For the construction of highâperformance biosensor, it is important to interface bioreceptors with the sensor surface densely and in the optimal orientation. Herein, a simple surface modification method that can optimally immobilize antibodies onto various kinds of surfaces is reported. For the surface modification, a mixture of polydopamine (PDA) and protein G was employed. PDA is a representative musselâinspired polymer, and protein G is an immunoglobulinâbinding protein that enables an antibody to have an optimal orientation. The surface characteristics of PDA/Protein G mixtureâcoated substrates are analyzed and the PDA/protein G ratio is optimized to maximize the antibody binding efficiency. Moreover, the antibodyâimmobilized substrates are applied to the detection of influenza viruses with the naked eye, providing a detection limit of 2.9 Ă 103 pfu mLâ1. Importantly, the several substrates (glass, SiO2, Si, Al2O3, polyethylene terephthalate, polyethylene, polypropylene, and paper) can be modified by simple incubation with the mixture of PDA/protein G, and then the antiâinfluenza A H1N1 antibodies can be immobilized on the substrates successfully. Regardless of the substrate, the influenza viruses are detectable after the sandwich immunoreaction and silver enhancement procedure. It is anticipated that the developed PDA/protein G coating method will extend the range of applicable materials for biosensing.