Immunosensors made of polymer-infused porous paper for the non-invasive detection of airways cytokines trapped by porous face masks

Abstract

The diverse physicochemical properties of polymers make them perfect candidates for developing biosensor elements when combined with porous substrates. For example, microfluidic channels, valves, reservoirs and biorecognition elements have been proposed that rely on filling the cavities of porous cellulose with different polymers. Yet, highly concentrated polymers are often too viscous to dispense them with precision using conventional printing methods. This increases the manufacturing variability, which degrades the performance of the biosensors. Here this issue is solved with a new method for infusing porous materials (filter paper) with concentrated polymers (PSS) that circumvents the dropwise addition of highly viscous reagents. The resulting films contain homogenously distributed polymers, which reduces the intra- and inter-batch variabilities of biosensors based on dispensing nanoparticles from the reservoirs. The proposed method was utilized to develop immunosensors for detecting the cytokines IL-6 and IL-5 in aerosols, which were trapped by the polypropylene layer of a surgical face mask (limit of detection 10−2 pg·mL−1). Using this approach, we were able to detect elevated levels of airways cytokines when exacerbated COPD patients and eosinophilic asthma patients wore the face mask for 30 min. The results shown here pave the way for upscaling the manufacturing of paper-based nanoparticle biosensors, which is a crucial step towards their future commercialization.