David Kinnamon

Portable biosensor for monitoring cortisol in low-volume perspired human sweat

A non-faradaic label-free cortisol biosensor was demonstrated using MoS2 nanosheets integrated into a nanoporous flexible electrode system. Low volume (1–5 μL) sensing was achieved through use of a novel sensor stack design comprised of vertically aligned metal electrodes confining semi-conductive MoS2 nanosheets. The MoS2 nanosheets were surface functionalized with cortisol antibodies towards developing an affinity biosensor specific to the physiological relevant range of cortisol (8.16 to 141.7 ng/mL) in perspired human sweat. Sensing was achieved by measuring impedance changes associated with cortisol binding along the MoS2 nanosheet interface using electrochemical impedance spectroscopy. The sensor demonstrated a dynamic range from 1–500 ng/mL with a limit of detection of 1 ng/mL. A specificity study was conducted using a metabolite expressed in human sweat, Ethyl Glucuronide. Continuous dosing studies were performed during which the sensor was able to discriminate between four cortisol concentration ranges (0.5, 5, 50, 500 ng/mL) for a 3+ hour duration. Translatability of the sensor was shown with a portable form factor device, demonstrating a comparable dynamic range and limit of detection for the sensor. The device demonstrated a R2 correlation value of 0.998 when comparing measurements to the reported impedance values of the benchtop instrumentation.

Use of dicationic ionic liquids as a novel liquid platform for dielectrophoretic cell manipulation

Separation, characterization and analysis of target cells demonstrate critical cues for diagnosis and monitoring of chronic diseases. Electrokinetic cell separation methods have been previously established to have greater efficiency when compared to traditional flow cytometry methods. Ionic liquids show promise in the design of conductive buffers with required electrical properties suitable for electrokinetic manipulation of cells with an enhanced signal to noise ratio (SNR). The goal of this project is to design and test tailored ionic liquid compositions with the hypothesis that dielectrophoretic forces are enhanced on cells while creating an environment for retaining cell integrity. We analysed two uniquely synthesized methylimidazolium based ionic liquids with a low toxicity as conductive suspension buffers for cell separation. These dicationic ionic liquids possess slight electrical and structural differences with high thermal stability. The two ionic liquids were tested for cytotoxicity and their ability to enhance SNR. We validated our hypothesis using osteosarcoma cells Saos-2 and MC3T3-E1 osteoblast cells. The tests were compared against commonly used dielectrophoretic sucrose-isotonic solution. The effects of electrical neutrality, charged particle effects, free charge screening due to ionic liquids from cells were studied using a single-shell model. Effects of ionic liquid and isotonic medium on electrokinetic signal from cells were studied through dielectrophoretic force profiles as a function of non-linear displacement of cells in the two ionic liquids and control media. We observed significant differences in electrokinetic responses between healthy and cancerous cells and steady increase in signal magnitude resulting in enhanced SNR using ILs when compared against sucrose buffer.

Fully electronic urine dipstick probe for combinatorial detection of inflammatory biomarkers

Aim: An electrochemical urine dipstick probe biosensor has been demonstrated using molybdenum electrodes on nanoporous polyamide substrate for the quantitative detection of two inflammatory protein biomarkers, CRP and IL-6. Materials & methods: The electrode interface was characterized using ζ-potential and Fourier transform infrared spectroscopy. Detection of biomarkers was demonstrated by measuring impedance changes associated with the dose concentrations of the two biomarkers. A proof of feasibility of point-of-care implementation of the biosensor was demonstrated using a portable electronics platform. Results & conclusion: Limit of detection of 1 pg/ml was achieved for CRP and IL-6 in human urine and synthetic urine buffers. The developed portable hardware demonstrated close correlation with benchtop equipment results.

Electronic bracelet for monitoring of alcohol lifestyle

We demonstrate a wearable electronic bracelet for monitoring of alcohol lifestyle through the detection of ethyl glucuronide (EtG), a metabolite of ethanol associated with alcohol consumption, from human sweat. The device leverages disposable nanoporous polymer substrates that easily wick small volumes of sweat over the sensors electrodes. A gold working electrode fabricated on the flexible substrate is functionalized with EtG specific monocolonal antibodies using thiol based chemistry, as well as with a potassium ferricyanide redox molecule. When exposed to EtG in pooled human sweat, and sweat analog the binding of EtG to the sensing electrode results in chemiresistive changes to the electrode surface that can be quantified using square wave voltammetry (SWV). Varying doses of EtG was thus quantified and reported electronically by measuring changes in response peak currents. Detection of EtG was demonstrated in the range of 1–100 μg/mL in sweat analog. Similar dose discrimination was shown in the range of 1–10000 μg/L for human sweat, corresponding to one or more U.S. standard drinks. Validation of the EtG sensor performance was done using cyclic voltammetry and electrochemical impedance spectroscopy.

Portable Chronic Alcohol Consumption Monitor in Human Sweat through Square-Wave Voltammetry:

Chronic alcohol consumption is a significant financial and physical burden in the United States each year. Alcohol consumption monitors focus on establishing a state of intoxication, not assessing a user’s health risks as a function of consumed alcohol. This work demonstrates a biosensor for a chronic alcohol consumption monitor through the electrochemical detection of ethyl glucuronide (EtG) in human sweat using square-wave voltammetry (SWV). A novel affinity assay was demonstrated in which monoclonal antibodies were chemically coabsorbed onto a gold electrode surface in parallel with thiolated charge transfer molecule. Concentration-dependent EtG binding was detected by measuring a reduction in the charge transfer of the sensor, manifesting as a current response during SWV measurement. A companion compact electronic reader was constructed, demonstrating comparable sensitivity to a conventional lab instrument. Both tools demonstrated a limit of detection of 0.1 µg/L and a linear dynamic range of 0.1–100 µg/L corresponding to the physiologically relevant range of EtG expression in human sweat. This device can address the need for a chronic alcohol consumption monitor toward establishing a user’s long-term consumption habits to assess the risk of developing specific diseases and conditions associated with regular alcohol consumption, through integration with existing technologies.

AWARE: A Wearable Awareness with Real-time Exposure, for monitoring alcohol consumption impact through Ethyl Glucuronide detection

Here we demonstrate for the first time a dynamic monitoring of the ethanol metabolite Ethyl Glucuronide (EtG) for a more robust evaluation of alcohol consumption compared to conventional methods. A wearable biosensor device capable of reporting EtG levels in sweat both continuously via low power impedance spectroscopy is reported. The custom hardware was compared against conventional benchtop potentiostat, demonstrating comparable results in the application space of EtG detection in low volume sweat. The device successfully differentiated three distinct EtG concentrations correlating to simulated drinking scenarios estimated to be 1, 2, and 3 standard U.S. drinks consumed over a duration of 60 minutes with p < 0.0001. This device has the potential to enable moderate drinkers to engage in guided decision making, based on objective data, addressing the needs of alcohol sensitive populations. The device also will serve as a tool for researchers to better understand and characterize the relationship between sweat EtG and consumed alcohol.