Submitted To: NCIIA BME Idea

A Novel Approach to Lactate Sensing: Use of a Mouthguard Embedded Microfluidic Lactate Sensor For Clinical Diagnosis and Sports Performance

Submitted to: NCIIA BME Idea

Date: November 4, 2010

Tuo Fu Li

L. Wern Ong

Joseph Sun

Stephanie Wu

Christine Zhang

Department of Biomedical Engineering

Vanderbilt University

2301 Vanderbilt Place

Nashville, TN 37235

615-322-3521

Zhang, Wu 11.05.2010 Project Abstract

Increased blood lactate level is a common clinical measure of anaerobic metabolism. This tool is invaluable to physicians assessing the extent of irreversible tissue damage in conditions as varied as heart attack, muscle fatigue, Alzheimer’s, ischemic stroke, and septic shock. Changes in lactate level during abnormal physiological processes hold immense potential as a clinical indicator of disease state, progression, and outcome. Changes in lactate level during normal physiological processes may also be useful in sports physiology, where determination of lactate threshold or anaerobic threshold can maximize training efficiency. Modeling lactate levels over time may reveal information that discrete sampling cannot. Top three features of lactate sensor:

 Robust and versatile

 Accessible to patients of various age, size, ethnicity, and gender

 Continuous measurement

Introduction

Increased blood lactate level is a common clinical measure of anaerobic metabolism. This tool is invaluable to physicians assessing the extent of irreversible tissue damage in conditions as varied as heart attack, muscle fatigue, Alzheimer’s, ischemic stroke, and septic shock (Romero

2010). Changes in lactate level during abnormal physiological processes hold immense potential as a clinical indicator of disease state, progression, and outcome (Ellmerer 2009, Scott 2010,

Simoes 2010). Changes in lactate level during normal physiological processes may also be useful in sports physiology, where determination of lactate threshold or anaerobic threshold can

Zhang, Wu 11.05.2010 maximize training efficiency (Scharhag 2010). Modeling lactate levels over time may reveal information that discrete sampling cannot.

Recent studies indicate a significant correlation between saliva and blood lactate levels

(Kelsay et al 1972, Kesay et al1974, T Ohkuwa et al 1995, C Schabmueller et al 2006, Segura

1996, Takeda I et al. 2009). Saliva is easily sampled from subjects yet blood lactate measurements remain ubiquitous in clinical settings. A device is needed capable of continuously sampling saliva lactate levels in order to replace traditional invasive techniques. Our design project addresses this need through research and development of a mouthguard embedded microfluidic lactate sensor capable of wirelessly transmitting real time lactate level data. Possible models may include multi analyte sensors to provide physicians with a broad spectrum of information.

History and Context

Rapid changes in the desired application have occurred within the first phase of design.

Our team began brainstorming from a seed topic, lactate sensing, suggested by our mentor Dr.

Franz Baudenbacher as a potentially useful clinical diagnosis and prognosis tool. Extensive research within the past two months have revealed the limitations of current sensing techniques and the market niche our saliva lactate sensor will occupy.

Initial models focused on the possibility of machining a subcutaneous multianalyte electrode capable of interfacing with Medtronic’s continuous glucose monitoring system. The premise of this design was to replace only the electrochemical electrode embedded into a subject’s subcutaneous abdominal adipose tissue. Multiple “pockets” within the electrode’s

Zhang, Wu 11.05.2010 sensing tip would preferentially hold different analytes (glucose or lactate) and their respective oxidases (Reghabi 2005). This layout would enable differential measurements of glucose and lactate levels from one fluid sample. Further investigation revealed subcutaneous lactate levels are not significantly correlated with blood lactate levels and a ten minute latency period exists for changes in subcutaneous adipose tissue glucose levels with respect to blood glucose levels

(Ellmerer 2009).

Lactate sensing still remained our greatest priority. The next model focused on the possibility of machining a microfluidic lactate sensor for saliva. Kelsey et al (1972) discovered a significant correlation between blood and saliva lactate levels in a metabolic study of seven young women. Multiple other studies (Kelsay et al 1974, T Ohkuwa et al 1995, C Schabmueller et al 2006, Takeda I et al. 2009) corroborate the relationship between blood and saliva lactate levels. In order to address concerns of stability, flow, and placement method, our current design seeks to embed, into a compact and versatile mouthguard, a microfluidic sensor hardwired to a microprocessor capable of wirelessly transmitting data through Bluetooth technology.

The applications and settings in which this device may be used are diverse and exciting.

Sports teams may harness continuous lactate level curves as well as anaerobic threshold data to plan more efficient and effective training regimens. Knowledge of an individual’s anaerobic threshold will allow intensive training despite discomfort and cessation of training before lactate levels become deleterious. Battlefield medicine can utilize this same data to determine the extent of irreversible tissue damage and optimize treatment to salvageable areas. NICU’s can measure the extent of tissue perfusion in premature infants without having to insert bulky catheters into a patient’s small vessels. The potential for clinical medicine is too great to detail here. A

Zhang, Wu 11.05.2010 mouthguard embedded lactate sensor will provide a simple, versatile, and continuous measure of lactate levels in all the narrated scenarios.

Five biomedical engineers, Toby Li, Joseph Sun, Wern Ong, Christine Zhang, and

Stephanie Wu, comprise this design team. Altogether, we possess a broad spectrum of strengths, motivations, and perspectives; a collaborative team dynamic harnesses individual strengths in a synergistic manner. Toby Li is a double major in Economics and Biomedical Engineering. His expertise in both fields provides a unique perspective on the market potential and financial constraints of our design product. Joseph Sun, a Biomedical Engineer, has extensive research experience in basic sciences and design of microfluidic devices. His prior projects include development of a myocardial cell picocalorimeter, a topic which heavily overlaps with the design of our microfluidic lactate sensor. Wern Ong, a Biomedical Engineer, brings industry expertise to our design process. His prior internship with Medtronic’s sensor division in San Francisco will prove invaluable to the accessibility of industry experts and availability of physical resources.

Stephanie Wu, a Biomedical Engineer and minor in Engineering Management, provides expert guidance through the proper application and documentation procedures as well as regular assessments of the feasibility of our design. Christine Zhang, a Biomedical Engineer and minor in Molecular and Cellular Biology, gives in depth insight to the physiology and disease mechanisms encountered. Her research experience encompasses both computational modeling in a neurophysiology lab and profiling of Avian beta defensins in a Salmonella pathogenesis study

Zhang, Wu 11.05.2010 published in BMC Microbiology. Christine will also serve as team technology guru, responsible for building and maintaining the group’s online presence.

Work Plan and Outcomes

The main purpose of this design project is to give our team a chance to pursue our own interests while applying all the knowledge and skills we have learned within the past three years.

We seek to gain first hand experience building a device to meet a need we see in the community.

At the end of this project, we hope to contribute new knowledge to the scientific community on the feasilibility of continuous lactate level measurements in saliva as well as build a prototype that may be used in clinical, athletic, and battlefield settings. We intend to apply for the

BMEIdea stipend, BMEIdea grant and obtain IRB approval to develop and test our device on human subjects. A patent may be filed if the device proves to be effective. Though the viability of this tool is undoubted, too many factors remain undefined to predict commercial success of this product.

Evaluation and Sustainability Plan

A robust and versatile lactate sensor is required to transition between diverse settings: hospital to clinics to athletic fields. Sensing must be accessible to patients of various age, size, ethnicity, and gender and account for the differences that may arise due to these traits.

Continuous measurements are necessary to study fluctuations in lactate levels on a small time

Zhang, Wu 11.05.2010 interval and to extract patterns from fluctuations over a long time course. Saliva lactate levels must also significantly reflect blood lactate levels in a timely fashion.

Our goal is to design and build a prototype possessing all the above detailed features.

Success will be achieved if and when our prototype is capable of reflecting physiological changes in real time. Completing landmarks in the design and development will also provide a periodic measure of success.

References

1. Martin Ellmerer et al. “Clinical Evaluation of Subcutaneous Lactate Measurement in Patients after Major

Cardiac Surgery.” International Journal of Endocrinology 2009 (390975), (03 Mar 2009).

2. J Kelsay et al. “Pyruvate and Lactate in Human Blood and Saliva in Response to Different Carbohydrates.”

Journal of Nutrition 102 (5), 661 (1972).

3. J Kelsay, K Behall, and W Clark. “Glucose, fructose, lactate and pyruvate in blood and lactate and pyruvate

in parotid saliva in response to sugars with and without other foods.” The American Journal of Clinical

Nutrition 27, 819-25 (Aug 1974).

4. Bahar Reghabi et al. Implantable apparatus for sensing multiple parameters. US Patent 2005/0148832 A1.

5. Marcelo Romero et al. “Amperometric Biosensor for Direct Blood Lactate Detection.” Analytical

Chemistry 82 (13), 5568-72 (02 Jun 2010).

6. C Schabmueller et al. “Micromachined sensor for lactate monitoring in saliva.” Biosensors and

Bioelectronics 21 (1), 1170-1776 (2006).

Zhang, Wu 11.05.2010 7. Friederike Scharhag-Rosenbergera et al. “Exercise at given percentages of VO2max: Heterogeneous

metabolic responses between individuals.” Journal of Science and Medicine in Sport 13 (1), 74-9 (Jan

2010).

8. Sean Scott et al. “Two-Hour Lactate Clearance Predicts Negative Outcome in Patients with

Cardiorespiratory Insufficiency.” Critical Care Research and Practice 2010 (917053), (23 May 2010).

9. R Segura et al. “A new approach to the assessment of anaerobic metabolism: measurement of lactate in

saliva.” British Journal of Sports Medicine 30 (4), 305-9 (1996).

10. Herbert Simoes et al. “Methods to identify the anaerobic threshold for type-2 diabetic and non-diabetic

subjects.” Arquivos Brasileiros de Cardiologia 94 (1), 71-8 (Jan 2010).

11. Takeda I et al. “Understanding the human salivary metabolome.” NMR in Biomedicine 22 (6), 577-84 (Jul

2009).

Appendix

 Budget Template with Budget Justification

 Gantt Chart

 Tuo Fu Li Resume

 L. Wern Ong Resume

 Joseph Sun Resume

 Stephanie Wu Resume

 Christine Zhang Resume

Zhang, Wu 11.05.2010