biocompatibility of polyimide based neural devices for chronic...
TRANSCRIPT
-
Biocompatibility of Biocompatibility of Polyimide Based Neural Polyimide Based Neural
Devices for Chronic Devices for Chronic Implant Applications Implant Applications
Samantha WatkinsSamantha WatkinsAdvisor: Dr. Patrick J. Advisor: Dr. Patrick J. RouscheRousche
Neural Engineering & Applications LabNeural Engineering & Applications Lab
Gandhi, D 2006 Assessing Chronic Functionality of Photo-Definable Polyimide Based Flexible Neural Interface for the Central Nervous System Preliminary Thesis PhD. Defense Summary.
-
Neural Device Neural Device ApplicationsApplications
Gandhi, D 2006 Assessing Chronic Functionality of Photo-Definable Polyimide Based Flexible Neural Interface for the Central Nervous System Preliminary Thesis PhD. Defense Summary. & http://bryanbrandenburg.blog.com/Biomedical/
NeuroNeuro Prosthesis Prosthesis –– Restore functionality in Restore functionality in
central nervous system central nervous system tissuetissue
–– Information exchange Information exchange Delivering and recording Delivering and recording electrical signals to and from electrical signals to and from neuronal cellsneuronal cells
Assess the physiological Assess the physiological environment at a cellular environment at a cellular levellevel
-
LongLong--Term Term BiocompatibilityBiocompatibility
Minimize foreign body response and immune reactionMinimize foreign body response and immune reactionDecrease the risk of scar tissue formationDecrease the risk of scar tissue formation–– Preventing device isolation from surrounding neural tissue Preventing device isolation from surrounding neural tissue
((gliosisgliosis))
The interface should also reduce mechanical The interface should also reduce mechanical micromotionmicromotionstrain which further reduces strain which further reduces gliosisgliosis
Stimulation & RecordingFunctionality
Brain TissueAcceptance
Gandhi, D 2006 Assessing Chronic Functionality of Photo-Definable Polyimide Based Flexible Neural Interface for the Central Nervous System Preliminary Thesis PhD. Defense Summary.
-
Mechanical ComplianceMechanical Compliance
Mechanical mismatch between materialsMechanical mismatch between materials–– Polyimide has a YoungPolyimide has a Young’’s Modulus 25s Modulus 25--100 times lower than other 100 times lower than other
materialsmaterialsPolyimide flexibility causes buckling during insertionPolyimide flexibility causes buckling during insertionEnhance device strength by with Enhance device strength by with polyglycolicpolyglycolic acid (PGA)acid (PGA)
Mechanical RigidityMechanical Rigidity
MaterialMaterial YoungYoung’’s Moduluss ModulusTungsten Tungsten MicrowireMicrowire 400 400 GPaGPa
SiliconSilicon 120120--140 140 GPaGPa
PolyimidePolyimide 4 4 GPaGPa
Brain TissueBrain Tissue 0.067 0.067 GPaGPa
-
PGA MaterialPGA Material
Mechanical rigidityMechanical rigidity–– YoungYoung’’s Modulus s Modulus --> 7GPa> 7GPa
FDA approved and biodegradable suture materialFDA approved and biodegradable suture materialGlass transition temperature Glass transition temperature --> 35> 3500CC–– Stable at room temperatures Stable at room temperatures
and degrades once implantedand degrades once implanted
MeltMelt--coating polyimide coating polyimide devices for implant devices for implant applicationsapplications
–– OneOne--sided coatingsided coating
-
Polymer Material Polymer Material CharacterizationCharacterization
Utilize polymerUtilize polymer--based devices to assess based devices to assess biocompatibility of neural implants in biocompatibility of neural implants in chronic applicationschronic applications–– Uncoated polyimide devicesUncoated polyimide devices–– PGA coated polyimide devicesPGA coated polyimide devices
Monitor tissue response with histology Monitor tissue response with histology techniquestechniques
4 0 0 μm1 4 6 -1 5 6 μm
1 0 0 0 0 μm 4 0 0 0 μm
4 0 0 μm1 4 6 -1 5 6 μm
1 0 0 0 0 μm 4 0 0 0 μm
1 0 0 0 0 μm 4 0 0 0 μm
1 0 0 0 0 μm 4 0 0 0 μm4 0 0 0 μm
Gandhi, D 2006 Assessing Chronic Functionality of Photo-Definable Polyimide Based Flexible Neural Interface for the Central Nervous System Preliminary Thesis PhD. Defense Summary.
-
Histology MethodsHistology Methods
Device implantDevice implant-- 15 days15 daysFormalin fixationFormalin fixationParaffin embeddingParaffin embedding88μμm sectionsm sectionsH&E stainingH&E staining–– Cell DistributionCell Distribution
Immunochemistry stainingImmunochemistry staining–– GlialGlial fibrillaryfibrillary acidic protein (GFAP), acidic protein (GFAP),
astrocyteastrocyte--specific marker specific marker –– GlialGlial scar formationscar formation
BrightfieldBrightfield microscopy imagingmicroscopy imaging2 Shaft Polyimide Device
500 um
-
H&E Results H&E Results ––Uncoated Polyimide DevicesUncoated Polyimide Devices
Sections of four implants Sections of four implants at varying depthsat varying depthsNormal cell interactionNormal cell interaction
100 um
100 um 100 um100 um
-
H&E Results H&E Results ––PGA Coated DevicesPGA Coated Devices
Sections of three implants Sections of three implants at varying depthsat varying depthsNormal cell behaviorNormal cell behavior–– OneOne--sided responsesided response
100 um 100 um100 um
100 um
-
GFAP Immunochemistry GFAP Immunochemistry Results Results –– Uncoated Polyimide Uncoated Polyimide DevicesDevices
Sections of two implants at Sections of two implants at varying depthsvarying depthsMinimal Minimal glialglial scar scar formation formation
100 um
100 um
100 um 100 um
-
GFAP ImmunochemistryGFAP ImmunochemistryResults Results —— PGA Coated DevicesPGA Coated Devices
Sections of three implants Sections of three implants at varying depthsat varying depthsMinimal Minimal glialglial scar scar formation formation –– OneOne--sided responsesided response
100 um 100 um 100 um
100 um
-
ConclusionConclusion
Polyimide material provides mechanical flexibility to Polyimide material provides mechanical flexibility to reduce reduce micromotionmicromotion strainstrainPGA material provides temporary mechanical PGA material provides temporary mechanical rigidity for insertionrigidity for insertion–– In vitro studies in our lab suggest PGA degrades within In vitro studies in our lab suggest PGA degrades within
three daysthree days
Histology results show successful biocompatibility of Histology results show successful biocompatibility of polymer materials with only a slight tissue responsepolymer materials with only a slight tissue responsePolymer materials provide new design strategies for Polymer materials provide new design strategies for
neural devices used in longneural devices used in long--term implantsterm implants
-
AcknowledgementsAcknowledgements
Grant NSF EEC 0453432Grant NSF EEC 0453432–– National Science Foundation REU National Science Foundation REU
Program Program –– Department of Defense ASSURE ProgramDepartment of Defense ASSURE ProgramDr. Dr. Rousche'sRousche's Research TeamResearch Team–– DevangDevang GandhiGandhi–– Peter Peter TekTek
Biocompatibility of Polyimide Based Neural Devices for Chronic Implant Applications Neural Device ApplicationsLong-Term BiocompatibilityMechanical CompliancePGA MaterialPolymer Material CharacterizationHistology MethodsH&E Results – �Uncoated Polyimide DevicesH&E Results – �PGA Coated DevicesGFAP Immunochemistry �Results – Uncoated Polyimide DevicesGFAP Immunochemistry�Results — PGA Coated DevicesConclusionAcknowledgements