title: Photoinactivation effects of hematoporphyrin monomethyl ether on Gram-positive and -negative bacteria detected by atomic force microscopy.
abstract: The photodynamic antimicrobial chemotherapy as a promising approach for efficiently killing pathogenic microbes is attracting increasing interest. In this study, the cytotoxic and phototoxic effects of hematoporphyrin monomethyl ether (HMME) on the Gram-positive and Gram-negative bacteria were investigated. The cell viability was assessed by colony-forming unit method, and the results indicated that there was no significant cytotoxicity but high phototoxicity in the examined concentrations. Notably, the Gram-positive bacteria were more sensitive to HMME in phototoxicity. Simultaneously, an atomic force microscope (AFM) was used to detect the changes in morphological and nanomechanical properties of bacteria before and after HMME treatment. AFM images indicate that upon photoinactivation, the bacterial surface changed from a smooth, homogeneous architecture to a heterogenous, crackled morphology. The force spectroscopy measurements reveal that the cell wall became less rigid and the Young's modulus decreased about 50%, whereas the tip-cell-surface adhesion forces increased significantly compared to those of native cells. It was speculated that the photodynamic effects of HMME induced the changes in the chemical composition of the outer membrane and exposure of some proteins inside the envelope. AFM can be utilized as a powerful and sensitive method for studying the interaction between bacteria and drugs.
authors.affiliation: Department of Chemistry, Jinan University, Guangzhou, China.
authors.forename: Hua
authors.initials: H
authors.lastname: Jin
authors.forename: Xun
authors.initials: X
authors.lastname: Huang
authors.forename: Yong
authors.initials: Y
authors.lastname: Chen
authors.forename: Hongxia
authors.initials: H
authors.lastname: Zhao
authors.forename: Hongyan
authors.initials: H
authors.lastname: Ye
authors.forename: Feicheng
authors.initials: F
authors.lastname: Huang
authors.forename: Xiaobo
authors.initials: X
authors.lastname: Xing
authors.forename: Jiye
authors.initials: J
authors.lastname: Cai
mesh_terms: D001422:Bacterial Adhesion; D006090:Gram-Negative Bacteria / Q000187:drug effects / Q000472:pathogenicity* / Q000648:ultrastructure; D006094:Gram-Positive Bacteria / Q000187:drug effects / Q000472:pathogenicity* / Q000648:ultrastructure; D006415:Hematoporphyrins / Q000494:pharmacology*; D050296:Microbial Viability / Q000187:drug effects; D018625:Microscopy, Atomic Force; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000494:pharmacology*
chemical_list: D006415:Hematoporphyrins; D017319:Photosensitizing Agents; C494379:hematoporphyrin monomethyl ether