Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA.
J Photochem Photobiol B. 2012 Oct 3;115:42-50. doi: 10.1016/j.jphotobiol.2012.06.009. Epub 2012 Jul 4.
The potential application of nonlinear optical imaging diagnosis and treatment using femtosecond laser pulses in humans accentuates the need for studies carried out in whole organisms instead of single cells or cell cultures. While there is a general consensus that in order to minimize the level of photodamage the excitation power has to be kept as low as possible, it has yet to be determined if shorter pulses have greater benefit than longer pulses. Here we evaluate the rate of death in Drosophila melanogaster as the integral parameter related to photodamage resulting from femtosecond near infrared (NIR) laser irradiation under conditions comparable to those used in two-photon excited fluorescence (TPEF) microscopy. We found that the lethality (resulting from photodamage) as a function of laser energy fluence fits a 3-region dose-response curve. The lethality was accompanied with development of necrosis and apoptosis in irradiated tissues. Quantitative analysis showed that the damage has a mostly linear character on energy fluence per pulse, and for a given TPEF signal, shorter (37 fs) pulse duration results in lower lethality than longer (100 fs) pulse duration. These results have important implications for the use of femtosecond NIR laser pulses in microscopy as well as in vivo medical imaging.
飞秒激光脉冲在人类中进行非线性光学成像诊断和治疗的潜在应用凸显了需要在整个生物体中进行研究，而不是在单个细胞或细胞培养物中进行研究。虽然人们普遍认为为了将光损伤的程度降到最低，必须将激发功率保持在尽可能低的水平，但尚未确定短脉冲是否比长脉冲更有优势。在这里，我们评估了黑腹果蝇的死亡率，作为与飞秒近红外（NIR）激光照射相关的光损伤的整体参数，其条件与双光子激发荧光（TPEF）显微镜中使用的条件相当。我们发现，激光能量密度的致死率（由光损伤引起）符合三区域剂量反应曲线。在照射组织中，致死率伴随着坏死和凋亡的发生。定量分析表明，损伤对每个脉冲的能量密度具有线性特征，并且对于给定的 TPEF 信号，较短（37 fs）脉冲持续时间导致的致死率低于较长（100 fs）脉冲持续时间。这些结果对于在显微镜以及体内医学成像中使用飞秒 NIR 激光脉冲具有重要意义。
