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Nano-Surgery

Researchers explore whether micro/nanoscale tools and materials can be used to ... Direct surgery on individual axons using micro devices as surgical tools. Axon Surgery ...

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Nano-Surgery

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    Slide 1:Nano-Surgery for Axon Repair

    Andrew Dunne

    Slide 2:Background

    Injury to the nervous system is a common occurrence after trauma. Unlike some tissues in the body that exhibit self healing, nerve cells that are injured, particularly those in the brain and spinal cord, are incapable of regenerating circuits by themselves to restore neurological function May lead to the loss of sensory/motor function.

    Slide 3:Christopher and Dana Reeve Foundation

    In the USA alone, close to 1.3 million individuals suffer from some form of spinal cord injury and live with permanent neurological dysfunction. Impact on society increases greatly when considering PNS injuries. Demonstrates the need for treatment of nerve injuries motivationmotivation

    Slide 4:Research Areas

    Researchers explore whether micro/nanoscale tools and materials can be used to address this major challenge in neuromedicine. Two Paths: Stimulating axon regeneration The development of new nanoscale tissue scaffold materials Direct surgery on individual axons using micro devices as surgical tools. The create environments that support the growth of new axonsThe create environments that support the growth of new axons

    Slide 5:Axon Surgery

    This approach conceders nerve injury as a subcellular surgical problem in which micro and nano devices are used as instruments to repair of individual axons Central Thesis: Physical rejoining of two severed axon segments will restore axon electrical conduction Beyond existing surgical technologies Obstacles: Technical inability to perform surgical manipulations at a subcellular scale on the axon Progress has been made with testing of microdevices with nanoscale features to perform basic steps of axon repair

    Slide 6:Basic steps

    Removal of injured ends of axons and trimming back to healthy axon segments Separated axon segments being physically brought together Fusing the membranes of apposing axon segments to form a single structurally intact and functional axon.

    Slide 7:Laser Cutting

    Widely investigated method for biological cutting with micron or submicron scale precision Nano-scissors Have been used to cut or ablate whole cells and intracellular elements Chromosomes, mitochondria and microtubules. Use of low energy femtosecond laser pulses to create a high photon concentration in a small area without creating a lot of heat that might damage surrounding axons. Dye labeling typically used to photosensitize the intended targets prior to ablation.

    Slide 8:Experiment

    University of Texas Cut individual axons in nematode (1mm long) Cut size 300-500nm in diameter Cut a axon known to impair worms backward motion. After surgery couldnt move backwards. 24 hours later grew back the severed axon proving the laser didnt damage surrounding tissue.

    Slide 9:Mechanical Cutting

    Miniaturized mechanical cutting to cut individual axons simpler, less costly, does not require dye photosensitization. A Nanoknife Produced using silicon microfabrication and microassembly techniques Demonstrated for precise cutting of a variety of CNS and PNS axons both in vitro and in anesthetized animals in vivo meansmeans

    Slide 10:Nanoknife

    Two microfabricated silicon components Micro fabricated frame and suspension Blade in the shape of an elongated pyramid Frame attached to a rod Micromanipulator holds rod in place during use and delivers cutting stroke. 500m

    Slide 12:Nanoknife continued

    1mm2 frame and pair of serpentine flexures for multiaxial motion Centered blade. Cutting edge: 20nm radius of curvature and about the width of a synaptic cleft Length: fabrication of one to hundreds of microns 20m 100nm 200m

    Slide 13:Experiment

    Extensively tested Highly effective in severing axons (both myelinated and umyelinated) Delivers cut without distorting adjacent segments and avoids mechanical shearing Tested in vivo to address questions of whether miniaturized cutting instruments can be effective under real surgical conditions. Strength Demonstrated by making repeated cuts at axons from the sciatic nerve of a mouse. Precision Targeted removal of short axon segment Mimics the first of the three proposed steps in axon surgical repair 25 m

    Single axon surgery on mouse Isolation of short segment using a Nanoknife Scale = 200 m

    Slide 15:Conclusion

    Different techniques still being tested for the multiple steps in axon repair. Cutting away Moving of axon ends together Fusion of the ends to make it whole This is not a reality yet Techniques from different stages must be brought together and researched even more before micro-technology based axon repair can be used in patients

    Slide 16:Resources

    Change, WC, Hawkes, E, Keller, CG, & Sretavan, DW. (2010, January 25). Axon repair: surgical application at a subcellular scale.John Wiley & Sons, Inc., Retrieved from http://www3.interscience.wiley.com/cgi-bin/fulltext/123261285/HTMLSTART doi: 10.1002/wnan.76 http://en.wikipedia.org/wiki/Axon http://www.christopherreeve.org http://www.utexas.edu/news/2004/12/16/nr_engineering/

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