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The optical fiber deposits with gold nanorods was successfully accomplished as a biosensor device which sensing to the refractive index change on the surrounding surface. The principle is based on the localized surface plasmon resonance (LSPR) occurs on the metal surface of gold nanorods (AuNRs). The gold nanorods were coated on the glass core fiber surface through the covalent bond. The uncladded area fiber optic was incubated in 5% of (3-Mercaptopropyl) trimethoxysilane (MPTMS) in ethanol for overnight to alter the thiol group on the surface. The gold nanorods with aspect ratio ⁓2.035 was deposited on thiol surface by incubation the optical fiber in gold nanorod solution for 6 hr. The sensor provides the sensitivity of 4.94×104 a.u./RIU. Moreover, antibody for blood grouping was immobilized on the AuNRs-optical fiber to detect the red blood cells. The AuNRs-optical fiber can detect A antigen on the immobilized anti-A surface with Δ%T of 0.98 and can detect B-antigen on the immobilized anti-B surface with Δ%T of 1.78. This work possesses possibility of a simple AuNRs-optical fiber to detect the biomolecular interaction.

In this research studied on the conjugation of antibodies on gold nanoparticles (GNPs) and the optimization in term of antibody concentration and albumin blocking concentration. Gold nanoparticleswith diameter size of ~20 nm were synthesized via chemical reduction of HAuCl4 with trisodium citrate as reducing and stabilizing agent. Gold nanoparticles and anti-A antibody at various concentrations were mixed and nonspecific binding sites were blocked by using bovine serum albumin (BSA) at various concentrations. The antibody conjugated gold nanoparticles were tested by coagulation with 1% sodium chloride salt solution to obtain the optimal antibody concentration. BSA 50, 100 and 200 μg/mL were added in solution after antibody covered on gold nanoparticles. The solutions were characterized by measuring absorbance spectra. From the results found that the optimal concentration of antibodies and BSA blocking were 45 μg/mL and 50 μg/mL, respectively. The anti-A conjugated gold nanoparticles were tested with saliva of blood group A sample to monitor the specific interaction between antibody on gold surface and antigen in saliva via the change of absorbance spectra.