Disease antigens detection by silicon nanowires with the efficiency optimization of their antibodies on a chip

Enhancing the efficiency of antibody protein immobilized on a silicon nanowire-based chip for their antigens detection is reported. An external electric field (EEF) is applied to direct the orientation of antibodies during their immobilization on a chip. Atomic force microscopy (AFM) is used to measure the binding forces between immobilized antibody and targeting antigen under the influence of EEF at different angles. The maximum binding force under a specific angle (optimal angle; oa) of EEF (_maxEEF^oa) implies the optimal orientation of the antibodies on the chip. In this report, two different cancer carcinoembryonic antigen (CEA)-related cell adhesion molecules 5 (CEACAM5) & 1 (CEACAM1) were used for the examples of disease antigen detection. _maxEEF^oa of anti-CEACAM5 or anti-CEACAM1 immobilized on a general chip was firstly determined. Spectroscopy of AFM revealed that both binding forces were the largest ones with their antigens when _maxEEF^oa was applied as compared with no or other angles of EEF. These antibody proteins accompanied with the application of EEF were secondly immobilized on silicon-nanowires (n = 1000) and the field effects were measured (∆I) as their target antigens were approached. Results showed that ∆I was the largest ones when _maxEEF^oas (225°/270° and 135°/180° for anti-CEACAM5 and anti-CEACAM1, respectively) were applied as compared with other angles of EEF. These observations imply that the silicon nanowires together with the application of _maxEEF^oa as detection tools could be applied for the cancer diagnostics in the future.