Innovative Nanosensor for Disease Diagnosis

Abstract

As a futuristic diagnosis platform, breath analysis is gaining much attention because it is a noninvasive, simple, and low cost diagnostic method. Very promising clinical applications have been demonstrated for diagnostic purposes by correlation analysis between exhaled breath components and specific diseases. In addition, diverse breath molecules, which serve as biomarkers for specific diseases, are precisely identified by statistical pattern recognition studies. To further improve the accuracy of breath analysis as a diagnostic tool, breath sampling, biomarker sensing, and data analysis should be optimized. In particular, development of high performance breath sensors, which can detect biomarkers at the ppb-level in exhaled breath, is one of the most critical challenges. Due to the presence of numerous interfering gas species in exhaled breath, selective detection of specific biomarkers is also important. This Account focuses on chemiresistive type breath sensors with exceptionally high sensitivity and selectivity that were developed by combining hollow protein templated nanocatalysts with electrospun metal oxide nanostructures. Nanostructures with high surface areas are advantageous in achieving high sensitivity because the sensing signal is dominated by the surface reaction between the sensing layers and the target biomarkers. Furthermore, macroscale pores between one-dimensional (1D) nanostructures can facilitate fast gas diffusion into the sensing layers. To further enhance the selectivity, catalytic functionalization of the 1D metal oxide nanostructure is essential. However, the majority of conventional techniques for catalytic functionalization have failed to achieve a high degree of dispersion of nanoscale catalysts due to aggregation on the surface of the metal oxide, which severely deteriorates the sensing properties by lowering catalytic activity. This issue has led to extensive studies on monolithically dispersed nanoscale particles on metal oxides to maximize the catalytic performances. As a pioneering technique, a bioinspired templating route using apoferritin, that is, a hollow protein cage, has been proposed to obtain nanoscale (∼2 nm) catalyst particles with high dispersity. Nanocatalysts encapsulated by a protein shell were first used in chemiresistive type breath sensors for catalyst functionalization on 1D metal oxide structures. We discuss the robustness and versatility of the apoferrtin templating route for creating highly dispersive catalytic NPs including single components (Au, Pt, Pd, Rh, Ag, Ru, Cu, and La) and bimetallic catalysts (PtY and PtCo), as well as the core-shell structure of Au-Pd (Au-core@Pd-shell). The use of these catalysts is essential to establish high performance sensors arrays for the pattern recognition of biomarkers. In addition, novel multicomponent catalysts provide unprecedented sensitivity and selectivity. With this in mind, we discuss diverse synthetic routes for nanocatalysts using apoferritin and the formation of various catalyst-1D metal oxide composite nanos...

Glass‐Fabric Reinforced Ag Nanowire/Siloxane Composite Heater Substrate: Sub‐10 nm Metal@Metal Oxide Nanosheet for Sensitive Flexible Sensing Platform

“…Because Pt nanocatalysts in Pt‐SnO 2 NSs possess the capability of effectively dissociating O 2 and CH bonding, the effective dissociation of oxygen molecules of CH bonding in DMS induces active gas sensing reaction of DMS with the chemisorbed oxygen species (O − and O 2 − ) . Note that the major X‐ray photoelectron spectroscopy (XPS) peak of oxygen species adsorbed on the surface of Pt‐SnO 2 NSs is the peak of O − ions (Figure S8b, Supporting Information), which are active gas reaction sites compared to lattice oxygen O 2− . Therefore, Pt‐SnO 2 NSs can deliver high response and superior selectivity toward DMS ( R air / R gas = 11.5 at 5 ppm of DMS).…”

“…Compared with carbon and metal based sensing layers, SMOs sensors generally offer much enhanced sensitivity toward target analytes, even at sub‐ppm level of gas concentration . Moreover, functionalization of catalysts on SMOs significantly improves not only gas responses but also selective detection capability . Gas sensing mechanism of SMOs layers is based on the resistance variation, which is caused by adsorption/desorption of target analytes which react with chemisorbed oxygen species on surface of sensing layer.…”

Cyber–Physiochemical Interfaces

“…Besides biophysical signals, there are numerous biochemical signals such as metabolites, proteins, and nucleotides that provide a window to reflect our overall well‐being including state of health, the environment, and food safety . For instance, glucose for diabetes, chloride for cystic fibrosis, human chorionic gonadotropin for pregnancy, carcinoembryonic antigen and prostate‐specific antigen for cancers, breath ethanol for drunk driving, and volatile organic compounds for indoor air quality . It is noted that these indicators do not work independently and have huge interconnection with each other.…”

“…Copyright 2018, Springer Nature. Breath sensor image: Reproduced with permission . Copyright 2017, American Chemical Society.…”

“…The collected samples are then subsequently used in benchtop equipment such as mass spectrometry, spectrophotometer, electrochemical measurement, chloridometry, or other analytical methods. Among them, electrochemical and colorimetric outputs are most feasible to be miniaturized into portable and wearable modality such as tattoo‐based perspiration sensor, wearable mask‐based breath sensor, contact lenses‐based tear sensor, mouth guard‐based saliva sensor, and epidermal sensor integrated with therapy systems (Figure ) . Taking the glucose biosensor as an example, the catalytic oxidation of glucose by glucose oxidase in the presence of oxygen (electron mediator) produces H 2 O 2 (oxidized mediator).…”