Application of an antibody biochip for p53 detection and cancer diagnosis

Detection of the p53 tumor suppressor gene is important in early cancer dia gnostics because alterations in the gene have been associated with carcinog enic manifestations in several tissue types in humans. We have developed an antibody-based detection instrument, the biochip, to detect the presence o f the anti-p53 antibody in human serum. The design of this highly integrate d detector system is based on miniaturized phototransistors having multiple optical sensing elements, amplifiers, discriminators, and logic circuitry on an IC board. The system utilizes laser excitation and fluorescence signa ls to detect complex formation between the p53 monoclonal antibody and the p53 antigen. Recognition antibodies are immobilized on a nylon membrane pla tform and incubated in solutions containing antigens labeled with Cy5, a fl uorescent cyanine dye. Subsequently, this membrane is placed on the detecti on platform of the biochip and fluorescence signal is induced using a 632.8 -nm He-Ne laser. Using this immuno-biochip, we have been able to detect bin ding of the p53 monoclonal antibody to the human p53 cancer protein in biol ogical matrices. The performance of the integrated phototransistors and amp lifier circuits of the biochip, previously evaluated through measurement of the signal output response for various concentrations of fluorescein-label ed molecules, have illustrated the linearity of the microchip necessary for quantitative analysis. The design of this biochip permits sensitive, selec tive and direct measurements of a variety of antigen-antibody formations at very low concentrations. Furthermore, the acquisitions of the qualitative and quantitative results are accomplished rapidly, in about 15 min. These f eatures demonstrate the potential. of this antibody-based biochip for simpl e, rapid and early biomedical diagnostics of cancer.