Hierarchically structured microchip for point-of-care immunoassays with dynamic detection ranges.

Point-of-care (POC) medical assays provide critical information to guide clinical therapy for a broad range of medical scenarios, such as resource-poor settings and specialty departments in hospitals. Even though many types of POC assays can be done in automated devices, these POC assays typically cannot well accommodate the multiplexed detection of biomarkers where a large dynamic range is needed. Here, we report a POC assay, which is both automated and suitable for detecting multiple biomarkers with dynamic detection ranges. We call it a dynamic multiplexed immunoassay (DMI). We control the concentrations of capture antibodies and the intensity of the readout signal to dynamically modulate the detection range of immunoassays (pg mL-1 to µg mL-1), leading to the multiplexed detection of C-reactive protein (CRP), procalcitonin (PCT), and interleukin 6 (IL-6) simultaneously in undiluted human serum samples. The POC assay allows the rapid and accurate detection of infection in patients.

A hinge-based aligner for fast, large-scale assembly of microfluidic chips.

Microfluidics has shown its vitality in scientific research. But the lack of fast and straightforward approaches for aligning chip and easy-to-control on-chip valve still prevent microfluidic chips from becoming powerful commercial products. This work presents an aligner based on hinge structures, which we call a "hinge aligner", for aligning microfluidic chips. Two flat chip holders are connected by a connecting rod so that the chip holders can rotate relative to each other along the connecting rod, in the way a hinge works. The two chip holders contain pre-designed recesses for placing two chips which can align chips with 20 µm resolution. Meanwhile, with this hinge aligner, we can easily implement a fully sealed on-chip valve, which can prevent aqueous liquids from leaking even at 80 °C for 30 min. The real immunoassay result shows aligned microfluidic chips can detect protein with improved reproducibility in both high and low concentration of biomarkers.

Skiving stacked sheets of paper into test paper for rapid and multiplexed assay.

This paper shows that stacked sheets of paper preincubated with different biological reagents and skiving them into uniform test paper sheets allow mass manufacturing of multiplexed immunoassay devices and simultaneous detection of multiplex targets that can be read out by a barcode scanner. The thickness of one sheet of paper can form the width of a module for the barcode; when stacked, these sheets of paper can form a series of barcodes representing the targets, depending on the color contrast provided by a colored precipitate of an immunoassay. The uniform thickness of sheets of paper allows high-quality signal readout. The manufacturing method allows highly efficient fabrication of the materials and substrates for a straightforward assay of targets that range from drugs of abuse to biomarkers of blood-transmitted infections. In addition, as a novel alternative to the conventional point-of-care testing method, the paper-based barcode assay system can provide highly efficient, accurate, and objective diagnoses.

An automated and portable microfluidic chemiluminescence immunoassay for quantitative detection of biomarkers.

Microfluidic platforms capable of automated, rapid, sensitive, and quantitative detection of biomarkers from patient samples could make a major impact on clinical or point-of-care (POC) diagnosis. In this work, we realize an automated diagnostic platform composed of two main components: (1) a disposable, self-contained, and integrated microfluidic chip and (2) a portable instrument that carries out completely automated operations. To demonstrate its potential for real-world application, we use injection molding for mass fabrication of the main components of disposable microfluidic chips. The assembled three-layered chip with on-chip mechanical valves for fluid control consists of (1) a top silicone fluidic layer with embedded zigzag microchannels, reagent reservoirs and a negative pressure port, (2) a middle tinfoil layer with patterned antibody/antigen stripes, and (3) a bottom silicone substrate layer with waste reservoirs. The versatility of the microfluidics-based system is demonstrated by implementation of a chemiluminescence immunoassay for quantitative detection of C-reactive protein (CRP) and testosterone in real clinical samples. This lab-on-a-chip platform with features of quantitation, portability and automation provides a promising strategy for POC diagnosis.

A microfluidic indirect competitive immunoassay for multiple and sensitive detection of testosterone in serum and urine.

We demonstrate a microfluidic-based indirect competitive chemiluminescence enzyme immunoassay (MIC) for multiple, sensitive, reliable and rapid detection of testosterone in human serum and urine samples. As MIC can detect biomarkers in a cost-effective and easy-to-operate manner, it may have great potential for clinical diagnosis and point-of-care testing (POCT).

Evaluation of the effect of the structure of bacterial cellulose on full thickness skin wound repair on a microfluidic chip.

Bacterial cellulose (BC) is a kind of nanobiomaterial for tissue engineering. How the nanoscale structure of BC affects skin wound repair is unexplored. Here, the hierarchical structure of BC films and their different effects on skin wound healing were studied both in vitro and in vivo. The bottom side of the BC film had a larger pore size, and a looser and rougher structure than that of the top side. By using a microfluidics-based in vitro wound healing model, we revealed that the bottom side of the BC film can better promote the migration of cells to facilitate wound healing. Furthermore, the full-thickness skin wounds on Wistar rats demonstrated that, compared with gauze and the top side of the BC film, the wound covered by the bottom side of the BC film showed faster recovery rate and less inflammatory response. The results indicate that the platform based on the microfluidic chip provide a rapid, reliable, and repeatable method for wound dressing screening. As an excellent biomaterial for wound healing, the BC film displays different properties on different sides, which not only provides a method to optimize the biocompatibility of wound dressings but also paves a new way to building heterogeneous BC-based biomaterials for complex tissue engineering.