Localized surface plasmon resonance biosensor using nanopatterned gold particles on the surface of an optical fiber

Abstract Fiber-optic localized surface plasmon resonance (FO LSPR) sensors are fabricated by immobilizing metal nanoparticles on the surface of an optical fiber, and have advantages in their miniaturization, simple optical set-up, low cost, and remote sensing. However, the conventional FO LSPR sensor based on chemically synthesized metal nanoparticles lacks durability and fabrication reproducibility, due to the rearrangement and irregular sizes of metal nanoparticles. In this paper, in order to overcome these problems, focused ion beam (FIB) milling is utilized to pattern nanostructures from a metallic film deposited on the end-face of an optical fiber. We also present a design for the fabrication processes to utilize multi-mode fibers. The proposed method is evidenced by measuring the output intensities of an FO LSPR sensor for various refractive index solutions. To verify fabrication reproducibility, sensors fabricated in different batches are compared. Finally, a prostate-specific antigen (PSA) immunoassay is performed to verify the possibility of the fabricated sensor system as a biosensor. PSA is the most useful biomarker for the screening, early detection, and follow up of prostate cancer. Any change in the low PSA levels is important to detect early diagnosis and recurrence of prostate cancer. We measure the PSA to 0.1 pg/ml using the proposed FO LSPR sensor.