title: Time dependency of ultrasound-facilitated gene transfection.
abstract: BACKGROUND
  The use of ultrasound (US)-facilitated gene therapy is increasing rapidly as a result of its high specificity and non-invasiveness. However, the acoustic parameters that produce the most efficient transfection have not been established. The present study investigated the effects of time parameters [including pulsing strategy (on- and off-times), exposure duration, pore opening time and expression duration] of US-facilitated gene transfection.
  
  
  METHODS
  Cervical cancer cells (HeLa cells) cultured with pCMViLUC plasmids were exposed to 1-MHz pulsed US, and gene transfection efficiency and cell viability were assessed. The ability of in vivo transfection by ultrasound using different pulsing strategy was also evaluated.
  
  
  RESULTS
  For a constant total exposure time, the transfection was always better for a longer on-time (on-off ratio = 1, or 50% duty cycle) than a shorter one (ratio = 0.1, 9% duty cycle), whether performed in vitro or in vivo. However, for a fixed on-time, there was a strong inverse correlation between transfection efficiency and off-time (r(2) = 0.89). Multiple regression analysis showed that the on-time, off-time and on-off ratio are all independent variables for US-facilitated gene transfection. Furthermore, transfection increased with the total exposure time, but plateaued for long exposure times. More than half of the opened pores closed within 15 s after the cessation of US exposure. The half-life of the transfected DNA was 7.43 days.
  
  
  CONCLUSIONS
  Time is an important determinant of US-facilitated gene transfection. Methods for increasing the transfected number of plasmids, such as increasing the concentration of plasmids or the duration of pore opening, will be critical for future research and clinical applications.
authors.affiliation: Institute of Biomedical Engineering, National Taiwan University College of Medicine, Taipei, Taiwan.
authors.forename: Kun-Che
authors.initials: KC
authors.lastname: Tsai
authors.forename: Shin-Yu
authors.initials: SY
authors.lastname: Fang
authors.forename: Shu-Jyuan
authors.initials: SJ
authors.lastname: Yang
authors.forename: Ming-Jium
authors.initials: MJ
authors.lastname: Shieh
authors.forename: Win-Li
authors.initials: WL
authors.lastname: Lin
authors.forename: Wen-Shiang
authors.initials: WS
authors.lastname: Chen
mesh_terms: D000162:Acoustics; D000818:Animals; D002463:Cell Membrane Permeability; D002470:Cell Survival; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D015999:Multivariate Analysis; D013997:Time Factors; D014162:Transfection; D014465:Ultrasonics
chemical_list: D008156:Luciferases