Abstract
The detection and recognition of metabolically derived aldehydes, which have been identified as important products of oxidative stress and biomarkers of cancers; are considered as an effective approach for early cancer detection as well as health status monitoring. Quartz crystal microbalance (QCM) sensor arrays based on molecularly imprinted sol-gel (MISG) materials were developed in this work for highly sensitive detection and highly selective recognition of typical aldehyde vapors including hexanal (HAL); nonanal (NAL) and bezaldehyde (BAL). The MISGs were prepared by a sol-gel procedure using two matrix precursors: tetraethyl orthosilicate (TEOS) and tetrabutoxytitanium (TBOT). Aminopropyltriethoxysilane (APT); diethylaminopropyltrimethoxysilane (EAP) and trimethoxy-phenylsilane (TMP) were added as functional monomers to adjust the imprinting effect of the matrix. Hexanoic acid (HA); nonanoic acid (NA) and benzoic acid (BA) were used as psuedotemplates in view of their analogous structure to the target molecules as well as the strong hydrogen-bonding interaction with the matrix. Totally 13 types of MISGs with different components were prepared and coated on QCM electrodes by spin coating. Their sensing characters towards the three aldehyde vapors with different concentrations were investigated qualitatively. The results demonstrated that the response of individual sensors to each target strongly depended on the matrix precursors; functional monomers and template molecules. An optimization of the 13 MISG materials was carried out based on statistical analysis such as principle component analysis (PCA); multivariate analysis of covariance (MANCOVA) and hierarchical cluster analysis (HCA). The optimized sensor array consisting of five channels showed a high discrimination ability on the aldehyde vapors; which was confirmed by quantitative comparison with a randomly selected array. It was suggested that both the molecularly imprinting (MIP) effect and the matrix effect contributed to the sensitivity and selectivity of the optimized sensor array. The developed MISGs were expected to be promising materials for the detection and recognition of volatile aldehydes contained in exhaled breath or human body odor.
Highlights
The sensing of volatile aldehydes has attracted a continuously growing interest in various fields.It is well known that vapors of aldehydes such as formaldehyde, benzaldehye and nonanal, are Sensors 2017, 17, 382; doi:10.3390/s17020382 www.mdpi.com/journal/sensorsSensors 2017, 17, 382 typical indoor pollutants related to sick building syndrome [1]
It was found that the film-forming properties of the molecularly imprinted sol-gel (MISG) during the spin coating process was dependent upon the materials of matrix precursors, functional monomers and template molecules
Quartz crystal microbalance (QCM) sensor arrays based on molecularly imprinted sol-gel (MISG) materials were investigated in the present study for the detection and recognition of volatile aldehyde vapors
Summary
The sensing of volatile aldehydes has attracted a continuously growing interest in various fields.It is well known that vapors of aldehydes such as formaldehyde, benzaldehye and nonanal, are Sensors 2017, 17, 382; doi:10.3390/s17020382 www.mdpi.com/journal/sensorsSensors 2017, 17, 382 typical indoor pollutants related to sick building syndrome [1]. Volatile hexanal and nonanal present in the exhaled breath are identified by many studies as biomarkers related to lung cancer [2,3,4,5]. The detection of volatile aldehydes has been considered as an effective approach for the early detection of cancers as well as the monitoring of health status. It is, difficult to detect aldehydes selectively due to the complex composition of volatile organic compounds contained in exhaled breath. The development of sensing materials with both high sensitivity and selectivity on volatile aldehydes is very important for the aldehyde-related biomarker sensors
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