Mass Density Characterization of Hydrogel-Based Systems Inoculated with Bacterial Strains and Dose-Response Performance of Escherichia coli Inoculation

This study aims to determine the density of two hydrogel-based media, medium with agar-agar and medium with agar-agar and glucose, which are suitable for both irradiation and bacterial growth, considering the presence or absence of Staphylococcus aureus and Escherichia coli strains. The viability of Escherichia coli cell-inoculated systems was also evaluated to explore potential applications in radiation dosimetry within the 0–10 Gy range, using spectrophotometric and bacterial culture methods. Mass density measurements were performed at varying temperatures using two approaches: the first one, based on direct measurements of mass and volume, yielded densities comparable to liquid water, with uncertainties ranging from 9 to 16%, while the second approach, employing Archimedes’ principle (mass in air vs. mass in a liquid of known density), produced more accurate results, with uncertainties between 0.04 and 0.08%, thus proving more reliable for density determinations. Furthermore, the feasibility study of Escherichia coli-inoculated systems for ionizing radiation dosimetry demonstrated a linear spectrophotometric response to radiation doses across the investigated range, particularly for samples stored at 25 °C. The studied systems were characterized in terms of the corresponding growth curve and post-irradiation bacterial survival, supporting their potentiality as reliable ionizing radiation dosimeters.