Determination of prostate-specific antigen in serum samples using gold nanoparticle based amplification and lab-on-a-chip based amperometric detection

We describe an electrode array and microfluidics based integrated biochip for the quantitation of the tumor marker prostate specific antigen (PSA). The surface of the chip was functionalized with a self-assembled monolayer of mercaptoundecanoic acid prior to the immobilization of the antibody against PSA. A flow of buffer or spiked human serum (75 %) and, subsequently, the detection antibody and gold nanoparticles (Au-NPs) modified with horseradish peroxidase were passed over the antibody-coated electrodes. This was followed by the injection of the substrate tetramethylbenzidine and simultaneous amperometry during the flow. This resulted in a real-time amperometric reading. The method has detection limits (LODs) of 0.2 nga (TM) L-1 in buffer and of 1 nga (TM) L-1 in 75 % human serum. The linear part of the calibration plot has an r(2) of 0.97. These LODs are well below the clinical threshold level of 4 nga (TM) L-1. This assay is rapid (similar to 15 min) which compares favorably with respect to conventional chronoamperometric analysis and to ELISA tests which require similar to 45 min. This new platform has a potential as an automatted point-of-care device for clinical use because it is likely to be applicable to numerous other clinical analytes for which appropriate antibodies are available.