Simultaneous detection of cardiac biomarkers using multiplexed gold nanorod bioprobes

Gold based biosensors are gaining much interest in the field of biomarker detection. Conventional bioanalytic systems for biomarker detection are usually large, expensive, time consuming, and require highly skilled staff to operate. A gold nanorod (GNR) based test is being developed to eliminate some of these pitfalls and provide an easy, inexpensive, point of care biosensing platform. The ultimate goal of the test is to simultaneously detect cardiac troponin I (cTnI) and myoglobin (Mb), two biomarker proteins used in the detection of myocardial infarction. The mechanism of detection in this scheme is the exploitation of surface plasmon resonance (SPR) in gold nanorods, enhanced by the presence of magnetic nanoparticles. Gold nanospheres express nanoparticle SPR (nanoSPR), which creates characteristic peaks in optical density at incident wavelengths of ∼520 nm, while gold nanorods express two peaks representing their longitudinal and transverse axes. These characteristic peaks shift in wavelength as antibodies and antigens are attached to the surface. We have shown that the shift magnitude is directly proportional to the concentration of detected molecules. Magnetic nanoparticles (MNPs) serve a dual purpose; their magnetic property allows for the biomarkers to be specifically purified from physiological complex samples (i.e. blood plasma), and MNPs have been found to significantly enhance the sensitivity of nanoSPR biosensing using GNRs. By synthesizing gold nanorods of different aspect ratios, a multiplex detection scheme can be devised in which these nanorods are biofunctionalized, and the resulting wavelength shift detected using spectrophotometry.