Rapid and sensitive detection of troponin I in human whole blood samples by using silver nanoparticle films and microwave heating.

BACKGROUND Cardiovascular diseases are among the leading causes of mortality in developed countries. It is widely recognized that troponin I (TnI) can be used for the assessment of a myocardial infarction. METHODS We investigated the use of the microwave-accelerated and metal-enhanced fluorescence (MA-MEF), a technique based on the combined use of low-power microwave heating, silver nanoparticle films (SNFs), and fluorescence spectroscopy for the detection of TnI from human whole blood samples. SNFs were deposited onto amine-modified glass microscope slides by use of Tollen's reaction scheme and characterized by optical absorption spectroscopy and scanning electron microscopy. The detection of TnI from buffer solutions and human whole blood samples on SNFs was carried out by using fluorescence-based immunoassays at room temperature (control immunoassay, 2 h total assay time) or microwave heating (MA-MEF-based immunoassay, 1 min total assay time). RESULTS We found that the lower limits of detection for TnI from buffer solutions in the control immunoassay and MA-MEF-based immunoassay were 0.1 μg/L and 0.005 μg/L, respectively. However, we were unable to detect TnI in whole blood samples in the control immunoassays owing to the coagulation of whole blood within 5 min of the incubation step. The use of the MA-MEF technique allowed detection of TnI from whole blood samples in 1 min with a lower detection limit of 0.05 μg/L. CONCLUSIONS The MA-MEF-based immunoassay is one of the fastest reported quantitative detection methodos for detection of TnI in human whole blood and has low detection limits similar to those obtained with commercially available immunoassays.