Amplification Strategy of FET Biosensor Signal for Sensitive Detection of Prion Proteins
In this research, we designed two approaches of charge amplification including (i) addition of metal ions as second ligand, and (ii) chemical modification via coupling reaction as illustrated at Figure 1. These strategies were performed into the target protein that can increase the charge of proteins, leading to the enhancement of FET signal. Here, we used and detected prion proteins as a model of the target protein. Highly sensitive method for detecting prion proteins is a top priority for early diagnosis and minimizing the spread of the diseases , and the amplified FET signal is of utmost importance to meet the goal for improving the sensitivity of prion detection to the lowest concentration as possible.
Firstly, by utilizing thiamine as probe molecule, the surface of FET biosensor can specifically interact with the prion protein as confirmed by FET response, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) analysis . Then, the sensitivity of thiamine-immobilized FET to the prion protein in human serum sample before the use of amplification step was quantitatively determined and achieved at the concentration of 400 pM, which is also lower than the cut-off value (2 nM). Furthermore, the amplification process was applied. As for approach (i), by taking the advantage of specific interaction between prion protein and copper (II) ions (Cu2+), a model of dual-ligand binding consist of thiamine immobilized surface, prion protein and Cu2+was performed and successfully generated an enhancement of FET response. As for approach (ii), we demonstrated the feasibility of protein modification with conventional coupling reaction, converting the carboxylate group (anionic) to the amino group (cationic) of prion protein. These strategies can result higher electrical signals in prion detection based on FET biosensor. The detail of experimental procedure and mechanism will be discussed further in the conference. In summary, the FET biosensor device could provide a promising technique and a pave way for highly sensitive detection of prion protein.
- M. J. Schöning and A. Poghossian, Analyst, 127, 1137-1151 (2002).
- J. Castilla, P. Saa, C. Soto, Nature, 11, 982-985 (2005).
- S. Wustoni, S. Hideshima, S. Kuroiwa, T. Nakanishi, M. Hashimoto, Y. Mori, T. Osaka, Biosens. Bioelect., 67, 256-262 (2015).