Paper Title
The Effect of Bovine Serum Albumin to Platform of Electrochemical Immunosensor for Hepatocellular Carcinoma Detection

Hepatocellular carcinoma (HCC) diagnosis is commonly accomplished by biomarker testing. Alpha-fetoprotein (AFP) is the most widely used biomarker for HCC during the past several decades. Most of the biomarker tests that have been developed are time-consuming and not sensitive enough for HCC early screening. To overcome these limitations, an alternative method for AFP detection based on electrochemical immunosensor was developed using Electrochemical Impedance Spectroscopy (EIS) technique. An immunoassay based on direct Enzyme-Linked Immunosorbent Assay (ELISA) was performed on a commercial screen-printing carbon electrode (SPCE) instead of a 96-well plate. 1-pyrenebutanoic acid succinimidyl ester was used as an immobilizing agent to immobilize AFP antibody effectively on the electrode surface. However, this platform needed to be adjusted for signal enhancement because AFP antigen-antibody complex molecules on SPCE was so small that cannot bring about significant electrical signal change. Thereby, many different amounts of Bovine Serum Albumin (BSA) was optimized for signal enhancement purpose. The results showed that mixing 0.2 % wt/vol BSA with AFP can enhance signal of the specific antigen-antibody complex molecules considerably as it created more double layer charges between electrode surface and Fe(CN)6 3-/4-. More double layer charges hindered Fe(CN)6 3-/4- to diffuse from bulk solution to electrode surface and caused more resistance at the interface. On the other hand, mixing 0.5% and 1% wt/vol BSA with AFP concealed the signal of AFP antigen-antibody complex molecules. Too much amount of BSA created too much double layer charges that overcame small impedance signal change from the formation of AFP antigen-antibody complex molecules. Keywords: Hepatocellular Carcinoma (HCC), Alpha-Fetoprotein (AFP), Electrochemical Impedance Spectroscopy (EIS), Direct Enzyme-Linked Immunosorbent Assay (ELISA), Screen-Printing Carbon Electrode (SPCE), 1-Pyrenebutanoic Acid Succinimidyl Ester, Bovine Serum Albumin (BSA)