Abstract
Lateral flow assays (LFAs) have become the most common biosensing platforms for point-of-care testing due to their compliance with the ASSURED (affordable, sensitive, specific, user-friendly, rapid/robust, equipment-free, and deliverable to end-users) guidelines stipulated by the World Health Organization. However, the limited analytical sensitivity and low quantitative capability of conventional LFAs, which use gold nanoparticles (AuNPs) for colorimetric labeling, have prevented high-performance testing. Here, we report the development of a highly sensitive chemiluminescence (CL)-based LFA involving AuNPs conjugated with aldehyde-activated peroxidase and antibody molecules—i.e., AuNP-(ald)HRP-Ab—as a new conjugation scheme for high-performance testing in LFAs. When paired with the CL-based signal readout modality, the AuNP-(ald)HRP-Ab conjugate resulted in 110-fold enhanced sensitivity over the colorimetric response of a typical AuNP-Ab conjugate. To evaluate the performance of the CL-based LFA, we tested it with human cardiac troponin I (cTnI; a standard cardiac biomarker used to diagnose myocardial infarction) in standard and clinical serum samples. Testing the standard samples revealed a detection limit of 5.6 pg·mL−1 and acceptably reliable precision (with a coefficient of variation of 2.3%–8.4%), according to clinical guidelines. Moreover, testing the clinical samples revealed a high correlation (r = 0.97) with standard biochemical analyzers, demonstrating the potential clinical utility of the CL-based LFA for high-performance cTnI testing.
Highlights
Cardiac troponin proteins control the contractile activity of cardiac muscles by regulating calcium-mediated interactions between actin and myosin [1]
After cardiac muscle undergoes myocardial infarction (MI), a primary subtype of cardiovascular disease (CVD), necrosis and myocardial damage occur due to the blockage of a coronary artery, and cardiac troponins are released into the bloodstream [1]
Despite the time-critical nature of MI and recent increases of CVD-related mortality in developing countries, most MI diagnoses based on high-end analyzers operating within clinical guidelines that are available at clinical laboratories require multiple decision processes and a specialized operator, which prevents rapid and early diagnosis and leads to diagnostic inequality [5,6]
Summary
Cardiac troponin proteins control the contractile activity of cardiac muscles by regulating calcium-mediated interactions between actin and myosin [1]. Among the cardiac troponins (I, T, and C) and other biomarker proteins such as creatine kinase-myocardial band and myoglobin, cardiac troponin I (cTnI) has been considered a gold-standard biomarker for diagnosing MI because of its high clinical sensitivity and cardiac specificity [2]. With the development of cTnI assays, the specifications of high-sensitivity standard analyzers for cTnI testing have achieved clinically acceptable levels; i.e., a coefficient of Sensors 2020, 20, 2593; doi:10.3390/s20092593 www.mdpi.com/journal/sensors. Despite the time-critical nature of MI and recent increases of CVD-related mortality in developing countries, most MI diagnoses based on high-end analyzers operating within clinical guidelines that are available at clinical laboratories require multiple decision processes and a specialized operator, which prevents rapid and early diagnosis and leads to diagnostic inequality [5,6]. Developing a simple, rapid, reliable, and highly sensitive point-of-care test (POCT) for cTnI is urgently needed to alleviate the high rate of mortality and disability caused by MI
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