This work describes the application of acoustic wave technology for the real-time and label-free detection of biotin-avidin interactions. Biosensing surfaces are constructed onto unelectroded piezoelectric quartz discs as functionalizable mixed self-assembled monolayers (SAM) produced from previously unreported linker and diluent molecules. Biotinthiol can subsequently be immobilized for detection purposes in a straightforward and coupling-free manner. Specific and non-specific adsorptions of avidin are measured at ultra-high frequencies (1.06 and 0.82 GHz) with an electromagnetic piezoelectric acoustic sensor (EMPAS) using micromolar avidin-spiked buffer solutions. These biosensing surfaces, especially the oligoethylene glycol SAM-based variety, display high specificity for avidin, with moderate to excellent reproducibility. This preliminary work constitutes the first application of SAM chemistry and EMPAS technology in the bioanalytical field.

The operation of biosensors requires surfaces that are both highly specific towards the target analyte and that are minimally subject to fouling by species present in a biological fluid. In this work, we further examined the thiosulfonate-based linker in order to construct robust and durable self-assembling monolayers (SAMs) onto hydroxylated surfaces such as silica. These SAMs are capable of the chemoselective immobilization of thiol-containing probes (for analytes) under aqueous conditions in a single, straightforward, reliable, and coupling-free manner. The efficacy of the method was assessed through implementation as a biosensing interface for an ultra-high frequency acoustic wave device dedicated to the detection of avidin via attached biotin. Fouling was assessed via introduction of interfering bovine serum albumin (BSA), IgG antibody, or goat serum. Improvements were investigated systematically through the incorporation of an oligoethylene glycol backbone employed together with a self-assembling diluent without a functional distal group. This work demonstrates that the incorporation of a diluent of relatively short length is crucial for the reduction of fouling. Included in this work is a comparison of the surface attachment of the linker to Si3N4 and AlN, both materials used in sensor technology.

The adulteration of food products, including honeys and syrups, is of growing concern in global food markets. Detecting adulterated food products can be difficult using traditional analytical methodologies because of complex sample matrices or poor separation of key compounds. NMR is an analytical tool that circumvents some of these issues by providing a snapshot of chemical components in a sample mixture with minimal and unbiased sample preparation. In this upper-year undergraduate and graduate laboratory, students are introduced to NMR as an analytical tool through the analysis of a honey or syrup sample of their choice. Simple sugars in honeys or syrups are quantified using a single point internal standard, while the NMR signals arising from the complex organic mixture of amino acids, proteins, carbohydrates, and oils found in these syrups are compared against a sample data set using principal component analysis. The experiment highlights the benefits and challenges of NMR as an analytical tool, demonstrating the simplicity of sample preparation and single-point calibration, as well as the limitations of instrument sensitivity and signal resolving power.