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Healthcare workers (HCW) play a vital role in the SARS-CoV-2 pandemic control. The aim of this study was to assess the prevalence of SARS-CoV-2 antibodies and the risk of COVID-19 infections in a cohort of HCW from four different risk groups (from intensive care unit to administration) of a hospital of a primary care level in rural Germany. The outcomes were monthly measures of antibody seroprevalence over a period of 6 months. Overall, a seroprevalence of 13.41% was determined, with significantly higher prevalence rates among HCW working in areas with more frequent contact to confirmed or suspected cases (30.30%, p = 0.003). The group specific differences in the risk of infection from COVID-19 were detected, as HCW groups with frequent exposure seemed to have an increased risk (RR = 3.18, p = 0.02; CI95 1.09–9.24). The findings contribute to the epidemiological understanding of the virus spread in an unvaccinated population group, which is highly relevant for the pandemic management.
Background: The 3D printing is relevant as a manufacturing technology of functional models for forensic, pharmaceutical and bioanalytical applications such as drug delivery systems, sample preparation and point-of-care tests.
Objective: Melting behavior and autofluorescence of materials are decisive for optimal printing and applicability of the product which are influenced by varying unknown additives.
Methods: We have produced devices for bioanalytical applications from commercially available thermoplastic polymers using a melt-layer process. We characterized them by differential scanning calorimetry, fluorescence spectroscopy and functional assays (DNA capture assay, model for cell adhesion, bacterial adhesion and biofilm formation test).
Results: From 14 tested colored, transparent and black materials we found only deep black acrylonitrile-butadiene-styrene (ABS) and some black polylactic acid (PLA) useable for fluorescence-based assays, with low autofluorescence only in the short-wave range of 300-400 nm. PLA was suitable for standard bioanalytical purposes due to a glass transition temperature of approximately 60°C, resistance to common laboratory chemicals and easy print processing. For temperature-critical methods, such as hybridization reactions up to 90°C, ABS was better suited.
Conclusions: Autofluorescence was not a disadvantage per se but can also be used as a reference signal in assays. The rapid development of individual protocols for sample processing and analysis required the availability of a material with consistent quality over time. For fluorescence-based assays, the use of commercial standard materials did not seem to meet this requirement.