Neurite Outgrowth on Electrospun Nanofibers with Uniaxial Alignment: The Effects of Fiber Density, Surface Coating, and Supporting Substrate

Electrospun nanofibers with uniaxial alignment have recently gained its popularity as scaffolds for neural tissue engineering. Many studies have demonstrated that the nanofibers could guide the neurites to extend along the direction of alignment, resembling the native hierarchy of the nerve tissue. However, the contact cues provided by the nanofibers can be far more complicated than just guiding the neurites to extend along them. In the current study, we used dorsal root ganglia as a model system to systematically investigate the interactions between neurites and uniaxially aligned nanofibers. We demonstrated, for the first time, that the neurites could not only project along the nanofibers, but also be directed to grow along a direction perpendicular to the aligned nanofibers, depending on the following parameters: (i) the density of nanofibers, (ii) the protein deposited on the surfaces of the nanofibers, and (iii) surface properties of the substrate on which the nanofibers were supported. We also investigated the pharmacological effect of myosin II inhibition on the nanofiber-guided growth of neurites by adding blebbistatin to the culture medium. Our findings offer new insights into the design of nanofiber-based scaffolds for nerve injury repair and will provide new guidelines for the construction of well-defined neuronal network architecture (the so-called neural circuits)

Neurite Outgrowth on Electrospun Nanofibers with Uniaxial Alignment: The Effects of Fiber Density, Surface Coating, and Supporting Substrate

Electrospun nanofibers with uniaxial alignment have recently gained its popularity as scaffolds for neural tissue engineering. Many studies have demonstrated that the nanofibers could guide the neurites to extend along the direction of alignment, resembling the native hierarchy of the nerve tissue. However, the contact cues provided by the nanofibers can be far more complicated than just guiding the neurites to extend along them. In the current study, we used dorsal root ganglia as a model system to systematically investigate the interactions between neurites and uniaxially aligned nanofibers. We demonstrated, for the first time, that the neurites could not only project along the nanofibers, but also be directed to grow along a direction perpendicular to the aligned nanofibers, depending on the following parameters: (i) the density of nanofibers, (ii) the protein deposited on the surfaces of the nanofibers, and (iii) surface properties of the substrate on which the nanofibers were supported. We also investigated the pharmacological effect of myosin II inhibition on the nanofiber-guided growth of neurites by adding blebbistatin to the culture medium. Our findings offer new insights into the design of nanofiber-based scaffolds for nerve injury repair and will provide new guidelines for the construction of well-defined neuronal network architecture (the so-called neural circuits)

Expanding Two-Dimensional Electrospun Nanofiber Membranes in the Third Dimension By a Modified Gas-Foaming Technique

Electrospun nanofibers have shown great potential as scaffolds for regenerative medicine because of its biomimicry. However, traditional two-dimensional electrospun nanofiber mats inhibit their applications because of the dense structure and lack of effective cell infiltration. Herein, we report a new method of expanding electrospun nanofiber mats in the third dimension using a modified gas-foaming technique. The resulting nanofiber scaffolds show layered structures with controllable gap widths and layer thicknesses on the order of microns. Expanded nanofiber scaffolds possess significantly higher porosity than traditional two-dimensional nanofiber membranes, while simultaneously maintaining nanotopographic cues. The distributions of gap widths and layer thicknesses are directly dependent on the processing time of nanofiber mats within the gas bubble forming solution. In vitro testing demonstrates robust cellular infiltration and proliferation within expanded nanofiber scaffolds as compared to limited cellular proliferation on the surface of traditional nanofiber mats. Importantly, cell alignment was observed throughout the expanded and aligned nanofiber scaffolds after incubation for 7 days. The presented method was further applied to fabricate tubular scaffolds composed of expanded nanofibers. Together, this novel class of scaffolds holds significant promise for applications in regenerative medicine and building 3D in vitro tissue models for drug screening and biological study

Comparison of battery-powered and wireless-powered pacemakers.

<p>Comparison of battery-powered and wireless-powered pacemakers.</p

Bench top and <i>in vivo</i> testing of battery powered pacemaker.

<p>(a) Current (blue) and voltage (gray) traces from the pacing catheter. (b) Frequency Response Analysis of distal and proximal pacing catheter electrodes (c) Lead II ECG recording in a mouse heart during sinus rhythm and right ventricular pacing by the battery-powered pacemaker over 5 days.</p

<i>In vivo</i> testing of wireless pacemaker.

<p>(a) Lead II ECG during normal sinus rhythm (top) and during LV apical pacing (bottom). (b) Pacing pulse width threshold of wireless device over 30 days for all mice with stable capture. Solid red line shows linear regression on mean pulse width thresholds. Dashed black lines show 95% confidence interval bounds for the regression.</p

Assembly process of wireless powered pacemaker.

<p>(a) Platinum wire is attached to the circuit board, wound together, and coiled with a 0.5 cc syringe. (b) A bead of Silastic is placed on a piece of parafilm(1). The device is placed on the bead(2), coated with an additional layer of Silastic(3), and topped with a piece of gas permeable film(4). (c) Final product. (d) Artistic rendering of external transmitter interacting with abdominally implanted receiver in mouse.</p

Layout of the wireless-powered pacemaker.

<p>(a) Circuit layout of transmitter (top) and receiver (bottom). (b) Pulsed input into transmitter from pulse generator. (c) Output from transmitter. (d) Uncapped output from receiver. (e) Capped output from receiver. (f) Receiver output decreases minimally up to 5 cm from the transmitter coil. See text for further details.</p

Parts list for wireless transmitter and receiver circuits.

<p>Parts list for wireless transmitter and receiver circuits.</p