Binding enhancements of antibody functionalized natural and synthetic fibers.

Development of low cost biosensing using convenient and environmentally benign materials is important for wide adoption and ultimately improved healthcare and sustainable development. Immobilized antibodies are often incorporated as an essential biorecognition element in point-of-care biosensors but these proteins are costly. We present a strategy of combining convenient and low-cost surface functionalization approaches for increasing the overall binding activity of antibody functionalized natural and synthetic fibers. We demonstrate a simple one-step in situ silica NP growth protocol for increasing the surface area available for functionalization on cotton and polyester fabrics as well as on nanoporous cellulose substrates. Comparing this effect with the widely adopted and low cost plant-based polyphenol coating to enhance antibody immobilization, we find that both approaches can similarly increase overall surface activity, and we illustrate conditions under which the two approaches can produce an additive effect. Furthermore, we introduce co-immobilization of antibodies with a sacrificial "steric helper" protein for further enhancing surface activities. In combination, several hundred percent higher activities compared to physical adsorption can be achieved while maintaining a low amount of antibodies used, thus paving a practical path towards low cost biosensing.

Highly Active Protein Surfaces Enabled by Plant-Based Polyphenol Coatings.

Proteins represent complex biomolecules capable of wide-ranging but also highly specific functionalities. Their immobilization on material supports can enable broad applications from sensing and industrial biocatalysis to biomedical interfaces and materials. We demonstrate the advantages of using aqueous-processed cross-linked polyphenol coatings for immobilizing proteins, including IgG, avidin, and various single and multidomain enzymes on diverse materials, to enable active biofunctional structures (e.g., ca. 2.2, 1.7, 1.1, and 4.8 mg·m-2 active phosphatase on nanoporous cellulose and alumina, steel mesh, and polyester fabric, respectively). Enzyme assays, X-ray photoelectron spectroscopy, silver staining, supplemented with contact angle, solid-state 13C NMR, HPLC, and ESI-MS measurements were used to characterize the polyphenols, coatings, and protein layers. We show that the functionalization process may be advantageously optimized directly for protein activity rather than the traditional focus on the thickness of the coating layer. Higher activities (by more than an order of magnitude in some cases) and wider process pH and material compatibility are demonstrated with polyphenol coatings than other approaches such as polydopamine. Coatings formed from different plant polyphenol extracts, even at lowered purity (and cost), were also found to be highly functional. Chemically, our results indicate that polyphenol coatings differ from polydopamine mainly because of the elimination of amine groups, and that polyphenol layers with intermediate levels of reactivity may better lead to high immobilized protein activity. Overall, an improved understanding of simple-to-use polyphenol coatings has been obtained, which enabled a significant development in active protein surfaces that may be applied across diverse materials and nanostructured supports.