Piezoelectric-responsive hydrogel promotes matrix synthesis in nucleus pulposus cells of rats

Objective To investigate the property of fundamental material properties of a piezoelectic-responsive hydrogel (KNN/GelMA), including its mechanical, piezoelectric and biocompatibility characteristics, and to examine the effects of its piezoelectric response the synthetic metabolism of nucleus pulposus cells (NPCs). Methods 1)Material characterisation: KNN was uniformly dispersed in GelMA hydrogel via ultrasonication to prepare a photopolymerisable, degradable piezoelectric hydrogel. Preliminary physicochemical characterisation was conducted by measuring microstructure, piezoelectric properties and so on. 2) Cellular experiments: The piezoelectic-responsive hydrogel was co-incubated with rat primary NPCs. The proliferation capacity and biocompatibility were assessed using the CCK-8 methods and a dead/live staining kit. Gene expression related to extra cellular matrix synthesis was detected by RT-qPCR. Results The material surface exhibited a uniform pore structure, with KNN nanoparticles distributed evenly throughout the hydrogel. Piezoelectric output experiments demonstrated significant voltage and current generation under applied force(P＜0.05). The proliferation of cells in the 0.4% w/v KNN/GelMA group was significantly enhanced over time as compared with that in 0.2% w/v KNN/GelMA group, and live cells (green) were dominant(P＜0.05). RT-qPCR showed that the mRNA levels of related aggrecan(Acan) and type Ⅱ collagen (Col2) in the extra cellular matrix of chondrocytes in the TNF-α + KNN/GelMA + ultrasound(US) group was lower than those in the TNF-α + KNN/GelM group(P＜0.05). Conclusions A light-curable, degradable, piezoelectric-responsive hydrogel which exhibits a uniform porous structure has developed. It has a significant piezoelectric effect, excellent biocompatibility, and can significantly promote the cell matrix synthesis ability of nucleus pulposus cells. It is a promising material option for repairing degenerative disc injuries.