The multidisciplinary and integrative research efforts in the field of nanotechnology have led to the development of a variety of nanoparticle-based carrier systems. Technologies that are enabled through the application of nanotechnology in biomedical research include nanodevices as biosensors, site-specific delivery of nanoparticles-based therapeutic agents, and technologies for cellular, tissue, and organ level imaging, to name a few.1

Development and application of point-of-care (POC) diagnostics hold great potential to improve healthcare in both developing and developed nations. Currently, the detection of nucleic acids of the infectious agent is the standard protocol for sensitive and specific diagnosis of infectious diseases. Although various technologies have been developed and practiced in centralized laboratories for nucleic acid detection (e.g., electrophoresis, spectrophotometry, and real-time polymerase chain reaction - qPCR), they cannot be easily carried out on-site for POC diagnostics such as in rural settings. Lateral flow assay (LFA) test strips (such as pregnancy test kits purchased over-the-counter in industrialized nations) have the most significant potential for POC and rural diagnostic. It is worth mentioning here that conventional immunoassays suffer from at least one of the following limitations: long processing time, poor user-friendliness, technical complexity, poor sensitivity, and specificity.2 Additionally, in the case of high-cost proteins (e.g., antibodies for detecting viruses including human papillomavirus-associated cervical cancer, hepatitis C virus, and the recently emerged SARS-COV-2), strategies need to are developed to minimize the amount of proteins required for the immobilization while maintaining high surface binding activity.3 A variety of substrates are used to immobilize biomolecules for diagnostic purposes. Fabrics and other fibrous meshes represent attractive platforms in advanced materials not only because of their relatively low-cost and lightweight but also because their porous structures give them a combination of mechanical flexibility and toughness, as well as high internal surface areas for surface modification. Cotton, an abundant fabric composed of natural cellulose fibers, offers an attractive combination of stability in a diverse range of solvents and (bio)degradability. Its potential as porous support of advanced functionalities is illustrated by the widely reported application of paper, also chiefly composed of cellulose, in low-cost biosensing. Polyester as a synthetic fabric is another widely available and low-cost material. Functionalization of both cotton and polyester holds significant appeal for a range of sensing applications.4

In this study, cotton fabric, nanoporous regenerated cellulose (NRC), and polyester (PE) substrates were functionalized with different combinations of polyphenol coating and silica nanoparticles to develop surfaces for enhancing the activity of the immobilized antibody. The addition of nanoparticles increased the surface area for functionalization, while polytannic acid (pTA) enabled effective surface immobilization of proteins. Moreover, co-immobilization with serum albumin as a “steric helper” protein was found to further enhance overall surface activity. The present results highlight the strategies for increasing the effective activities of immobilized antibodies (i.e., increased activity retention) without resorting to relatively costly site-specific or oriented protein immobilization approaches. Our results also highlight the overlapping considerations of surface chemistry, surface area, and the nature of protein-surface interactions in tuning the activities of immobilized proteins. The understandings developed in this work are anticipated to enable constructing low-cost yet sensitive biosensors by employing smaller amounts of antibodies during surface functionalization.