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Cardiovascular disease (CVD), the leading cause of death worldwide, has been viewed as one of the major problems for wealthy and industrialized nations for decades, and the need for rapid detection and timely diagnosis has the utmost importance. Cardiac troponin I (cTnI) is a promising biomarker for early diagnosis of acute myocardial infarction (AMI). Hence, the development of immunoassay based biosensor for cTnI is necessary. Over the past decades, there have been extensive researches regarding cTnI detection, including colorimetric, fluorescence, paramagnetic, electrochemical, and surface plasmon resonance. However, conventional laboratory methods are time-consuming and require expensive and bulky equipment. In light of this, the need for point of care testing becomes more crucial. Here, we use a programmable microcontroller unit (MCU) to operate the device. A digital-to-analog converter (DAC) is used to deliver a modulating signal to LEDs, and then the modulated light excites the samples in the microfluidic reaction wells. The signals from the sample and control group are obtained by two photodetectors individually. They will be amplified and demodulated through the lock-in amplifier and digitized by analog-to-digital converters (ADC) to the MCU. And the collected data will be presented on the device and uploaded synchronically to the smartphone via Bluetooth. The whole processing time is less than 5 minutes. Next, we use the microfluidic platform to simplify complicated laboratory procedures. In our study, we focus on using cTnI to detect the samples in the human serum or blood. In order to solve low efficacy caused by the non-specific binding, we used Zwitterionic carboxybetaine disulfide (CB) as a self-assembled monolayer in the experimental design. The use of self-assembled monolayer can not only decrease non-specific binding problem but also shorten the analysis time.
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