title: Effects of the electrode size and modification protocol on a label-free electrochemical biosensor.
abstract: In the present work, the effect of a surface modification protocol along with the electrode size has been investigated for developing an efficient, label-free electrochemical biosensing method for diagnosis of traumatic brain injury (TBI) biomarkers. A microdisk electrode array (MDEA) and a macroelectrode with a comb structure (MECS) were modified with an anti-GFAP (GFAP = glial fibrillary acidic protein) antibody using two protocols for optimum and label-free detection of GFAP, a promising acute-phase TBI biomarker. For the MDEA, an array of six microdisks with a 100 μm diameter and, for the MECS, a 3.2 mm × 5.5 mm electrode 5 μm wide with 10 μm spaced comb fingers were modified using an optimized protocol for dithiobis(succinimidyl propionate) (DSP) self-assembled monolayer formation. Anti-GFAP was covalently bound, and the remaining free DSP groups were blocked using ethanolamine (Ea). Sensors were exposed to solutions with different GFAP concentrations, and a label-free electrochemical impedance spectroscopy (EIS) technique was used to determine the concentration. EIS results confirmed that both types of Ea/anti-GFAP/DSP/Au electrodes modified with an optimized DSP-based protocol can accurately detect GFAP in the range of 1 pg mL(-1) to 100 ng mL(-1) with a detection limit of 1 pg mL(-1). However, the cross-use of the MDEA protocol on the MECS and vice versa resulted in very low sensitivity or poor signal resolution, underscoring the importance of proper matching of the electrode size and type and the surface modification protocol.
authors: Bioelectronics Programme, Institute of Microelectronics, A*STAR (Agency for Science, Technology and Research), Singapore Science Park II, Singapore. sunilarya333@gmail.com
authors: Sunil K
authors: SK
authors: Arya
authors: Tze Sian
authors: TS
authors: Pui
authors: Chee Chung
authors: CC
authors: Wong
authors: Sai
authors: S
authors: Kumar
authors: Abdur Rub Abdur
authors: AR
authors: Rahman
mesh_terms: D000906:Antibodies / Q000737:chemistry*; D015415:Biomarkers / Q000032:analysis; D015374:Biosensing Techniques / Q000379:methods* / Q000592:standards; D003217:Conductometry; D058266:Dielectric Spectroscopy / Q000379:methods / Q000592:standards; D004566:Electrodes / Q000592:standards; D004867:Equipment Design; D019856:Ethanolamine / Q000737:chemistry; D005904:Glial Fibrillary Acidic Protein / Q000032:analysis* / Q000737:chemistry; D006046:Gold / Q000737:chemistry; D006801:Humans; D057230:Limit of Detection; D012996:Solutions / Q000737:chemistry; D013388:Succinimides / Q000737:chemistry
chemical_list: D000906:Antibodies; D015415:Biomarkers; D005904:Glial Fibrillary Acidic Protein; D012996:Solutions; D013388:Succinimides; D019856:Ethanolamine; D006046:Gold; C011240:dithiobis(succinimidylpropionate)