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Microfluidics drives technological advancement in point-of-care (POC) bioanalytical diagnostics towards portability, fast response and low cost. In most microfluidic bioanalytical applications, flowing antigen/antibody reacts with immobilized antibody/antigen at a constant flux; it is difficult to reach a compromise to simultaneously realize sufficient time for the antigen–antibody interaction and short time for the entire assay. Here, we present a pump-free microfluidic chip, in which flow is self-initialized by capillary pumping and continued by imbibition of a filter paper. Microfluidic units in teardrop shape ensure that flow passes through the reaction areas at a reduced flux to facilitate the association between antigen and antibody and speeds up after the reaction areas. By spotting different antibodies into the reaction area, four types of biomarkers can be measured simultaneously in one microfluidic chip. Moreover, a small-sized instrument was developed for chemiluminescence detection and signal analysis. The system was validated by testing four biomarkers of colorectal cancer using plasma samples from patients. The assay took about 20 minutes. The limit of detection is 0.89 ng mL−1, 1.72 ng mL−1, 3.62 U mL−1 and 1.05 U mL−1 for the assays of carcinoembryonic antigen, alpha-fetoprotein, carbohydrate antigen 125 and carbohydrate antigen 19-9, respectively. This flux-adaptable and self-contained microfluidic platform is expected to be useful in various POC disease-monitoring applications. [ABSTRACT FROM AUTHOR]

• A microfluidic chip and a semi-automated immunoassay instrument were demonstrated. • Reagent loading, well washing and signal detection can be procedurally realized. • Eleven samples can be simultaneously tested within a short time. • The platform was validated using clinical serum samples for human IL-6 ELISA. Microfluidic based enzyme-linked immunosorbent assay (ELISA) has been recognized as an advanced diagnosis tool due to the reduced sample consumption and fast reaction; but it often suffers from limited throughput and requires specialized operation skills. In this paper, we developed a microfluidic chip for multi-sample ELISA and an associated instrument for fluidic delivery and colorimetric detection. Eleven different samples can be assayed simultaneously using the developed platform in a straightforward, user-friendly, and low manual workload manner. Human interleukin-6 (IL-6) was used as the model protein biomarker to validate the platform and the estimated limit of detection (LOD) is 1.262 pg/ml. The entire assay took about 35 min, which is about six-fold shorter than the assay conducted in the traditional 96-well plate. Furthermore, we validated this platform using serum samples from 89 patients with ovarian cancer. The IL-6 concentrations in the clinical samples measured by the microfluidic platform were in good agreement with the traditional well-plate measurements. High accuracy, sensitivity and specificity of 95.5%, 96.2% and 90.9% are achieved in the testing of early-stage ovarian cancer. The semi-automated microfluidic immunoassay provides a convenient, rapid and reliable method for biomedical diagnosis. [ABSTRACT FROM AUTHOR]