Direct and label-free detection of the human growth hormone in urine by an ultrasensitive bimodal waveguide biosensor

A label-free interferometric transducer showing a theoretical detection limit for homogeneous sensing of 5 x 10(-8) RIU, being equivalent to a protein mass coverage resolution of 2.8 fg mm(-2), is used to develop a high sensitive biosensor for protein detection. The extreme sensitivity of this transducer combined with a selective bioreceptor layer enables the direct evaluation of the human growth hormone (hGH) in undiluted urine matrix in the 10 pg mL(-1) range.