Plasma myoglobin in the early diagnosis of acute myocardial infarction

Enhanced adhesion of functional layers by controlled electrografting of ethylenediamine on ITO for electrochemical immunoassay in microfluidic channel

Two-electrode (2E) system of the interdigitated electrode array (IDA), which operates neither reference nor counter electrodes, has great potential to miniaturize multiplex immunoassay in a microfluidic chip for point-of-care testing. However, it is necessary to firmly immobilize the mediator layer on IDA made of indium tin oxide (ITO) which is chemically inert. It is important because the mediator determines the electrochemical potential in the 2E system, but the layer is easy to be detached during the washing processes of immunoassay. Here, we controlled the concentration of ethylenediamine (EDA) to generate a permeable and robust film to adhere to mediators on the ITO IDA chip. Electrooxidation of EDA yielded thin oligomeric ethyleneimine (OEI) film and it provided amine groups for immobilizing the mediator, poly(toluidine blue) (pTB), via common conjugation reaction. Despite repeated flows in the microchannel, which are essential for sensitive immunoassay, the pTB/OEI layer was hardly washed and still remained on the ITO IDA. Myoglobin was measured down to ∼ pg/mL level. Therefore, the ITO IDA modified with the OEI film in the 2E system constituted a stable platform that withstands washing steps for sensitive electrochemical detection in the miniaturized immunoassay.

Isobaric tags for relative and absolute quantitation‑based proteomics reveals potential novel biomarkers for the early diagnosis of acute myocardial infarction within 3 h

Acute myocardial infarction (AMI) is one of the most common and life-threatening cardiovascular diseases. However, the ability to diagnose AMI within 3 h is currently lacking. The present study aimed to identify the differentially expressed proteins of AMI within 3 h and to investigate novel biomarkers using isobaric tags for relative and absolute quantitation (ITRAQ) technology. A total of 30 beagle dogs were used for establishing the MI models successfully by injecting thrombin powder and a polyethylene microsphere suspension. Serum samples were collected prior to (0 h) and following MI (1, 2 and 3 h). ITRAQ-coupled liquid chromatography-mass spectrometry (LC-MS) technology was used to identify the differentially expressed proteins. The bioinformatics analysis selected several key proteins in the initiation of MI. Further analysis was performed using STRING software. Finally, western blot analysis was used to evaluate the results obtained from ITRAQ. In total, 28 proteins were upregulated and 23 were downregulated in the 1 h/0 h group, 28 proteins were upregulated and 26 were downregulated in the 2 h/0 h group, and 24 proteins were upregulated and 19 were downregulated in the 3 h/0 h group. The Gene Ontology (GO) annotation and functional enrichment analysis identified 19 key proteins. Protein-protein interactions (PPIs) were investigated using the STRING database. GO enrichment analysis revealed that a number of key proteins, including ATP synthase F1 subunit β (ATP5B), cytochrome c oxidase subunit 2 and cytochrome c, were components of the electron transport chain and were involved in energy metabolism. The western blot analysis demonstrated that the expression of ATP5B decreased significantly at all three time points (P<0.01), which was consistent with the ITRAQ results, whereas the expression of fibrinogen γ chain increased at 2 and 3 h (P<0.01) and the expression of integrator complex subunit 4 increased at all three time points (P<0.01), which differed from the ITRAQ results. According to the proteomics of the beagle dog MI model, ATP5B may serve as the potential biomarkers of AMI. Mitochondrial dysfunction and disruption of the electron transport chain may be critical indicators of early MI within 3 h. These finding may provide a novel direction for the diagnosis of AMI.

Cardiac troponins I and T: molecular markers for early diagnosis, prognosis, and accurate triaging of patients with acute myocardial infarction

Acute myocardial infarction (AMI) is the leading cause of death worldwide, with early diagnosis still being difficult. Promising new cardiac biomarkers such as troponins and creatine kinase (CK) isoforms are being studied and integrated into clinical practice for early diagnosis of AMI. The cardiac-specific troponins I and T (cTnI and cTnT) have good sensitivity and specificity as indicators of myocardial necrosis and are superior to CK and its MB isoenzyme (CK-MB) in this regard. Besides being potential biologic markers, cardiac troponins also provide significant prognostic information. The introduction of novel high-sensitivity troponin assays has enabled more sensitive and timely diagnosis or exclusion of acute coronary syndromes. This review summarizes the available information on the potential of troponins and other cardiac markers in early diagnosis and prognosis of AMI, and provides perspectives on future diagnostic approaches to AMI.

Myoglobin immunoassay based on metal particle-enhanced fluorescence

Enhanced fluorescence on silver island films (SIFs) is utilized to develop a sandwich-format immunoassay for the cardiac marker myoglobin (Myo). Myoglobin was first captured on surfaces coated with anti-Myo antibodies; the surface was then incubated with fluorescently labeled anti-Myo antibodies. The system was examined on glass surfaces and on SIFs. We observed the enhancement of the signal from SIFs in the range of 10-15-fold if compared to the signal from the glass substrate not modified with a SIF. A kinetic immunoassay for Myo on SIF-modified surface results in a decreased background signal. The initial results show that it is possible to detect Myoglobin concentrations below 50 ng/mL, which is lower than clinical cut-off for Myoglobin in healthy patients. We suggest the use of SIF-modified substrates for increasing the sensitivity of surface assays with fluorescence detection.

Metal-enhanced fluorescent biomarkers for cardiac risk assessment

In this presentation we describe a novel methodology for ultra-sensitive fluorescence immunoassays based on a new class of fluorescent biomarkers, which are strongly enhanced by nano-size metallic particles. Specifically, we discuss development of the immunoassay on the surfaces coated with metallic particles for high sensitivity detection of cardiac markers. This technology will allow detection of the biomarkers in serum and blood without separation and amplification steps. We present an experimental platform that uses front-face excitation in total internal reflection mode for efficient rejection of background fluorescence.