Abstract
Although volatile organic compounds (VOCs) are becoming increasingly recognized as harmful agents and potential biomarkers, selective detection of the organic targets remains a tremendous challenge. Among the materials being investigated for target recognition, peptides are attractive candidates because of their chemical robustness, divergence, and their homology to natural olfactory receptors. Using a combinatorial peptide library and either a graphitic surface or phenyl-terminated self-assembled monolayer as relevant target surfaces, we successfully selected three interesting peptides that differentiate a single carbon deviation among benzene and its analogues. The heterogeneity of the designed target surfaces provided peptides with varying affinity toward targeted molecules and generated a set of selective peptides that complemented each other. Microcantilever sensors conjugated with each peptide quantitated benzene, toluene and xylene to sub-ppm levels in real time. The selection of specific receptors for a group of volatile molecules will provide a strong foundation for general approach to individually monitoring VOCs.
Highlights
Volatile organic compounds (VOCs) are becoming increasingly recognized as harmful agents and potential biomarkers, selective detection of the organic targets remains a tremendous challenge
The majority of the exhaled chemicals are volatile organic compounds (VOCs) in the range of 30–200 Daltons according to gas chromatography-mass spectroscopy (GC-MS) analysis[5,6]
These findings suggest the potential of natural receptors in the selective detection of specific VOCs
Summary
Plaque-forming units (PFU), and each sequence included about approximately 1.3 3 105 copies (see Methods). To examine the selectivity of the identified peptides, several target gases such as benzene, toluene, xylene, hexane, acetone, and ethanol were applied to microcantilever-based sensors with the signaling cantilevers being fully conjugated with one of the peptides GP1, GP2 and BP1. The BP1 peptide, which was identified from the SAM surface of phenyl-terminated alkane chains, showed significant interactions with benzene and toluene, but not with xylene. Xylene, which is characterized by two methyl substituents on the phenyl ring, might be classified differently from PTA and did not bind to BP1 peptides, highlighting the fine discrimination of chemical structures by BP1 This is the first report demonstrating the capability of SAM-based surfaces for biopanning against volatile small molecules. Designed selection of specific receptors for a group of small volatile molecules as demonstrated here has not been reported with other organic species[19,20,29]
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