Immunoassay of prostate-specific antigen (PSA) using resonant frequency shift of piezoelectric nanomechanical microcantilever.
We designed and fabricated the nanomechanical Pb(Zr0.52Ti0.48)O3 (PZT) cantilever; we demonstrated a novel electrical measurement, under a controlled ambient temperature and humidity, for label-free detection of a prostate-specific antigen (PSA); and we achieved a detection sensitivity as low as 10 pg/ml. For the fabrication of our nanomechanical PZT cantilevers, we used composite layers of Ta/Pt/PZT/Pt/SiO2 on a SiN(x) supporting layer for electrical self-sensing without external oscillators. This method allows PSA proteins to be detected via a simple electrical measurement of the resonant frequency change generated by the molecular interaction of the antigen (Ag) and the antibody (Ab). The resonant frequency shifted due to the specific binding of the PSA Ag to its Ab which is immobilized via calixcrown self-assembled monolayers on an Au surface deposited on a nanomechanical PZT cantilever. We determined the resonant frequency shift as the value of -172 Hz and -273 Hz, when the concentration of PSA Ag was 1 ng/ml, with the cantilever dimensions of 100 microm x 300 microm and 50 microm x 150 microm, respectively. Theoretical and experimental analysis suggests that the minimum detectable sensitivity for a resonant frequency shift due to a PSA Ag-Ab interaction depends on the dimensions of the nanomechanical PZT cantilever. These results also demonstrate that the experimentally measured resonant frequency shift is larger than that calculated theoretically due to the compressive stress of the PSA Ag-Ab interaction.
Lee
Jeong Hoon
JH
Microsystem Research Center, KIST, Seoul 136-791, Korea.
Hwang
Kyo Seon
KS
Park
Jaebum
J
Yoon
Ki Hyun
KH
Yoon
Dae Sung
DS
Kim
Tae Song
TS
D014408:Biomarkers, Tumor / Q000097:blood*; D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods; D017097:Electric Impedance; D004563:Electrochemistry / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D007118:Immunoassay / Q000295:instrumentation* / Q000379:methods; D008297:Male; D019563:Mechanics; D036103:Nanotechnology / Q000295:instrumentation* / Q000379:methods; D017430:Prostate-Specific Antigen / Q000097:blood* / Q000276:immunology; D011471:Prostatic Neoplasms / Q000097:blood / Q000175:diagnosis; D014159:Transducers
D014408:Biomarkers, Tumor; D017430:Prostate-Specific Antigen