Summary

Экологически-контролируемое Microtensile Тестирование Механически адаптивных полимерных нанокомпозитов для<em> Экс естественных условиях</em> Характеристика

Published: August 20, 2013
doi:

Summary

Метод обсуждается в котором<em> В естественных условиях</em> Механические свойства раздражителей аспекты материалов как функцию времени. Образцы испытывают<em> Экс естественных условиях</em> Использование microtensile тестер с экологическим контролем для имитации физиологической среде. Эта работа способствует дальнейшему пониманию<em> В естественных условиях</em> Поведение нашем материале.

Abstract

Implantable microdevices are gaining significant attention for several biomedical applications1-4. Such devices have been made from a range of materials, each offering its own advantages and shortcomings5,6. Most prominently, due to the microscale device dimensions, a high modulus is required to facilitate implantation into living tissue. Conversely, the stiffness of the device should match the surrounding tissue to minimize induced local strain7-9. Therefore, we recently developed a new class of bio-inspired materials to meet these requirements by responding to environmental stimuli with a change in mechanical properties10-14. Specifically, our poly(vinyl acetate)-based nanocomposite (PVAc-NC) displays a reduction in stiffness when exposed to water and elevated temperatures (e.g. body temperature). Unfortunately, few methods exist to quantify the stiffness of materials in vivo15, and mechanical testing outside of the physiological environment often requires large samples inappropriate for implantation. Further, stimuli-responsive materials may quickly recover their initial stiffness after explantation. Therefore, we have developed a method by which the mechanical properties of implanted microsamples can be measured ex vivo, with simulated physiological conditions maintained using moisture and temperature control13,16,17.

To this end, a custom microtensile tester was designed to accommodate microscale samples13,17 with widely-varying Young’s moduli (range of 10 MPa to 5 GPa). As our interests are in the application of PVAc-NC as a biologically-adaptable neural probe substrate, a tool capable of mechanical characterization of samples at the microscale was necessary. This tool was adapted to provide humidity and temperature control, which minimized sample drying and cooling17. As a result, the mechanical characteristics of the explanted sample closely reflect those of the sample just prior to explantation.

The overall goal of this method is to quantitatively assess the in vivo mechanical properties, specifically the Young’s modulus, of stimuli-responsive, mechanically-adaptive polymer-based materials. This is accomplished by first establishing the environmental conditions that will minimize a change in sample mechanical properties after explantation without contributing to a reduction in stiffness independent of that resulting from implantation. Samples are then prepared for implantation, handling, and testing (Figure 1A). Each sample is implanted into the cerebral cortex of rats, which is represented here as an explanted rat brain, for a specified duration (Figure 1B). At this point, the sample is explanted and immediately loaded into the microtensile tester, and then subjected to tensile testing (Figure 1C). Subsequent data analysis provides insight into the mechanical behavior of these innovative materials in the environment of the cerebral cortex.

Protocol

1. Подготовка образцов Подготовьте ПВА-NC пленки толщиной в диапазоне 25-100 мкм, с использованием литья решения и технологии сжатия 10-12. Придерживаться пленки на кремниевой пластине при нагревании на горячей плите в течение двух минут при 70 ° С (выше температуры стеклован?…

Representative Results

Механические свойства практически всех полимерных материалов, в том числе наши ПВА-NC, зависят от воздействия окружающей среды. В частности, они включают воздействием тепла и влаги. Когда материал является пластифицированный благодаря поглощению влаги или претерпевает фазовый перехо?…

Discussion

Продвижение имплантируемых биомедицинских микроэлектромеханических систем (BioMEMS) для взаимодействия с биологическими системами мотивирует развитие новых материалов с высокой заданными свойствами. Некоторые из этих материалов предназначены для демонстрируют изменение свойств мат?…

Disclosures

The authors have nothing to disclose.

Acknowledgements

Эта работа была поддержана Департаментом биомедицинской инженерии в Case Western Reserve University через обе лаборатории запуска средства (J. Capadona) и Medtronic стипендий (К. Поттер). Дополнительное финансирование на этом исследовании была частично поддержана грантом NSF ECS-0621984 (С. Zorman), Case Ассоциации выпускников (С. Zorman), Департамент по делам ветеранов через Премия заслуги обзора (B7122R), а также Advanced Платформа технический центр (C3819C).

Materials

Name of Reagent/Material Company Catalogue Number Comments
Silicon wafer University Wafer   Mechanical grade
Extruded acrylic sheet Professional Plastics SACR 062EF Thickness 0.062″
Razor blade McMaster-Carr 3962A3  
Tweezers McMaster-Carr 8384A47 #5 tip
Super Glue Gel Loctite 130380  
Air Brush Snap-on Industrial BF175TA  
Air Compressor Paasche B002YKN8YO D500
Thermocouple Omega HH12A  
Hot plate Cimarec SP131325Q  
CO2 direct-write laser VersaLaser 3.5  
Dessicator Fisher Scientific 08-595  
Lamp     custom-built
Microtensile tester     custom-built

References

  1. Chen, P. J., Saati, S., Varma, R., Humayun, M. S., Tai, Y. C. Wireless intraocular pressure sensing using microfabricated minimally invasive flexible-coiled LC sensor implant. Journal of Microelectromechanical Systems. 19, 721-734 (2010).
  2. Ren, X., Zheng, N., Gao, Y., Chen, T., Lu, W. Biodegradable three-dimension micro-device delivering 5-fluorouracil in tumor bearing mice. Drug Delivery. 19, 36-44 (2012).
  3. Bai, Q. Single-unit neural recording with active microelectrode arrays. IEEE Transactions on Biomedical Engineering. 48, 911 (2001).
  4. Rousche, P. J., Pellinen, D. S., Pivin, D. P., Williams, J. C., Vetter, R. J., kirke, D. R. Flexible polyimide-based intracortical electrode arrays with bioactive capability. IEEE Transactions on Biomedical Engineering. 48, 361-371 (2001).
  5. Hassler, C., Boretius, T., Stieglitz, T. Polymers for neural implants. Journal of Polymer Science Part B: Polymer Physics. 49, 18-33 (2011).
  6. Mercanzini, A., Colin, P., Bensadoun, J. C., Bertsch, A., Renaud, P. In Vivo Electrical Impedance Spectroscopy of Tissue Reaction to Microelectrode Arrays. IEEE Transactions on Biomedical Engineering. 56, 1909-1918 (2009).
  7. Polikov, V. S., Tresco, P. A., Reichert, W. M. Response of brain tissue to chronically implanted neural electrodes. Journal of Neuroscience Methods. 148, 1-18 (2005).
  8. Subbaroyan, J., Kipke, D. Engineering in Medicine and Biology Society, 2006. , 3588-3591 (2006).
  9. Harris, J., Capadona, J., Miller, R., Healy, B., Shanmuganathan, K., Rowan, S., Weder, C., Tyler, D. Mechanically adaptive intracortical implants improve the proximity of neuronal cell bodies. Journal of Neural Engineering. 8, 066011 (2011).
  10. Capadona, J. R., Shanmuganathan, K., Tyler, D. J., Rowan, S. J., Weder, C. Stimuli-Responsive Polymer Nanocomposites Inspired by the Sea Cucumber Dermis. Science. 319, 1370-1374 (2008).
  11. Shanmuganathan, K., Capadona, J. R., Rowan, S. J., Weder, C. Stimuli-Responsive Mechanically Adaptive Polymer Nanocomposites. ACS Applied Materials & Interfaces. 2, 165-174 (2009).
  12. Shanmuganathan, K., Capadona, J. R., Rowan, S. J., Weder, C. Bio-inspired mechanically-adaptive nanocomposites derived from cotton cellulose whiskers. Journal of Materials Chemistry. 20, 180 (2010).
  13. Hess, A., Capadona, J., Shanmuganathan, K., Hsu, L., Rowan, S., Weder, C., Tyler, D., Zorman, C. Development of a stimuli-responsive polymer nanocomposite toward biologically optimized, MEMS-based neural probes. Journal of Micromechanics and Microengineering. 21, 054009 (2011).
  14. Capadona, J. R., Tyler, D. J., Zorman, C. A., Rowan, S. J., Weder, C. Mechanically adaptive nanocomposites for neural interfacing. Materials Research Society Bulletin. 37, 581-589 (2012).
  15. Ophir, J., Cespedes, I., Garra, B., Ponnekanti, H., Huang, Y. Elastography: ultrasonic imaging of tissue strain and elastic modulus in vivo. European journal of ultrasound. 3, 49-70 (1996).
  16. Hess, A., Shanmuganathan, K., Capadona, J., Hsu, L., Rowan, S., Weder, C., Tyler, D., Zorman, C. Micro Electro Mechanical Systems (MEMS). , 453-456 (2011).
  17. Harris, J. P., Hess, A. E., Rowan, S. J., Weder, C., Zorman, C. A., Tyler, D. J., Capadona, J. R. In vivo deployment of mechanically adaptive nanocomposites for intracortical microelectrodes. Journal of Neural Engineering. 8, 046010 (2011).
  18. Shanmuganathan, K. . Bio-inspired Stimuli-responsive Mechanically Dynamic Nanocomposites. , (2010).
  19. Rousche, P. J., Pellinen, D. S., Pivin, D. P., Williams, J. C., Vetter, R. J., Kipke, D. R. Flexible polyimide-based intracortical electrode arrays with bioactive capability. IEEE Transactions on Biomedical Engineering. 48, 361-371 (2001).
  20. Norlin, P., Kindlundh, M., Mouroux, A., Yoshida, K., Hofmann, U. G. A 32-site neural recording probe fabricated by DRIE of SOI substrates. Journal of Micromechanics and Microengineering. 12, 414 (2002).
  21. Ward, M. P., Rajdev, P., Ellison, C., Irazoqui, P. P. Toward a comparison of microelectrodes for acute and chronic recordings. Brain Research. 1282, 183-200 (2009).
  22. Lin, J. M., Chang, P. K. A Novel Remote Health Monitor with Replaceable Non-Fragile Bio-Probes on RFID Tag. Applied Mechanics and Materials. 145, 415-419 (2012).
  23. Kunzelman, K. S., Cochran, R. Stress/strain characteristics of porcine mitral valve tissue: parallel versus perpendicular collagen orientation. Journal of Cardiac Surgery. 7, 71-78 (1992).
  24. Snedeker, J., Niederer, P., Schmidlin, F., Farshad, M., Demetropoulos, C., Lee, J., Yang, K. Strain-rate dependent material properties of the porcine and human kidney capsule. Journal of Biomechanics. 38, 1011-1021 (2005).
  25. Ahn, S., Kasi, R. M., Kim, S. C., Sharma, N., Zhou, Y. Stimuli-responsive polymer gels. Soft Matter. 4, 1151-1157 (2008).
  26. Stuart, M. A. C., et al. Emerging applications of stimuli-responsive polymer materials. Nature Materials. 9, 101-113 (2010).

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Cite This Article
Hess, A. E., Potter, K. A., Tyler, D. J., Zorman, C. A., Capadona, J. R. Environmentally-controlled Microtensile Testing of Mechanically-adaptive Polymer Nanocomposites for ex vivo Characterization. J. Vis. Exp. (78), e50078, doi:10.3791/50078 (2013).

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