New Delhi, September 24, 2016: (UNI) Magnetic bacteria are a promising vehicle for more efficiently delivering tumour-fighting drugs, according to the results of a research published in Nature Nanotechnology.
One of the biggest challenges in cancer therapy is being able to sufficiently deliver chemotherapy drugs to tumours without exposing healthy tissues to their toxic effects.
One way researchers have attempted to overcome this is by developing nano-carriers – microscopic particles packed with drugs.
The nano-carriers are designed so they’re only taken up by cancer cells, thereby preventing the drugs from being absorbed by healthy tissues as they travel through the body’s circulation.
Yet while nano-carriers do a good job protecting healthy tissues, the amount of drug successfully delivered to tumours remains low.
The main reasons for this shortcoming are that nano-carriers rely on the circulation system to carry them to the tumour, so a large percentage are filtered out of the body before ever reaching their destination.
In addition, differences in pressure between the tumour and its surrounding tissue prevent nano-carriers from penetrating deep inside the tumour.
As a result, nano-carriers aren’t able to reach the tumour’s hypoxic zones, which are regions of active cell division that are characterised by low oxygen content and from where the cancer spreads to other parts of the body.
“Therefore, targeting the low-oxygen regions will most likely decrease the rate of metastasis (spread of cancer) while maximising the effect of a therapy,” says Sylvain Martel, Director of the Polytechnique Montréal NanoRobotics Laboratory and lead researcher of the study.
Martel and his research team were attempting to develop robotic nanocarriers that would travel to hypoxic zones when they realized nature may have already created one in the form of a bacteria called magnetococcus marinus or MC-1 which thrive in deep waters where oxygen is sparse.
In order to find these areas, the bacteria rely on a two-part navigation system.
The first part involves a chain of magnetic nano-crystals within MC-1 that acts like a compass needle and causes the bacteria to swim in a north direction when in the Northern Hemisphere.
The second part consists of sensors that allow the bacteria to detect changes in oxygen levels.
This unique navigation system helps the bacteria migrate to and maintain their position at areas of low oxygen.
In an initial experiment, mice that had been given human colorectal tumours were injected with either live MC-1 cells, dead MC-1 cells, or non-magnetic beads (roughly the same size as the bacteria).
The injection was made into the tissue directly adjacent to the tumours after which the mice were exposed to a computer-programmed magnetic field, meant to direct the cells or beads into the tumour.
Upon examination of the tumours, the researchers found minimal penetration of the dead bacterial cells and the beads into the tumour, whereas the live bacterial cells were found deep within the tumour and especially in regions with low oxygen content.
“When they get inside the tumour, we switch off the magnetic field and the bacteria automatically rely on the oxygen sensors to seek out the hypoxic areas,” says Martel.
Next, the researchers wanted to see whether attaching vesicles loaded with drugs to the cells would affect their movement into the tumours.
They attached approximately 70 drug-containing vesicles to each bacterial cell.
The cells were then injected into another set of mice with colorectal tumours and exposed to the magnet.
After examining the tumours of those mice, the researchers estimated that on average, 55 per cent of the injected bacterial cells with attached vesicles made it into the tumour.
For comparison, some researchers estimate that only approximately two per cent of drugs delivered via current nano-carriers make it into tumours.
The next step for Martel’s team is to determine the effects of the drug-loaded bacterial cells on reducing tumour size.
They would also like to test whether the bacteria can be used to deliver other types of cancer-killing medicines such as molecules that instruct the immune system to attack tumours.
“These bacteria are really the perfect machine (because) they replicate, they’re cheap, and we can inject hundreds of millions or more at a time,” says Martel. UNI YSG PY PR0815
United News of India
