Immunosensor for the ultrasensitive and quantitative detection of bladder cancer in point of care testing.

An ultrasensitive and real-time impedance based immunosensor has been fabricated for the quantitative detection of Galectin-1 (Gal-1) protein, a biomarker for the onset of multiple oncological conditions, especially bladder cancer. The chip consists of a gold annular interdigitated microelectrode array (3×3 format with a sensing area of 200µm) patterned using standard microfabrication processes, with the ability to electrically address each electrode individually. To improve sensitivity and immobilization efficiency, we have utilized nanoprobes (Gal-1 antibodies conjugated to alumina nanoparticles through silane modification) that are trapped on the microelectrode surface using programmable dielectrophoretic manipulations. The limit of detection of the immunosensor for Gal-1 protein is 0.0078mg/ml of T24 (Grade III) cell lysate in phosphate buffered saline, artificial urine and human urine samples. The normalized impedance variations show a linear dependence on the concentration of cell lysate present while specificity is demonstrated by comparing the immunosensor response for two different grades of bladder cancer cell lysates. We have also designed a portable impedance analyzing device to connect the immunosensor for regular checkup in point of care testing with the ability to transfer data over the internet using a personal computer. We believe that this diagnostic system would allow for improved public health monitoring and aid in early cancer diagnosis.

Enhancing of intensity of fluorescence by DEP manipulations of polyaniline-coated Al2O3 nanoparticles for immunosensing.

A novel modification of low-cost Al2O3 nanoparticles (Al2O3 NPs) for antibody-protein immunosensing is proposed. The modified NPs are utilized to enhance the intensity of fluorescence in a dielectrophoretic (DEP) chip with a microelectrode array. The surface of the Al2O3 NPs is modified by ionic polyaniline (PANDB) rather than the conventional silane (3-aminopropyltrimethoxysilane) to conjugate the antibody on the outer shell. After the PANDB-Al2O3 NPs is functionalized to form probes, a DEP chip with a vertical non-uniform electric field that is produced by top and bottom electrodes condenses and immobilizes the nanoprobes on the surface of the electrodes by positive DEP force for immunosensing of the fluorescent protein. Additionally, each microelectrode array can be individually controlled with/without DEP manipulation using a computer program. Experimental results indicate that PANDB-based nanoprobes provide more rapid and sensitive immunosensing than those having undergone conventional silane modification. During immunosensing, fluorescence intensity can be doubled by the application of extra DEP force. The individual control of NPs on the microelectrode array has great potential for applications in multi-antibody arrays in a single chip for immunosensing.