Performances of rapid and connected salivary RT-LAMP diagnostic test for SARS-CoV-2 infection in ambulatory screening.

In the context of social events reopening and economic relaunch, sanitary surveillance of SARS-CoV-2 infection is still required. Here, we evaluated the diagnostic performances of a rapid, extraction-free and connected reverse-transcription loop-mediated isothermal amplification (RT-LAMP) assay on saliva. Nasopharyngeal (NP) swabs and saliva from 443 outpatients were collected simultaneously and tested by reverse-transcription quantitative PCR (RT-qPCR) as reference standard test. Seventy-one individuals (16.0%) were positive by NP and/or salivary RT-qPCR. Sensitivity and specificity of salivary RT-LAMP were 85.9% (95%CI 77.8-94.0%) and 99.5% (98.7-100%), respectively. Performances were similar for symptomatic and asymptomatic participants. Moreover, SARS-CoV-2 genetic variants were analyzed and no dominant mutation in RT-LAMP primer region was observed during the period of the study. We demonstrated that this RT-LAMP test on self-collected saliva is reliable for SARS-CoV-2 detection. This simple connected test with optional automatic results transfer to health authorities is unique and opens the way to secure professional and social events in actual context of economics restart.

Effect of surface roughness, porosity and roughened micro-pillar structures on the early formation of microbial anodes.

The early formation of electroactive biofilms was investigated with gold electrodes inoculated with Geobacter sulfurreducens. Biofilms were formed under an applied potential of 0.1 V/SCE, with a single batch of acetate 10 mM, on flat gold electrodes with different random surface roughness. Roughness with arithmetical mean height (Sa) ranging from 0.5 to 6.7 µm decreased the initial latency time, and increased the current density by a factor of 2.7 to 6.7 with respect to nano-rough electrodes (Sa = 4.5 nm). The current density increased linearly with Sa up to 14.0 A·m-2 for Sa of 6.7 µm. This linear relationship remained valid for porous gold. In this case, the biofilm rapidly formed a uniform layer over the pores, so porosity impacted the current only by modifying the roughness of the upper surface. The current density thus reached 14.8 ±â€¯1.1 A·m-2 with Sa of 7.6 µm (7 times higher than the nano-rough electrodes). Arrays of 500-µm-high micro-pillars were roughened following the same protocol. In this case, roughening resulted in a modest gain around 1.3-fold. A numerical model showed that the modest enhancement was due to ion transport not being sufficient to mitigate the local acidification of the structure bottom.

Impact of electrode micro- and nano-scale topography on the formation and performance of microbial electrodes.

From a fundamental standpoint, microbial electrochemistry is unravelling a thrilling link between life and materials. Technically, it may be the source of a large number of new processes such as microbial fuel cells for powering remote sensors, autonomous sensors, microbial electrolysers and equipment for effluent treatment. Microbial electron transfers are also involved in many natural processes such as biocorrosion. In these contexts, a huge number of studies have dealt with the impact of electrode materials, coatings and surface functionalizations but very few have focused on the effect of the surface topography, although it has often been pointed out as a key parameter impacting the performance of electroactive biofilms. The first part of the review gives an overview of the influence of electrode topography on abiotic electrochemical reactions. The second part recalls some basics of the effect of surface topography on bacterial adhesion and biofilm formation, in a broad domain reaching beyond the context of electroactivity. On these well-established bases, the effect of surface topography is reviewed and analysed in the field of electroactive biofilms. General trends are extracted and fundamental questions are pointed out, which should be addressed to boost future research endeavours. The objective is to provide basic guidelines useful to the widest possible range of research communities so that they can exploit surface topography as a powerful lever to improve, or to mitigate in the case of biocorrosion for instance, the performance of electrode/biofilm interfaces.

Effect of surface nano/micro-structuring on the early formation of microbial anodes with Geobacter sulfurreducens: Experimental and theoretical approaches.

Smooth and nano-rough flat gold electrodes were manufactured with controlled Ra of 0.8 and 4.5nm, respectively. Further nano-rough surfaces (Ra 4.5nm) were patterned with arrays of micro-pillars 500µm high. All these electrodes were implemented in pure cultures of Geobacter sulfurreducens, under a constant potential of 0.1V/SCE and with a single addition of acetate 10mM to check the early formation of microbial anodes. The flat smooth electrodes produced an average current density of 0.9A·m-2. The flat nano-rough electrodes reached 2.5A·m-2 on average, but with a large experimental deviation of ±2.0A·m-2. This large deviation was due to the erratic colonization of the surface but, when settled on the surface, the cells displayed current density that was directly correlated to the biofilm coverage ratio. The micro-pillars considerably improved the experimental reproducibility by offering the cells a quieter environment, facilitating biofilm development. Current densities of up to 8.5A·m-2 (per projected surface area) were thus reached, in spite of rate limitation due to the mass transport of the buffering species, as demonstrated by numerical modelling. Nano-roughness combined with micro-structuring increased current density by a factor close to 10 with respect to the smooth flat surface.