CURRENT GROUP MEMBERS
Ph.D., Seoul National University
M.S., Incheon National University
B.S., Incheon National University
Electrochemistry in nanoscale dimensions has been increasingly attracted attention because of fascinating electrochemical behaviors, which are not observed in macroscale environments. However, it is difficult to detect electrochemical responses such in nanoscale, in particular current, because redox molecules with only limited access to a nanoelectrode produce a range of sub-nanoampere current. In attempt to detect the electron-transfer of single molecules, our lab has developed closely spaced double-electrode system to amplify current by redox cycling. My research focuses on the investigation of single-molecule redox events by means of electrochemical analysis as well as single-molecule fluorescence microscopy. In addition, single-molecule kinetics also can be attained individually in zeptoliter wells by creating isolated nanopore arrays.
Ph. D., Temple University
B.Tech., Central Electrochemical Research Institute
My research focuses on understanding the reactivity of individual enzyme cofactors, enzymes, and bacteria using coupled optical and electrochemical techniques. I am particularly interested in exploring the potential-/controlled redox environment-dependent fluorescence dynamics of the fluorogenic flavin based entities, starting from its molecular state (flavin mononucleotide and flavin adenine dinucleotide) to its state as a cofactor or electron carrier in flavoenzyme (monomeric sarcosine oxidase) or bacteria (M. Xanthus) respectively. These studies help us to understand the contribution of individual molecules behavior to the ensemble average behavior and to elucidate the metabolic pathways in microbes.
M.S., Seoul National University
B.S., Seoul National University
With the availability of highly sophisticated nanofabrication, recently more challenging and elaborate studies for electron transfer reactions have been conducted using nanotechnologies. The investigation of electron transfer events in single biological redox enzyme is one of the important topics in low dimensional electrochemistry area. My research focuses on understanding the relationship between the condition of individual redox enzymes and the macroscopic phenomenon coming from an ensemble or bulk collection of the same enzyme molecules, with anticipation of distinguished individual behavior of molecules over their average properties. For observing electron transfer events
in single enzyme molecule, electrochemical zero-mode wave guide (ZMW) structures in nanoscale are fabricated, where recessed duel-ring electrodes are employed for redox cycling to amplify faradaic currents. Combining electrochemistry with spectroscopy, electrochemical ZMW devices enable not
only the control of potential in environmentally confined nanopore structures, but also in situ measurement of the potential-dependent fluorescence dynamics of single enzyme molecules.
Tianyuan (Abby) Cao
B.S., Nanjing University
As a non-invasive, sensitive and rapid analytical tool, Raman spectroscopy has now been used extensively in biological sciences to understand the fundamentals of biochemical reactions, as well as in biomedical engineering and modern disease diagnosis. Confocal Raman imaging (CRM), which provides additional spatial information, is known to be very powerful in the detection of complex biological systems. My project is to utilize CRM method to detect the chemical characteristics of bacterial communities -- Pseudomonas aeruginosa. P. aeruginosa is a ubiquitous, gram negative opportunistic human pathogen that is associated with various severe infections such as cystic fibrosis (CF), and it also exhibits a high antibiotics resistance due to its surface motilities and biofilm formation ability. Quorum sensing system is a cell-to-cell communication system that P. aeruginosauses to regulate its biological behaviors, including biofilm formation and surface mollify, and the system relies highly on the production and secretion of small signaling molecules, known as the autoinducers. By using this powerful characterization method, I hope to understand how the autoinducers behave in P. aeruginosa strains under different environmental conditions at both macro- and molecular- level, and how these biological behaviors are regulated using quorum sensing system.
B.E., Beijing University of Chemical Technology
Understanding the photoinduced electron-transfer process is of paramount importance for realizing efﬁcient solar energy conversion. However, there is rare research in the photo-induced electron transfer of single nanoparticle because traditional research about solar-cell materials is mostly based upon bulk properties. Thus, clarifying the heterogeneity of single-nanoparticle and bulk spetcro-electrochemistry is beneficial to understand the relationship between the structure and property of solar-energy conversion nanomaterials. Combining with the emerging techniques of nano-electrochemistry in our group, I would like to answer these questions by studying a special type of confined-volume architecture, the nanopore electrode array, or NEA, which is designed to be commensurate in size with physical scaling lengths, such as the Debye length, a concordance that offers performance characteristics not available in larger scale structures.
B.S., Temple University
Psuedomonas aeruginosa is an opportunistic pathogen responsible for many hospital-acquired infections, and its ability to form biofilms contributes to its high antibiotic resistance, making these infections difficult to treat. While many studies have been performed on P.aeruginosa biofilms and bulk colonies, not much research has been done on the behavior of single P. aeruginosa bacteria. My work focuses on designing micropore electrode devices to be able to trap single bacteria and study their behavior upon changes to the surrounding environment through spectroscopic and electrochemical techniques.
HyeIn (Anne) Do
B.S., Purdue University
Surfaced Enhanced Raman Spectroscopy(SERS) demonstrates notable sensitivity for chemical and biochemical analysis, offering vibrational information for identification of numerous analytes, and Pyocyanin is the most widely studied virulence factor due to its role in pathogenesis. In my research, I am focusing on determination of the electrochemical adsorption isotherm of Ox in pyocyanin by SERS and the electrochemical behavior of Pyocyanin species as a function of potential either by cyclic voltammetry or differential pulse voltammetry.
M.S., South China University of Technology
B.S., Beijing University of Chemical Technology
The key ability for bacterial survival is to evolve with the varying environment. Alginate is a viscous extracellular polymer produced by mucoid strains of Pseudomonas aeruginosa. Also, alginate plays a role in the biofilm structure and may act as intercellular material required for formation of biofilms which makes it an important signaling molecule. In my research, confocal raman microscopy (CRM) is used to test the role and structure of alginate which is produced by
P. aeruginosa FRD1 to study the mutation of P. aeruginosa caused by protein-mucin (pig-stomach). The goal of my research is to build a signal enhanced plate for bacteria study and use it to study the signature signaling molecules produced by P. aeruginosa in the varied environment with the powerful confocal raman microscopy (CRM).
B.S., University of Alabama
Fentanyl is a highly addictive synthetic opioid that is commonly used in acute analgesia and chronic pain management. Due to its high potency in minute quantities(~2mg), illicitly manufactured fentanyl analogs have been progressively used as an adulterant and frequently associated with the alarming increase in opioid related drug overdose death, commonly referred to as the “Opioid Overdose Crisis” by the National Institute on Drug abuse. Hidden in less potent drugs like heroin and morphine, fentanyl presents a threat to unsuspecting users, emphasizing the demand for field-deployable testing on par with lab setting discrimination. While there are efforts to develop more low-cost field deployable handheld detection devices, most still fail in the need to quantify concentrations of fentanyl. In addition, gold standard detection methods like mass spectroscopy still undergo challenges in miniaturization and ease of use for quantitative analysis.
My research aims to utilize the sensitivity and inherent miniaturization of electrochemistry and translate electrochemical signals to more simple optical intensities that can be quantified using electrochromic materials. This research will focus on optimization of signal amplification due to self-induced redox cycling inherent in closed bipolar electrochemistry through electrolyte and electrode surface modifications.
B.S., Penn State University
Many biological entities are present in low concentrations and require high sensitivity and low limits of detection to effectively study analytes. Digital counting using Single Molecule Arrays (Simoa) is currently the method of choice for detection as it uses a fluorescence response from a femtoliter sized well containing one analyte, but it does not allow potential or redox control of the environment. My research focuses on adapting Simoa to create a method that allows single molecules to be probed in a potential or redox controlled environment.
B.E., The City College of New York
Cytokines are small (6-70 kDa), soluble proteins produced by many cells in the immune system that regulate responses to external pathogens such as cell-cell communication and inflammatory responses. Because cytokines are pervasive components of inflammatory-based disease, nearly every type of disease has involvement of cytokines as potential biomarkers; accordingly, these are widely used as biomarkers for diagnosis, tracking of disease progression as well as therapeutic monitoring. The aim of my research is to combine the advantages presented by electrochemical sensing, optical sensing and micro- and nanoscale architectures or materials to develop enhanced biosensing strategies for these protein biomarkers. I am studying a range of sensor structures, configurations, and transduction methods to achieve sensitive and reliable immunoassaying with an emphasis towards point-of-care (POC) applications. The strategies developed in this research focus on several approaches: separation of biorecognition and transduction schemes, signal amplification by improved geometric efficiency, improved sensor stability and resistance to biofouling (i.e. electrode passivation by adsorption of nontarget biomolecules), and enhanced analyte delivery via improved fluidic transport.
B.A., Earlham College
With the mortality rate of 28 to 50%, sepsis has been categorized as one of the most dangerous conditions, with over 31.5 million cases each year worldwide. The estimated number of deaths caused by sepsis in the US is much higher than the total number of deaths caused by prostate cancer, AIDS, and breast cancer combined. Sepsis is generally defined as Systemic Inflammatory Response Syndrome (SIRS) occurs with confirmed infections to the patients. Sepsis fatality is not caused by the invasion of the pathogens or the microorganisms but by the extreme response, causing imbalances in the body's immune system, which later results in the dysregulation of organ function, coagulation, and hypertension. The balance between SIRS and Compensatory Anti-Inflammatory Response Syndrome (CARS) is crucial in determining septic progression and outcome. As the liver plays a vital role in regulating the inflammatory and anti-inflammatory response of the body immune system, my research focuses on developing an electrochemical device for early detection of liver injuries as a prognosis tool for sepsis. To optimize the sensing performance of this bio-sensing device, I want to investigate different surface modification methods and immobilization strategies, when utilizing the novel geometrical configuration of the closed bipolar electrochemical system.