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Polymer nanotubes improve connection to brain implants
News and opinions ‘‘This degradation is an important issue since most nanomaterials enter the cell via endocytosis,’’ says Vince Rotello of the University of Massachusetts at Amherst. ‘‘Those of us looking to control intracellular localization of nanoparticles will have to go back to the drawing board.’’ The results indicate that designing intracellular nanoparticles or devices must take into account cathepsin L degradation of surface layers by inhibiting its activity or find a way to bypass the endosome when entering a cell.
453 Lévy believes it could be very challenging to develop nanoparticles able to avoid or rapidly escape the endosome. The alternative route of developing systems that resist cathepsin L degradation is more promising. ‘‘For peptides, this can be achieved using enantiomers or other synthetic analogs that are resistant to protease degradation,’’ he told Nano Today. E-mail address: [email protected] 1748-0132/$ — see front matter doi: 10.1016/j.nantod.2009.10.002
Polymer nanotubes improve connection to brain implants Cordelia Sealy Coating brain implants with conducting polymer nanotubes improves device performance and could potentially increase device longevity, according to new findings from researchers at the University of Michigan [M.R. Abidian et al., Adv. Mater. 21 (2009) 3764]. In the desire to find treatments for neurodegenerative diseases like Parkinson’s or repair function after trauma, efforts have focused on developing implanted neutral electrodes that record and deliver signals from brain tissue. Such implants, which are typically made to/from metals like Au or Pt, have to work for anything from a few hours to years on end. There is a trade-off between the size of these devices and the quality of the signal. Reducing the size of electrodes lessens their invasiveness but increases their impedance, to the detriment of the signal quality. Nanostructured materials offer a promising route to meet the conflicting requirements of smaller size, desirable electronic characteristics and biocompatibility. The University of Michigan researchers have found that coating the microelectrode recording sites of neural implants with poly(3,4-ethylenedioxythiophene) (PEDOT) nanotubes decreases the device impedance and improves sensitivity. The seven-week test of implants in six rats revealed high-quality unit activity (where the signal-tonoise ratio is over 4) in 30% more of the coated devices than uncoated. But the researchers believe that using polymer nanotubes could have additional advantages. Their unique structure could be used to deliver anti-inflammatory or other agents to reduce immune response and local scarring, supporting the longer term use of implants (Fig. 1). ‘‘This study paves the way for smart recording electrodes that can deliver drugs to alleviate the immune response of encapsulation,’’ says Mohammad Reza Abidian. He also adds that the PEDOT nanotubes could be used as a novel method for biosensing to indicate the transition between acute and chronic responses in the brain. PEDOT has already been demonstrated to be biocompatible, while the nanotubes themselves have both high conductivity and good chemical stability.
Figure 1 Illustration of firing neutrons (green structures) communicating with polymer nanotubes. (Credit: Mohammad Reza Abidian.)
‘‘This approach is powerful in that the PEDOT nanotubes help to decrease initial impedance, which is critical for device performance, while having the flexibility to deliver drugs to help control the inflammatory and tissue responses, which will ultimately be necessary for long-term performance of neural electrodes,’’ says Christine E. Schmidt of the University of Texas at Austin. E-mail address: [email protected] 1748-0132/$ — see front matter doi: 10.1016/j.nantod.2009.10.004
453 Lévy believes it could be very challenging to develop nanoparticles able to avoid or rapidly escape the endosome. The alternative route of developing systems that resist cathepsin L degradation is more promising. ‘‘For peptides, this can be achieved using enantiomers or other synthetic analogs that are resistant to protease degradation,’’ he told Nano Today. E-mail address: [email protected] 1748-0132/$ — see front matter doi: 10.1016/j.nantod.2009.10.002
Polymer nanotubes improve connection to brain implants Cordelia Sealy Coating brain implants with conducting polymer nanotubes improves device performance and could potentially increase device longevity, according to new findings from researchers at the University of Michigan [M.R. Abidian et al., Adv. Mater. 21 (2009) 3764]. In the desire to find treatments for neurodegenerative diseases like Parkinson’s or repair function after trauma, efforts have focused on developing implanted neutral electrodes that record and deliver signals from brain tissue. Such implants, which are typically made to/from metals like Au or Pt, have to work for anything from a few hours to years on end. There is a trade-off between the size of these devices and the quality of the signal. Reducing the size of electrodes lessens their invasiveness but increases their impedance, to the detriment of the signal quality. Nanostructured materials offer a promising route to meet the conflicting requirements of smaller size, desirable electronic characteristics and biocompatibility. The University of Michigan researchers have found that coating the microelectrode recording sites of neural implants with poly(3,4-ethylenedioxythiophene) (PEDOT) nanotubes decreases the device impedance and improves sensitivity. The seven-week test of implants in six rats revealed high-quality unit activity (where the signal-tonoise ratio is over 4) in 30% more of the coated devices than uncoated. But the researchers believe that using polymer nanotubes could have additional advantages. Their unique structure could be used to deliver anti-inflammatory or other agents to reduce immune response and local scarring, supporting the longer term use of implants (Fig. 1). ‘‘This study paves the way for smart recording electrodes that can deliver drugs to alleviate the immune response of encapsulation,’’ says Mohammad Reza Abidian. He also adds that the PEDOT nanotubes could be used as a novel method for biosensing to indicate the transition between acute and chronic responses in the brain. PEDOT has already been demonstrated to be biocompatible, while the nanotubes themselves have both high conductivity and good chemical stability.
Figure 1 Illustration of firing neutrons (green structures) communicating with polymer nanotubes. (Credit: Mohammad Reza Abidian.)
‘‘This approach is powerful in that the PEDOT nanotubes help to decrease initial impedance, which is critical for device performance, while having the flexibility to deliver drugs to help control the inflammatory and tissue responses, which will ultimately be necessary for long-term performance of neural electrodes,’’ says Christine E. Schmidt of the University of Texas at Austin. E-mail address: [email protected] 1748-0132/$ — see front matter doi: 10.1016/j.nantod.2009.10.004