title: Development and application of a real-time capacitive sensor.
abstract: A real-time capacitive sensor based on a potentiostatic step method was developed. It can display in real-time the evoked current waveform, capacitance and the electrical resistance of elements serially connected to the insulation layer on the electrode as a function of time as well as the ohmic resistance of the insulation layer. These features enable the user to observe the association and dissociation of the affinity binding pairs and to evaluate the insulating property of the electrode surface during measurement. The system allows the setting of potential pulse height, pulse interval, gain, filter, and sampling frequency, enabling the system to be more flexible. The performance of the system was firstly evaluated with equivalent circuits. Under suitable parameter settings it provided good accuracy of both the capacitance and resistance. Using the affinity binding pair of human serum albumin (HSA) and anti human serum albumin (anti-HSA) the measured capacitance change was used for the direct detection of HSA. The developed system provided the same sensitivity as the commercially available potentiostat (P>0.05). The proposed system was then applied to analyse HSA in real urine samples and the results agreed well with the immunoturbidimetric assay (P>0.05). The proposed system can be applied for capacitance measurement to directly detect other target analytes using different affinity binding pairs. Other applications such as kinetics analysis of the interaction between affinity bindings, thickness analysis, and the study of the insulation property of the modified layer are also promising.
authors.affiliation: Trace Analysis and Biosensor Research Center, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand.
authors.forename: Booncharoen
authors.initials: B
authors.lastname: Wongkittisuksa
authors.forename: Chusak
authors.initials: C
authors.lastname: Limsakul
authors.forename: Proespichaya
authors.initials: P
authors.lastname: Kanatharana
authors.forename: Warakorn
authors.initials: W
authors.lastname: Limbut
authors.forename: Punnee
authors.initials: P
authors.lastname: Asawatreratanakul
authors.forename: Supaporn
authors.initials: S
authors.lastname: Dawan
authors.forename: Suchera
authors.initials: S
authors.lastname: Loyprasert
authors.forename: Panote
authors.initials: P
authors.lastname: Thavarungkul
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation*; D003199:Computer Systems; D003217:Conductometry / Q000295:instrumentation*; D025802:Electric Capacitance; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D007118:Immunoassay / Q000295:instrumentation*; D012709:Serum Albumin / Q000032:analysis*
chemical_list: D012709:Serum Albumin