Biodegradable polymers and devices for detection of respiratory pathogens

Abstract

Novel sampling matrices were manufactured using 3D printing for the detection of respiratory pathogens, particularly the tubercle bacillus, in expired air. Polyvinyl alcohol (PVA) was printed using fused deposition modelling (FDM) to create a multilayer matrix to enhance the capture of bacteria. The performances of these matrices were compared with that of gelatine filters, which have been used for this same purpose to date. Mycobacterium bovis BCG, Mycobacterium abscessus, Mycobacterium Smegmatis, Haemophilus Influenzae and Escherichia coli were used in this study to contaminate the matrices. PVA matrices (60 mm diameter) and gelatine filters were contaminated with bacteria either by direct inoculation, or by aerosol exposure using an Omron A3 nebuliser to compare recovery rates for quantitative analyses. Also, bacteria exhaled by patients with Cystic Fibrosis (CF) were analysed using face masks loaded with PVA matrices. These were dissolved in water, the bacteria pelleted, and DNA extracted followed by quantitative Polymerase Chain Reaction (qPCR).The characteristic features of the PVA sampling matrix (SM) were studied by measuring the porosity, surface roughness, wettability and surface characteristics. The unidirectional tensile test was used to study the mechanical properties including strength, strain and modulus of elasticity of the 3D printed matrices produced using different printing parameters. These parameters included speed, infill density, layer thickness, cut angle and strain rate to allow selection of the most appropriate properties to facilitate the improved mechanical integrity of the matrices.The results showed that the 3D printed PVA samples can be used effectively to detect the airborne microorganisms. The hydrophilicity of the PVA matrix surface, the surface roughness (Ra >1 μm) and the overlap between PVA rasters resulted in enhanced the bacterial entrapment in the matrix. PVA is sufficiently robust to allow it to be handled and fabricated into fully printed face masks. The 100% infill density specimens printed at slow speed yielded a higher strength material, which is required for PVA SM.