Thiolated Gold Nanoflowers for Breast Cancer Volatile Organic Compound Biomarker Sensing

Breast cancer is a malignant disease, and patient prognosis significantly improves when it is detected at an early stage. Consequently, various advanced techniques have been adopted to enable early-stage detection. One promising approach involves the classification of Volatile Organic Compounds (VOCs) byproducts of cellular metabolism that are exhaled in breath, using chemiresistors based on thiolated gold nanoparticles. These sensors can selectively detect a range of VOCs, with tunability achieved by selecting thiols of specific molecular shapes. In this work, we synthesized gold nanoflowers (AuNFs) with a high surface-area-to-volume ratio, a face-centered cubic (FCC) crystalline structure, and an average size of 203 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nm</i>, as confirmed by Energy-Dispersive X-Ray Spectroscopy (EDS), X-ray diffraction (XRD), and Scanning Electron Microscopy (SEM). The AuNFs were dispersed in deionized (DI) water, pipetted, and drop coated onto interdigital gold electrodes patterned on SiO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>/p-Si (100) substrates to form a continuous film between with an initial resistance of up to 5 kΩ. Subsequently, the AuNF films were functionalized with 2-ethyl-1-hexanethiol, 2-methyl-1-propanethiol, and phenylethyl mercaptan using a simple and controllable drop coating method; this technique offers advantages over ligand ion exchange method. Thiolation increased the film resistance to approximately 10 kΩ. The resulting chemiresistor sensors demonstrated excellent sensitivity to breast cancer VOC biomarkers, including 2-ethyl-1-hexanol, 2-propanol, and heptaldehyde. Notably, 2-methyl-1-propanethiol functionalized AuNFs exhibited the highest sensitivity (21.07%) towards heptaldehyde, outperforming other thiol-modified sensors and previously reported values in literature. The sensors also demonstrated ultra-fast response and recovery times of 5 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</i> and 6 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</i>, respectively. To the best of the author’s knowledge, neither this novel sensor design nor this approach has been previously reported.