A spiral sensor sandwich could help patients with traumatic brain injury. The new device allows continuous monitoring of key physiological and biological parameters affected by TBI.

TBI is caused by direct impact or by acceleration alone. Often little can be done to reverse the initial brain damage so clinicians focus on stabilising the patient and preventing further injury due to, for example, insufficient oxygen in the brain. But physiological indices such as brain glucose are commonly assessed only intermittently, even though they are known to affect patient outcomes. This is partly due to the lack of a simple, comprehensive and inexpensive monitoring device. 

The lab-on-a-tube system developed by Chunyan Li and colleagues at the University of Cincinnati, US, comprises a film containing a microchannel sandwiched between two polymer films, one including a pressure sensor and the other containing glucose, oxygen and temperature sensors. The system is rolled into a spiral to form a tube which can be inserted into the brain. The tube is connected to a multimodal monitor, which shows results from the four sensors, and a cerebrospinal fluid drainage bag as the tube can also be used to drain (and monitor) the fluid to lower intracranial pressure. 

Li's device can measure key parameters affected by TBI and could be used to deliver drugs to the brain through the microchannel

The device addresses a vital clinical need since, according to Raj Narayan, a member of the US team, 'the technology for monitoring severely-ill patients is woefully inadequate.' Li's device has several advantages over existing approaches as it is less invasive - only one hole needs to be drilled into the skull - and is less traumatic as its diameter can be adjusted to lie safely in place. It is also cheaper and easier to use than multiple individual sensors. The tube could be used to deliver drugs through the microchannel that delivers calibration solution to the biosensors.

The significance of the device is emphasised by Ross Bullock, a researcher on TBI at the University of Miami, US, who says that multimodality sensors of this type would 'represent a very major step forward in our ability to monitor neurosurgical patients.'

Possible future developments are suggested by Justin Williams, an expert in neurochemistry and neurobiology at the University of Wisconsin-Madison, US, who says that 'the multifaceted fabrication approach makes it possible to integrate numerous other types of sensors as well as electrical stimulation and even drug delivery.'

Having tested its device with patient samples in vitro, the team is now testing the system in vivo. 'We need to pass this translation process,' says Narayan. 'Interactions with tissues are often unanticipated even to those experienced in the field.'

Ziva Whitelock

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