This study evaluated the in vitro effects of 62.5 µg/mL silica nanoparticles (SiO₂ NPs) on MRC-5 human lung fibroblast cells for 24, 48 and 72 h. The nanoparticles’ morphology, composition, and structure were investigated using high resolution transmission electron microscopy, selected area electron diffraction and X-ray diffraction. Our study showed a decreased cell viability and the induction of cellular oxidative stress as evidenced by an increased level of reactive oxygen species (ROS), carbonyl groups, and advanced oxidation protein products after 24, 48, and 72 h, as well as a decreased concentration of glutathione (GSH) and protein sulfhydryl groups. The protein expression of Hsp27, Hsp60, and Hsp90 decreased at all time intervals, while the level of protein Hsp70 remained unchanged during the exposure. Similarly, the expression of p53, MDM2 and Bcl-2 was significantly decreased for all time intervals, while the expression of Bax, a marker for apoptosis, was insignificantly downregulated. These results correlated with the increase of pro-caspase 3 expression. The role of autophagy in cellular response to SiO₂ NPs was demonstrated by a fluorescence-labeled method and by an increased level of LC3-II/LC3-I ratio. Taken together, our data suggested that SiO₂ NPs induced ROS-mediated autophagy in MRC-5 cells as a possible mechanism of cell survival.

Laser deposition was used to obtain Pd/ZnO bilayers, which were used as sensing layers in surface acoustic wave (SAW) sensors. The effect of laser deposition parameters such as deposition pressure, laser energy per pulse, laser wavelength or pulse duration on the porosity of the Pd and ZnO films used in the sensors was studied. The effect of the morphology of the Pd and ZnO components on the sensor response to hydrogen was assessed. Deposition conditions producing more porous films lead to a larger sensor response. The morphology of the ZnO component of the bilayer is decisive and has an influence on the sensor properties in the same order of magnitude as the use of a bilayer instead of a single Pd or ZnO layer. The effect of the Pd film morphology is considerably smaller than that of ZnO, probably due to its smaller thickness. This has implications in other bilayer material combinations used in such sensors and for other types of analytes.

This study investigates ZnO-based surface acoustic wave (SAW) sensors for the detection of methane (CH₄) at room temperature (RT), focusing on the influence of film morphology and oxide heterostructures developed by pulsed laser deposition (PLD). Bilayer thin films—specifically ZnO/CuO and ZnO/In₂O₃—were deposited onto quartz substrates at 400 °C under oxygen pressures of 100 and 700 mTorr to evaluate how deposition conditions affect sensor performance. Structural and morphological characterization was performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). ZnO thin films deposited at 700 mTorr exhibited a more open, granular morphology compared to those deposited at 100 mTorr, a feature likely to facilitate gas access to the sensor’s active surface. The addition of CuO and In₂O₃ top layers further influenced the sensor response, presumably through surface and interface effects. Among the configurations studied, sensor S6 (ZnO/CuO, with both layers deposited at 700 mTorr) demonstrated the highest sensitivity—0.18 Hz/ppm—within the experimentally investigated CH₄ concentration range (0.4–2%), with an estimated limit of detection (LOD) of 167 ppm. Short-term measurements performed on sensors S4 and S6 at a 2% CH₄ concentration indicated reversible responses over two consecutive exposure and recovery cycles, with a return to the initial baseline value following the removal of the gas. These results suggest that ZnO-based double layers, fabricated via PLD, are promising candidates for further investigation as CH₄-sensitive layers at RT.