Since December 2019, Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has caused millions of deaths and seriously threatened the safety of human life; indeed, this situation is worsening and many people are infected with the new coronavirus every day. Therefore, it is very important to understand patients’ degree of infection and infection history through antibody testing. Such information is useful also for the government and hospitals to formulate reasonable prevention policies and treatment plans. In this paper, we develop a lateral flow immunoassay (LFIA) method based on superparamagnetic nanoparticles (SMNPs) and a giant magnetoresistance (GMR) sensing system for the simultaneously quantitative detection of anti-SARS-CoV-2 immunoglobulin M (IgM) and G (IgG). A simple and time-effective co-precipitation method was utilized to prepare the SMNPs, which have good dispersibility and magnetic property, with an average diameter of 68 nm. The Internet of Medical Things-supported GMR could transmit medical data to a smartphone through the Bluetooth protocol, making patient information available for medical staff. The proposed GMR system, based on SMNP-supported LFIA, has an outstanding advantage in cost-effectiveness and time-efficiency, and is easy to operate. We believe that the suggested GMR based LFIA system will be very useful for medical staff to analyze and to preserve as a record of infection in COVID-19 patients.
In recent years, point-of-care testing has played an important role in immunoassay, biochemical analysis, and molecular diagnosis, especially in low-resource settings. Among various point-of-care-testing platforms, microfluidic chips have many outstanding advantages. Microfluidic chip applies the technology of miniaturizing conventional laboratory which enables the whole biochemical process including reagent loading, reaction, separation, and detection on the microchip. As a result, microfluidic platform has become a hotspot of research in the fields of food safety, health care, and environmental monitoring in the past few decades. Here, the state-of-the-art application of microfluidics in immunoassay in the past decade will be reviewed. According to different driving forces of fluid, microfluidic platform is divided into two parts: passive manipulation and active manipulation. In passive manipulation, we focus on the capillary-driven microfluidics, while in active manipulation, we introduce pressure microfluidics, centrifugal microfluidics, electric microfluidics, optofluidics, magnetic microfluidics, and digital microfluidics. Additionally, within the introduction of each platform, innovation of the methods used and their corresponding performance improvement will be discussed. Ultimately, the shortcomings of different platforms and approaches for improvement will be proposed.
As the medical community puts forward higher requirements for the speed and convenience of disease diagnosis, point-of-care testing has become a hot research topic to overcome various kinds of healthcare problems. Blood test is considered to be highly sensitive and accurate in clinical diagnosis. However, conventional plasma separation system tends to be bulky and needs professional operations. Moreover, imprecise separation may cause residual biochemical substances such as blood cells to affect the detection results. In this work, to solve these problems, we designed a portable centrifugal microfluidic platform for automatic, rapid and ultraprecise blood separation. The disc consists of multichambers and multi-microchannels where a plasma reservoir and a cell reservoir are connected to each other and collinear with the center of the circle. This structure overcomes the weakness of low separation efficiency (when hematocrit increases) under the traditional blood separation structure (bifurcation structure). As a result, the proposed system achieved 99.9% plasma purity, 99.9% separation efficiency (with a blood hematocrit of 48%) and 32.5% plasma recovery rate in the 50s, which provides a strong guarantee for rapid blood diagnosis and analysis, especially in areas where medical resources are limited.
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