Exploring the role of impedance spectroscopy in assessing 405 nm laser-induced inactivation of saccharomyces cerevisiae.

Impedance spectroscopy was employed to assess the electrical properties of yeast following 405 nm laser irradiation, exploring the effects of visible, non-ionizing laser-induced inactivation as a more selective and safer alternative for photoinactivation applications compared to the use of DNA targeting, ionizing UV light. Capacitance and impedance spectra were obtained for yeast suspensions irradiated for 10, 20, 30, and 40 min using 100 and 200 mW laser powers. Noticeable differences in capacitance spectra were observed at lower frequencies (40 Hz to 1 kHz), with a significant increase at 40 min for both laser powers. ß-dispersion was evident in the impedance spectra in the frequency range of 10 kHz to 10 MHz. The characteristic frequency of dielectric relaxation steadily shifted to higher frequencies with increasing irradiation time, with a drastic change observed at 40 min for both laser powers. These changes signify a distinct alteration in the physical state of yeast. A yeast spot assay demonstrated a decrease in cell viability with increasing laser irradiation dose. The results indicate a correlation between changes in electrical properties, cell viability, and the efficacy of 405 nm laser-induced inactivation. Impedance spectroscopy is shown to be an efficient, non-destructive, label-free method for monitoring changes in cell viability in photobiological effect studies. The development of impedance spectroscopy-based real-time studies in photoinactivation holds promise for advancing our understanding of light-cell interactions in medical applications.

Exploring differentiation-dependent responses to 532 nm green laser photobiomodulation in SHSY5Y neuroblastoma cells.

Photobiomodulation (PBM) holds promise as a therapy modality, but its applicability is hindered by the lack of a quantitative model to predict the optimal dose for all forms of PBM. This study investigated the optimal PBM parameters for 532 nm green laser irradiation on SHSY5Y neuroblastoma cells, a commonly used in vitro model for neurodegenerative disease studies. A two-tailed, two sample t-test with equal variance was used to obtain the p-values and statistical significance. There are 3 sets of parameters showing significant ( p < 0 . 01 ) positive percentage biostimulation. 160 m W , 15 m i n produce a percentage biostimulation of ( 9 ± 10 ) % ; 180 m W , 5 m i n produce a percentage biostimulation of ( 19 ± 7 ) % ; and ( 200 m W , 5 m i n ) produce a percentage biostimulation of ( 9 ± 2 ) % . The highest significant ( p < 0 . 01 ) percentage bioinhibition observed is for 220 m W , 15 m i n (dose: 1008 J / c m 2 ) producing a bioinhibition of ( 54 ± 1 ) % . After identifying several parameters that produce noticeable photobiological effects (biostimulation and bioinhibition), this study compared the reaction of undifferentiated and differentiated SHSY5Y cells to laser irradiation and found that undifferentiated SHSY5Y cells shows greater photobiological effect from 532 nm laser irradiation ( p < 0 . 01 ) . This study demonstrated the differentiation-dependant photobiological effect of SHSY5Y in 532 nm laser PBM. This shows that considerations on the differentiation state of cells is important in PBM studies. The hypothesis of difference in intracellular reactive oxygen species (ROS) accumulation from laser irradiation can serve as a versatile explanation of the observed difference in photobiological effect. Further investigation into the role of ROS as a mediator of various photobiological effects from laser of different wavelengths is warranted.