圖1:細胞存活率檢測 A)原生細胞的體積分布圖,虛線為平均值,點線為最大值和最小值;B)細胞提取體積與活細胞數(shù)之間的關系。C)活細胞細胞核提取后GFP 的變化;D)死細胞細胞核提取后GFP 的變化;E)活細胞提取后(2.9 pL)后對細胞形態(tài)的連續(xù)觀測。
3.使用FluidFM 單細胞提取物的三種應用
3.1 透射電鏡負染色觀測
對于細胞亞結(jié)構的觀察,往往對于揭示細胞病變有著重要的意義。然而細胞裂解的傳統(tǒng)手段往往會產(chǎn)生大量的碎片,因此對細胞器的觀察造成了諸多困難。在本篇報道中,作者通過使用FluidFM 設備提取細胞內(nèi)容物,在低溫環(huán)境下轉(zhuǎn)移到透射電鏡的銅網(wǎng)上,然后進行負染色和揮干,之后將片子放到透射電鏡下觀察,并使用傳統(tǒng)裂解方法得到單細胞溶液同時鋪設在銅網(wǎng)上進行對比。通過觀察他們發(fā)現(xiàn),使用FluidFM 技術得到的細胞提取物能夠觀察到大泡狀的結(jié)構、小球狀的結(jié)構和長絲類的結(jié)構,如圖2C 所示。而相比之下細胞裂解法得到的結(jié)果卻不盡人意,如圖2D 所示。
圖2:細胞提取物負染色電鏡圖 A)電鏡樣本制作的示意圖;B)提取液滴在電鏡銅網(wǎng)上的放大圖;C)FluidFM 技術的細胞提取物電鏡下的圖像;D)普通裂解法的細胞提取物電鏡下的圖像。
3.2 酶活力的檢測
酶活力的檢測對于探尋細胞異質(zhì)性有著十分重要的意義。因此作者也對FluidFM 提取的細胞提取物進行了對比。首先作者通過β-半乳糖苷酶實驗來測定提取蛋白的完整性。通過測定酶解底物產(chǎn)生的熒光素的熒光強度,他們成功觀察到熒光強度隨時間而增加,說明提取物中的蛋白沒有被破壞,如圖3C、D 所示。隨后作者又對不同細胞進行了不同酶活力的檢驗,結(jié)果顯示無論是LacZ 轉(zhuǎn)基因HeLa 細胞上還是在測定HeLa 細胞的Caspase3 酶上均取得了成功,如圖3 E、F 所示。
圖3:酶活性分析 A)細胞提取分析的示意圖;B)將提取的3 pL 細胞提取物放到預先液封的微孔中;C)酶解底物產(chǎn)生熒光素的熒光強度變化,熒光在1 小時后可見。D)圖形量化熒光強度時間表;E)LacZ 轉(zhuǎn)基因細胞和非轉(zhuǎn)基因細胞之間β-半乳糖苷酶活性的差異;F)Caspase3 酶活力測定。
4.3 單細胞級轉(zhuǎn)錄檢測
單細胞層面的基因表達通常需要反轉(zhuǎn)錄或者PCR 擴增,之后使用qPCR 測定。而在此之前往往需要將細胞裂解,而作者他們采用了與傳統(tǒng)方法不同的策略。他們首先創(chuàng)建了使用FluidFM 直接從活細胞中提取大約0.01 pg RNA,并用普通PCR 管合成cDNA 并進行qPCR 檢測,如圖4A 所示。由于如此小的提取量是不能直接放到PCR 管里面的,所以他們采取的策略是首先將提取液注入1uL 水中,然后再轉(zhuǎn)移到PCR 管中,進行合成和檢測如圖6B 所示。他們檢測了兩種管家基因beta-actin (ACTB)beta-2-microglobulin (B2M)以及GFP mRNA 的表達量。在21 個樣本中有90%的樣本成功檢測到至少1 中基因的表達,其中2/3 的樣本可以同時檢測到三種基因的表達。而對細胞核的檢測中,也能夠檢測到至少一種基因的表達,如圖4C 所示。在對比同一細胞同時提取細胞質(zhì)(1.7 pL)和細胞核(1.3 pL)中這三種基因的表達時,可以發(fā)現(xiàn)兩者基本相同,如圖4D 所示。
圖4: A)單細胞提取mRNA 轉(zhuǎn)錄實驗的示意圖;B)將提取物放入液滴中的方法;C) ERCC spike 為對照,測定細胞質(zhì)中GFP、B2M、ACTB 的Ct 值;D)對同一細胞的細胞質(zhì)與細胞核進行提取并測定Ct 值。
總結(jié)
隨著生物研究越發(fā)趨于微觀化,對于分析單個細胞的需求變得越來越大。但是由于單個細胞體積小,所能夠提取出的物質(zhì)相比以前細胞群落分析來說,難度顯著提高。這不僅對檢測儀器的靈敏度有了新的更高的要求,也同時對樣本本身的質(zhì)量也提出了更高的指標。本篇中使用FluidFM 提取活細胞所取得的樣本質(zhì)量相比于傳統(tǒng)裂解手段有了明顯的提高,從而取得了令人滿意的結(jié)果。另外這種方法控制提取量后,甚至能夠做到不殺死細胞的情況下完成提取,這使得對于對單個細胞代謝測定的追蹤成為了可能。
多功能單細胞顯微操作系統(tǒng)
瑞士 Cytosurge FluidFM BOT
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產(chǎn)品簡介:
多功能單細胞顯微操作系統(tǒng)--FluidFM BOT,是將原子力系統(tǒng)、微流控系統(tǒng)、細胞培養(yǎng)系統(tǒng)為一體的單細胞操作系統(tǒng)。主要功能包括單細胞注射、單細胞提取以及單細胞分離。
FluidFM BOT 極大的方便了單細胞水平的研究,尤其適合應用于精準醫(yī)療、單細胞生物學、單細胞質(zhì)譜、單細胞基因編輯、藥物研發(fā)等領域。
注射、提取、分選
一體化的單細胞操縱解決方案
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