Surface-Plasmon-Resonance Amplification of FMD Detection through Dendrimer Conjugation

Abstract

The amplification of the surface plasmon resonance (SPR) sensitivity for the foot-and-mouth disease (FMD) detection was studied using Poly(amidoamine) (PAMAM) succinamic-acid dendrimers. The dendrimers were conjugated with the complementary annealed with the aptamers capable of binding specifically to FMD peptides. The tethered layer of the dendrimer-conjugated double-stranded(ds)-aptamers was formed on the SPR sensor Au surface via a thiol bond between the aptamers and Au. After the tethered layer was formed, the surface was taken out of the SPR equipment. Then, the ds-aptamers on the surface were denatured to collect the dendrimer-conjugated single-stranded(ss)-complementary. The surface with only the remaining ss-aptamers was transferred again to the equipment. Two types of the injections, the FMD peptide only and the dendrimer-conjugated ss-complementary followed by the FMD peptides, were performed on the surface. The sensitivity was increased 20 times with the conjugation of the dendrimers, but the binding rate of the peptides became more than two times slower.

Keywords: aptamer; dendrimer; foot-and-mouth disease; sensitivity; surface plasmon resonance.

Figure 1

Schematic diagram for the experimental procedures.

Figure 2

Diameter distribution before (A) and after (B) conjugation between the ds aptamers and dendrimers.

Figure 3

Optical signal for the layer formation of the dendrimer-conjugated ds aptamers on the SPR sensor Au surface: formation (solid circle) and fitting to the signal (solid line).

Figure 4

Optical signals for the correlation with FMD peptide concentration (A) and for the binding between FMD peptides and the ss aptamers remaining on the SPR sensor Au surface: 10, 20, and 40 nM FMD peptide concentration (triangle, diamond, and square, respectively) and fittings to the signals (solid lines) (B).

Figure 5

Optical signals for the correlation with the FMD peptide concentration (A) and for the binding between the FMD peptides and ds aptamers, which released the dendrimer-conjugated ss-complementary: 1, 2, and 4 nM FMD peptide concentrations (diamond, square, and asterisk, respectively) and fittings to the signals (solid lines) (B).