of astrocytes around the electronics and a tight junction between neurons and
unfolded mesh electronics (Fig.5.15f).
To further demonstrate the potential of the geometrical restoration of the
injectable electronics in cavity as well as its uniqueness for potential applications in
cellular therapy, we injected mesh electronics into the cavity of lateral ventricle
region in rat brain to target the subventricular zone region, considering progenitor
cells in this region have proved capability for regeneration and long-distance
migration [ 33 ], which shows potential for neuron replacement therapy [ 34 , 35 ].
Mesh electronics was stereotaxically injected into the lateral ventricle region
through a 200-μm glass needle (Fig.5.15c, II). Mesh electronics in solution is
similar to synthetic polymeric networks. A large volume of mesh electronics can be
continuously injected into the cavity of lateral ventricle to fulfill the cavity and
contact cell walls after unfolding. After 5 weeks, immunostaining of horizontal
slice showed unfolded mesh electronics occupied a volume with 1.5-mm diameter,
which covers the most inner area of lateral ventricle and bridges the lateral walls.
Immunostaining with higher magnification shows that ribbons from mesh elec-
tronics contacted with the caudoputamen have interpenetrated with cells and
merged into the astrocytic-characteristic tube-like structure (Fig.5.15g–i) [ 33 ].
Control experiment from the same rodent shows the same level of glialfibrillary
acidic protein (GFAP) expression, which demonstrates no chronic tissue response
to the electronics. Importantly, image shows a migration of neural outgrowth cells
from both sides of the lateral ventricle cell walls into the interior space of the
unfolded mesh, even in the center of cavity. Those cells formed tight junctions on
the ribbons of electronics in chain-structures and migrated along the direction of
ribbons from mesh electronics (Fig.5.16). Considering the electrophysiological
monitoring capability, these results show a potential application to use injectable
electronics to direct, mobilize and monitor the adult stem neurons from lateral
ventricle region to injured brain region for therapy.
5.4 Conclusion
The methods and mechanical designs introduced here represent new concepts for
electronics fabrication and delivery. The future potential development is to (1) in-
crease the complexity of electronics while keeping its nanoscale-thickness to
maintain the syringe injectable property, (2) investigate different materials as
supporting materials for injectable electronics to achieve the subsequent dissolving
of materials releasing the sensing unit inside the injected subject to allow those unit
to behave like colloidal in the subject for better integration, (3) further develop a
non-surgical implantation bioelectronics and (4) create cellular therapy by using
injectable electronics as scaffold for stem cell delivery, mobilization and
monitoring.
5.3 Results and Discussion 91