A surgical blade includes a handle with a recess sized to receive the proximal end of a blade assembly. In particular, due to displacement with a specific competitor, binding molecules are selected which preferably bind to previously known epitopes. The dispenser also includes a novel stored energy source in the form of a constant force spring which controllably urges the medicinal fluid from the device reservoir. The elements of the switching mechanism and the latching mechanism are monolithically fabricated from a wafer. The threshold detection circuit may be configured to sense a feedback current and provide a DC signal to the base of the amplifier transistor for dynamically sourcing bias current to the amplifier.