Assessing levels of neuropeptide Y (NPY) in the human body has many medical uses. Accordingly, we report the quantitative detection of NPY biomarkers applying guided-mode resonance (GMR) biosensor methodology. The label-free sensor operates in the near-infrared spectral region exhibiting distinctive resonance signatures. The interaction of NPY with bioselective molecules on the sensor surface causes spectral shifts that directly identify the binding event without additional processing. In the experiments described here, NPY antibodies are attached to the sensor surface to impart specificity during operation. For the low concentrations of NPY of interest, we apply a sandwich NPY assay in which the sensor-linked anti-NPY molecule binds with NPY that subsequently binds with anti-NPY to close the sandwich. The sandwich assay achieves a detection limit of ~0.1 pM NPY. The photonic sensor methodology applied here enables expeditious high-throughput data acquisition with high sensitivity and specificity. The entire bioreaction is recorded as a function of time, in contrast to label-based methods with single-point detection. The convenient methodology and results reported are significant, as the NPY detection range of 0.1–10 pM demonstrated is useful in important medical circumstances.

This research addresses fuel biocontaminant sensing using resonant photonic gratings. The fundamental photonic resonance physics enables compact, economic sensors that provide a rapid, quantitative, and effective modality for detecting and monitoring biochemical bindings. Thus, we present resonant sensors and attendant surface chemistry targeting yeast cells as representative biofouling agents. We apply biorecognition elements (BREs) to functionalize the dielectric grating surface (TiO2) to produce a sensitive, quantitative wavelength shift-based assay for detecting Yarrowia yeast cells. Concanavalin A (Con A) is used as a BRE consisting of carbohydrate-binding proteins binding to ligands on the yeast cell surface. Corresponding resonance wavelength shifts are measured relative to concentration expressed in log10[C] where C represents the concentration of cells in solution. The assay is shown to be highly specific for detecting Yarrowia cells in various concentrations. The experimental limit of detection (LOD) of the assay is 1.92 for yeast cells in culture media and 1.22 for cells in phosphate buffer saline (PBS). The comparisons of the various functionalization methods show that (3-aminopropyl)triethoxysilane (APTES) with glutardialdehyde (GA) and Con A protocol provides optimal detection of cells in PBS.

We discuss the design, fabrication, and characterization of silicon-nitride microring resonators for nonlinear-photonic and biosensing device applications. The first part presents new theoretical and experimental results that overcome highly normal dispersion of silicon-nitride microresonators by adding a dispersive coupler. The latter parts review our work on highly efficient second-order nonlinear interaction in a hybrid silicon-nitride slot waveguide with nonlinear polymer cladding and silicon-nitride microring application as a biosensor for human stress indicator neuropeptide Y at the nanomolar level.

We report the design, fabrication, and characterization of a silicon-nitride (SiN) microring-resonator-based label-free biosensor for the purpose of neuropeptide Y (NPY) protein detection. NPY is commonly associated with stress in human body. The device uses evanescent field sensing, its geometry is optimized for 1550-nm signal, and it is fabricated by following standard CMOS processes. Top surface of the device is designed to function in aqueous environment and appropriately functionalized to ensure the biomaterial-specific attachment. The time-dependent spectral response to the biomaterial attachment is observed by scanning a tunable laser source around 1550 nm and measuring the resonance shift in the transmission spectrum. We experimentally achieve the detection into nanomolar concentration level in a regular assay system with 0.1 nm/( μg/mL) of sensitivity and ~ 30 mins of analysis time. This sensitivity is further amplified by a factor of three with a sandwiched assay technique, with which ~ 58 nM ( 0.25 μg/mL) concentration of NPY is successfully detected.