Fast three-dimensional micropatterning of PC12 cells in rapidly crosslinked hydrogel scaffolds using ultrasonic standing waves

Abstract The ability to spatially organise the microenvironment of tissue scaffolds unlocks the potential of many scaffold-based tissue engineering applications. An example application is to aid the regeneration process of peripheral nerve injuries. Herein, we present a promising approach for three-dimensional (3D) micropatterning of nerve cells in tissue scaffolds for peripheral nerve repair. In particular, we demonstrate the 3D micropatterning of PC12 cells in a gelatin-hydroxyphenylpropionic acid (Gtn-HPA) hydrogel using ultrasound standing waves (USWs). PC12 cells were first aligned in 3D along nodal planes by the USWs in Gtn-HPA hydrogel precursor solution. The precursor was then crosslinked using horseradish peroxidase (HRP) and diluted hydrogen peroxide (H ₂ O ₂ ), thus immobilising the aligned cells within 90–120 s. This micropatterning process is cost effective and can be replicated easily without the need for complex and expensive specialised equipment. USW-aligned PC12 cells showed no adverse effect in terms of viability or ability to proliferate. To our best knowledge, this is the first report on the effect of USW alignment on neural cell differentiation. Differentiated and USW-aligned PC12 cells showed directional uniformity after 20 d, making this technique a promising alternative approach to guide the nerve regeneration process.