Resonant Photonic Biosensors with Polarization-Based Multiparametric Discrimination in Each Channel

In this paper, we describe guided-mode resonance biochemical sensor technology. We briefly discuss sensor fabrication and show measured binding dynamics for example biomaterials in use in our laboratories. We then turn our attention to a particularly powerful attribute of this technology not possessed by competing methods. This attribute is the facile generation of multiple resonance peaks at an identical physical location on the sensor surface. These peaks respond uniquely to the biomolecular event, thereby enriching the data set available for event quantification. The peaks result from individual, polarization-dependent resonant leaky modes that are the foundation of this technology. Thus, by modeling the binding event and fitting to a rigorous electromagnetic formalism, we can determine individual attributes of the biolayer and its surroundings and avoid a separate reference site for background monitoring. Examples provide dual-polarization quantification of biotin binding to a silane-coated sensor as well as binding of the cancer biomarker protein calreticulin to its monoclonal IgG capture antibody. Finally, we present dual-polarization resonance response for poly (allylamine hydrochloride) binding to the sensor with corresponding results of backfitting to a simple model; this differentiates the contributions from biolayer adhesion and background changes

Magnetic Nanoparticle-Based Nano-Grating Guided-Mode Resonance Biosensors

Biomolecular detection systems based on monitoring changes in the refractive indices of functionalized surfaces are promising for applications as chemical and biological sensors. Here, we describe the design and figures of merit of our refractive index-based guided-mode resonance (GR) biosensor consisting of thin film silicon nitride sub-wavelength nano-gratings. The sensitivity of our nano-grating GR sensor was experimentally determined to be 59.3 nm per refractive index unit. We describe how the wavelength for maximum intensity of diffraction (peak wavelength) of nano-gratings was affected when functionalized magnetic nanoparticles (MNPs) were attached onto GR sensor surfaces. Moreover, we demonstrate with avidin-biotin model experiments that attaching MNPs to sensor surfaces enhances the dynamic range of detection of the GR system detection. The peak wavelength value (PWV) shifted by 0.35 nm in the case of avidin with a concentration of avidin 400 nmol/L immobilized on the sensor surface. In contrast, we achieved a 1.41 nm PWV shift after adding 5% MNPs to the solution of avidin. Not only did the MNPs enhance the dynamic range of detection, but also magnetically induced interaction of avidin-biotin significantly reduced the detection time

Fabrication, instrumentation and application for subwavelength periodic nanophotonic devices

This dissertation focuses on developing novel and efficient fabrication methodology for periodic nanostructures based nanophotonic devices, especially variable or tunable optical/photonic devices that based on photonic crystal or plasmonic crystal slabs. These nanophotonic devices are optically characterized to demonstrate the effectiveness. This dissertation starts by developing an angular-dispersion detection instrument based on a one-dimensional photonic crystal. This instrument was demonstrated to have applications in chemical sensing and imaging by monitoring the guided-mode resonance (GMR) supported in the PC sensor comprised of a one-dimensional grating structure. Exposed to solutions with different refractive indices or adsorbed with biomaterials, the PC sensor exhibited changes of the optical resonant modes. In order to fabricate tunable nanophotonic devices with continuously varying resonant wavelengths, two different approaches were explored in this dissertation. The first approach is to introducing graded geometry into the structure of the device, such as a varying period over the device surface. To accomplish this, a strain-tunable soft lithography method is developed using PDMS masters as the replicate molds. The process exploits an elastomeric mold made of PDMS to generate the designed periodic pattern in a UV curable polymer (UVCP) on glass or plastic substrates. During the imprint and curing process, the PDMS mold was mechanically deformed by a uniaxial force, which causes the periodic pattern carried on the PDMS mold to vary as designed. By control the stretching direction and magnitude of the applied force carefully, the lattice constant and arrangement can be determined. For example, by stretching the mold with a 2D array in a square lattice, rectangular and triangular lattice arrangements can be obtained. As a specific application, we have applied this programmable nanoimprint lithography method to create a linear variable photonic crystal (PC) filter with continuously tunable resonant wavelength covering a wide spectral range along its length. The other approach is incorporating materials with tunable optical properties into the constituent material of the periodic nanophotonic devices. In this dissertation, a thin layer of phase-change material, Ge2Sb2Te5ïÿý (GST), in nanometers was embedded in the waveguide layer of a photonic crystal (PC) structure. The PC structure is based on a one-dimensional grating with a zinc sulfide waveguide. The GST-incorporated PC (GST-PC) structure supports the guided-mode resonance (GMR) that selectively absorbs light at particular wavelengths. The tuning effects were experimentally demonstrated by the crystallization or re-amorphization of the GST thin film. The GST-PC device opens a new path for tuning optical resonances in the near infrared region. Potential applications include color generation, display, optical storage, optical switches, and optical filters. At last, a novel fabrication method for an ultrathin freestanding gold plasmonic membrane is proposed. The freestanding plasmonic membrane was characterized using FT-IR, and demonstrated to support extraordinary optical transmission in the mid infrared wavelength range. The effect of the thickness of gold was also investigated. This plasmonic device was utilized as a surface-based optical sensor by measuring the absorption of the stretching modes of chemical bonds in the Mid-IR

Design, fabrication and characterization of resonant waveguide grating based optical biosensors

The absence of rapid, low cost and highly sensitive biodetection platform has hindered the implementation of next generation cheap and early stage clinical or home based point-of-care diagnostics. Label-free optical biosensing with high sensitivity, throughput, compactness, and low cost, plays an important role to resolve these diagnostic challenges and pushes the detection limit down to single molecule. Optical nanostructures, specifically the resonant waveguide grating (RWG) and nano-ribbon cavity based biodetection are promising in this context. The main element of this dissertation is design, fabrication and characterization of RWG sensors for different spectral regions (e.g. visible, near infrared) for use in label-free optical biosensing and also to explore different RWG parameters to maximize sensitivity and increase detection accuracy. Design and fabrication of the waveguide embedded resonant nano-cavity are also studied. Multi-parametric analyses were done using customized optical simulator to understand the operational principle of these sensors and more important the relationship between the physical design parameters and sensor sensitivities. Silicon nitride (SixNy) is a useful waveguide material because of its wide transparency across the whole infrared, visible and part of UV spectrum, and comparatively higher refractive index than glass substrate. SixNy based RWGs on glass substrate are designed and fabricated applying both electron beam lithography and low cost nano-imprint lithography techniques. A Chromium hard mask aided nano-fabrication technique is developed for making very high aspect ratio optical nano-structure on glass substrate. An aspect ratio of 10 for very narrow (~60 nm wide) grating lines is achieved which is the highest presented so far. The fabricated RWG sensors are characterized for both bulk (183.3 nm/RIU) and surface sensitivity (0.21nm/nm-layer), and then used for successful detection of Immunoglobulin-G (IgG) antibodies and antigen (~1μg/ml) both in buffer and serum. Widely used optical biosensors like surface plasmon resonance and optical microcavities are limited in the separation of bulk response from the surface binding events which is crucial for ultralow biosensing application with thermal or other perturbations. A RWG based dual resonance approach is proposed and verified by controlled experiments for separating the response of bulk and surface sensitivity. The dual resonance approach gives sensitivity ratio of 9.4 whereas the competitive polarization based approach can offer only 2.5. The improved performance of the dual resonance approach would help reducing probability of false reading in precise bio-assay experiments where thermal variations are probable like portable diagnostics

Development and optimisation of photonic crystal based nanosensors

This thesis involved the development of two Biosensors and their associated assays for the detection of diseases, namely IBR and BVD for veterinary use and C1q protein as a biomarker to pancreatic cancer for medical application, using Surface Plasmon Resonance (SPR) and nanoplasmonics. SPR techniques have been used by a number of groups, both in research [1-3] and commercially [4, 5] , as a diagnostic tool for the detection of various biomolecules, especially antibodies [6-8]. The biosensor market is an ever expanding field, with new technology and new companies rapidly emerging on the market, for both human [8] and veterinary applications [9, 10]. In Chapter 2, we discuss the development of a simultaneous IBR and BVD virus assay for the detection of antibodies in bovine serum on an SPR-2 platform. Pancreatic cancer is the most lethal cancer by organ site, partially due to the lack of a reliable molecular signature for diagnostic testing. C1q protein has been recently proposed as a biomarker within a panel for the detection of pancreatic cancer. The third chapter discusses the fabrication, assays and characterisation of nanoplasmonic arrays. We will talk about developing C1q scFv antibody assays, clone screening of the antibodies and subsequently moving the assays onto the nanoplasmonic array platform for static assays, as well as a custom hybrid benchtop system as a diagnostic method for the detection of pancreatic cancer. Finally, in chapter 4, we move on to Guided Mode Resonance (GMR) sensors, as a low-cost option for potential use in Point-of Care diagnostics. C1q and BVD assays used in the prior formats are transferred to this platform, to ascertain its usability as a cost effective, reliable sensor for diagnostic testing. We discuss the fabrication, characterisation and assay development, as well as their use in the benchtop hybrid system

Mobile Biosensorik auf Basis funktionalisierter, nanostrukturierter, optischer Wellenleiter

In dieser Arbeit wird ein kompakter Biosensor zur mobilen, markerfreien Detektion von mehreren Proteinen präsentiert. Ein photonischer Kristall, der mit Rezeptoren lokal funktionalisiert ist, dient hier als optischer Signalumwandler. Dafür wurden zwei Herstellungsprozesse zur Vervielfältigung von photonischen Kristallen und zwei Prozesse zur lokalen und kovalenten Anbindung von Rezeptoren an die Kristalloberfläche entwickelt. Zur Auslesung dieses photonischen Kristall-Sensors wurden verschiedene intensitätsbasierte Messsysteme in Form von zwei Smartphone-Adaptern und einem Kamera-basierten Messgerät evaluiert. Diese Messsysteme wandeln die Proteinanbindung an die Sensoroberfläche in ein Intensitätssignal um, über dessen Amplitude die Proteinkonzentration bestimmt werden kann. Mit dem Kamera-basierten Messgerät konnte die parallele und spezifische Anbindung der drei Proteine CD40 Ligand Antikörper (13.5 μg/ml), EGF Antikörper (13.5 μg/ml) und Streptavidin (30 μg/ml) anhand von sechs Rezeptorstellen nachgewiesen werden. In einem weiteren Experiment ist die detektierbare Konzentration des Proteins CD40 Ligand Antikörper auf 1,35 μg/ml reduziert worden. Um die Detektionsgrenze weiter zu verbessern, werden hier photonische Kristalle mit einer multi- und aperiodischen Gitterstruktur simulativ und experimentell untersucht.Zusätzlich wurde ein Testchip zur Filterung von Vollblut und für die bildgebende, markerfreie Detektion von mehreren Risikomarkern entworfen. Dieser beinhaltet Kapillarkanäle zum Transport des Blutes, eine Filtermembran und eine Sensorkammer, in der der photonische Kristall-Sensor eingeklebt wird. Die Eigenschaften des Testchips wurden evaluiert und die Assoziation von 500 nmol/l Biotin in Puffer an zwei Bindungsstellen und in Vollblut an einer Bindungsstelle kann im Intensitätssignal beobachtet werden. Abschließend wurden mono- und zweiperiodische Gitter in nanostruktierten Wellenleitern zur Steigerung des Fluoreszenzsignals für die Marker-basierte Biosensorik experimentell und theoretisch betrachtet.In this thesis a compact biosensor for mobile, label-free detection of multiple proteins is presented. A photonic crystal functionalized with specific receptors forms the optical transducer. Two fabrication processes to duplicate photonic crystals as well as two processes for coupling the receptors covalently and locally to the crystal surface are developed. Different intensity based measuring systems are evaluated in the form of two smartphone adapters and a camera-based measuring instrument to read-out the photonic crystal sensor. These measuring systems transform the binding kinetics of the protein into a detectable intensity signal, whose amplitudes can be used to determine protein concentration. With the compact, camera-based measuring instrument the parallel and specific association of the three proteins CD40 ligand antibody (13.5 μg/ml), EGF antibody (13.5 μg/ml) and streptavidin (30 μg/ml) could be observed on six binding positions. In a further experiment the detectable protein concentration is reduced down to 1.35 μg/ml for CD40 ligand antibody. To improve the limit of detection photonic crystals with multiperiodic and aperiodic grating structures are investigated in simulation and in experiment. Additionally, a test chip for human blood filtration and imaging label-free detection of multiple biomarkers is designed. The chip contains capillary channels for blood transportation, a filter membrane and a cavity open on one side for sensor bonding. The performance of the test chip is evaluated and the accociaten of 500 nmol/l biotin in buffer on two receptor positions and in human blood on one receptor position is observed in the intensity signal. Concluding monoperiodic and twoperiodic gratings in nanostructured waveguides are investigated in experiment and in simulation to enhance the fluorescence signal of labelled biosensors