High-performance low-cost antibody microarrays using enzyme-mediated silver amplification.

Antibody microarrays can detect multiple proteins simultaneously, but the need for bulky and expensive fluorescence scanners limits their adaptation in clinical settings. Here we introduce a 15-plex enzyme-mediated silver enhanced sandwich immunoassay (SENSIA) on a microarray as an economic alternative to conventional fluorescence microarray assays. We compared several gold and silver amplification schemes, optimized HRP-mediated silver amplification, and evaluated the use of flatbed scanners for microarray quantification. Using the optimized assay condition, we established binding curves for 15 proteins using both SENSIA and conventional fluorescence microarray assays and compared their limits of detection (LODs) and dynamic ranges (DRs). We found that the LODs for all proteins are in the pg/mL range, with LODs for 12 proteins below 10 pg/mL. All but two proteins (ENDO and IL4) have similar LODs (less than 10-fold difference) and all but two proteins (IL1b and MCP1) are similar in DR (less than 1.5-log difference). Furthermore, we spiked six proteins in diluted serum and measured them by both silver enhancement and fluorescence detection and found a good agreement (R(2) > 0.9) between the two methods, suggesting that a complex matrix such as serum has a minimal effect on the measurement. By combining enzyme-mediated silver enhancement and consumer electronics for optical detection, SENSIA presents a new opportunity for low-cost high-sensitivity multiplex immunoassays for clinical applications.

Left ventricular shape assessment: a new simple diagnostic tool in stress echocardiography.

OBJECTIVE: Knowing that ventricular shape can be distorted by ischemia, we conducted this retrospective study to evaluate the value of left ventricular shape assessment as a diagnostic tool in stress echocardiography. METHODS: Forty studies (normal and abnormal dobutamine or exercise tests) were analyzed. All patients had normal systolic function at baseline. Endocardial borders were traced in diastole, in systole, at rest, and at peak stress. The endocardial border tracings (without corresponding video images) were presented to a blinded observer. Normal shape was defined as "rectangular or circular in parasternal long- and short-axis views, respectively, and triangular in the apical view." On the basis of those simple criteria for normal ventricular shape, the tracings were classified as normal or abnormal (ischemia) and results were compared with the wall-motion analysis of video images. RESULTS: Sensitivity, specificity, and positive and negative predictive values for shape abnormalities were 95%. Thirty-eight of the 40 studies were accurately classified without looking at the video tapes of the studies. CONCLUSIONS: Visual evaluation of ventricular shape can be very helpful in stress echocardiography. It can be easily accomplished even by someone with limited experience in this technique.