About

Mei Shen is an Assistant Professor in the Department of Bioengineering at the University of Illinois Urbana-Champaign, located in the Grainger College of Engineering. Her primary research focuses on micro and molecular technologies, specifically neural recording, bionanotechnology, cancer detection, chemical biosensors, live-cell imaging, microfabrication, nanofabrication, nanosensors, stem cell differentiation, and tumor microenvironments. She is involved in advancing early cancer detection and live-cell imaging techniques, utilizing microfabrication and nanotechnology to develop innovative tools for biomedical applications. Her work contributes to understanding neural recording and the development of chemical biosensors, with an emphasis on applications in health and disease.

Research topics

• Chemistry
• Materials science
• Physical chemistry
• Nanotechnology
• Organic chemistry
• Physics
• Chemical physics
• Inorganic chemistry
• Chemical engineering
• Chromatography
• Medicine
• Pathology
• Engineering
• Environmental chemistry

Selected publications

• Observation of Acetylcholine Secretion on Living Glioblastoma Cells

  ACS Measurement Science Au · 2026-05-06

  articleOpen accessSenior authorCorresponding

  Glioblastoma, as the most common malignant brain tumor in humans, remains a big societal challenge; identifying new signaling molecules in glioblastoma opens avenues for alternative treatment strategies. Emerging evidence suggests that neurochemical signaling is involved in glioblastoma pathology. However, it is unknown if the neurotransmitter acetylcholine can be secreted by glioblastoma cells despite the expression of the acetylcholine synthesis enzyme. Here, we tested our hypothesis that glioblastoma cells secreted acetylcholine using a nanoelectrochemistry platform: scanning electrochemical microscopy (SECM) and nanoelectrodes. Linear and selective acetylcholine detection was achieved on the nano interface between two immiscible electrolyte solutions (nanoITIES, also called liquid/liquid interface). Using SECM, we positioned the acetylcholine-sensing nanoITIES electrodes very close (i.e., hundreds of nanometers) to the living T98G glioblastoma cells. We observed real-time secretion of acetylcholine from glioblastoma cells. We quantified the number of secreted acetylcholine molecules. Our discovery that glioblastoma cells secrete acetylcholine reveals a novel signaling axis in glioblastoma biology, highlighting a potential therapeutic target for glioblastoma treatment.

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• Systems nanoelectrochemistry from single entity to ensemble: general discussion

  Faraday Discussions · 2025-01-01

  article

  Kim McKelvey opened discussion of the paper by Paolo Actis: Can you expand on why you see enhanced signals for nanoparticle translocations when you have a large concentration of polyethylene glycol (PEG) present? Paolo Actis answered: We have discussed the mechanism in detail in

  PublisherDOI

• Liquid/Liquid Junction Microelectrodes for Monitoring Cholinergic Transmitter in Live Mice Brain <i>In Vivo</i>

  ECS Meeting Abstracts · 2025-07-11

  article1st authorCorresponding

  High spatiotemporal studies on the signaling of a broad range of neurotransmitters are essential to understand brain functions and diseases. Shen group has developed nanoscale interface between two immiscible electrolyte solution (nanoITIES) liquid-liquid junction probes to enable the detection of redox-inactive neurotransmitters [1,2,3,4,5]. By using the liquid/liquid approach, we circumvent the challenges in the measurement of redox inactive neurotransmitters using nanoelectrochemistry. To push the limit further, we further developed dual-functional nano-carbon-liquid/liquid interface probes for the simultaneous detection of acetylcholine (redox-inactive) and dopamine (redox-active) [6]. In this talk, we will share our recent efforts in developing microITIES electrodes for in vivo measurement of acetylcholine at high spatiotemporal resolution. The microITIES electrode was implanted in the cortex of the mouse brain via stereotaxic surgery. The electrode was tested for exogenously applied acetylcholine in vivo by the local injection of acetylcholine. The electrode was also tested for endogenously released acetylcholine in mice brain by the local injection of a high concentration KCl solution to stimulate acetylcholine release. These results validated the capability of the introduced ITIES electrode to measure exogenous and endogenous acetylcholine in vivo . References: Detection of Acetylcholine at Nanoscale NPOE/Water Liquid/Liquid Junction Electrodes. Jetmore, H. D.; Milton, C.; Satheesan, A. E.; Chen, R.; Xu, K.; Shen, M*. Analytical Chemistry , 93, 16535–16542 (2021). A High Spatiotemporal Study of Somatic Exocytosis with Scanning Electrochemical Microscopy and nanoITIES Electrodes. Welle, T. M.;Alanis, K.;Colombo, M. L.;Sweedler, J. V.; Shen, M.* Chemical Science , 9, 4937-4941 (2018). Interface between Two Immiscible Electrolyte Solutions Electrodes for Chemical Analysis. Jetmore, H.; Satheesan, A. E.; Cress, T.; Shen, M.* Invited Feature Article , Analytical Chemistry , 94,16519–16527(2022) GABA Detection with nano-ITIES pipet electrode: a new mechanism, water/DCE–octanoic acid interface. Iwai, N. T.; Kramaric, M.; Crabbe, D.; Wei, Y.; Chen, R.; Shen, M.* Analytical Chemistry , 90, 3067-3072(2018). Recent Advances in Nanoelectrochemistry at the Interface Between Two Immiscible Electrolyte Solutions.Milton, C.; Xu, K.; Shen, M.* Current Opinion in Electrochemistry . 34, 101005 (2022). Dual-channel Nano-carbon-liquid/liquid Junction Electrodes for Multi-modal Analysis: Redox-active (dopamine) and Non-redox-active (acetylcholine). Satheesan, A. E.; Chen, R.; Kalski, D.; Palmer, J.; Shen, M*. Analyst , DOI: 10.1039/D4AN01153H (2025)

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• Spectroelectrochemistry and light active process at nanointerface: general discussion

  Faraday Discussions · 2025-01-01

  article

  Christian Kuttner opened a general discussion of the paper by Frédéric Kanoufi: While nanoelectrochemistry has revealed the edge effect, the full mechanistic understanding at individual particle levels remains unclear (https://doi.org/10.1039/d4fd00132j). In seeking mechanistic understanding of

  PublisherDOI

• Selective Detection of Acetylcholine against Choline and In Vivo Measurement in the Mouse Brain Using the Micropipet-Supported Liquid/Liquid Interface Electrode

  ACS Measurement Science Au · 2025-10-20 · 5 citations

  articleOpen accessSenior authorCorresponding

  Acetylcholine (ACh) is a neurotransmitter that plays critical roles in human health and diseases. To better understand ACh signaling in the brain, developing analytical capabilities for its selective and quantitative measurement in real time is essential. While electrochemical amperometry offers exceptional temporal resolution, most in vivo electrochemical ACh sensors have limited selectivity, such as against choline (the product of ACh hydrolysis) and ascorbic acid. Here, we report a micropipet-supported ITIES (interface between two immiscible electrolyte solutions), which demonstrated the selective detection of ACh against choline, ascorbic acid, and other neurotransmitters using chronoamperometry. The detection of ACh is based on its ion transfer across a water/oil interface, which was formed between an aqueous solution and a 2-nitrophenyl octyl ether (NPOE) solution containing an ACh ionophore, termed water/NPOE-ionophore ITIES. The ionophore was heptakis-(2,6-di-O-methyl)-β-cyclodextrin (DM-β-CD). The addition of DM-β-CD in the NPOE phase resulted in an easier ACh transfer at the water/NPOE-ionophore ITIES compared with that at the ITIES without the ionophore, suggesting the presence of ionophore-facilitated ion transfer in addition to the direct ion transfer at the water/NPOE-ionophore ITIES. We observed a linear detection of ACh on the water/NPOE-ionophore ITIES. When implanted in the cortex of the brain of a live mouse, the water/NPOE-ionophore ITIES tracked the dynamic concentration changes of the injected ACh in the brain. The measuring techniques are broadly applicable to quantifying real-time ACh release in the brain with negligible interference, enabling a better understanding of neurological disorders and diseases.

  PublisherDOI

• Novel Electrochemical Sensors for <i>In Vivo</i> measurements of Acetylcholine

  ECS Meeting Abstracts · 2025-11-24

  articleSenior author

  Neurotransmitters play important roles in plenty of brain functions such as learning, memory, and emotion. Abnormal levels of some neurotransmitters are also reported to be related to neurological disorders. For example, decreased levels of acetylcholine (ACh) were found in Alzheimer’s’ diseases patients. To better understand brain function and diseases, developing platforms to quantitatively measure ACh in live mice brain is necessary and critical. Shen lab has been working on the development of electrodes for ACh detection at high spatiotemporal resolution for possible in vivo applications. In this oral presentation, I would like to introduce the novel electrochemical ACh sensors without enzyme modification developed in our lab recently with different sensing strategies. The first kind of electrode is an ion-selective electrode fabricated by the deposition of ionophore layer targeting ACh on electrode surface [1] . Specifically, a glassy carbon electrode was firstly deposited with a poly(3,4-ethylenedioxythiophene (PEDOT) layer electrochemically, then an ionophore-doped poly(vinyl) chloride (PVC) membrane was deposited on top of the PEDOT layer by drop-casting to achieve selective detection of ACh. Surface characterization showed the uniform deposition of polymer layers, and cyclic voltammetry (CV) showed selective detection of ACh. The second kind of electrode is a micrometer-sized liquid/liquid interface electrode based on the ACh ion transfer at the interface between two immiscible electrolyte solutions (ITIES) [2] . The liquid/liquid interface is formed between two immiscible electrolyte solutions where one phase is aqueous and the other phase is an organic phase. We have made microITIES electrodes with radius of around 1 to 3 µm. The microITIES electrode showed linear, selective, and sensitive detection of ACh. When applied for in vivo detection in the cortex of live mouse brain, the electrode showed a stable in vivo background current within a short period of time after the implantation. The electrochemical recording of ACh response was performed after a stable background was achieved to ensure that biofouling was not a confounding factor. The microITIES electrode showed response towards exogenously applied and endogenously released acetylcholine via cyclic voltammetry (CV). References: [1] Xu, P.; Muhamad Rapidi, H. I.; Ahmed, S.; Abel, D. K.; Garcia, K. J.; Chen, R.; Iwai, N. T.; Shen, M. PEDOT/PVC-modified amperometric carbon electrodes for acetylcholine detection. Chemical Communications 2022 , 58 (95), 13218-13221, [2] Xu, P.; Shen, M. Liquid/liquid junction microelectrodes for monitoring cholinergic transmitter in live mice brain in vivo. Biosensors and Bioelectronics 2025 , 278 , 117315.

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• Scanning electrochemical probe microscopy: general discussion

  Faraday Discussions · 2025-01-01

  article

  Christian Kuttner opened the discussion of the paper by Mei Shen: The current–concentration relationship follows a Michaelis–Menten model, with well-defined constants like Imax and Km for glutamate detection. How does nanoscale confinement impact the enzyme kinetics and binding efficiency at th

  PublisherDOI

• Liquid/liquid junction microelectrodes for monitoring cholinergic transmitter in live mice brain in vivo

  Biosensors and Bioelectronics · 2025-02-26 · 7 citations

  articleOpen accessSenior authorCorresponding

  Acetylcholine (ACh) is an important neurotransmitter and biomarker for neurological disorders. The quantitative detection of ACh in vivo is critical but remains a challenge. In this work, we developed a novel micrometer-sized electrode based on interface between two immiscible electrolyte solutions (ITIES) to achieve in vivo measurement of ACh at high spatiotemporal resolution. The fabricated microITIES electrode was tested in vitro for ACh sensing using electrochemical methods including cyclical voltammetry and i-t amperometry in artificial cerebrospinal fluid (ACSF) solution. An increase in current was observed in both CV and i-t at −0.25 V (vs E 1/2, TEA ). Both CV and i-t showed a high sensitivity and a linear response with the linear range starting from as low as 0.5 μM. Then the electrode was applied for in vivo measurement of ACh in the living mouse brain. The electrode was implanted in the cortex of the mouse brain via stereotaxic surgery. The electrode was tested for exogenously applied ACh in vivo by local injection of ACh (500 nL, 0.5 M) twice. Repeated cyclic voltammograms were recorded before, during, and after both injections; the cyclic voltammograms showed a significant increase in current at ACh detection potential. The electrode was also tested for endogenously released ACh in vivo by the local injection of a high concentration KCl solution (500 nL and 1000 nL, 100 mM) to stimulate ACh release. Similarly, repeated cyclic voltammograms were recorded before, during, and after both injections; a significant increase in current at the ACh detection potential in the cyclic voltammograms was observed following each injection of KCl. These results validated the capability of the introduced microITIES electrode to measure exogenous and endogenous ACh in vivo . • A novel micrometer-sized liquid/liquid junction electrode to detect acetylcholine in vivo at high spatiotemporal resolution. • Acetylcholine detection is based on the ion transfer at the interface between two immiscible electrolyte solutions (ITIES). • The microITIES electrode exhibited linear, selective, and sensitive detection of acetylcholine. • ITIES electrode measured exogenously applied and endogenously released acetylcholine in mouse brain via cyclic voltammetry. • The microITIES electrode is the first quantitative sensor of in vivo acetylcholine at such high spatiotemporal resolution.

  PublisherDOI

• ( <i>Invited</i> ) Nano Liquid/Liquid Junction Electrodes for Interrogating Neurotransmitter Dynamics with High Spatiotemporal Resolution

  ECS Meeting Abstracts · 2025-11-24

  article1st authorCorresponding

  Measuring and quantifying neurotransmitters in real-time at high spatiotemporal resolution is essential to understand the brain functions and diseases. Chemical sensing with electrodes offers chemical identity, quantification, fast response time, and high spatial resolution about biological processes in vivo (1). By decreasing the electrodes to nanometers in size, nanometer spatial resolution has been achieved. Using chronoamperometry, millisecond temporal resolution on the relevant time scale of exocytosis is possible. Electrochemically speaking, there are two kinds of transmitters, i.e., redox-active and redox-inactive. By using the liquid/liquid junction approach, we circumvent the challenges in the measurement of redox-inactive neurotransmitters using nano-electroanalytical methods. Shen group has reported the development and application of nanoscale interface between two immiscible electrolyte solutions (nanoITIES) for the detection of cholinergic transmitter dynamics in real-time from single cells and single synapses (1-4). To push the limit further, we have developed dual-functional nano-carbon-ITIES electrodes to detect and quantify both redox-active and non-redox-active neurotransmitters at the same time at the nanoscale (5). These efforts to develop new nanoelectrodes for sensing neurotransmitters in couple with scanning electrochemical microscopy at nanometer spatial and millisecond temporal resolution will be presented here. Single Synaptic Observation of Cholinergic Neurotransmission on Living Neurons: Concentration and Dynamics. Shen, M. ; * Qu, Z.;Deslaurier, J.;Welle, T.;Sweedler, J.;Chen, R. Journal of the American Chemical Society , 140, 7764-7768(2018). Detection of Acetylcholine at Nanoscale NPOE/Water Liquid/Liquid Junction Electrodes. Jetmore, H. D.; Milton, C.; Satheesan, A. E.; Chen, R.; Xu, K.; Shen, M*. Analytical Chemistry , 93, 16535–16542 (2021). A High Spatiotemporal Study of Somatic Exocytosis with Scanning Electrochemical Microscopy and nanoITIES Electrodes. Welle, T. M.;Alanis, K.;Colombo, M. L.;Sweedler, J. V.; Shen, M.* Chemical Science , 9, 4937-4941 (2018). GABA Detection with nano-ITIES pipet electrode: a new mechanism, water/DCE–octanoic acid interface. Iwai, N. T.; Kramaric, M.; Crabbe, D.; Wei, Y.; Chen, R.; Shen, M.* Analytical Chemistry , 90, 3067-3072(2018). Satheesan, A. E.; Chen, R.; Kalski, D.; Palmer, J.; Shen, M *. Dual-channel Nano-carbon-liquid/liquid Junction Electrodes for Multi-modal Analysis: Redox-active (dopamine) and Non-redox-active (acetylcholine). Analyst, 150, 414 – 424 (2025).

  PublisherDOI

• Scanning Electrochemical Microscopy to Characterize Acetylcholine Release from Living Cells

  ECS Meeting Abstracts · 2025-11-24

  articleSenior author

  The neurotransmitter acetylcholine (ACh) is vital to synaptic chemical transmission 1 and is implicated in the pathological mechanisms of numerous diseases. 2 However, because ACh is not redox-active, solid (e.g., carbon, Pt) electrochemical probes capable of high temporal resolution analyte detection cannot sense ACh. To electrochemically detect ACh without enzyme-modification, our lab developed nanoscale interface between two immiscible electrolyte solutions (nanoITIES) electrodes to detect ACh ion transfer across a liquid/liquid interface of immiscible organic and aqueous phases. 3,4 To apply nanoITIES electrodes to cellular studies of ACh release, these electrodes were positioned with scanning electrochemical microscopy (SECM) to within nanometers of living Aplysia californica neurons. Prior to SECM nanopositioning, a nanoelectrode and stimulating pipette were localized using an upright side view optical microscope to a specific region (e.g., soma, synapse) of a neuron on a reflective culturing substrate. 5,6 After nanopositioning, ACh release from neurons was stimulated by high concentration potassium chemical stimulation, and real-time ACh release was detected from the synapses 5 and soma. 6 Here, we present a home-built SECM and inverted microscopy system for live cell electrochemical detection and imaging, presenting analytical advantages such as 1) phase contrast imaging, 2) higher precision optical localization of nanoelectrodes, 3) maintenance of cell environment during SECM experiments, and 4) tandem SECM plus fluorescent imaging. SECM 7 and SICM 8 have been integrated with inverted microscopy to position micro- and nanoelectrodes for 1) electrochemical imaging of live cell morphology and 2) measurement of ion transport, including of catecholamines, across live cell membranes. Our SECM plus inverted microscope system uses an LED ring light source to achieve phase contrast imaging 9 for better contrast when imaging transparent samples such as cells. We are using this platform to detect and quantify real-time neurotransmitter release from living disease-state cells with high spatiotemporal resolution. Overall, this integrated SECM plus inverted microscopy system will enable more expansive studies of the topography and chemical release of living cells, improving characterization of cellular processes and disease states. Y. P. Singh et al., Eur J Med Chem , 215 , 113278 (2021) https://doi.org/10.1016/j.ejmech.2021.113278. X. Gu and X. Wang, Anal Biochem , 632 , 114381 (2021) https://doi.org/10.1016/j.ab.2021.114381. M. L. Colombo, J. V Sweedler, and M. Shen, Anal Chem , 87 , 5095–5100 (2015) https://doi.org/10.1021/ac504151e. H. D. Jetmore et al., Anal Chem , 93 , 16535–16542 (2021) https://doi.org/10.1021/acs.analchem.1c03711. M. Shen et al., J Am Chem Soc , 140 , 7764–7768 (2018) https://doi.org/10.1021/jacs.8b01989. T. M. Welle, K. Alanis, M. L. Colombo, J. V Sweedler, and M. Shen, Chem. Sci. , 9 , 4937–4941 (2018) https://doi.org/10.1039/C8SC01131A. L. Pitta Bauermann, W. Schuhmann, and A. Schulte, Physical Chemistry Chemical Physics , 6 , 4003–4008 (2004) https://doi.org/10.1039/B405233A. L. Zhou, Y. Gong, J. Hou, and L. A. Baker, Anal Chem , 89 , 13603–13609 (2017) https://doi.org/10.1021/acs.analchem.7b04139. K. F. Webb, J Microsc , 257 , 8–22 (2015) https://doi.org/10.1111/jmi.12181.

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Recent grants

• CAREER: Multimodal Nanoelectrochemistry to Characterize Nanometer and Microsecond Resolved Transmitter Release

  NSF · $632k · 2019–2026

• Study Exocytosis in the Region of Synaptic Cleft using Electrochemical Nanoprobe

  NIH · $391k · 2013–2017

Frequent coauthors

• Ran Chen

  13 shared

• Joaquín Rodríguez‐López

  University of Illinois Urbana-Champaign

  11 shared

• Michelle L. Colombo

  Urbana University

  10 shared

• Allen J. Bard

  The University of Texas at Austin

  9 shared

• Edappalil Satheesan Anupriya

  Chan Zuckerberg Initiative (United States)

  8 shared

• Kristen Alanis

  Texas A&M University

  6 shared

• Yi‐Ting Lee

  Kyushu University

  6 shared

• Jonathan V. Sweedler

  University of Illinois Urbana-Champaign

  6 shared

Labs

• Shen LabPI