Effect of 1 064-nm Q-switched Nd:YAG laser on cell viability, protease activity and structures of Malassezia furfur / 中华皮肤科杂志

ABSTRACT

Objective:To investigate the effect of 1 064-nm Q-switched NdYAG laser at different energy settings on cell viability, protease activity and structures of Malassezia furfur. Methods:Cultured standard strains of Malassezia furfur were divided into several groups to be irradiated with 1 064-nm Q-switched NdYAG laser at different energies of 0 (control group) , 500, 600, 700, 800 and 900 mJ, respectively. Then, fungal suspensions in the above groups were inoculated onto the Leeming & Notman medium separately. After 7-day culture, the diameter and number of colonies were measured to evaluate the fungal cell viability, the protease activity was measured by using the whole-milk plate medium, and the ultrastructure of Malassezia furfur in each group was observed by transmission electron microscopy. One-way analysis of variance was used for comparisons among multiple groups, least significant difference- t test for multiple comparisons, and Pearson correlation analysis for analyzing correlations of laser energy with colony diameter, number and protease activity. Results:The colony diameter and number both significantly differed among the control group, 500-, 600-, 700-, 800- and 900-mJ groups (colony diameter 4.05 ± 0.69, 3.76 ± 0.51, 3.28 ± 0.41, 3.09 ± 0.72, 2.54 ± 0.64 and 2.43 ± 0.41 mm, respectively; colony number 4 787 ± 597, 4 287 ± 761, 1 879 ± 275, 1 082 ± 248 and 209 ± 42, 72 ± 31 colony-forming units, respectively; F = 14.83, 231.85, respectively, both P < 0.05) , and were significantly decreased in the 600-, 700-, 800- and 900-mJ groups compared with the control group (all P < 0.05) . The laser energy was negatively correlated with the colony diameter and number ( r = -0.67, -0.91, respectively, both P < 0.05) . The protease activity significantly differed among the control group, 500-, 700- and 900-mJ groups ( F = 346.60, P < 0.05) , and was significantly lower in the 700- and 900-mJ groups than in the control group (both P < 0.05) . There was a negative correlation between the laser energy and protease activity ( r = -0.94, P < 0.05) . Transmission electron microscopy showed intact fungal structures in the control group, relatively intact fungal structures in the 500-mJ group, and obviously damaged fungal structures in the 600- to 900-mJ groups, and the greater the laser energy, the more severely the fungal structures were damaged. Conclusion:The 1 064-nm Q-switched NdYAG laser could affect the cell viability of and protease activity in Malassezia furfur, and damage its structures.