Published on July 8th, 2014 | By: April Gocha, PhD0
Self-folding silicon nanostructures mock Venus flytraps to catch single cellsPublished on July 8th, 2014 | By: April Gocha, PhD
The cells within your body are most certainly not created equal. There are many different types of cells, with many vastly different and specialized functions, that work together to create a single, living, breathing organism. (Ahem, that’s you.)
But even within a specific cell type located in a specific region of your body, still not all cells are created equal. They will undoubtedly have at least a few small differences in their DNA—some of which could amount to nothing, and some of which could noticeably alter a host of cellular functions. Heck, one tiny little DNA substitution could even destine that cell to eventually form cancer.
Laboratory science, for these very reasons, has come to appreciate that cells are unique. This mantra is behind the emergence of single-cell assays for a variety of parameters in genomics, proteomics, diagnostics, and more. So interest in tiny tools that can help separate and capture single cells for analysis—the so-called “lab on a chip”—has become a robust area of research.
Somewhat akin to the self-assembling origami nanostructures we’ve reported on before, new research from The Johns Hopkins University (Baltimore, Md.) and the U.S. Army Research Laboratory (Adelphi, Md.) details self-folding biocompatible nanostructures that can gingerly capture single live cells in vitro. The research, published in Nano Letters, holds promise for future in vitro and in vivo techniques of cellular analysis and diagnosis.
Using high-throughput photolithography techniques, the team patterned the little structures, like unfolded gift boxes, with four microscopic triangular arms. Making the structures out of pre-stressed bilayers of silicon monoxide and silicon dioxide made them biocompatible and bioresorbable.
And now for the magic: Placing the little grippers in a warm solution caused a “sacrificial” layer of silicon to dissolve, causing the arms to spontaneously fold upwards. Thicker layers of silicon monoxide were patterned into more rigid hinge shapes to guide the arms to fold upwards, creating a little cell-catching box.
The researchers showed that their lil’ grippers were pretty good at gently nabbing single cells when they tested them with different types of live mouse cells in vitro. With just the right touch—the cells remained viable—the four arms spontaneously folded upward to catch a single cell in a gentle embrace.
The scientists made the nanostructures—10–70 μm in length—into large arrays or as untethered, free-floating grippers. When arrayed, the authors speculate that up to 10 million grippers could potentially be patterned onto a 12-inch silicon wafer for in vitro uses. Free-floating grippers might find potential in vivo use to travel through places like the circulatory system, enhanced with and guided by magnetic elements to control their location.
“Right now the grippers close spontaneously on release from the substrate, so the capture is statistical,” senior author David Gracias says in a Phys.org article. “Elsewhere we have shown with larger grippers that a polymer trigger can be added to make such tools responsive to temperature and even enzymes such as proteases. So the single cell grippers could also be potentially made responsive to single cells when coated with the appropriate recognition elements.”
The paper is “Self-folding single cell grippers” (DOI: 10.1021/nl500136a).
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