posted on 2023-01-04, 13:06authored byKai-Chiang Yu, Chun-Yao Hsu, Gurpur Rakesh D. Prabhu, Hsien-Yi Chiu, Pawel L. Urban
Skin metabolites show huge potential for use in clinical
diagnostics.
However, skin sampling and analysis workflows are tedious and time-consuming.
Here, we demonstrate a vending-machine-style skin excretion sensing
platform based on hydrogel-assisted sampling of skin metabolites.
In this sensing platform, a sampling probe with hydrogel is held by
a robotic arm. The robotic arm manoeuvres the probe to press it onto
the forearm of a human subject. Due to the highly hydrophilic nature
of the hydrogel, water-soluble metabolitesreleased by skinare
collected into the hydrogel, leaving behind the nonpolar metabolites.
The probe is then inserted into a custom-made open port sampling interface
coupled to an electrospray ion source of a high-resolution quadrupole-time-of-flight
mass spectrometer. Metabolites in the hydrogel are immediately extracted
by a solvent liquid junction in the interface and analyzed using the
mass spectrometer. The ion current of the target analyte is displayed
on a customized graphical user interface, which can also be used to
control the key components of the analytical platform. The automated
sampling and analysis workflow starts after the user inserts coins
or presents an insurance card, presses a button, and extends an arm
on the sampling area. The platform relies on low-cost mechanical and
electronic modules (a robotic arm, a single-board computer, and two
microcontroller boards). The limits of detection for standard analytesarginine,
citrulline, and histidineembedded in agarose gel beds were
148, 205, and 199 nM, respectively. Various low-molecular-weight metabolites
from human skin have been identified with the high-resolution mass
spectrometer.