Nanostructured Microcantilevers for the Sensing of Volatile Organic Compounds
Authors: McNeilly Ryan J. , Hansen Karolyn M. 
Published: February 2020

Biomolecular detection has applications in many fields, including environmental monitoring, food quality monitoring, hazardous gas detection, and medical diagnostics. Three volatile analytes are of particular interest: trimethylamine (TMA) is associated with seafood spoilage and Trimethylaminuria [1], acetic acid (AA) is a biomarker for asthma [2], and ammonia (NH3) is a biomarker for protein degradation [3]. Detection of these molecules requires a highly sensitive and highly specific sensing platform. For the purpose of detecting these molecules, a microcantilever is designed with a nanostructured surface and is functionalized with odorant-binding peptides.

Nanostructure is fabricated on the microcantilever surface in order to increase the sensitivity of the device. Silicon dioxide nanostructure is created using glancing angle deposition (GLAD) and increases the overall surface area, allowing more molecules to be captured. Images of the nanostructure taken using a high-resolution scanning electron microscope are shown in Figure 1.

The odorant-binding peptides are attached to the SiO2 surface using aminosilane. Validation of the surface chemistry was performed by attaching biotin-streptavadin with a fluorescence tag (FITC). Further validation is performed by attaching a fluorescence tag to the ammonia-binding peptide and introducing it to a SiO2 surface. The peptides are modeled using the PEP-FOLD servers [4,5], and binding interactions are modeled using the AutoDock routines in the PyRx software, Figure 2.

A scanning kelvin probe (SKP) is used to characterize the charge differential between the flat surface and nanostructure-coated surface. In addition, a charge differential is shown between surfaces functionalized with or without peptides. This charge differential can be used as a numerical indication of the success of the nanostructure and surface chemistry strategies.

References

[1] R. A. Chalmers, M. D. Bain, H. Michelakakis, J. Zschocke, R. A. Iles, “Diagnosis and management of trimethylaminuria (FMO3 deficiency) in children,” Journal of Inherited Metabolic Disease, vol. 29, pp. 162-172, 2006.

[2] R. M. Effros, R. Casaburi, J. Su, M. Dunning, J. Torday, J. Biller, R. Shaker, “The effects of volatile salivary acids and bases on exhaled breath condensate pH,” American Journal of Respiratory and Critical Care Medicine, vol. 173, pp. 386-392, 2006.

[3] G. Neri, A. Lacquaniti, G. Rizzo, N. Donato, M. Latino, M. Buemi, “Real-time monitoring of breath ammonia during haemodialysis: use of ion mobility spectrometry (IMS) and cavity ring-down spectroscsopy (CRDS) techniques,” Nephrology Dialysis Transplantation, vol. 27, pp. 2945-2952, 2012.

[4] Shen Y, Maupetit J, Derreumaux P, Tufféry P. “Improved PEP-FOLD approach for peptide and miniprotein structure prediction” J. Chem. Theor. Comput. 2014; 10:4745-4758

[5] Thévenet P, Shen Y, Maupetit J, Guyon F, Derreumaux P, Tufféry P. “PEP-FOLD: an updated de novo structure prediction server for both linear and disulfide bonded cyclic peptides.” Nucleic Acids Res. 2012. 40, W288-293.

Figure 1