Sensitive molecular binding assay using a photonic crystal structure in total internal reflection

Center for Ultrafast Optical Science, University of Michigan, Ann Arbor, MI 48109-2099, USA.
Optics Express (Impact Factor: 3.49). 09/2008; 16(16):11741-9. DOI: 10.1364/OE.16.011741
Source: PubMed


A novel optical sensor for label-free biomolecular binding assay using a one-dimensional photonic crystal in a total-internal-reflection geometry is proposed and demonstrated. The simple configuration provides a narrow optical resonance to enable sensitive measurements of molecular binding, and at the same time employs an open interface to enable real-time measurements of binding dynamics. Ultrathin aminopropyltriethoxysilane/ glutaraldehyde films adsorbed on the interface were detected by measuring the spectral shift of the photonic crystal resonance and the intensity ratio change in a differential reflectance measurement. A detection limit of 6 x 10(-5) nm for molecular layer thickness was obtained, which corresponds to a detection limit for analyte adsorption of 0.06 pg/mm(2) or a refractive index resolution of 3 x 10(-8) RIU; this represents a significant improvement relative to state-of-the-art surface-plasmon-resonance-based systems.

Download full-text


Available from: James R Baker, Dec 17, 2013
  • Source
    • "Some groups have used two-photon excitation or introduced defects to allow excitation [41]. A second difficulty with 3DPCs, and also 2DPCs, is the need for nano-scale structural features that require complex nanofabrication using either top-down or self-assembly methods [42] [43]. Third, most bioassays are performed on surfaces or volumes accessible from the liquid phase. "
    [Show abstract] [Hide abstract]
    ABSTRACT: During the past decade the interactions of fluorophores with metallic particles and surfaces has become an active area of research. These near-field interactions of fluorophores with surface plasmons have resulted in increased brightness and directional emission. However, using metals provide some disadvantages, like quenching at short fluorophore-metal distances, increased rates of energy dissipation due to lossy metals. These unfavorable effects are not expected in dielectrics. In this paper we describe the interactions of fluorophores with one-dimensional (1D) photonic crystals (PCs), which have alternating layers of dielectrics with dimensions that create a photonic bandgap (PBG). Freely propagating light at the PBG wavelength will be reflected. However, similar with metals, we show that fluorophores within near-field distances of the 1DPC interacts with the structure. Our results demonstrated that these fluorophores can interact with both Internal Modes (IM) and Bloch Surface Waves (BSW) of the 1DPC. For fluorophores on the surface of the 1DPC the emission dominantly occurs through the 1DPC and into the substrate. We refer to these two phenomena together as Bragg Grating-Coupled Emission (BGCE). Here we describe our preliminary results on BGCE. 1DPCs are simple to fabricate and can be handled and reused without damage. We believe BGCE provide opportunities for new formats for fluorescence detection and sensing.
    Full-text · Article · Jul 2013 · Analytical Biochemistry
  • Source
    • "Label-free detection of chemical and biological species is a rapidly growing research area with wide applications ranging from clinical diagnostics, environmental monitoring, explosive detection, and biological research [1]. Many label-free optical sensor platforms have been established such as surface plasmon resonance [2], interferometry [3], evanescent waveguides [4], Bragg reflectors [5], photonic nanocavity laser sensors [6], and diffractive gratings [7]. These sensor techniques often require collimated readout optical beams and hence a relatively large sensing area [8]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: In this simulation study, integration of a nanocantilever inside a two-dimensional (2D) photonic crystal (PC) cavity resulted in a unique photonic crystal-cantilever cavity (PC3), where the cantilever served as a tunable mechanical defect of the PC slab. Strong nano-opto-mechanical interactions between the cantilever and the defect-mode field inside the PC3 gave rise to a high sensitivity of the resonance wavelength to surface stress-induced cantilever deflection. Mechanical and optical responses of the PC3 to surface stress changes on the cantilever surface were studied by using a finite-element method (FEM) and a finite-difference time-domain (FDTD) method, respectively. Theoretical analysis revealed that the devised PC3 sensor could resolve a conservative minimum surface stress at the level of ∼0.8 mN m−1, representing state-of-the-art cantilever sensor performance. Also, the PC3 sensor design used an ultracompact structure with an on-chip optical length of only several microns, while a conventional reflected laser beam detection scheme requires a ∼1 m long free-space optical path.
    Full-text · Article · Jul 2012 · Journal of optics
  • Source
    • "For coating as indicated in Figure 5(a), (i) the baseline was calibrated with PBS; (ii) the sensor was coated with fibronectin (200 μg/mL) and the coating was detected by measuring the resonant wavelength shift; (iii) the subsequent washes removed the unbound protein molecules, leading to a minor reduction in the resonance shift, but the substantial changes still remained indicating the effective coating of the sensor by fibronectin. The binding thickness of fibronectin on the sensor was determined to be 4.8 nm corresponding to the 4.2 nm resonance shift calculated with a transfer matrix method [31]. For protein binding as demonstrated in Figure 5(b) (blue), after (I) the coating baseline was calibrated, (II) EF-Tu was added onto the fibronectin-coated sensor surface. "
    [Show abstract] [Hide abstract]
    ABSTRACT: A conundrum has long lingered over association of cytosol elongation factor Tu (EF-Tu) with bacterial surface. Here we investigated it with Acinetobacter baumannii , an emerging opportunistic pathogen associated with a wide spectrum of infectious diseases. The gene for A. baumannii EF-Tu was sequenced, and recombinant EF-Tu was purified for antibody development. EF-Tu on the bacterial surface and the outer membrane vesicles (OMVs) was revealed by immune electron microscopy, and its presence in the outer membrane (OM) and the OMV subproteomes was verified by Western blotting with the EF-Tu antibodies and confirmed by proteomic analyses. EF-Tu in the OM and the OMV subproteomes bound to fibronectin as detected by Western blot and confirmed by a label-free real-time optical sensor. The sensor that originates from photonic crystal structure in a total-Internal-reflection (PC-TIR) configuration was functionalized with fibronectin for characterizing EF-Tu binding. Altogether, with a novel combination of immunological, proteomical, and biophysical assays, these results suggest association of A. baumannii EF-Tu with the bacterial cell surface, OMVs, and fibronectin.
    Full-text · Article · May 2012 · The Scientific World Journal
Show more