title: Two-photon imaging of chronically implanted neural electrodes: Sealing methods and new insights.
abstract: BACKGROUND
  Two-photon microscopy has enabled the visualization of dynamic tissue changes to injury and disease in vivo. While this technique has provided powerful new information, in vivo two-photon chronic imaging around tethered cortical implants, such as microelectrodes or neural probes, present unique challenges.
  
  
  METHODS
  A number of strategies are described to prepare a cranial window to longitudinally observe the impact of neural probes on brain tissue and vasculature for up to 3 months.
  
  
  RESULTS
  It was found that silastic sealants limit cell infiltration into the craniotomy, thereby limiting light scattering and preserving window clarity over time. In contrast, low concentration hydrogel sealants failed to prevent cell infiltration and their use at high concentration displaced brain tissue and disrupted probe performance.
  
  
  CONCLUSIONS
  The use of silastic sealants allows for a suitable imaging window for long term chronic experiments and revealed new insights regarding the dynamic leukocyte response around implants and the nature of chronic BBB leakage in the sub-dural space.
  
  
  CONCLUSIONS
  The presented method provides a valuable tool for evaluating the chronic inflammatory response and the performance of emerging implantable neural technologies.
authors.affiliation: Bioengineering, University of Pittsburgh, USA; Center for the Neural Basis of Cognition, University of Pittsburgh, USA; McGowan Institute for Regenerative Medicine, University of Pittsburgh, USA; NeuroTech Center of the University of Pittsburgh Brain Institute, USA. Electronic address: tdk18@pitt.edu.
authors.forename: Takashi D Y
authors.initials: TD
authors.lastname: Kozai
authors.affiliation: Bioengineering, University of Pittsburgh, USA; Center for the Neural Basis of Cognition, University of Pittsburgh, USA.
authors.forename: James R
authors.initials: JR
authors.lastname: Eles
authors.affiliation: Bioengineering, University of Pittsburgh, USA; Center for the Neural Basis of Cognition, University of Pittsburgh, USA; Radiology, University of Pittsburgh, USA.
authors.forename: Alberto L
authors.initials: AL
authors.lastname: Vazquez
authors.affiliation: Bioengineering, University of Pittsburgh, USA; Center for the Neural Basis of Cognition, University of Pittsburgh, USA; McGowan Institute for Regenerative Medicine, University of Pittsburgh, USA. Electronic address: xic11@pitt.edu.
authors.forename: X Tracy
authors.initials: XT
authors.lastname: Cui
mesh_terms: D000818:Animals; D001921:Brain / Q000502:physiology / Q000601:surgery*; D003399:Craniotomy; D004567:Electrodes, Implanted; D051379:Mice; D008839:Microelectrodes; D036641:Microscopy, Fluorescence, Multiphoton / Q000379:methods*
keywords: Encapsulation; Foreign Body; Giant Cell; Intracortical microelectrode; Intravital imaging; Multiphoton; Reactive tissue response