Imperial College spots brain injury complications to assist clinical care

10 Dec 2024

Platform using specialized optical fibers tracks six biomarkers simultaneously.

Monitoring the condition of patients after a traumatic brain injury (TBI) is a vital factor in their recovery, since secondary damage from swelling in the brain is both possible and potentially dangerous.

Traditional brain monitoring techniques such as EEG and intracranial pressure measurements are now increasingly being joined by optical instruments, able to assess the key blood flow parameters.

A project at Imperial College London has now developed a new optical fiber sensing system that could offer further assistance to clinicians monitoring TBI recovery. The study was published in ACS Sensors.

"Biomarkers found in blood or spinal fluid provide medical professionals with information on brain health," commented the Imperial team in its paper. "However, current challenges remain in insufficient temporal resolution and limited biomarker numbers and types that can be monitored."

In clinical settings continuous monitoring of several biomarkers is more desirable for precise and accurate disease diagnosis and treatment, so this limitation of current systems is a significant problem.

The project at Imperial's Centre for Biochemical Sensors set out to create an optical fiber system that would concurrently monitor six key brain health biomarkers: temperature, pH, and concentrations of dissolved oxygen, glucose, sodium ions and calcium ions.

It built on previous work at Imperial studying how functionalizing different sensing probes on a single reflection optic fiber tip brought a multiplexing capability to the optical analysis. This earlier study had demonstrated the detection of four biomarkers in artificial cerbrospinal fluid, a number the project now aimed to surpass.

Enormous potential of multiplexed optical fiber sensing

The team designed an optical bundle in which six fluorescent sensing films, each made from a fluroescent probe encapsulated in polymer film, were present on the fiber tips. These six fibers, along with an extra fiber to boost the calcium signal's measurement, were incorporated into a 2.5-millimeter-thick catheter to create a cerebrospinal fluid sensing system.

A purpose-designed multi-wavelength laser was shone through the fibers, and the change in brightness when a target analyte interacted with the appropriate fluorescent tip was recorded. Algorithms driven by machine learning then detangled the fluorescence signals from one another, providing an easy readout of each biomarker.

"Typically, each optical fiber sensor necessitates one spectrometer and one laser/LED for measurement, resulting in the requirement of six lasers and six spectrometers for monitoring the six biomarkers," noted the project in its paper.

"Our design optimizes the system by incorporating six optical fiber sensors with either different excitation or emission wavelengths, bundled together. This reduces the requirement to only one spectrometer and one switchable multiwavelength laser source for monitoring all six biomarkers."

In trials, the catheter sensing system first successfully detected the six biomarkers in an experiment with animal brains designed to mimic the conditions of the human brain after a traumatic injury. The platform was then applied to cerebrospinal fluid samples collected from healthy human participants and spiked with the brain health biomarkers of interest.

The system accurately determined pH, temperature and dissolved oxygen level in these samples and identified changes in the concentrations of the ions and glucose. This showed that the optical fiber system can detect when a secondary injury might be imminent, and could help monitor complications from these traumatic injuries in patients.

"These findings underscore the enormous potential of automated and multiplexed optical fiber sensing systems for intraoperative and postoperative monitoring of brain physiologies," said the Imperial team.