Chemoresistive Nanostructured Metal-Oxide Sensors for Human Tumor Tissue and Blood Exhalations Analysis
Authors: Astolfi Michele , Zonta Giulia , Landini Nicolò , Gherardi Sandro , Rispoli Giorgio , Anania Gabriele , Benedusi Mascia , Guidi Vincenzo , Palmonari Caterina , Valt Matteo , Malagù Cesare 
Published: July 2021

Early-stage tumor detection is one of the most coveted goals for the world research community. An effective prevention, associated to reliable screening protocols, is crucial to favor a early diagnosis, allowing doctors and surgeons to intervene with high probabilities of success on tumor affected patients. The main purpose of this study is cancer detection, exploiting the volatile organic compounds (VOCs) produced by cancer cells as tumor biomarkers [1][2], by investigating tumor tissue and blood samples. Tumor biomarkers exhalation is attributed to two main cell involving biological mechanisms: altered metabolism and cellular membrane peroxidation [3]. This experimental work was carried on using an innovative, fast-responding and reliable patented device, named SCENT B1 [4], entirely designed and assembled in the Sensor Laboratory of the University of Ferrara. It hosts an array of four specific metal-oxide (MOX) sensors able to detect gases in low concentration (up to 10 ppm) with high stability and repeatability, chosen after many tests on different types of biological samples (feces, blood, cell cultures, etc.) [5,6]; the chosen sensors are based on different mixtures of tin, titanium, tungsten, niobium, tantalum and vanadium oxides (ST25Au, W11, STN, TiTaV). Moreover, SCENT B1 is gifted of a power supply and sensor signal transduction electronic boards, a pneumatic air system (necessary to direct the VOCs contaminated air from the sample chamber to the sensors) and an ad hoc management and data acquisition software (LSS4) [6]. The sensor output signal is a voltage directly proportional to the sensor conductance, depending on the chemical redox reactions taking place on the surface of the sensor sensing material. The sensor response is: R=Vgas/Vair , where Vgas and Vair are the sensor voltage in gas presence and in dry air after the steady state achievement respectively [6].Sensor responses were further elaborated, using different statistical approaches as principal component analysis and receiver operating characteristics methods.
Measurements have been performed on colorectal cancer and healthy tissues surgically removed from the same operatory piece (directly and far enough from tumor mass respectively) (Figure 1a), and on blood samples collected from tumor affected subjects and healthy ones as controls (Figure 1b). with the future aim of extending the study to other tumor types. All four sensors gave larger responses (although with different amplitudes) to the tumor tissue with respect to the healthy one. Smaller and reproducible responses were given by the breeding ground (DMEM) only, confirming that it does not alter the measurements. The results are consistent with the stronger and altered metabolism of tumor cells, leading them to emit a larger amount of volatile biomarkers with respect to the healthy ones;.
All the four sensors hosted by SCENT B1 proved to be capable of distinguishing between healthy and tumor tissue and blood samples, although with different discrimination power. The encouraging results of this feasibility study are the basis of a new in-depth study, which includes also a follow-up protocol based on post surgery blood monitoring of patients. Our future aims foresee the extension of this study to other tumor types and the obtainment of the SCENT B1 clinical validation as oncologic screening device.

Figure 1