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wo357026239銅蟲 (正式寫手)
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The strong two-photon luminescence of gold nanorods makes them suitable to 3D imaging. Although autofluorescence of cell provides the most convenient way for cell imaging, the high laser power of 35 mW needed to induce the autofluorescence is a potential safety hazard. As shown in Fig. 4A, cells can be killed after 30 raster scans at even a lower power of 30 mW. Obvious perforation of cells was observed when the power was increased to 35 mW (Fig. 6A). A laser operating at such a high power will thus cause clinical safety concerns. The enhanced imaging in the presence of gold nanorods is due to the high two-photon excitation cross section of gold nanorods, which is about ~3 ×104 GM for a nanorod with an aspect ration of 4 [31]. This is three orders of magnitude higher than that of a fluoresceine molecule [32,33]. Therefore, compared with the conventional fluorescent molecules, gold nanorod is a superior contrast agent. It was observed that membrane blebbing occurred on both necrotic and apoptotic cells. The initiation of cell membrane blebbing has been generally regarded as the sign of apoptosis [34]. During apoptosis, the cell’s cytoskeleton breaks up causing the membrane to bulge outward [35]. The intense femtosecond laser pulses particularly the localized photothermal effects of gold nanorods produced by the femtosecond laser pulses can destroy the intracellular actin network which provides mechanical support to maintain cell shape [7]. It was observed that the staining of the necrotic cells took only a few minutes. While for apoptotic cells to get sufficient staining with Annexin V-Cy3.18, the treated cells have to be incubated for at least 2 h. The short time required for PI staining of the necrotic cells indicates that the membrane of the cells was compromised. It was observed that when the laser power is 2mW(55.6 W/cm2) and above, perforation of cell membranewas induced after only one raster scan (Fig. 6B). The sharp decrease in irradiation duration can significantly reduce the energy fluence. However, a laser operating at this power presents a potential safetyhazard. This critical power/power density should be the upper limit that can be applied. With the eduction in the power density, the thermal effect becomes dominant and thermally induced cell damage controls the death of cells. Perforation of cell membrane enhanced in the presence of gold nanorods at high energy fluence was also reported in a real-time observation of a recent work. In terms of cancer therapy, significant reduction in the energy fluence can be achieved by inducing cell apoptosis rather than necrosis. For example, at 0.5 mW, apoptosis of HeLa cells was induced after being scanned 20 times, less than 1/7 of that needed to kill the cells (150 scans). When the laser power was increased to 1.5 mW, apoptosis of cells was induced after only 2 scans, which is only 1/5 of that required to induce necrosis. As a result, at a laser power ranging from 0.5 mW to 1.5 mW, the energy fluence for apoptosis is only about 1/7 to 1/5 (less than 20%) of that for necrosis, which is also two orders of magnitude lower than the medical safety level (100 mJ/cm2) [37]. The thresholds of energy fluence that cause cells necrosis and apoptosis at different laser powers are shown in Fig. 5. Increasing the laser power, the energy fluence for both necrosis and apoptosis was reduced. This can be attributable to the more intense heat production from the gold nanorods at a higher laser power. Apoptosis induction is important to medical applications since proliferation of cancer cells can be inhibited with low energy fluence. This will lead to the destruction of tumors in a safer and less aggressive manner, similar to drug-induced cell apoptosis and tumor damage in chemotherapy and radiotherapy. However, photothermally induced apoptosis can offer a more localized treatment and avoid the harsh side effects that are caused by anticancer drugs and radioactive isotopes. Interestingly, it was observed in a recent work that the photothermal effects of gold nanorods could induce apoptosis of macrophages by damaging the mitochondria [38], which regulates the apoptosis of cells. Whether this mechanism also governs the apoptosis of the cancer cells in this work is an interesting topic. |
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terry_well
榮譽(yù)版主 (知名作家)
笑熬漿糊——滿腦漿糊
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【答案】應(yīng)助回帖
wo357026239(金幣+30): 2012-01-05 19:47:39
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據(jù)觀察，膜出泡一般發(fā)生在壞死性和凋亡性細(xì)胞內(nèi)，并且細(xì)胞膜出泡已普遍被視為細(xì)胞凋亡的先兆[34]。在細(xì)胞凋亡過程中，細(xì)胞骨架的破壞造成了細(xì)胞膜向外凸出[35]。劇烈的飛秒激光脈沖作用下，尤其是金納米棒產(chǎn)生的局部飛秒激光脈沖導(dǎo)致的光熱效應(yīng)可以破壞細(xì)胞內(nèi)的肌動(dòng)蛋白網(wǎng)絡(luò)，而該網(wǎng)絡(luò)它可以為維持細(xì)胞的形狀提供機(jī)械支持[7]。研究發(fā)現(xiàn)，只用幾分鐘即可破壞細(xì)胞的染色體。對(duì)凋亡的細(xì)胞來說，要采用Annexin V Cy3.18獲得足夠的染色處理，所處理的細(xì)胞至少需要培養(yǎng)2小時(shí)。若PI壞死細(xì)胞染色所需時(shí)間短則表明其細(xì)胞膜遭到了破壞。據(jù)觀察，當(dāng)激光功率為2MW（55.6 W/cm2時(shí)）及以上時(shí)，一個(gè)光柵掃描誘導(dǎo)后細(xì)胞膜發(fā)生穿孔（如圖6B所示）。輻照持續(xù)時(shí)間大幅減少可以顯著降低能量密度。 然而，有人提出用這個(gè)功率的激光工作存在潛在的安全隱患。這個(gè)2MW的關(guān)鍵電源/功率密度可視為使用上限。隨著在功率密度降低，熱效應(yīng)成為主導(dǎo)，且熱誘導(dǎo)細(xì)胞損傷成為控制細(xì)胞死亡的只要因素。最新實(shí)時(shí)檢索表明，高能量通量的金納米棒可增強(qiáng)細(xì)胞膜穿孔的研究已經(jīng)報(bào)道。 在癌癥治療方面，顯著減少能源能量密度時(shí)，可通過誘導(dǎo)細(xì)胞凋亡而非使其壞死。例如，在0.5毫瓦時(shí)，掃描20次后可使HeLa癌細(xì)胞發(fā)生誘導(dǎo)凋亡，需要?dú)⑺赖募?xì)胞不到1/7（150掃描）。當(dāng)激光功率的增加1.5兆瓦，只有2掃描即可誘導(dǎo)癌細(xì)胞凋亡，此時(shí)誘發(fā)壞死的只有1 / 5。因此，激光功率范圍從0.5毫瓦到1.5兆瓦，為細(xì)胞凋亡的能源能量密度大約只有1 / 7至1 / 5（低于20％）為壞死，這也比醫(yī)療安全水平低兩個(gè)數(shù)量級(jí)（安全水平為100 mJ/cm2）[37]。圖5給出了在不同的激光功率下導(dǎo)致細(xì)胞壞死和凋亡的能量密度閾值。激光功率的增加會(huì)導(dǎo)致細(xì)胞壞死和凋亡的能量通量減少，這可以歸因于更高功率激光金納米棒所產(chǎn)生的更劇烈的熱效應(yīng)。 因?yàn)榭梢杂玫湍芰客恳种瓢┘?xì)胞的擴(kuò)散，誘導(dǎo)凋亡在醫(yī)療領(lǐng)域具有很重要的作用。這將獲得一個(gè)更安全、更有效地破壞腫瘤的治療方法。而類似的藥物誘導(dǎo)癌細(xì)胞凋亡可導(dǎo)致腫瘤化療和放療損傷。然而，輻照熱誘導(dǎo)細(xì)胞凋亡，可以提供更局部化處理并避免由抗癌藥物和放射性同位素引起的附帶影響。有趣的是，通過最近的工作觀察，金納米棒的光熱效應(yīng)通過破壞其線粒體可誘導(dǎo)巨噬細(xì)胞凋亡，從而調(diào)節(jié)細(xì)胞凋亡[38]。在這個(gè)作用機(jī)制是否也可以用來控制癌細(xì)胞凋亡將是一個(gè)有趣的課題。 太長(zhǎng)了，僅供參考。  |
3樓2012-01-05 17:38:41
【答案】應(yīng)助回帖
wo357026239(金幣+120, 翻譯EPI+1): 2012-01-05 19:47:33
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因其雙光子發(fā)光，金納米棒適用于三維成像。 盡管細(xì)胞的自發(fā)螢光提供了細(xì)胞成像的最簡(jiǎn)單方法，其所需的用來激發(fā)自發(fā)光的高達(dá)35 毫瓦的激光能量為安全性帶來了潛在的威脅。如圖4A所示，即使激光能量低于30 毫瓦，30次光柵掃描后，細(xì)胞即可死亡。當(dāng)能量被提高到35毫瓦時(shí)，可見明顯細(xì)胞穿孔 （圖6A）。 在如此高能量下的激光操作，將引起人們對(duì)醫(yī)療安全的擔(dān)憂。 加入金納米棒可改進(jìn)成像，這是因?yàn)閷?duì)一個(gè)長(zhǎng)寬比為4的金納米棒來說，在其橫截面的雙光子激發(fā)可達(dá)約 ~3 ×104 GM，這比熒光素分子高出三個(gè)數(shù)量級(jí)［32，33］。因此，和傳統(tǒng)的熒光分子相比，金納米棒是優(yōu)秀的對(duì)比度提升劑。 在壞死的細(xì)胞和凋亡的細(xì)胞上皆可觀察到細(xì)胞膜起泡。細(xì)胞膜開始?xì)馀萃ǔ１徽J(rèn)為是細(xì)胞凋亡的前兆［34］。 在細(xì)胞凋亡過程中，細(xì)胞骨架的破壞導(dǎo)致細(xì)胞膜向外鼓出。高強(qiáng)度的飛秒級(jí)激光脈沖，尤其是它所產(chǎn)生的金納米棒區(qū)域光熱效應(yīng)，可破壞提供支撐以維持細(xì)胞形狀的細(xì)胞間肌動(dòng)蛋白網(wǎng)絡(luò)［7］。可以觀察到，壞死細(xì)胞的染色幾分鐘內(nèi)即可完成。使用Annexin V-cy3.18染色凋亡細(xì)胞，充分的染色需要至少2小時(shí)的培養(yǎng)。PI染色短時(shí)間內(nèi)即可完成，說明壞死細(xì)胞的膜已經(jīng)受到了損壞。當(dāng)激光功率為2毫瓦或更高時(shí)，一次光柵掃描后即可觀察到細(xì)胞膜穿孔 （圖6B）。大幅度縮短輻照時(shí)間可明顯減少能量的注入。 然而，如此大功率的激光應(yīng)用，可帶來潛在的安全隱患。此功率／功率比應(yīng)為應(yīng)用中的最上限。當(dāng)功率值下降時(shí)，熱效應(yīng)占據(jù)了主導(dǎo)地位，高溫導(dǎo)致的細(xì)胞損傷成為了細(xì)胞死亡的主要因素。在近期的工作中也有報(bào)導(dǎo)，實(shí)時(shí)觀測(cè)中可見在金納米棒的參與下，高功率輻照引起了更多的細(xì)胞穿孔。 在癌癥治療中，與細(xì)胞壞死相比，引發(fā)細(xì)胞凋亡可明顯降低所需的能量輸入。比如，在0.5毫瓦下，20次掃描即導(dǎo)致hela細(xì)胞凋亡，少于殺死細(xì)胞所需劑量的1/7 （150次掃描）。當(dāng)激光功率提高到1.5毫伏，2次掃描即可導(dǎo)致細(xì)胞凋亡，這是導(dǎo)致細(xì)胞壞死所需的1/5。因此，當(dāng)激光功率處于0.5 -1.5毫伏之間時(shí)，致使細(xì)胞凋亡所需的能量只是導(dǎo)致細(xì)胞壞死所需能量的1/7 到1/5（少于20％），同時(shí)也比醫(yī)療安全值 (100 mJ/cm2)低兩個(gè)數(shù)量級(jí)［37］。在不同激光功率下導(dǎo)致細(xì)胞壞死和凋亡的能量起始值如圖5所示。提高激光功率，致細(xì)胞壞死或凋亡的能量即隨之降低。這可歸因于更高激光功率下，金納米棒產(chǎn)生的熱量更高。 因?yàn)榈湍芰康淖⑷爰纯勺柚拱┘?xì)胞的繁殖，誘使細(xì)胞凋亡對(duì)醫(yī)療中的應(yīng)用非常重要。就像化學(xué)療法和和放射療法中，藥物所導(dǎo)致的細(xì)胞凋亡和腫瘤破壞一樣，這可以獲得一種更安全和平和的方式來破壞腫瘤。然而，光熱法治療所致的細(xì)胞凋亡可更精確的控于局部，避免了抗癌藥及用于輻照治療的同位素所帶來的強(qiáng)烈的副作用［38］。有趣的是，在近期的研究中，科學(xué)家們觀察到金納米棒的光熱效應(yīng)可通過破壞線粒體 （其控制細(xì)胞凋亡），導(dǎo)致巨噬細(xì)胞凋亡［38］。在本實(shí)驗(yàn)中，是否這也是控制癌細(xì)胞凋亡的機(jī)理，仍是一個(gè)有趣的研究題目。 |
2樓2012-01-05 17:01:35
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