Routine lab work to examine a host of biological parameters often depends on destructively lysing, or bursting, cells to release their contents for measurement. While this simple technique has been used for decades, it creates a constraint on protocol design because a given cell can only be analyzed once (when lysed) in a snapshot-like manner. A new technique developed at Stanford University enables researchers to non-destructively sample a cell’s interior, thus allowing for dynamic monitoring of the same cell over multiple time-points.
Inspired by natural gates (gap junctions) that allow cells to exchange substances, the Stanford team built an array of nano-scale hollow tubes 600 times thinner than a human hair. Cells grown on this Nanostraw Extraction (NEX) platform are subjected to a momentary electrical current, freeing some of the cellular contents to diffuse out and through the nanostraws for collection and analysis by standard lab techniques, such as ELISA or PCR. Coupling a transient current with these nanostraws allows the researchers to take multiple snapshots of a cell’s interior without killing it.
The Stanford team tested the NEX platform on cell lines and human stem-cell derived heart and brain cells for up to 20 days, showing that it did not alter cell survival or morphology. Demonstrating the versatility of NEX sampling, the investigators measured levels of constant and dynamic fluorescent proteins over multiple days, showing high correlation with measurements from conventional lysis techniques. Notably, NEX can sample all regions of a cell’s cytoplasm, is consistent with lysis controls for measuring functional proteins and mRNA levels, and its function is unaffected by a dynamic culture such as beating heart cells.
Although the researchers have demonstrated an ability to interrogate biological parameters at a single-cell level by manipulating the area containing nanostraws, the platform necessitates an additional step to concentrate or amplify the extracted proteins and RNA – a step that will hopefully be eliminated as more sensitive assay technologies are developed. In the meantime, the NEX platform promises to revolutionize dynamic assays, such as those studying stem cell development or transient drug responses.
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