Describe the principle of operation of the prostate-specific antigen (PSA) sensor of Zhang et al. [517], and rationalize how its claimed sensitivity of 4 fg/mL could be achieved. How many units or...

Describe the principle of operation of the prostate-specific antigen (PSA) sensor

of Zhang et al. [517], and rationalize how its claimed sensitivity of 4 fg/mL

could be achieved. How many units or molecules of PSA would be present in a