The present invention provides an immobilization medium which can immobilize bioreagents to support materials and which dries to a water resistant layer or film. The immobilization medium comprises (i) a liquid or fluid binding reagent and (ii) complexes of a bioreagent immobilized to a solid phase which are evenly dispersed within the binding reagent. The suspension can further include supplemental ingredients evenly dispersed throughout the medium which can provide the medium with electrochemical properties, enhance the stability of the immobilized bioreagent and/or improve the medium's capability of drying to a substantially water resistant or insoluble layer. The immobilization medium provided by the instant invention is in the form of a homogeneous liquid suspension.