Name: label-free single molecule detection using microtoroid optical resonators
Uploaded: 2015-12-29T14:00:00.000+00:00
Duration: 8 min 53 s
Description: Watch this Scientific Journal Video about Label-free Single Molecule Detection Using Microtoroid Optical Resonators at JoVE.com

This research was supported in part by a National Research Service Award (T32GM07616) from the National Institute of General Medical Sciences.

1. Deneysel Kurulum ve Numune Hazırlama <ol><li> , Litografi kullanarak gravür ve daha önce 6 açıklanan prosedür erime microtoroids Üretiyor. Tipik olarak 80-100 um büyük bir çapa ve 2 um küçük bir çapa sahip olan, bir silikon göbek (çip) üzerinde microtoroids üretmektedirler. </li><li> Kabaca kendi fiber makaradan tek modlu fiber optik (125 mikron kaplama, 4.3 mikron mod alan çapı) bir metre gevşeyin. </li><li> Fiber optiğin çözülür bölümünün ortasında, tel şeritler kullanılarak optik elyafın yaklaşık polimer kaplama gibi küçük bir bölümünü (2.5 cm) şerit. Not: Bu microtoroid içine evanescently birkaç ışığa kullanılacak fiber optiğin kısmıdır. </li><li> Izopropanol alkol ve ücretsiz silin bir tüy bırakmayan soyulmuş lif temizleyin. </li><li> Tutucu mıknatıs yapılan bir lif tutucu kullanılarak yerinde lif bu bölümünü tutun. </li><li> Meltin tarafından ~ 500 nm İnce elimden lifg ve hidrojen meşale ve 60 mm / dak zıt yönlerde hareket eden iki step motorlar kullanılarak çekme. ~ 10 mm boyunda olmalıdır alev üst kısmı, iç fiber optik yerleştirin. Fiber boyunca transmisyon (kapalı fiber yanıp yanal olarak dağılmış ve ışık izleme) veya bir osiloskop bağlanmış bir foto diyot için elyafın bağlanması yoluyla görsel olarak izlenebilir olan dalgalı durduğunda lif çekme durdurma . </li><li> Fiber optik bir ucunu yarmak ve çıplak fiber adaptöre takın. Foto alıcı girişine içine lif bu ucunu yerleştirin. </li><li> Fiber çift fiber optik bağlayıcı kullanılarak lazer fiber makaranın diğer ucu. </li><li> Epoksi veya çift taraflı bant kullanarak bir numune tutucu üstüne microtoroid çip (paslanmaz çelik, 37.8 mm x 6,4 mm x 3,2 mm) yerleştirin. </li><li> (3 eksenli nano konumlandırma içeren bir konumlandırma kademesinin üzerine numune tutucuyu monte n3 eksenli mikrometre üstünde anocube) aşama (ekipman listesine bakınız). Titreşimleri en aza indirmek için bir pnömatik izole optik masa üzerindeki tüm deneyler. </li><li> Kaba pozisyon 3 eksenli mikrometre kullanarak örnek çip. </li><li> Nano-pozisyoner kullanarak optik fiber microtoroid içeren çip paralel hizaya getirin. Not: Giriş ışığı (~ 633 nm) bir dalga boyunun bir mesafede microtoroid hizalayın. Bu sürecin görselleştirme için iki görüntüleme sütunları kullanın üstünde ve çip tarafında konumlandırılmış (objektif lens ve kamera ile boru, ekipman listesine bakınız). </li><li> Bir in-line polarizasyon kontrolörü kullanarak optik fiber üzerinden yönlendirilen lazer ışığının polarizasyonu Optimize kutuplaşmayı ayarlamak için bir düğme ile (ekipman listesine bakınız). Not: fiber optik iletimi ölçülen dip dar göründüğünde Optimum polarizasyon elde edilir. Bir osiloskop (Daha fazla bilgi için adım 2.2) Bu dalış gözlemleyin. </li><li> Inşa etmekbir aralama olarak cam mikroskop lamı kullanılarak örnek sahne üzerinde bir cam lamel epoxying bir örnek odası. Not: Tüm kurulum kapsayan pleksiglas muhafaza hava akımları en aza indirmek için yararlı olabilir. Küçük bir açıklık boru kullanılarak pompalanan edilecek çözelti sağlamak için bırakılmalıdır. </li><li> Isı, bir RT su banyosunda (~ 500 mi) içinde ≥ 1 saat boyunca tanecik süspansiyonlar ya da tek-molekül sulu çözeltileri dengeye getirin. Not: Örnekler üreticiler, örneğin PBS veya HEPES belirtilen ilgili tamponlar kullanılarak mikrosantrifüj tüpleri içinde istenen konsantrasyona seyreltilir. Hiçbir bağlayıcı olay tespit edilirse, tampon tuz konsantrasyonu artırır. </li><li> ~ 2 sn çözümler (1 ml) kısaca içeren Vortex parçacık. </li><li> 1 ml numune bölmesine partikül içeren çözeltiler enjekte / 1 ml şırınga pompası kullanılarak Min. </li><li> Numune odası doldurdu sonra, şırınga pompası kapatın. </li><li> Kayıt verileri en aza indirmek için önce 30 saniye bekleyinölçümünü etkileyebilecek sıvı akışı kaynaklanan mekanik titreşimler etkileri. </li></ol> 2. Frekans Kilitleme <ol><li> Bağlama sıvısının enjeksiyonu nedeniyle rahatsız olacak çünkü, nanopositioner numune tutucu hareket ettirerek fiber optik için toroid-çift Re. </li><li> Dalga boyu çeşitli yoluyla bilgisayar kontrollü giriş lazer tarama microtoroid rezonans dalga boyu bulun. Lazerin dalga boyunu düzenleyen lazer denetleyicisi içinde piezoelektrik eleman bir üçgen dalga gerilim sinyali göndererek bu adımı gerçekleştirin. Bu dalga boyunda suyun ışık düşük emme olarak orada görünür ışığı (2.5 nm ± 635 nm) kullanarak deneyler yapın. </li><li> Oto-dengeli foto alıcı içine fiber optik çıkışını takarak fiber optik aracılığıyla ışık geçirgenliği ölçün. BNC kablosu kullanarak bir osiloskop içine foto alıcı çıkışını takın. O gözlemleyinn osiloskop microtoroid rezonans dalga boyunda optik fiber üzerinden iletim düşer. </li><li> Bir kablo ile geribildirim denetleyicisi (ekipman listesine bakınız) kilitleme frekansı ana girişine foto alıcı çıkışını takın. </li><li> 2 kHz titreşim frekansı ve 19 fm dalga boyu titreşim genliği ile kilitleme üstü tepe kullanarak kilitlenme modunda frekans kilitleme geribildirim denetleyicisi çalıştırın. Ampirik Ziegler-Nichols ayar kurallarını 14 kullanarak yazılım penceresindeki oransal-integral-türev ayarlarını. Not: Bu değerler tüm deneyler başında bir kez ayarlanması yeterlidir. </li><li> Microtoroid rezonans dalga boyuna lazerin dalga boyu otomatik kilitleyin. Numune odasını doldurduktan sonra bu adımı gerçekleştirin. Not: dalgaboyu kayması çok büyükse, o zaman geri denetleyici kilidi kaybedecek ve otomatik rezonans dalgaboyu yerini bulmak için tarama moduna. Bu ocDalga boyu Curs yaklaşık bir çizgi genişliği (araştırılan tüm sistemler için en az 600 fm) daha büyük kaydırır. </li><li> 24 bit veri toplama kartı kullanarak 20 kHz geribildirim denetleyicisi çıkışını kaydedin. Veri toplama yazılımı ile bir metin dosyası olarak veri verir. </li></ol> 3. Veri İşleme ve Analiz <ol><li> Fourier MATLAB&#39;da verileri dönüştürmek. </li><li> Düşük 2 kHz dayatılan taklidinin frekansını çıkarmak için 1 kHz bir kesim ile bir &quot;tuğla duvar&quot; filtre kullanarak veri geçmek (Yan Kod Screenshot 1 Dosya bakınız). </li><li> Hesaplama çentik 16 Hz pencere boyutunu kullanarak verileri süzmek. Not: Bu, bu durumda, gürültü bilinen kaynaklarını ortadan kaldırmak için yapılır, 60 Hz, elektronik hat gürültüsü ve harmonikleri, (lazer sürücüsünden gelen) yanı sıra, 100 Hz ve harmonik (Yan Kod Screenshot 1 Dosya bakınız). </li><li> Ters Fourier zaman alanına geri verileri dönüştürmek. </li><li> Medyan filtre penceresini kullanarak veri1001 örneklerin boyutu (Yan Kodu Screenshot 2 Dosya bakınız). </li><li> Kerssemakers ve ark., 15 adım bulma algoritması kullanılarak rezonans dalga adım değişiklikleri bulun. </li><li> Her bağlama aşamasında genliği histogramları oluşturun. </li><li> Denklem kullanarak parçacık boyutunu hesaplayın. (1) (Tartışma). </li></ol>

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The authors declare that they have no competing financial interests.

Bir parçacık bağlanan olarak, toroid artar rezonans dalgaboyu (λ). Bir parçacık keser ise, rezonans dalga boyu buna (a step-down olayı) azalır. Parçacık çapı (d), her dalga boyunda adım amplitüdü histogramları yoluyla belirlenebilir. Her dalga boyu basamağın yüksekliği bağlı parçacık büyüklüğü varyasyonları nedeniyle partikül bağlayan microtoroid üzerinde konumu nedeniyle değişir. Parçacıklar elektrik alan (E 0, max) maksimum olduğu mic...

Tek moleküllü saptama deneyleri Hastalığın erken teşhisi için biyosensörler kullanılan analit miktarının azaltılması için faydalıdır, ve moleküllerin 3 temel özelliklerini incelemek için. Bu tür deneyler, tipik olarak etiketler, bununla birlikte, etiketler her olay üzerinde çalışılan yapabilirliğini bozmakta ve bu, maliyet artışı, belirli bir protein için elde etmek mümkün değildir, ve özellikle de bünyesinde deneyleri veya nokta-of, gerçek süre, rahatsız edici olabilir kullanılarak gerçekleştirilir bakım teşhis. Etiket içermeyen biosensörleme şu anki altın standart Ancak, ticari yüzey plazmon rezonans sistemi tipik haliyle nM mertebesinde tespit tipik bir alt sınırı, yüzey plazmon rezonans 4&#39;tür. Son zamanlarda, optik rezonatörler etiket içermeyen tek bir molekül biodetection 5 için umut verici bir teknoloji olarak ortaya çıkmıştır. Uzun vadeli (ns) dayalı optik rezonatörler çalışma ışığı 6,7 hapsi. Işık evanescently olduğunutipik bir fiber optik aracılığıyla bu cihazların içine birleştiğinde. Fiber geçiyor ışığın dalga boyu rezonatör rezonans dalga boyu eşleştiği zaman, verimli rezonatör çiftler yanar. Bu birleştirilmiş ışık tamamen dahili rezonatörün çevresinin yakınında genliği azalan bir alan üreten rezonatörün en boşluk içinde yansıtır. Parçacıklar rezonatör, parçacığın 8 hacmi ile orantılı olarak rezonatör değişiklikleri rezonans dalgaboyu kaybolan alan ve bağlayıcılığı girerken. Algılama yeteneği açısından mikrosfer rezonatörler daha önce tek bir influenza A virüs partiküllerini (100 nm), 9,10 tespit etmek için kullanılmıştır. Son zamanlarda, plasmonically geliştirilmiş mikroküre optik rezonatörler Ancak bu yaklaşım de yüzde 0.3 um ila 2 tane çekim alanı sınırlar molekülleri 11 ve 8-mer oligonükleotitlerin 12 albumin, tek sığır serumu tespit etmek için kullanılmaktadıryardımcısı. Büyük çekim alanı biyosensörler parçacık algılama şansını maksimize etmek için idealdir. Büyük (&gt; 100 mikron 2) yakalama alanları ile Güncel çözüm tabanlı etiket içermeyen biyoalgı teknolojileri polistiren tanecikleri ≥ 25 nm tespit sınırlı kalmıştır. Bu çözelti içinde tek moleküllerin zamana bağımlı algılama kapasitesine sahip optik Whispering Evanescent Resonator (çiçek) 13 (Şekil 1) kilitleme Frekans olarak bilinen optik rezonatör teknolojisine dayalı bir etiket içermeyen biyo-algılayıcı sistemi geliştirmiştir. ÇİÇEK frekans kilitleme geri besleme kontrolü, dengeli algılama ve tek bir protein molekülleri aşağı küçük partikülleri tespit etmek için hesaplamalı filtreleme ile birlikte microtoroid optik rezonatörlerin uzun foton ömrünü kullanır. Frekans kilitleme kullanımı süpürüp veya lazer dalga boyu üzerinden tarama gerek kalmadan, parçacıklar bağlamak gibi sistem daima microtoroid kayması rezonans izlemenize olanak sağlarBüyük aralığındadır. Çiçeğin ilkeleri plasmonik geliştirilmesi de dahil olmak üzere diğer tekniklerin algılama yeteneklerini geliştirmek için kullanılabilir. Aşağıda, ÇİÇEK gerçekleştirmek için prosedürler açıklanmaktadır.

<table><tbody><tr><td>Tunable diode laser</td><td>Newport</td><td>TLB-6300</td><td></td></tr><tr><td>Laser controller</td><td>Newport</td><td>TLB-6300-LN</td><td></td></tr><tr><td>Frequency locking feedback controller</td><td>Toptica Photonics</td><td>Digilock 110</td><td></td></tr><tr><td>Auto-balanced photoreceiver</td><td>Newport</td><td>Model 2007</td><td></td></tr><tr><td>In-line polarization controller</td><td>General Photonics</td><td>PLC-003-S-90</td><td></td></tr><tr><td>24-bit data acquisition card</td><td>National Instruments</td><td>NI-PCI-4461</td><td></td></tr><tr><td>Recombinant human interleukin-2</td><td>Pierce Biotechnology</td><td>R201520</td><td></td></tr><tr><td>20 nm polystyrene beads</td><td>Thermo Scientific</td><td>3020A</td><td></td></tr><tr><td>NanoCube XYZ Piezo Stage</td><td>Physik Instrumente</td><td>P-611.3</td><td></td></tr><tr><td>Optical table</td><td>Newport</td><td>VH3660W-OPT</td><td></td></tr><tr><td>Objective lens for imaging column</td><td>Navitar Machine Vision</td><td>1-60228</td><td></td></tr><tr><td>Imaging column (adaptor tube)</td><td>Navitar Machine Vision</td><td>1-60228</td><td></td></tr><tr><td>High-Res CCD camera for imaging column</td><td>Edmund Industrial Optics</td><td>NT39244</td><td></td></tr></tbody></table>

label-free single molecule detection using microtoroid optical resonators

Aşağı tek bir molekül sınırına moleküllerinin küçük konsantrasyonlarını algılama gibi Hastalığın erken teşhisi ve moleküllerin davranışına temel çalışmaları gibi alanlarda bir etkiye sahiptir. Tek molekül algılama teknikleri yaygın, ancak etiket maliyeti ve karmaşıklığı artırmak, her zaman mevcut değildir ve olaylar çalışılan perturb böyle floresan etiket veya kuantum noktaları gibi etiketler kullanır. Optik rezonatörler ve etiket kullanılmaksızın tek moleküllerin tespit için umut verici bir araç olarak ortaya çıkmıştır. Şu anda çözelti içinde olmayan plasmonically geliştirilmiş çıplak optik rezonatör sistemi tarafından tespit edilen en küçük parçacık 25 nm polistiren küre 1&#39;dir. Biz Optik Whispering Evanescent Resonator sulu çözelti 2 etiket içermeyen tek bir molekül algılama bu sınırı aşmak ve elde edebilirsiniz (ÇİÇEK) Kilitleme Frekans olarak bilinen bir teknik geliştirdiler. Sinyal gücü partikül hacmi ile ölçekler gibi, bizim çalışma&gt; 100x improveme temsilnt sanatın mevcut durumu üzerinde gürültü oranı (SNR) sinyalde. İşte ÇİÇEK arkasında prosedürleri alanındaki kullanımını artırmak amacıyla sunulmuştur.

Olayları bağlayıcı Parçacık açıkça zaman (Şekil 2A) üzerinde microtoroid rezonans dalga adım gibi değişiklikler olarak görülmektedir. Bu adımların yükseklikleri. Şekil 2B&#39;de, bir histogram olarak gösterilen 2-4, sırasıyla Örnek eksozom bağlanma izleri (nanovesicles), 5 mil silika boncuklar ve tek bir insan interlökin-2 moleküllerinin Şekil edilir. Adım gibi olaylar parçacık boyutu ile ölçek gerçeği tekniği doğru ...

Watch this Scientific Journal Video about Label-free Single Molecule Detection Using Microtoroid Optical Resonators at JoVE.com

Label-free Single Molecule Detection Using Microtoroid Optical Resonators

We have developed a label-free biosensing system based on optical resonator technology known as Frequency Locking Optical Whispering Evanescent Resonator (FLOWER) that is capable of detecting single molecules in solution. Here the procedures behind this work are described and presented.

Microtoroid Optik Rezonatörler Kullanarak Etiket serbest Tek Molekül Algılama

Detecting small concentrations of molecules down to the single molecule limit has impact on areas such as early detection of disease, and fundamental ...

label-free-single-molecule-detection-using-microtoroid-optical

Research

JoVE Journal

Bioengineering

9.2K Görüntüleme.  California Institute of Technology. We have developed a label-free biosensing system based on optical resonator technology known as Frequency Locking Optical Whispering Evanescent Resonator (FLOWER) that is capable of detecting single molecules in solution. Here the procedures behind this work are described and presented. 

Video: Label-free Single Molecule Detection Using Microtoroid Optical Resonators

Fabrication of Silica Ultra High Quality Factor Microresonators

Whispering gallery resonant cavities confine light in circular orbits at their periphery.1-2 The photon storage lifetime in the cavity, quantified by the quality factor (Q) of the cavity, can be in excess of 500ns for cavities with Q factors above 100 million. As a result of their low material losses, silica microcavities have demonstrated some of the longest photon lifetimes to date1-2. Since a portion of the circulating light extends outside the resonator, these devices can also be used to probe the surroundings. This interaction has enabled numerous experiments in biology, such as single molecule biodetection and antibody-antigen kinetics, as well as discoveries in other fields, such as development of ultra-low-threshold microlasers, characterization of thin films, and cavity quantum electrodynamics studies.3-7
The two primary silica resonant cavity geometries are the microsphere and the microtoroid. Both devices rely on a carbon dioxide laser reflow step to achieve their ultra-high-Q factors (Q&gt;100 million).1-2,8-9 However, there are several notable differences between the two structures. Silica microspheres are free-standing, supported by a single optical fiber, whereas silica microtoroids can be fabricated on a silicon wafer in large arrays using a combination of lithography and etching steps. These differences influence which device is optimal for a given experiment.
Here, we present detailed fabrication protocols for both types of resonant cavities. While the fabrication of microsphere resonant cavities is fairly straightforward, the fabrication of microtoroid resonant cavities requires additional specialized equipment and facilities (cleanroom). Therefore, this additional requirement may also influence which device is selected for a given experiment.
Introduction
An optical resonator efficiently confines light at specific wavelengths, known as the resonant wavelengths of the device. 1-2 The common figure of merit for these optical resonators is the quality factor or Q. This term describes the photon lifetime (&tau;o) within the resonator, which is directly related to the resonator's optical losses. Therefore, an optical resonator with a high Q factor has low optical losses, long photon lifetimes, and very low photon decay rates (1/&tau;o). As a result of the long photon lifetimes, it is possible to build-up extremely large circulating optical field intensities in these devices. This very unique property has allowed these devices to be used as laser sources and integrated biosensors.10
A unique sub-class of resonators is the whispering gallery mode optical microcavity. In these devices, the light is confined in circular orbits at the periphery. Therefore, the field is not completely confined within the device, but evanesces into the environment. Whispering gallery mode optical cavities have demonstrated some of the highest quality factors of any optical resonant cavity to date.9,11 Therefore, these devices are used throughout science and engineering, including in fundamental physics studies and in telecommunications as well as in biodetection experiments. 3-7,12
Optical microcavities can be fabricated from a wide range of materials and in a wide variety of geometries. A few examples include silica and silicon microtoroids, silicon, silicon nitride, and silica microdisks, micropillars, and silica and polymer microrings.13-17 The range in quality factor (Q) varies as dramatically as the geometry. Although both geometry and high Q are important considerations in any field, in many applications, there is far greater leverage in boosting device performance through Q enhancement. Among the numerous options detailed previously, the silica microsphere and the silica microtoroid resonator have achieved some of the highest Q factors to date.1,9 Additionally, as a result of the extremely low optical loss of silica from the visible through the near-IR, both microspheres and microtoroids are able to maintain their Q factors over a wide range of testing wavelengths.18 Finally, because silica is inherently biocompatible, it is routinely used in biodetection experiments.
In addition to high material absorption, there are several other potential loss mechanisms, including surface roughness, radiation loss, and contamination loss.2 Through an optimization of the device size, it is possible to eliminate radiation losses, which arise from poor optical field confinement within the device. Similarly, by storing a device in an appropriately clean environment, contamination of the surface can be minimized. Therefore, in addition to material loss, surface scattering is the primary loss mechanism of concern.2,8
In silica devices, surface scattering is minimized by using a laser reflow technique, which melts the silica through surface tension induced reflow. While spherical optical resonators have been studied for many years, it is only with recent advances in fabrication technologies that researchers been able to fabricate high quality silica optical toroidal microresonators (Q&gt;100 million) on a silicon substrate, thus paving the way for integration with microfluidics.1
The present series of protocols details how to fabricate both silica microsphere and microtoroid resonant cavities. While silica microsphere resonant cavities are well-established, microtoroid resonant cavities were only recently invented.1 As many of the fundamental methods used to fabricate the microsphere are also used in the more complex microtoroid fabrication procedure, by including both in a single protocol it will enable researchers to more easily trouble-shoot their experiments.

We describe the use of a carbon dioxide laser reflow technique to fabricate silica resonant cavities, including free-standing microspheres and on-chip microtoroids. The reflow method removes surface imperfections, allowing long photon lifetimes within both devices. The resulting devices have ultra high quality factors, enabling applications ranging from telecommunications to biodetection.

Silika Ultra Yüksek Kalite Faktörü Microresonators Fabrikasyon

Whispering gallery resonant cavities confine light in circular orbits at their periphery.1-2 The photon storage lifetime in the cavity, quantified by the ...

Mühendislik

Optical Trapping of Nanoparticles

Optical trapping is a technique for immobilizing and manipulating small objects in a gentle way using light, and it has been widely applied in trapping and manipulating small biological particles. Ashkin and co-workers first demonstrated optical tweezers using a single focused beam1. The single beam trap can be described accurately using the perturbative gradient force formulation in the case of small Rayleigh regime particles1. In the perturbative regime, the optical power required for trapping a particle scales as the inverse fourth power of the particle size. High optical powers can damage dielectric particles and cause heating. For instance, trapped latex spheres of 109 nm in diameter were destroyed by a 15 mW beam in 25 sec1, which has serious implications for biological matter2,3.
A self-induced back-action (SIBA) optical trapping was proposed to trap 50 nm polystyrene spheres in the non-perturbative regime4. In a non-perturbative regime, even a small particle with little permittivity contrast to the background can influence significantly the ambient electromagnetic field and induce a large optical force. As a particle enters an illuminated aperture, light transmission increases dramatically because of dielectric loading. If the particle attempts to leave the aperture, decreased transmission causes a change in momentum outwards from the hole and, by Newton's Third Law, results in a force on the particle inwards into the hole, trapping the particle. The light transmission can be monitored; hence, the trap can become a sensor. The SIBA trapping technique can be further improved by using a double-nanohole structure.
The double-nanohole structure has been shown to give a strong local field enhancement5,6. Between the two sharp tips of the double-nanohole, a small particle can cause a large change in optical transmission, thereby inducing a large optical force. As a result, smaller nanoparticles can be trapped, such as 12 nm silicate spheres7 and 3.4 nm hydrodynamic radius bovine serum albumin proteins8. In this work, the experimental configuration used for nanoparticle trapping is outlined. First, we detail the assembly of the trapping setup which is based on a Thorlabs Optical Tweezer Kit. Next, we explain the nanofabrication procedure of the double-nanohole in a metal film, the fabrication of the microfluidic chamber and the sample preparation. Finally, we detail the data acquisition procedure and provide typical results for trapping 20 nm polystyrene nanospheres.

The following setup approach details low power optical trapping of dielectric nanoparticles using a double-nanohole in metal film.

Nanopartiküllerin Optik Yakalama

Optical trapping is a technique for immobilizing and manipulating small objects in a gentle way using light, and it has been widely applied in trapping ...

Synthesis and Operation of Fluorescent-core Microcavities for Refractometric Sensing

This paper discusses fluorescent core microcavity-based sensors that can operate in a microfluidic analysis setup. These structures are based on the formation of a fluorescent quantum-dot (QD) coating on the channel surface of a conventional microcapillary. Silicon QDs are especially attractive for this application, owing in part to their negligible toxicity compared to the II-VI and II-VI compound QDs, which are legislatively controlled substances in many countries. While the ensemble emission spectrum is broad and featureless, an Si-QD film on the channel wall of a capillary features a set of sharp, narrow peaks in the fluorescence spectrum, corresponding to the electromagnetic resonances for light trapped within the film. The peak wavelength of these resonances is sensitive to the external medium, thus permitting the device to function as a refractometric sensor in which the QDs never come into physical contact with the analyte. The experimental methods associated with the fabrication of the fluorescent-core microcapillaries are discussed in detail, as well as the analysis methods. Finally, a comparison is made between these structures and the more widely investigated liquid-core optical ring resonators, in terms of microfluidic sensing capabilities.

Fluorescent-core microcavity sensors employ a high-index quantum-dot coating in the channel of silica microcapillaries. Changes in the refractive index of fluids pumped into the capillary channel cause shifts in the microcavity fluorescence spectrum that can be used to analyze the channel medium.

Refraktometrik Algılama Floresan çekirdekli mikro kavitasyonlar sentezi ve İşletilmesi

This paper discusses  fluorescent core microcavity-based sensors that can operate in a microfluidic  analysis setup. These structures are based on the ...

Implementation of a Reference Interferometer for Nanodetection

A thermally and mechanically stabilized fiber interferometer suited for examining ultra-high quality factor microcavities is fashioned. After assessing its free spectral range (FSR), the module is put in parallel with a fiber taper-microcavity system and then calibrated through isolating and eliminating random shifts in the laser frequency (i.e. laser jitter noise). To realize the taper-microcavity junction and to maximize the optical power that is transferred to the resonator, a single-mode optical fiber waveguide is pulled. Solutions containing polystyrene nanobeads are then prepared and flown to the microcavity in order to demonstrate the system&#8217;s ability to sense binding to the surface of the microcavity. Data is post-processed via adaptive curve fitting, which allows for high-resolution measurements of the quality factor as well as the plotting of time-dependent parameters, such as resonant wavelength and split frequency shifts. By carefully inspecting steps in the time-domain response and shifting in the frequency-domain response, this instrument can quantify discrete binding events.

A reference interferometer technique, which is designed to remove undesirable laser jitter noise for nanodetection, is utilized for probing an ultra-high quality factor microcavity. Instructions for assembly, setup, and data acquisition are provided, alongside the measurement process for specifying the cavity quality factor.

Nanodetection için bir referans Interferometer Uygulanması

A thermally and mechanically stabilized fiber interferometer suited for examining ultra-high quality factor microcavities is fashioned. After assessing ...

Fabrication and Testing of Microfluidic Optomechanical Oscillators

Cavity optomechanics experiments that parametrically couple the phonon modes and photon modes have been investigated in various optical systems including microresonators. However, because of the increased acoustic radiative losses during direct liquid immersion of optomechanical devices, almost all published optomechanical experiments have been performed in solid phase. This paper discusses a recently introduced hollow microfluidic optomechanical resonator. Detailed methodology is provided to fabricate these ultra-high-Q microfluidic resonators, perform optomechanical testing, and measure radiation pressure-driven breathing mode and SBS-driven whispering gallery mode parametric vibrations. By confining liquids inside the capillary resonator, high mechanical- and optical- quality factors are simultaneously maintained.

Parametric optomechanical excitations have recently been experimentally demonstrated in microfluidic optomechanical resonators by means of optical radiation pressure and stimulated Brillouin scattering. This paper describes the fabrication of these microfluidic resonators along with methodologies for generating and verifying optomechanical oscillations.

Fabrikasyon ve mikroakışkan optomechanical Osilatörler Testi

Cavity optomechanics experiments that parametrically couple the phonon modes and photon modes have been investigated in various optical systems including ...

Attaching Biological Probes to Silica Optical Biosensors Using Silane Coupling Agents

In order to interface with biological environments, biosensor platforms, such as the popular Biacore system (based on the Surface Plasmon Resonance (SPR) technique), make use of various surface modification techniques, that can, for example, prevent surface fouling, tune the hydrophobicity / hydrophilicity of the surface, adapt to a variety of electronic environments, and most frequently, induce specificity towards a target of interest.1-5 These techniques extend the functionality of otherwise highly sensitive biosensors to real-world applications in complex environments, such as blood, urine, and wastewater analysis.2,6-7 While commercial biosensing platforms, such as Biacore, have well-understood, standard techniques for performing such surface modifications, these techniques have not been translated in a standardized fashion to other label-free biosensing platforms, such as Whispering Gallery Mode (WGM) optical resonators.8-9
WGM optical resonators represent a promising technology for performing label-free detection of a wide variety of species at ultra-low concentrations.6,10-12 The high sensitivity of these platforms is a result of their unique geometric optics: WGM optical resonators confine circulating light at specific, integral resonance frequencies.13 Like the SPR platforms, the optical field is not totally confined to the sensor device, but evanesces; this "evanescent tail" can then interact with species in the surrounding environment. This interaction causes the effective refractive index of the optical field to change, resulting in a slight, but detectable, shift in the resonance frequency of the device. Because the optical field circulates, it can interact many times with the environment, resulting in an inherent amplification of the signal, and very high sensitivities to minor changes in the environment.2,14-15
To perform targeted detection in complex environments, these platforms must be paired with a probe molecule (usually one half of a binding pair, e.g. antibodies / antigens) through surface modification.2 Although WGM optical resonators can be fabricated in several geometries from a variety of material systems, the silica microsphere is the most common. These microspheres are generally fabricated on the end of an optical fiber, which provides a "stem" by which the microspheres can be handled during functionalization and detection experiments. Silica surface chemistries may be applied to attach probe molecules to their surfaces; however, traditional techniques generated for planar substrates are often not adequate for these three-dimensional structures, as any changes to the surface of the microspheres (dust, contamination, surface defects, and uneven coatings) can have severe, negative consequences on their detection capabilities. Here, we demonstrate a facile approach for the surface functionalization of silica microsphere WGM optical resonators using silane coupling agents to bridge the inorganic surface and the biological environment, by attaching biotin to the silica surface.8,16 Although we use silica microsphere WGM resonators as the sensor system in this report, the protocols are general and can be used to functionalize the surface of any silica device with biotin.

Biosensors interface with complex, biological environments and perform targeted detection by combining highly sensitive sensors with highly specific probes attached to the sensor via surface modification. Here, we demonstrate the surface functionalization of silica optical sensors with biotin using silane coupling agents to bridge the sensor and the biological environment.

Silan Kaplin Ajanlar kullanarak Silika Optik Biyosensörler için Biyolojik Probları takılması

In order to interface with biological environments, biosensor platforms, such as the popular Biacore system (based on the Surface Plasmon Resonance (SPR) ...

Biyomühendislik

Fabrication and Operation of a Nano-Optical Conveyor Belt

The technique of using focused laser beams to trap and exert forces on small particles has enabled many pivotal discoveries in the nanoscale biological and physical sciences over the past few decades. The progress made in this field invites further study of even smaller systems and at a larger scale, with tools that could be distributed more easily and made more widely available. Unfortunately, the fundamental laws of diffraction limit the minimum size of the focal spot of a laser beam, which makes particles smaller than a half-wavelength in diameter hard to trap and generally prevents an operator from discriminating between particles which are closer together than one half-wavelength. This precludes the optical manipulation of many closely-spaced nanoparticles and&#160;limits the&#160;resolution of optical-mechanical systems. Furthermore, manipulation using focused beams requires beam-forming or steering optics, which can be very bulky and expensive. To address these limitations in the system scalability of conventional optical trapping our lab has devised an alternative technique which utilizes near-field optics to move particles across a chip. Instead of focusing laser beams in the far-field, the optical near field of plasmonic resonators produces the necessary local optical intensity enhancement to overcome the restrictions of diffraction and manipulate particles at higher resolution. Closely-spaced resonators produce strong optical traps which can be addressed to mediate the hand-off of particles from one to the next in a conveyor-belt-like fashion. Here, we describe how to design and produce a conveyor belt using a gold surface patterned with plasmonic C-shaped resonators and how to operate it with polarized laser light to achieve super-resolution nanoparticle manipulation and transport. The nano-optical conveyor belt chip can be produced using lithography techniques and easily packaged and distributed.

The scalability and resolution of conventional optical manipulation techniques are limited by diffraction. We circumvent the diffraction limit and describe a method of optically transporting nanoparticles across a chip using a gold surface patterned with a path of closely spaced C-shaped plasmonic resonators.

Bir Nano-Optik Konveyör Bant imalatı ve İşletilmesi

The technique of using focused laser beams to trap and exert forces on small particles has enabled many pivotal discoveries in the nanoscale biological ...

Multicolor Fluorescence Detection for Droplet Microfluidics Using Optical Fibers

Fluorescence assays are the most common readouts used in droplet microfluidics due to their bright signals and fast time response. Applications such as multiplex assays, enzyme evolution, and molecular biology enhanced cell sorting require the detection of two or more colors of fluorescence. Standard multicolor detection systems that couple free space lasers to epifluorescence microscopes are bulky, expensive, and difficult to maintain. In this paper, we describe a scheme to perform multicolor detection by exciting discrete regions of a microfluidic channel with lasers coupled to optical fibers. Emitted light is collected by an optical fiber coupled to a single photodetector. Because the excitation occurs at different spatial locations, the identity of emitted light can be encoded as a temporal shift, eliminating the need for more complicated light filtering schemes. The system has been used to detect droplet populations containing four unique combinations of dyes and to detect sub-nanomolar concentrations of fluorescein.

Multicolor fluorescence detection in droplet microfluidics typically involves bulky and complex epifluorescence microscope-based detection systems. Here we describe a compact and modular multicolor detection scheme that utilizes an array of optical fibers to temporally encode multicolor data collected by a single photodetector.

Damlacık Mikroakiskan için renkli Floresan Algılama Optik Elyaf kullanma

Fluorescence assays are the most common readouts used in droplet microfluidics due to their bright signals and fast time response. Applications such as ...

Use of Dual Optical Tweezers and Microfluidics for Single-Molecule Studies

Visual biochemistry is a powerful technique for observing the stochastic properties of single enzymes or enzyme complexes that are obscured in the averaging that takes place in bulk-phase studies. To achieve visualization, dual optical tweezers, where one trap is fixed and the other is mobile, are focused into one channel of a multi-stream microfluidic chamber positioned on the stage of an inverted fluorescence microscope. The optical tweezers trap single molecules of fluorescently labeled DNA and fluid flow through the chamber and past the trapped beads, stretches the DNA to B-form (under minimal force, i.e., 0 pN) with the nucleic acid being observed as a white string against a black background. DNA molecules are moved from one stream to the next, by translating the stage perpendicular to the flow to enable the initiation of reactions in a controlled manner. To achieve success, microfluidic devices with optically clear channels are mated to glass syringes held in place in a syringe pump. Optimal results use connectors permanently bonded to the flow cell, tubing that is mechanically rigid and chemically resistant, and which is connected to switching valves that eliminate bubbles that prohibit laminar flow.

Visual, single-molecule biochemistry studied through microfluidic chambers is greatly facilitated using glass barrel, gas-tight syringes, stable connections of tubing to flow cells, and elimination of bubbles by placing switching valves between the syringes and tubing. The protocol describes dual optical traps that enable visualization of DNA transactions and intermolecular interactions.

Tek Moleküllü Çalışmalarda Çift Optik Cımbız ve Mikroakışkan Kullanımı

Visual biochemistry is a powerful technique for observing the stochastic properties of single enzymes or enzyme complexes that are obscured in the ...

Biyokimya

Optical Biosensing

Optical biosensors utilize light to detect the binding of a target molecule. These sensors can utilize a label molecule, which produces a measurable signal such as fluorescence,&#160;or these sensors can be label-free&#160;and use the changes in optical properties, such as refractive index, to sense for the binding of the target molecule. This video introduces both label and label-free optical biosensors, demonstrates their use in the laboratory, and shows some applications of the technology.

Types of Optical Biosensing; Surface Plasmon Resonance SPR

Optical biosensors utilize light to detect the binding of a target molecule. These sensors can utilize a label molecule, which produces a measurable signal such as fluorescence, or these sensors can be label-free&#160;and use the changes in optical properties, such as refractive index, to sense for the binding of the target molecule. This video introduces both label and label-free optical biosensors, demonstrates their use in the laboratory, and shows some applications of the technology.

Optical biosensors utilize light to detect the binding of a target molecule. These sensors can utilize a label molecule, which produces a measurable ...