Many may wonder why we need to fabricate nano structures and nano devices and things like nano dots, nano wires and nano needles. Here is a recent paper in Nature Materials that demonstrates the use of dense array of silicon nano needles used in medicine research to reprogram cells to develop new blood vessels (thanks Wendy at
www.colnatec.com for sharing this one). Just imagine the huge potential for this technology in giving blood in the future! You could just have a constant supply of fresh blood cells added to the system when needed or regenerate faster after giving blood.
So back to why do we need nano needles in this case? First of all the average person does´t like needles at all it bloody hurts! "In cell perspective needles also do damage and models suggest that the cell membrane cannot recover if it is perforated by anything larger than 500 nm" - that´s half a micron, microtechnology, old technology - Here is a clear call for nanotechnology!
That is why Tascotti and his colleagues had to go through a pretty advanced nano patterning and structuring process flow to create arrays of silicon based nano needles as described by
Materials 360 Online and seen in Figure 1 from the publication in Nature Materials below:
"To create their nanoneedles, Tasciotti and his colleagues first deposited silicon nitride onto biodegradable silicon wafers using chemical vapor deposition, and then patterned nanoneedles onto their substrate using photolithography. Next, they formed porous silicon pillars using metal-assisted chemical etching, which they then shaped into nanoneedles with reactive ion etching. Importantly, the porosity of the nanoneedles could be tailored between 45% and 70%, which allows their degradation time, payload volume, and mechanical properties to be fine-tuned. The resulting nanoneedles, which were on 8 × 8 mm2chips, were 5 μm long, 50 nm wide at the apex, and 600 nm at the base. Compared with a solid cylindrical nanowire of equivalent apical diameter, the nanoneedles had more than 300 times the surface area for payload adsorption."
Biodegradable silicon nanoneedles delivering nucleic acids intracellularly induce localizedin vivo neovascularization
C. Chiappini, E. De Rosa, J. O. Martinez, X. Liu, J. Steele, M. M. Stevens & E. Tasciotti
The controlled delivery of nucleic acids to selected tissues remains an inefficient process mired by low transfection efficacy, poor scalability because of varying efficiency with cell type and location, and questionable safety as a result of toxicity issues arising from the typical materials and procedures employed. High efficiency and minimal toxicity in vitro has been shown for intracellular delivery of nuclei acids by using nanoneedles, yet extending these characteristics to in vivo delivery has been difficult, as current interfacing strategies rely on complex equipment or active cell internalization through prolonged interfacing. Here, we show that a tunable array of biodegradable nanoneedles fabricated by metal-assisted chemical etching of silicon can access the cytosol to co-deliver DNA and siRNA with an efficiency greater than 90%, and that in vivo the nanoneedles transfect the VEGF-165gene, inducing sustained neovascularization and a localized sixfold increase in blood perfusion in a target region of the muscle.
Figure 1 | Porous silicon nanoneedles. a, Schematic of the nanoneedle synthesis combining conventional microfabrication and metal-assisted chemical etch (MACE). RIE, Reactive ion etching. b,c, SEM micrographs showing the morphology of porous silicon nanoneedles fabricated according to the process outlined in a. b, Ordered nanoneedle arrays with pitches of 2 μm, 10 μm and 20 μm, respectively. Scale bars, 2 μm. c, High-resolution SEM micrographs of nanoneedle tips showing the nanoneedles’ porous structure and the tunability of tip diameter from less than 100 nm to over 400 nm. Scale bars, 200 nm. d, Time course of nanoneedles incubated in cell-culture medium at 37 ◦ C. Progressive biodegradation of the needles appears, with loss of structural integrity between 8 and 15 h. Complete degradation occurs at 72 h. Scale bars, 2 μm. e, ICP-AES quantification of Si released in solution. Blue and black bars represent the rate of silicon release per hour and the cumulative release of silicon, respectively, at each timepoint, expressed as a percentage of total silicon released. Error bars represent the s.d. of 3–6 replicates. (Nature Publishing Group, License Number: 3630681325690).
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