Researchers at the University of Connecticut have developed an ultrasound implant that can assist in opening the blood brain barrier to allow chemotherapy to enter and treat brain cancer. However, unlike cumbersome ultrasound systems, this technology can be implanted directly into the brain, and does not require a follow-up surgery to remove the device later as it degrades away to nothing in the brain over time. The implant contains crystals of the amino acid glycine, which has been shown to be strongly piezoelectric, meaning that it vibrates when an electrical current is passed through it. The researchers combined this with biodegradable polymers to create the ultrasound implant, which can be seen in the image above.
The usual procedure when a brain tumor is identified involves surgical removal followed by chemotherapy to remove any residual cancer cells. However, delivering chemotherapy to the brain is notoriously difficult, with the specialized endothelium lining the blood vessels of the brain, otherwise known as the blood-brain barrier, preventing the entry of many common chemotherapy drugs.
One method to trespass across the blood-brain barrier is to use ultrasound to create transient gaps in the barrier, allowing the drug to enter. However, this has traditionally been quite cumbersome, with the need for several powerful ultrasound devices to be placed on the head and a duration of 5-6 hours for the procedure. These factors significantly limit how often such patients can avail of ultrasound-enhanced chemotherapy.
Implantable ultrasound transmitters have been developed, but so far these have been made using ceramics and require a second surgery to remove the device later. To address this, these researchers have created an ultrasound implant that is completely biodegradable, but which maintains the same power and efficacy as ceramic devices. “We can avoid all of that by using an implanted device” within the brain itself,” said Thanh Nguyen, a researcher involved in the study. “We can repeatedly use it, allowing chemo to penetrate the brain and kill off tumor cells.”
The new device is made using piezoelectric glycine crystals. On their own, the crystals would biodegrade too quickly and would be far too brittle, so the researchers combined them through an electrospinning process with a biodegradable polymer called polycaprolactone and another called Poly-L-Lactide. These polymers help to extend the life of the ultrasound emitter within the brain.
In tests with mice with brain tumors, using the ultrasound device in combination with chemo doubled the survival of the mice compared with untreated mice.
Study in journal Science Advances: Highly piezoelectric, biodegradable and flexible amino acid nanofibers for medical applications
