According to the team at University of California San Diego, its skin patch could give medical professionals unprecedented access to crucial information that could help spot life-threatening conditions such as malignant tumours, organ dysfunction, cerebral or gut haemorrhages and more.
“The amount and location of haemoglobin in the body provide critical information about blood perfusion or accumulation in specific locations. Our device shows great potential in close monitoring of high-risk groups, enabling timely interventions at urgent moments,” said Sheng Xu, a professor of nanoengineering at UC San Diego and corresponding author of the study.
Low blood perfusion inside the body may cause severe organ dysfunctions and is associated with a range of ailments, including heart attacks and vascular diseases of the extremities.
At the same time, abnormal blood accumulation in areas such as in the brain, abdomen or cysts can indicate cerebral or visceral haemorrhage or malignant tumours. Continuous monitoring can aid diagnosis of these conditions and help facilitate timely and potentially life-saving interventions.
Researchers believe that their new sensor can overcome significant limitations in existing methods of monitoring biomolecules.
Magnetic resonance imaging (MRI) and X-ray-computed tomography rely on bulky equipment that can be hard to procure and usually only provide information on the immediate status of the molecule, which makes them unsuitable for long-term biomolecule monitoring, they said.
“Continuous monitoring is critical for timely interventions to prevent life-threatening conditions from worsening quickly,” said Xiangjun Chen, a nanoengineering PhD student in the Xu group and study co-author.
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“Wearable devices based on electrochemistry for biomolecules detection, not limited to haemoglobin, are good candidates for long-term wearable monitoring applications. However, the existing technologies only achieve the ability of skin-surface detection.”
The flexible low form-factor wearable patch comfortably attaches to the skin according to the team, allowing for non-invasive long-term monitoring. It can reportedly perform three-dimensional mapping of haemoglobin with a submillimetre spatial resolution in deep tissues down to centimetres below the skin.
Due to its optical selectivity, it can expand the range of detectable molecules, integrating different laser diodes with different wavelengths, along with its potential clinical applications.
The patch is equipped with arrays of laser diodes and piezoelectric transducers in its soft silicone polymer matrix. Laser diodes emit pulsed lasers into the tissues. Biomolecules in the tissue absorb the optical energy and radiate acoustic waves into surrounding media.
“Piezoelectric transducers receive the acoustic waves, which are processed in an electrical system to reconstruct the spatial mapping of the wave-emitting biomolecules”, said Xiaoxiang Gao, a postdoctoral researcher in Xu’s lab and co-author of the study.
Hongjie Hu, another postdoctoral researcher in the group and study co-author said that due to its low-power laser pulses, it is also much safer than X-ray techniques that have ionising radiation.
The team now plans to further develop the device, including shrinking the backend controlling system to a portable-sized device for laser diode driving and data acquisition, expanding flexibility and potential clinical utility. They also plan to explore the wearable’s potential for core temperature monitoring.
“Because the photoacoustic signal amplitude is proportional to the temperature, we have demonstrated core temperature monitoring on ex-vivo experiments,” Xu said. “However, validating the core temperature monitoring on the human body requires interventional calibration.”
They are continuing to work with physicians to pursue more potential clinical applications. Their work is published in Nature Communications.
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