Detection of human neutrophil elastase (HNE) on wound dressings as marker of inflammation

Chronic wound fluids have elevated concentration of human neutrophil elastase (HNE) which can be used as inflammation/infection marker. Our goal is to develop functional materials for fast diagnosis of wound inflammation/infection by using HNE as a specific marker. For that, fluorogenic peptides with a HNE-specific cleavage sequence were incorporated into traditional textile dressings, to allow real-time detection of the wound status. Two different fluorogenic approaches were studied in terms of intensity of the signal generated upon HNE addition: a fluorophore 7-amino-4-trifluormethylcoumarin (AFC) conjugated to a HNE-specific peptide and two fluorophore/quencher pairs (FAM/Dabcyl and EDANS/Dabcyl) coupled to a similar peptide as a Förster resonance energy transfer (FRET) strategy. Also, two immobilization methods were tested: sonochemistry immobilization onto a cotton bandage and glutaraldehyde (GTA)-assisted chemical crosslinking onto a polyamide dressing. The immobilized fluorogenic AFC peptide showed an intense fluorescence emission in the presence of HNE. HNE also induced an enhanced fluorescent signal with the EDANS/Dabcyl FRET peptide which showed to be a more sensitive and effective strategy than the AFC peptide. However, its chemical immobilization onto the polyamide dressing greatly decreased its detection, mainly due to the more difficult access of the enzyme to the cleavage sequence of the immobilized peptide. After optimization of the in situ immobilization, it will be possible to use these fluorescence-functionalized dressings for an effective and specific monitoring of chronic wounds by simply using a portable ultraviolet (UV) light source. We envision that the development of this point-of-care medical device for wound control will have a great impact on patients life quality and reduction of costs on health care system.This study was funded by the European project InFact-Functional materials for fast diagnosis of wound infection (FP7-NMP-2013-SME-7-grant agreement no. 604278). The work done at Centre of Biological Engineering (CEB) was also supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit, COMPETE 2020 (POCI-01-0145-FEDER-006684) and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by European Regional Development Fund under the scope of Norte 2020-Programa Operacional Regional do Norte

Nonlinear deformation and localized failure of bacterial streamers in creeping flows

We investigate the failure of bacterial floc mediated streamers in a microfluidic device in a creeping flow regime using both experimental observations and analytical modeling. The quantification of streamer deformation and failure behavior is possible due to the use of 200 nm fluorescent polystyrene beads which firmly embed in the extracellular polymeric substance (EPS) and act as tracers. The streamers, which form soon after the commencement of flow begin to deviate from an apparently quiescent fully formed state in spite of steady background flow and limited mass accretion indicating significant mechanical nonlinearity. This nonlinear behavior shows distinct phases of deformation with mutually different characteristic times and comes to an end with a distinct localized failure of the streamer far from the walls. We investigate this deformation and failure behavior for two separate bacterial strains and develop a simplified but nonlinear analytical model describing the experimentally observed instability phenomena assuming a necking route to instability. Our model leads to a power law relation between the critical strain at failure and the fluid velocity scale exhibiting excellent qualitative and quantitative agreeing with the experimental rupture behavior

Electromagnetic shielding of polypyrrole-sawdust composites: polypyrrole globules and nanotubes

Economic and efficient materials for the shielding of electromagnetic interference are required by many applications. Electrically conducting composite materials based on wood sawdust modified by polypyrrole (PPy) with different morphology, globular and nanotubular, were prepared through in-situ polymerization of pyrrole with the use of iron (III) chloride as an oxidant. The effect of PPy morphology and content in composite with sawdust on the DC conductivity and shielding effectiveness (SE) were investigated. Composites of sawdust with globular PPy demonstrated higher DC conductivity as compared to those with PPy nanotubes as long as PPy content was less or equal to 18 vol.%. Above this concentration the opposite trend was observed. The SE of composites was evaluated theoretically in the radio-frequency range, and measured by waveguide method in the frequency range 5.85–8.2 GHz. The SE increased with increase in DC conductivity, and good agreement between the theoretically calculated SE and experimental results was achieved. The SE of the composites extended over 20 dB level above 18 vol.% PPy at the thickness of the order of 10 μm. Polypyrrole nanotubes perfomed better than globular PPy at high conducting polymer content. The composites are good candidates for the application as shielding materials in the microwave band. © 2017, Springer Science+Business Media B.V.Ministry of Education, Youth and Sports of the Czech Republic (NPU I) [LO1504]; Czech Science Foundation [16-02787S