FIG. 3.
(A, a) Nanoelectrodes as a minimally invasive wireless device for recording neuronal activities in model animals. (b) Left side of the photo shows traditional bulk implants while the right image displays nanoscale implants as an open, stretchable and flexible framework that induce fewer immune reactions. These networks allow access to many more astrocytes and microglial cells and can be activated at the surface of bulk implants. (c) Multiple forms of signal transduction in neuronal synapses. (d) The size-shrink of metal conductors or semiconductors and change of behavior of iron oxide from paramagnetic to superparamagnetic at the nanoscale compared with bulk-size properties. FETs are gated more easily when nanoscale channels are implemented. Also, nanoscale patterns can lead to a neural response that cannot be detected in a planar neural substrate. (e) The synaptic spaces and several other subcellular spaces are crowded and dynamic. Nanoscale signal transduction can record activities with much higher precision in these crowded spaces compared with traditional methods. (f) Recordings show different signal shapes and amplitudes on different sites of a single neuron. Traces 1–4 show extracellular signal recordings whereas traces I–III show intracellular recordings from micropipettes. All of panel A adopted from Taylor and Francis.69 (B) Polymeric nanoparticles employed for targeted drug delivery. (i) Schematic representation of paclitaxel-loaded Angiopep-PEG-PCL nanoparticles. (ii) Angiopep-conjugation increased the targeting efficiency of brain tumors.70 (C) A 3D printed implant, 2-mm in thickness, is used as scaffolding to repair spinal cord injuries in rats. The H shape in the center is the location of the spinal cord and the dots surrounding it are hollow spaces through which stem cell neural implants extend axons into the host tissues.71 PCL, poly(ɛ-caprolactone).