Au nanoparticle conjugation for impedance and capacitance signal amplification in biosensors.
Amplification of the electrochemical impedance and capacitance signals in a biosensor is demonstrated for the model fluorescein/anti-fluorescein system. Following immobilization of fluorescein onto Au through formation of a self-assembled monolayer, goat anti-fluorescein conjugated with 10-nm Au nanoparticles is introduced into the system. This results in an increase in the capacitance of approximately 400 nF/cm(2), whereas no change can be observed for goat anti-fluorescein without the Au nanoparticle conjugate. An even greater sensitivity is obtained by introduction of a redox probe, [Fe(CN)6]3-/4-, whereby the charge-transfer resistance (R(ct)) is reduced to approximately 25% of its original value. This allows construction of high-sensitivity electrochemical impedance biosensors at a single low frequency, where the signal is sensitive to the interfacial R(ct). This change in the electrochemical impedance signal upon binding to goat anti-fluorescein conjugated with Au nanoparticles can be attributed to the much higher electrochemical activity of Au surfaces relative to the underlying organic layer.
Department of Chemical Engineering and Center for Advanced Materials Processing (CAMP), 8 Clarkson Avenue, Clarkson University, Potsdam, New York 13699-5705, USA.
Jianbin
J
Wang
James A
JA
Profitt
Michael J
MJ
Pugia
Ian I
II
Suni
D000588:Amines / Q000032:analysis*; D000937:Antigen-Antibody Reactions; D015374:Biosensing Techniques / Q000295:instrumentation / Q000379:methods*; D004563:Electrochemistry; D004566:Electrodes; D019793:Fluorescein / Q000032:analysis; D006046:Gold / Q000032:analysis*; D008855:Microscopy, Electron, Scanning / Q000379:methods; D053758:Nanoparticles / Q000032:analysis*; D010316:Particle Size; D012680:Sensitivity and Specificity; D013499:Surface Properties; D013997:Time Factors
D000588:Amines; D006046:Gold; D019793:Fluorescein