Vending-Machine-Style Skin Excretion Sensing

Abstract

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 metabolitesreleased by skinare 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 analytesarginine, citrulline, and histidineembedded 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.

Automation and Computerization of (Bio)sensing Systems

“…In recent times, biocompatible agarose hydrogel is being utilized for manual sampling of human sweat and skin excretions. , However, it should be noted that although manual sample collection from human skin using hydrogels is simple, the desorption or re-extraction of analytes from the hydrogels and its subsequent detection require skill and expertise. In order to address this limitation, Yu et al developed a vending-machine-style skin excretion sensing platform, which serves to automate the sampling and analysis of human sweat and skin excretion . In this automatic sensing platform, the robotic arm picks up a hydrogel probe and collects the sample from the forearm (Figure -III-A).…”

“…(III-B) Illustration of OPSI working principle. Reprinted with permission from ref ( 116 ). Copyright 2023 American Chemical Society.…”

Mass Specthoscope: A Hand-held Extendable Probe for Localized Noninvasive Sampling of Skin Volatome for Online Analysis

“…Hand-held probes were also applied to detect pesticide residues on solid surfaces of fruits and vegetables, in different detection modes (ambient MS, biochemiluminescence). The efficacy of employing a hand-held aspirating probe for the sampling and transfer of concentrated VOCs to an ion-mobility spectrometry analyzer has been demonstrated in previous studies. , Another study demonstrated a vending-machine-style device that employs a robotic arm to sample analytes from the skin using hydrogel probes . A robotized probe was also coupled with MS for chemical mapping of VOCs in solid specimens …”

“…32,33 Another study demonstrated a vending-machine-style device that employs a robotic arm to sample analytes from the skin using hydrogel probes. 34 A robotized probe was also coupled with MS for chemical mapping of VOCs in solid specimens. 35 There is no universally accepted standard technique for analyzing VOCs from the skin's surface.…”

The Three Laws of Nano-Robotics

“…From the manufacturing tools used on the factory floor, to the inventory control devices used in commercial warehouses, even to the vacuum cleaners used in our homes, robots are deeply embedded in our daily lives. Modern analytical and clinical laboratories are critically dependent on robotic instrumentation for high-throughput analyses, and readers of ACS Sensors have begun to see how integration of the wide range of chemical and biological sensors into robots will massively expand the capabilities of these systems. − As miniaturization and nanotechnological tools have evolved, the shrinking of these robots and their sensory systems to the nanoscale has brought its own set of promises and challenges.…”