1
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Hao S, Suebka S, Su J. Single 5-nm quantum dot detection via microtoroid optical resonator photothermal microscopy. LIGHT, SCIENCE & APPLICATIONS 2024; 13:195. [PMID: 39160151 DOI: 10.1038/s41377-024-01536-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2024] [Revised: 07/10/2024] [Accepted: 07/16/2024] [Indexed: 08/21/2024]
Abstract
Label-free detection techniques for single particles and molecules play an important role in basic science, disease diagnostics, and nanomaterial investigations. While fluorescence-based methods are tools for single molecule detection and imaging, they are limited by available molecular probes and photoblinking and photobleaching. Photothermal microscopy has emerged as a label-free imaging technique capable of detecting individual nanoabsorbers with high sensitivity. Whispering gallery mode (WGM) microresonators can confine light in a small volume for enhanced light-matter interaction and thus are a promising ultra-sensitive photothermal microscopy platform. Previously, microtoroid optical resonators were combined with photothermal microscopy to detect 250 nm long gold nanorods and 100 nm long polymers. Here, we combine microtoroids with photothermal microscopy to spatially detect single 5 nm diameter quantum dots (QDs) with a signal-to-noise ratio exceeding 104. Photothermal images were generated by point-by-point scanning of the pump laser. Single particle detection was confirmed for 18 nm QDs by high sensitivity fluorescence imaging and for 5 nm QDs via comparison with theory. Our system demonstrates the capability to detect a minimum heat dissipation of 0.75 pW. To achieve this, we integrated our microtoroid based photothermal microscopy setup with a low amplitude modulated pump laser and utilized the proportional-integral-derivative controller output as the photothermal signal source to reduce noise and enhance signal stability. The heat dissipation of these QDs is below that from single dye molecules. We anticipate that our work will have application in a wide variety of fields, including the biological sciences, nanotechnology, materials science, chemistry, and medicine.
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Affiliation(s)
- Shuang Hao
- Wyant College of Optical Sciences, University of Arizona, Tucson, AZ, 85721, USA
| | - Sartanee Suebka
- Wyant College of Optical Sciences, University of Arizona, Tucson, AZ, 85721, USA
| | - Judith Su
- Wyant College of Optical Sciences and Department of Biomedical Engineering, University of Arizona, Tucson, AZ, 85721, USA.
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2
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Gin A, Nguyen PD, Serrano G, Alexander G, Su J. Towards Early Diagnosis and Screening of Alzheimer's Disease Using Frequency Locked Whispering Gallery Mode Microtoroid Biosensors. RESEARCH SQUARE 2024:rs.3.rs-4355995. [PMID: 38798660 PMCID: PMC11118682 DOI: 10.21203/rs.3.rs-4355995/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2024]
Abstract
Alzheimer's disease (AD) is a progressive form of dementia affecting almost 55 million people worldwide. It is characterized by the abnormal deposition of amyloid plaques and neurofibrillary tangles within the brain, leading to a pathological cascade of neuron degeneration and death as well as memory loss and cognitive decline. Amyloid beta (Aβ) is an AD biomarker present in cerebrospinal fluid and blood serum and correlates with the presence of amyloid plaques and tau tangles in the brain. Measuring the levels of Aβ can help with early diagnosis of AD, which is key for studying novel AD drugs and delaying the symptoms of dementia. However, this goal is difficult to achieve due to the low levels of AD biomarkers in biofluids. Here we demonstrate for the first time the use of FLOWER (frequency locked optical whispering evanescent resonator) for quantifying the levels of post-mortem cerebrospinal fluid (CSF) Aβ42 in clinicopathologically classified control, mild cognitive impairment (MCI), and AD participants. FLOWER is capable of measuring CSF Aβ42 (area under curve, AUC = 0.92) with higher diagnostic performance than standard ELISA (AUC = 0.82) and was also able to distinguish between control and MCI samples. Our results demonstrate the capability of FLOWER for screening CSF samples for early diagnosis of Alzheimer's pathology.
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3
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Suebka S, McLeod E, Su J. Ultra-high-Q free-space coupling to microtoroid resonators. LIGHT, SCIENCE & APPLICATIONS 2024; 13:75. [PMID: 38490984 PMCID: PMC10942989 DOI: 10.1038/s41377-024-01418-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2023] [Revised: 02/20/2024] [Accepted: 02/28/2024] [Indexed: 03/18/2024]
Abstract
Whispering gallery mode (WGM) microtoroid resonators are one of the most sensitive biochemical sensors in existence, capable of detecting single molecules. The main barrier for translating these devices out of the laboratory is that light is evanescently coupled into these devices though a tapered optical fiber. This hinders translation of these devices as the taper is fragile, suffers from mechanical vibration, and requires precise positioning. Here, we eliminate the need for an optical fiber by coupling light into and out from a toroid via free-space coupling and monitoring the scattered resonant light. A single long working distance objective lens combined with a digital micromirror device (DMD) was used for light injection, scattered light collection, and imaging. We obtain Q-factors as high as 1.6 × 10 8 with this approach. Electromagnetically induced transparency (EIT)-like and Fano resonances were observed in a single cavity due to indirect coupling in free space. This enables improved sensing sensitivity. The large effective coupling area (~10 μm in diameter for numerical aperture = 0.14) removes the need for precise positioning. Sensing performance was verified by combining the system with the frequency locked whispering evanescent resonator (FLOWER) approach to perform temperature sensing experiments. A thermal nonlinear optical effect was examined by tracking the resonance through FLOWER while adjusting the input power. We believe that this work will be a foundation for expanding the implementation of WGM microtoroid resonators to real-world applications.
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Affiliation(s)
- Sartanee Suebka
- Wyant College of Optical Sciences, University of Arizona, Tucson, AZ, USA
| | - Euan McLeod
- Wyant College of Optical Sciences, University of Arizona, Tucson, AZ, USA
| | - Judith Su
- Wyant College of Optical Sciences, University of Arizona, Tucson, AZ, USA.
- Department of Biomedical Engineering, University of Arizona, Tucson, AZ, USA.
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4
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Guan B, Kok TW, Riesen N, Lancaster D, Suu K, Priest C. Microsphere-Enabled Micropillar Array for Whispering Gallery Mode Virus Detection. ACS APPLIED MATERIALS & INTERFACES 2024; 16:12042-12051. [PMID: 38382003 DOI: 10.1021/acsami.3c17751] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/23/2024]
Abstract
Rapid detection of pathogens and analytes at the point of care offers an opportunity for prompt patient management and public health control. This paper reports an open microfluidic platform coupled with active whispering gallery mode (WGM) microsphere resonators for the rapid detection of influenza viruses. The WGM microsphere resonators, precoated with influenza A polyclonal antibodies, are mechanically trapped in the open micropillar array, where the evaporation-driven flow continuously transports a small volume (∼μL) of sample to the resonators without auxiliaries. Selective chemical modification of the pillar array changes surface wettability and flow pattern, which enhances the detection sensitivity of the WGM resonator-based virus sensor. The optofluidic sensing platform is able to specifically detect influenza A viruses within 15 min using a few microliters of sample and displays a linear response to different virus concentrations.
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Affiliation(s)
- Bin Guan
- Future Industries Institute, STEM, University of South Australia, Mawson Lakes, SA 5095, Australia
- ARC Research Hub for Integrated Devices for End-User Analysis at Low-Levels (IDEAL), University of South Australia, Mawson Lakes, SA 5095, Australia
| | - Tuck-Weng Kok
- Adelaide Medical School & School of Biological Sciences, University of Adelaide, Adelaide, SA 5005, Australia
| | - Nicolas Riesen
- Future Industries Institute, STEM, University of South Australia, Mawson Lakes, SA 5095, Australia
- ARC Research Hub for Integrated Devices for End-User Analysis at Low-Levels (IDEAL), University of South Australia, Mawson Lakes, SA 5095, Australia
| | - David Lancaster
- Future Industries Institute, STEM, University of South Australia, Mawson Lakes, SA 5095, Australia
- ARC Research Hub for Integrated Devices for End-User Analysis at Low-Levels (IDEAL), University of South Australia, Mawson Lakes, SA 5095, Australia
| | - Koukou Suu
- ULVAC Inc., Chigasaki, Kanagawa 253-8543, Japan
| | - Craig Priest
- Future Industries Institute, STEM, University of South Australia, Mawson Lakes, SA 5095, Australia
- ARC Research Hub for Integrated Devices for End-User Analysis at Low-Levels (IDEAL), University of South Australia, Mawson Lakes, SA 5095, Australia
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5
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Kim SK, Suebka S, Gin A, Nguyen PD, Tang Y, Su J, Goddard WA. Methotrexate Inhibits the Binding of the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Receptor Binding Domain to the Host-Cell Angiotensin-Converting Enzyme-2 (ACE-2) Receptor. ACS Pharmacol Transl Sci 2024; 7:348-362. [PMID: 38357278 PMCID: PMC10863433 DOI: 10.1021/acsptsci.3c00197] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Revised: 12/21/2023] [Accepted: 12/29/2023] [Indexed: 02/16/2024]
Abstract
As the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus mutates, finding effective drugs becomes more challenging. In this study, we use ultrasensitive frequency locked microtoroid optical resonators in combination with in silico screening to search for COVID-19 drugs that can stop the virus from attaching to the human angiotensin-converting enzyme 2 (hACE2) receptor in the lungs. We found 29 promising candidates that could block the binding site and selected four of them that were likely to bind very strongly. We tested three of these candidates using frequency locked optical whispering evanescent resonator (FLOWER), a label-free sensing method based on microtoroid resonators. FLOWER has previously been used for sensing single macromolecules. Here we show, for the first time, that FLOWER can provide accurate binding affinities and sense the inhibition effect of small molecule drug candidates without labels, which can be prohibitive in drug discovery. One of the candidates, methotrexate, showed binding to the spike protein 1.8 million times greater than that to the receptor binding domain (RBD) binding to hACE2, making it difficult for the virus to enter cells. We tested methotrexate against different variants of the SARS-CoV-2 virus and found that it is effective against all four of the tested variants. People taking methotrexate for other conditions have also shown protection against the original SARS-CoV-2 virus. Normally, it is assumed that methotrexate inhibits the replication and release of the virus. However, our findings suggest that it may also block the virus from entering cells. These studies additionally demonstrate the possibility of extracting candidate ligands from large databases, followed by direct receptor-ligand binding experiments on the best candidates using microtoroid resonators, thus creating a workflow that enables the rapid discovery of new drug candidates for a variety of applications.
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Affiliation(s)
- Soo-Kyung Kim
- Materials
and Process Simulation Center, California
Institute of Technology, Pasadena, California 91125, United States
| | - Sartanee Suebka
- Wyant
College of Optical Sciences, The University
of Arizona, Tucson, Arizona 85721, United States
| | - Adley Gin
- Wyant
College of Optical Sciences, The University
of Arizona, Tucson, Arizona 85721, United States
- Department
of Biomedical Engineering, The University
of Arizona, Tucson, Arizona 85721, United States
| | - Phuong-Diem Nguyen
- Department
of Biomedical Engineering, The University
of Arizona, Tucson, Arizona 85721, United States
| | - Yisha Tang
- Department
of Biomedical Engineering, The University
of Arizona, Tucson, Arizona 85721, United States
| | - Judith Su
- Wyant
College of Optical Sciences, The University
of Arizona, Tucson, Arizona 85721, United States
| | - William A. Goddard
- Materials
and Process Simulation Center, California
Institute of Technology, Pasadena, California 91125, United States
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6
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Xu Y, Stanko AM, Cerione CS, Lohrey TD, McLeod E, Stoltz BM, Su J. Low Part-Per-Trillion, Humidity Resistant Detection of Nitric Oxide Using Microtoroid Optical Resonators. ACS APPLIED MATERIALS & INTERFACES 2024; 16:5120-5128. [PMID: 38240231 DOI: 10.1021/acsami.3c16012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2024]
Abstract
The nitric oxide radical plays pivotal roles in physiological as well as atmospheric contexts. Although the detection of dissolved nitric oxide in vivo has been widely explored, highly sensitive (i.e., low part-per-trillion level), selective, and humidity-resistant detection of gaseous nitric oxide in air remains challenging. In the field, humidity can have dramatic effects on the accuracy and selectivity of gas sensors, confounding data, and leading to overestimation of gas concentration. Highly selective and humidity-resistant gaseous NO sensors based on laser-induced graphene were recently reported, displaying a limit of detection (LOD) of 8.3 ppb. Although highly sensitive (LOD = 590 ppq) single-wall carbon nanotube NO sensors have been reported, these sensors lack selectivity and humidity resistance. In this report, we disclose a highly sensitive (LOD = 2.34 ppt), selective, and humidity-resistant nitric oxide sensor based on a whispering-gallery mode microtoroid optical resonator. Excellent analyte selectivity was enabled via novel ferrocene-containing polymeric coatings synthesized via reversible addition-fragmentation chain-transfer polymerization. Utilizing a frequency locked optical whispering evanescent resonator system, the microtoroid's real-time resonance frequency shift response to nitric oxide was tracked with subfemtometer resolution. The lowest concentration experimentally detected was 6.4 ppt, which is the lowest reported to date. Additionally, the performance of the sensor remained consistent across different humidity environments. Lastly, the impact of the chemical composition and molecular weight of the novel ferrocene-containing polymeric coatings on sensing performance was evaluated. We anticipate that our results will have impact on a wide variety of fields where NO sensing is important such as medical diagnostics through exhaled breath, determination of planetary habitability, climate change, air quality monitoring, and treating cardiovascular and neurological disorders.
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Affiliation(s)
- Yinchao Xu
- Wyant College of Optical Sciences, The University of Arizona, Tucson, Arizona 85721, United States
- Department of Biomedical Engineering, The University of Arizona, Tucson, Arizona 85721, United States
| | - Allison M Stanko
- The Warren and Catherine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Chloe S Cerione
- The Warren and Catherine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Trevor D Lohrey
- The Warren and Catherine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Euan McLeod
- Wyant College of Optical Sciences, The University of Arizona, Tucson, Arizona 85721, United States
- Department of Biomedical Engineering, The University of Arizona, Tucson, Arizona 85721, United States
| | - Brian M Stoltz
- The Warren and Catherine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Judith Su
- Wyant College of Optical Sciences, The University of Arizona, Tucson, Arizona 85721, United States
- Department of Biomedical Engineering, The University of Arizona, Tucson, Arizona 85721, United States
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7
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Gin A, Nguyen PD, Melzer JE, Li C, Strzelinski H, Liggett SB, Su J. Label-free, real-time monitoring of membrane binding events at zeptomolar concentrations using frequency-locked optical microresonators. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.20.558657. [PMID: 37786702 PMCID: PMC10541581 DOI: 10.1101/2023.09.20.558657] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/04/2023]
Abstract
Binding events to elements of the cell membrane act as receptors which regulate cellular function and communication and are the targets of many small molecule drug discovery efforts for agonists and antagonists. Conventional techniques to probe these interactions generally require labels and large amounts of receptor to achieve satisfactory sensitivity. Whispering gallery mode microtoroid optical resonators have demonstrated sensitivity to detect single-molecule binding events. Here, we demonstrate the use of frequency-locked optical microtoroids for characterization of membrane interactions in vitro at zeptomolar concentrations using a supported biomimetic membrane. Arrays of microtoroids were produced using photolithography and subsequently modified with a biomimetic membrane, providing high quality (Q) factors (> 10 6 ) in aqueous environments. Fluorescent recovery after photobleaching (FRAP) experiments confirmed the retained fluidity of the microtoroid supported-lipid membrane with a diffusion coefficient of 3.38 ± 0.26 μm 2 ⋅ s - 1 . Utilizing this frequency-locked membrane-on-a-chip model combined with auto-balanced detection and non-linear post-processing techniques, we demonstrate zeptomolar detection levels The binding of Cholera Toxin B- monosialotetrahexosyl ganglioside (GM1) was monitored in real-time, with an apparent equilibrium dissociation constant k d = 1.53 nM . The measured affiny of the agonist dynorphin A 1-13 to the κ -opioid receptor revealed a k d = 3.1 nM using the same approach. Radioligand binding competition with dynorphin A 1-13 revealed a k d in agreement (1.1 nM) with the unlabeled method. The biosensing platform reported herein provides a highly sensitive real-time characterization of membrane embedded protein binding kinetics, that is rapid and label-free, for toxin screening and drug discovery, among other applications.
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Affiliation(s)
- Adley Gin
- Wyant College of Optical Sciences, The University of Arizona, Tucson, AZ 85721
| | - Phuong-Diem Nguyen
- Department of Biomedical Engineering, The University of Arizona, Tucson, AZ 85721
| | - Jeffrey E. Melzer
- Wyant College of Optical Sciences, The University of Arizona, Tucson, AZ 85721
| | - Cheng Li
- Wyant College of Optical Sciences, The University of Arizona, Tucson, AZ 85721
| | - Hannah Strzelinski
- Department of Medicine, University of South Florida Morsani College of Medicine, Tampa, FL 33612
| | - Stephen B. Liggett
- Department of Medicine, University of South Florida Morsani College of Medicine, Tampa, FL 33612
| | - Judith Su
- Wyant College of Optical Sciences, The University of Arizona, Tucson, AZ 85721
- Department of Biomedical Engineering, The University of Arizona, Tucson, AZ 85721
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8
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Luu GT, Ge C, Tang Y, Li K, Cologna SM, Godwin AK, Burdette JE, Su J, Sanchez LM. An Integrated Approach to Protein Discovery and Detection From Complex Biofluids. Mol Cell Proteomics 2023; 22:100590. [PMID: 37301378 PMCID: PMC10388710 DOI: 10.1016/j.mcpro.2023.100590] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 05/22/2023] [Accepted: 06/07/2023] [Indexed: 06/12/2023] Open
Abstract
Ovarian cancer, a leading cause of cancer-related deaths among women, has been notoriously difficult to screen for and diagnose early, as early detection significantly improves survival. Researchers and clinicians seek routinely usable and noninvasive screening methods; however, available methods (i.e., biomarker screening) lack desirable sensitivity/specificity. The most fatal form, high-grade serous ovarian cancer, often originate in the fallopian tube; therefore, sampling from the vaginal environment provides more proximal sources for tumor detection. To address these shortcomings and leverage proximal sampling, we developed an untargeted mass spectrometry microprotein profiling method and identified cystatin A, which was validated in an animal model. To overcome the limits of detection inherent to mass spectrometry, we demonstrated that cystatin A is present at 100 pM concentrations using a label-free microtoroid resonator and translated our workflow to patient-derived clinical samples, highlighting the potential utility of early stage detection where biomarker levels would be low.
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Affiliation(s)
- Gordon T Luu
- Department of Chemistry and Biochemistry, University of California Santa Cruz, Santa Cruz, California, USA
| | - Chang Ge
- Wyant College of Optical Sciences, University of Arizona, Tucson, Arizona, USA
| | - Yisha Tang
- Department of Biomedical Engineering, University of Arizona, Tucson, Arizona, USA
| | - Kailiang Li
- Department of Pharmaceutical Sciences, University of Illinois at Chicago, Chicago, Illinois, USA
| | - Stephanie M Cologna
- Department of Chemistry, University of Illinois at Chicago, Chicago, Illinois, USA
| | - Andrew K Godwin
- Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, Kansas City, Kansas, USA; Kansas Institute for Precision Medicine, University of Kansas Medical Center, Kansas City, Kansas, USA; The University of Kansas Cancer Center, Kansas City, Kansas, USA
| | - Joanna E Burdette
- Department of Pharmaceutical Sciences, University of Illinois at Chicago, Chicago, Illinois, USA
| | - Judith Su
- Wyant College of Optical Sciences, University of Arizona, Tucson, Arizona, USA; Department of Biomedical Engineering, University of Arizona, Tucson, Arizona, USA.
| | - Laura M Sanchez
- Department of Chemistry and Biochemistry, University of California Santa Cruz, Santa Cruz, California, USA.
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9
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Holler S, Speck M. Spatial Multiplexing of Whispering Gallery Mode Sensors. SENSORS (BASEL, SWITZERLAND) 2023; 23:5925. [PMID: 37447776 DOI: 10.3390/s23135925] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Revised: 06/13/2023] [Accepted: 06/23/2023] [Indexed: 07/15/2023]
Abstract
Whispering gallery mode resonators have proven to be robust and sensitive platforms for the trace detection of chemical and/or biological analytes. Conventional approaches using serially addressed resonators face challenges in simultaneous multi-channel (i.e., multi-species) detection. We present an alternative monitoring scheme that allows for the spatial multiplexing of whispering gallery mode resonators with the simultaneous observation of the resonance spectra from each of them. By imaging arrays of microspheres and monitoring the glare spot intensities through image processing routines, resonance spectra from multiple resonators may be simultaneously recorded without interference or confounding effects of serial excitation/detection. We demonstrate our multiplexed imaging approach with bulk refractive index variations and virus-antibody binding.
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Affiliation(s)
- Stephen Holler
- Department of Physics and Engineering Physics, Fordham University, Bronx, NY 10458, USA
| | - Matthew Speck
- Department of Physics and Engineering Physics, Fordham University, Bronx, NY 10458, USA
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10
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Choi G, Su J. Impact of stimulated Raman scattering on dark soliton generation in a silica microresonator. JPHYS PHOTONICS 2023; 5:014001. [PMID: 36698962 PMCID: PMC9855653 DOI: 10.1088/2515-7647/aca8e1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Revised: 11/17/2022] [Accepted: 12/05/2022] [Indexed: 05/09/2023] Open
Abstract
Generating a coherent optical frequency comb at an arbitrary wavelength is important for fields such as precision spectroscopy and optical communications. Dark solitons which are coherent states of optical frequency combs in normal dispersion microresonators can extend the operating wavelength range of these combs. While the existence and dynamics of dark solitons has been examined extensively, requirements for the modal interaction for accessing the soliton state in the presence of a strong Raman interaction at near visible wavelengths has been less explored. Here, analysis on the parametric and Raman gain in a silica microresonator is performed, revealing that four-wave mixing parametric gain which can be created by a modal-interaction-aided additional frequency shift is able to exceed the Raman gain. The existence range of the dark soliton is analyzed as a function of pump power and detuning for given modal coupling conditions. We anticipate these results will benefit fields requiring optical frequency combs with high efficiency and selectable wavelength such as biosensing applications using silica microcavities that have a strong Raman gain in the normal dispersion regime.
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Affiliation(s)
- Gwangho Choi
- Wyant College of Optical Sciences, The University of Arizona, Tucson, AZ 85721, United States of America
| | - Judith Su
- Wyant College of Optical Sciences, The University of Arizona, Tucson, AZ 85721, United States of America
- Department of Biomedical Engineering, The University of Arizona, Tucson, AZ 85721, United States of America
- Author to whom any correspondence should be addressed
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11
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Li C, Lohrey T, Nguyen PD, Min Z, Tang Y, Ge C, Sercel ZP, McLeod E, Stoltz BM, Su J. Part-per-Trillion Trace Selective Gas Detection Using Frequency Locked Whispering-Gallery Mode Microtoroids. ACS APPLIED MATERIALS & INTERFACES 2022; 14:42430-42440. [PMID: 36049126 DOI: 10.1021/acsami.2c11494] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Rapid detection of toxic and hazardous gases at trace concentrations plays a vital role in industrial, battlefield, and laboratory scenarios. Of interest are both sensitive as well as highly selective sensors. Whispering-gallery mode (WGM) microresonator-based biochemical sensors are among the most sensitive sensors in existence due to their long photon confinement times. One main concern with these devices, however, is their selectivity toward specific classes of target analytes. Here, we employ frequency locked WGM microtoroid optical resonators covalently modified with various polymer coatings to selectively detect the chemical warfare agent surrogate diisopropyl methylphosphonate (DIMP) as well as the toxic industrial chemicals formaldehyde and ammonia at parts-per-trillion concentrations (304, 434, and 117 ppt, respectively). This is 1-2 orders of magnitude better than previously reported, depending on the target, except for pristine graphene and pristine carbon nanotube sensors, which demonstrate similar detection levels but in vacuum and without selectivity. Selective polymer coatings include polyethylene glycol for DIMP sensing, accessed by the modification of commercially available materials, and 3-(triethoxysilyl) propyl-terminated polyvinyl acetate (PVAc) for ammonia sensing. Notably, we developed for the first time an efficient one-pot procedure to access 3-(triethoxysilyl) propyl-terminated PVAc that utilizes cobalt-mediated living radical polymerization and a nitroxyl polymer-terminating agent. Alkaline hydrolysis of PVAc coatings to form polyvinyl alcohol coatings directly bound to the microtoroid proved to be reliable and reproducible, leading to WGM sensors capable of the rapid and selective detection of formaldehyde vapors. The selectivity of these three polymer coatings as sensing media was predicted, in part, based on their functional group content and known reactivity patterns with the target analytes. Furthermore, we demonstrate that microtoroids coated with a mixture of polymers can serve as an all-in-one sensor that can detect multiple agents. We anticipate that our results will facilitate rapid early detection of chemical agents, as well as their surrogates and precursors.
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Affiliation(s)
- Cheng Li
- Wyant College of Optical Sciences, The University of Arizona, 1630 E University Blvd, Tucson, Arizona85721, United States
| | - Trevor Lohrey
- The Warren and Katherine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California91125, United States
| | - Phuong-Diem Nguyen
- Department of Biomedical Engineering, The University of Arizona, 1630 E University Blvd, Tucson, Arizona85721, United States
| | - Zhouyang Min
- Department of Biomedical Engineering, The University of Arizona, 1630 E University Blvd, Tucson, Arizona85721, United States
| | - Yisha Tang
- Department of Biomedical Engineering, The University of Arizona, 1630 E University Blvd, Tucson, Arizona85721, United States
| | - Chang Ge
- Wyant College of Optical Sciences, The University of Arizona, 1630 E University Blvd, Tucson, Arizona85721, United States
| | - Zachary P Sercel
- The Warren and Katherine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California91125, United States
| | - Euan McLeod
- Wyant College of Optical Sciences, The University of Arizona, 1630 E University Blvd, Tucson, Arizona85721, United States
| | - Brian M Stoltz
- The Warren and Katherine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California91125, United States
| | - Judith Su
- Wyant College of Optical Sciences, The University of Arizona, 1630 E University Blvd, Tucson, Arizona85721, United States
- Department of Biomedical Engineering, The University of Arizona, 1630 E University Blvd, Tucson, Arizona85721, United States
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12
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Choi G, Gin A, Su J. Optical frequency combs in aqueous and air environments at visible to near-IR wavelengths. OPTICS EXPRESS 2022; 30:8690-8699. [PMID: 35299315 PMCID: PMC8970704 DOI: 10.1364/oe.451631] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2021] [Revised: 02/16/2022] [Accepted: 02/21/2022] [Indexed: 05/24/2023]
Abstract
The ability to detect and identify molecules at high sensitivity without the use of labels or capture agents is important for medical diagnostics, threat identification, environmental monitoring, and basic science. Microtoroid optical resonators, when combined with noise reduction techniques, have been shown capable of label-free single molecule detection; however, they still require a capture agent and prior knowledge of the target molecule. Optical frequency combs can potentially provide high precision spectroscopic information on molecules within the evanescent field of the microresonator; however, this has not yet been demonstrated in air or aqueous biological sensing. For aqueous solutions in particular, impediments include coupling and thermal instabilities, reduced Q factor, and changes to the mode spectrum. Here we overcome a key challenge toward single-molecule spectroscopy using optical microresonators: the generation of a frequency comb at visible to near-IR wavelengths when immersed in either air or aqueous solution. The required dispersion is achieved via intermodal coupling, which we show is attainable using larger microtoroids, but with the same shape and material that has previously been shown ideal for ultra-high sensitivity biosensing. We believe that the continuous evolution of this platform will allow us in the future to simultaneously detect and identify single molecules in both gas and liquid at any wavelength without the use of labels.
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Affiliation(s)
- Gwangho Choi
- College of Optical Sciences, University of Arizona, Tucson, Arizona 85721, USA
| | - Adley Gin
- College of Optical Sciences, University of Arizona, Tucson, Arizona 85721, USA
| | - Judith Su
- College of Optical Sciences, University of Arizona, Tucson, Arizona 85721, USA
- Department of Biomedical Engineering, University of Arizona, Tucson, Arizona 85721, USA
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Rajendran B, Chen X, Li Z, Zhan Z, Goh KB. How molecular interactions tune the characteristic time of nanocomposite colloidal sensors. J Colloid Interface Sci 2022; 616:668-678. [PMID: 35245793 DOI: 10.1016/j.jcis.2022.02.100] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2022] [Revised: 02/18/2022] [Accepted: 02/21/2022] [Indexed: 12/19/2022]
Abstract
HYPOTHESIS Mass transport critically controls the performance of colloidal metal-polymer sensors. We hypothesize that molecular-level pair interactions, such as electric, steric, and specific binding effects, govern the mass transport and, in return, the characteristic time of these sensors. THEORY Here we present a simple theory guided by experimental data to examine the sensing performance of two usually encountered archetypal metal-polymer sensors, namely (1) core-shell and (2) yolk-shell architectures. For this purpose, we use the static reactive density functional theory framework, determining how (i) charge, (ii) size, and (iii) non-covalent binding factors modulate the characteristic time. FINDINGS We show how an interplay between diffusivity and partitioning governs the sensing time of the sensors, where an anti-correlation cancellation between them renders the time non-trivial. Our study demonstrates that the convoluted substrate-hydrogel shell interaction controls the characteristic time of these colloidal sensors, especially when the sensors are in a collapsed state. Notably, the substrates with a high dipole moment tend to equilibrate greatly, but undesirably, at the shell-solution interface. With this, we encourage the formation of a metastable sorption state.
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Affiliation(s)
- Barathan Rajendran
- School of Engineering, Monash University Malaysia, Bandar Sunway, Selangor, Malaysia
| | - Xiao Chen
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798, Republic of Singapore
| | - Zhong Li
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798, Republic of Singapore; Center for Cellular and Molecular Engineering, Department of Orthopaedic Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
| | - Zhixin Zhan
- School of Aeronautic Science and Engineering, Beihang University, Beijing 100191, China
| | - K B Goh
- School of Engineering, Monash University Malaysia, Bandar Sunway, Selangor, Malaysia.
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Single-molecule optofluidic microsensor with interface whispering gallery modes. Proc Natl Acad Sci U S A 2022; 119:2108678119. [PMID: 35115398 PMCID: PMC8832994 DOI: 10.1073/pnas.2108678119] [Citation(s) in RCA: 31] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/23/2021] [Indexed: 12/23/2022] Open
Abstract
Optical microresonators have emerged as promising platforms for label-free detection of molecules. However, approaching optimum sensitivity is hindered due to the weak tail of evanescent fields. Here, we report the implementation of the interface modes for ultrasensitive sensing in a microbubble resonator. With the electromagnetic field peaked at the interface between the optical resonator and the analyte solution, interface modes enable sensing of biomolecules with a detection limit of 0.3 pg/cm2. Single-molecule detection is further demonstrated using the plasmonic-enhanced interface modes. In addition, intrinsically integrated into a microfluidic channel, the sensor exhibits ultrasmall sample consumption down to 10 pL, providing an automatic platform for biomedical analysis. Label-free sensors are highly desirable for biological analysis and early-stage disease diagnosis. Optical evanescent sensors have shown extraordinary ability in label-free detection, but their potentials have not been fully exploited because of the weak evanescent field tails at the sensing surfaces. Here, we report an ultrasensitive optofluidic biosensor with interface whispering gallery modes in a microbubble cavity. The interface modes feature both the peak of electromagnetic-field intensity at the sensing surface and high-Q factors even in a small-sized cavity, enabling a detection limit as low as 0.3 pg/cm2. The sample consumption can be pushed down to 10 pL due to the intrinsically integrated microfluidic channel. Furthermore, detection of single DNA with 8 kDa molecular weight is realized by the plasmonic-enhanced interface mode.
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