Comparison of bacterial filtration efficiency vs. particle filtration efficiency to assess the performance of non-medical face masks.

As a result of the current COVID-19 pandemic, the use of facemasks has become commonplace. The performance of medical facemasks is assessed using Bacterial Filtration Efficiency (BFE) tests. However, as BFE tests, require specific expertise and equipment and are time-consuming, the performance of non-medical facemasks is assessed with non-biological Particle Filtration Efficiency (PFE) tests which are comparatively easier to implement. It is necessary to better understand the possible correlations between BFE and PFE to be able to compare the performances of the different types of masks (medical vs. non-medical). In this study BFE results obtained in accordance with the standard EN 14683 are compared to the results of PFE from a reference test protocol defined by AFNOR SPEC S76-001 with the aim to determine if BFE could be predicted from PFE. Our results showed a correlation between PFE and BFE. It was also observed that PFE values were higher than BFE and this was attributed to the difference in particle size distribution considered for efficiency calculation. In order to properly compare these test protocols for a better deduction, it would be interesting to compare the filtration efficiency for a similar granulometric range.

Reuse of medical face masks in domestic and community settings without sacrificing safety: Ecological and economical lessons from the Covid-19 pandemic.

The need for personal protective equipment increased exponentially in response to the Covid-19 pandemic. To cope with the mask shortage during springtime 2020, a French consortium was created to find ways to reuse medical and respiratory masks in healthcare departments. The consortium addressed the complex context of the balance between cleaning medical masks in a way that maintains their safety and functionality for reuse, with the environmental advantage to manage medical disposable waste despite the current mask designation as single-use by the regulatory frameworks. We report a Workflow that provides a quantitative basis to determine the safety and efficacy of a medical mask that is decontaminated for reuse. The type IIR polypropylene medical masks can be washed up to 10 times, washed 5 times and autoclaved 5 times, or washed then sterilized with radiations or ethylene oxide, without any degradation of their filtration or breathability properties. There is loss of the anti-projection properties. The Workflow rendered the medical masks to comply to the AFNOR S76-001 standard as "type 1 non-sanitory usage masks". This qualification gives a legal status to the Workflow-treated masks and allows recommendation for the reuse of washed medical masks by the general population, with the significant public health advantage of providing better protection than cloth-tissue masks. Additionally, such a legal status provides a basis to perform a clinical trial to test the masks in real conditions, with full compliance with EN 14683 norm, for collective reuse. The rational reuse of medical mask and their end-of-life management is critical, particularly in pandemic periods when decisive turns can be taken. The reuse of masks in the general population, in industries, or in hospitals (but not for surgery) has significant advantages for the management of waste without degrading the safety of individuals wearing reused masks.

New insights into the standard method of assessing bacterial filtration efficiency of medical face masks.

Based on the current knowledge of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) transmission, wearing a mask has been recommended during the COVID-19 pandemic. Bacterial filtration efficiency (BFE) measurements enable designing and regulating medical masks to prevent bioaerosol dissemination; however, despite the simplicity of these measurements, several scientific questions remain unanswered regarding BFE tests. Here, we investigated (1) the impact of substituting 100-mm Petri dishes with 90-mm disposable Petri dishes, (2) the impact of colony-counting methods on the bioaerosol aerodynamic size, and (3) the impact of colony-counting methods on the total viable particle counts. We demonstrated that disposable 90-mm Petri dishes can be used to replace the 100-mm dishes. We also showed that an automatic high-resolution colony counter can be used to directly count viable particles on collection substrates and to measure the bioaerosol size parameters. Our results enable possible modernization of the outdated testing methods recommended in the US and European standards for BFE measurements. Specifically, use of a modernized colony counter should be clearly regulated and permitted to avoid the counting of positive holes. The median aerodynamic diameter appears to be the most relevant parameter for characterizing bioaerosol size.

Macrotopographic closure promotes tissue growth and osteogenesis in vitro.

While the impact of substrate topographies at nano- and microscale on bone cell behavior has been particularly well documented, very few studies have analyzed the role of substrate closure at a tissular level. Moreover, these have focused on matrix deposition rather than on osteoblastic differentiation. In the present work, mouse calvaria cells were grown for 15days on hydroxyapatite (HA) ceramics textured with three different macrogrooves shapes (**100µm): 1 sine and 2 triangle waveforms. We found that macrotopography favors cell attachment, and that bone-like tissue growth and organization are promoted by a tight "closure angle" of the substrate geometry. Interestingly, while Flat HA controls showed little marker expression at the end of the culture, cells grown on macrogrooves, and in particular the most closed (triangle waveform with a 517µm spatial period) showed a fast time-course of osteoblast differentiation, reaching high levels of gene and protein expression of osteocalcin and sclerostin, a marker of osteocytes. STATEMENT OF SIGNIFICANCE: Many in vitro studies have been conducted on topography at nano and microscale, fewer have focused on the influence of macrotopography on osteoblasts. Ceramics with a controlled architecture were obtained throught a 3D printing process and used to assess osteoblast behavior. Biocompatible, they allowed the long-terme survival of osteoblast cells and the laying of an important bone matrix. V-shaped grooves were found to accelerates osteoblast differentiation and promote bone-like tissue deposition and maturation (osteocyte formation), proportionately to angle closure. Such macrostructures are attractive for the design of innovative implants for bone tissue engineering and in vitro models of osteogenesis.