Sensitive biosensor array using surface plasmon resonance on metallic nanoslits.

Academia Sinica, Research Center for Applied Sciences, 128 Section 2, Academia Road, Nankang, Taipei 11529, Taiwan.
Journal of Biomedical Optics (Impact Factor: 2.75). 01/2007; 12(4):044023. DOI: 10.1117/1.2772296
Source: PubMed

ABSTRACT Chip-based biosensor arrays for label-free and high-throughput detection were fabricated and tested. The sensor array was composed of a 150-nm-thick, 50-nm-gap, and 600-nm-period gold nanoslits. Each array size was 100 mumx100 mum. A transverse-magnetic polarized wave in these metallic nanostructures generated resonant surface plasmons at a wavelength of about 800 nm in a water environment. Using the resonant wavelength shift in the nanoslit array, we achieved detection sensitivity up to 668 nm per refractive index unit, about 1.7 times larger than that reported on an array of nanoholes. An antigen-antibody interaction experiment in an aqueous environment verified the sensitivity in a surface binding event.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Label-free detection of rare cells in biological samples is an important and highly demanded task for clinical applications and various fields of research, such as detection of circulating tumor cells for cancer therapy and stem cells studies. Surface Plasmon Resonance (SPR) as a label-free method is a promising technology for detection of rare cells for diagnosis or research applications. Short detection depth of SPR (400 nm) provides a sensitive method with minimum interference of non-targets in the biological samples. In this work, we developed a novel microfluidic chip integrated with gold nanoslit SPR platform for highly efficient immunomagnetic capturing and detection of rare cells in human blood. Our method offers simple yet efficient detection of target cells with high purity. The approach for detection consists of two steps. Target cells are firs captured on functionalized magnetic nanoparticles (MNPs) with specific antibody I. The suspension containing the captured cells (MNPs-cells) is then introduced into a microfluidic chip integrated with a gold nanoslit film. MNPs-cells bind with the second specific antibody immobilized on the surface of the gold nanoslit and are therefore captured on the sensor active area. The cell binding on the gold nanoslit was monitored by the wavelength shift of the SPR spectrum generated by the gold nanoslits.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Nanostructure-based sensors are capable of sensitive and label-free detection for biomedical applications. However, plasmonic sensors capable of highly sensitive detection with high-throughput and low-cost fabrication techniques are desirable. We show that capped gold nanoslit arrays made by thermal-embossing nanoimprint method on a polymer film can produce extremely sharp asymmetric resonances for a transverse magnetic-polarized wave. An ultrasmall linewidth is formed due to the enhanced Fano coupling between the cavity resonance mode in nanoslits and surface plasmon resonance mode on periodic metallic surface. With an optimal slit length and width, the full width at half-maximum bandwidth of the Fano mode is only 3.68 nm. The wavelength sensitivity is 926 nm/RIU for 60-nm-width and 1,000-nm-period nanoslits. The figure of merit is up to 252. The obtained value is higher than the theoretically estimated upper limits of the prism-coupling SPR sensors and the previously reported record high figure-of-merit in array sensors. In addition, the structure has an ultrahigh intensity sensitivity up to 48,117%/RIU.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Gold (Au) is so far the most commonly used plasmonic metal in nanohole-array-based surface plasmon resonance biosensors, due to its excellent plasmonic properties in visible light range and chemical inertness in solutions. However, Au intrinsically absorbs blue-green light heavily, leading to poor plasmonic excitation efficiency below 600 nm. This work explores the possibilities of using various kinds of plasmonic metals (Au, Ag, Cu, Al) or their composites (Ag/Au, Cu/Au, Al/Au) in nanohole-array surface plasmon field-enhanced fluorescence spectroscopy (SPFS) biosensors, aiming to excite different fluorescent dyes (working in different wavelength ranges) with satisfactory plasmonic performance. It is found that SiO2 anti-tarnish-coated Ag nanohole array is suitable and practical for exciting 400–500-nm fluorescent dyes. The Au-coated Al nanohole array supports a very good plasmon resonance for fluorescence excitation in 600–700 nm, whose field enhancement even exceeds that of pure Au. The combination of Au and Ag is found to be superior to pure Au or Ag for the 500–600- or 700–800-nm fluorescent dyes. These findings provide the guideline on selecting suitable plasmonic metals for nanohole-array SPFS biosensors.
    Plasmonics 08/2014; 9(4):825-833. DOI:10.1007/s11468-014-9667-6 · 2.74 Impact Factor

Full-text (2 Sources)

Available from
May 22, 2014