Label free Impedimetric Immunosensor for effective bladder Cancer detection in clinical urine samples

Galectin-1 protein has been recently recognized as a valuable urinary biomarker for the diagnosis and prognosis of bladder cancer. Herein, we present a sensitive and specific impedimetric immunosensor for the quantitative and label free detection of Galectin-1 protein in clinical urine samples. The immunosensor consists of nine gold interdigitated microelectrodes (3 × 3 array), which can simultaneously monitor multiple immunoreactions by analyzing the normalized impedance variations at each microelectrode during immunosensing. To obtain enhanced sensitivities, we have utilized Galectin-1/Al₂O₃ nanoprobes (Galectin-1 antibody conjugated to alumina nanoparticles) that can be selectively trapped on the microelectrode surface using positive dielectrophoresis (p-DEP). Preliminary studies highlight the feasibility of the proposed immunosensor for Gal -1 detection in T24 cell lysate spiked phosphate buffer saline and artificial urine samples with a limit of detection that is estimated to be in the pg/ml range. To verify its practical feasibility, we have tested the immunosensor for Galectin-1 detection in clinical urine samples obtained from normal patients and those diagnosed with bladder cancer. Analysis of the clinical tests shows that the median normalized impedance variation during immunosensing for 22 cancer patients and 26 normal patients is 27% and 10%, respectively, with an identified cutoff point of 19.5% above which the sensitivity and specificity of bladder cancer detection was 82.1% and 80.8%, respectively. Based on these results, the proposed immunosensor shows promise for bladder cancer diagnosis and prognosis in a point of care format, thus enabling improved public health monitoring.