Medical Design Briefs - May 2021 - 25

Biosensor Measures
Extracellular Hydrogen
Peroxide
Researchers have developed a sensor for measuring concentrations of H2O2
in the vicinity of cell membranes, with nanometerExplanatory sketch of the plasma memresolution. The biosensor
brane anchored nanosensor. (Credit:
Kanazawa University)
consists of a gold nanoparticle with organic molecules attached to it. The whole cluster is designed so that it
anchors easily to the outside of a cell's membrane, which is
exactly where the hydrogen peroxide molecules to be detected
are. As attachment molecules, the scientists used a compound
called 4MPBE, known to have a strong Raman scattering
response: when irradiated by a laser, the molecules consume
some of the laser light's energy.
By measuring the frequency change of the laser light and
plotting the signal strength as a function of this change, a
unique spectrum is obtained - a signature of the 4MPBE molecules. When a 4MPBE molecule reacts with a H2O2 molecule,
its Raman spectrum changes. Based on this principle, by comparing Raman spectra, the researchers were able to obtain an
estimate of the H2O2 concentration near the biosensor.
After developing a calibration procedure for their nanosensor
- relating the H2O2 concentration to a change in Raman spectrum in a quantitative way is not straightforward - the scientists
were able to produce a concentration map with a resolution of
about 700 nm for lung cancer cell samples. Finally, they also succeeded in extending their technique to obtain measurements of
the H2O2 concentration variation across cell membranes.
For more information, visit www.medicaldesignbriefs.com/
roundup/0521/biosensor.
Artificial Pancreas
System Upgraded
with AI Algorithm
A new a reinforcement learning (RL)
based artificial intelligence (AI) algorithm
Fully automated pancreas system using
calculates the amount of
AI. (Credit: Postech)
insulin needed for a diabetic patient and injects it automatically.
To eliminate the inconvenience of calculating and injecting
insulin daily, the research team added a pharmacological concept to reinforcement learning, widely known as the algorithm
of AlphaGo. This method of AI algorithm achieved a mean glucose of 124.72 mg/dL and percentage time in the normal
range of 89.56 percent. Even without inputting the meal
intake, the policy showed performance comparable to that of
conventional artificial pancreas.
The newly developed AI algorithm enables fully automated
blood sugar control without the hassle of inputting meal or
exercise information. The team expects this algorithm to be
extended to other drug-based treatments.
For more information, visit www.medicaldesignbriefs.com/
roundup/0521/pancreas.
Medical Design Briefs, May 2021

Wearable Sensor Measures Lactate
Concentration in Real Time
Researchers have developed a soft and
nonirritating microfluidic sensor for the
Nonirritating materireal-time measurement of lactate concenals are important in
tration in sweat. This wearable device will
the design of wearable sensors used for
help monitor the state of the body during
quantifying lactate
intense physical exercise or work.
levels during exerChemical biomarkers in bodily fluids such
cise. (Credit: Ketut
Subiyanto on Pexels)
as blood, saliva, and sweat are challenging
to quantify with wearable sensors.
The team first focused on the sensing mechanism that they
would employ in the sensor. Most lactate biosensors are made
by immobilizing lactate oxidase (an enzyme) and an appropriate mediator on an electrode. A chemical reaction involving lactate oxidase, the mediator, and free lactate results in the generation of a measurable current between electrodes - current
that is roughly proportional to the concentration of lactate.
The scientists employed a method called electron beam-induced
graft polymerization, by which functional molecules were bonded
to a carbon-based material that can spontaneously bind to the
enzyme. They turned the material into a liquid ink that can be
used to print electrodes.
The team then designed an appropriate system for collecting
sweat and delivering it to the sensor. They achieved this with a
microfluidic sweat collection system made out of polydimethylsiloxane (PDMS); it comprised multiple small inlets, an outlet,
and a chamber for the sensor in between. The detection limits of
the sensor and its operating range for lactate concentrations was
confirmed to be suitable for investigating the lactate threshold.
For more information, visit www.medicaldesignbriefs.com/
roundup/0521/microfluidic.
AI System Enables Contactless
Heart Monitoring
Researchers have developed a new
skill for a smart speaker that for the first
time monitors both regular and irreguA smart speaker acts as
lar heartbeats without physical contact.
a contactless monitor for
The system sends inaudible sounds
both regular and irregufrom the speaker out into a room and,
lar heartbeats. (Credit:
University of Washington)
based on the way the sounds are reflected back to the speaker, it can identify
and monitor individual heartbeats. Because the heartbeat is
such a tiny motion on the chest surface, the team's system uses
machine learning to help the smart speaker locate signals from
both regular and irregular heartbeats.
When the researchers tested this system on healthy participants and hospitalized cardiac patients, the smart speaker
detected heartbeats that closely matched the beats detected by
standard heartbeat monitors.
For this system, the search for heartbeats begins when a person
sits within 1-2 ft in front of the smart speaker. Then the system
plays an inaudible continuous sound, which bounces off the person and returns to the speaker. Based on how the returned sound
has changed, the system can isolate movements on the person -
including the rise and fall of their chest as they breathe.
For more information, visit www.medicaldesignbriefs.com/
roundup/0521/heart.

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Medical Design Briefs - May 2021

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