{"id":31,"date":"2016-01-21T00:35:07","date_gmt":"2016-01-21T00:35:07","guid":{"rendered":"https:\/\/live-optics-wp.pantheonsite.io\/jsu\/?page_id=31"},"modified":"2025-10-07T17:31:30","modified_gmt":"2025-10-07T17:31:30","slug":"research","status":"publish","type":"page","link":"https:\/\/wp.optics.arizona.edu\/jsu\/research\/","title":{"rendered":"Research"},"content":{"rendered":"
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Detecting molecules at extremely low concentrations is essential for advancing basic science, developing earlier and more accurate medical diagnostics, and protecting the environment. Our lab develops optical sensing technologies to meet these challenges, with the goal of revealing signals invisible to conventional methods.<\/p>\n

At the core of this effort is FLOWER<\/strong> (Frequency Locked Optical Whispering Evanescent Resonator), a sensing platform built on whispering gallery mode (WGM) resonators<\/strong>, most often implemented as microtoroids (Figure 1). FLOWER keeps the resonator synchronized with the laser. When a molecule binds, the resonator\u2019s frequency changes, and the laser controller must adjust its voltage to keep up. By measuring these tiny voltage changes, FLOWER can detect single molecules with extraordinary sensitivity.<\/p>\n

With this approach, FLOWER achieves label-free, ultra-sensitive detection<\/strong> at the single-molecule level — capable of identifying proteins as small as 15.4 kDa<\/strong> without the need for fluorescent or chemical labels. Crucially, FLOWER is not limited to purified solutions; it maintains high sensitivity in complex biological samples<\/strong> such as serum and urine, making it well suited for both biomedical diagnostics<\/strong> and real-world environmental monitoring<\/strong>.<\/p>\n

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(a)\"Fig8<\/div>\n
\u00a0Figure 1.\u00a0 (a) Microtoroid optical resonator (b) FLOWER: Frequency Locked Optical Whispering Evanescent Resonator<\/em><\/div>\n
Key references:<\/h5>\n

Suebka, S., Gin, A.,\u00a0Su, Judith<\/strong>, Frequency Locked Whispering Evanescent Resonator (FLOWER) for biochemical sensing applications<\/a>,\u00a0Nature Protocols<\/em> (2025) https:\/\/doi.org\/10.1038\/s41596-024-01096-7 (se<\/strong>lected by Nature Protocols<\/em> as the journal\u2019s Protocol of the Week)<\/strong><\/p>\n

Gin, A., Nguyen, P-D., Melzer, J., Li, C., Strzelinski, H., Liggett, S.B.,\u00a0Su, Judith<\/strong>,\u00a0Label-free, real-time monitoring of membrane binding events at zeptomolar concentrations using frequency-locked optical microresonators<\/a>,\u00a0Nature Communications<\/em>,\u00a015<\/strong>, 7445 (2024).<\/p>\n

Gin, A., Nguyen, P-D., Serrano, G., Alexander, G,\u00a0Su, Judith<\/strong>,\u00a0Towards Early Diagnosis and Screening of Alzheimer\u2019s Disease Using Frequency Locked Whispering Gallery Mode Microtoroid Biosensors<\/a>,\u00a0npj Biosensing<\/em>,\u00a01<\/strong>, 9 (2024).\u00a0(Editorially highlighted with a homepage hero image on the npj Biosensing<\/em> website)<\/strong><\/p>\n

Su, Judith<\/strong>, Goldberg. A.F, Stoltz, B.M. \u201cLabel-free single detection of single nanoparticles and biological molecules using microtoroid optical resonators<\/a>,\u201d Light: Science and Applications<\/em>, 5<\/strong>, e16001 (2016). (Winner of a best paper award from Light: Science & Applications<\/em>\u00a0<\/em><\/strong>)<\/p>\n

Suebka, S., Nguyen, P-D, Gin, A, and\u00a0Su, Judith<\/strong>,\u00a0How fast it can stick: visualizing flow delivery to microtoroid biosensors<\/a>,\u00a0ACS Sensors<\/em>,\u00a07<\/span>, 2700\u20132708,\u00a0<\/span>(2021), (supplementary cover)<\/strong><\/p>\n

Hao, S. and\u00a0Su, Judith<\/strong>,\u00a0Noise-induced limits of detection in frequency locked optical microcavities<\/a>,\u00a0Journal of Lightwave Technology,<\/em>\u00a038(22), 6393\u00a0\u2013 6401 (2020).<\/p>\n

United States Patent Numbers 9,737,770 and 10,309,960<\/p>\n

Basic science<\/h3>\n

Our lab is interested in utilizing the high sensitivity and quick response time of our devices to study the basics of pain, olfaction, and taste.<\/p>\n

Key references:<\/h5>\n

Yang, M-Y^<\/sup>, Mac, Khuong D.M^<\/sup>,\u00a0 Strzelinski, Hannah R., Hoffman, S.A., Kim, D., Kim, S-K,\u00a0Su, Judith<\/strong>,* Liggett, S.B.*, III Goddard, W.A,* Agonist activation opening the Ga subunit of the GPCR\u2013GProtein precoupled complex defines functional agonist activation of TAS2R5 GPCR<\/a>,\u00a0Proceedings of the National Academy of Sciences<\/em>\u00a0(PNAS<\/em>),<\/em> 121<\/strong>, e2409987121 (2024),\u00a0^<\/sup>co-first author, * co-corresponding author.<\/p>\n

Hao, S., Guthrie, B., Kim, S-K, Kubicek, J., Murtaza, B., Khan, N.A., Khakbaz, P. ,\u00a0Su, Judith*<\/strong>, III Goddard, WA*,\u00a0Steviol rebaudiosides bind to four different sites of the human sweet taste receptor (T1R2\/T1R3) complex explaining confusing experiments<\/a>,\u00a0Communications Chemistry,\u00a0<\/em>7<\/strong>, 236 (2024), co-corresponding author<\/p>\n

Translational medicine<\/h3>\n

We have used FLOWER to successfully sense low concentrations of exosome (~ 40 nm nanovesicle) cancer biomarkers in mouse serum (Figure 2). \u00a0In these experiments, female mice (n = 5) born on the same day were implanted with Daudi (human Burkitt\u2019s lymphoma) tumor cells for 5 weeks. \u00a0One microliter of serum from each mouse each week was diluted a million-fold in 0.9% saline and sequentially flowed over a microtoroid covalently functionalized with anti-CD81, an exosome-specific marker. \u00a0A close inspection of a binding curve (Figure 4) shows discrete changes, or steps, in the resonance wavelength (\u03bb) of the microtoroid as individual exosomes bind to the surface of the microtoroid.<\/p>\n

\"mouse5_fit2\"<\/h4>\n

Figure 2. <\/em>Exosome binding curves. Mice were implanted with human Burkitt\u2019s lymphoma tumor cells, and each week blood serum samples were taken and later analyzed all together using FLOWER. The curves shown here are from a single mouse. For each week we see an increase in the response from the sensor corresponding to increasing exosome levels. No significant signal was obtained from week 0. The data traces are fit with a simple exponential (dashed red line) corresponding to first-order kinetics.<\/em><\/p>\n

Key references:<\/h5>\n

Hao, S.,\u00a0Su, Judith<\/strong>,\u00a0Whispering gallery mode optical resonators for biological and chemical detection: current practices, future perspectives, and challenges<\/a>,\u00a0Reports on Progress in Physics<\/em>, 88<\/b> 016402, (2025).<\/p>\n

Gin, A., Nguyen, P-D., Serrano, G., Alexander, G,\u00a0Su, Judith<\/strong>,\u00a0Towards Early Diagnosis and Screening of Alzheimer\u2019s Disease Using Frequency Locked Whispering Gallery Mode Microtoroid Biosensors<\/a>,\u00a0npj Biosensing<\/em>,\u00a01<\/strong>, 9 (2024). (Editorially highlighted with a homepage hero image on the npj Biosensing<\/em> website)<\/strong><\/p>\n

Kim, S-K, Suebka S., Gin A., Nguyen, P-D., Tang Y.,\u00a0Su, Judith*<\/strong>, III Goddard, WA*,\u00a0Methotrexate 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<\/a>,\u00a0ACS Pharmacology & Translational Science,\u00a0<\/em>7<\/span><\/strong>,\u00a0<\/span><\/em>2<\/span>,\u00a0<\/span><\/em>348\u2013362<\/span>\u00a0(2024), *co-corresponding author (supplementary cover)<\/strong><\/p>\n

Luu, G., Ge., C., Tang, Y., Li, K., Cologna, S., Burdette, J.,\u00a0Su, Judith*<\/strong>, and Sanchez, L.*,\u00a0An integrated approach to protein discovery and detection from complex biofluids<\/a>, *co-corresponding author,\u00a0Molecular & Cellular Proteomics,\u00a0<\/em>2023<\/p>\n

Dell\u2019Olio, F.,\u00a0Su, Judith<\/strong>, Huser, T., Sottile, V., Alix-Panabi\u00e8res, C.\u00a0 Photonic technologies for liquid biopsies: recent advances and open research challenges<\/a>,\u00a0Laser & Photonics Reviews<\/em>, 15, 2170012 (2021) (back cover)<\/strong>.<\/p>\n

Su, Judith<\/strong>, Label-free single exosome detection using frequency locked microtoroid optical resonators<\/a>, ACS Photonics<\/em> 2<\/strong>, 1241\u20131245 (2015).<\/p>\n

Environmental monitoring<\/h3>\n

FLOWER has demonstrated part-per-trillion detection of toxic industrial chemicals and chemical warfare agent surrogates and precursors. This work is funded by the Defense Threat Reduction Agency (DTRA).<\/p>\n

Key references:<\/h5>\n

Xu, Y, Stanko, A, Cerione, C, Lohrey, T, McLeod, E., Stoltz, B.,\u00a0Su, Judith,<\/strong>\u00a0Low part-per-trillion, humidity resistant detection of nitric oxide using microtoroid optical resonators<\/a>\u00a0,\u00a0ACS Applied Materials & Interfaces,\u00a0<\/em>1<\/span>6<\/span><\/strong>,\u00a0<\/span><\/em>4<\/span>,\u00a0<\/span><\/em>5120<\/span>\u2013<\/span><\/em>5128\u00a0<\/span>(2024)<\/p>\n

Li, C., Lohrey, T.D., Nguyen, P-D., Min, Z., Tang, Y., Ge, C., Sercel, Z.P., McLeod, E., Stoltz, B.M.,\u00a0Su, Judith,<\/strong>\u00a0Part-per-trillion trace selective gas detection using frequency locked whispering gallery mode microtoroids<\/a>,\u00a0ACS Applied Materials & Interfaces,\u00a0<\/em>1<\/span>4<\/span><\/strong>,\u00a0<\/span><\/em>37<\/span>,\u00a0<\/span><\/em>42430\u201342440 (2022)\u00a0<\/span>(supplementary cover)<\/strong>.<\/p>\n

Next generation sensing platforms<\/h3>\n

We work on building our next generation sensing platforms, this includes adding spectroscopic capabilities to our devices as well as working on ways to boost the sensitivity of our sensors.<\/p>\n

Key references:<\/h5>\n

Hao, S, Suebka, S.,\u00a0Su, Judith,\u00a0<\/strong>Single 5-nm quantum dot detection via microtoroid optical resonator photothermal microscopy<\/a>\u00a0Light: Science & Applications<\/em>,\u00a013<\/strong>, 195 (2024). (featured in\u00a0Optics & Photonics News Y<\/em>ear in Optics 2025 which highlights the the most exciting optics research to emerge in the preceding 12 months<\/strong>)<\/strong><\/p>\n

Choi, G. and\u00a0Su, Judith<\/strong>,\u00a0Impact of stimulated Raman scattering on dark soliton generation in a silica microresonator<\/a>,\u00a0J. Phys. Photonics<\/em>,\u00a05<\/strong>, 014001 (2023) (special issue on Emerging Leaders 2023)<\/strong>.<\/p>\n

Choi, G., Gin., A., and\u00a0Su, Judith<\/strong>,\u00a0Optical<\/span>\u00a0frequency combs in aqueous and air environments at visible to near-IR wavelengths,<\/a>\u00a0Optics Express,\u00a0<\/em>3<\/b>0<\/b>, 8690-8699 (2022)<\/p>\n

Li, C., Chen, L., McLeod, E.,\u00a0Su, Judith<\/strong>, \u201cDark mode plasmonic optical microcavity biochemical sensor<\/a>,\u201d\u00a0Photonics Research,\u00a0<\/em>7<\/strong>(8), 939-947(2019).<\/p>\n

Nguyen, P-D., Zhang, X.,\u00a0Su, Judith<\/strong>,\u00a0One-step controlled synthesis of size-tunable toroidal gold particles for biochemical sensing<\/a>,\u00a0ACS Applied Nano Materials,\u00a0<\/em>2<\/strong>(<\/span>12)<\/span>,\u00a0<\/span><\/em>7839-7847\u00a0<\/span>(2019).<\/p>\n

Portable, point-of-care, ultra-sensitive biosensors<\/h3>\n

In collaboration with the McLeod Laboratory<\/a>, we are working to miniaturize these sensors, making them easily translatable to other labs and clinics.<\/p>\n

Key references:<\/h5>\n

Suebka, S, McLeod, E.,\u00a0Su, Judith<\/strong>,\u00a0Ultra-high-Q free space coupling to microtoroid resonators,<\/a>\u00a0Light: Science & Applications<\/em>,\u00a013<\/strong>, 75 (2024)\u00a0(Most downloaded paper, May 2024)<\/strong><\/p>\n

Chen, L., Li, C., Liu, Y.,\u00a0Su, Judith*<\/strong>, McLeod, E.* \u201cSimulating robust far-field coupling to traveling waves in large three-dimensional nanostructured high-Q microresonators<\/a>,\u201d\u00a0Photonics Research<\/em>,\u00a07<\/strong>\u00a0(9), 967-976 (2019), *co-corresponding author<\/p>\n","protected":false},"excerpt":{"rendered":"

Detecting molecules at extremely low concentrations is essential for advancing basic science, developing earlier and more accurate medical diagnostics, and protecting the environment. Our lab develops optical sensing technologies to meet these challenges, with the goal of revealing signals invisible to conventional methods. At the core of this effort is FLOWER (Frequency Locked Optical Whispering Evanescent Resonator), a sensing platform<\/p>\n","protected":false},"author":36,"featured_media":0,"parent":0,"menu_order":2,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-31","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/wp.optics.arizona.edu\/jsu\/wp-json\/wp\/v2\/pages\/31","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/wp.optics.arizona.edu\/jsu\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/wp.optics.arizona.edu\/jsu\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/wp.optics.arizona.edu\/jsu\/wp-json\/wp\/v2\/users\/36"}],"replies":[{"embeddable":true,"href":"https:\/\/wp.optics.arizona.edu\/jsu\/wp-json\/wp\/v2\/comments?post=31"}],"version-history":[{"count":94,"href":"https:\/\/wp.optics.arizona.edu\/jsu\/wp-json\/wp\/v2\/pages\/31\/revisions"}],"predecessor-version":[{"id":2278,"href":"https:\/\/wp.optics.arizona.edu\/jsu\/wp-json\/wp\/v2\/pages\/31\/revisions\/2278"}],"wp:attachment":[{"href":"https:\/\/wp.optics.arizona.edu\/jsu\/wp-json\/wp\/v2\/media?parent=31"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}