Label-free cancer markers detection by capacitance biochip

This paper investigates technological advancements in developing reliable technologies for label free detection of cancer markers. Capacitance detection was used successfully to develop an immunosensor. Rigorous probe immobilization was implemented to obtain reliable capacitance measurements. The commonly considered alkanethiols for proteins immobilization do not allow sufficiently stable capacitance measurements. Therefore, new ethylene-glycol functionalized alkanethiols were used as more suitable materials to develop lab-on-a-chip detection of cancer markers. Results from AFM, Chemi-luminescence, Fluorescence, Cyclic Voltammetry, QCM, and capacitance measurements showed that three (ethylene-glycol) alkanethiols highly stabilized the sensing surfaces in time. The measured capacitance on the antibody layers was in the range of 60–70 nF/cm2 and 80–115 nF/cm2 for the antigen detection. The developed system was utilized to detect the Hepatocarcinoma marker SCCA, and the whole IgM fraction from Hepatocarcinoma patient’s serum. Electrode by electrode reproducibility within the same chip increased by one order of magnitude (variations were reduced from 30–40% down to less than 2%) using these new alkanethiols, while the reached limit in sensitivity was close to 2.43 μg/ml.