Bionic E-Eye Based High-Throughput Immunocolorimetric Sensor System for Sensitive Detection BNP in Blood through Carbon-Gold Nanocomposites

Introduction Precise and sensitive detection of protein biomarkers is of vital importance in clinical diagnosis and biomedical research. To date, enzyme-linked immunosorbent assay (ELISA) remains the gold standard in detecting protein biomarkers due to the robust properties of simple operation, acceptable sensitivity, and automated high throughput [1, 2]. Despite desirable results from ELSA, pursuing high sensitivity and accuracy to meet diagnosis demands is still an ongoing endeavor. For that, nanomaterials behaving with favorable physical properties and biocompatibility may serve as a solution, especially the carbon nanosphere (CN) or gold nanoparticles (AuNPs) that feature strong stability, easy manufacture, low cost, and environment-friendly, and abundant active sites [3, 4]. Heart failure (HF) is one of the most threatening cardiovascular diseases. B-type natriuretic peptide (BNP), a vital cardiac biomarker, has been acknowledged as one of the principal biomarkers for HF [5]. Individuals at risk of HF demonstrate raised BNP in serum and real-time quantification of HF biomarkers, identifying those at highest risk of HF early, and ensuring they receive appropriate treatment can effectively prevent premature death [6]. Although current ELISA-methods for detecting BNP have been developed, there are urgent needs for providing more efficiently and reliably in vitro diagnostic (IVD) methods or point-of-care (POC) devices in BNP clinical measurement. Most of the previous studies for ELISA-based BNP detection required large instruments with high costs such as microplate readers, spectrophotometers. In this work, we adopted a self-developed portable bionic electronic eye (Bionic E-eye) system using a smartphone (iPhone 4S and iPad 3) integrated with simple accessories including a piece of electroluminescent, a wide-angle lens, and a dark hood instead of the commercial microplate reader to make the entire analysis process more intelligent and convenient. In addition, the CN-AuNPs nanocomposites (CGN) we prepared was used as a signal amplifier to develop a high-throughput immunocolorimetric method that sensitively identified BNP through the color change of antibody-antigen reactions using enzyme-substrate and horseradish peroxidase-antibody (pAb-HRP) linked CGN immunoprobe (CGNs@ pAb-HRP). The combination of Bionic E-eye and high-throughput immunocolorimetric system aimed to establish a general and reliable strategy for POC testing ( Figure. 1A ). Method Monoclon