1. Lactate Sensor Design: Smart Gels for Diabetes Pre-screening
Toby Li, Wern Ong, Joseph Sun, Stephanie Wu & Christine Zhang
Advisors: Franz Baudenbacher, Ph.D. & Paul King, Ph.D.
Biomedical Engineering, Vanderbilt University , Nashville, TN, 37235
Introduction
Methods
Methods
Mix hydrogel ingredients together using proper volumetric ratios
Set polymerizing solution into capillary tubes
Wait overnight for the hydrogel to fully set in the capillary tubes
Isolate capillary tubes to prevent hydrogels from drying out
Soak hydrogel with lactate solution and measure volumetric swelling
Purpose
Design and develop a diabetes pre-screening device to fill market void
Background
Cost of diabetes (direct/indirect) per person = $11,744 per year
Cost of diabetes over lifetime (33 yrs) = $387,552 per person4
Cheap, non-invasive, accurate, and easy to use device is needed for large scale pre-screening and diabetes prevention
Solution
Develop hydrogel based lactate sensor that is sensitive to saliva lactate levels
Volumetric change (directional swelling) of hydrogel polymer caused by saliva lactate concentration is correlated to blood lactate levels
Correlation of lactate concentration to development of type-II diabetes
If test is positive, patients can take steps to prevent development of the disease including changes to diet and exercise
Design 1
Design 2
Figure 3. Diagram illustrating the inputs and outputs of the hydrogel lactate sensor system.
Figure 4. Different design approaches. Design 1 utilizes the direct volumetric change caused by swelling. The volumetric change caused by directional swelling is extremely small and difficult to measure. Design 2 amplifies the change in volume for more accurate and sensitive readouts.
Conclusion
Diabetes
Hygienic, non-invasive, disposable, uniform, and cheap lactate sensor
Small and varied volumetric change due to non-uniform directional swelling, bubbles, and limited reaction area
Hydrogel polymer not sensitive to small lactate concentrations resulting in low resolution and difficulty making accurate measurements
Results
Diabetes:
Chronic illness
Characterized by high blood sugar
Caused by insufficient insulin levels
Body has become resistant to insulin
Medical expenditure of diabetics is 2.3x higher than non-diabetics
[Lactate] pH
0.2 mmol
4.5
0.3 mmol
0.4 mmol
4.0
0.5 mmol
3.5
1 mmol
3.0
5 mmol
100 mmol
2.5
Acetic Acid
2.0
A1C Test
Measure Glycated Hemoglobin
$20-$30
Needle Prick
Average over 6 weeks
Lab/Home Setting
Varied Results
Fasting Plasma Glucose Test
Measure Plasma Glucose
Low Cost
Draw Blood
12-14 hr Fasting
Lab Setting
May not identify pre-diabetes
Oral Glucose Tolerance Test
Measure Blood Glucose
Expensive
Complaints Nausea
Fasting + 4 hrs for Results
Accurate Results
Smart Gel Lactate Sensor
Measure Saliva Lactate Concentration
Low Cost: $0.29
Non-invasive
1 hr
Self Testing
Figure 5. Shows the response of different hydrogel configurations to an acidic solution.
Figure 1. Prevalence of diabetes in the population.
Risk Factors:
Age
Ethnicity
Weight
Family History Other Symptoms
Complications:
Heart Disease/Stroke
High Blood Pressure
Blindness
Kidney Disease
Nervous System Disease
Amputation
Future Considerations
Use of more sophisticated fabrication techniques including the use of sonication in order to produce more sensitive polymer and more accurate readouts
Use of other measurement techniques such as the Q ratio in order to measure small effects of lactate oxidase on the hydrogel polymer
Introduction of a colorimetric assay as a means of internal control
Establishing testing protocols for use of this device in public health settings
Background
Figure 6. Hydrogel response to different Lactate concentrations using Design 1.
Figure 7. Hydrogels of different lactate oxidase configurations and their response to different solutions.
References
Polymer
Cost ($)
HEMA
0.33
DMAEMA
1.80
TEGDMA
0.10 EG
0.42
Water
0.00
Ammonium Persulfate
0.02
Sodium Bisulfite
0.01
Total
2.67
Number Tubes 74
Gel Costs
$2.67
LOD costs
$17.48
Total Costs
$21.11
Cost per Tube
$0.29
Traitel, Tamar. "Characterization of Glucose-sensitive Insulin Release Systems in Simulated in Vivo Conditions." Biomaterials (2000): Print.
Segura, R. "A New Approach to the Assessment of Anaerobic Metabolism: Measurement of Lactate in Saliva." Journal of Sports Medicine (1996): Print.
Crawford, Stephen O. "Association of Blood Lactate with Type 2 Diabetes: the Ahterosclerosis Risk in Communities Carotid MRI Study." International Journal of Epidemiology (2010): Print.
American Diabetes Association. "Economic Costs of Diabetes in the U.S. in 2007." Diabetes Care (2008): Print.
Figure 2. Shows the correlation of saliva lactate levels to lactate levels in the blood3.
Figure 3. Correlates lactate levels in the blood to the probability of developing type-II diabetes2.
Figure 8. Financial analysis of the cost of production including material costs.