Microfluidic Device for the Detection of V. cholerae in Drinking - PowerPoint PPT Presentation

Microfluidic Device for the Detection of V. cholerae in Drinking Water Cholera Microbusters, Inc. CEO: Dr. Orlin Velev Designers: Jeffrey Millman, Katherine Schadel, Chris Shaul, Lao Yang

Overview � Goal and Motivation � Cholera: Cause and Detection � Available Detection Tools � Silver Enhancement Technique � The Microfluidic Advantage � Device Concept � Optimization of Design Features � Future Challenges Cholera Microbusters, Inc.

Goal � To design a small, accurate, and inexpensive microfluidic device for the detection of cholera � Help local health officials identify outbreaks � Provide residents and travelers with an affordable, discrete, and quick means of assessing risk Cholera Microbusters, Inc.

Motivation Cholera � Fatal if not promptly treated � Predominant in Asia, Africa, Latin America � Mass infections in refugee camps and after natural disasters IV drip treatment of cholera victims at � Problematic in tropical a refugee camp in Mozambique. areas popular with [ Medecins Sans Frontiers/Doctors Without Borders ] http://www.designthatmatters.org/proto_portfolio/cholera_t tourists reatment/multimedia/msf_moz_cholera_camp.jpg Cholera Microbusters, Inc.

Motivation: Scope of the Problem http://www.die-reisemedizin.de/data/krankheiten/images/cholera.jpg Cholera Microbusters, Inc.

Cholera: Cause and Detection � Vibrio cholerae � Aquatic bacterium � Cholera toxin (CT) � Chlorine ion imbalance � Severe dehydration � Resistant to Vibrio cholerae vaccination and http://www.crystalinks.com/cholera.jpg antibiotics � Most devices detect CT only Cholera Microbusters, Inc.

Available Detection Tools � Naturally Specific Antibodies � Labeling � Fluorescent markers � Gold colloids Immunoassay with Gold-Colloid Labeling Courtesy Shalini Gupta, NCSU chemical engineering graduate student Cholera Microbusters, Inc.

Commercially Available Device � The SMART � Gold-Labeled Antibodies Limit of detection 6 million cells � per mL � Portable � External Requirements Buffer � Reaction vial � The SMART by New Horizons Eyedroppers � Diagnostic Corporation (Columbia Swabs � Maryland, USA) http://www.nhdiag.com/cholera_bt.shtml Cholera Microbusters, Inc.

Silver Enhancement Technique � Amplified level of detection � Implemented on microfluidic devices recently Immunoassay with Gold Labeling � No known and Silver-Enhancement environmental or safety Courtesy Shalini Gupta, NCSU chemical engineering graduate student hazards Cholera Microbusters, Inc.

The Microfluidic Advantage Microchannel Prototype � Smaller devices RNA � Drastically reduced Fingerprinting reagent volumes � Decreased waste DNA Assays Examples of previously developed microfluidic devices currently on the market. Courtesy Dr. Orlin Velev, NCSU chemical engineering professor Cholera Microbusters, Inc.

Device Concept Credit-card-sized Assay and diagnostic device result with reagent and Sample reaction chambers collection Cholera Microbusters, Inc.

Device Considerations � Polydimethylsiloxane (PDMS) Rubber � Elastomer � Antibody binding techniques studied � Ease of microfabrication � Finger-Actuated Micro- The importance of rounded Pump chambers. (Ahn et al . 2004) � Sample collector � Reagent dispenser Cholera Microbusters, Inc.

Finger-Actuated Micro-Pump Optimization � Purpose Chamber Wall � Determine effective volume Chamber � Deliver sufficient volume � Constraints on Diameter � Large enough to be easily handled � Small enough to fit on a Finger-Actuated Micro-Pump microfluidic device Cholera Microbusters, Inc.

Theoretical Analysis Chamber Wall Chamber Wall Dead Volume Dead Volume Effective Volume Effective Volume Chamber with Elastic Top Chamber with Elastic Top and and Bottom Rigid Bottom ⎡ ⎤ ⎛ ⎞ + + 2 2 R rR r ⎜ ⎟ = π − ⎢ 2 ⎥ V d h R ⎜ ⎟ ⎝ ⎠ ⎣ 3 ⎦ Cholera Microbusters, Inc.

Theoretical Analysis 80 60 % Dead Volume 40 20 0 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 Diameter (inches) � Percent dead volume decreases as diameter increases � Not a function of height Cholera Microbusters, Inc.

Experimental Analysis � Two Scenarios � Sample collector � Reagent dispenser � Constructed from Silicone Rubber � Independent Variables � Diameter � Thickness All numbers in millimeters Cholera Microbusters, Inc.

Reagent Dispenser Experimental Data Height 80.0% 0.0625 inches 0.0313 inches 0.0200 inches 60.0% % Dead Volume 40.0% 20.0% 0.0% 0.3 0.5 0.7 0.9 1.1 Diameter (inches) � Percent dead volume decreases as diameter increases � Not a clear function of height Cholera Microbusters, Inc.

Sample Collector Experimental Data 80.0% 60.0% % Dead Volume 40.0% Height 0.0625 inches 20.0% 0.0313 inches 0.0200 inches 0.0% 0.3 0.5 0.7 0.9 1.1 Diameter (inches) � Percent dead volume increases as diameter increases � Not a clear function of height Cholera Microbusters, Inc.

Chamber Optimization Results � Sample Collector � 1-inch diameter � Larger size because of higher percent dead volume � Reagent Dispenser � 0.625-inch diameter � Smaller size because of lower percent dead volume � Smaller amount of reagents � Height � 0.0625-inch � No effect on dead volume � Greater total volume Cholera Microbusters, Inc.

Channel Sizing Optimization � Guiding Principles � Low fill-up time of about 1 second � Manufacturing costs � Device size � Method � Extrapolation from experimental data � Mechanical energy balance with estimates of frictional terms (length, expansions, contractions, bends) Cholera Microbusters, Inc.

Channel Sizing Optimization 6 5 Fill-up Time (s) 4 3 2 1 0 0.4 0.6 0.8 1 1.2 1.4 1.6 Channel Width (mm) Optimal channel width of 1 mm Cholera Microbusters, Inc.

Five-Pump Design All numbers in millimeters Cholera Microbusters, Inc.

Cholera Microbusters, Inc. Five-Pump Design

Cholera Microbusters, Inc. Five-Pump Design

Conclusions � Finger-actuated � No external requirements � Portable � Disposable � Smaller, simpler alternative to commercially available options Cholera Microbusters, Inc.

Future Challenges � Final device selection � Build prototype � Operating procedure � Valve system to prevent backflow � Economic analysis Cholera Microbusters, Inc.

Acknowledgements Dr. Orlin Velev’s research group, for their help and access to laboratory equipment Dr. Lisa Bullard, for her advice and http://xenafan.com/movies/ assistance ghostbusters/egonfiring.jpg Cholera Microbusters, Inc.