Browsing by Subject "Microtoroid"

Now showing 1 - 4 of 4

Open Access
Design and development of novel large scale applications in micro/nanophotonics and nanobiotechnology
(2014) Özgür, Erol
Developments in micro/nanophotonics and nanobiotechnology creates new opportunities regarding development of devices with unprecedented capabilities, which could improve human civilization substantially. On the other hand, a certain level of maturity in transforming these possibilities into reality still requires considerable efforts. One of the main problems of these novel technologies is that their practical know-how is so scarce that they could only be utilized within strictly determined laboratory conditions, and by highly sophisticated scientists. This thesis focuses on large scale applications at the intersection of microphotonics and nanobiotechnology, and also in nanophotonics. On microphotonics side, optical microresonators with toroidal shape were successfully fabricated and optically integrated. Having an extremely high sensitivity towards perturbations in their environments, these microcavities could be used as biological sensors; however, they are also very sensitive for nonspecific interactions. Thus, a novel surface chemistry enabling bioconjugation of molecular probes without compromising their sensitivity and enhancing their selectivity was developed, based on methylphosphonate containing silane modification of the microtoroid surface. After this functionalization, microtoroids were used in biodetection in complex media. Also, a macroscopic photodetection device composed on intrinsically aligned semiconducting selenium nanowires were demonstrated. This device could be considered as a novel and efficient demonstration of nanowire integration to the macroscopic world. Together with the research on biosensors, these are important large scale applications of emergent science of our age.
Open Access
Label-free optical biodetection of pathogen virulence factors in complex media using microtoroids with multifunctional surface functionality
(American Chemical Society, 2018) Toren, P.; Ozgur E.; Bayındır, Mehmet
Early detection of pathogens or their virulence factors in complex media has a key role in early diagnosis and treatment of many diseases. Nanomolar and selective detection of Exotoxin A, which is a virulence factor secreted from Pseudomonas aeruginosa in the sputum of Cystic Fibrosis (CF) patients, can pave the way for early diagnosis of P. aeruginosa infections. In this study, we conducted a preliminary study to demonstrate the feasibility of optical biodetection of P. aeruginosa Exotoxin A in a diluted artificial sputum mimicking the CF respiratory environment. Our surface engineering approach provides an effective biointerface enabling highly selective detection of the Exotoxin A molecules in the complex media using monoclonal anti-Exotoxin A functionalized microtoroids. The highly resilient microtoroid surface toward other constituents of the sputum provides Exotoxin A detection ability in the complex media by reproducible measurements. In this study, the limit-of-detection of Exotoxin A in the complex media is calculated as 2.45 nM.
Open Access
Ultra high quality factor microtoroidal optical resonators in label - free biosensing applications with high sensitivity and selectivity
(2016-11) Tören, Pelin
Whispering - Gallery - Mode type microresonators provide great opportunities for label - free biosensing, allowing detections down to single - molecule levels. Microtoroids as optical resonators are quite sensitive and preferable biosensors due to their high quality factors. However, their surface design should be carefully considered for a selective biodetection. For this purpose, studies on WGM type biosensing for DNA, RNA and protein detections using various surface modifications are herein summarized. Over and above, this thesis mainly focuses on the microfabrication and surface modification of the microtoroids for various selective biosensing purposes such as antigen detection in complex media or detecting single base pair DNA alterations in buffer. With this regard, the developed microtoroid surface modification for dual characteristics (anti - fouling property and bioconjugability) is described in detail. The dual surface approach, used for selective Interleukin - 2 and Exotoxin - A detections in complex media, is applied to the microtoroids. Biosensing in complex media is a challeging task to perform unless the calibration approach is used. To overcome this challenge the suggested surface modification approach for nano - molar level detections is explained in detail. Besides, a novel surface modification approach for a selective single - stranded DNA detection based on discriminating single base pairs is portrayed as well.
Open Access
Ultrasensitive label-free microcavity biosensors with high selectivity
(IEEE, 2011) Özgür, Erol; Bayındır, Mehmet; Aktaş, Ozan
High quality factor whispering gallery mode microresonators have been recently shown to exhibit detection sensitivity of single molecule; however, the selectivity of these sensors among different types of analytes remains as an important issue, obscuring the broad applicability of optical microcavities. We demonstrate a surface modification strategy for fabrication of high selectivity and sensitivity microcavity biosensors in this study. © 2011 IEEE.