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.
Wang
Jianbin
J
Department of Chemical Engineering and Center for Advanced Materials Processing (CAMP), 8 Clarkson Avenue, Clarkson University, Potsdam, New York 13699-5705, USA.
Profitt
James A
JA
Pugia
Michael J
MJ
Suni
Ian I
II
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