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Articles by Heather K. Hunt in JoVE
JoVE Bioengineering
הוספת בדיקות ביולוגיות Biosensors סיליקה אופטי באמצעות סוכני צימוד silane
Department of Biological Engineering, University of Missouri
Biosensors ממשק עם סביבות מורכבות ביולוגיות ולבצע איתור ממוקד על ידי שילוב של חיישנים רגישים מאוד עם בדיקות ספציפיות ביותר המחוברים חיישן באמצעות שינוי פני השטח. הנה, אנחנו מדגימים functionalization פני השטח של חיישנים אופטיים עם סיליקה ביוטין באמצעות סוכני צימוד silane לגשר על חיישן את הסביבה הביולוגית.
Other articles by Heather K. Hunt on PubMed
Label-free Biological and Chemical Sensors
Highly sensitive, label-free biodetection methods have applications in both the fundamental research and healthcare diagnostics arenas. Therefore, the development of new transduction methods and the improvement of the existing methods will significantly impact these areas. A brief overview of the different types of biosensors and the critical parameters governing their performance will be given. Additionally, a more in-depth discussion of optical devices, surface functionalization methods to increase device specificity, and fluidic techniques to improve sample delivery will be reviewed.
Bioconjugation Strategies for Microtoroidal Optical Resonators
The development of label-free biosensors with high sensitivity and specificity is of significant interest for medical diagnostics and environmental monitoring, where rapid and real-time detection of antigens, bacteria, viruses, etc., is necessary. Optical resonant devices, which have very high sensitivity resulting from their low optical loss, are uniquely suited to sensing applications. However, previous research efforts in this area have focused on the development of the sensor itself. While device sensitivity is an important feature of a sensor, specificity is an equally, if not more, important performance parameter. Therefore, it is crucial to develop a covalent surface functionalization process, which also maintains the device's sensing capabilities or optical qualities. Here, we demonstrate a facile method to impart specificity to optical microcavities, without adversely impacting their optical performance. In this approach, we selectively functionalize the surface of the silica microtoroids with biotin, using amine-terminated silane coupling agents as linkers. The surface chemistry of these devices is demonstrated using X-ray photoelectron spectroscopy, and fluorescent and optical microscopy. The quality factors of the surface functionalized devices are also characterized to determine the impact of the chemistry methods on the device sensitivity. The resulting devices show uniform surface coverage, with no microstructural damage. This work represents one of the first examples of non-physisorption-based bioconjugation of microtoroidal optical resonators.
Recycling Microcavity Optical Biosensors
Optical biosensors have tremendous potential for commercial applications in medical diagnostics, environmental monitoring, and food safety evaluation. In these applications, sensor reuse is desirable to reduce costs. To achieve this, harsh, wet chemistry treatments are required to remove surface chemistry from the sensor, typically resulting in reduced sensor performance and increased noise due to recognition moiety and optical transducer degradation. In the present work, we suggest an alternative, dry-chemistry method, based on O2 plasma treatment. This approach is compatible with typical fabrication of substrate-based optical transducers. This treatment completely removes the recognition moiety, allowing the transducer surface to be refreshed with new recognition elements and thus enabling the sensor to be recycled.
Determination of Binding Kinetics Using Whispering Gallery Mode Microcavities
Silica optical microcavity sensors show great promise in the kinetic evaluation of binding pairs, fundamental in understanding biomolecular interactions. Here, we develop and demonstrate a novel platform, based on bioconjugated silica microsphere resonators, to study the binding kinetics of the biotin-streptavidin system. We characterize the optical performance, verify the covalent attachment of biotin to the surface, and perform streptavidin detection experiments. We perform preliminary kinetic analysis of the detection data which shows the potential of whispering gallery mode resonators in the determination of the dissociation constant of the binding pair, which is in good agreement with previously published values.
Thermo-optic Coefficient of Polyisobutylene Ultrathin Films Measured with Integrated Photonic Devices
The optical properties of polymeric materials, such as transmission loss and the thermo-optic coefficient, determine their utility in numerous applications, ranging from nanotechnology to the automotive and aerospace industries. However, because of the wide variation in the physical properties of polymers, many are unsuited for characterization using conventional techniques; consequently, their optical properties are unknown. One such polymer is polyisobutylene, which is viscous at room temperature and therefore is not compatible with conventional transmission loss and the thermo-optic coefficient characterization techniques because they rely on contact measurements. To overcome this, we have developed an integrated, microscale optical sensor that relies on an evanescent wave to study the material's optical behavior. Using this device, we successfully determined the refractive index, the transmission loss, and the thermo-optic coefficient of ultrathin films of polyisobutylene. The films are deposited on the sensor's silica surface using either spin coating or surface-initiated cationic polymerization, demonstrating the flexibility of this approach.
Selective Patterning of Si-based Biosensor Surfaces Using Isotropic Silicon Etchants
Ultra-sensitive, label-free biosensors have the potential to have a tremendous impact on fields like medical diagnostics. For the majority of these Si-based integrated devices, it is necessary to functionalize the surface with a targeting ligand in order to perform specific biodetection. To do this, silane coupling agents are commonly used to immobilize the targeting ligand. However, this method typically results in the bioconjugation of the entire device surface, which is undesirable. To compensate for this effect, researchers have developed complex blocking strategies that result in selective patterning of the sensor surface. Recently, silane coupling agents were used to attach biomolecules to the surface of silica toroidal biosensors integrated on a silicon wafer. Interestingly, only the silica biosensor surface was conjugated. Here, we hypothesize why this selective patterning occurred. Specifically, the silicon etchant (xenon difluoride), which is used in the fabrication of the biosensor, appears to reduce the efficiency of the silane coupling attachment to the underlying silicon wafer. These results will enable future researchers to more easily control the bioconjugation of their sensor surfaces, thus improving biosensor device performance.
