Latest article by Hossam Haick:Appears to be a method to achieve...

Latest article by Hossam Haick:
Appears to be a method to achieve high levels of consistency when manufacturing their gold nanoparticle sensors. Strange that it mentions using these sensors for cancer detection but not for COVID. It also gives an indication of other possible applications of these sensors (ie. monitoring of diagnostic markers in body fluids (link to Biotome partnership???), explosive materials, environmental contaminations and food quality control).
Hopefully one of the last problems they had to solve before mass-production of breathalyzers can be achieved

https://www.nature.com/articles/s41596-021-00528-y

Abstract

Chemiresistors that are based on monolayer-capped metal nanoparticles (MCNPs) have been used in a wide variety of innovative sensing applications, including detection and monitoring of diagnostic markers in body fluids, explosive materials, environmental contaminations and food quality control. The sensing mechanism is based on reversible swelling or aggregation and/or changes in dielectric constant of the MCNPs. In this protocol, we describe a procedure for producing MCNP-based chemiresistive sensors that is reproducible from device to device and from batch to batch. The approach relies on three main steps: (i) controlled synthesis of gold MCNPs, (ii) fabrication of electrodes that are surrounded with a microbarrier ring to confine the deposited MCNP solution and (iii) a tailor-made drying process to enable evaporation of solvent residues from the MCNP sensing layer to prevent a coffee-ring effect. Application of this approach has been shown to produce devices with ±1.5% variance—a value consistent with the criterion for commercial sensors—as well as long shelf life and stability. Fabrication of chemical sensors based on dodecanethiol- or 2-ethylhexanethiol-capped MCNPs with this approach provides high sensitivity and accuracy in the detection of volatile organic compounds (e.g., octane and decane), toxic gaseous species (e.g., HCl and NH₃) in air and simulated mixtures of lung and gastric cancer from exhaled breath.

Introduction

Chemiresistors based on monolayer-capped metal nanoparticles (MCNPs) have been proven to determine and classify a number of diseases from exhaled breath, including lung cancer (LC)^1,2,3, colorectal cancer^1,4, head and neck cancer¹, ovarian cancer^1,5,6, bladder cancer¹, prostate cancer^1,7, kidney cancer¹, gastric cancer (GC)^1,8,9,10,11, Crohn’s disease¹, ulcerative colitis^1,12, irritable bowel syndrome^1,12, idiopathic Parkinson^1,13,14,15, atypical parkinsonism^1,14, multiple sclerosis^1,16,17, pulmonary arterial hypertension^1,18,19,20, preeclampsia^1,21, chronic kidney disease^22,23, tuberculosis²⁴ and coronavirus disease 2019²⁵. The detection and discrimination between these diseases was possible because of a unique profile made of 15 volatile organic compounds (VOCs) that characterized each type. These VOCs are 2-ethylhexanol, 3-methylhexane, 5-ethyl-3-methyloctane, acetone, ethanol, ethyl acetate, ethylbenzene, isononane, isoprene, nonanal, styrene, toluene, decane, octane and undecane. Other studies have shown the effectiveness of MCNP-based sensors for environmental monitoring, i.e., indoor air quality monitoring²⁶, through the detection of benzene, xylene, ethylbenzene and toluene. MCNP-based sensors were applied in smart heating, ventilation and air conditioning control systems, human health monitoring (capnography), home monitoring kits and even growth condition monitoring in greenhouses. Sensors based on MCNPs offer advantages such as (sub-)ppb detection limits of VOCs, a wide dynamic range for detection, ambient room operation, tolerance for interruptive molecules, reasonable dimensions and low cost^{1,8,10,27,28,29,30,31,32,33,34,35,36,37}.