We have all heard of Concorde aircrafts, which can fly faster than sound. When flying at max speed, these aircrafts generate what is called a 'shock wave' – a kind of disturbance that occurs in nature when a body is moving faster than sound. Imagine the high energy generated! Now imagine harnessing that energy to kill off micro-organisms.
Scientists from the Indian Institute of Science have attempted, for the first time, to use shock waves to treat biofilm infections in living organisms – things like tooth decay and sinusities, which involve a layer of micro-organisms growing on a living surface.
Shock waves are defined by very large variations in pressure and temperature over a thin region. In general, shock waves occur naturally in the environment as a result of explosions, lightning or earthquakes. They can also be created artificially in what are called 'shock tubes'.
Of primary interest to aerospace engineers, these waves are now being explored in bioengineering as a form of non-invasive treatment. This study describes the use of shock waves to get rid of slimy layers of micro-organisms called biofilms. “Biofilms are essentially densely packed bacterial communities that grow on living or inert surfaces. When they are formed inside the body, they cause inflammation and tissue damage,” explains Jagadeesh Gopalan, a Professor at the Department of Aerospace Engineering at IISc, Bangalore and one of the authors of this paper.
Gopalan collaborated with Dipshikha Chakravortty from the Department of Microbiology and Cell Biology, also at IISc, to use the shock waves from aerospace to tackle a microbial infection. Shock waves have already been successfully used as a non-invasive technique of drug delivery, vaccinations and kidney stone removal.
Besides living surfaces, biofilms can even form on non-living things such as catheters and prosthetic joints. Infection-causing bacterial biofilms are generally better than free-floating bacteria at combating the immune system of our body, causing infection to stay longer. They are also more resistant to antibiotic treatments.
Antibiotics can only work very slowly on biofilm. “It is generally very difficult to disrupt the biofilm,” says Gopalan. “If there’s a space between the biofilm, only then the antibiotic can work. Otherwise, biofilm tend to live together and breathe together and can be very hard to disrupt.”
While most previous experiments of shock wave treatment on biofilm have involved external, artificial environments, this study has attempted to treat biofilm using shock waves in vivo i.e. in a living organism. The shock waves used for treatment were of low energy and repeatable.
In this experiment, the researchers bred biofilm on a urinary catheter and exposed it to a hand-held shock wave generator, a portable technology developed by the researchers themselves. This successfully disrupted the biofilm on the catheter.
In further experiments, the researchers used shock tubes to deliver shock waves to mice with a lung infection. One end of the tube had the mice, and the entire body was exposed to the shock wave. These mice were also treated with antibiotics, and in a matter of three days, the researchers found that the number of bacteria in the biofilm had significantly reduced in the shock wave treated mice, compared to a control group.
“This study has major implications,” explains Janardhanraj, a post-doctoral scholar working in the Department of Aerospace Engineering at IISc and one of the researchers in the study, “It shows us that using shock waves along with antibiotics can treat several lung and skin infections caused by bacteria.”
Based on these findings, the researchers have already begun developing treatment techniques using shock waves for infected living organisms that can be used in tandem with antibiotic treatment.
About the paper
Jagadeesh Gopalan is a Professor in the Department of Aerospace Engineering at IISc, Bangalore. Dipshikha Chakravortty is a Professor at the Department of Microbiology and Cell Biology, Indian Institute of Science. Divya Prakash Gnanadhas was a joint student, presently a post doctoral fellow at University of Nebraska Medical Center.Janardhanraj is a post-doctoral scholar working with Gopalan. Monalisha Elango, C. S. Srinandan and Akshay Datey are research scholars at the Department of Microbiology and Cell Biology.
Collaborator Richard A. Strugnell is at the Department of Microbiology and Immunology, The Peter Doherty Centre for Infection and Immunity at The University of Melbourne, Australia.
Jagadeesh Gopalan: firstname.lastname@example.org
Dipshikha Chakravortty: email@example.com
The paper appeared in the journal Scientific Reports, published by the Nature Publishing Group, earlier this month.