An immunoassay cassette with a handheld reader for HIV urine testing in point-of-care diagnostics.

Currently, most HIV tests are performed with blood samples, or alternatively saliva samples are used for HIV testing. Simple HIV tests need to be performed in hospitals or other medical agencies instead of more invasive HIV blood tests. To enable point-of-care (POC) HIV diagnostics, based on a recently developed lateral flow strip for HIV urine testing, a microfluidic immunoassay cassette with a handheld optical reader is developed. Based on lateral flow strip with gold colloid reporter, the integrated immunoassay cassette can perform sample introduction, metering, discharging, applying and detection which simplifies HIV testing. An indicator is incorporated into the cassette to guide sample introduction based on color change, and further, the excess test sample is stored inside the sealed cassette to avoid any contamination. The low-cost handheld optical reader can provide a test result within a few seconds, which is useful for simple, sensitive and affordable HIV onsite detection. Instead of using normal white LEDs, a customized back light module embedded with green LEDs is adopted to illuminate the lateral flow strip with an appropriate working current to achieve optimal performance. Compared to the standard lateral flow strips using a benchtop reader, with the disposable immunoassay cassette assisted by the handheld optical reader, more convenient, easier-to-operate, and more affordable HIV urine testing can be achieved in POC diagnostics.

Development of a Surface Plasmon Resonance and Fluorescence Imaging System for Biochemical Sensing.

Surface plasmon resonance (SPR) biosensors are an extremely sensitive optical technique used to detect the changes in refractive index occurring at the sensor interface. Fluorescence involves the emission of light by a substance that has absorbed light or other electromagnetic radiation, and the parameters of the absorbed and emitted radiation are used to identify the presence and the amount of specific molecules in a specimen. SPR biosensors and fluorescence analysis are both effective methods for real-time detection. The combination of these technologies would improve the quantitative detection sensitivity of fluorescence analysis and the specificity of SPR detection. We designed and developed an SPR and fluorescence synchronous detection system. The SPR module was based on two kinds of modulation methods, and the fluorescence module was capable of switching between four wavelengths. The fluorescence microspheres and A549 cells of different concentration were both detected by the SPR and fluorescence method synchronously in real time. The fluorescent signal and the optical signal of the SPR were shown to correlate. The correlation coefficient for fluorescent microspheres detection reached up to 0.9866. The system could be used in cell analysis and molecule diagnosis in the future.

A Single-Bead-Based, Fully Integrated Microfluidic System for High-Throughput CD4+T Lymphocyte Enumeration.

A single-bead-based, fully integrated microfluidic system has been developed for high-throughput CD4+T lymphocyte enumeration at point-of-care testing. Instead of directly counting CD4+T lymphocytes, CD4+T lymphocyte enumeration is achieved by quantitatively detecting CD4 antigen from the lysed blood sample with a functionalized polycarbonate single bead based on chemiluminescence. To implement the sandwiched chemiluminescence immunoassay with reduced nonspecific binding, a streamlined microfluidic chip with multiple reaction chambers is developed to allow each reaction step to be completed in an independent chamber where reagent is pre-stored. With simple magnetic control, the single bead with an embedded ferrous core can be consecutively transported between each of two adjacent chambers for different reactions. Meanwhile, enhanced mixing can be achieved by moving the single bead back and forth inside one chamber with magnetic actuation. High-throughput detection can be performed when a linear actuation stage is adopted to introduce synchronous magnetic control to multiple single beads in parallel microfluidic chips. A sensitive charge-coupled device (CCD) camera is adopted for high-throughput chemiluminescence detection from multiple single beads. Experimental results show that with the fully integrated microfluidic system, easy-to-operate, accurate, low-cost, immediate, and high-throughput CD4+T lymphocyte enumeration can be successfully achieved at resource-poor settings.