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 × 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.