Biomicrofluidics最新文献

Droplet digital PCR (ddPCR) is a technique in which PCR reaction is divided into thousands of nanoliter-sized droplets and has proven to be a great tool in virus diagnostics. Compared to the gold standard system quantitative real-time PCR (RT-qPCR), ddPCR functions particularly well when dealing with samples with low template counts, such as viral concentration. This feature makes the technique suitable for early detection of the virus. In this study, a novel portable PDMS ddPCR chip is introduced. The chip functions without external pumps using manual pressurization with a multichannel pipet. The created droplets are monodispersed and form a monolayer on the chip's collection chamber, from where they can be effortlessly imaged. Droplets were analyzed and counted using artificial intelligence. The use of the manually pressurized chip was demonstrated for a SARS-CoV-2 assay, which takes advantage of isothermal strand invasion-based amplification (SIBA) technology, allowing quick and accurate, even point-of-care analysis of the sample. The results demonstrate that SIBA assays can be divided into nanoliter-sized droplets and used as quantitative assays, giving an approximation of the samples' viral count.

The robust identification and quantification of various biomarkers is of utmost significance in clinical diagnostics and precision medicine. Fluorescent immunoassays are widely used and considered as a gold standard for biomarker detection due to their high specificity and accuracy. However, current commercial immunoassay tests suffer from limited detection sensitivity and complicated, labor-intensive operation procedures, making them impractical for point-of-care diagnosis, particularly in resource-limited regions. Recently, microfluidic immunoassay devices integrated with plasmonic nanostructures have emerged as a powerful tool for sensitive detection of biomarkers, addressing specific issues, such as integration schemes, easy operation, multiplexed detection, and sensitivity enhancement. In this paper, we provide a discussion on the recent advances in the plasmonic nanostructures integrated with microfluidic devices for fluorescent immunoassays. We shed light on the nanofabrication strategies and various fluidic designs for rapid, sensitive, and highly efficient sensing of antigens. Finally, we share our perspectives on the potential directions of these integrated devices for practical applications.

Point-of-care (POC) diagnostic devices have been developing rapidly in recent years, but they are mainly using saliva instead of blood as a test sample. A highly efficient self-separation during the self-driven flow without power systems is desired for expanding the point-of-care diagnostic devices. Microfiltration stands out as a promising technique for blood plasma separation but faces limitations due to blood cell clogging, resulting in reduced separation speed and efficiency. These limitations are mainly caused by the high viscosity and hematocrit in the blood flow. A small increment in the hematocrit of the blood significantly increases the pressure needed for the blood plasma separation in the micro-filters and decreases the separation speed and efficiency. Addressing this challenge, this study explores the feasibility of diluting whole blood within a microfluidic device without external power systems. This study implemented a spiral microchannel utilizing the inertial focusing and Dean vortex effects to focus the red blood cells and extract the blood with lower hematocrit. The inertial migration of the particles during the capillary flow was first investigated experimentally; a maximum of 88% of the particles migrated to the bottom and top equilibrium positions in the optimized 350 × 60 μm (cross-sectional area, 5.8 aspect ratio) microchannel. With the optimized dimension of the microchannel, the whole blood samples within the physiological hematocrit range were tested in the experiments, and more than 10% of the hematocrit reduction was compared between the outer branch outlet and inner branch outlet in the 350 × 60 μm microchannel.