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Why do you need to extract live cells?
In traditional cell extraction techniques, chemical and biological methods are often used to lyse cells, so that the contents of the cells are exuded for extraction purposes. However, such methods must destroy the cells themselves. In the aging study, the cells are often treated as components, and such methods cannot overcome the errors caused by cell heterogeneity. [1,2]
The new live cell extraction technology solves this problem. This technology uses a micro-syringe to extract only a small amount of cytoplasm or nucleus (pL level) from a specific part of the cell at a time, thereby ensuring cell viability while obtaining a sufficiently analyzed cytoplasm or nucleus to achieve different time points for the same cell. Monitoring of changes overcomes the errors in traditional methods due to cellular heterogeneity. [1,3]
4 common techniques for living cell extraction 
Nano trawl
2. Cell microinjection Glass needle cells Microinjection glass needles are mainly used for injection of large cells. This method mainly uses a glass tube of 0.5 to 5 μm to directly extract the contents from the cells. However, this method often causes cell damage, so there are also laboratories that have developed 100 nm injection needles for extraction. [4,6,7]Actis et al [4] used ion-conducting microscopy combined with micro-injection glass needle to establish a fL-level cell content extraction method. In this method they use a microinjection glass needle containing an organic phase to move the organic phase by pressure to effect extraction. The method they established was able to extract only RNA, mitochondrial DNA expression in HeLa cells without extracting any organelles.
3. FluidFM
Fluid force microscopy uses a hollow atomic force probe to precisely and controlly penetrate the cell membrane through mechanical detection. The cells are then extracted by applying a negative pressure to the tip. According to Guillaume-Gentil et al., cells used this technique to extract up to 90% of the cytoplasm of cells, and the cells remained highly active for 5 days. In addition, they also used this technology to simultaneously extract the nucleus and cytoplasm and perform enzyme assays and PCR experiments. [1,8]
4. Carbon nanotubes Carbon nanotubes are currently mainly used in low-damage cell monitoring. Singhal et al. connected the ends of 50 μm long multi-walled carbon nanotubes to a microporous glass tube to extract fluorescently labeled Ca ions in the cytosol. However, the volume extracted by this method is currently small, and its application is still limited. [5]
to sum up:
Although there are many other methods available today to evaluate the intracellular environment, including fluorescent labels, quantum dots, nanoparticles, FRET, thermosensitive fluorescently labeled antibodies or RNA. These methods provide high specificity, high contrast, and high resolution, but all recognize only a small number of pre-set targets and do not fully monitor intracellular environmental changes. At the same time, the introduction of exogenous materials also carries the risk of adversely affecting cell viability. [3]
In contrast, cell bio-extraction techniques have advantages that these methods cannot match. This technology can maintain the internal environment stability as much as possible while comprehensively monitoring changes in the intracellular environment. The four techniques described in this paper also have their own advantages and disadvantages: nano-trawling can provide a large amount of cell extraction, but can not select the cells to be extracted, and the amount of extraction for different cells is quite different. The micro-injection of the glass needle is complicated, and the glass needle required to directly affect the quality of the injection. FluidFM technology is easy to use and can be accurately positioned, but the technology is relatively new and currently has a small number of users. Carbon nanotubes are still subject to the constraints of their extraction and still need to be developed. [9-10]
references
[1] O. Guillaume-Gentil et al., Cell 166, 506 (2016).
[2] Y. Cao et al., Proc. Natl. Acad. Sci. USA 114, E1866 (2017).
[3] J. Liu, J. Wen, Z. Zhang, H. Liu, Y. Sun, Microsys. Nanoeng. 1,15020 (2015).
[4] P. Actis et al., ACS Nano 8, 546 (2014).
[5] R. Singhal et al., Nat. Nanotechnol. 6, 57 (2011).
[6] W. Kang, RL McNaughton, HD Espinosa, Trends Biotechnol. 34, 665 (2016).
[7] Y. Nashimoto et al., ACS Nano 10, 6915 (2016).
[8] A. Meister et al., Nano Lett. 9, 2501 (2009).
[9] C. Chiappini et al., Nat. Mater. 14, 532 (2015).
[10] AM Xu et al., Nat. Commun. 5, 8 (2014).
Summary of four living cell extraction techniques
Live cell content extraction technology overview
Published on April 28, 2017 in the journal NANOTECHNOLOGY.
The latest adherent live cell extraction technology - Cytosurge multi-function single-cell microscopic operating system FluidFM BOT
Today, monitoring of intracellular expression plays an increasingly important role in the study of cell differentiation, cell senescence, and cytopathic and drug metabolism. This article will summarize the commonly used live cell extraction techniques.
This technique was established by the laboratory of Cao et al. [2-5]. In their experiments, they made 150 nm diameter alumina tubes into nano-trawlers. The cells are then planted on the surface of this trawl. Through these channels, the cell membrane attached to the surface can be punctured, allowing the cell contents to penetrate into the lower extraction buffer, which allows about 7% of the contents to penetrate into the buffer. They pointed out that the extract obtained by this method can be used for experiments such as fluorescent protein, enzyme assay, and PCR. In their study, it was found that the use of this nano-trawl was used in the extraction analysis of iPSc-induced mRNA in cardiomyocytes. They successfully analyzed 44 mRNA sequences, and only 7 were analyzed by conventional lysis methods.