Surface plasmon resonance spectroscopy has long been demonstrated to enable detection of ~ng/ml of proteins. The detection limit varies with the size of the protein and the binding affinity of the antibody. In many cases signal enhancement with a secondary antibody, often labeled with a nanoparticle or another large protein, is needed to achieve ng/ml detection limits. However, lower detection limits and reliable quantitation in complex matrices, such as serum, have eluded SPR sensors.
We are developing a lab-on-a-chip sensor for determination of protein biomarkers for heart attacks and strokes. Incorporated in the sensor are strategies to overcome many of the problems that have traditionally limited application of SPR spectroscopy to real-world samples:
- microfluidic's to minimize needed sample volume
- electrokinetic separation and pre-concentration to effectively separate the analytes from background proteins
- biopolymer coatings to minimize surface fouling
- addressable SPR sensing pads, each with different molecular recognition motif, to account for thermal effects that change the SPR signal background
- rapid "just in time" functionalization of SPR sensing pads from lyophilized antibodies to ensure a fresh and active surface at the time of analysis.