations. When this phenomenon becomes faster than the rate of fluorescence emission, an intensity decrease is observed. By exploiting the surface plasmon enhancement of absorption processes, we have observed the first exciton-exciton annihilation using a low-intensity Hg-lamp continuous wave source.

Detection and differentiation of normal, cancerous, and metastatic cells using nanoparticle-polymer sensor arrays.

Rapid and effective differentiation between normal and cancer cells is an important challenge for the diagnosis and treatment of tumors. Here, we describe an array-based system for identification of normal and cancer cells based on a "chemical nose/tongue" approach that exploits subtle changes in the physicochemical nature of different cell surfaces. Their differential interactions with functionalized nanoparticles are transduced through displacement of a multivalent polymer fluorophore that is quenched when bound to the particle and fluorescent after release. Using this sensing strategy we can rapidly (minutes/seconds) and effectively distinguish (i) different cell types; (ii) normal, cancerous and metastatic human breast cells; and (iii) isogenic normal, cancerous and metastatic murine epithelial cell lines.

Nano-conjugate fluorescence probe for the discrimination of phosphate and pyrophosphate.

We describe a pyrophosphate (PPi) probe that is based on a fluorescent dicarboxylate-substituted poly(para-phenyleneethynylene) (PPE) and 10 nm cobalt-iron spinel nanoparticles (NPs) in aqueous media. The spinel NPs efficiently quench the fluorescence of the PPE at a concentration of 20-30 pmol. Addition of phosphate anions to the PPE-NP construct displaces the quenched PPE to give rise to a fluorescent response; we found that PPi and phosphate (Pi) have significantly different binding affinities for the self-assembled materials. We can discern >40 nM PPi in the presence of 0.1 mM Pi at pH 7, which suggests that these assemblies may be useful in bio-analytical applications. This displacement assay was used to effectively determine the ability of pyrophosphatase to hydrolyze PPi to Pi.

Fluorescence self-quenching of a mannosylated poly(p-phenyleneethynylene) induced by concanavalin A.

We report that static quenching of a mannosylated conjugated polymer (sugar-PPE) by Concanavalin A is positively dependent upon sugar-PPE concentration, that is, the recorded Stern-Volmer constants increase with increasing sugar-PPE concentration. Comparison with data obtained from isothermal titration calorimetry (ITC) display the increased sensitivity of the quenching method when compared to ITC. The proposed mechanism suggests the interaction of two or more chains of PPE with one Con A molecule leading to a quenched sugar-PPE-Con A construct.

Molecular recognition based on low-affinity polyvalent interactions: selective binding of a carboxylated polymer to fibronectin fibrils of live fibroblast cells.

To explore molecular recognition of biomolecules in the complex environment of the extracellular matrix, we utilized two fluorescent poly(p-phenyleneethynylene)s bearing either cationic alkylammonium or negatively charged carboyxlate side chains. While incubation of live NIH 3T3 fibroblast cells with the cationic polymer yielded perinuclear punctate staining reminiscent of endocytotic vesicles, the carboxylated polymer revealed a characteristic filamentous staining pattern. Histochemical and immunofluorescence studies demonstrated that the anionic PPE selectively binds to fibronectin fibrils of the extracellular matrix. An in vitro binding study revealed a dissociation constant of approximately 100 nM for the fibronectin-polymer complex. Both polymers showed bright two-photon excited emission as well as low toxicity, rendering them well-suited for live cell imaging studies. The studies demonstrate that selective molecular recognition of biomolecules in the complex environment of the extracellular matrix can be achieved by means of nonspecific low-affinity polyvalent interactions.

Terpyridine-based cruciform-Zn2+ complexes as anion-responsive fluorophores.

The synthesis of a terpyridine-appended, zinc-complexed cruciform, 3-Zn2+, and the anion-reactive modulation of its emissive properties in acetone-water mixtures are reported.