Abstract
A reliable lateral flow immunoassay (LFIA) based on a facile one-step synthesis of single microspheres in combining with immunochromatography technique was developed to establish a new point-of-care test (POCT) for the rapid and early detection of cardiac troponin I (cTnI), a kind of cardiac specific biomarker for acute myocardial infarction (AMI). The double layered microspheres with clear core-shell structures were produced using soap-free emulsion polymerization method with inexpensive compounds (styrene and acrylic acid). The synthetic process was simple, rapid and easy to control due to one-step synthesis without any complicated procedures. The microspheres are nanostructure with high surface area, which have numerous carboxyl groups on the out layer, resulting in high-efficiency coupling between the carrier and antibody via amide bond. Meanwhile, the red fluorescent dye, Nile-red (NR), was wrapped inside the microspheres to improve its stability, as well to reduce the background noise, because of its higher emission wavelength than interference from real plasma samples. The core-shell structures provided different functional areas to separate antibody and dyes, so the immunoassay has highly sensitive, wide working curves in the range of 0–40 ng/mL, low limits of detection (LOD) at 0.016 ng/mL, and limits of quantification (LOQ) at 0.087 ng/mL with coefficient of variations (CV) of 10%. This strategy suggested an outstanding platform for LFIA, with good reproducibility and stability to straightforwardly analyze the plasma samples without washing steps, thereby reducing the operating procedures for non-professionals and promoting detection efficiency. The whole detection process can be completed in less than 15 min. This novel immunoassay offers a reliable and favorable analytical result by detecting the real samples, indicating that it holds great potential as a new alternative for biomolecule detection in complex samples, for the early detection of cardiac specific biomarkers.
Highlights
Cardiac troponin I is a cardiac specific biomarker that is released during myocardial necrosis; it reaches a peak value in blood after about 11 h [1]
For the inter-assay precision, each concentration of Cardiac troponin I (cTnI) was measured by nine test strips, which were randomly chosen from three different batches
The results showed that the relative deviations (RD) were all in the range of ±10%, suggesting that the effects of interfering factors were not significant, and the specificity of this immunoassay was acceptable as its highly specific toward cTnI
Summary
Cardiac troponin I (cTnI) is a cardiac specific biomarker that is released during myocardial necrosis; it reaches a peak value in blood after about 11 h [1]. In order to conjugate the antibodies for immunoassay, some functional groups, such as carboxyl and amidogen, still need to be modified on those microsphere surface These methods are effective in improving the detection sensitivity and product stability, many problems are still encountered, such as complicated synthetic steps, low yield, and high cost, which limit their application in clinical detection. A facile one-step synthesis was used to prepare a single microsphere with clear core-shell structures to establish a new POCT method for the rapid and early detection of cTnI. This detection method, based on double layered fluorescent microsphere in combination with immunochromatography technique, challenging than previous sinceapplication.
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