Design of Rheologically Consistent Artificial Sputum Medium
Hope E. Wolterman, Uranbileg Daalkhaijav, Travis W. Walker
School of Chemical, Biological, and Environmental Engineering, Oregon State University, Corvallis, OR 97331
Background
Cystic Fibrosis:
• Caused by a genetic mutation in the cystic fibrosis
transmembrane conductance regulators (CTFR) gene
• Affects 70,000 people worldwide, 30,000 in the US
• Causes a buildup in the lungs
of viscous mucus
Pseudomonas aeruginosa is a
bacteria commonly found in the
pulmonary system of humans.
In cystic fibrosis patients, it www.bbc.co.uk.
reaches heightened population densities and produces EPS,
which causes a resistance to antibiotics.
Creating Synthetic CF Sputum
The following additives were chosen
initially to mix with the ASM at one
weight percent and tested
• Guar gum (GG)
• Xanthan gum (XG)
• Sodium alginate (SA)
• Locust bean gum (LBG)
After xanthan gum was chosen, it
was mixed with the other gums and
1 wt% xanthan gum
tested. XG turned out to be the best
additive when it was by itself.
Substance
Viscoelastic
CF Sputum
ASM
Guar Gum
Locust Bean Gum
Xanthan Gum
Sodium Alginate
XG+GG
XG+LBG
XG+SA
N
Y
N
N
N
N
N
N
N
Conclusion
Elastically
Dominated
Y
N
Y
N
Y
N
Y
N
Y
Constant Frequency Sweep
Modulus
Y
N
N
N
Y
N
N
N
N
Table 1. Comparison of different properties of CF sputum to
various additives.
Results
Through mixing xanthan gum with ASM, we can now
make a gel rheologically consistent to expelled cystic
fibrosis sputum. After the objectives were obtained,
further research can continue to
attempt to understand how P.
aeruginosa works and how it
moves through the thick, netted
mucus. Because of the mucus’
unique structure as a complex
fluid, we may also get a glimpse
of future ways drugs may be
administered into a body and
transported through the mucus.
www.directindustry.com
Acknowledgements
Normal Airway
Cystic Fibrosis Airway
Travis Walker Research Website
Treatments:
• Gene Therapy
• Chest Physiotherapy
• Lung Transplantation
• Aerosolized Medication
www.nhlbi.nih.gov
Currently, the best treatment for cystic fibrosis (CF) is
through chest physiotherapy. Patients usually take a mucus
thinner; then, percussion therapy is performed to loosen the
mucus so that it can be expelled as phlegm. To study the
infectious bacteria P. aeruginosa, it is grown in artificial
sputum medium (ASM), a low viscosity fluid that acts as a
food source to the bacteria.
Objectives
The main purpose of this project was to model the
rheological properties of CF sputum by mixing ASM with
gums. Making a suitable substitute of CF sputum will help
us to:
• Grow P. aeruginosa on a synthetic substance more
similar to CF sputum than ASM
• Take rheological measurements of grown bacteria
• Study the microrheology of the mucus to better
understand how P. aeruginosa behaves in a CF lung
• Perfect the technique of using the rheometer and testing
the new sputum substitute (ASM+) to get reliable and
repeatable data
Creating a substitute, ASM+, will help the lab collect
valuable research data without having to use extracted CF
sputum for every experiment.
a. Strain amplitude sweep
b. Frequency sweep
c. Flow sweep
Figure 1. Rheology of CF sputum, ASM, and ASM+XG (xanthan gum). (a) A strain amplitude sweep shows loss modulus (G’ ;
open symbols) and storage modulus (G” ; closed symbols) versus percent strain () (=1/s). (b) A frequency sweep shows loss
and storage modulus versus percent frequency () (CF and ASM+XG:  = 1%; ASM:  = 100%). (c) A flow sweep shows
apparent viscosity () versus shear rate ().
Rheology Research Group (Summer 2014
I would like to recognize Annika Gabriel for her help
with this project. I would also like to thank Pete and
Rosalie Johnson, Skip Rochefort, and Travis Walker for
allowing me to have this great opportunity.
Data from Dawson, Wirtz, and Hanes. J. Biol. Chem. 2003
Future Research
Future research concerning the ASM+ will involve two different projects.
Determination of the mechanical and electrochemical properties of P. aeruginosa
biofilm formation in cystic fibrosis sputum
• Exploring the correlation between mechanical changes of the mucosal environment and
the release of quorum sensing molecules by P. aeruginosa can lead to better treatment of
CF and prevention of secondary infections.
• Actively grow bacteria in a double
wall couette while taking
rheological measurements
Cartoon by Uranbileg Daalkhaijav
Determination of the strengths of adhesion interactions and the ability for
penetration of selectively coated micron spheres with mechanically-relevant
synthetic pulmonary mucus
• The aim of this project is to explore interactions of various types of particulates with
excreted biofluids such as mucus, focusing on the differences in pulmonary mucus for
people with CF.
Cartoon by Ming Yang