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Cancer Technologies

In vitro Assessment of Bacterial Swimming in Simulated Breast Cancer Microenvironments 

(F-212) In vitro Assessment of Bacterial Swimming in Simulated Breast Cancer Microenvironments 

Saturday, October 14, 2023

9:30 AM – 10:30 AM PDT

Location: Exhibit Hall - Row F - Poster # 212

Presenting Author(s)

Izabela Kowalik, UG

Research Associate
National High Magnetic Field Lab
Land O' Lakes, Florida, United States

Co-Author(s)

SJ

Sophie Jermyn

Ph.D.
FAMU-FSU College of Engineering, United States
Astrid Daugherty (she/her/hers)

Research Associate
FAMU-FSU College of Engineering
Tallahassee, Florida, United States
MA

Makena Andersen

Research Associate
Lewis & Clark College, Department of Chemistry & Physics
Tallahassee, Florida, United States
AM

Amisha Martin

Research Associate
FAMU-FSU College of Engineering, United States
JK

Jaideep Katuri

Postdoctoral Fellow
FAMU-FSU College of Engineering, United States

Last Author(s)

JA

Jamel Ali

Professor
FAMU-FSU College of Engineering, Florida, United States

Introduction::

Bacteria-based cancer therapy is an evolving practice that has the potential to be an effective and economical form of cancer treatment. Recent preliminary clinical trials have demonstrated the ability of genetically modified motile bacteria to attack and deliver medication to cancerous micro-environments while maintaining the health of patients. However, there is still much that is unknown about the mechanisms, reliability, and side effects of live bacterial therapeutics. To gain insight into these therapeutic bacteria and their function and behavior in vivo, it is crucial to understand their locomotion in different complex environments that simulate the microenvironments that exist in the body. The aim of this study is to understand the effects of increased fluid viscosity and viscoelasticity on bacterial motility and chemotaxis. It is theorized that with living objects at the microscale, viscoelasticity can have a significant effect on swimming velocity with fluid viscosity suppressing cell tumbling, and fluid elasticity increasing cell velocity.

Materials and Methods::

Bacterial motility was assessed by placing flagellated wild type Salmonella Typhimurium into five different polymer solutions with varying viscosities, mimicking the cancer microenvironment. The S. Typhimurium was pelleted and pipetted into different polymer solutions and left for 10 minutes to diffuse. Bacteria were then viewed under an inverted microscope with a 40X (0.75 N.A.) phase contrast objective. Motility in dilute polymer solutions, mimicking various simulated breast cancer microenvironments, included measurements in 1% methylcellulose (15kDa), 0.2% methylcellulose (44kDa), 0.2% methylcellulose (88kDa), 0.075% Xanthan Gum (5,000-6,000kDa), and 0.25% Polyacrylamide (2,000kDa). For the analysis of bacterial motility, phase contrast microscopy (PCM) was utilized. The swimming trajectories were analyzed in the ImageJ TrackMate plugin to find the resulting velocities. The scales of velocity were averaged using Prism GraphPad and Python.

Results, Conclusions, and Discussions::

Results and Discussion: Bacterial motility in a control buffer solution yielded an average swimming velocity of 6.94 µm/s (Fig.1A), in line with previously reported results. There was a significant drop in motility in the 15kDa methylcellulose fluid, indicating that viscous drag attenuates flagellar motility at this concentration of specific polymer.  Interestingly, the results of this experiment showed that S. Typhimurium moved the fastest in 88kDa methylcellulose, with an average speed of 10.17 µm/s. (Fig.1A) This result aligns with other experiments and theories that have reported swimming enhancement in certain viscoelastic conditions. Swimming velocity was also attenuated in the chosen concentrations of xanthan gum (XG), a highly shear thinning fluid, and polyacrylamide (PA), a fluid with distinct elasticity. The observed decrease in XG and PA solutions may be due to the polymer concentrations being too high (Fig. 1B). A number of groups have proposed many theories as to why some bacteria move faster in certain biological fluid environments.  One popular theory involves the kinematics of the helical bacterial flagella. These flagella aren't completely aligned with the bacterial body causing them to move in helical forms which under a microscope make the salmonella appear to be moving side to side. When S. Typhimurium is dispersed into a fluid with a higher viscosity, the flagella encounter particles that force it to undergo a boundary induced torque. This torque diminishes the misalignments between the body and flagella of the bacteria, reducing the wobbling angle of the swimmer and increasing their linear velocity.

Conclusion: Dilute polymer solutions with varying viscosities that mimic the cancer microenvironment can in some cases significantly enhance the motility and chemotaxis of therapeutic bacteria. We characterized the motility behavior of S. Typhimurium in different viscoelastic environments.  These experiments are critical for the development of therapeutic motile S. Typhimurium in the human body. The movement of S. Typhimurium in different polymer fluids mimics in vivo cancerous microenvironments allowing development for better medication delivery and targeting abilities. Future experiments still must be conducted by co-culturing S. Typhimurium alongside MDA cells to analyze rheotaxis, and chemotaxis in the presence of cancer cells. 

Acknowledgements (Optional): :

This work was funded by the National Science Foundation (No. EES-2000202, CMMI-2000330, EES-2219558) and supported by Dow. This research work was also supported by The Grainger Foundation Frontiers of Engineering Grant under the National Academy of Sciences Award Number: 2000013181. All the work was performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreement No. DMR-1644779 and the State of Florida. The content is solely the responsibility of the authors and does not necessarily represent the official views of The Grainger Foundation or the National Academy of Sciences.

References (Optional): :