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wo357026239铜虫 (正式写手)
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In previous works, the dye exclusion method was used to examine cell death. Under this circumstance, the laser powers applied have to be high enough to compromise the cell membrane and induce instant cell death (necrosis). When a cell is labeled with gold nanoparticles, heat can be built up around the nanoparticles instantly upon the irradiation of an ultrafast pulsed laser. If the laser power density is high enough, fragmentation of gold nanoparticles can be produced，which can bring a localized mechanical shock to the cell membrane causing membrane perforation. At a low power, when the energy fluence is high enough, the heat produced from gold nanorods can also burn the cell membrane. These two effects will compromise the integrity and cause leaking of cell membrane, leading to rapid cell death.As known, cell proliferation can be stopped either by damaging the cells (necrosis) or by inducing cell apoptosis. Necrosis is a process of cell death by accident, which is normally due to the compromising of membrane integrity. In contrast, apoptosis is programmed cell death (suicide), which is a natural process that governs the proliferation of cells in a living body. As a matter of fact, what makes a cell cancerous is the disturbance of its natural apoptosis, leading to its proliferation out of control. To restore and enhance apoptosis, certain stimuli such as drugs and irradiation can be introduced. This forms the basis of the conventional chemotherapy and radiation therapy. With reduction in power density or energy fluence, the thermal effect becomes dominant. While keeping the membrane integrated, the photothermal effect of gold nanorods can potentially lead to the dysfunction of the subcellular structures that govern the proliferation of cells, causing cell apoptosis .While maintaining the therapeutic effects, a laser operating at these lower energy levels is clinically safer. In addition, compared with necrosis, apoptosis is more suitable to in vivo treatment since inflammation and even secondary cancers associated with necrosis can be avoided. Despite its significance, laser induced apoptosis of cancer cells in the presence of gold nanoparticles has not been investigated, to the best of our knowledge. In this work, gold nanorod-enhanced two-photon luminescence imaging and apoptosis of cancer cells will be investigated in the aim of developing a way for efficient and medically safe cancer detection and microsurgery using femtosecond lasers under twophoton microscopy. A two-photon Fluoview inverted scanning microscope was used for two-photon excitation of gold nanorods. A human cervical cancer cell line HeLa was used as a model. To achieve efficient targeting of gold nanorods to the cancer cells, transferrin molecules were conjugated to the surface of the nanorods. Transferrin has been proven to be efficient in enhancing cancer targeting by nanoparticles including gold nanoparticles.The imaging capability of gold nanorods was also compared with the cell autofluorescence and molecular dyes. |
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moqing1991
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爱与雨下(金币+1): 2012-01-04 11:52:51
爱与雨下(金币+1): 2012-01-04 11:52:51
| 在以往的研究中，染料排除方法被用来研究细胞死亡率，在这种情况下，激光功率的应用都必须充分高，足以破坏细胞膜并诱导即时性细胞死亡（坏死）。当细胞用金纳米粒子标记时，超快脉冲激光照射后会即刻在纳米粒子周围产生热量。如果激光功率密度足够高，可以使金纳米粒子分散，从而给细胞膜带来局部机械冲击，造成穿孔。在低功耗、能源能量密度足够高时，金纳米棒产生的热量还可以烧毁细胞膜。这两种效应都会破坏完整性并造成细胞膜的泄漏，导致细胞快速死亡。总所周知的，细胞增殖停止可以通过破坏细胞（坏死），或通过诱导细胞凋亡。坏死是细胞死亡事故过程，通常是在细胞膜的完整性的前提下。与此相反，细胞凋亡是细胞程序化死亡（自杀），这是一个自然的过程，从而产生活体细胞的增殖。事实上，细胞发生癌变是因为自然细胞凋亡遭到干扰，从而导致其增殖失控。为了恢复和增强细胞凋亡，某些刺激，如药物和辐射可以被使用。这就形成了传统的化疗和放射治疗的基础。减少功率密度或能量通量，热效应成为主要因素。在保持细胞膜完整的前提下，金纳米棒的光热效应有可能致使支配细胞增殖的亚细胞结构功能失调，引起细胞凋亡。在保证同样治疗效果的同时，在较低能量水平上运行的激光在临床上更加安全。此外，与坏死相比较，凋亡更适合于体内治疗，因为可以避免炎症和坏死引起的继发性癌症。据我们所知，尽管金纳米粒子协同下激光诱导的癌细胞凋亡的意义极其重大，却很少有人对其开展研究。 |
3楼2012-01-04 11:08:34